1 /*-
2 * SPDX-License-Identifier: BSD-3-Clause
3 *
4 * Copyright (c) 1989, 1993, 1995
5 * The Regents of the University of California. All rights reserved.
6 *
7 * This code is derived from software contributed to Berkeley by
8 * Poul-Henning Kamp of the FreeBSD Project.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 * notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 * notice, this list of conditions and the following disclaimer in the
17 * documentation and/or other materials provided with the distribution.
18 * 3. Neither the name of the University nor the names of its contributors
19 * may be used to endorse or promote products derived from this software
20 * without specific prior written permission.
21 *
22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
25 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
32 * SUCH DAMAGE.
33 */
34
35 #include "opt_ddb.h"
36 #include "opt_ktrace.h"
37
38 #include <sys/param.h>
39 #include <sys/systm.h>
40 #include <sys/capsicum.h>
41 #include <sys/counter.h>
42 #include <sys/filedesc.h>
43 #include <sys/fnv_hash.h>
44 #include <sys/inotify.h>
45 #include <sys/kernel.h>
46 #include <sys/ktr.h>
47 #include <sys/lock.h>
48 #include <sys/malloc.h>
49 #include <sys/fcntl.h>
50 #include <sys/jail.h>
51 #include <sys/mount.h>
52 #include <sys/namei.h>
53 #include <sys/proc.h>
54 #include <sys/seqc.h>
55 #include <sys/sdt.h>
56 #include <sys/smr.h>
57 #include <sys/smp.h>
58 #include <sys/syscallsubr.h>
59 #include <sys/sysctl.h>
60 #include <sys/sysproto.h>
61 #include <sys/vnode.h>
62 #include <ck_queue.h>
63 #ifdef KTRACE
64 #include <sys/ktrace.h>
65 #endif
66 #ifdef INVARIANTS
67 #include <machine/_inttypes.h>
68 #endif
69
70 #include <security/audit/audit.h>
71 #include <security/mac/mac_framework.h>
72
73 #ifdef DDB
74 #include <ddb/ddb.h>
75 #endif
76
77 #include <vm/uma.h>
78
79 /*
80 * High level overview of name caching in the VFS layer.
81 *
82 * Originally caching was implemented as part of UFS, later extracted to allow
83 * use by other filesystems. A decision was made to make it optional and
84 * completely detached from the rest of the kernel, which comes with limitations
85 * outlined near the end of this comment block.
86 *
87 * This fundamental choice needs to be revisited. In the meantime, the current
88 * state is described below. Significance of all notable routines is explained
89 * in comments placed above their implementation. Scattered throughout the
90 * file are TODO comments indicating shortcomings which can be fixed without
91 * reworking everything (most of the fixes will likely be reusable). Various
92 * details are omitted from this explanation to not clutter the overview, they
93 * have to be checked by reading the code and associated commentary.
94 *
95 * Keep in mind that it's individual path components which are cached, not full
96 * paths. That is, for a fully cached path "foo/bar/baz" there are 3 entries,
97 * one for each name.
98 *
99 * I. Data organization
100 *
101 * Entries are described by "struct namecache" objects and stored in a hash
102 * table. See cache_get_hash for more information.
103 *
104 * "struct vnode" contains pointers to source entries (names which can be found
105 * when traversing through said vnode), destination entries (names of that
106 * vnode (see "Limitations" for a breakdown on the subject) and a pointer to
107 * the parent vnode.
108 *
109 * The (directory vnode; name) tuple reliably determines the target entry if
110 * it exists.
111 *
112 * Since there were no small locks at the time of writing this comment (all are
113 * 32 bytes in size on LP64), the code works around the problem by introducing
114 * lock arrays to protect hash buckets and vnode lists.
115 *
116 * II. Filesystem integration
117 *
118 * Filesystems participating in name caching do the following:
119 * - set vop_lookup routine to vfs_cache_lookup
120 * - set vop_cachedlookup to a routine which can perform the lookup if the
121 * above fails
122 * - if they support lockless lookup (see below), they set vop_fplookup_vexec
123 * and vop_fplookup_symlink along with the MNTK_FPLOOKUP flag on the mount
124 * point
125 * - call cache_purge or cache_vop_* routines to eliminate stale entries as
126 * applicable
127 * - call cache_enter to add entries depending on the MAKEENTRY flag
128 *
129 * With the above in mind, there are 2 entry points when doing lookups:
130 * - ... -> namei -> cache_fplookup -- this is the default
131 * - ... -> VOP_LOOKUP -> vfs_cache_lookup -- normally only called by namei
132 * should the above fail
133 *
134 * Example code flow how an entry is added:
135 * ... -> namei -> cache_fplookup -> cache_fplookup_noentry -> VOP_LOOKUP ->
136 * vfs_cache_lookup -> VOP_CACHEDLOOKUP -> ufs_lookup_ino -> cache_enter
137 *
138 * You may notice a degree of CPU waste in this callchain.
139 *
140 * III. Performance considerations
141 *
142 * For lockless case forward lookup avoids any writes to shared areas apart
143 * from the terminal path component. In other words non-modifying lookups of
144 * different files don't suffer any scalability problems in the namecache
145 * itself.
146 *
147 * Looking up the same file is limited by VFS and goes beyond the scope of this
148 * file.
149 *
150 * At least on amd64 the single-threaded bottleneck for long paths is hashing
151 * (see cache_get_hash). There are cases where the code issues acquire fence
152 * multiple times, they can be combined on architectures which suffer from it.
153 *
154 * For locked case each encountered vnode has to be referenced and locked in
155 * order to be handed out to the caller (normally that's namei). This
156 * introduces significant hit single-threaded and serialization multi-threaded.
157 *
158 * Reverse lookup (e.g., "getcwd") fully scales provided it is fully cached --
159 * avoids any writes to shared areas to any components.
160 *
161 * Unrelated insertions are partially serialized on updating the global entry
162 * counter and possibly serialized on colliding bucket or vnode locks.
163 *
164 * IV. Observability
165 *
166 * Several statistics are collected in the vfs.cache sysctl tree.
167 *
168 * Some of the state can be checked for with explicit dtrace probes, must of it
169 * depends on implementation details.
170 *
171 * Examples:
172 *
173 * # Check what lookups failed to be handled in a lockless manner. Column 1 is
174 * # line number, column 2 is status code (see cache_fpl_status)
175 * dtrace -n 'vfs:fplookup:lookup:done { @[arg1, arg2] = count(); }'
176 *
177 * # Histogram of lengths of names added, aggregated by which programs are doing it
178 * dtrace -n 'fbt::cache_enter_time:entry { @[execname] = quantize(args[2]->cn_namelen); }'
179 *
180 * # Same as above but only those which exceed 64 characters
181 * dtrace -n 'fbt::cache_enter_time:entry /args[2]->cn_namelen > 64/ { @[execname] = quantize(args[2]->cn_namelen); }'
182 *
183 * # Who is performing lookups with spurious slashes (e.g., "foo//bar") and what
184 * # path is it
185 * dtrace -n 'fbt::cache_fplookup_skip_slashes:entry { @[execname, stringof(args[0]->cnp->cn_pnbuf)] = count(); }'
186 *
187 * V. Limitations and implementation defects
188 *
189 * - since it is possible there is no entry for an open file, tools like
190 * "procstat" may fail to resolve fd -> vnode -> path to anything
191 * - even if a filesystem adds an entry, it may get purged (e.g., due to memory
192 * shortage) in which case the above problem applies
193 * - hardlinks are not tracked, thus if a vnode is reachable in more than one
194 * way, resolving a name may return a different path than the one used to
195 * open it (even if said path is still valid)
196 * - by default entries are not added for newly created files
197 * - adding an entry may need to evict negative entry first, which happens in 2
198 * distinct places (evicting on lookup, adding in a later VOP) making it
199 * impossible to simply reuse it
200 * - there is a simple scheme to evict negative entries as the cache is approaching
201 * its capacity, but it is very unclear if doing so is a good idea to begin with
202 * - vnodes are subject to being recycled even if target inode is left in memory,
203 * which loses the name cache entries when it perhaps should not. in case of tmpfs
204 * names get duplicated -- kept by filesystem itself and namecache separately
205 * - vnode reclamation (see vnlru in kern/vfs_subr.c) defaults to skipping
206 * directories for this very reason, which arguably further reducing quality
207 * of vnode LRU. Per the above this is done to avoid breaking vnode -> path
208 * resolution (it becomes expensive for directories and impossible for the rest)
209 * This would not be a factor if namecache entries could persist without vnodes.
210 * - struct namecache has a fixed size and comes in 2 variants, often wasting
211 * space. now hard to replace with malloc due to dependence on SMR, which
212 * requires UMA zones to opt in
213 * - lack of better integration with the kernel also turns nullfs into a layered
214 * filesystem instead of something which can take advantage of caching
215 *
216 * Appendix A: where is the time lost, expanding on paragraph III
217 *
218 * While some care went into optimizing lookups, there is still plenty of
219 * performance left on the table, most notably from single-threaded standpoint.
220 * Below is a woefully incomplete list of changes which can help. Ideas are
221 * mostly sketched out, no claim is made all kinks or prerequisites are laid
222 * out. The name of the game is eliding branches altogether and hopefully some
223 * of memory accesses.
224 *
225 * Note there is performance lost all over VFS.
226 *
227 * === SMR-only lookup
228 *
229 * For commonly used ops like stat(2), when the terminal vnode *is* cached,
230 * lockless lookup could refrain from refing/locking the found vnode and
231 * instead return while within the SMR section. Then a call to, say,
232 * vop_stat_smr could do the work (or fail with EAGAIN), finally the result
233 * would be validated with seqc not changing. This would be faster
234 * single-threaded as it dodges atomics and would provide full scalability for
235 * multicore uses. This would *not* work for open(2) or other calls which need
236 * the vnode to hang around for the long haul, but would work for aforementioned
237 * stat(2) but also access(2), readlink(2), realpathat(2) and probably more.
238 *
239 * === copyinstr
240 *
241 * On all architectures it operates one byte at a time, while it could be
242 * word-sized instead thanks to the Mycroft trick.
243 *
244 * API itself is rather pessimal for path lookup, accepting arbitrary sizes and
245 * *optionally* filling in the length parameter.
246 *
247 * Instead a new routine (copyinpath?) could be introduced, demanding a buffer
248 * size which is a multiply of the word (and never zero), with the length
249 * always returned. On top of it the routine could be allowed to transform the
250 * buffer in arbitrary ways, most notably writing past the found length (not to
251 * be confused with writing past buffer size) -- this would allow word-sized
252 * movs while checking for '\0' later.
253 *
254 * === detour through namei
255 *
256 * Currently one suffers being called from namei, which then has to check if
257 * things worked out locklessly. Instead the lockless lookup could be the
258 * actual entry point which calls what is currently namei as a fallback.
259 *
260 * It could be hotpatched if lockless lookup is disabled.
261 *
262 * === avoidable branches in cache_can_fplookup
263 *
264 * The cache_fast_lookup_enabled flag check could be hotpatchable (in fact if
265 * this is off, none of fplookup code should execute, see above).
266 *
267 * Both audit and capsicum branches can be combined into one, but it requires
268 * paying off a lot of tech debt first.
269 *
270 * ni_startdir could be indicated with a flag in cn_flags, eliminating the
271 * branch.
272 *
273 * === mount stacks
274 *
275 * Crossing a mount requires checking if perhaps something is mounted on top.
276 * Instead, an additional entry could be added to struct mount with a pointer
277 * to the final mount on the stack. This would be recalculated on each
278 * mount/unmount.
279 *
280 * === root vnodes
281 *
282 * It could become part of the API contract to *always* have a rootvnode set in
283 * mnt_rootvnode. Such vnodes are annotated with VV_ROOT and vnlru would have
284 * to be modified to always skip them.
285 *
286 * === inactive on v_usecount reaching 0
287 *
288 * VOP_NEED_INACTIVE should not exist. Filesystems can indicate need for such
289 * processing with a bit in usecount and adding a hold count. Then vput fast path
290 * would become as simple as (ACHTUNG: locking ignored):
291 *
292 * ref = atomic_fetchadd_int(&vp->v_count, -1) - 1;
293 * if ((ref & MAGIC_BIT) == 0) // common case
294 * return;
295 * if (ref != 0) // the bit is set but this was not the last user
296 * return;
297 * // do inactive here
298 *
299 * Also see below.
300 *
301 * === v_holdcnt
302 *
303 * Hold count should probably get eliminated, but one can argue it is a useful
304 * feature. Even if so, handling of v_usecount could be decoupled from it --
305 * vnlru et al would consider the vnode not-freeable if has either hold or
306 * usecount on it.
307 *
308 * This would eliminate 2 atomics in the common case of securing a vnode and
309 * undoing it.
310 */
311
312 static SYSCTL_NODE(_vfs, OID_AUTO, cache, CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
313 "Name cache");
314
315 SDT_PROVIDER_DECLARE(vfs);
316 SDT_PROBE_DEFINE3(vfs, namecache, enter, done, "struct vnode *", "char *",
317 "struct vnode *");
318 SDT_PROBE_DEFINE3(vfs, namecache, enter, duplicate, "struct vnode *", "char *",
319 "struct vnode *");
320 SDT_PROBE_DEFINE2(vfs, namecache, enter_negative, done, "struct vnode *",
321 "char *");
322 SDT_PROBE_DEFINE2(vfs, namecache, fullpath_smr, hit, "struct vnode *",
323 "const char *");
324 SDT_PROBE_DEFINE4(vfs, namecache, fullpath_smr, miss, "struct vnode *",
325 "struct namecache *", "int", "int");
326 SDT_PROBE_DEFINE1(vfs, namecache, fullpath, entry, "struct vnode *");
327 SDT_PROBE_DEFINE3(vfs, namecache, fullpath, hit, "struct vnode *",
328 "char *", "struct vnode *");
329 SDT_PROBE_DEFINE1(vfs, namecache, fullpath, miss, "struct vnode *");
330 SDT_PROBE_DEFINE3(vfs, namecache, fullpath, return, "int",
331 "struct vnode *", "char *");
332 SDT_PROBE_DEFINE3(vfs, namecache, lookup, hit, "struct vnode *", "char *",
333 "struct vnode *");
334 SDT_PROBE_DEFINE2(vfs, namecache, lookup, hit__negative,
335 "struct vnode *", "char *");
336 SDT_PROBE_DEFINE2(vfs, namecache, lookup, miss, "struct vnode *",
337 "char *");
338 SDT_PROBE_DEFINE2(vfs, namecache, removecnp, hit, "struct vnode *",
339 "struct componentname *");
340 SDT_PROBE_DEFINE2(vfs, namecache, removecnp, miss, "struct vnode *",
341 "struct componentname *");
342 SDT_PROBE_DEFINE3(vfs, namecache, purge, done, "struct vnode *", "size_t", "size_t");
343 SDT_PROBE_DEFINE1(vfs, namecache, purge, batch, "int");
344 SDT_PROBE_DEFINE1(vfs, namecache, purge_negative, done, "struct vnode *");
345 SDT_PROBE_DEFINE1(vfs, namecache, purgevfs, done, "struct mount *");
346 SDT_PROBE_DEFINE3(vfs, namecache, zap, done, "struct vnode *", "char *",
347 "struct vnode *");
348 SDT_PROBE_DEFINE2(vfs, namecache, zap_negative, done, "struct vnode *",
349 "char *");
350 SDT_PROBE_DEFINE2(vfs, namecache, evict_negative, done, "struct vnode *",
351 "char *");
352 SDT_PROBE_DEFINE1(vfs, namecache, symlink, alloc__fail, "size_t");
353
354 SDT_PROBE_DEFINE3(vfs, fplookup, lookup, done, "struct nameidata *", "int",
355 "enum cache_fpl_status");
356 SDT_PROBE_DECLARE(vfs, namei, lookup, entry);
357 SDT_PROBE_DECLARE(vfs, namei, lookup, return);
358
359 static char __read_frequently cache_fast_lookup_enabled = true;
360
361 /*
362 * This structure describes the elements in the cache of recent
363 * names looked up by namei.
364 */
365 struct negstate {
366 u_char neg_flag;
367 u_char neg_hit;
368 };
369 _Static_assert(sizeof(struct negstate) <= sizeof(struct vnode *),
370 "the state must fit in a union with a pointer without growing it");
371
372 struct namecache {
373 LIST_ENTRY(namecache) nc_src; /* source vnode list */
374 TAILQ_ENTRY(namecache) nc_dst; /* destination vnode list */
375 CK_SLIST_ENTRY(namecache) nc_hash;/* hash chain */
376 struct vnode *nc_dvp; /* vnode of parent of name */
377 union {
378 struct vnode *nu_vp; /* vnode the name refers to */
379 struct negstate nu_neg;/* negative entry state */
380 } n_un;
381 u_char nc_flag; /* flag bits */
382 u_char nc_nlen; /* length of name */
383 char nc_name[]; /* segment name + nul */
384 };
385
386 /*
387 * struct namecache_ts repeats struct namecache layout up to the
388 * nc_nlen member.
389 * struct namecache_ts is used in place of struct namecache when time(s) need
390 * to be stored. The nc_dotdottime field is used when a cache entry is mapping
391 * both a non-dotdot directory name plus dotdot for the directory's
392 * parent.
393 *
394 * See below for alignment requirement.
395 */
396 struct namecache_ts {
397 struct timespec nc_time; /* timespec provided by fs */
398 struct timespec nc_dotdottime; /* dotdot timespec provided by fs */
399 int nc_ticks; /* ticks value when entry was added */
400 int nc_pad;
401 struct namecache nc_nc;
402 };
403
404 TAILQ_HEAD(cache_freebatch, namecache);
405
406 /*
407 * At least mips n32 performs 64-bit accesses to timespec as found
408 * in namecache_ts and requires them to be aligned. Since others
409 * may be in the same spot suffer a little bit and enforce the
410 * alignment for everyone. Note this is a nop for 64-bit platforms.
411 */
412 #define CACHE_ZONE_ALIGNMENT UMA_ALIGNOF(time_t)
413
414 /*
415 * TODO: the initial value of CACHE_PATH_CUTOFF was inherited from the
416 * 4.4 BSD codebase. Later on struct namecache was tweaked to become
417 * smaller and the value was bumped to retain the total size, but it
418 * was never re-evaluated for suitability. A simple test counting
419 * lengths during package building shows that the value of 45 covers
420 * about 86% of all added entries, reaching 99% at 65.
421 *
422 * Regardless of the above, use of dedicated zones instead of malloc may be
423 * inducing additional waste. This may be hard to address as said zones are
424 * tied to VFS SMR. Even if retaining them, the current split should be
425 * re-evaluated.
426 */
427 #ifdef __LP64__
428 #define CACHE_PATH_CUTOFF 45
429 #define CACHE_LARGE_PAD 6
430 #else
431 #define CACHE_PATH_CUTOFF 41
432 #define CACHE_LARGE_PAD 2
433 #endif
434
435 #define CACHE_ZONE_SMALL_SIZE (offsetof(struct namecache, nc_name) + CACHE_PATH_CUTOFF + 1)
436 #define CACHE_ZONE_SMALL_TS_SIZE (offsetof(struct namecache_ts, nc_nc) + CACHE_ZONE_SMALL_SIZE)
437 #define CACHE_ZONE_LARGE_SIZE (offsetof(struct namecache, nc_name) + NAME_MAX + 1 + CACHE_LARGE_PAD)
438 #define CACHE_ZONE_LARGE_TS_SIZE (offsetof(struct namecache_ts, nc_nc) + CACHE_ZONE_LARGE_SIZE)
439
440 _Static_assert((CACHE_ZONE_SMALL_SIZE % (CACHE_ZONE_ALIGNMENT + 1)) == 0, "bad zone size");
441 _Static_assert((CACHE_ZONE_SMALL_TS_SIZE % (CACHE_ZONE_ALIGNMENT + 1)) == 0, "bad zone size");
442 _Static_assert((CACHE_ZONE_LARGE_SIZE % (CACHE_ZONE_ALIGNMENT + 1)) == 0, "bad zone size");
443 _Static_assert((CACHE_ZONE_LARGE_TS_SIZE % (CACHE_ZONE_ALIGNMENT + 1)) == 0, "bad zone size");
444
445 #define nc_vp n_un.nu_vp
446 #define nc_neg n_un.nu_neg
447
448 /*
449 * Flags in namecache.nc_flag
450 */
451 #define NCF_WHITE 0x01
452 #define NCF_ISDOTDOT 0x02
453 #define NCF_TS 0x04
454 #define NCF_DTS 0x08
455 #define NCF_DVDROP 0x10
456 #define NCF_NEGATIVE 0x20
457 #define NCF_INVALID 0x40
458 #define NCF_WIP 0x80
459
460 /*
461 * Flags in negstate.neg_flag
462 */
463 #define NEG_HOT 0x01
464
465 static bool cache_neg_evict_cond(u_long lnumcache);
466
467 /*
468 * Mark an entry as invalid.
469 *
470 * This is called before it starts getting deconstructed.
471 */
472 static void
cache_ncp_invalidate(struct namecache * ncp)473 cache_ncp_invalidate(struct namecache *ncp)
474 {
475
476 KASSERT((ncp->nc_flag & NCF_INVALID) == 0,
477 ("%s: entry %p already invalid", __func__, ncp));
478 atomic_store_char(&ncp->nc_flag, ncp->nc_flag | NCF_INVALID);
479 atomic_thread_fence_rel();
480 }
481
482 /*
483 * Does this entry match the given directory and name?
484 */
485 static bool
cache_ncp_match(struct namecache * ncp,struct vnode * dvp,struct componentname * cnp)486 cache_ncp_match(struct namecache *ncp, struct vnode *dvp,
487 struct componentname *cnp)
488 {
489 return (ncp->nc_dvp == dvp &&
490 ncp->nc_nlen == cnp->cn_namelen &&
491 bcmp(ncp->nc_name, cnp->cn_nameptr, cnp->cn_namelen) == 0);
492 }
493
494 /*
495 * Check whether the entry can be safely used.
496 *
497 * All places which elide locks are supposed to call this after they are
498 * done with reading from an entry.
499 */
500 #define cache_ncp_canuse(ncp) ({ \
501 struct namecache *_ncp = (ncp); \
502 u_char _nc_flag; \
503 \
504 atomic_thread_fence_acq(); \
505 _nc_flag = atomic_load_char(&_ncp->nc_flag); \
506 __predict_true((_nc_flag & (NCF_INVALID | NCF_WIP)) == 0); \
507 })
508
509 /*
510 * Like the above but also checks NCF_WHITE.
511 */
512 #define cache_fpl_neg_ncp_canuse(ncp) ({ \
513 struct namecache *_ncp = (ncp); \
514 u_char _nc_flag; \
515 \
516 atomic_thread_fence_acq(); \
517 _nc_flag = atomic_load_char(&_ncp->nc_flag); \
518 __predict_true((_nc_flag & (NCF_INVALID | NCF_WIP | NCF_WHITE)) == 0); \
519 })
520
521 VFS_SMR_DECLARE;
522
523 static SYSCTL_NODE(_vfs_cache, OID_AUTO, param, CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
524 "Name cache parameters");
525
526 static u_int __read_mostly ncsize; /* the size as computed on creation or resizing */
527 SYSCTL_UINT(_vfs_cache_param, OID_AUTO, size, CTLFLAG_RD, &ncsize, 0,
528 "Total namecache capacity");
529
530 u_int ncsizefactor = 2;
531 SYSCTL_UINT(_vfs_cache_param, OID_AUTO, sizefactor, CTLFLAG_RW, &ncsizefactor, 0,
532 "Size factor for namecache");
533
534 static u_long __read_mostly ncnegfactor = 5; /* ratio of negative entries */
535 SYSCTL_ULONG(_vfs_cache_param, OID_AUTO, negfactor, CTLFLAG_RW, &ncnegfactor, 0,
536 "Ratio of negative namecache entries");
537
538 /*
539 * Negative entry % of namecache capacity above which automatic eviction is allowed.
540 *
541 * Check cache_neg_evict_cond for details.
542 */
543 static u_int ncnegminpct = 3;
544
545 static u_int __read_mostly neg_min; /* the above recomputed against ncsize */
546 SYSCTL_UINT(_vfs_cache_param, OID_AUTO, negmin, CTLFLAG_RD, &neg_min, 0,
547 "Negative entry count above which automatic eviction is allowed");
548
549 /*
550 * Structures associated with name caching.
551 */
552 #define NCHHASH(hash) \
553 (&nchashtbl[(hash) & nchash])
554 static __read_mostly CK_SLIST_HEAD(nchashhead, namecache) *nchashtbl;/* Hash Table */
555 static u_long __read_mostly nchash; /* size of hash table */
556 SYSCTL_ULONG(_debug, OID_AUTO, nchash, CTLFLAG_RD, &nchash, 0,
557 "Size of namecache hash table");
558 static u_long __exclusive_cache_line numneg; /* number of negative entries allocated */
559 static u_long __exclusive_cache_line numcache;/* number of cache entries allocated */
560
561 struct nchstats nchstats; /* cache effectiveness statistics */
562
563 static u_int __exclusive_cache_line neg_cycle;
564
565 #define ncneghash 3
566 #define numneglists (ncneghash + 1)
567
568 struct neglist {
569 struct mtx nl_evict_lock;
570 struct mtx nl_lock __aligned(CACHE_LINE_SIZE);
571 TAILQ_HEAD(, namecache) nl_list;
572 TAILQ_HEAD(, namecache) nl_hotlist;
573 u_long nl_hotnum;
574 } __aligned(CACHE_LINE_SIZE);
575
576 static struct neglist neglists[numneglists];
577
578 static inline struct neglist *
NCP2NEGLIST(struct namecache * ncp)579 NCP2NEGLIST(struct namecache *ncp)
580 {
581
582 return (&neglists[(((uintptr_t)(ncp) >> 8) & ncneghash)]);
583 }
584
585 static inline struct negstate *
NCP2NEGSTATE(struct namecache * ncp)586 NCP2NEGSTATE(struct namecache *ncp)
587 {
588
589 MPASS(atomic_load_char(&ncp->nc_flag) & NCF_NEGATIVE);
590 return (&ncp->nc_neg);
591 }
592
593 #define numbucketlocks (ncbuckethash + 1)
594 static u_int __read_mostly ncbuckethash;
595 static struct mtx_padalign __read_mostly *bucketlocks;
596 #define HASH2BUCKETLOCK(hash) \
597 ((struct mtx *)(&bucketlocks[((hash) & ncbuckethash)]))
598
599 #define numvnodelocks (ncvnodehash + 1)
600 static u_int __read_mostly ncvnodehash;
601 static struct mtx __read_mostly *vnodelocks;
602 static inline struct mtx *
VP2VNODELOCK(struct vnode * vp)603 VP2VNODELOCK(struct vnode *vp)
604 {
605
606 return (&vnodelocks[(((uintptr_t)(vp) >> 8) & ncvnodehash)]);
607 }
608
609 /*
610 * Search the hash table for a namecache entry. Either the corresponding bucket
611 * must be locked, or the caller must be in an SMR read section.
612 */
613 static struct namecache *
cache_ncp_find(struct vnode * dvp,struct componentname * cnp,uint32_t hash)614 cache_ncp_find(struct vnode *dvp, struct componentname *cnp, uint32_t hash)
615 {
616 struct namecache *ncp;
617
618 KASSERT(mtx_owned(HASH2BUCKETLOCK(hash)) || VFS_SMR_ENTERED(),
619 ("%s: hash %u not locked", __func__, hash));
620 CK_SLIST_FOREACH(ncp, NCHHASH(hash), nc_hash) {
621 if (cache_ncp_match(ncp, dvp, cnp))
622 break;
623 }
624 return (ncp);
625 }
626
627 static void
cache_out_ts(struct namecache * ncp,struct timespec * tsp,int * ticksp)628 cache_out_ts(struct namecache *ncp, struct timespec *tsp, int *ticksp)
629 {
630 struct namecache_ts *ncp_ts;
631
632 KASSERT((ncp->nc_flag & NCF_TS) != 0 ||
633 (tsp == NULL && ticksp == NULL),
634 ("No NCF_TS"));
635
636 if (tsp == NULL)
637 return;
638
639 ncp_ts = __containerof(ncp, struct namecache_ts, nc_nc);
640 *tsp = ncp_ts->nc_time;
641 *ticksp = ncp_ts->nc_ticks;
642 }
643
644 #ifdef DEBUG_CACHE
645 static int __read_mostly doingcache = 1; /* 1 => enable the cache */
646 SYSCTL_INT(_debug, OID_AUTO, vfscache, CTLFLAG_RW, &doingcache, 0,
647 "VFS namecache enabled");
648 #endif
649
650 /* Export size information to userland */
651 SYSCTL_SIZEOF_STRUCT(namecache);
652
653 /*
654 * The new name cache statistics
655 */
656 static SYSCTL_NODE(_vfs_cache, OID_AUTO, stats, CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
657 "Name cache statistics");
658
659 #define STATNODE_ULONG(name, varname, descr) \
660 SYSCTL_ULONG(_vfs_cache_stats, OID_AUTO, name, CTLFLAG_RD, &varname, 0, descr);
661 #define STATNODE_COUNTER(name, varname, descr) \
662 static COUNTER_U64_DEFINE_EARLY(varname); \
663 SYSCTL_COUNTER_U64(_vfs_cache_stats, OID_AUTO, name, CTLFLAG_RD, &varname, \
664 descr);
665 STATNODE_ULONG(neg, numneg, "Number of negative cache entries");
666 STATNODE_ULONG(count, numcache, "Number of cache entries");
667 STATNODE_COUNTER(heldvnodes, numcachehv, "Number of namecache entries with vnodes held");
668 STATNODE_COUNTER(drops, numdrops, "Number of dropped entries due to reaching the limit");
669 STATNODE_COUNTER(miss, nummiss, "Number of cache misses");
670 STATNODE_COUNTER(misszap, nummisszap, "Number of cache misses we do not want to cache");
671 STATNODE_COUNTER(poszaps, numposzaps,
672 "Number of cache hits (positive) we do not want to cache");
673 STATNODE_COUNTER(poshits, numposhits, "Number of cache hits (positive)");
674 STATNODE_COUNTER(negzaps, numnegzaps,
675 "Number of cache hits (negative) we do not want to cache");
676 STATNODE_COUNTER(neghits, numneghits, "Number of cache hits (negative)");
677 /* These count for vn_getcwd(), too. */
678 STATNODE_COUNTER(fullpathcalls, numfullpathcalls, "Number of fullpath search calls");
679 STATNODE_COUNTER(fullpathfail2, numfullpathfail2,
680 "Number of fullpath search errors (VOP_VPTOCNP failures)");
681 STATNODE_COUNTER(fullpathfail4, numfullpathfail4, "Number of fullpath search errors (ENOMEM)");
682 STATNODE_COUNTER(fullpathfound, numfullpathfound, "Number of successful fullpath calls");
683 STATNODE_COUNTER(symlinktoobig, symlinktoobig, "Number of times symlink did not fit the cache");
684
685 /*
686 * Debug or developer statistics.
687 */
688 static SYSCTL_NODE(_vfs_cache, OID_AUTO, debug, CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
689 "Name cache debugging");
690 #define DEBUGNODE_ULONG(name, varname, descr) \
691 SYSCTL_ULONG(_vfs_cache_debug, OID_AUTO, name, CTLFLAG_RD, &varname, 0, descr);
692 static u_long zap_bucket_relock_success;
693 DEBUGNODE_ULONG(zap_bucket_relock_success, zap_bucket_relock_success,
694 "Number of successful removals after relocking");
695 static u_long zap_bucket_fail;
696 DEBUGNODE_ULONG(zap_bucket_fail, zap_bucket_fail, "");
697 static u_long zap_bucket_fail2;
698 DEBUGNODE_ULONG(zap_bucket_fail2, zap_bucket_fail2, "");
699 static u_long cache_lock_vnodes_cel_3_failures;
700 DEBUGNODE_ULONG(vnodes_cel_3_failures, cache_lock_vnodes_cel_3_failures,
701 "Number of times 3-way vnode locking failed");
702
703 static void cache_zap_locked(struct namecache *ncp);
704 static int vn_fullpath_any_smr(struct vnode *vp, struct vnode *rdir, char *buf,
705 char **retbuf, size_t *buflen, size_t addend);
706 static int vn_fullpath_any(struct vnode *vp, struct vnode *rdir, char *buf,
707 char **retbuf, size_t *buflen);
708 static int vn_fullpath_dir(struct vnode *vp, struct vnode *rdir, char *buf,
709 char **retbuf, size_t *len, size_t addend);
710
711 static MALLOC_DEFINE(M_VFSCACHE, "vfscache", "VFS name cache entries");
712
713 static inline void
cache_assert_vlp_locked(struct mtx * vlp)714 cache_assert_vlp_locked(struct mtx *vlp)
715 {
716
717 if (vlp != NULL)
718 mtx_assert(vlp, MA_OWNED);
719 }
720
721 static inline void
cache_assert_vnode_locked(struct vnode * vp)722 cache_assert_vnode_locked(struct vnode *vp)
723 {
724 struct mtx *vlp;
725
726 vlp = VP2VNODELOCK(vp);
727 cache_assert_vlp_locked(vlp);
728 }
729
730 /*
731 * Directory vnodes with entries are held for two reasons:
732 * 1. make them less of a target for reclamation in vnlru
733 * 2. suffer smaller performance penalty in locked lookup as requeieing is avoided
734 *
735 * It will be feasible to stop doing it altogether if all filesystems start
736 * supporting lockless lookup.
737 */
738 static void
cache_hold_vnode(struct vnode * vp)739 cache_hold_vnode(struct vnode *vp)
740 {
741
742 cache_assert_vnode_locked(vp);
743 VNPASS(LIST_EMPTY(&vp->v_cache_src), vp);
744 vhold(vp);
745 counter_u64_add(numcachehv, 1);
746 }
747
748 static void
cache_drop_vnode(struct vnode * vp)749 cache_drop_vnode(struct vnode *vp)
750 {
751
752 /*
753 * Called after all locks are dropped, meaning we can't assert
754 * on the state of v_cache_src.
755 */
756 vdrop(vp);
757 counter_u64_add(numcachehv, -1);
758 }
759
760 /*
761 * UMA zones.
762 */
763 static uma_zone_t __read_mostly cache_zone_small;
764 static uma_zone_t __read_mostly cache_zone_small_ts;
765 static uma_zone_t __read_mostly cache_zone_large;
766 static uma_zone_t __read_mostly cache_zone_large_ts;
767
768 char *
cache_symlink_alloc(size_t size,int flags)769 cache_symlink_alloc(size_t size, int flags)
770 {
771
772 if (size < CACHE_ZONE_SMALL_SIZE) {
773 return (uma_zalloc_smr(cache_zone_small, flags));
774 }
775 if (size < CACHE_ZONE_LARGE_SIZE) {
776 return (uma_zalloc_smr(cache_zone_large, flags));
777 }
778 counter_u64_add(symlinktoobig, 1);
779 SDT_PROBE1(vfs, namecache, symlink, alloc__fail, size);
780 return (NULL);
781 }
782
783 void
cache_symlink_free(char * string,size_t size)784 cache_symlink_free(char *string, size_t size)
785 {
786
787 MPASS(string != NULL);
788 KASSERT(size < CACHE_ZONE_LARGE_SIZE,
789 ("%s: size %zu too big", __func__, size));
790
791 if (size < CACHE_ZONE_SMALL_SIZE) {
792 uma_zfree_smr(cache_zone_small, string);
793 return;
794 }
795 if (size < CACHE_ZONE_LARGE_SIZE) {
796 uma_zfree_smr(cache_zone_large, string);
797 return;
798 }
799 __assert_unreachable();
800 }
801
802 static struct namecache *
cache_alloc_uma(int len,bool ts)803 cache_alloc_uma(int len, bool ts)
804 {
805 struct namecache_ts *ncp_ts;
806 struct namecache *ncp;
807
808 if (__predict_false(ts)) {
809 if (len <= CACHE_PATH_CUTOFF)
810 ncp_ts = uma_zalloc_smr(cache_zone_small_ts, M_WAITOK);
811 else
812 ncp_ts = uma_zalloc_smr(cache_zone_large_ts, M_WAITOK);
813 ncp = &ncp_ts->nc_nc;
814 } else {
815 if (len <= CACHE_PATH_CUTOFF)
816 ncp = uma_zalloc_smr(cache_zone_small, M_WAITOK);
817 else
818 ncp = uma_zalloc_smr(cache_zone_large, M_WAITOK);
819 }
820 return (ncp);
821 }
822
823 static void
cache_free_uma(struct namecache * ncp)824 cache_free_uma(struct namecache *ncp)
825 {
826 struct namecache_ts *ncp_ts;
827
828 if (__predict_false(ncp->nc_flag & NCF_TS)) {
829 ncp_ts = __containerof(ncp, struct namecache_ts, nc_nc);
830 if (ncp->nc_nlen <= CACHE_PATH_CUTOFF)
831 uma_zfree_smr(cache_zone_small_ts, ncp_ts);
832 else
833 uma_zfree_smr(cache_zone_large_ts, ncp_ts);
834 } else {
835 if (ncp->nc_nlen <= CACHE_PATH_CUTOFF)
836 uma_zfree_smr(cache_zone_small, ncp);
837 else
838 uma_zfree_smr(cache_zone_large, ncp);
839 }
840 }
841
842 static struct namecache *
cache_alloc(int len,bool ts)843 cache_alloc(int len, bool ts)
844 {
845 u_long lnumcache;
846
847 /*
848 * Avoid blowout in namecache entries.
849 *
850 * Bugs:
851 * 1. filesystems may end up trying to add an already existing entry
852 * (for example this can happen after a cache miss during concurrent
853 * lookup), in which case we will call cache_neg_evict despite not
854 * adding anything.
855 * 2. the routine may fail to free anything and no provisions are made
856 * to make it try harder (see the inside for failure modes)
857 * 3. it only ever looks at negative entries.
858 */
859 lnumcache = atomic_fetchadd_long(&numcache, 1) + 1;
860 if (cache_neg_evict_cond(lnumcache)) {
861 lnumcache = atomic_load_long(&numcache);
862 }
863 if (__predict_false(lnumcache >= ncsize)) {
864 atomic_subtract_long(&numcache, 1);
865 counter_u64_add(numdrops, 1);
866 return (NULL);
867 }
868 return (cache_alloc_uma(len, ts));
869 }
870
871 static void
cache_free(struct namecache * ncp)872 cache_free(struct namecache *ncp)
873 {
874
875 MPASS(ncp != NULL);
876 if ((ncp->nc_flag & NCF_DVDROP) != 0) {
877 cache_drop_vnode(ncp->nc_dvp);
878 }
879 cache_free_uma(ncp);
880 atomic_subtract_long(&numcache, 1);
881 }
882
883 static void
cache_free_batch(struct cache_freebatch * batch)884 cache_free_batch(struct cache_freebatch *batch)
885 {
886 struct namecache *ncp, *nnp;
887 int i;
888
889 i = 0;
890 if (TAILQ_EMPTY(batch))
891 goto out;
892 TAILQ_FOREACH_SAFE(ncp, batch, nc_dst, nnp) {
893 if ((ncp->nc_flag & NCF_DVDROP) != 0) {
894 cache_drop_vnode(ncp->nc_dvp);
895 }
896 cache_free_uma(ncp);
897 i++;
898 }
899 atomic_subtract_long(&numcache, i);
900 out:
901 SDT_PROBE1(vfs, namecache, purge, batch, i);
902 }
903
904 /*
905 * Hashing.
906 *
907 * The code was made to use FNV in 2001 and this choice needs to be revisited.
908 *
909 * Short summary of the difficulty:
910 * The longest name which can be inserted is NAME_MAX characters in length (or
911 * 255 at the time of writing this comment), while majority of names used in
912 * practice are significantly shorter (mostly below 10). More importantly
913 * majority of lookups performed find names are even shorter than that.
914 *
915 * This poses a problem where hashes which do better than FNV past word size
916 * (or so) tend to come with additional overhead when finalizing the result,
917 * making them noticeably slower for the most commonly used range.
918 *
919 * Consider a path like: /usr/obj/usr/src/sys/amd64/GENERIC/vnode_if.c
920 *
921 * When looking it up the most time consuming part by a large margin (at least
922 * on amd64) is hashing. Replacing FNV with something which pessimizes short
923 * input would make the slowest part stand out even more.
924 */
925
926 /*
927 * TODO: With the value stored we can do better than computing the hash based
928 * on the address.
929 */
930 static void
cache_prehash(struct vnode * vp)931 cache_prehash(struct vnode *vp)
932 {
933
934 vp->v_nchash = fnv_32_buf(&vp, sizeof(vp), FNV1_32_INIT);
935 }
936
937 static uint32_t
cache_get_hash(char * name,u_char len,struct vnode * dvp)938 cache_get_hash(char *name, u_char len, struct vnode *dvp)
939 {
940
941 return (fnv_32_buf(name, len, dvp->v_nchash));
942 }
943
944 static uint32_t
cache_get_hash_iter_start(struct vnode * dvp)945 cache_get_hash_iter_start(struct vnode *dvp)
946 {
947
948 return (dvp->v_nchash);
949 }
950
951 static uint32_t
cache_get_hash_iter(char c,uint32_t hash)952 cache_get_hash_iter(char c, uint32_t hash)
953 {
954
955 return (fnv_32_buf(&c, 1, hash));
956 }
957
958 static uint32_t
cache_get_hash_iter_finish(uint32_t hash)959 cache_get_hash_iter_finish(uint32_t hash)
960 {
961
962 return (hash);
963 }
964
965 static inline struct nchashhead *
NCP2BUCKET(struct namecache * ncp)966 NCP2BUCKET(struct namecache *ncp)
967 {
968 uint32_t hash;
969
970 hash = cache_get_hash(ncp->nc_name, ncp->nc_nlen, ncp->nc_dvp);
971 return (NCHHASH(hash));
972 }
973
974 static inline struct mtx *
NCP2BUCKETLOCK(struct namecache * ncp)975 NCP2BUCKETLOCK(struct namecache *ncp)
976 {
977 uint32_t hash;
978
979 hash = cache_get_hash(ncp->nc_name, ncp->nc_nlen, ncp->nc_dvp);
980 return (HASH2BUCKETLOCK(hash));
981 }
982
983 #ifdef INVARIANTS
984 static void
cache_assert_bucket_locked(struct namecache * ncp)985 cache_assert_bucket_locked(struct namecache *ncp)
986 {
987 struct mtx *blp;
988
989 blp = NCP2BUCKETLOCK(ncp);
990 mtx_assert(blp, MA_OWNED);
991 }
992
993 static void
cache_assert_bucket_unlocked(struct namecache * ncp)994 cache_assert_bucket_unlocked(struct namecache *ncp)
995 {
996 struct mtx *blp;
997
998 blp = NCP2BUCKETLOCK(ncp);
999 mtx_assert(blp, MA_NOTOWNED);
1000 }
1001 #else
1002 #define cache_assert_bucket_locked(x) do { } while (0)
1003 #define cache_assert_bucket_unlocked(x) do { } while (0)
1004 #endif
1005
1006 #define cache_sort_vnodes(x, y) _cache_sort_vnodes((void **)(x), (void **)(y))
1007 static void
_cache_sort_vnodes(void ** p1,void ** p2)1008 _cache_sort_vnodes(void **p1, void **p2)
1009 {
1010 void *tmp;
1011
1012 MPASS(*p1 != NULL || *p2 != NULL);
1013
1014 if (*p1 > *p2) {
1015 tmp = *p2;
1016 *p2 = *p1;
1017 *p1 = tmp;
1018 }
1019 }
1020
1021 static void
cache_lock_all_buckets(void)1022 cache_lock_all_buckets(void)
1023 {
1024 u_int i;
1025
1026 for (i = 0; i < numbucketlocks; i++)
1027 mtx_lock(&bucketlocks[i]);
1028 }
1029
1030 static void
cache_unlock_all_buckets(void)1031 cache_unlock_all_buckets(void)
1032 {
1033 u_int i;
1034
1035 for (i = 0; i < numbucketlocks; i++)
1036 mtx_unlock(&bucketlocks[i]);
1037 }
1038
1039 static void
cache_lock_all_vnodes(void)1040 cache_lock_all_vnodes(void)
1041 {
1042 u_int i;
1043
1044 for (i = 0; i < numvnodelocks; i++)
1045 mtx_lock(&vnodelocks[i]);
1046 }
1047
1048 static void
cache_unlock_all_vnodes(void)1049 cache_unlock_all_vnodes(void)
1050 {
1051 u_int i;
1052
1053 for (i = 0; i < numvnodelocks; i++)
1054 mtx_unlock(&vnodelocks[i]);
1055 }
1056
1057 static int
cache_trylock_vnodes(struct mtx * vlp1,struct mtx * vlp2)1058 cache_trylock_vnodes(struct mtx *vlp1, struct mtx *vlp2)
1059 {
1060
1061 cache_sort_vnodes(&vlp1, &vlp2);
1062
1063 if (vlp1 != NULL) {
1064 if (!mtx_trylock(vlp1))
1065 return (EAGAIN);
1066 }
1067 if (!mtx_trylock(vlp2)) {
1068 if (vlp1 != NULL)
1069 mtx_unlock(vlp1);
1070 return (EAGAIN);
1071 }
1072
1073 return (0);
1074 }
1075
1076 static void
cache_lock_vnodes(struct mtx * vlp1,struct mtx * vlp2)1077 cache_lock_vnodes(struct mtx *vlp1, struct mtx *vlp2)
1078 {
1079
1080 MPASS(vlp1 != NULL || vlp2 != NULL);
1081 MPASS(vlp1 <= vlp2);
1082
1083 if (vlp1 != NULL)
1084 mtx_lock(vlp1);
1085 if (vlp2 != NULL)
1086 mtx_lock(vlp2);
1087 }
1088
1089 static void
cache_unlock_vnodes(struct mtx * vlp1,struct mtx * vlp2)1090 cache_unlock_vnodes(struct mtx *vlp1, struct mtx *vlp2)
1091 {
1092
1093 MPASS(vlp1 != NULL || vlp2 != NULL);
1094
1095 if (vlp1 != NULL)
1096 mtx_unlock(vlp1);
1097 if (vlp2 != NULL)
1098 mtx_unlock(vlp2);
1099 }
1100
1101 static int
sysctl_nchstats(SYSCTL_HANDLER_ARGS)1102 sysctl_nchstats(SYSCTL_HANDLER_ARGS)
1103 {
1104 struct nchstats snap;
1105
1106 if (req->oldptr == NULL)
1107 return (SYSCTL_OUT(req, 0, sizeof(snap)));
1108
1109 snap = nchstats;
1110 snap.ncs_goodhits = counter_u64_fetch(numposhits);
1111 snap.ncs_neghits = counter_u64_fetch(numneghits);
1112 snap.ncs_badhits = counter_u64_fetch(numposzaps) +
1113 counter_u64_fetch(numnegzaps);
1114 snap.ncs_miss = counter_u64_fetch(nummisszap) +
1115 counter_u64_fetch(nummiss);
1116
1117 return (SYSCTL_OUT(req, &snap, sizeof(snap)));
1118 }
1119 SYSCTL_PROC(_vfs_cache, OID_AUTO, nchstats, CTLTYPE_OPAQUE | CTLFLAG_RD |
1120 CTLFLAG_MPSAFE, 0, 0, sysctl_nchstats, "LU",
1121 "VFS cache effectiveness statistics");
1122
1123 static int
sysctl_hitpct(SYSCTL_HANDLER_ARGS)1124 sysctl_hitpct(SYSCTL_HANDLER_ARGS)
1125 {
1126 long poshits, neghits, miss, total;
1127 long pct;
1128
1129 poshits = counter_u64_fetch(numposhits);
1130 neghits = counter_u64_fetch(numneghits);
1131 miss = counter_u64_fetch(nummiss);
1132 total = poshits + neghits + miss;
1133
1134 pct = 0;
1135 if (total != 0)
1136 pct = ((poshits + neghits) * 100) / total;
1137 return (sysctl_handle_int(oidp, 0, pct, req));
1138 }
1139 SYSCTL_PROC(_vfs_cache_stats, OID_AUTO, hitpct,
1140 CTLTYPE_INT | CTLFLAG_MPSAFE | CTLFLAG_RD, NULL, 0, sysctl_hitpct,
1141 "I", "Percentage of hits");
1142
1143 static void
cache_recalc_neg_min(void)1144 cache_recalc_neg_min(void)
1145 {
1146
1147 neg_min = (ncsize * ncnegminpct) / 100;
1148 }
1149
1150 static int
sysctl_negminpct(SYSCTL_HANDLER_ARGS)1151 sysctl_negminpct(SYSCTL_HANDLER_ARGS)
1152 {
1153 u_int val;
1154 int error;
1155
1156 val = ncnegminpct;
1157 error = sysctl_handle_int(oidp, &val, 0, req);
1158 if (error != 0 || req->newptr == NULL)
1159 return (error);
1160
1161 if (val == ncnegminpct)
1162 return (0);
1163 if (val < 0 || val > 99)
1164 return (EINVAL);
1165 ncnegminpct = val;
1166 cache_recalc_neg_min();
1167 return (0);
1168 }
1169
1170 SYSCTL_PROC(_vfs_cache_param, OID_AUTO, negminpct,
1171 CTLTYPE_INT | CTLFLAG_MPSAFE | CTLFLAG_RW, NULL, 0, sysctl_negminpct,
1172 "I", "Negative entry \% of namecache capacity above which automatic eviction is allowed");
1173
1174 #ifdef DEBUG_CACHE
1175 /*
1176 * Grab an atomic snapshot of the name cache hash chain lengths
1177 */
1178 static SYSCTL_NODE(_debug, OID_AUTO, hashstat,
1179 CTLFLAG_RW | CTLFLAG_MPSAFE, NULL,
1180 "hash table stats");
1181
1182 static int
sysctl_debug_hashstat_rawnchash(SYSCTL_HANDLER_ARGS)1183 sysctl_debug_hashstat_rawnchash(SYSCTL_HANDLER_ARGS)
1184 {
1185 struct nchashhead *ncpp;
1186 struct namecache *ncp;
1187 int i, error, n_nchash, *cntbuf;
1188
1189 retry:
1190 n_nchash = nchash + 1; /* nchash is max index, not count */
1191 if (req->oldptr == NULL)
1192 return SYSCTL_OUT(req, 0, n_nchash * sizeof(int));
1193 cntbuf = malloc(n_nchash * sizeof(int), M_TEMP, M_ZERO | M_WAITOK);
1194 cache_lock_all_buckets();
1195 if (n_nchash != nchash + 1) {
1196 cache_unlock_all_buckets();
1197 free(cntbuf, M_TEMP);
1198 goto retry;
1199 }
1200 /* Scan hash tables counting entries */
1201 for (ncpp = nchashtbl, i = 0; i < n_nchash; ncpp++, i++)
1202 CK_SLIST_FOREACH(ncp, ncpp, nc_hash)
1203 cntbuf[i]++;
1204 cache_unlock_all_buckets();
1205 for (error = 0, i = 0; i < n_nchash; i++)
1206 if ((error = SYSCTL_OUT(req, &cntbuf[i], sizeof(int))) != 0)
1207 break;
1208 free(cntbuf, M_TEMP);
1209 return (error);
1210 }
1211 SYSCTL_PROC(_debug_hashstat, OID_AUTO, rawnchash, CTLTYPE_INT|CTLFLAG_RD|
1212 CTLFLAG_MPSAFE, 0, 0, sysctl_debug_hashstat_rawnchash, "S,int",
1213 "nchash chain lengths");
1214
1215 static int
sysctl_debug_hashstat_nchash(SYSCTL_HANDLER_ARGS)1216 sysctl_debug_hashstat_nchash(SYSCTL_HANDLER_ARGS)
1217 {
1218 int error;
1219 struct nchashhead *ncpp;
1220 struct namecache *ncp;
1221 int n_nchash;
1222 int count, maxlength, used, pct;
1223
1224 if (!req->oldptr)
1225 return SYSCTL_OUT(req, 0, 4 * sizeof(int));
1226
1227 cache_lock_all_buckets();
1228 n_nchash = nchash + 1; /* nchash is max index, not count */
1229 used = 0;
1230 maxlength = 0;
1231
1232 /* Scan hash tables for applicable entries */
1233 for (ncpp = nchashtbl; n_nchash > 0; n_nchash--, ncpp++) {
1234 count = 0;
1235 CK_SLIST_FOREACH(ncp, ncpp, nc_hash) {
1236 count++;
1237 }
1238 if (count)
1239 used++;
1240 if (maxlength < count)
1241 maxlength = count;
1242 }
1243 n_nchash = nchash + 1;
1244 cache_unlock_all_buckets();
1245 pct = (used * 100) / (n_nchash / 100);
1246 error = SYSCTL_OUT(req, &n_nchash, sizeof(n_nchash));
1247 if (error)
1248 return (error);
1249 error = SYSCTL_OUT(req, &used, sizeof(used));
1250 if (error)
1251 return (error);
1252 error = SYSCTL_OUT(req, &maxlength, sizeof(maxlength));
1253 if (error)
1254 return (error);
1255 error = SYSCTL_OUT(req, &pct, sizeof(pct));
1256 if (error)
1257 return (error);
1258 return (0);
1259 }
1260 SYSCTL_PROC(_debug_hashstat, OID_AUTO, nchash, CTLTYPE_INT|CTLFLAG_RD|
1261 CTLFLAG_MPSAFE, 0, 0, sysctl_debug_hashstat_nchash, "I",
1262 "nchash statistics (number of total/used buckets, maximum chain length, usage percentage)");
1263 #endif
1264
1265 /*
1266 * Negative entries management
1267 *
1268 * Various workloads create plenty of negative entries and barely use them
1269 * afterwards. Moreover malicious users can keep performing bogus lookups
1270 * adding even more entries. For example "make tinderbox" as of writing this
1271 * comment ends up with 2.6M namecache entries in total, 1.2M of which are
1272 * negative.
1273 *
1274 * As such, a rather aggressive eviction method is needed. The currently
1275 * employed method is a placeholder.
1276 *
1277 * Entries are split over numneglists separate lists, each of which is further
1278 * split into hot and cold entries. Entries get promoted after getting a hit.
1279 * Eviction happens on addition of new entry.
1280 */
1281 static SYSCTL_NODE(_vfs_cache, OID_AUTO, neg, CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
1282 "Name cache negative entry statistics");
1283
1284 SYSCTL_ULONG(_vfs_cache_neg, OID_AUTO, count, CTLFLAG_RD, &numneg, 0,
1285 "Number of negative cache entries");
1286
1287 static COUNTER_U64_DEFINE_EARLY(neg_created);
1288 SYSCTL_COUNTER_U64(_vfs_cache_neg, OID_AUTO, created, CTLFLAG_RD, &neg_created,
1289 "Number of created negative entries");
1290
1291 static COUNTER_U64_DEFINE_EARLY(neg_evicted);
1292 SYSCTL_COUNTER_U64(_vfs_cache_neg, OID_AUTO, evicted, CTLFLAG_RD, &neg_evicted,
1293 "Number of evicted negative entries");
1294
1295 static COUNTER_U64_DEFINE_EARLY(neg_evict_skipped_empty);
1296 SYSCTL_COUNTER_U64(_vfs_cache_neg, OID_AUTO, evict_skipped_empty, CTLFLAG_RD,
1297 &neg_evict_skipped_empty,
1298 "Number of times evicting failed due to lack of entries");
1299
1300 static COUNTER_U64_DEFINE_EARLY(neg_evict_skipped_missed);
1301 SYSCTL_COUNTER_U64(_vfs_cache_neg, OID_AUTO, evict_skipped_missed, CTLFLAG_RD,
1302 &neg_evict_skipped_missed,
1303 "Number of times evicting failed due to target entry disappearing");
1304
1305 static COUNTER_U64_DEFINE_EARLY(neg_evict_skipped_contended);
1306 SYSCTL_COUNTER_U64(_vfs_cache_neg, OID_AUTO, evict_skipped_contended, CTLFLAG_RD,
1307 &neg_evict_skipped_contended,
1308 "Number of times evicting failed due to contention");
1309
1310 SYSCTL_COUNTER_U64(_vfs_cache_neg, OID_AUTO, hits, CTLFLAG_RD, &numneghits,
1311 "Number of cache hits (negative)");
1312
1313 static int
sysctl_neg_hot(SYSCTL_HANDLER_ARGS)1314 sysctl_neg_hot(SYSCTL_HANDLER_ARGS)
1315 {
1316 int i, out;
1317
1318 out = 0;
1319 for (i = 0; i < numneglists; i++)
1320 out += neglists[i].nl_hotnum;
1321
1322 return (SYSCTL_OUT(req, &out, sizeof(out)));
1323 }
1324 SYSCTL_PROC(_vfs_cache_neg, OID_AUTO, hot, CTLTYPE_INT | CTLFLAG_RD |
1325 CTLFLAG_MPSAFE, 0, 0, sysctl_neg_hot, "I",
1326 "Number of hot negative entries");
1327
1328 static void
cache_neg_init(struct namecache * ncp)1329 cache_neg_init(struct namecache *ncp)
1330 {
1331 struct negstate *ns;
1332
1333 ncp->nc_flag |= NCF_NEGATIVE;
1334 ns = NCP2NEGSTATE(ncp);
1335 ns->neg_flag = 0;
1336 ns->neg_hit = 0;
1337 counter_u64_add(neg_created, 1);
1338 }
1339
1340 #define CACHE_NEG_PROMOTION_THRESH 2
1341
1342 static bool
cache_neg_hit_prep(struct namecache * ncp)1343 cache_neg_hit_prep(struct namecache *ncp)
1344 {
1345 struct negstate *ns;
1346 u_char n;
1347
1348 ns = NCP2NEGSTATE(ncp);
1349 n = atomic_load_char(&ns->neg_hit);
1350 for (;;) {
1351 if (n >= CACHE_NEG_PROMOTION_THRESH)
1352 return (false);
1353 if (atomic_fcmpset_8(&ns->neg_hit, &n, n + 1))
1354 break;
1355 }
1356 return (n + 1 == CACHE_NEG_PROMOTION_THRESH);
1357 }
1358
1359 /*
1360 * Nothing to do here but it is provided for completeness as some
1361 * cache_neg_hit_prep callers may end up returning without even
1362 * trying to promote.
1363 */
1364 #define cache_neg_hit_abort(ncp) do { } while (0)
1365
1366 static void
cache_neg_hit_finish(struct namecache * ncp)1367 cache_neg_hit_finish(struct namecache *ncp)
1368 {
1369
1370 SDT_PROBE2(vfs, namecache, lookup, hit__negative, ncp->nc_dvp, ncp->nc_name);
1371 counter_u64_add(numneghits, 1);
1372 }
1373
1374 /*
1375 * Move a negative entry to the hot list.
1376 */
1377 static void
cache_neg_promote_locked(struct namecache * ncp)1378 cache_neg_promote_locked(struct namecache *ncp)
1379 {
1380 struct neglist *nl;
1381 struct negstate *ns;
1382
1383 ns = NCP2NEGSTATE(ncp);
1384 nl = NCP2NEGLIST(ncp);
1385 mtx_assert(&nl->nl_lock, MA_OWNED);
1386 if ((ns->neg_flag & NEG_HOT) == 0) {
1387 TAILQ_REMOVE(&nl->nl_list, ncp, nc_dst);
1388 TAILQ_INSERT_TAIL(&nl->nl_hotlist, ncp, nc_dst);
1389 nl->nl_hotnum++;
1390 ns->neg_flag |= NEG_HOT;
1391 }
1392 }
1393
1394 /*
1395 * Move a hot negative entry to the cold list.
1396 */
1397 static void
cache_neg_demote_locked(struct namecache * ncp)1398 cache_neg_demote_locked(struct namecache *ncp)
1399 {
1400 struct neglist *nl;
1401 struct negstate *ns;
1402
1403 ns = NCP2NEGSTATE(ncp);
1404 nl = NCP2NEGLIST(ncp);
1405 mtx_assert(&nl->nl_lock, MA_OWNED);
1406 MPASS(ns->neg_flag & NEG_HOT);
1407 TAILQ_REMOVE(&nl->nl_hotlist, ncp, nc_dst);
1408 TAILQ_INSERT_TAIL(&nl->nl_list, ncp, nc_dst);
1409 nl->nl_hotnum--;
1410 ns->neg_flag &= ~NEG_HOT;
1411 atomic_store_char(&ns->neg_hit, 0);
1412 }
1413
1414 /*
1415 * Move a negative entry to the hot list if it matches the lookup.
1416 *
1417 * We have to take locks, but they may be contended and in the worst
1418 * case we may need to go off CPU. We don't want to spin within the
1419 * smr section and we can't block with it. Exiting the section means
1420 * the found entry could have been evicted. We are going to look it
1421 * up again.
1422 */
1423 static bool
cache_neg_promote_cond(struct vnode * dvp,struct componentname * cnp,struct namecache * oncp,uint32_t hash)1424 cache_neg_promote_cond(struct vnode *dvp, struct componentname *cnp,
1425 struct namecache *oncp, uint32_t hash)
1426 {
1427 struct namecache *ncp;
1428 struct neglist *nl;
1429 u_char nc_flag;
1430
1431 nl = NCP2NEGLIST(oncp);
1432
1433 mtx_lock(&nl->nl_lock);
1434 /*
1435 * For hash iteration.
1436 */
1437 vfs_smr_enter();
1438
1439 /*
1440 * Avoid all surprises by only succeeding if we got the same entry and
1441 * bailing completely otherwise.
1442 * XXX There are no provisions to keep the vnode around, meaning we may
1443 * end up promoting a negative entry for a *new* vnode and returning
1444 * ENOENT on its account. This is the error we want to return anyway
1445 * and promotion is harmless.
1446 *
1447 * In particular at this point there can be a new ncp which matches the
1448 * search but hashes to a different neglist.
1449 */
1450 CK_SLIST_FOREACH(ncp, (NCHHASH(hash)), nc_hash) {
1451 if (ncp == oncp)
1452 break;
1453 }
1454
1455 /*
1456 * No match to begin with.
1457 */
1458 if (__predict_false(ncp == NULL)) {
1459 goto out_abort;
1460 }
1461
1462 /*
1463 * The newly found entry may be something different...
1464 */
1465 if (!cache_ncp_match(ncp, dvp, cnp)) {
1466 goto out_abort;
1467 }
1468
1469 /*
1470 * ... and not even negative.
1471 */
1472 nc_flag = atomic_load_char(&ncp->nc_flag);
1473 if ((nc_flag & NCF_NEGATIVE) == 0) {
1474 goto out_abort;
1475 }
1476
1477 if (!cache_ncp_canuse(ncp)) {
1478 goto out_abort;
1479 }
1480
1481 cache_neg_promote_locked(ncp);
1482 cache_neg_hit_finish(ncp);
1483 vfs_smr_exit();
1484 mtx_unlock(&nl->nl_lock);
1485 return (true);
1486 out_abort:
1487 vfs_smr_exit();
1488 mtx_unlock(&nl->nl_lock);
1489 return (false);
1490 }
1491
1492 static void
cache_neg_promote(struct namecache * ncp)1493 cache_neg_promote(struct namecache *ncp)
1494 {
1495 struct neglist *nl;
1496
1497 nl = NCP2NEGLIST(ncp);
1498 mtx_lock(&nl->nl_lock);
1499 cache_neg_promote_locked(ncp);
1500 mtx_unlock(&nl->nl_lock);
1501 }
1502
1503 static void
cache_neg_insert(struct namecache * ncp)1504 cache_neg_insert(struct namecache *ncp)
1505 {
1506 struct neglist *nl;
1507
1508 MPASS(ncp->nc_flag & NCF_NEGATIVE);
1509 cache_assert_bucket_locked(ncp);
1510 nl = NCP2NEGLIST(ncp);
1511 mtx_lock(&nl->nl_lock);
1512 TAILQ_INSERT_TAIL(&nl->nl_list, ncp, nc_dst);
1513 mtx_unlock(&nl->nl_lock);
1514 atomic_add_long(&numneg, 1);
1515 }
1516
1517 static void
cache_neg_remove(struct namecache * ncp)1518 cache_neg_remove(struct namecache *ncp)
1519 {
1520 struct neglist *nl;
1521 struct negstate *ns;
1522
1523 cache_assert_bucket_locked(ncp);
1524 nl = NCP2NEGLIST(ncp);
1525 ns = NCP2NEGSTATE(ncp);
1526 mtx_lock(&nl->nl_lock);
1527 if ((ns->neg_flag & NEG_HOT) != 0) {
1528 TAILQ_REMOVE(&nl->nl_hotlist, ncp, nc_dst);
1529 nl->nl_hotnum--;
1530 } else {
1531 TAILQ_REMOVE(&nl->nl_list, ncp, nc_dst);
1532 }
1533 mtx_unlock(&nl->nl_lock);
1534 atomic_subtract_long(&numneg, 1);
1535 }
1536
1537 static struct neglist *
cache_neg_evict_select_list(void)1538 cache_neg_evict_select_list(void)
1539 {
1540 struct neglist *nl;
1541 u_int c;
1542
1543 c = atomic_fetchadd_int(&neg_cycle, 1) + 1;
1544 nl = &neglists[c % numneglists];
1545 if (!mtx_trylock(&nl->nl_evict_lock)) {
1546 counter_u64_add(neg_evict_skipped_contended, 1);
1547 return (NULL);
1548 }
1549 return (nl);
1550 }
1551
1552 static struct namecache *
cache_neg_evict_select_entry(struct neglist * nl)1553 cache_neg_evict_select_entry(struct neglist *nl)
1554 {
1555 struct namecache *ncp, *lncp;
1556 struct negstate *ns, *lns;
1557 int i;
1558
1559 mtx_assert(&nl->nl_evict_lock, MA_OWNED);
1560 mtx_assert(&nl->nl_lock, MA_OWNED);
1561 ncp = TAILQ_FIRST(&nl->nl_list);
1562 if (ncp == NULL)
1563 return (NULL);
1564 lncp = ncp;
1565 lns = NCP2NEGSTATE(lncp);
1566 for (i = 1; i < 4; i++) {
1567 ncp = TAILQ_NEXT(ncp, nc_dst);
1568 if (ncp == NULL)
1569 break;
1570 ns = NCP2NEGSTATE(ncp);
1571 if (ns->neg_hit < lns->neg_hit) {
1572 lncp = ncp;
1573 lns = ns;
1574 }
1575 }
1576 return (lncp);
1577 }
1578
1579 static bool
cache_neg_evict(void)1580 cache_neg_evict(void)
1581 {
1582 struct namecache *ncp, *ncp2;
1583 struct neglist *nl;
1584 struct vnode *dvp;
1585 struct mtx *dvlp;
1586 struct mtx *blp;
1587 uint32_t hash;
1588 u_char nlen;
1589 bool evicted;
1590
1591 nl = cache_neg_evict_select_list();
1592 if (nl == NULL) {
1593 return (false);
1594 }
1595
1596 mtx_lock(&nl->nl_lock);
1597 ncp = TAILQ_FIRST(&nl->nl_hotlist);
1598 if (ncp != NULL) {
1599 cache_neg_demote_locked(ncp);
1600 }
1601 ncp = cache_neg_evict_select_entry(nl);
1602 if (ncp == NULL) {
1603 counter_u64_add(neg_evict_skipped_empty, 1);
1604 mtx_unlock(&nl->nl_lock);
1605 mtx_unlock(&nl->nl_evict_lock);
1606 return (false);
1607 }
1608 nlen = ncp->nc_nlen;
1609 dvp = ncp->nc_dvp;
1610 hash = cache_get_hash(ncp->nc_name, nlen, dvp);
1611 dvlp = VP2VNODELOCK(dvp);
1612 blp = HASH2BUCKETLOCK(hash);
1613 mtx_unlock(&nl->nl_lock);
1614 mtx_unlock(&nl->nl_evict_lock);
1615 mtx_lock(dvlp);
1616 mtx_lock(blp);
1617 /*
1618 * Note that since all locks were dropped above, the entry may be
1619 * gone or reallocated to be something else.
1620 */
1621 CK_SLIST_FOREACH(ncp2, (NCHHASH(hash)), nc_hash) {
1622 if (ncp2 == ncp && ncp2->nc_dvp == dvp &&
1623 ncp2->nc_nlen == nlen && (ncp2->nc_flag & NCF_NEGATIVE) != 0)
1624 break;
1625 }
1626 if (ncp2 == NULL) {
1627 counter_u64_add(neg_evict_skipped_missed, 1);
1628 ncp = NULL;
1629 evicted = false;
1630 } else {
1631 MPASS(dvlp == VP2VNODELOCK(ncp->nc_dvp));
1632 MPASS(blp == NCP2BUCKETLOCK(ncp));
1633 SDT_PROBE2(vfs, namecache, evict_negative, done, ncp->nc_dvp,
1634 ncp->nc_name);
1635 cache_zap_locked(ncp);
1636 counter_u64_add(neg_evicted, 1);
1637 evicted = true;
1638 }
1639 mtx_unlock(blp);
1640 mtx_unlock(dvlp);
1641 if (ncp != NULL)
1642 cache_free(ncp);
1643 return (evicted);
1644 }
1645
1646 /*
1647 * Maybe evict a negative entry to create more room.
1648 *
1649 * The ncnegfactor parameter limits what fraction of the total count
1650 * can comprise of negative entries. However, if the cache is just
1651 * warming up this leads to excessive evictions. As such, ncnegminpct
1652 * (recomputed to neg_min) dictates whether the above should be
1653 * applied.
1654 *
1655 * Try evicting if the cache is close to full capacity regardless of
1656 * other considerations.
1657 */
1658 static bool
cache_neg_evict_cond(u_long lnumcache)1659 cache_neg_evict_cond(u_long lnumcache)
1660 {
1661 u_long lnumneg;
1662
1663 if (ncsize - 1000 < lnumcache)
1664 goto out_evict;
1665 lnumneg = atomic_load_long(&numneg);
1666 if (lnumneg < neg_min)
1667 return (false);
1668 if (lnumneg * ncnegfactor < lnumcache)
1669 return (false);
1670 out_evict:
1671 return (cache_neg_evict());
1672 }
1673
1674 /*
1675 * cache_zap_locked():
1676 *
1677 * Removes a namecache entry from cache, whether it contains an actual
1678 * pointer to a vnode or if it is just a negative cache entry.
1679 */
1680 static void
cache_zap_locked(struct namecache * ncp)1681 cache_zap_locked(struct namecache *ncp)
1682 {
1683 struct nchashhead *ncpp;
1684 struct vnode *dvp, *vp;
1685
1686 dvp = ncp->nc_dvp;
1687 vp = ncp->nc_vp;
1688
1689 if (!(ncp->nc_flag & NCF_NEGATIVE))
1690 cache_assert_vnode_locked(vp);
1691 cache_assert_vnode_locked(dvp);
1692 cache_assert_bucket_locked(ncp);
1693
1694 cache_ncp_invalidate(ncp);
1695
1696 ncpp = NCP2BUCKET(ncp);
1697 CK_SLIST_REMOVE(ncpp, ncp, namecache, nc_hash);
1698 if (!(ncp->nc_flag & NCF_NEGATIVE)) {
1699 SDT_PROBE3(vfs, namecache, zap, done, dvp, ncp->nc_name, vp);
1700 TAILQ_REMOVE(&vp->v_cache_dst, ncp, nc_dst);
1701 if (ncp == vp->v_cache_dd) {
1702 atomic_store_ptr(&vp->v_cache_dd, NULL);
1703 }
1704 } else {
1705 SDT_PROBE2(vfs, namecache, zap_negative, done, dvp, ncp->nc_name);
1706 cache_neg_remove(ncp);
1707 }
1708 if (ncp->nc_flag & NCF_ISDOTDOT) {
1709 if (ncp == dvp->v_cache_dd) {
1710 atomic_store_ptr(&dvp->v_cache_dd, NULL);
1711 }
1712 } else {
1713 LIST_REMOVE(ncp, nc_src);
1714 if (LIST_EMPTY(&dvp->v_cache_src)) {
1715 ncp->nc_flag |= NCF_DVDROP;
1716 }
1717 }
1718 }
1719
1720 static void
cache_zap_negative_locked_vnode_kl(struct namecache * ncp,struct vnode * vp)1721 cache_zap_negative_locked_vnode_kl(struct namecache *ncp, struct vnode *vp)
1722 {
1723 struct mtx *blp;
1724
1725 MPASS(ncp->nc_dvp == vp);
1726 MPASS(ncp->nc_flag & NCF_NEGATIVE);
1727 cache_assert_vnode_locked(vp);
1728
1729 blp = NCP2BUCKETLOCK(ncp);
1730 mtx_lock(blp);
1731 cache_zap_locked(ncp);
1732 mtx_unlock(blp);
1733 }
1734
1735 static bool
cache_zap_locked_vnode_kl2(struct namecache * ncp,struct vnode * vp,struct mtx ** vlpp)1736 cache_zap_locked_vnode_kl2(struct namecache *ncp, struct vnode *vp,
1737 struct mtx **vlpp)
1738 {
1739 struct mtx *pvlp, *vlp1, *vlp2, *to_unlock;
1740 struct mtx *blp;
1741
1742 MPASS(vp == ncp->nc_dvp || vp == ncp->nc_vp);
1743 cache_assert_vnode_locked(vp);
1744
1745 if (ncp->nc_flag & NCF_NEGATIVE) {
1746 if (*vlpp != NULL) {
1747 mtx_unlock(*vlpp);
1748 *vlpp = NULL;
1749 }
1750 cache_zap_negative_locked_vnode_kl(ncp, vp);
1751 return (true);
1752 }
1753
1754 pvlp = VP2VNODELOCK(vp);
1755 blp = NCP2BUCKETLOCK(ncp);
1756 vlp1 = VP2VNODELOCK(ncp->nc_dvp);
1757 vlp2 = VP2VNODELOCK(ncp->nc_vp);
1758
1759 if (*vlpp == vlp1 || *vlpp == vlp2) {
1760 to_unlock = *vlpp;
1761 *vlpp = NULL;
1762 } else {
1763 if (*vlpp != NULL) {
1764 mtx_unlock(*vlpp);
1765 *vlpp = NULL;
1766 }
1767 cache_sort_vnodes(&vlp1, &vlp2);
1768 if (vlp1 == pvlp) {
1769 mtx_lock(vlp2);
1770 to_unlock = vlp2;
1771 } else {
1772 if (!mtx_trylock(vlp1))
1773 goto out_relock;
1774 to_unlock = vlp1;
1775 }
1776 }
1777 mtx_lock(blp);
1778 cache_zap_locked(ncp);
1779 mtx_unlock(blp);
1780 if (to_unlock != NULL)
1781 mtx_unlock(to_unlock);
1782 return (true);
1783
1784 out_relock:
1785 mtx_unlock(vlp2);
1786 mtx_lock(vlp1);
1787 mtx_lock(vlp2);
1788 MPASS(*vlpp == NULL);
1789 *vlpp = vlp1;
1790 return (false);
1791 }
1792
1793 /*
1794 * If trylocking failed we can get here. We know enough to take all needed locks
1795 * in the right order and re-lookup the entry.
1796 */
1797 static int
cache_zap_unlocked_bucket(struct namecache * ncp,struct componentname * cnp,struct vnode * dvp,struct mtx * dvlp,struct mtx * vlp,uint32_t hash,struct mtx * blp)1798 cache_zap_unlocked_bucket(struct namecache *ncp, struct componentname *cnp,
1799 struct vnode *dvp, struct mtx *dvlp, struct mtx *vlp, uint32_t hash,
1800 struct mtx *blp)
1801 {
1802 struct namecache *rncp;
1803 struct mtx *rvlp;
1804
1805 cache_assert_bucket_unlocked(ncp);
1806
1807 cache_sort_vnodes(&dvlp, &vlp);
1808 cache_lock_vnodes(dvlp, vlp);
1809 mtx_lock(blp);
1810 CK_SLIST_FOREACH(rncp, (NCHHASH(hash)), nc_hash) {
1811 if (rncp == ncp && cache_ncp_match(rncp, dvp, cnp))
1812 break;
1813 }
1814 if (rncp == NULL)
1815 goto out_mismatch;
1816
1817 if (!(ncp->nc_flag & NCF_NEGATIVE))
1818 rvlp = VP2VNODELOCK(rncp->nc_vp);
1819 else
1820 rvlp = NULL;
1821 if (rvlp != vlp)
1822 goto out_mismatch;
1823
1824 cache_zap_locked(rncp);
1825 mtx_unlock(blp);
1826 cache_unlock_vnodes(dvlp, vlp);
1827 atomic_add_long(&zap_bucket_relock_success, 1);
1828 return (0);
1829
1830 out_mismatch:
1831 mtx_unlock(blp);
1832 cache_unlock_vnodes(dvlp, vlp);
1833 return (EAGAIN);
1834 }
1835
1836 static int __noinline
cache_zap_locked_bucket(struct namecache * ncp,struct componentname * cnp,uint32_t hash,struct mtx * blp)1837 cache_zap_locked_bucket(struct namecache *ncp, struct componentname *cnp,
1838 uint32_t hash, struct mtx *blp)
1839 {
1840 struct mtx *dvlp, *vlp;
1841 struct vnode *dvp;
1842
1843 cache_assert_bucket_locked(ncp);
1844
1845 dvlp = VP2VNODELOCK(ncp->nc_dvp);
1846 vlp = NULL;
1847 if (!(ncp->nc_flag & NCF_NEGATIVE))
1848 vlp = VP2VNODELOCK(ncp->nc_vp);
1849 if (cache_trylock_vnodes(dvlp, vlp) == 0) {
1850 cache_zap_locked(ncp);
1851 mtx_unlock(blp);
1852 cache_unlock_vnodes(dvlp, vlp);
1853 return (0);
1854 }
1855
1856 dvp = ncp->nc_dvp;
1857 mtx_unlock(blp);
1858 return (cache_zap_unlocked_bucket(ncp, cnp, dvp, dvlp, vlp, hash, blp));
1859 }
1860
1861 static __noinline int
cache_remove_cnp(struct vnode * dvp,struct componentname * cnp)1862 cache_remove_cnp(struct vnode *dvp, struct componentname *cnp)
1863 {
1864 struct namecache *ncp;
1865 struct mtx *blp;
1866 struct mtx *dvlp, *dvlp2;
1867 uint32_t hash;
1868 int error;
1869
1870 if (cnp->cn_namelen == 2 &&
1871 cnp->cn_nameptr[0] == '.' && cnp->cn_nameptr[1] == '.') {
1872 dvlp = VP2VNODELOCK(dvp);
1873 dvlp2 = NULL;
1874 mtx_lock(dvlp);
1875 retry_dotdot:
1876 ncp = dvp->v_cache_dd;
1877 if (ncp == NULL) {
1878 mtx_unlock(dvlp);
1879 if (dvlp2 != NULL)
1880 mtx_unlock(dvlp2);
1881 SDT_PROBE2(vfs, namecache, removecnp, miss, dvp, cnp);
1882 return (0);
1883 }
1884 if ((ncp->nc_flag & NCF_ISDOTDOT) != 0) {
1885 if (!cache_zap_locked_vnode_kl2(ncp, dvp, &dvlp2))
1886 goto retry_dotdot;
1887 MPASS(dvp->v_cache_dd == NULL);
1888 mtx_unlock(dvlp);
1889 if (dvlp2 != NULL)
1890 mtx_unlock(dvlp2);
1891 cache_free(ncp);
1892 } else {
1893 atomic_store_ptr(&dvp->v_cache_dd, NULL);
1894 mtx_unlock(dvlp);
1895 if (dvlp2 != NULL)
1896 mtx_unlock(dvlp2);
1897 }
1898 SDT_PROBE2(vfs, namecache, removecnp, hit, dvp, cnp);
1899 return (1);
1900 }
1901
1902 /*
1903 * XXX note that access here is completely unlocked with no provisions
1904 * to keep the hash allocated. If one is sufficiently unlucky a
1905 * parallel cache resize can reallocate the hash, unmap backing pages
1906 * and cause the empty check below to fault.
1907 *
1908 * Fixing this has epsilon priority, but can be done with no overhead
1909 * for this codepath with sufficient effort.
1910 */
1911 hash = cache_get_hash(cnp->cn_nameptr, cnp->cn_namelen, dvp);
1912 blp = HASH2BUCKETLOCK(hash);
1913 retry:
1914 if (CK_SLIST_EMPTY(NCHHASH(hash)))
1915 goto out_no_entry;
1916
1917 mtx_lock(blp);
1918 ncp = cache_ncp_find(dvp, cnp, hash);
1919 if (ncp == NULL) {
1920 mtx_unlock(blp);
1921 goto out_no_entry;
1922 }
1923
1924 error = cache_zap_locked_bucket(ncp, cnp, hash, blp);
1925 if (__predict_false(error != 0)) {
1926 atomic_add_long(&zap_bucket_fail, 1);
1927 goto retry;
1928 }
1929 counter_u64_add(numposzaps, 1);
1930 SDT_PROBE2(vfs, namecache, removecnp, hit, dvp, cnp);
1931 cache_free(ncp);
1932 return (1);
1933 out_no_entry:
1934 counter_u64_add(nummisszap, 1);
1935 SDT_PROBE2(vfs, namecache, removecnp, miss, dvp, cnp);
1936 return (0);
1937 }
1938
1939 static int __noinline
cache_lookup_dot(struct vnode * dvp,struct vnode ** vpp,struct componentname * cnp,struct timespec * tsp,int * ticksp)1940 cache_lookup_dot(struct vnode *dvp, struct vnode **vpp, struct componentname *cnp,
1941 struct timespec *tsp, int *ticksp)
1942 {
1943 int ltype;
1944
1945 *vpp = dvp;
1946 SDT_PROBE3(vfs, namecache, lookup, hit, dvp, ".", *vpp);
1947 if (tsp != NULL)
1948 timespecclear(tsp);
1949 if (ticksp != NULL)
1950 *ticksp = ticks;
1951 vrefact(*vpp);
1952 /*
1953 * When we lookup "." we still can be asked to lock it
1954 * differently...
1955 */
1956 ltype = cnp->cn_lkflags & LK_TYPE_MASK;
1957 if (ltype != VOP_ISLOCKED(*vpp)) {
1958 if (ltype == LK_EXCLUSIVE) {
1959 vn_lock(*vpp, LK_UPGRADE | LK_RETRY);
1960 if (VN_IS_DOOMED((*vpp))) {
1961 /* forced unmount */
1962 vrele(*vpp);
1963 *vpp = NULL;
1964 return (ENOENT);
1965 }
1966 } else
1967 vn_lock(*vpp, LK_DOWNGRADE | LK_RETRY);
1968 }
1969 return (-1);
1970 }
1971
1972 static int __noinline
cache_lookup_dotdot(struct vnode * dvp,struct vnode ** vpp,struct componentname * cnp,struct timespec * tsp,int * ticksp)1973 cache_lookup_dotdot(struct vnode *dvp, struct vnode **vpp, struct componentname *cnp,
1974 struct timespec *tsp, int *ticksp)
1975 {
1976 struct namecache_ts *ncp_ts;
1977 struct namecache *ncp;
1978 struct mtx *dvlp;
1979 enum vgetstate vs;
1980 int error, ltype;
1981 bool whiteout;
1982
1983 MPASS((cnp->cn_flags & ISDOTDOT) != 0);
1984
1985 if ((cnp->cn_flags & MAKEENTRY) == 0) {
1986 cache_remove_cnp(dvp, cnp);
1987 return (0);
1988 }
1989
1990 retry:
1991 dvlp = VP2VNODELOCK(dvp);
1992 mtx_lock(dvlp);
1993 ncp = dvp->v_cache_dd;
1994 if (ncp == NULL) {
1995 SDT_PROBE2(vfs, namecache, lookup, miss, dvp, "..");
1996 mtx_unlock(dvlp);
1997 return (0);
1998 }
1999 if ((ncp->nc_flag & NCF_ISDOTDOT) != 0) {
2000 if (ncp->nc_flag & NCF_NEGATIVE)
2001 *vpp = NULL;
2002 else
2003 *vpp = ncp->nc_vp;
2004 } else
2005 *vpp = ncp->nc_dvp;
2006 if (*vpp == NULL)
2007 goto negative_success;
2008 SDT_PROBE3(vfs, namecache, lookup, hit, dvp, "..", *vpp);
2009 cache_out_ts(ncp, tsp, ticksp);
2010 if ((ncp->nc_flag & (NCF_ISDOTDOT | NCF_DTS)) ==
2011 NCF_DTS && tsp != NULL) {
2012 ncp_ts = __containerof(ncp, struct namecache_ts, nc_nc);
2013 *tsp = ncp_ts->nc_dotdottime;
2014 }
2015
2016 MPASS(dvp != *vpp);
2017 ltype = VOP_ISLOCKED(dvp);
2018 VOP_UNLOCK(dvp);
2019 vs = vget_prep(*vpp);
2020 mtx_unlock(dvlp);
2021 error = vget_finish(*vpp, cnp->cn_lkflags, vs);
2022 vn_lock(dvp, ltype | LK_RETRY);
2023 if (VN_IS_DOOMED(dvp)) {
2024 if (error == 0)
2025 vput(*vpp);
2026 *vpp = NULL;
2027 return (ENOENT);
2028 }
2029 if (error) {
2030 *vpp = NULL;
2031 goto retry;
2032 }
2033 return (-1);
2034 negative_success:
2035 if (__predict_false(cnp->cn_nameiop == CREATE)) {
2036 if (cnp->cn_flags & ISLASTCN) {
2037 counter_u64_add(numnegzaps, 1);
2038 cache_zap_negative_locked_vnode_kl(ncp, dvp);
2039 mtx_unlock(dvlp);
2040 cache_free(ncp);
2041 return (0);
2042 }
2043 }
2044
2045 whiteout = (ncp->nc_flag & NCF_WHITE);
2046 cache_out_ts(ncp, tsp, ticksp);
2047 if (cache_neg_hit_prep(ncp))
2048 cache_neg_promote(ncp);
2049 else
2050 cache_neg_hit_finish(ncp);
2051 mtx_unlock(dvlp);
2052 if (whiteout)
2053 cnp->cn_flags |= ISWHITEOUT;
2054 return (ENOENT);
2055 }
2056
2057 /**
2058 * Lookup a name in the name cache
2059 *
2060 * # Arguments
2061 *
2062 * - dvp: Parent directory in which to search.
2063 * - vpp: Return argument. Will contain desired vnode on cache hit.
2064 * - cnp: Parameters of the name search. The most interesting bits of
2065 * the cn_flags field have the following meanings:
2066 * - MAKEENTRY: If clear, free an entry from the cache rather than look
2067 * it up.
2068 * - ISDOTDOT: Must be set if and only if cn_nameptr == ".."
2069 * - tsp: Return storage for cache timestamp. On a successful (positive
2070 * or negative) lookup, tsp will be filled with any timespec that
2071 * was stored when this cache entry was created. However, it will
2072 * be clear for "." entries.
2073 * - ticks: Return storage for alternate cache timestamp. On a successful
2074 * (positive or negative) lookup, it will contain the ticks value
2075 * that was current when the cache entry was created, unless cnp
2076 * was ".".
2077 *
2078 * Either both tsp and ticks have to be provided or neither of them.
2079 *
2080 * # Returns
2081 *
2082 * - -1: A positive cache hit. vpp will contain the desired vnode.
2083 * - ENOENT: A negative cache hit, or dvp was recycled out from under us due
2084 * to a forced unmount. vpp will not be modified. If the entry
2085 * is a whiteout, then the ISWHITEOUT flag will be set in
2086 * cnp->cn_flags.
2087 * - 0: A cache miss. vpp will not be modified.
2088 *
2089 * # Locking
2090 *
2091 * On a cache hit, vpp will be returned locked and ref'd. If we're looking up
2092 * .., dvp is unlocked. If we're looking up . an extra ref is taken, but the
2093 * lock is not recursively acquired.
2094 */
2095 static int __noinline
cache_lookup_fallback(struct vnode * dvp,struct vnode ** vpp,struct componentname * cnp,struct timespec * tsp,int * ticksp)2096 cache_lookup_fallback(struct vnode *dvp, struct vnode **vpp, struct componentname *cnp,
2097 struct timespec *tsp, int *ticksp)
2098 {
2099 struct namecache *ncp;
2100 struct mtx *blp;
2101 uint32_t hash;
2102 enum vgetstate vs;
2103 int error;
2104 bool whiteout;
2105
2106 MPASS((cnp->cn_flags & ISDOTDOT) == 0);
2107 MPASS((cnp->cn_flags & (MAKEENTRY | NC_KEEPPOSENTRY)) != 0);
2108
2109 retry:
2110 hash = cache_get_hash(cnp->cn_nameptr, cnp->cn_namelen, dvp);
2111 blp = HASH2BUCKETLOCK(hash);
2112 mtx_lock(blp);
2113
2114 ncp = cache_ncp_find(dvp, cnp, hash);
2115 if (__predict_false(ncp == NULL)) {
2116 mtx_unlock(blp);
2117 SDT_PROBE2(vfs, namecache, lookup, miss, dvp, cnp->cn_nameptr);
2118 counter_u64_add(nummiss, 1);
2119 return (0);
2120 }
2121
2122 if (ncp->nc_flag & NCF_NEGATIVE)
2123 goto negative_success;
2124
2125 counter_u64_add(numposhits, 1);
2126 *vpp = ncp->nc_vp;
2127 SDT_PROBE3(vfs, namecache, lookup, hit, dvp, ncp->nc_name, *vpp);
2128 cache_out_ts(ncp, tsp, ticksp);
2129 MPASS(dvp != *vpp);
2130 vs = vget_prep(*vpp);
2131 mtx_unlock(blp);
2132 error = vget_finish(*vpp, cnp->cn_lkflags, vs);
2133 if (error) {
2134 *vpp = NULL;
2135 goto retry;
2136 }
2137 return (-1);
2138 negative_success:
2139 /*
2140 * We don't get here with regular lookup apart from corner cases.
2141 */
2142 if (__predict_true(cnp->cn_nameiop == CREATE)) {
2143 if (cnp->cn_flags & ISLASTCN) {
2144 counter_u64_add(numnegzaps, 1);
2145 error = cache_zap_locked_bucket(ncp, cnp, hash, blp);
2146 if (__predict_false(error != 0)) {
2147 atomic_add_long(&zap_bucket_fail2, 1);
2148 goto retry;
2149 }
2150 cache_free(ncp);
2151 return (0);
2152 }
2153 }
2154
2155 whiteout = (ncp->nc_flag & NCF_WHITE);
2156 cache_out_ts(ncp, tsp, ticksp);
2157 if (cache_neg_hit_prep(ncp))
2158 cache_neg_promote(ncp);
2159 else
2160 cache_neg_hit_finish(ncp);
2161 mtx_unlock(blp);
2162 if (whiteout)
2163 cnp->cn_flags |= ISWHITEOUT;
2164 return (ENOENT);
2165 }
2166
2167 int
cache_lookup(struct vnode * dvp,struct vnode ** vpp,struct componentname * cnp,struct timespec * tsp,int * ticksp)2168 cache_lookup(struct vnode *dvp, struct vnode **vpp, struct componentname *cnp,
2169 struct timespec *tsp, int *ticksp)
2170 {
2171 struct namecache *ncp;
2172 uint32_t hash;
2173 enum vgetstate vs;
2174 int error;
2175 bool whiteout, neg_promote;
2176 u_short nc_flag;
2177
2178 MPASS((tsp == NULL && ticksp == NULL) || (tsp != NULL && ticksp != NULL));
2179
2180 #ifdef DEBUG_CACHE
2181 if (__predict_false(!doingcache)) {
2182 cnp->cn_flags &= ~MAKEENTRY;
2183 return (0);
2184 }
2185 #endif
2186
2187 if (__predict_false(cnp->cn_nameptr[0] == '.')) {
2188 if (cnp->cn_namelen == 1)
2189 return (cache_lookup_dot(dvp, vpp, cnp, tsp, ticksp));
2190 if (cnp->cn_namelen == 2 && cnp->cn_nameptr[1] == '.')
2191 return (cache_lookup_dotdot(dvp, vpp, cnp, tsp, ticksp));
2192 }
2193
2194 MPASS((cnp->cn_flags & ISDOTDOT) == 0);
2195
2196 if ((cnp->cn_flags & (MAKEENTRY | NC_KEEPPOSENTRY)) == 0) {
2197 cache_remove_cnp(dvp, cnp);
2198 return (0);
2199 }
2200
2201 hash = cache_get_hash(cnp->cn_nameptr, cnp->cn_namelen, dvp);
2202 vfs_smr_enter();
2203
2204 ncp = cache_ncp_find(dvp, cnp, hash);
2205 if (__predict_false(ncp == NULL)) {
2206 vfs_smr_exit();
2207 SDT_PROBE2(vfs, namecache, lookup, miss, dvp, cnp->cn_nameptr);
2208 counter_u64_add(nummiss, 1);
2209 return (0);
2210 }
2211
2212 nc_flag = atomic_load_char(&ncp->nc_flag);
2213 if (nc_flag & NCF_NEGATIVE)
2214 goto negative_success;
2215
2216 counter_u64_add(numposhits, 1);
2217 *vpp = ncp->nc_vp;
2218 SDT_PROBE3(vfs, namecache, lookup, hit, dvp, ncp->nc_name, *vpp);
2219 cache_out_ts(ncp, tsp, ticksp);
2220 MPASS(dvp != *vpp);
2221 if (!cache_ncp_canuse(ncp)) {
2222 vfs_smr_exit();
2223 *vpp = NULL;
2224 goto out_fallback;
2225 }
2226 vs = vget_prep_smr(*vpp);
2227 vfs_smr_exit();
2228 if (__predict_false(vs == VGET_NONE)) {
2229 *vpp = NULL;
2230 goto out_fallback;
2231 }
2232 error = vget_finish(*vpp, cnp->cn_lkflags, vs);
2233 if (error) {
2234 *vpp = NULL;
2235 goto out_fallback;
2236 }
2237 return (-1);
2238 negative_success:
2239 if (cnp->cn_nameiop == CREATE) {
2240 if (cnp->cn_flags & ISLASTCN) {
2241 vfs_smr_exit();
2242 goto out_fallback;
2243 }
2244 }
2245
2246 cache_out_ts(ncp, tsp, ticksp);
2247 whiteout = (atomic_load_char(&ncp->nc_flag) & NCF_WHITE);
2248 neg_promote = cache_neg_hit_prep(ncp);
2249 if (!cache_ncp_canuse(ncp)) {
2250 cache_neg_hit_abort(ncp);
2251 vfs_smr_exit();
2252 goto out_fallback;
2253 }
2254 if (neg_promote) {
2255 vfs_smr_exit();
2256 if (!cache_neg_promote_cond(dvp, cnp, ncp, hash))
2257 goto out_fallback;
2258 } else {
2259 cache_neg_hit_finish(ncp);
2260 vfs_smr_exit();
2261 }
2262 if (whiteout)
2263 cnp->cn_flags |= ISWHITEOUT;
2264 return (ENOENT);
2265 out_fallback:
2266 return (cache_lookup_fallback(dvp, vpp, cnp, tsp, ticksp));
2267 }
2268
2269 struct celockstate {
2270 struct mtx *vlp[3];
2271 struct mtx *blp[2];
2272 };
2273 CTASSERT((nitems(((struct celockstate *)0)->vlp) == 3));
2274 CTASSERT((nitems(((struct celockstate *)0)->blp) == 2));
2275
2276 static inline void
cache_celockstate_init(struct celockstate * cel)2277 cache_celockstate_init(struct celockstate *cel)
2278 {
2279
2280 bzero(cel, sizeof(*cel));
2281 }
2282
2283 static void
cache_lock_vnodes_cel(struct celockstate * cel,struct vnode * vp,struct vnode * dvp)2284 cache_lock_vnodes_cel(struct celockstate *cel, struct vnode *vp,
2285 struct vnode *dvp)
2286 {
2287 struct mtx *vlp1, *vlp2;
2288
2289 MPASS(cel->vlp[0] == NULL);
2290 MPASS(cel->vlp[1] == NULL);
2291 MPASS(cel->vlp[2] == NULL);
2292
2293 MPASS(vp != NULL || dvp != NULL);
2294
2295 vlp1 = VP2VNODELOCK(vp);
2296 vlp2 = VP2VNODELOCK(dvp);
2297 cache_sort_vnodes(&vlp1, &vlp2);
2298
2299 if (vlp1 != NULL) {
2300 mtx_lock(vlp1);
2301 cel->vlp[0] = vlp1;
2302 }
2303 mtx_lock(vlp2);
2304 cel->vlp[1] = vlp2;
2305 }
2306
2307 static void
cache_unlock_vnodes_cel(struct celockstate * cel)2308 cache_unlock_vnodes_cel(struct celockstate *cel)
2309 {
2310
2311 MPASS(cel->vlp[0] != NULL || cel->vlp[1] != NULL);
2312
2313 if (cel->vlp[0] != NULL)
2314 mtx_unlock(cel->vlp[0]);
2315 if (cel->vlp[1] != NULL)
2316 mtx_unlock(cel->vlp[1]);
2317 if (cel->vlp[2] != NULL)
2318 mtx_unlock(cel->vlp[2]);
2319 }
2320
2321 static bool
cache_lock_vnodes_cel_3(struct celockstate * cel,struct vnode * vp)2322 cache_lock_vnodes_cel_3(struct celockstate *cel, struct vnode *vp)
2323 {
2324 struct mtx *vlp;
2325 bool ret;
2326
2327 cache_assert_vlp_locked(cel->vlp[0]);
2328 cache_assert_vlp_locked(cel->vlp[1]);
2329 MPASS(cel->vlp[2] == NULL);
2330
2331 MPASS(vp != NULL);
2332 vlp = VP2VNODELOCK(vp);
2333
2334 ret = true;
2335 if (vlp >= cel->vlp[1]) {
2336 mtx_lock(vlp);
2337 } else {
2338 if (mtx_trylock(vlp))
2339 goto out;
2340 cache_unlock_vnodes_cel(cel);
2341 atomic_add_long(&cache_lock_vnodes_cel_3_failures, 1);
2342 if (vlp < cel->vlp[0]) {
2343 mtx_lock(vlp);
2344 mtx_lock(cel->vlp[0]);
2345 mtx_lock(cel->vlp[1]);
2346 } else {
2347 if (cel->vlp[0] != NULL)
2348 mtx_lock(cel->vlp[0]);
2349 mtx_lock(vlp);
2350 mtx_lock(cel->vlp[1]);
2351 }
2352 ret = false;
2353 }
2354 out:
2355 cel->vlp[2] = vlp;
2356 return (ret);
2357 }
2358
2359 static void
cache_lock_buckets_cel(struct celockstate * cel,struct mtx * blp1,struct mtx * blp2)2360 cache_lock_buckets_cel(struct celockstate *cel, struct mtx *blp1,
2361 struct mtx *blp2)
2362 {
2363
2364 MPASS(cel->blp[0] == NULL);
2365 MPASS(cel->blp[1] == NULL);
2366
2367 cache_sort_vnodes(&blp1, &blp2);
2368
2369 if (blp1 != NULL) {
2370 mtx_lock(blp1);
2371 cel->blp[0] = blp1;
2372 }
2373 mtx_lock(blp2);
2374 cel->blp[1] = blp2;
2375 }
2376
2377 static void
cache_unlock_buckets_cel(struct celockstate * cel)2378 cache_unlock_buckets_cel(struct celockstate *cel)
2379 {
2380
2381 if (cel->blp[0] != NULL)
2382 mtx_unlock(cel->blp[0]);
2383 mtx_unlock(cel->blp[1]);
2384 }
2385
2386 /*
2387 * Lock part of the cache affected by the insertion.
2388 *
2389 * This means vnodelocks for dvp, vp and the relevant bucketlock.
2390 * However, insertion can result in removal of an old entry. In this
2391 * case we have an additional vnode and bucketlock pair to lock.
2392 *
2393 * That is, in the worst case we have to lock 3 vnodes and 2 bucketlocks, while
2394 * preserving the locking order (smaller address first).
2395 */
2396 static void
cache_enter_lock(struct celockstate * cel,struct vnode * dvp,struct vnode * vp,uint32_t hash)2397 cache_enter_lock(struct celockstate *cel, struct vnode *dvp, struct vnode *vp,
2398 uint32_t hash)
2399 {
2400 struct namecache *ncp;
2401 struct mtx *blps[2];
2402 u_char nc_flag;
2403
2404 blps[0] = HASH2BUCKETLOCK(hash);
2405 for (;;) {
2406 blps[1] = NULL;
2407 cache_lock_vnodes_cel(cel, dvp, vp);
2408 if (vp == NULL || vp->v_type != VDIR)
2409 break;
2410 ncp = atomic_load_consume_ptr(&vp->v_cache_dd);
2411 if (ncp == NULL)
2412 break;
2413 nc_flag = atomic_load_char(&ncp->nc_flag);
2414 if ((nc_flag & NCF_ISDOTDOT) == 0)
2415 break;
2416 MPASS(ncp->nc_dvp == vp);
2417 blps[1] = NCP2BUCKETLOCK(ncp);
2418 if ((nc_flag & NCF_NEGATIVE) != 0)
2419 break;
2420 if (cache_lock_vnodes_cel_3(cel, ncp->nc_vp))
2421 break;
2422 /*
2423 * All vnodes got re-locked. Re-validate the state and if
2424 * nothing changed we are done. Otherwise restart.
2425 */
2426 if (ncp == vp->v_cache_dd &&
2427 (ncp->nc_flag & NCF_ISDOTDOT) != 0 &&
2428 blps[1] == NCP2BUCKETLOCK(ncp) &&
2429 VP2VNODELOCK(ncp->nc_vp) == cel->vlp[2])
2430 break;
2431 cache_unlock_vnodes_cel(cel);
2432 cel->vlp[0] = NULL;
2433 cel->vlp[1] = NULL;
2434 cel->vlp[2] = NULL;
2435 }
2436 cache_lock_buckets_cel(cel, blps[0], blps[1]);
2437 }
2438
2439 static void
cache_enter_lock_dd(struct celockstate * cel,struct vnode * dvp,struct vnode * vp,uint32_t hash)2440 cache_enter_lock_dd(struct celockstate *cel, struct vnode *dvp, struct vnode *vp,
2441 uint32_t hash)
2442 {
2443 struct namecache *ncp;
2444 struct mtx *blps[2];
2445 u_char nc_flag;
2446
2447 blps[0] = HASH2BUCKETLOCK(hash);
2448 for (;;) {
2449 blps[1] = NULL;
2450 cache_lock_vnodes_cel(cel, dvp, vp);
2451 ncp = atomic_load_consume_ptr(&dvp->v_cache_dd);
2452 if (ncp == NULL)
2453 break;
2454 nc_flag = atomic_load_char(&ncp->nc_flag);
2455 if ((nc_flag & NCF_ISDOTDOT) == 0)
2456 break;
2457 MPASS(ncp->nc_dvp == dvp);
2458 blps[1] = NCP2BUCKETLOCK(ncp);
2459 if ((nc_flag & NCF_NEGATIVE) != 0)
2460 break;
2461 if (cache_lock_vnodes_cel_3(cel, ncp->nc_vp))
2462 break;
2463 if (ncp == dvp->v_cache_dd &&
2464 (ncp->nc_flag & NCF_ISDOTDOT) != 0 &&
2465 blps[1] == NCP2BUCKETLOCK(ncp) &&
2466 VP2VNODELOCK(ncp->nc_vp) == cel->vlp[2])
2467 break;
2468 cache_unlock_vnodes_cel(cel);
2469 cel->vlp[0] = NULL;
2470 cel->vlp[1] = NULL;
2471 cel->vlp[2] = NULL;
2472 }
2473 cache_lock_buckets_cel(cel, blps[0], blps[1]);
2474 }
2475
2476 static void
cache_enter_unlock(struct celockstate * cel)2477 cache_enter_unlock(struct celockstate *cel)
2478 {
2479
2480 cache_unlock_buckets_cel(cel);
2481 cache_unlock_vnodes_cel(cel);
2482 }
2483
2484 static void __noinline
cache_enter_dotdot_prep(struct vnode * dvp,struct vnode * vp,struct componentname * cnp)2485 cache_enter_dotdot_prep(struct vnode *dvp, struct vnode *vp,
2486 struct componentname *cnp)
2487 {
2488 struct celockstate cel;
2489 struct namecache *ncp;
2490 uint32_t hash;
2491 int len;
2492
2493 if (atomic_load_ptr(&dvp->v_cache_dd) == NULL)
2494 return;
2495 len = cnp->cn_namelen;
2496 cache_celockstate_init(&cel);
2497 hash = cache_get_hash(cnp->cn_nameptr, len, dvp);
2498 cache_enter_lock_dd(&cel, dvp, vp, hash);
2499 ncp = dvp->v_cache_dd;
2500 if (ncp != NULL && (ncp->nc_flag & NCF_ISDOTDOT)) {
2501 KASSERT(ncp->nc_dvp == dvp, ("wrong isdotdot parent"));
2502 cache_zap_locked(ncp);
2503 } else {
2504 ncp = NULL;
2505 }
2506 atomic_store_ptr(&dvp->v_cache_dd, NULL);
2507 cache_enter_unlock(&cel);
2508 if (ncp != NULL)
2509 cache_free(ncp);
2510 }
2511
2512 /*
2513 * Add an entry to the cache.
2514 */
2515 void
cache_enter_time(struct vnode * dvp,struct vnode * vp,struct componentname * cnp,struct timespec * tsp,struct timespec * dtsp)2516 cache_enter_time(struct vnode *dvp, struct vnode *vp, struct componentname *cnp,
2517 struct timespec *tsp, struct timespec *dtsp)
2518 {
2519 struct celockstate cel;
2520 struct namecache *ncp, *n2, *ndd;
2521 struct namecache_ts *ncp_ts;
2522 uint32_t hash;
2523 int flag;
2524 int len;
2525
2526 KASSERT(cnp->cn_namelen <= NAME_MAX,
2527 ("%s: passed len %ld exceeds NAME_MAX (%d)", __func__, cnp->cn_namelen,
2528 NAME_MAX));
2529 VNPASS(!VN_IS_DOOMED(dvp), dvp);
2530 VNPASS(dvp->v_type != VNON, dvp);
2531 if (vp != NULL) {
2532 VNPASS(!VN_IS_DOOMED(vp), vp);
2533 VNPASS(vp->v_type != VNON, vp);
2534 }
2535 if (cnp->cn_namelen == 1 && cnp->cn_nameptr[0] == '.') {
2536 KASSERT(dvp == vp,
2537 ("%s: different vnodes for dot entry (%p; %p)\n", __func__,
2538 dvp, vp));
2539 } else {
2540 KASSERT(dvp != vp,
2541 ("%s: same vnode for non-dot entry [%s] (%p)\n", __func__,
2542 cnp->cn_nameptr, dvp));
2543 }
2544
2545 #ifdef DEBUG_CACHE
2546 if (__predict_false(!doingcache))
2547 return;
2548 #endif
2549
2550 flag = 0;
2551 if (__predict_false(cnp->cn_nameptr[0] == '.')) {
2552 if (cnp->cn_namelen == 1)
2553 return;
2554 if (cnp->cn_namelen == 2 && cnp->cn_nameptr[1] == '.') {
2555 cache_enter_dotdot_prep(dvp, vp, cnp);
2556 flag = NCF_ISDOTDOT;
2557 }
2558 }
2559
2560 ncp = cache_alloc(cnp->cn_namelen, tsp != NULL);
2561 if (ncp == NULL)
2562 return;
2563
2564 cache_celockstate_init(&cel);
2565 ndd = NULL;
2566 ncp_ts = NULL;
2567
2568 /*
2569 * Calculate the hash key and setup as much of the new
2570 * namecache entry as possible before acquiring the lock.
2571 */
2572 ncp->nc_flag = flag | NCF_WIP;
2573 ncp->nc_vp = vp;
2574 if (vp == NULL)
2575 cache_neg_init(ncp);
2576 ncp->nc_dvp = dvp;
2577 if (tsp != NULL) {
2578 ncp_ts = __containerof(ncp, struct namecache_ts, nc_nc);
2579 ncp_ts->nc_time = *tsp;
2580 ncp_ts->nc_ticks = ticks;
2581 ncp_ts->nc_nc.nc_flag |= NCF_TS;
2582 if (dtsp != NULL) {
2583 ncp_ts->nc_dotdottime = *dtsp;
2584 ncp_ts->nc_nc.nc_flag |= NCF_DTS;
2585 }
2586 }
2587 len = ncp->nc_nlen = cnp->cn_namelen;
2588 hash = cache_get_hash(cnp->cn_nameptr, len, dvp);
2589 memcpy(ncp->nc_name, cnp->cn_nameptr, len);
2590 ncp->nc_name[len] = '\0';
2591 cache_enter_lock(&cel, dvp, vp, hash);
2592
2593 /*
2594 * See if this vnode or negative entry is already in the cache
2595 * with this name. This can happen with concurrent lookups of
2596 * the same path name.
2597 */
2598 n2 = cache_ncp_find(dvp, cnp, hash);
2599 if (n2 != NULL) {
2600 MPASS(cache_ncp_canuse(n2));
2601 if ((n2->nc_flag & NCF_NEGATIVE) != 0)
2602 KASSERT(vp == NULL,
2603 ("%s: found entry pointing to a different vnode "
2604 "(%p != %p); name [%s]",
2605 __func__, NULL, vp, cnp->cn_nameptr));
2606 else
2607 KASSERT(n2->nc_vp == vp,
2608 ("%s: found entry pointing to a different vnode "
2609 "(%p != %p); name [%s]",
2610 __func__, n2->nc_vp, vp, cnp->cn_nameptr));
2611 /*
2612 * Entries are supposed to be immutable unless in the
2613 * process of getting destroyed. Accommodating for
2614 * changing timestamps is possible but not worth it.
2615 * This should be harmless in terms of correctness, in
2616 * the worst case resulting in an earlier expiration.
2617 * Alternatively, the found entry can be replaced
2618 * altogether.
2619 */
2620 MPASS((n2->nc_flag & (NCF_TS | NCF_DTS)) ==
2621 (ncp->nc_flag & (NCF_TS | NCF_DTS)));
2622 #if 0
2623 if (tsp != NULL) {
2624 KASSERT((n2->nc_flag & NCF_TS) != 0,
2625 ("no NCF_TS"));
2626 n2_ts = __containerof(n2, struct namecache_ts, nc_nc);
2627 n2_ts->nc_time = ncp_ts->nc_time;
2628 n2_ts->nc_ticks = ncp_ts->nc_ticks;
2629 if (dtsp != NULL) {
2630 n2_ts->nc_dotdottime = ncp_ts->nc_dotdottime;
2631 n2_ts->nc_nc.nc_flag |= NCF_DTS;
2632 }
2633 }
2634 #endif
2635 SDT_PROBE3(vfs, namecache, enter, duplicate, dvp, ncp->nc_name,
2636 vp);
2637 goto out_unlock_free;
2638 }
2639
2640 if (flag == NCF_ISDOTDOT) {
2641 /*
2642 * See if we are trying to add .. entry, but some other lookup
2643 * has populated v_cache_dd pointer already.
2644 */
2645 if (dvp->v_cache_dd != NULL)
2646 goto out_unlock_free;
2647 KASSERT(vp == NULL || vp->v_type == VDIR,
2648 ("wrong vnode type %p", vp));
2649 atomic_thread_fence_rel();
2650 atomic_store_ptr(&dvp->v_cache_dd, ncp);
2651 } else if (vp != NULL) {
2652 /*
2653 * Take the slow path in INOTIFY(). This flag will be lazily
2654 * cleared by cache_vop_inotify() once all directories referring
2655 * to vp are unwatched.
2656 */
2657 if (__predict_false((vn_irflag_read(dvp) & VIRF_INOTIFY) != 0))
2658 vn_irflag_set_cond(vp, VIRF_INOTIFY_PARENT);
2659
2660 /*
2661 * For this case, the cache entry maps both the
2662 * directory name in it and the name ".." for the
2663 * directory's parent.
2664 */
2665 if ((ndd = vp->v_cache_dd) != NULL) {
2666 if ((ndd->nc_flag & NCF_ISDOTDOT) != 0)
2667 cache_zap_locked(ndd);
2668 else
2669 ndd = NULL;
2670 }
2671 atomic_thread_fence_rel();
2672 atomic_store_ptr(&vp->v_cache_dd, ncp);
2673 }
2674
2675 if (flag != NCF_ISDOTDOT) {
2676 if (LIST_EMPTY(&dvp->v_cache_src)) {
2677 cache_hold_vnode(dvp);
2678 }
2679 LIST_INSERT_HEAD(&dvp->v_cache_src, ncp, nc_src);
2680 }
2681
2682 /*
2683 * If the entry is "negative", we place it into the
2684 * "negative" cache queue, otherwise, we place it into the
2685 * destination vnode's cache entries queue.
2686 */
2687 if (vp != NULL) {
2688 TAILQ_INSERT_HEAD(&vp->v_cache_dst, ncp, nc_dst);
2689 SDT_PROBE3(vfs, namecache, enter, done, dvp, ncp->nc_name,
2690 vp);
2691 } else {
2692 if (cnp->cn_flags & ISWHITEOUT)
2693 atomic_store_char(&ncp->nc_flag, ncp->nc_flag | NCF_WHITE);
2694 cache_neg_insert(ncp);
2695 SDT_PROBE2(vfs, namecache, enter_negative, done, dvp,
2696 ncp->nc_name);
2697 }
2698
2699 /*
2700 * Insert the new namecache entry into the appropriate chain
2701 * within the cache entries table.
2702 */
2703 CK_SLIST_INSERT_HEAD(NCHHASH(hash), ncp, nc_hash);
2704
2705 atomic_thread_fence_rel();
2706 /*
2707 * Mark the entry as fully constructed.
2708 * It is immutable past this point until its removal.
2709 */
2710 atomic_store_char(&ncp->nc_flag, ncp->nc_flag & ~NCF_WIP);
2711
2712 cache_enter_unlock(&cel);
2713 if (ndd != NULL)
2714 cache_free(ndd);
2715 return;
2716 out_unlock_free:
2717 cache_enter_unlock(&cel);
2718 cache_free(ncp);
2719 return;
2720 }
2721
2722 /*
2723 * A variant of the above accepting flags.
2724 *
2725 * - VFS_CACHE_DROPOLD -- if a conflicting entry is found, drop it.
2726 *
2727 * TODO: this routine is a hack. It blindly removes the old entry, even if it
2728 * happens to match and it is doing it in an inefficient manner. It was added
2729 * to accommodate NFS which runs into a case where the target for a given name
2730 * may change from under it. Note this does nothing to solve the following
2731 * race: 2 callers of cache_enter_time_flags pass a different target vnode for
2732 * the same [dvp, cnp]. It may be argued that code doing this is broken.
2733 */
2734 void
cache_enter_time_flags(struct vnode * dvp,struct vnode * vp,struct componentname * cnp,struct timespec * tsp,struct timespec * dtsp,int flags)2735 cache_enter_time_flags(struct vnode *dvp, struct vnode *vp, struct componentname *cnp,
2736 struct timespec *tsp, struct timespec *dtsp, int flags)
2737 {
2738
2739 MPASS((flags & ~(VFS_CACHE_DROPOLD)) == 0);
2740
2741 if (flags & VFS_CACHE_DROPOLD)
2742 cache_remove_cnp(dvp, cnp);
2743 cache_enter_time(dvp, vp, cnp, tsp, dtsp);
2744 }
2745
2746 static u_long
cache_roundup_2(u_long val)2747 cache_roundup_2(u_long val)
2748 {
2749 u_long res;
2750
2751 for (res = 1; res <= val; res <<= 1)
2752 continue;
2753
2754 return (res);
2755 }
2756
2757 static struct nchashhead *
nchinittbl(u_long elements,u_long * hashmask)2758 nchinittbl(u_long elements, u_long *hashmask)
2759 {
2760 struct nchashhead *hashtbl;
2761 u_long hashsize, i;
2762
2763 hashsize = cache_roundup_2(elements) / 2;
2764
2765 hashtbl = malloc(hashsize * sizeof(*hashtbl), M_VFSCACHE, M_WAITOK);
2766 for (i = 0; i < hashsize; i++)
2767 CK_SLIST_INIT(&hashtbl[i]);
2768 *hashmask = hashsize - 1;
2769 return (hashtbl);
2770 }
2771
2772 static void
ncfreetbl(struct nchashhead * hashtbl)2773 ncfreetbl(struct nchashhead *hashtbl)
2774 {
2775
2776 free(hashtbl, M_VFSCACHE);
2777 }
2778
2779 /*
2780 * Name cache initialization, from vfs_init() when we are booting
2781 */
2782 static void
nchinit(void * dummy __unused)2783 nchinit(void *dummy __unused)
2784 {
2785 u_int i;
2786
2787 cache_zone_small = uma_zcreate("S VFS Cache", CACHE_ZONE_SMALL_SIZE,
2788 NULL, NULL, NULL, NULL, CACHE_ZONE_ALIGNMENT, UMA_ZONE_ZINIT);
2789 cache_zone_small_ts = uma_zcreate("STS VFS Cache", CACHE_ZONE_SMALL_TS_SIZE,
2790 NULL, NULL, NULL, NULL, CACHE_ZONE_ALIGNMENT, UMA_ZONE_ZINIT);
2791 cache_zone_large = uma_zcreate("L VFS Cache", CACHE_ZONE_LARGE_SIZE,
2792 NULL, NULL, NULL, NULL, CACHE_ZONE_ALIGNMENT, UMA_ZONE_ZINIT);
2793 cache_zone_large_ts = uma_zcreate("LTS VFS Cache", CACHE_ZONE_LARGE_TS_SIZE,
2794 NULL, NULL, NULL, NULL, CACHE_ZONE_ALIGNMENT, UMA_ZONE_ZINIT);
2795
2796 VFS_SMR_ZONE_SET(cache_zone_small);
2797 VFS_SMR_ZONE_SET(cache_zone_small_ts);
2798 VFS_SMR_ZONE_SET(cache_zone_large);
2799 VFS_SMR_ZONE_SET(cache_zone_large_ts);
2800
2801 ncsize = desiredvnodes * ncsizefactor;
2802 cache_recalc_neg_min();
2803 nchashtbl = nchinittbl(ncsize, &nchash);
2804 ncbuckethash = cache_roundup_2(mp_ncpus * mp_ncpus) - 1;
2805 if (ncbuckethash < 7) /* arbitrarily chosen to avoid having one lock */
2806 ncbuckethash = 7;
2807 if (ncbuckethash > nchash)
2808 ncbuckethash = nchash;
2809 bucketlocks = malloc(sizeof(*bucketlocks) * numbucketlocks, M_VFSCACHE,
2810 M_WAITOK | M_ZERO);
2811 for (i = 0; i < numbucketlocks; i++)
2812 mtx_init(&bucketlocks[i], "ncbuc", NULL, MTX_DUPOK | MTX_RECURSE);
2813 ncvnodehash = ncbuckethash;
2814 vnodelocks = malloc(sizeof(*vnodelocks) * numvnodelocks, M_VFSCACHE,
2815 M_WAITOK | M_ZERO);
2816 for (i = 0; i < numvnodelocks; i++)
2817 mtx_init(&vnodelocks[i], "ncvn", NULL, MTX_DUPOK | MTX_RECURSE);
2818
2819 for (i = 0; i < numneglists; i++) {
2820 mtx_init(&neglists[i].nl_evict_lock, "ncnege", NULL, MTX_DEF);
2821 mtx_init(&neglists[i].nl_lock, "ncnegl", NULL, MTX_DEF);
2822 TAILQ_INIT(&neglists[i].nl_list);
2823 TAILQ_INIT(&neglists[i].nl_hotlist);
2824 }
2825 }
2826 SYSINIT(vfs, SI_SUB_VFS, SI_ORDER_SECOND, nchinit, NULL);
2827
2828 void
cache_vnode_init(struct vnode * vp)2829 cache_vnode_init(struct vnode *vp)
2830 {
2831
2832 LIST_INIT(&vp->v_cache_src);
2833 TAILQ_INIT(&vp->v_cache_dst);
2834 vp->v_cache_dd = NULL;
2835 cache_prehash(vp);
2836 }
2837
2838 /*
2839 * Induce transient cache misses for lockless operation in cache_lookup() by
2840 * using a temporary hash table.
2841 *
2842 * This will force a fs lookup.
2843 *
2844 * Synchronisation is done in 2 steps, calling vfs_smr_synchronize each time
2845 * to observe all CPUs not performing the lookup.
2846 */
2847 static void
cache_changesize_set_temp(struct nchashhead * temptbl,u_long temphash)2848 cache_changesize_set_temp(struct nchashhead *temptbl, u_long temphash)
2849 {
2850
2851 MPASS(temphash < nchash);
2852 /*
2853 * Change the size. The new size is smaller and can safely be used
2854 * against the existing table. All lookups which now hash wrong will
2855 * result in a cache miss, which all callers are supposed to know how
2856 * to handle.
2857 */
2858 atomic_store_long(&nchash, temphash);
2859 atomic_thread_fence_rel();
2860 vfs_smr_synchronize();
2861 /*
2862 * At this point everyone sees the updated hash value, but they still
2863 * see the old table.
2864 */
2865 atomic_store_ptr(&nchashtbl, temptbl);
2866 atomic_thread_fence_rel();
2867 vfs_smr_synchronize();
2868 /*
2869 * At this point everyone sees the updated table pointer and size pair.
2870 */
2871 }
2872
2873 /*
2874 * Set the new hash table.
2875 *
2876 * Similarly to cache_changesize_set_temp(), this has to synchronize against
2877 * lockless operation in cache_lookup().
2878 */
2879 static void
cache_changesize_set_new(struct nchashhead * new_tbl,u_long new_hash)2880 cache_changesize_set_new(struct nchashhead *new_tbl, u_long new_hash)
2881 {
2882
2883 MPASS(nchash < new_hash);
2884 /*
2885 * Change the pointer first. This wont result in out of bounds access
2886 * since the temporary table is guaranteed to be smaller.
2887 */
2888 atomic_store_ptr(&nchashtbl, new_tbl);
2889 atomic_thread_fence_rel();
2890 vfs_smr_synchronize();
2891 /*
2892 * At this point everyone sees the updated pointer value, but they
2893 * still see the old size.
2894 */
2895 atomic_store_long(&nchash, new_hash);
2896 atomic_thread_fence_rel();
2897 vfs_smr_synchronize();
2898 /*
2899 * At this point everyone sees the updated table pointer and size pair.
2900 */
2901 }
2902
2903 void
cache_changesize(u_long newmaxvnodes)2904 cache_changesize(u_long newmaxvnodes)
2905 {
2906 struct nchashhead *new_nchashtbl, *old_nchashtbl, *temptbl;
2907 u_long new_nchash, old_nchash, temphash;
2908 struct namecache *ncp;
2909 uint32_t hash;
2910 u_long newncsize;
2911 u_long i;
2912
2913 newncsize = newmaxvnodes * ncsizefactor;
2914 newmaxvnodes = cache_roundup_2(newmaxvnodes * 2);
2915 if (newmaxvnodes < numbucketlocks)
2916 newmaxvnodes = numbucketlocks;
2917
2918 new_nchashtbl = nchinittbl(newmaxvnodes, &new_nchash);
2919 /* If same hash table size, nothing to do */
2920 if (nchash == new_nchash) {
2921 ncfreetbl(new_nchashtbl);
2922 return;
2923 }
2924
2925 temptbl = nchinittbl(1, &temphash);
2926
2927 /*
2928 * Move everything from the old hash table to the new table.
2929 * None of the namecache entries in the table can be removed
2930 * because to do so, they have to be removed from the hash table.
2931 */
2932 cache_lock_all_vnodes();
2933 cache_lock_all_buckets();
2934 old_nchashtbl = nchashtbl;
2935 old_nchash = nchash;
2936 cache_changesize_set_temp(temptbl, temphash);
2937 for (i = 0; i <= old_nchash; i++) {
2938 while ((ncp = CK_SLIST_FIRST(&old_nchashtbl[i])) != NULL) {
2939 hash = cache_get_hash(ncp->nc_name, ncp->nc_nlen,
2940 ncp->nc_dvp);
2941 CK_SLIST_REMOVE(&old_nchashtbl[i], ncp, namecache, nc_hash);
2942 CK_SLIST_INSERT_HEAD(&new_nchashtbl[hash & new_nchash], ncp, nc_hash);
2943 }
2944 }
2945 ncsize = newncsize;
2946 cache_recalc_neg_min();
2947 cache_changesize_set_new(new_nchashtbl, new_nchash);
2948 cache_unlock_all_buckets();
2949 cache_unlock_all_vnodes();
2950 ncfreetbl(old_nchashtbl);
2951 ncfreetbl(temptbl);
2952 }
2953
2954 /*
2955 * Remove all entries from and to a particular vnode.
2956 */
2957 static void
cache_purge_impl(struct vnode * vp)2958 cache_purge_impl(struct vnode *vp)
2959 {
2960 struct cache_freebatch batch;
2961 struct namecache *ncp;
2962 struct mtx *vlp, *vlp2;
2963
2964 TAILQ_INIT(&batch);
2965 vlp = VP2VNODELOCK(vp);
2966 vlp2 = NULL;
2967 mtx_lock(vlp);
2968 retry:
2969 while (!LIST_EMPTY(&vp->v_cache_src)) {
2970 ncp = LIST_FIRST(&vp->v_cache_src);
2971 if (!cache_zap_locked_vnode_kl2(ncp, vp, &vlp2))
2972 goto retry;
2973 TAILQ_INSERT_TAIL(&batch, ncp, nc_dst);
2974 }
2975 while (!TAILQ_EMPTY(&vp->v_cache_dst)) {
2976 ncp = TAILQ_FIRST(&vp->v_cache_dst);
2977 if (!cache_zap_locked_vnode_kl2(ncp, vp, &vlp2))
2978 goto retry;
2979 TAILQ_INSERT_TAIL(&batch, ncp, nc_dst);
2980 }
2981 ncp = vp->v_cache_dd;
2982 if (ncp != NULL) {
2983 KASSERT(ncp->nc_flag & NCF_ISDOTDOT,
2984 ("lost dotdot link"));
2985 if (!cache_zap_locked_vnode_kl2(ncp, vp, &vlp2))
2986 goto retry;
2987 TAILQ_INSERT_TAIL(&batch, ncp, nc_dst);
2988 }
2989 KASSERT(vp->v_cache_dd == NULL, ("incomplete purge"));
2990 mtx_unlock(vlp);
2991 if (vlp2 != NULL)
2992 mtx_unlock(vlp2);
2993 cache_free_batch(&batch);
2994 }
2995
2996 /*
2997 * Opportunistic check to see if there is anything to do.
2998 */
2999 static bool
cache_has_entries(struct vnode * vp)3000 cache_has_entries(struct vnode *vp)
3001 {
3002
3003 if (LIST_EMPTY(&vp->v_cache_src) && TAILQ_EMPTY(&vp->v_cache_dst) &&
3004 atomic_load_ptr(&vp->v_cache_dd) == NULL)
3005 return (false);
3006 return (true);
3007 }
3008
3009 void
cache_purge(struct vnode * vp)3010 cache_purge(struct vnode *vp)
3011 {
3012
3013 SDT_PROBE1(vfs, namecache, purge, done, vp);
3014 if (!cache_has_entries(vp))
3015 return;
3016 cache_purge_impl(vp);
3017 }
3018
3019 /*
3020 * Only to be used by vgone.
3021 */
3022 void
cache_purge_vgone(struct vnode * vp)3023 cache_purge_vgone(struct vnode *vp)
3024 {
3025 struct mtx *vlp;
3026
3027 VNPASS(VN_IS_DOOMED(vp), vp);
3028 if (cache_has_entries(vp)) {
3029 cache_purge_impl(vp);
3030 return;
3031 }
3032
3033 /*
3034 * Serialize against a potential thread doing cache_purge.
3035 */
3036 vlp = VP2VNODELOCK(vp);
3037 mtx_wait_unlocked(vlp);
3038 if (cache_has_entries(vp)) {
3039 cache_purge_impl(vp);
3040 return;
3041 }
3042 return;
3043 }
3044
3045 /*
3046 * Remove all negative entries for a particular directory vnode.
3047 */
3048 void
cache_purge_negative(struct vnode * vp)3049 cache_purge_negative(struct vnode *vp)
3050 {
3051 struct cache_freebatch batch;
3052 struct namecache *ncp, *nnp;
3053 struct mtx *vlp;
3054
3055 SDT_PROBE1(vfs, namecache, purge_negative, done, vp);
3056 if (LIST_EMPTY(&vp->v_cache_src))
3057 return;
3058 TAILQ_INIT(&batch);
3059 vlp = VP2VNODELOCK(vp);
3060 mtx_lock(vlp);
3061 LIST_FOREACH_SAFE(ncp, &vp->v_cache_src, nc_src, nnp) {
3062 if (!(ncp->nc_flag & NCF_NEGATIVE))
3063 continue;
3064 cache_zap_negative_locked_vnode_kl(ncp, vp);
3065 TAILQ_INSERT_TAIL(&batch, ncp, nc_dst);
3066 }
3067 mtx_unlock(vlp);
3068 cache_free_batch(&batch);
3069 }
3070
3071 /*
3072 * Entry points for modifying VOP operations.
3073 */
3074 void
cache_vop_rename(struct vnode * fdvp,struct vnode * fvp,struct vnode * tdvp,struct vnode * tvp,struct componentname * fcnp,struct componentname * tcnp)3075 cache_vop_rename(struct vnode *fdvp, struct vnode *fvp, struct vnode *tdvp,
3076 struct vnode *tvp, struct componentname *fcnp, struct componentname *tcnp)
3077 {
3078
3079 ASSERT_VOP_IN_SEQC(fdvp);
3080 ASSERT_VOP_IN_SEQC(fvp);
3081 ASSERT_VOP_IN_SEQC(tdvp);
3082 if (tvp != NULL)
3083 ASSERT_VOP_IN_SEQC(tvp);
3084
3085 cache_purge(fvp);
3086 if (tvp != NULL) {
3087 cache_purge(tvp);
3088 KASSERT(!cache_remove_cnp(tdvp, tcnp),
3089 ("%s: lingering negative entry", __func__));
3090 } else {
3091 cache_remove_cnp(tdvp, tcnp);
3092 }
3093
3094 /*
3095 * TODO
3096 *
3097 * Historically renaming was always purging all revelang entries,
3098 * but that's quite wasteful. In particular turns out that in many cases
3099 * the target file is immediately accessed after rename, inducing a cache
3100 * miss.
3101 *
3102 * Recode this to reduce relocking and reuse the existing entry (if any)
3103 * instead of just removing it above and allocating a new one here.
3104 */
3105 cache_enter(tdvp, fvp, tcnp);
3106 }
3107
3108 void
cache_vop_rmdir(struct vnode * dvp,struct vnode * vp)3109 cache_vop_rmdir(struct vnode *dvp, struct vnode *vp)
3110 {
3111
3112 ASSERT_VOP_IN_SEQC(dvp);
3113 ASSERT_VOP_IN_SEQC(vp);
3114 cache_purge(vp);
3115 }
3116
3117 #ifdef INVARIANTS
3118 /*
3119 * Validate that if an entry exists it matches.
3120 */
3121 void
cache_validate(struct vnode * dvp,struct vnode * vp,struct componentname * cnp)3122 cache_validate(struct vnode *dvp, struct vnode *vp, struct componentname *cnp)
3123 {
3124 struct namecache *ncp;
3125 struct mtx *blp;
3126 uint32_t hash;
3127
3128 hash = cache_get_hash(cnp->cn_nameptr, cnp->cn_namelen, dvp);
3129 if (CK_SLIST_EMPTY(NCHHASH(hash)))
3130 return;
3131 blp = HASH2BUCKETLOCK(hash);
3132 mtx_lock(blp);
3133 ncp = cache_ncp_find(dvp, cnp, hash);
3134 if (ncp != NULL && ncp->nc_vp != vp) {
3135 panic("%s: mismatch (%p != %p); ncp %p [%s] dvp %p\n",
3136 __func__, vp, ncp->nc_vp, ncp, ncp->nc_name, ncp->nc_dvp);
3137 }
3138 mtx_unlock(blp);
3139 }
3140
3141 void
cache_assert_no_entries(struct vnode * vp)3142 cache_assert_no_entries(struct vnode *vp)
3143 {
3144
3145 VNPASS(TAILQ_EMPTY(&vp->v_cache_dst), vp);
3146 VNPASS(LIST_EMPTY(&vp->v_cache_src), vp);
3147 VNPASS(vp->v_cache_dd == NULL, vp);
3148 }
3149 #endif
3150
3151 /*
3152 * Flush all entries referencing a particular filesystem.
3153 */
3154 void
cache_purgevfs(struct mount * mp)3155 cache_purgevfs(struct mount *mp)
3156 {
3157 struct vnode *vp, *mvp;
3158 size_t visited __sdt_used, purged __sdt_used;
3159
3160 visited = purged = 0;
3161 /*
3162 * Somewhat wasteful iteration over all vnodes. Would be better to
3163 * support filtering and avoid the interlock to begin with.
3164 */
3165 MNT_VNODE_FOREACH_ALL(vp, mp, mvp) {
3166 visited++;
3167 if (!cache_has_entries(vp)) {
3168 VI_UNLOCK(vp);
3169 continue;
3170 }
3171 vholdl(vp);
3172 VI_UNLOCK(vp);
3173 cache_purge(vp);
3174 purged++;
3175 vdrop(vp);
3176 }
3177
3178 SDT_PROBE3(vfs, namecache, purgevfs, done, mp, visited, purged);
3179 }
3180
3181 /*
3182 * Perform canonical checks and cache lookup and pass on to filesystem
3183 * through the vop_cachedlookup only if needed.
3184 */
3185
3186 int
vfs_cache_lookup(struct vop_lookup_args * ap)3187 vfs_cache_lookup(struct vop_lookup_args *ap)
3188 {
3189 struct vnode *dvp;
3190 int error;
3191 struct vnode **vpp = ap->a_vpp;
3192 struct componentname *cnp = ap->a_cnp;
3193 int flags = cnp->cn_flags;
3194
3195 *vpp = NULL;
3196 dvp = ap->a_dvp;
3197
3198 if (dvp->v_type != VDIR)
3199 return (ENOTDIR);
3200
3201 if ((flags & ISLASTCN) && (dvp->v_mount->mnt_flag & MNT_RDONLY) &&
3202 (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME))
3203 return (EROFS);
3204
3205 error = vn_dir_check_exec(dvp, cnp);
3206 if (error != 0)
3207 return (error);
3208
3209 error = cache_lookup(dvp, vpp, cnp, NULL, NULL);
3210 if (error == 0)
3211 return (VOP_CACHEDLOOKUP(dvp, vpp, cnp));
3212 if (error == -1)
3213 return (0);
3214 return (error);
3215 }
3216
3217 /* Implementation of the getcwd syscall. */
3218 int
sys___getcwd(struct thread * td,struct __getcwd_args * uap)3219 sys___getcwd(struct thread *td, struct __getcwd_args *uap)
3220 {
3221 char *buf, *retbuf;
3222 size_t buflen;
3223 int error;
3224
3225 buflen = uap->buflen;
3226 if (__predict_false(buflen < 2))
3227 return (EINVAL);
3228 if (buflen > MAXPATHLEN)
3229 buflen = MAXPATHLEN;
3230
3231 buf = uma_zalloc(namei_zone, M_WAITOK);
3232 error = vn_getcwd(buf, &retbuf, &buflen);
3233 if (error == 0)
3234 error = copyout(retbuf, uap->buf, buflen);
3235 uma_zfree(namei_zone, buf);
3236 return (error);
3237 }
3238
3239 int
vn_getcwd(char * buf,char ** retbuf,size_t * buflen)3240 vn_getcwd(char *buf, char **retbuf, size_t *buflen)
3241 {
3242 struct pwd *pwd;
3243 int error;
3244
3245 vfs_smr_enter();
3246 pwd = pwd_get_smr();
3247 error = vn_fullpath_any_smr(pwd->pwd_cdir, pwd->pwd_rdir, buf, retbuf,
3248 buflen, 0);
3249 VFS_SMR_ASSERT_NOT_ENTERED();
3250 if (error < 0) {
3251 pwd = pwd_hold(curthread);
3252 error = vn_fullpath_any(pwd->pwd_cdir, pwd->pwd_rdir, buf,
3253 retbuf, buflen);
3254 pwd_drop(pwd);
3255 }
3256
3257 #ifdef KTRACE
3258 if (KTRPOINT(curthread, KTR_NAMEI) && error == 0)
3259 ktrnamei(*retbuf);
3260 #endif
3261 return (error);
3262 }
3263
3264 /*
3265 * Canonicalize a path by walking it forward and back.
3266 *
3267 * BUGS:
3268 * - Nothing guarantees the integrity of the entire chain. Consider the case
3269 * where the path "foo/bar/baz/qux" is passed, but "bar" is moved out of
3270 * "foo" into "quux" during the backwards walk. The result will be
3271 * "quux/bar/baz/qux", which could not have been obtained by an incremental
3272 * walk in userspace. Moreover, the path we return is inaccessible if the
3273 * calling thread lacks permission to traverse "quux".
3274 */
3275 static int
kern___realpathat(struct thread * td,int fd,const char * path,char * buf,size_t size,int flags,enum uio_seg pathseg)3276 kern___realpathat(struct thread *td, int fd, const char *path, char *buf,
3277 size_t size, int flags, enum uio_seg pathseg)
3278 {
3279 struct nameidata nd;
3280 char *retbuf, *freebuf;
3281 int error;
3282
3283 if (flags != 0)
3284 return (EINVAL);
3285 NDINIT_ATRIGHTS(&nd, LOOKUP, FOLLOW | WANTPARENT | AUDITVNODE1,
3286 pathseg, path, fd, &cap_fstat_rights);
3287 if ((error = namei(&nd)) != 0)
3288 return (error);
3289
3290 if (nd.ni_vp->v_type == VREG && nd.ni_dvp->v_type != VDIR &&
3291 (nd.ni_vp->v_vflag & VV_ROOT) != 0) {
3292 struct vnode *covered_vp;
3293
3294 /*
3295 * This happens if vp is a file mount. The call to
3296 * vn_fullpath_hardlink can panic if path resolution can't be
3297 * handled without the directory.
3298 *
3299 * To resolve this, we find the vnode which was mounted on -
3300 * this should have a unique global path since we disallow
3301 * mounting on linked files.
3302 */
3303 error = vn_lock(nd.ni_vp, LK_SHARED);
3304 if (error != 0)
3305 goto out;
3306 covered_vp = nd.ni_vp->v_mount->mnt_vnodecovered;
3307 vref(covered_vp);
3308 VOP_UNLOCK(nd.ni_vp);
3309 error = vn_fullpath(covered_vp, &retbuf, &freebuf);
3310 vrele(covered_vp);
3311 } else {
3312 error = vn_fullpath_hardlink(nd.ni_vp, nd.ni_dvp,
3313 nd.ni_cnd.cn_nameptr, nd.ni_cnd.cn_namelen, &retbuf,
3314 &freebuf, &size);
3315 }
3316 if (error == 0) {
3317 size_t len;
3318
3319 len = strlen(retbuf) + 1;
3320 if (size < len)
3321 error = ENAMETOOLONG;
3322 else if (pathseg == UIO_USERSPACE)
3323 error = copyout(retbuf, buf, len);
3324 else
3325 memcpy(buf, retbuf, len);
3326 free(freebuf, M_TEMP);
3327 }
3328 out:
3329 vrele(nd.ni_vp);
3330 vrele(nd.ni_dvp);
3331 NDFREE_PNBUF(&nd);
3332 return (error);
3333 }
3334
3335 int
sys___realpathat(struct thread * td,struct __realpathat_args * uap)3336 sys___realpathat(struct thread *td, struct __realpathat_args *uap)
3337 {
3338
3339 return (kern___realpathat(td, uap->fd, uap->path, uap->buf, uap->size,
3340 uap->flags, UIO_USERSPACE));
3341 }
3342
3343 /*
3344 * Retrieve the full filesystem path that correspond to a vnode from the name
3345 * cache (if available)
3346 */
3347 int
vn_fullpath(struct vnode * vp,char ** retbuf,char ** freebuf)3348 vn_fullpath(struct vnode *vp, char **retbuf, char **freebuf)
3349 {
3350 struct pwd *pwd;
3351 char *buf;
3352 size_t buflen;
3353 int error;
3354
3355 if (__predict_false(vp == NULL))
3356 return (EINVAL);
3357
3358 buflen = MAXPATHLEN;
3359 buf = malloc(buflen, M_TEMP, M_WAITOK);
3360 vfs_smr_enter();
3361 pwd = pwd_get_smr();
3362 error = vn_fullpath_any_smr(vp, pwd->pwd_rdir, buf, retbuf, &buflen, 0);
3363 VFS_SMR_ASSERT_NOT_ENTERED();
3364 if (error < 0) {
3365 pwd = pwd_hold(curthread);
3366 error = vn_fullpath_any(vp, pwd->pwd_rdir, buf, retbuf, &buflen);
3367 pwd_drop(pwd);
3368 }
3369 if (error == 0)
3370 *freebuf = buf;
3371 else
3372 free(buf, M_TEMP);
3373 return (error);
3374 }
3375
3376 /*
3377 * This function is similar to vn_fullpath, but it attempts to lookup the
3378 * pathname relative to the global root mount point. This is required for the
3379 * auditing sub-system, as audited pathnames must be absolute, relative to the
3380 * global root mount point.
3381 */
3382 int
vn_fullpath_global(struct vnode * vp,char ** retbuf,char ** freebuf)3383 vn_fullpath_global(struct vnode *vp, char **retbuf, char **freebuf)
3384 {
3385 char *buf;
3386 size_t buflen;
3387 int error;
3388
3389 if (__predict_false(vp == NULL))
3390 return (EINVAL);
3391 buflen = MAXPATHLEN;
3392 buf = malloc(buflen, M_TEMP, M_WAITOK);
3393 vfs_smr_enter();
3394 error = vn_fullpath_any_smr(vp, rootvnode, buf, retbuf, &buflen, 0);
3395 VFS_SMR_ASSERT_NOT_ENTERED();
3396 if (error < 0) {
3397 error = vn_fullpath_any(vp, rootvnode, buf, retbuf, &buflen);
3398 }
3399 if (error == 0)
3400 *freebuf = buf;
3401 else
3402 free(buf, M_TEMP);
3403 return (error);
3404 }
3405
3406 static struct namecache *
vn_dd_from_dst(struct vnode * vp)3407 vn_dd_from_dst(struct vnode *vp)
3408 {
3409 struct namecache *ncp;
3410
3411 cache_assert_vnode_locked(vp);
3412 TAILQ_FOREACH(ncp, &vp->v_cache_dst, nc_dst) {
3413 if ((ncp->nc_flag & NCF_ISDOTDOT) == 0)
3414 return (ncp);
3415 }
3416 return (NULL);
3417 }
3418
3419 int
vn_vptocnp(struct vnode ** vp,char * buf,size_t * buflen)3420 vn_vptocnp(struct vnode **vp, char *buf, size_t *buflen)
3421 {
3422 struct vnode *dvp;
3423 struct namecache *ncp;
3424 struct mtx *vlp;
3425 int error;
3426
3427 vlp = VP2VNODELOCK(*vp);
3428 mtx_lock(vlp);
3429 ncp = (*vp)->v_cache_dd;
3430 if (ncp != NULL && (ncp->nc_flag & NCF_ISDOTDOT) == 0) {
3431 KASSERT(ncp == vn_dd_from_dst(*vp),
3432 ("%s: mismatch for dd entry (%p != %p)", __func__,
3433 ncp, vn_dd_from_dst(*vp)));
3434 } else {
3435 ncp = vn_dd_from_dst(*vp);
3436 }
3437 if (ncp != NULL) {
3438 if (*buflen < ncp->nc_nlen) {
3439 mtx_unlock(vlp);
3440 vrele(*vp);
3441 counter_u64_add(numfullpathfail4, 1);
3442 error = ENOMEM;
3443 SDT_PROBE3(vfs, namecache, fullpath, return, error,
3444 vp, NULL);
3445 return (error);
3446 }
3447 *buflen -= ncp->nc_nlen;
3448 memcpy(buf + *buflen, ncp->nc_name, ncp->nc_nlen);
3449 SDT_PROBE3(vfs, namecache, fullpath, hit, ncp->nc_dvp,
3450 ncp->nc_name, vp);
3451 dvp = *vp;
3452 *vp = ncp->nc_dvp;
3453 vref(*vp);
3454 mtx_unlock(vlp);
3455 vrele(dvp);
3456 return (0);
3457 }
3458 SDT_PROBE1(vfs, namecache, fullpath, miss, vp);
3459
3460 mtx_unlock(vlp);
3461 vn_lock(*vp, LK_SHARED | LK_RETRY);
3462 error = VOP_VPTOCNP(*vp, &dvp, buf, buflen);
3463 vput(*vp);
3464 if (error) {
3465 counter_u64_add(numfullpathfail2, 1);
3466 SDT_PROBE3(vfs, namecache, fullpath, return, error, vp, NULL);
3467 return (error);
3468 }
3469
3470 *vp = dvp;
3471 if (VN_IS_DOOMED(dvp)) {
3472 /* forced unmount */
3473 vrele(dvp);
3474 error = ENOENT;
3475 SDT_PROBE3(vfs, namecache, fullpath, return, error, vp, NULL);
3476 return (error);
3477 }
3478 /*
3479 * *vp has its use count incremented still.
3480 */
3481
3482 return (0);
3483 }
3484
3485 /*
3486 * Resolve a directory to a pathname.
3487 *
3488 * The name of the directory can always be found in the namecache or fetched
3489 * from the filesystem. There is also guaranteed to be only one parent, meaning
3490 * we can just follow vnodes up until we find the root.
3491 *
3492 * The vnode must be referenced.
3493 */
3494 static int
vn_fullpath_dir(struct vnode * vp,struct vnode * rdir,char * buf,char ** retbuf,size_t * len,size_t addend)3495 vn_fullpath_dir(struct vnode *vp, struct vnode *rdir, char *buf, char **retbuf,
3496 size_t *len, size_t addend)
3497 {
3498 #ifdef KDTRACE_HOOKS
3499 struct vnode *startvp = vp;
3500 #endif
3501 struct vnode *vp1;
3502 size_t buflen;
3503 int error;
3504 bool slash_prefixed;
3505
3506 VNPASS(vp->v_type == VDIR || VN_IS_DOOMED(vp), vp);
3507 VNPASS(vp->v_usecount > 0, vp);
3508
3509 buflen = *len;
3510
3511 slash_prefixed = true;
3512 if (addend == 0) {
3513 MPASS(*len >= 2);
3514 buflen--;
3515 buf[buflen] = '\0';
3516 slash_prefixed = false;
3517 }
3518
3519 error = 0;
3520
3521 SDT_PROBE1(vfs, namecache, fullpath, entry, vp);
3522 counter_u64_add(numfullpathcalls, 1);
3523 while (vp != rdir && vp != rootvnode) {
3524 /*
3525 * The vp vnode must be already fully constructed,
3526 * since it is either found in namecache or obtained
3527 * from VOP_VPTOCNP(). We may test for VV_ROOT safely
3528 * without obtaining the vnode lock.
3529 */
3530 if ((vp->v_vflag & VV_ROOT) != 0) {
3531 vn_lock(vp, LK_RETRY | LK_SHARED);
3532
3533 /*
3534 * With the vnode locked, check for races with
3535 * unmount, forced or not. Note that we
3536 * already verified that vp is not equal to
3537 * the root vnode, which means that
3538 * mnt_vnodecovered can be NULL only for the
3539 * case of unmount.
3540 */
3541 if (VN_IS_DOOMED(vp) ||
3542 (vp1 = vp->v_mount->mnt_vnodecovered) == NULL ||
3543 vp1->v_mountedhere != vp->v_mount) {
3544 vput(vp);
3545 error = ENOENT;
3546 SDT_PROBE3(vfs, namecache, fullpath, return,
3547 error, vp, NULL);
3548 break;
3549 }
3550
3551 vref(vp1);
3552 vput(vp);
3553 vp = vp1;
3554 continue;
3555 }
3556 VNPASS(vp->v_type == VDIR || VN_IS_DOOMED(vp), vp);
3557 error = vn_vptocnp(&vp, buf, &buflen);
3558 if (error)
3559 break;
3560 if (buflen == 0) {
3561 vrele(vp);
3562 error = ENOMEM;
3563 SDT_PROBE3(vfs, namecache, fullpath, return, error,
3564 startvp, NULL);
3565 break;
3566 }
3567 buf[--buflen] = '/';
3568 slash_prefixed = true;
3569 }
3570 if (error)
3571 return (error);
3572 if (!slash_prefixed) {
3573 if (buflen == 0) {
3574 vrele(vp);
3575 counter_u64_add(numfullpathfail4, 1);
3576 SDT_PROBE3(vfs, namecache, fullpath, return, ENOMEM,
3577 startvp, NULL);
3578 return (ENOMEM);
3579 }
3580 buf[--buflen] = '/';
3581 }
3582 counter_u64_add(numfullpathfound, 1);
3583 vrele(vp);
3584
3585 *retbuf = buf + buflen;
3586 SDT_PROBE3(vfs, namecache, fullpath, return, 0, startvp, *retbuf);
3587 *len -= buflen;
3588 *len += addend;
3589 return (0);
3590 }
3591
3592 /*
3593 * Resolve an arbitrary vnode to a pathname.
3594 *
3595 * Note 2 caveats:
3596 * - hardlinks are not tracked, thus if the vnode is not a directory this can
3597 * resolve to a different path than the one used to find it
3598 * - namecache is not mandatory, meaning names are not guaranteed to be added
3599 * (in which case resolving fails)
3600 */
3601 static void __inline
cache_rev_failed_impl(int * reason,int line)3602 cache_rev_failed_impl(int *reason, int line)
3603 {
3604
3605 *reason = line;
3606 }
3607 #define cache_rev_failed(var) cache_rev_failed_impl((var), __LINE__)
3608
3609 static int
vn_fullpath_any_smr(struct vnode * vp,struct vnode * rdir,char * buf,char ** retbuf,size_t * buflen,size_t addend)3610 vn_fullpath_any_smr(struct vnode *vp, struct vnode *rdir, char *buf,
3611 char **retbuf, size_t *buflen, size_t addend)
3612 {
3613 #ifdef KDTRACE_HOOKS
3614 struct vnode *startvp = vp;
3615 #endif
3616 struct vnode *tvp;
3617 struct mount *mp;
3618 struct namecache *ncp;
3619 size_t orig_buflen;
3620 int reason;
3621 int error;
3622 #ifdef KDTRACE_HOOKS
3623 int i;
3624 #endif
3625 seqc_t vp_seqc, tvp_seqc;
3626 u_char nc_flag;
3627
3628 VFS_SMR_ASSERT_ENTERED();
3629
3630 if (!atomic_load_char(&cache_fast_lookup_enabled)) {
3631 vfs_smr_exit();
3632 return (-1);
3633 }
3634
3635 orig_buflen = *buflen;
3636
3637 if (addend == 0) {
3638 MPASS(*buflen >= 2);
3639 *buflen -= 1;
3640 buf[*buflen] = '\0';
3641 }
3642
3643 if (vp == rdir || vp == rootvnode) {
3644 if (addend == 0) {
3645 *buflen -= 1;
3646 buf[*buflen] = '/';
3647 }
3648 goto out_ok;
3649 }
3650
3651 #ifdef KDTRACE_HOOKS
3652 i = 0;
3653 #endif
3654 error = -1;
3655 ncp = NULL; /* for sdt probe down below */
3656 vp_seqc = vn_seqc_read_any(vp);
3657 if (seqc_in_modify(vp_seqc)) {
3658 cache_rev_failed(&reason);
3659 goto out_abort;
3660 }
3661
3662 for (;;) {
3663 #ifdef KDTRACE_HOOKS
3664 i++;
3665 #endif
3666 if ((vp->v_vflag & VV_ROOT) != 0) {
3667 mp = atomic_load_ptr(&vp->v_mount);
3668 if (mp == NULL) {
3669 cache_rev_failed(&reason);
3670 goto out_abort;
3671 }
3672 tvp = atomic_load_ptr(&mp->mnt_vnodecovered);
3673 tvp_seqc = vn_seqc_read_any(tvp);
3674 if (seqc_in_modify(tvp_seqc)) {
3675 cache_rev_failed(&reason);
3676 goto out_abort;
3677 }
3678 if (!vn_seqc_consistent(vp, vp_seqc)) {
3679 cache_rev_failed(&reason);
3680 goto out_abort;
3681 }
3682 vp = tvp;
3683 vp_seqc = tvp_seqc;
3684 continue;
3685 }
3686 ncp = atomic_load_consume_ptr(&vp->v_cache_dd);
3687 if (ncp == NULL) {
3688 cache_rev_failed(&reason);
3689 goto out_abort;
3690 }
3691 nc_flag = atomic_load_char(&ncp->nc_flag);
3692 if ((nc_flag & NCF_ISDOTDOT) != 0) {
3693 cache_rev_failed(&reason);
3694 goto out_abort;
3695 }
3696 if (ncp->nc_nlen >= *buflen) {
3697 cache_rev_failed(&reason);
3698 error = ENOMEM;
3699 goto out_abort;
3700 }
3701 *buflen -= ncp->nc_nlen;
3702 memcpy(buf + *buflen, ncp->nc_name, ncp->nc_nlen);
3703 *buflen -= 1;
3704 buf[*buflen] = '/';
3705 tvp = ncp->nc_dvp;
3706 tvp_seqc = vn_seqc_read_any(tvp);
3707 if (seqc_in_modify(tvp_seqc)) {
3708 cache_rev_failed(&reason);
3709 goto out_abort;
3710 }
3711 if (!vn_seqc_consistent(vp, vp_seqc)) {
3712 cache_rev_failed(&reason);
3713 goto out_abort;
3714 }
3715 /*
3716 * Acquire fence provided by vn_seqc_read_any above.
3717 */
3718 if (__predict_false(atomic_load_ptr(&vp->v_cache_dd) != ncp)) {
3719 cache_rev_failed(&reason);
3720 goto out_abort;
3721 }
3722 if (!cache_ncp_canuse(ncp)) {
3723 cache_rev_failed(&reason);
3724 goto out_abort;
3725 }
3726 vp = tvp;
3727 vp_seqc = tvp_seqc;
3728 if (vp == rdir || vp == rootvnode)
3729 break;
3730 }
3731 out_ok:
3732 vfs_smr_exit();
3733 *retbuf = buf + *buflen;
3734 *buflen = orig_buflen - *buflen + addend;
3735 SDT_PROBE2(vfs, namecache, fullpath_smr, hit, startvp, *retbuf);
3736 return (0);
3737
3738 out_abort:
3739 *buflen = orig_buflen;
3740 SDT_PROBE4(vfs, namecache, fullpath_smr, miss, startvp, ncp, reason, i);
3741 vfs_smr_exit();
3742 return (error);
3743 }
3744
3745 static int
vn_fullpath_any(struct vnode * vp,struct vnode * rdir,char * buf,char ** retbuf,size_t * buflen)3746 vn_fullpath_any(struct vnode *vp, struct vnode *rdir, char *buf, char **retbuf,
3747 size_t *buflen)
3748 {
3749 size_t orig_buflen, addend;
3750 int error;
3751
3752 if (*buflen < 2)
3753 return (EINVAL);
3754
3755 orig_buflen = *buflen;
3756
3757 vref(vp);
3758 addend = 0;
3759 if (vp->v_type != VDIR) {
3760 *buflen -= 1;
3761 buf[*buflen] = '\0';
3762 error = vn_vptocnp(&vp, buf, buflen);
3763 if (error)
3764 return (error);
3765 if (*buflen == 0) {
3766 vrele(vp);
3767 return (ENOMEM);
3768 }
3769 *buflen -= 1;
3770 buf[*buflen] = '/';
3771 addend = orig_buflen - *buflen;
3772 }
3773
3774 return (vn_fullpath_dir(vp, rdir, buf, retbuf, buflen, addend));
3775 }
3776
3777 /*
3778 * Resolve an arbitrary vnode to a pathname (taking care of hardlinks).
3779 *
3780 * Since the namecache does not track hardlinks, the caller is expected to
3781 * first look up the target vnode with WANTPARENT flag passed to namei to get
3782 * dvp and vp.
3783 *
3784 * Then we have 2 cases:
3785 * - if the found vnode is a directory, the path can be constructed just by
3786 * following names up the chain
3787 * - otherwise we populate the buffer with the saved name and start resolving
3788 * from the parent
3789 */
3790 int
vn_fullpath_hardlink(struct vnode * vp,struct vnode * dvp,const char * hrdl_name,size_t hrdl_name_length,char ** retbuf,char ** freebuf,size_t * buflen)3791 vn_fullpath_hardlink(struct vnode *vp, struct vnode *dvp,
3792 const char *hrdl_name, size_t hrdl_name_length,
3793 char **retbuf, char **freebuf, size_t *buflen)
3794 {
3795 char *buf, *tmpbuf;
3796 struct pwd *pwd;
3797 size_t addend;
3798 int error;
3799 __enum_uint8(vtype) type;
3800
3801 if (*buflen < 2)
3802 return (EINVAL);
3803 if (*buflen > MAXPATHLEN)
3804 *buflen = MAXPATHLEN;
3805
3806 buf = malloc(*buflen, M_TEMP, M_WAITOK);
3807
3808 addend = 0;
3809
3810 /*
3811 * Check for VBAD to work around the vp_crossmp bug in lookup().
3812 *
3813 * For example consider tmpfs on /tmp and realpath /tmp. ni_vp will be
3814 * set to mount point's root vnode while ni_dvp will be vp_crossmp.
3815 * If the type is VDIR (like in this very case) we can skip looking
3816 * at ni_dvp in the first place. However, since vnodes get passed here
3817 * unlocked the target may transition to doomed state (type == VBAD)
3818 * before we get to evaluate the condition. If this happens, we will
3819 * populate part of the buffer and descend to vn_fullpath_dir with
3820 * vp == vp_crossmp. Prevent the problem by checking for VBAD.
3821 */
3822 type = atomic_load_8(&vp->v_type);
3823 if (type == VBAD) {
3824 error = ENOENT;
3825 goto out_bad;
3826 }
3827 if (type != VDIR) {
3828 addend = hrdl_name_length + 2;
3829 if (*buflen < addend) {
3830 error = ENOMEM;
3831 goto out_bad;
3832 }
3833 *buflen -= addend;
3834 tmpbuf = buf + *buflen;
3835 tmpbuf[0] = '/';
3836 memcpy(&tmpbuf[1], hrdl_name, hrdl_name_length);
3837 tmpbuf[addend - 1] = '\0';
3838 vp = dvp;
3839 }
3840
3841 vfs_smr_enter();
3842 pwd = pwd_get_smr();
3843 error = vn_fullpath_any_smr(vp, pwd->pwd_rdir, buf, retbuf, buflen,
3844 addend);
3845 VFS_SMR_ASSERT_NOT_ENTERED();
3846 if (error < 0) {
3847 pwd = pwd_hold(curthread);
3848 vref(vp);
3849 error = vn_fullpath_dir(vp, pwd->pwd_rdir, buf, retbuf, buflen,
3850 addend);
3851 pwd_drop(pwd);
3852 }
3853 if (error != 0)
3854 goto out_bad;
3855
3856 *freebuf = buf;
3857
3858 return (0);
3859 out_bad:
3860 free(buf, M_TEMP);
3861 return (error);
3862 }
3863
3864 struct vnode *
vn_dir_dd_ino(struct vnode * vp)3865 vn_dir_dd_ino(struct vnode *vp)
3866 {
3867 struct namecache *ncp;
3868 struct vnode *ddvp;
3869 struct mtx *vlp;
3870 enum vgetstate vs;
3871
3872 ASSERT_VOP_LOCKED(vp, "vn_dir_dd_ino");
3873 vlp = VP2VNODELOCK(vp);
3874 mtx_lock(vlp);
3875 TAILQ_FOREACH(ncp, &(vp->v_cache_dst), nc_dst) {
3876 if ((ncp->nc_flag & NCF_ISDOTDOT) != 0)
3877 continue;
3878 ddvp = ncp->nc_dvp;
3879 vs = vget_prep(ddvp);
3880 mtx_unlock(vlp);
3881 if (vget_finish(ddvp, LK_SHARED | LK_NOWAIT, vs))
3882 return (NULL);
3883 return (ddvp);
3884 }
3885 mtx_unlock(vlp);
3886 return (NULL);
3887 }
3888
3889 int
vn_commname(struct vnode * vp,char * buf,u_int buflen)3890 vn_commname(struct vnode *vp, char *buf, u_int buflen)
3891 {
3892 struct namecache *ncp;
3893 struct mtx *vlp;
3894 int l;
3895
3896 vlp = VP2VNODELOCK(vp);
3897 mtx_lock(vlp);
3898 TAILQ_FOREACH(ncp, &vp->v_cache_dst, nc_dst)
3899 if ((ncp->nc_flag & NCF_ISDOTDOT) == 0)
3900 break;
3901 if (ncp == NULL) {
3902 mtx_unlock(vlp);
3903 return (ENOENT);
3904 }
3905 l = min(ncp->nc_nlen, buflen - 1);
3906 memcpy(buf, ncp->nc_name, l);
3907 mtx_unlock(vlp);
3908 buf[l] = '\0';
3909 return (0);
3910 }
3911
3912 /*
3913 * This function updates path string to vnode's full global path
3914 * and checks the size of the new path string against the pathlen argument.
3915 *
3916 * Requires a locked, referenced vnode.
3917 * Vnode is re-locked on success or ENODEV, otherwise unlocked.
3918 *
3919 * If vp is a directory, the call to vn_fullpath_global() always succeeds
3920 * because it falls back to the ".." lookup if the namecache lookup fails.
3921 */
3922 int
vn_path_to_global_path(struct thread * td,struct vnode * vp,char * path,u_int pathlen)3923 vn_path_to_global_path(struct thread *td, struct vnode *vp, char *path,
3924 u_int pathlen)
3925 {
3926 struct nameidata nd;
3927 struct vnode *vp1;
3928 char *rpath, *fbuf;
3929 int error;
3930
3931 ASSERT_VOP_ELOCKED(vp, __func__);
3932
3933 /* Construct global filesystem path from vp. */
3934 VOP_UNLOCK(vp);
3935 error = vn_fullpath_global(vp, &rpath, &fbuf);
3936
3937 if (error != 0) {
3938 vrele(vp);
3939 return (error);
3940 }
3941
3942 if (strlen(rpath) >= pathlen) {
3943 vrele(vp);
3944 error = ENAMETOOLONG;
3945 goto out;
3946 }
3947
3948 /*
3949 * Re-lookup the vnode by path to detect a possible rename.
3950 * As a side effect, the vnode is relocked.
3951 * If vnode was renamed, return ENOENT.
3952 */
3953 NDINIT(&nd, LOOKUP, FOLLOW | LOCKLEAF | AUDITVNODE1, UIO_SYSSPACE, path);
3954 error = namei(&nd);
3955 if (error != 0) {
3956 vrele(vp);
3957 goto out;
3958 }
3959 NDFREE_PNBUF(&nd);
3960 vp1 = nd.ni_vp;
3961 vrele(vp);
3962 if (vp1 == vp)
3963 strcpy(path, rpath);
3964 else {
3965 vput(vp1);
3966 error = ENOENT;
3967 }
3968
3969 out:
3970 free(fbuf, M_TEMP);
3971 return (error);
3972 }
3973
3974 /*
3975 * This is similar to vn_path_to_global_path but allows for regular
3976 * files which may not be present in the cache.
3977 *
3978 * Requires a locked, referenced vnode.
3979 * Vnode is re-locked on success or ENODEV, otherwise unlocked.
3980 */
3981 int
vn_path_to_global_path_hardlink(struct thread * td,struct vnode * vp,struct vnode * dvp,char * path,u_int pathlen,const char * leaf_name,size_t leaf_length)3982 vn_path_to_global_path_hardlink(struct thread *td, struct vnode *vp,
3983 struct vnode *dvp, char *path, u_int pathlen, const char *leaf_name,
3984 size_t leaf_length)
3985 {
3986 struct nameidata nd;
3987 struct vnode *vp1;
3988 char *rpath, *fbuf;
3989 size_t len;
3990 int error;
3991
3992 ASSERT_VOP_ELOCKED(vp, __func__);
3993
3994 /*
3995 * Construct global filesystem path from dvp, vp and leaf
3996 * name.
3997 */
3998 VOP_UNLOCK(vp);
3999 len = pathlen;
4000 error = vn_fullpath_hardlink(vp, dvp, leaf_name, leaf_length,
4001 &rpath, &fbuf, &len);
4002
4003 if (error != 0) {
4004 vrele(vp);
4005 return (error);
4006 }
4007
4008 if (strlen(rpath) >= pathlen) {
4009 vrele(vp);
4010 error = ENAMETOOLONG;
4011 goto out;
4012 }
4013
4014 /*
4015 * Re-lookup the vnode by path to detect a possible rename.
4016 * As a side effect, the vnode is relocked.
4017 * If vnode was renamed, return ENOENT.
4018 */
4019 NDINIT(&nd, LOOKUP, FOLLOW | LOCKLEAF | AUDITVNODE1, UIO_SYSSPACE, path);
4020 error = namei(&nd);
4021 if (error != 0) {
4022 vrele(vp);
4023 goto out;
4024 }
4025 NDFREE_PNBUF(&nd);
4026 vp1 = nd.ni_vp;
4027 vrele(vp);
4028 if (vp1 == vp)
4029 strcpy(path, rpath);
4030 else {
4031 vput(vp1);
4032 error = ENOENT;
4033 }
4034
4035 out:
4036 free(fbuf, M_TEMP);
4037 return (error);
4038 }
4039
4040 void
cache_vop_inotify(struct vnode * vp,int event,uint32_t cookie)4041 cache_vop_inotify(struct vnode *vp, int event, uint32_t cookie)
4042 {
4043 struct mtx *vlp;
4044 struct namecache *ncp;
4045 int isdir;
4046 bool logged, self;
4047
4048 isdir = vp->v_type == VDIR ? IN_ISDIR : 0;
4049 self = (vn_irflag_read(vp) & VIRF_INOTIFY) != 0 &&
4050 (vp->v_type != VDIR || (event & ~_IN_DIR_EVENTS) != 0);
4051
4052 if (self) {
4053 int selfevent;
4054
4055 if (event == _IN_ATTRIB_LINKCOUNT)
4056 selfevent = IN_ATTRIB;
4057 else
4058 selfevent = event;
4059 inotify_log(vp, NULL, 0, selfevent | isdir, cookie);
4060 }
4061 if ((event & IN_ALL_EVENTS) == 0)
4062 return;
4063
4064 logged = false;
4065 vlp = VP2VNODELOCK(vp);
4066 mtx_lock(vlp);
4067 TAILQ_FOREACH(ncp, &vp->v_cache_dst, nc_dst) {
4068 if ((ncp->nc_flag & NCF_ISDOTDOT) != 0)
4069 continue;
4070 if ((vn_irflag_read(ncp->nc_dvp) & VIRF_INOTIFY) != 0) {
4071 /*
4072 * XXX-MJ if the vnode has two links in the same
4073 * dir, we'll log the same event twice.
4074 */
4075 inotify_log(ncp->nc_dvp, ncp->nc_name, ncp->nc_nlen,
4076 event | isdir, cookie);
4077 logged = true;
4078 }
4079 }
4080 if (!logged && (vn_irflag_read(vp) & VIRF_INOTIFY_PARENT) != 0) {
4081 /*
4082 * We didn't find a watched directory that contains this vnode,
4083 * so stop calling VOP_INOTIFY for operations on the vnode.
4084 */
4085 vn_irflag_unset(vp, VIRF_INOTIFY_PARENT);
4086 }
4087 mtx_unlock(vlp);
4088 }
4089
4090 #ifdef DDB
4091 static void
db_print_vpath(struct vnode * vp)4092 db_print_vpath(struct vnode *vp)
4093 {
4094
4095 while (vp != NULL) {
4096 db_printf("%p: ", vp);
4097 if (vp == rootvnode) {
4098 db_printf("/");
4099 vp = NULL;
4100 } else {
4101 if (vp->v_vflag & VV_ROOT) {
4102 db_printf("<mount point>");
4103 vp = vp->v_mount->mnt_vnodecovered;
4104 } else {
4105 struct namecache *ncp;
4106 char *ncn;
4107 int i;
4108
4109 ncp = TAILQ_FIRST(&vp->v_cache_dst);
4110 if (ncp != NULL) {
4111 ncn = ncp->nc_name;
4112 for (i = 0; i < ncp->nc_nlen; i++)
4113 db_printf("%c", *ncn++);
4114 vp = ncp->nc_dvp;
4115 } else {
4116 vp = NULL;
4117 }
4118 }
4119 }
4120 db_printf("\n");
4121 }
4122
4123 return;
4124 }
4125
DB_SHOW_COMMAND(vpath,db_show_vpath)4126 DB_SHOW_COMMAND(vpath, db_show_vpath)
4127 {
4128 struct vnode *vp;
4129
4130 if (!have_addr) {
4131 db_printf("usage: show vpath <struct vnode *>\n");
4132 return;
4133 }
4134
4135 vp = (struct vnode *)addr;
4136 db_print_vpath(vp);
4137 }
4138
4139 #endif
4140
4141 static int cache_fast_lookup = 1;
4142
4143 #define CACHE_FPL_FAILED -2020
4144
4145 static int
cache_vop_bad_vexec(struct vop_fplookup_vexec_args * v)4146 cache_vop_bad_vexec(struct vop_fplookup_vexec_args *v)
4147 {
4148 vn_printf(v->a_vp, "no proper vop_fplookup_vexec\n");
4149 panic("no proper vop_fplookup_vexec");
4150 }
4151
4152 static int
cache_vop_bad_symlink(struct vop_fplookup_symlink_args * v)4153 cache_vop_bad_symlink(struct vop_fplookup_symlink_args *v)
4154 {
4155 vn_printf(v->a_vp, "no proper vop_fplookup_symlink\n");
4156 panic("no proper vop_fplookup_symlink");
4157 }
4158
4159 void
cache_vop_vector_register(struct vop_vector * v)4160 cache_vop_vector_register(struct vop_vector *v)
4161 {
4162 size_t ops;
4163
4164 ops = 0;
4165 if (v->vop_fplookup_vexec != NULL) {
4166 ops++;
4167 }
4168 if (v->vop_fplookup_symlink != NULL) {
4169 ops++;
4170 }
4171
4172 if (ops == 2) {
4173 return;
4174 }
4175
4176 if (ops == 0) {
4177 v->vop_fplookup_vexec = cache_vop_bad_vexec;
4178 v->vop_fplookup_symlink = cache_vop_bad_symlink;
4179 return;
4180 }
4181
4182 printf("%s: invalid vop vector %p -- either all or none fplookup vops "
4183 "need to be provided", __func__, v);
4184 if (v->vop_fplookup_vexec == NULL) {
4185 printf("%s: missing vop_fplookup_vexec\n", __func__);
4186 }
4187 if (v->vop_fplookup_symlink == NULL) {
4188 printf("%s: missing vop_fplookup_symlink\n", __func__);
4189 }
4190 panic("bad vop vector %p", v);
4191 }
4192
4193 #ifdef INVARIANTS
4194 void
cache_validate_vop_vector(struct mount * mp,struct vop_vector * vops)4195 cache_validate_vop_vector(struct mount *mp, struct vop_vector *vops)
4196 {
4197 if (mp == NULL)
4198 return;
4199
4200 if ((mp->mnt_kern_flag & MNTK_FPLOOKUP) == 0)
4201 return;
4202
4203 if (vops->vop_fplookup_vexec == NULL ||
4204 vops->vop_fplookup_vexec == cache_vop_bad_vexec)
4205 panic("bad vop_fplookup_vexec on vector %p for filesystem %s",
4206 vops, mp->mnt_vfc->vfc_name);
4207
4208 if (vops->vop_fplookup_symlink == NULL ||
4209 vops->vop_fplookup_symlink == cache_vop_bad_symlink)
4210 panic("bad vop_fplookup_symlink on vector %p for filesystem %s",
4211 vops, mp->mnt_vfc->vfc_name);
4212 }
4213 #endif
4214
4215 void
cache_fast_lookup_enabled_recalc(void)4216 cache_fast_lookup_enabled_recalc(void)
4217 {
4218 int lookup_flag;
4219 int mac_on;
4220
4221 #ifdef MAC
4222 mac_on = mac_vnode_check_lookup_enabled();
4223 mac_on |= mac_vnode_check_readlink_enabled();
4224 #else
4225 mac_on = 0;
4226 #endif
4227
4228 lookup_flag = atomic_load_int(&cache_fast_lookup);
4229 if (lookup_flag && !mac_on) {
4230 atomic_store_char(&cache_fast_lookup_enabled, true);
4231 } else {
4232 atomic_store_char(&cache_fast_lookup_enabled, false);
4233 }
4234 }
4235
4236 static int
syscal_vfs_cache_fast_lookup(SYSCTL_HANDLER_ARGS)4237 syscal_vfs_cache_fast_lookup(SYSCTL_HANDLER_ARGS)
4238 {
4239 int error, old;
4240
4241 old = atomic_load_int(&cache_fast_lookup);
4242 error = sysctl_handle_int(oidp, arg1, arg2, req);
4243 if (error == 0 && req->newptr && old != atomic_load_int(&cache_fast_lookup))
4244 cache_fast_lookup_enabled_recalc();
4245 return (error);
4246 }
4247 SYSCTL_PROC(_vfs_cache_param, OID_AUTO, fast_lookup, CTLTYPE_INT|CTLFLAG_RW|CTLFLAG_MPSAFE,
4248 &cache_fast_lookup, 0, syscal_vfs_cache_fast_lookup, "IU", "");
4249
4250 /*
4251 * Components of nameidata (or objects it can point to) which may
4252 * need restoring in case fast path lookup fails.
4253 */
4254 struct nameidata_outer {
4255 size_t ni_pathlen;
4256 uint64_t cn_flags;
4257 };
4258
4259 struct nameidata_saved {
4260 #ifdef INVARIANTS
4261 char *cn_nameptr;
4262 size_t ni_pathlen;
4263 #endif
4264 };
4265
4266 #ifdef INVARIANTS
4267 struct cache_fpl_debug {
4268 size_t ni_pathlen;
4269 };
4270 #endif
4271
4272 struct cache_fpl {
4273 struct nameidata *ndp;
4274 struct componentname *cnp;
4275 char *nulchar;
4276 struct vnode *dvp;
4277 struct vnode *tvp;
4278 seqc_t dvp_seqc;
4279 seqc_t tvp_seqc;
4280 uint32_t hash;
4281 struct nameidata_saved snd;
4282 struct nameidata_outer snd_outer;
4283 int line;
4284 enum cache_fpl_status status:8;
4285 bool in_smr;
4286 bool fsearch;
4287 struct pwd **pwd;
4288 #ifdef INVARIANTS
4289 struct cache_fpl_debug debug;
4290 #endif
4291 };
4292
4293 static bool cache_fplookup_mp_supported(struct mount *mp);
4294 static bool cache_fplookup_is_mp(struct cache_fpl *fpl);
4295 static int cache_fplookup_cross_mount(struct cache_fpl *fpl);
4296 static int cache_fplookup_partial_setup(struct cache_fpl *fpl);
4297 static int cache_fplookup_skip_slashes(struct cache_fpl *fpl);
4298 static int cache_fplookup_trailingslash(struct cache_fpl *fpl);
4299 static void cache_fpl_pathlen_dec(struct cache_fpl *fpl);
4300 static void cache_fpl_pathlen_inc(struct cache_fpl *fpl);
4301 static void cache_fpl_pathlen_add(struct cache_fpl *fpl, size_t n);
4302 static void cache_fpl_pathlen_sub(struct cache_fpl *fpl, size_t n);
4303
4304 static void
cache_fpl_cleanup_cnp(struct componentname * cnp)4305 cache_fpl_cleanup_cnp(struct componentname *cnp)
4306 {
4307
4308 uma_zfree(namei_zone, cnp->cn_pnbuf);
4309 cnp->cn_pnbuf = NULL;
4310 cnp->cn_nameptr = NULL;
4311 }
4312
4313 static struct vnode *
cache_fpl_handle_root(struct cache_fpl * fpl)4314 cache_fpl_handle_root(struct cache_fpl *fpl)
4315 {
4316 struct nameidata *ndp;
4317 struct componentname *cnp;
4318
4319 ndp = fpl->ndp;
4320 cnp = fpl->cnp;
4321
4322 MPASS(*(cnp->cn_nameptr) == '/');
4323 cnp->cn_nameptr++;
4324 cache_fpl_pathlen_dec(fpl);
4325
4326 if (__predict_false(*(cnp->cn_nameptr) == '/')) {
4327 do {
4328 cnp->cn_nameptr++;
4329 cache_fpl_pathlen_dec(fpl);
4330 } while (*(cnp->cn_nameptr) == '/');
4331 }
4332
4333 return (ndp->ni_rootdir);
4334 }
4335
4336 static void
cache_fpl_checkpoint_outer(struct cache_fpl * fpl)4337 cache_fpl_checkpoint_outer(struct cache_fpl *fpl)
4338 {
4339
4340 fpl->snd_outer.ni_pathlen = fpl->ndp->ni_pathlen;
4341 fpl->snd_outer.cn_flags = fpl->ndp->ni_cnd.cn_flags;
4342 }
4343
4344 static void
cache_fpl_checkpoint(struct cache_fpl * fpl)4345 cache_fpl_checkpoint(struct cache_fpl *fpl)
4346 {
4347
4348 #ifdef INVARIANTS
4349 fpl->snd.cn_nameptr = fpl->ndp->ni_cnd.cn_nameptr;
4350 fpl->snd.ni_pathlen = fpl->debug.ni_pathlen;
4351 #endif
4352 }
4353
4354 static void
cache_fpl_restore_partial(struct cache_fpl * fpl)4355 cache_fpl_restore_partial(struct cache_fpl *fpl)
4356 {
4357
4358 fpl->ndp->ni_cnd.cn_flags = fpl->snd_outer.cn_flags;
4359 #ifdef INVARIANTS
4360 fpl->debug.ni_pathlen = fpl->snd.ni_pathlen;
4361 #endif
4362 }
4363
4364 static void
cache_fpl_restore_abort(struct cache_fpl * fpl)4365 cache_fpl_restore_abort(struct cache_fpl *fpl)
4366 {
4367
4368 cache_fpl_restore_partial(fpl);
4369 /*
4370 * It is 0 on entry by API contract.
4371 */
4372 fpl->ndp->ni_resflags = 0;
4373 fpl->ndp->ni_cnd.cn_nameptr = fpl->ndp->ni_cnd.cn_pnbuf;
4374 fpl->ndp->ni_pathlen = fpl->snd_outer.ni_pathlen;
4375 }
4376
4377 #ifdef INVARIANTS
4378 #define cache_fpl_smr_assert_entered(fpl) ({ \
4379 struct cache_fpl *_fpl = (fpl); \
4380 MPASS(_fpl->in_smr == true); \
4381 VFS_SMR_ASSERT_ENTERED(); \
4382 })
4383 #define cache_fpl_smr_assert_not_entered(fpl) ({ \
4384 struct cache_fpl *_fpl = (fpl); \
4385 MPASS(_fpl->in_smr == false); \
4386 VFS_SMR_ASSERT_NOT_ENTERED(); \
4387 })
4388 static void
cache_fpl_assert_status(struct cache_fpl * fpl)4389 cache_fpl_assert_status(struct cache_fpl *fpl)
4390 {
4391
4392 switch (fpl->status) {
4393 case CACHE_FPL_STATUS_UNSET:
4394 __assert_unreachable();
4395 break;
4396 case CACHE_FPL_STATUS_DESTROYED:
4397 case CACHE_FPL_STATUS_ABORTED:
4398 case CACHE_FPL_STATUS_PARTIAL:
4399 case CACHE_FPL_STATUS_HANDLED:
4400 break;
4401 }
4402 }
4403 #else
4404 #define cache_fpl_smr_assert_entered(fpl) do { } while (0)
4405 #define cache_fpl_smr_assert_not_entered(fpl) do { } while (0)
4406 #define cache_fpl_assert_status(fpl) do { } while (0)
4407 #endif
4408
4409 #define cache_fpl_smr_enter_initial(fpl) ({ \
4410 struct cache_fpl *_fpl = (fpl); \
4411 vfs_smr_enter(); \
4412 _fpl->in_smr = true; \
4413 })
4414
4415 #define cache_fpl_smr_enter(fpl) ({ \
4416 struct cache_fpl *_fpl = (fpl); \
4417 MPASS(_fpl->in_smr == false); \
4418 vfs_smr_enter(); \
4419 _fpl->in_smr = true; \
4420 })
4421
4422 #define cache_fpl_smr_exit(fpl) ({ \
4423 struct cache_fpl *_fpl = (fpl); \
4424 MPASS(_fpl->in_smr == true); \
4425 vfs_smr_exit(); \
4426 _fpl->in_smr = false; \
4427 })
4428
4429 static int
cache_fpl_aborted_early_impl(struct cache_fpl * fpl,int line)4430 cache_fpl_aborted_early_impl(struct cache_fpl *fpl, int line)
4431 {
4432
4433 if (fpl->status != CACHE_FPL_STATUS_UNSET) {
4434 KASSERT(fpl->status == CACHE_FPL_STATUS_PARTIAL,
4435 ("%s: converting to abort from %d at %d, set at %d\n",
4436 __func__, fpl->status, line, fpl->line));
4437 }
4438 cache_fpl_smr_assert_not_entered(fpl);
4439 fpl->status = CACHE_FPL_STATUS_ABORTED;
4440 fpl->line = line;
4441 return (CACHE_FPL_FAILED);
4442 }
4443
4444 #define cache_fpl_aborted_early(x) cache_fpl_aborted_early_impl((x), __LINE__)
4445
4446 static int __noinline
cache_fpl_aborted_impl(struct cache_fpl * fpl,int line)4447 cache_fpl_aborted_impl(struct cache_fpl *fpl, int line)
4448 {
4449 struct nameidata *ndp;
4450 struct componentname *cnp;
4451
4452 ndp = fpl->ndp;
4453 cnp = fpl->cnp;
4454
4455 if (fpl->status != CACHE_FPL_STATUS_UNSET) {
4456 KASSERT(fpl->status == CACHE_FPL_STATUS_PARTIAL,
4457 ("%s: converting to abort from %d at %d, set at %d\n",
4458 __func__, fpl->status, line, fpl->line));
4459 }
4460 fpl->status = CACHE_FPL_STATUS_ABORTED;
4461 fpl->line = line;
4462 if (fpl->in_smr)
4463 cache_fpl_smr_exit(fpl);
4464 cache_fpl_restore_abort(fpl);
4465 /*
4466 * Resolving symlinks overwrites data passed by the caller.
4467 * Let namei know.
4468 */
4469 if (ndp->ni_loopcnt > 0) {
4470 fpl->status = CACHE_FPL_STATUS_DESTROYED;
4471 cache_fpl_cleanup_cnp(cnp);
4472 }
4473 return (CACHE_FPL_FAILED);
4474 }
4475
4476 #define cache_fpl_aborted(x) cache_fpl_aborted_impl((x), __LINE__)
4477
4478 static int __noinline
cache_fpl_partial_impl(struct cache_fpl * fpl,int line)4479 cache_fpl_partial_impl(struct cache_fpl *fpl, int line)
4480 {
4481
4482 KASSERT(fpl->status == CACHE_FPL_STATUS_UNSET,
4483 ("%s: setting to partial at %d, but already set to %d at %d\n",
4484 __func__, line, fpl->status, fpl->line));
4485 cache_fpl_smr_assert_entered(fpl);
4486 fpl->status = CACHE_FPL_STATUS_PARTIAL;
4487 fpl->line = line;
4488 return (cache_fplookup_partial_setup(fpl));
4489 }
4490
4491 #define cache_fpl_partial(x) cache_fpl_partial_impl((x), __LINE__)
4492
4493 static int
cache_fpl_handled_impl(struct cache_fpl * fpl,int line)4494 cache_fpl_handled_impl(struct cache_fpl *fpl, int line)
4495 {
4496
4497 KASSERT(fpl->status == CACHE_FPL_STATUS_UNSET,
4498 ("%s: setting to handled at %d, but already set to %d at %d\n",
4499 __func__, line, fpl->status, fpl->line));
4500 cache_fpl_smr_assert_not_entered(fpl);
4501 fpl->status = CACHE_FPL_STATUS_HANDLED;
4502 fpl->line = line;
4503 return (0);
4504 }
4505
4506 #define cache_fpl_handled(x) cache_fpl_handled_impl((x), __LINE__)
4507
4508 static int
cache_fpl_handled_error_impl(struct cache_fpl * fpl,int error,int line)4509 cache_fpl_handled_error_impl(struct cache_fpl *fpl, int error, int line)
4510 {
4511
4512 KASSERT(fpl->status == CACHE_FPL_STATUS_UNSET,
4513 ("%s: setting to handled at %d, but already set to %d at %d\n",
4514 __func__, line, fpl->status, fpl->line));
4515 MPASS(error != 0);
4516 MPASS(error != CACHE_FPL_FAILED);
4517 cache_fpl_smr_assert_not_entered(fpl);
4518 fpl->status = CACHE_FPL_STATUS_HANDLED;
4519 fpl->line = line;
4520 fpl->dvp = NULL;
4521 fpl->tvp = NULL;
4522 return (error);
4523 }
4524
4525 #define cache_fpl_handled_error(x, e) cache_fpl_handled_error_impl((x), (e), __LINE__)
4526
4527 static bool
cache_fpl_terminated(struct cache_fpl * fpl)4528 cache_fpl_terminated(struct cache_fpl *fpl)
4529 {
4530
4531 return (fpl->status != CACHE_FPL_STATUS_UNSET);
4532 }
4533
4534 #define CACHE_FPL_SUPPORTED_CN_FLAGS \
4535 (NC_NOMAKEENTRY | NC_KEEPPOSENTRY | LOCKLEAF | LOCKPARENT | WANTPARENT | \
4536 FAILIFEXISTS | FOLLOW | EMPTYPATH | LOCKSHARED | ISRESTARTED | WILLBEDIR | \
4537 ISOPEN | NOMACCHECK | AUDITVNODE1 | AUDITVNODE2 | NOCAPCHECK | OPENREAD | \
4538 OPENWRITE | WANTIOCTLCAPS | NAMEILOOKUP)
4539
4540 #define CACHE_FPL_INTERNAL_CN_FLAGS \
4541 (ISDOTDOT | MAKEENTRY | ISLASTCN)
4542
4543 _Static_assert((CACHE_FPL_SUPPORTED_CN_FLAGS & CACHE_FPL_INTERNAL_CN_FLAGS) == 0,
4544 "supported and internal flags overlap");
4545
4546 static bool
cache_fpl_islastcn(struct nameidata * ndp)4547 cache_fpl_islastcn(struct nameidata *ndp)
4548 {
4549
4550 return (*ndp->ni_next == 0);
4551 }
4552
4553 static bool
cache_fpl_istrailingslash(struct cache_fpl * fpl)4554 cache_fpl_istrailingslash(struct cache_fpl *fpl)
4555 {
4556
4557 MPASS(fpl->nulchar > fpl->cnp->cn_pnbuf);
4558 return (*(fpl->nulchar - 1) == '/');
4559 }
4560
4561 static bool
cache_fpl_isdotdot(struct componentname * cnp)4562 cache_fpl_isdotdot(struct componentname *cnp)
4563 {
4564
4565 if (cnp->cn_namelen == 2 &&
4566 cnp->cn_nameptr[1] == '.' && cnp->cn_nameptr[0] == '.')
4567 return (true);
4568 return (false);
4569 }
4570
4571 static bool
cache_can_fplookup(struct cache_fpl * fpl)4572 cache_can_fplookup(struct cache_fpl *fpl)
4573 {
4574 struct nameidata *ndp;
4575 struct componentname *cnp;
4576 struct thread *td;
4577
4578 ndp = fpl->ndp;
4579 cnp = fpl->cnp;
4580 td = curthread;
4581
4582 if (!atomic_load_char(&cache_fast_lookup_enabled)) {
4583 cache_fpl_aborted_early(fpl);
4584 return (false);
4585 }
4586 if ((cnp->cn_flags & ~CACHE_FPL_SUPPORTED_CN_FLAGS) != 0) {
4587 cache_fpl_aborted_early(fpl);
4588 return (false);
4589 }
4590 if (IN_CAPABILITY_MODE(td) || CAP_TRACING(td)) {
4591 cache_fpl_aborted_early(fpl);
4592 return (false);
4593 }
4594 if (AUDITING_TD(td)) {
4595 cache_fpl_aborted_early(fpl);
4596 return (false);
4597 }
4598 if (ndp->ni_startdir != NULL) {
4599 cache_fpl_aborted_early(fpl);
4600 return (false);
4601 }
4602 return (true);
4603 }
4604
4605 static int __noinline
cache_fplookup_dirfd(struct cache_fpl * fpl,struct vnode ** vpp)4606 cache_fplookup_dirfd(struct cache_fpl *fpl, struct vnode **vpp)
4607 {
4608 struct nameidata *ndp;
4609 struct componentname *cnp;
4610 int error, flags;
4611
4612 ndp = fpl->ndp;
4613 cnp = fpl->cnp;
4614
4615 error = fgetvp_lookup_smr(ndp, vpp, &flags);
4616 if (__predict_false(error != 0)) {
4617 return (cache_fpl_aborted(fpl));
4618 }
4619 if (__predict_false((flags & O_RESOLVE_BENEATH) != 0)) {
4620 _Static_assert((CACHE_FPL_SUPPORTED_CN_FLAGS & RBENEATH) == 0,
4621 "RBENEATH supported by fplookup");
4622 cache_fpl_smr_exit(fpl);
4623 cache_fpl_aborted(fpl);
4624 return (EOPNOTSUPP);
4625 }
4626 fpl->fsearch = (flags & FSEARCH) != 0;
4627 if ((*vpp)->v_type != VDIR) {
4628 if (!((cnp->cn_flags & EMPTYPATH) != 0 && cnp->cn_pnbuf[0] == '\0')) {
4629 cache_fpl_smr_exit(fpl);
4630 return (cache_fpl_handled_error(fpl, ENOTDIR));
4631 }
4632 }
4633 return (0);
4634 }
4635
4636 static int __noinline
cache_fplookup_negative_promote(struct cache_fpl * fpl,struct namecache * oncp,uint32_t hash)4637 cache_fplookup_negative_promote(struct cache_fpl *fpl, struct namecache *oncp,
4638 uint32_t hash)
4639 {
4640 struct componentname *cnp;
4641 struct vnode *dvp;
4642
4643 cnp = fpl->cnp;
4644 dvp = fpl->dvp;
4645
4646 cache_fpl_smr_exit(fpl);
4647 if (cache_neg_promote_cond(dvp, cnp, oncp, hash))
4648 return (cache_fpl_handled_error(fpl, ENOENT));
4649 else
4650 return (cache_fpl_aborted(fpl));
4651 }
4652
4653 /*
4654 * Prepare fallback to the locked lookup while trying to retain the progress.
4655 */
4656 static int __noinline
cache_fplookup_partial_setup(struct cache_fpl * fpl)4657 cache_fplookup_partial_setup(struct cache_fpl *fpl)
4658 {
4659 struct nameidata *ndp;
4660 struct componentname *cnp;
4661 enum vgetstate dvs;
4662 struct vnode *dvp;
4663 struct pwd *pwd;
4664 seqc_t dvp_seqc;
4665
4666 ndp = fpl->ndp;
4667 cnp = fpl->cnp;
4668 pwd = *(fpl->pwd);
4669 dvp = fpl->dvp;
4670 dvp_seqc = fpl->dvp_seqc;
4671
4672 if (!pwd_hold_smr(pwd)) {
4673 return (cache_fpl_aborted(fpl));
4674 }
4675
4676 /*
4677 * Note that seqc is checked before the vnode is locked, so by
4678 * the time regular lookup gets to it it may have moved.
4679 *
4680 * Ultimately this does not affect correctness, any lookup errors
4681 * are userspace racing with itself. It is guaranteed that any
4682 * path which ultimately gets found could also have been found
4683 * by regular lookup going all the way in absence of concurrent
4684 * modifications.
4685 */
4686 dvs = vget_prep_smr(dvp);
4687 cache_fpl_smr_exit(fpl);
4688 if (__predict_false(dvs == VGET_NONE)) {
4689 pwd_drop(pwd);
4690 return (cache_fpl_aborted(fpl));
4691 }
4692
4693 vget_finish_ref(dvp, dvs);
4694 if (!vn_seqc_consistent(dvp, dvp_seqc)) {
4695 vrele(dvp);
4696 pwd_drop(pwd);
4697 return (cache_fpl_aborted(fpl));
4698 }
4699
4700 cache_fpl_restore_partial(fpl);
4701 #ifdef INVARIANTS
4702 if (cnp->cn_nameptr != fpl->snd.cn_nameptr) {
4703 panic("%s: cn_nameptr mismatch (%p != %p) full [%s]\n", __func__,
4704 cnp->cn_nameptr, fpl->snd.cn_nameptr, cnp->cn_pnbuf);
4705 }
4706 #endif
4707
4708 ndp->ni_startdir = dvp;
4709 cnp->cn_flags |= MAKEENTRY;
4710 if (cache_fpl_islastcn(ndp))
4711 cnp->cn_flags |= ISLASTCN;
4712 if (cache_fpl_isdotdot(cnp))
4713 cnp->cn_flags |= ISDOTDOT;
4714
4715 /*
4716 * Skip potential extra slashes parsing did not take care of.
4717 * cache_fplookup_skip_slashes explains the mechanism.
4718 */
4719 if (__predict_false(*(cnp->cn_nameptr) == '/')) {
4720 do {
4721 cnp->cn_nameptr++;
4722 cache_fpl_pathlen_dec(fpl);
4723 } while (*(cnp->cn_nameptr) == '/');
4724 }
4725
4726 ndp->ni_pathlen = fpl->nulchar - cnp->cn_nameptr + 1;
4727 #ifdef INVARIANTS
4728 if (ndp->ni_pathlen != fpl->debug.ni_pathlen) {
4729 panic("%s: mismatch (%zu != %zu) nulchar %p nameptr %p [%s] ; full string [%s]\n",
4730 __func__, ndp->ni_pathlen, fpl->debug.ni_pathlen, fpl->nulchar,
4731 cnp->cn_nameptr, cnp->cn_nameptr, cnp->cn_pnbuf);
4732 }
4733 #endif
4734 return (0);
4735 }
4736
4737 static int
cache_fplookup_final_child(struct cache_fpl * fpl,enum vgetstate tvs)4738 cache_fplookup_final_child(struct cache_fpl *fpl, enum vgetstate tvs)
4739 {
4740 struct componentname *cnp;
4741 struct vnode *tvp;
4742 seqc_t tvp_seqc;
4743 int error, lkflags;
4744
4745 cnp = fpl->cnp;
4746 tvp = fpl->tvp;
4747 tvp_seqc = fpl->tvp_seqc;
4748
4749 if ((cnp->cn_flags & LOCKLEAF) != 0) {
4750 lkflags = LK_SHARED;
4751 if ((cnp->cn_flags & LOCKSHARED) == 0)
4752 lkflags = LK_EXCLUSIVE;
4753 error = vget_finish(tvp, lkflags, tvs);
4754 if (__predict_false(error != 0)) {
4755 return (cache_fpl_aborted(fpl));
4756 }
4757 } else {
4758 vget_finish_ref(tvp, tvs);
4759 }
4760
4761 if (!vn_seqc_consistent(tvp, tvp_seqc)) {
4762 if ((cnp->cn_flags & LOCKLEAF) != 0)
4763 vput(tvp);
4764 else
4765 vrele(tvp);
4766 return (cache_fpl_aborted(fpl));
4767 }
4768
4769 return (cache_fpl_handled(fpl));
4770 }
4771
4772 /*
4773 * They want to possibly modify the state of the namecache.
4774 */
4775 static int __noinline
cache_fplookup_final_modifying(struct cache_fpl * fpl)4776 cache_fplookup_final_modifying(struct cache_fpl *fpl)
4777 {
4778 struct nameidata *ndp __diagused;
4779 struct componentname *cnp;
4780 enum vgetstate dvs;
4781 struct vnode *dvp, *tvp;
4782 struct mount *mp;
4783 seqc_t dvp_seqc;
4784 int error;
4785 bool docache;
4786
4787 ndp = fpl->ndp;
4788 cnp = fpl->cnp;
4789 dvp = fpl->dvp;
4790 dvp_seqc = fpl->dvp_seqc;
4791
4792 MPASS(*(cnp->cn_nameptr) != '/');
4793 MPASS(cache_fpl_islastcn(ndp));
4794 if ((cnp->cn_flags & LOCKPARENT) == 0)
4795 MPASS((cnp->cn_flags & WANTPARENT) != 0);
4796 MPASS((cnp->cn_flags & TRAILINGSLASH) == 0);
4797 MPASS(cnp->cn_nameiop == CREATE || cnp->cn_nameiop == DELETE ||
4798 cnp->cn_nameiop == RENAME);
4799 MPASS((cnp->cn_flags & MAKEENTRY) == 0);
4800 MPASS((cnp->cn_flags & ISDOTDOT) == 0);
4801
4802 docache = (cnp->cn_flags & NOCACHE) ^ NOCACHE;
4803 if (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME)
4804 docache = false;
4805
4806 /*
4807 * Regular lookup nulifies the slash, which we don't do here.
4808 * Don't take chances with filesystem routines seeing it for
4809 * the last entry.
4810 */
4811 if (cache_fpl_istrailingslash(fpl)) {
4812 return (cache_fpl_partial(fpl));
4813 }
4814
4815 mp = atomic_load_ptr(&dvp->v_mount);
4816 if (__predict_false(mp == NULL)) {
4817 return (cache_fpl_aborted(fpl));
4818 }
4819
4820 if (__predict_false(mp->mnt_flag & MNT_RDONLY)) {
4821 cache_fpl_smr_exit(fpl);
4822 /*
4823 * Original code keeps not checking for CREATE which
4824 * might be a bug. For now let the old lookup decide.
4825 */
4826 if (cnp->cn_nameiop == CREATE) {
4827 return (cache_fpl_aborted(fpl));
4828 }
4829 return (cache_fpl_handled_error(fpl, EROFS));
4830 }
4831
4832 if (fpl->tvp != NULL && (cnp->cn_flags & FAILIFEXISTS) != 0) {
4833 cache_fpl_smr_exit(fpl);
4834 return (cache_fpl_handled_error(fpl, EEXIST));
4835 }
4836
4837 /*
4838 * Secure access to dvp; check cache_fplookup_partial_setup for
4839 * reasoning.
4840 *
4841 * XXX At least UFS requires its lookup routine to be called for
4842 * the last path component, which leads to some level of complication
4843 * and inefficiency:
4844 * - the target routine always locks the target vnode, but our caller
4845 * may not need it locked
4846 * - some of the VOP machinery asserts that the parent is locked, which
4847 * once more may be not required
4848 *
4849 * TODO: add a flag for filesystems which don't need this.
4850 */
4851 dvs = vget_prep_smr(dvp);
4852 cache_fpl_smr_exit(fpl);
4853 if (__predict_false(dvs == VGET_NONE)) {
4854 return (cache_fpl_aborted(fpl));
4855 }
4856
4857 vget_finish_ref(dvp, dvs);
4858 if (!vn_seqc_consistent(dvp, dvp_seqc)) {
4859 vrele(dvp);
4860 return (cache_fpl_aborted(fpl));
4861 }
4862
4863 error = vn_lock(dvp, LK_EXCLUSIVE);
4864 if (__predict_false(error != 0)) {
4865 vrele(dvp);
4866 return (cache_fpl_aborted(fpl));
4867 }
4868
4869 tvp = NULL;
4870 cnp->cn_flags |= ISLASTCN;
4871 if (docache)
4872 cnp->cn_flags |= MAKEENTRY;
4873 if (cache_fpl_isdotdot(cnp))
4874 cnp->cn_flags |= ISDOTDOT;
4875 cnp->cn_lkflags = LK_EXCLUSIVE;
4876 error = VOP_LOOKUP(dvp, &tvp, cnp);
4877 switch (error) {
4878 case EJUSTRETURN:
4879 case 0:
4880 break;
4881 case ENOTDIR:
4882 case ENOENT:
4883 vput(dvp);
4884 return (cache_fpl_handled_error(fpl, error));
4885 default:
4886 vput(dvp);
4887 return (cache_fpl_aborted(fpl));
4888 }
4889
4890 fpl->tvp = tvp;
4891
4892 if (tvp == NULL) {
4893 MPASS(error == EJUSTRETURN);
4894 if ((cnp->cn_flags & LOCKPARENT) == 0) {
4895 VOP_UNLOCK(dvp);
4896 }
4897 return (cache_fpl_handled(fpl));
4898 }
4899
4900 /*
4901 * There are very hairy corner cases concerning various flag combinations
4902 * and locking state. In particular here we only hold one lock instead of
4903 * two.
4904 *
4905 * Skip the complexity as it is of no significance for normal workloads.
4906 */
4907 if (__predict_false(tvp == dvp)) {
4908 vput(dvp);
4909 vrele(tvp);
4910 return (cache_fpl_aborted(fpl));
4911 }
4912
4913 /*
4914 * If they want the symlink itself we are fine, but if they want to
4915 * follow it regular lookup has to be engaged.
4916 */
4917 if (tvp->v_type == VLNK) {
4918 if ((cnp->cn_flags & FOLLOW) != 0) {
4919 vput(dvp);
4920 vput(tvp);
4921 return (cache_fpl_aborted(fpl));
4922 }
4923 }
4924
4925 /*
4926 * Since we expect this to be the terminal vnode it should almost never
4927 * be a mount point.
4928 */
4929 if (__predict_false(cache_fplookup_is_mp(fpl))) {
4930 vput(dvp);
4931 vput(tvp);
4932 return (cache_fpl_aborted(fpl));
4933 }
4934
4935 if ((cnp->cn_flags & FAILIFEXISTS) != 0) {
4936 vput(dvp);
4937 vput(tvp);
4938 return (cache_fpl_handled_error(fpl, EEXIST));
4939 }
4940
4941 if ((cnp->cn_flags & LOCKLEAF) == 0) {
4942 VOP_UNLOCK(tvp);
4943 }
4944
4945 if ((cnp->cn_flags & LOCKPARENT) == 0) {
4946 VOP_UNLOCK(dvp);
4947 }
4948
4949 return (cache_fpl_handled(fpl));
4950 }
4951
4952 static int __noinline
cache_fplookup_modifying(struct cache_fpl * fpl)4953 cache_fplookup_modifying(struct cache_fpl *fpl)
4954 {
4955 struct nameidata *ndp;
4956
4957 ndp = fpl->ndp;
4958
4959 if (!cache_fpl_islastcn(ndp)) {
4960 return (cache_fpl_partial(fpl));
4961 }
4962 return (cache_fplookup_final_modifying(fpl));
4963 }
4964
4965 static int __noinline
cache_fplookup_final_withparent(struct cache_fpl * fpl)4966 cache_fplookup_final_withparent(struct cache_fpl *fpl)
4967 {
4968 struct componentname *cnp;
4969 enum vgetstate dvs, tvs;
4970 struct vnode *dvp, *tvp;
4971 seqc_t dvp_seqc;
4972 int error;
4973
4974 cnp = fpl->cnp;
4975 dvp = fpl->dvp;
4976 dvp_seqc = fpl->dvp_seqc;
4977 tvp = fpl->tvp;
4978
4979 MPASS((cnp->cn_flags & (LOCKPARENT|WANTPARENT)) != 0);
4980
4981 /*
4982 * This is less efficient than it can be for simplicity.
4983 */
4984 dvs = vget_prep_smr(dvp);
4985 if (__predict_false(dvs == VGET_NONE)) {
4986 return (cache_fpl_aborted(fpl));
4987 }
4988 tvs = vget_prep_smr(tvp);
4989 if (__predict_false(tvs == VGET_NONE)) {
4990 cache_fpl_smr_exit(fpl);
4991 vget_abort(dvp, dvs);
4992 return (cache_fpl_aborted(fpl));
4993 }
4994
4995 cache_fpl_smr_exit(fpl);
4996
4997 if ((cnp->cn_flags & LOCKPARENT) != 0) {
4998 error = vget_finish(dvp, LK_EXCLUSIVE, dvs);
4999 if (__predict_false(error != 0)) {
5000 vget_abort(tvp, tvs);
5001 return (cache_fpl_aborted(fpl));
5002 }
5003 } else {
5004 vget_finish_ref(dvp, dvs);
5005 }
5006
5007 if (!vn_seqc_consistent(dvp, dvp_seqc)) {
5008 vget_abort(tvp, tvs);
5009 if ((cnp->cn_flags & LOCKPARENT) != 0)
5010 vput(dvp);
5011 else
5012 vrele(dvp);
5013 return (cache_fpl_aborted(fpl));
5014 }
5015
5016 error = cache_fplookup_final_child(fpl, tvs);
5017 if (__predict_false(error != 0)) {
5018 MPASS(fpl->status == CACHE_FPL_STATUS_ABORTED ||
5019 fpl->status == CACHE_FPL_STATUS_DESTROYED);
5020 if ((cnp->cn_flags & LOCKPARENT) != 0)
5021 vput(dvp);
5022 else
5023 vrele(dvp);
5024 return (error);
5025 }
5026
5027 MPASS(fpl->status == CACHE_FPL_STATUS_HANDLED);
5028 return (0);
5029 }
5030
5031 static int
cache_fplookup_final(struct cache_fpl * fpl)5032 cache_fplookup_final(struct cache_fpl *fpl)
5033 {
5034 struct componentname *cnp;
5035 enum vgetstate tvs;
5036 struct vnode *dvp, *tvp;
5037 seqc_t dvp_seqc;
5038
5039 cnp = fpl->cnp;
5040 dvp = fpl->dvp;
5041 dvp_seqc = fpl->dvp_seqc;
5042 tvp = fpl->tvp;
5043
5044 MPASS(*(cnp->cn_nameptr) != '/');
5045
5046 if (cnp->cn_nameiop != LOOKUP) {
5047 return (cache_fplookup_final_modifying(fpl));
5048 }
5049
5050 if ((cnp->cn_flags & (LOCKPARENT|WANTPARENT)) != 0)
5051 return (cache_fplookup_final_withparent(fpl));
5052
5053 tvs = vget_prep_smr(tvp);
5054 if (__predict_false(tvs == VGET_NONE)) {
5055 return (cache_fpl_partial(fpl));
5056 }
5057
5058 if (!vn_seqc_consistent(dvp, dvp_seqc)) {
5059 cache_fpl_smr_exit(fpl);
5060 vget_abort(tvp, tvs);
5061 return (cache_fpl_aborted(fpl));
5062 }
5063
5064 cache_fpl_smr_exit(fpl);
5065 return (cache_fplookup_final_child(fpl, tvs));
5066 }
5067
5068 /*
5069 * Comment from locked lookup:
5070 * Check for degenerate name (e.g. / or "") which is a way of talking about a
5071 * directory, e.g. like "/." or ".".
5072 */
5073 static int __noinline
cache_fplookup_degenerate(struct cache_fpl * fpl)5074 cache_fplookup_degenerate(struct cache_fpl *fpl)
5075 {
5076 struct componentname *cnp;
5077 struct vnode *dvp;
5078 enum vgetstate dvs;
5079 int error, lkflags;
5080 #ifdef INVARIANTS
5081 char *cp;
5082 #endif
5083
5084 fpl->tvp = fpl->dvp;
5085 fpl->tvp_seqc = fpl->dvp_seqc;
5086
5087 cnp = fpl->cnp;
5088 dvp = fpl->dvp;
5089
5090 #ifdef INVARIANTS
5091 for (cp = cnp->cn_pnbuf; *cp != '\0'; cp++) {
5092 KASSERT(*cp == '/',
5093 ("%s: encountered non-slash; string [%s]\n", __func__,
5094 cnp->cn_pnbuf));
5095 }
5096 #endif
5097
5098 if (__predict_false(cnp->cn_nameiop != LOOKUP)) {
5099 cache_fpl_smr_exit(fpl);
5100 return (cache_fpl_handled_error(fpl, EISDIR));
5101 }
5102
5103 if ((cnp->cn_flags & (LOCKPARENT|WANTPARENT)) != 0) {
5104 return (cache_fplookup_final_withparent(fpl));
5105 }
5106
5107 dvs = vget_prep_smr(dvp);
5108 cache_fpl_smr_exit(fpl);
5109 if (__predict_false(dvs == VGET_NONE)) {
5110 return (cache_fpl_aborted(fpl));
5111 }
5112
5113 if ((cnp->cn_flags & LOCKLEAF) != 0) {
5114 lkflags = LK_SHARED;
5115 if ((cnp->cn_flags & LOCKSHARED) == 0)
5116 lkflags = LK_EXCLUSIVE;
5117 error = vget_finish(dvp, lkflags, dvs);
5118 if (__predict_false(error != 0)) {
5119 return (cache_fpl_aborted(fpl));
5120 }
5121 } else {
5122 vget_finish_ref(dvp, dvs);
5123 }
5124 return (cache_fpl_handled(fpl));
5125 }
5126
5127 static int __noinline
cache_fplookup_emptypath(struct cache_fpl * fpl)5128 cache_fplookup_emptypath(struct cache_fpl *fpl)
5129 {
5130 struct nameidata *ndp;
5131 struct componentname *cnp;
5132 enum vgetstate tvs;
5133 struct vnode *tvp;
5134 int error, lkflags;
5135
5136 fpl->tvp = fpl->dvp;
5137 fpl->tvp_seqc = fpl->dvp_seqc;
5138
5139 ndp = fpl->ndp;
5140 cnp = fpl->cnp;
5141 tvp = fpl->tvp;
5142
5143 MPASS(*cnp->cn_pnbuf == '\0');
5144
5145 if (__predict_false((cnp->cn_flags & EMPTYPATH) == 0)) {
5146 cache_fpl_smr_exit(fpl);
5147 return (cache_fpl_handled_error(fpl, ENOENT));
5148 }
5149
5150 MPASS((cnp->cn_flags & (LOCKPARENT | WANTPARENT)) == 0);
5151
5152 tvs = vget_prep_smr(tvp);
5153 cache_fpl_smr_exit(fpl);
5154 if (__predict_false(tvs == VGET_NONE)) {
5155 return (cache_fpl_aborted(fpl));
5156 }
5157
5158 if ((cnp->cn_flags & LOCKLEAF) != 0) {
5159 lkflags = LK_SHARED;
5160 if ((cnp->cn_flags & LOCKSHARED) == 0)
5161 lkflags = LK_EXCLUSIVE;
5162 error = vget_finish(tvp, lkflags, tvs);
5163 if (__predict_false(error != 0)) {
5164 return (cache_fpl_aborted(fpl));
5165 }
5166 } else {
5167 vget_finish_ref(tvp, tvs);
5168 }
5169
5170 ndp->ni_resflags |= NIRES_EMPTYPATH;
5171 return (cache_fpl_handled(fpl));
5172 }
5173
5174 static int __noinline
cache_fplookup_noentry(struct cache_fpl * fpl)5175 cache_fplookup_noentry(struct cache_fpl *fpl)
5176 {
5177 struct nameidata *ndp;
5178 struct componentname *cnp;
5179 enum vgetstate dvs;
5180 struct vnode *dvp, *tvp;
5181 seqc_t dvp_seqc;
5182 int error;
5183
5184 ndp = fpl->ndp;
5185 cnp = fpl->cnp;
5186 dvp = fpl->dvp;
5187 dvp_seqc = fpl->dvp_seqc;
5188
5189 MPASS((cnp->cn_flags & MAKEENTRY) == 0);
5190 MPASS((cnp->cn_flags & ISDOTDOT) == 0);
5191 if (cnp->cn_nameiop == LOOKUP)
5192 MPASS((cnp->cn_flags & NOCACHE) == 0);
5193 MPASS(!cache_fpl_isdotdot(cnp));
5194
5195 /*
5196 * Hack: delayed name len checking.
5197 */
5198 if (__predict_false(cnp->cn_namelen > NAME_MAX)) {
5199 cache_fpl_smr_exit(fpl);
5200 return (cache_fpl_handled_error(fpl, ENAMETOOLONG));
5201 }
5202
5203 if (cnp->cn_nameptr[0] == '/') {
5204 return (cache_fplookup_skip_slashes(fpl));
5205 }
5206
5207 if (cnp->cn_pnbuf[0] == '\0') {
5208 return (cache_fplookup_emptypath(fpl));
5209 }
5210
5211 if (cnp->cn_nameptr[0] == '\0') {
5212 if (fpl->tvp == NULL) {
5213 return (cache_fplookup_degenerate(fpl));
5214 }
5215 return (cache_fplookup_trailingslash(fpl));
5216 }
5217
5218 if (cnp->cn_nameiop != LOOKUP) {
5219 fpl->tvp = NULL;
5220 return (cache_fplookup_modifying(fpl));
5221 }
5222
5223 /*
5224 * Only try to fill in the component if it is the last one,
5225 * otherwise not only there may be several to handle but the
5226 * walk may be complicated.
5227 */
5228 if (!cache_fpl_islastcn(ndp)) {
5229 return (cache_fpl_partial(fpl));
5230 }
5231
5232 /*
5233 * Regular lookup nulifies the slash, which we don't do here.
5234 * Don't take chances with filesystem routines seeing it for
5235 * the last entry.
5236 */
5237 if (cache_fpl_istrailingslash(fpl)) {
5238 return (cache_fpl_partial(fpl));
5239 }
5240
5241 /*
5242 * Secure access to dvp; check cache_fplookup_partial_setup for
5243 * reasoning.
5244 */
5245 dvs = vget_prep_smr(dvp);
5246 cache_fpl_smr_exit(fpl);
5247 if (__predict_false(dvs == VGET_NONE)) {
5248 return (cache_fpl_aborted(fpl));
5249 }
5250
5251 vget_finish_ref(dvp, dvs);
5252 if (!vn_seqc_consistent(dvp, dvp_seqc)) {
5253 vrele(dvp);
5254 return (cache_fpl_aborted(fpl));
5255 }
5256
5257 error = vn_lock(dvp, LK_SHARED);
5258 if (__predict_false(error != 0)) {
5259 vrele(dvp);
5260 return (cache_fpl_aborted(fpl));
5261 }
5262
5263 tvp = NULL;
5264 /*
5265 * TODO: provide variants which don't require locking either vnode.
5266 */
5267 cnp->cn_flags |= ISLASTCN | MAKEENTRY;
5268 cnp->cn_lkflags = LK_SHARED;
5269 if ((cnp->cn_flags & LOCKSHARED) == 0) {
5270 cnp->cn_lkflags = LK_EXCLUSIVE;
5271 }
5272 error = VOP_LOOKUP(dvp, &tvp, cnp);
5273 switch (error) {
5274 case EJUSTRETURN:
5275 case 0:
5276 break;
5277 case ENOTDIR:
5278 case ENOENT:
5279 vput(dvp);
5280 return (cache_fpl_handled_error(fpl, error));
5281 default:
5282 vput(dvp);
5283 return (cache_fpl_aborted(fpl));
5284 }
5285
5286 fpl->tvp = tvp;
5287
5288 if (tvp == NULL) {
5289 MPASS(error == EJUSTRETURN);
5290 if ((cnp->cn_flags & (WANTPARENT | LOCKPARENT)) == 0) {
5291 vput(dvp);
5292 } else if ((cnp->cn_flags & LOCKPARENT) == 0) {
5293 VOP_UNLOCK(dvp);
5294 }
5295 return (cache_fpl_handled(fpl));
5296 }
5297
5298 if (tvp->v_type == VLNK) {
5299 if ((cnp->cn_flags & FOLLOW) != 0) {
5300 vput(dvp);
5301 vput(tvp);
5302 return (cache_fpl_aborted(fpl));
5303 }
5304 }
5305
5306 if (__predict_false(cache_fplookup_is_mp(fpl))) {
5307 vput(dvp);
5308 vput(tvp);
5309 return (cache_fpl_aborted(fpl));
5310 }
5311
5312 if ((cnp->cn_flags & LOCKLEAF) == 0) {
5313 VOP_UNLOCK(tvp);
5314 }
5315
5316 if ((cnp->cn_flags & (WANTPARENT | LOCKPARENT)) == 0) {
5317 vput(dvp);
5318 } else if ((cnp->cn_flags & LOCKPARENT) == 0) {
5319 VOP_UNLOCK(dvp);
5320 }
5321 return (cache_fpl_handled(fpl));
5322 }
5323
5324 static int __noinline
cache_fplookup_dot(struct cache_fpl * fpl)5325 cache_fplookup_dot(struct cache_fpl *fpl)
5326 {
5327 int error;
5328
5329 MPASS(!seqc_in_modify(fpl->dvp_seqc));
5330
5331 if (__predict_false(fpl->dvp->v_type != VDIR)) {
5332 cache_fpl_smr_exit(fpl);
5333 return (cache_fpl_handled_error(fpl, ENOTDIR));
5334 }
5335
5336 /*
5337 * Just re-assign the value. seqc will be checked later for the first
5338 * non-dot path component in line and/or before deciding to return the
5339 * vnode.
5340 */
5341 fpl->tvp = fpl->dvp;
5342 fpl->tvp_seqc = fpl->dvp_seqc;
5343
5344 SDT_PROBE3(vfs, namecache, lookup, hit, fpl->dvp, ".", fpl->dvp);
5345
5346 error = 0;
5347 if (cache_fplookup_is_mp(fpl)) {
5348 error = cache_fplookup_cross_mount(fpl);
5349 }
5350 return (error);
5351 }
5352
5353 static int __noinline
cache_fplookup_dotdot(struct cache_fpl * fpl)5354 cache_fplookup_dotdot(struct cache_fpl *fpl)
5355 {
5356 struct nameidata *ndp;
5357 struct namecache *ncp;
5358 struct vnode *dvp;
5359 u_char nc_flag;
5360
5361 ndp = fpl->ndp;
5362 dvp = fpl->dvp;
5363
5364 MPASS(cache_fpl_isdotdot(fpl->cnp));
5365
5366 /*
5367 * XXX this is racy the same way regular lookup is
5368 */
5369 if (vfs_lookup_isroot(ndp, dvp)) {
5370 fpl->tvp = dvp;
5371 fpl->tvp_seqc = vn_seqc_read_any(dvp);
5372 if (seqc_in_modify(fpl->tvp_seqc)) {
5373 return (cache_fpl_aborted(fpl));
5374 }
5375 return (0);
5376 }
5377
5378 if ((dvp->v_vflag & VV_ROOT) != 0) {
5379 /*
5380 * TODO
5381 * The opposite of climb mount is needed here.
5382 */
5383 return (cache_fpl_partial(fpl));
5384 }
5385
5386 if (__predict_false(dvp->v_type != VDIR)) {
5387 cache_fpl_smr_exit(fpl);
5388 return (cache_fpl_handled_error(fpl, ENOTDIR));
5389 }
5390
5391 ncp = atomic_load_consume_ptr(&dvp->v_cache_dd);
5392 if (ncp == NULL) {
5393 return (cache_fpl_aborted(fpl));
5394 }
5395
5396 nc_flag = atomic_load_char(&ncp->nc_flag);
5397 if ((nc_flag & NCF_ISDOTDOT) != 0) {
5398 if ((nc_flag & NCF_NEGATIVE) != 0)
5399 return (cache_fpl_aborted(fpl));
5400 fpl->tvp = ncp->nc_vp;
5401 } else {
5402 fpl->tvp = ncp->nc_dvp;
5403 }
5404
5405 fpl->tvp_seqc = vn_seqc_read_any(fpl->tvp);
5406 if (seqc_in_modify(fpl->tvp_seqc)) {
5407 return (cache_fpl_partial(fpl));
5408 }
5409
5410 /*
5411 * Acquire fence provided by vn_seqc_read_any above.
5412 */
5413 if (__predict_false(atomic_load_ptr(&dvp->v_cache_dd) != ncp)) {
5414 return (cache_fpl_aborted(fpl));
5415 }
5416
5417 if (!cache_ncp_canuse(ncp)) {
5418 return (cache_fpl_aborted(fpl));
5419 }
5420
5421 return (0);
5422 }
5423
5424 static int __noinline
cache_fplookup_neg(struct cache_fpl * fpl,struct namecache * ncp,uint32_t hash)5425 cache_fplookup_neg(struct cache_fpl *fpl, struct namecache *ncp, uint32_t hash)
5426 {
5427 u_char nc_flag __diagused;
5428 bool neg_promote;
5429
5430 #ifdef INVARIANTS
5431 nc_flag = atomic_load_char(&ncp->nc_flag);
5432 MPASS((nc_flag & NCF_NEGATIVE) != 0);
5433 #endif
5434 /*
5435 * If they want to create an entry we need to replace this one.
5436 */
5437 if (__predict_false(fpl->cnp->cn_nameiop != LOOKUP)) {
5438 fpl->tvp = NULL;
5439 return (cache_fplookup_modifying(fpl));
5440 }
5441 neg_promote = cache_neg_hit_prep(ncp);
5442 if (!cache_fpl_neg_ncp_canuse(ncp)) {
5443 cache_neg_hit_abort(ncp);
5444 return (cache_fpl_partial(fpl));
5445 }
5446 if (neg_promote) {
5447 return (cache_fplookup_negative_promote(fpl, ncp, hash));
5448 }
5449 cache_neg_hit_finish(ncp);
5450 cache_fpl_smr_exit(fpl);
5451 return (cache_fpl_handled_error(fpl, ENOENT));
5452 }
5453
5454 /*
5455 * Resolve a symlink. Called by filesystem-specific routines.
5456 *
5457 * Code flow is:
5458 * ... -> cache_fplookup_symlink -> VOP_FPLOOKUP_SYMLINK -> cache_symlink_resolve
5459 */
5460 int
cache_symlink_resolve(struct cache_fpl * fpl,const char * string,size_t len)5461 cache_symlink_resolve(struct cache_fpl *fpl, const char *string, size_t len)
5462 {
5463 struct nameidata *ndp;
5464 struct componentname *cnp;
5465 size_t adjust;
5466
5467 ndp = fpl->ndp;
5468 cnp = fpl->cnp;
5469
5470 if (__predict_false(len == 0)) {
5471 return (ENOENT);
5472 }
5473
5474 if (__predict_false(len > MAXPATHLEN - 2)) {
5475 if (cache_fpl_istrailingslash(fpl)) {
5476 return (EAGAIN);
5477 }
5478 }
5479
5480 ndp->ni_pathlen = fpl->nulchar - cnp->cn_nameptr - cnp->cn_namelen + 1;
5481 #ifdef INVARIANTS
5482 if (ndp->ni_pathlen != fpl->debug.ni_pathlen) {
5483 panic("%s: mismatch (%zu != %zu) nulchar %p nameptr %p [%s] ; full string [%s]\n",
5484 __func__, ndp->ni_pathlen, fpl->debug.ni_pathlen, fpl->nulchar,
5485 cnp->cn_nameptr, cnp->cn_nameptr, cnp->cn_pnbuf);
5486 }
5487 #endif
5488
5489 if (__predict_false(len + ndp->ni_pathlen > MAXPATHLEN)) {
5490 return (ENAMETOOLONG);
5491 }
5492
5493 if (__predict_false(ndp->ni_loopcnt++ >= MAXSYMLINKS)) {
5494 return (ELOOP);
5495 }
5496
5497 adjust = len;
5498 if (ndp->ni_pathlen > 1) {
5499 bcopy(ndp->ni_next, cnp->cn_pnbuf + len, ndp->ni_pathlen);
5500 } else {
5501 if (cache_fpl_istrailingslash(fpl)) {
5502 adjust = len + 1;
5503 cnp->cn_pnbuf[len] = '/';
5504 cnp->cn_pnbuf[len + 1] = '\0';
5505 } else {
5506 cnp->cn_pnbuf[len] = '\0';
5507 }
5508 }
5509 bcopy(string, cnp->cn_pnbuf, len);
5510
5511 ndp->ni_pathlen += adjust;
5512 cache_fpl_pathlen_add(fpl, adjust);
5513 cnp->cn_nameptr = cnp->cn_pnbuf;
5514 fpl->nulchar = &cnp->cn_nameptr[ndp->ni_pathlen - 1];
5515 fpl->tvp = NULL;
5516 return (0);
5517 }
5518
5519 static int __noinline
cache_fplookup_symlink(struct cache_fpl * fpl)5520 cache_fplookup_symlink(struct cache_fpl *fpl)
5521 {
5522 struct mount *mp;
5523 struct nameidata *ndp;
5524 struct componentname *cnp;
5525 struct vnode *dvp, *tvp;
5526 struct pwd *pwd;
5527 int error;
5528
5529 ndp = fpl->ndp;
5530 cnp = fpl->cnp;
5531 dvp = fpl->dvp;
5532 tvp = fpl->tvp;
5533 pwd = *(fpl->pwd);
5534
5535 if (cache_fpl_islastcn(ndp)) {
5536 if ((cnp->cn_flags & FOLLOW) == 0) {
5537 return (cache_fplookup_final(fpl));
5538 }
5539 }
5540
5541 mp = atomic_load_ptr(&dvp->v_mount);
5542 if (__predict_false(mp == NULL)) {
5543 return (cache_fpl_aborted(fpl));
5544 }
5545
5546 /*
5547 * Note this check races against setting the flag just like regular
5548 * lookup.
5549 */
5550 if (__predict_false((mp->mnt_flag & MNT_NOSYMFOLLOW) != 0)) {
5551 cache_fpl_smr_exit(fpl);
5552 return (cache_fpl_handled_error(fpl, EACCES));
5553 }
5554
5555 error = VOP_FPLOOKUP_SYMLINK(tvp, fpl);
5556 if (__predict_false(error != 0)) {
5557 switch (error) {
5558 case EAGAIN:
5559 return (cache_fpl_partial(fpl));
5560 case ENOENT:
5561 case ENAMETOOLONG:
5562 case ELOOP:
5563 cache_fpl_smr_exit(fpl);
5564 return (cache_fpl_handled_error(fpl, error));
5565 default:
5566 return (cache_fpl_aborted(fpl));
5567 }
5568 }
5569
5570 if (*(cnp->cn_nameptr) == '/') {
5571 fpl->dvp = cache_fpl_handle_root(fpl);
5572 fpl->dvp_seqc = vn_seqc_read_any(fpl->dvp);
5573 if (seqc_in_modify(fpl->dvp_seqc)) {
5574 return (cache_fpl_aborted(fpl));
5575 }
5576 /*
5577 * The main loop assumes that ->dvp points to a vnode belonging
5578 * to a filesystem which can do lockless lookup, but the absolute
5579 * symlink can be wandering off to one which does not.
5580 */
5581 mp = atomic_load_ptr(&fpl->dvp->v_mount);
5582 if (__predict_false(mp == NULL)) {
5583 return (cache_fpl_aborted(fpl));
5584 }
5585 if (!cache_fplookup_mp_supported(mp)) {
5586 cache_fpl_checkpoint(fpl);
5587 return (cache_fpl_partial(fpl));
5588 }
5589 if (__predict_false(pwd->pwd_adir != pwd->pwd_rdir)) {
5590 return (cache_fpl_aborted(fpl));
5591 }
5592 }
5593 return (0);
5594 }
5595
5596 static int
cache_fplookup_next(struct cache_fpl * fpl)5597 cache_fplookup_next(struct cache_fpl *fpl)
5598 {
5599 struct componentname *cnp;
5600 struct namecache *ncp;
5601 struct vnode *dvp, *tvp;
5602 u_char nc_flag;
5603 uint32_t hash;
5604 int error;
5605
5606 cnp = fpl->cnp;
5607 dvp = fpl->dvp;
5608 hash = fpl->hash;
5609
5610 if (__predict_false(cnp->cn_nameptr[0] == '.')) {
5611 if (cnp->cn_namelen == 1) {
5612 return (cache_fplookup_dot(fpl));
5613 }
5614 if (cnp->cn_namelen == 2 && cnp->cn_nameptr[1] == '.') {
5615 return (cache_fplookup_dotdot(fpl));
5616 }
5617 }
5618
5619 MPASS(!cache_fpl_isdotdot(cnp));
5620
5621 ncp = cache_ncp_find(dvp, cnp, hash);
5622 if (__predict_false(ncp == NULL)) {
5623 return (cache_fplookup_noentry(fpl));
5624 }
5625
5626 tvp = atomic_load_ptr(&ncp->nc_vp);
5627 nc_flag = atomic_load_char(&ncp->nc_flag);
5628 if ((nc_flag & NCF_NEGATIVE) != 0) {
5629 return (cache_fplookup_neg(fpl, ncp, hash));
5630 }
5631
5632 if (!cache_ncp_canuse(ncp)) {
5633 return (cache_fpl_partial(fpl));
5634 }
5635
5636 fpl->tvp = tvp;
5637 fpl->tvp_seqc = vn_seqc_read_any(tvp);
5638 if (seqc_in_modify(fpl->tvp_seqc)) {
5639 return (cache_fpl_partial(fpl));
5640 }
5641
5642 counter_u64_add(numposhits, 1);
5643 SDT_PROBE3(vfs, namecache, lookup, hit, dvp, ncp->nc_name, tvp);
5644
5645 error = 0;
5646 if (cache_fplookup_is_mp(fpl)) {
5647 error = cache_fplookup_cross_mount(fpl);
5648 }
5649 return (error);
5650 }
5651
5652 static bool
cache_fplookup_mp_supported(struct mount * mp)5653 cache_fplookup_mp_supported(struct mount *mp)
5654 {
5655
5656 MPASS(mp != NULL);
5657 if ((mp->mnt_kern_flag & MNTK_FPLOOKUP) == 0)
5658 return (false);
5659 return (true);
5660 }
5661
5662 /*
5663 * Walk up the mount stack (if any).
5664 *
5665 * Correctness is provided in the following ways:
5666 * - all vnodes are protected from freeing with SMR
5667 * - struct mount objects are type stable making them always safe to access
5668 * - stability of the particular mount is provided by busying it
5669 * - relationship between the vnode which is mounted on and the mount is
5670 * verified with the vnode sequence counter after busying
5671 * - association between root vnode of the mount and the mount is protected
5672 * by busy
5673 *
5674 * From that point on we can read the sequence counter of the root vnode
5675 * and get the next mount on the stack (if any) using the same protection.
5676 *
5677 * By the end of successful walk we are guaranteed the reached state was
5678 * indeed present at least at some point which matches the regular lookup.
5679 */
5680 static int __noinline
cache_fplookup_climb_mount(struct cache_fpl * fpl)5681 cache_fplookup_climb_mount(struct cache_fpl *fpl)
5682 {
5683 struct mount *mp, *prev_mp;
5684 struct mount_pcpu *mpcpu, *prev_mpcpu;
5685 struct vnode *vp;
5686 seqc_t vp_seqc;
5687
5688 vp = fpl->tvp;
5689 vp_seqc = fpl->tvp_seqc;
5690
5691 VNPASS(vp->v_type == VDIR || vp->v_type == VREG || vp->v_type == VBAD, vp);
5692 mp = atomic_load_ptr(&vp->v_mountedhere);
5693 if (__predict_false(mp == NULL)) {
5694 return (0);
5695 }
5696
5697 prev_mp = NULL;
5698 for (;;) {
5699 if (!vfs_op_thread_enter_crit(mp, mpcpu)) {
5700 if (prev_mp != NULL)
5701 vfs_op_thread_exit_crit(prev_mp, prev_mpcpu);
5702 return (cache_fpl_partial(fpl));
5703 }
5704 if (prev_mp != NULL)
5705 vfs_op_thread_exit_crit(prev_mp, prev_mpcpu);
5706 if (!vn_seqc_consistent(vp, vp_seqc)) {
5707 vfs_op_thread_exit_crit(mp, mpcpu);
5708 return (cache_fpl_partial(fpl));
5709 }
5710 if (!cache_fplookup_mp_supported(mp)) {
5711 vfs_op_thread_exit_crit(mp, mpcpu);
5712 return (cache_fpl_partial(fpl));
5713 }
5714 vp = atomic_load_ptr(&mp->mnt_rootvnode);
5715 if (vp == NULL) {
5716 vfs_op_thread_exit_crit(mp, mpcpu);
5717 return (cache_fpl_partial(fpl));
5718 }
5719 vp_seqc = vn_seqc_read_any(vp);
5720 if (seqc_in_modify(vp_seqc)) {
5721 vfs_op_thread_exit_crit(mp, mpcpu);
5722 return (cache_fpl_partial(fpl));
5723 }
5724 prev_mp = mp;
5725 prev_mpcpu = mpcpu;
5726 mp = atomic_load_ptr(&vp->v_mountedhere);
5727 if (mp == NULL)
5728 break;
5729 }
5730
5731 vfs_op_thread_exit_crit(prev_mp, prev_mpcpu);
5732 fpl->tvp = vp;
5733 fpl->tvp_seqc = vp_seqc;
5734 return (0);
5735 }
5736
5737 static int __noinline
cache_fplookup_cross_mount(struct cache_fpl * fpl)5738 cache_fplookup_cross_mount(struct cache_fpl *fpl)
5739 {
5740 struct mount *mp;
5741 struct mount_pcpu *mpcpu;
5742 struct vnode *vp;
5743 seqc_t vp_seqc;
5744
5745 vp = fpl->tvp;
5746 vp_seqc = fpl->tvp_seqc;
5747
5748 VNPASS(vp->v_type == VDIR || vp->v_type == VREG || vp->v_type == VBAD, vp);
5749 mp = atomic_load_ptr(&vp->v_mountedhere);
5750 if (__predict_false(mp == NULL)) {
5751 return (0);
5752 }
5753
5754 if (!vfs_op_thread_enter_crit(mp, mpcpu)) {
5755 return (cache_fpl_partial(fpl));
5756 }
5757 if (!vn_seqc_consistent(vp, vp_seqc)) {
5758 vfs_op_thread_exit_crit(mp, mpcpu);
5759 return (cache_fpl_partial(fpl));
5760 }
5761 if (!cache_fplookup_mp_supported(mp)) {
5762 vfs_op_thread_exit_crit(mp, mpcpu);
5763 return (cache_fpl_partial(fpl));
5764 }
5765 vp = atomic_load_ptr(&mp->mnt_rootvnode);
5766 if (__predict_false(vp == NULL)) {
5767 vfs_op_thread_exit_crit(mp, mpcpu);
5768 return (cache_fpl_partial(fpl));
5769 }
5770 vp_seqc = vn_seqc_read_any(vp);
5771 vfs_op_thread_exit_crit(mp, mpcpu);
5772 if (seqc_in_modify(vp_seqc)) {
5773 return (cache_fpl_partial(fpl));
5774 }
5775 mp = atomic_load_ptr(&vp->v_mountedhere);
5776 if (__predict_false(mp != NULL)) {
5777 /*
5778 * There are possibly more mount points on top.
5779 * Normally this does not happen so for simplicity just start
5780 * over.
5781 */
5782 return (cache_fplookup_climb_mount(fpl));
5783 }
5784
5785 fpl->tvp = vp;
5786 fpl->tvp_seqc = vp_seqc;
5787 return (0);
5788 }
5789
5790 /*
5791 * Check if a vnode is mounted on.
5792 */
5793 static bool
cache_fplookup_is_mp(struct cache_fpl * fpl)5794 cache_fplookup_is_mp(struct cache_fpl *fpl)
5795 {
5796 struct vnode *vp;
5797
5798 vp = fpl->tvp;
5799 return ((vn_irflag_read(vp) & VIRF_MOUNTPOINT) != 0);
5800 }
5801
5802 /*
5803 * Parse the path.
5804 *
5805 * The code was originally copy-pasted from regular lookup and despite
5806 * clean ups leaves performance on the table. Any modifications here
5807 * must take into account that in case off fallback the resulting
5808 * nameidata state has to be compatible with the original.
5809 */
5810
5811 /*
5812 * Debug ni_pathlen tracking.
5813 */
5814 #ifdef INVARIANTS
5815 static void
cache_fpl_pathlen_add(struct cache_fpl * fpl,size_t n)5816 cache_fpl_pathlen_add(struct cache_fpl *fpl, size_t n)
5817 {
5818
5819 fpl->debug.ni_pathlen += n;
5820 KASSERT(fpl->debug.ni_pathlen <= PATH_MAX,
5821 ("%s: pathlen overflow to %zd\n", __func__, fpl->debug.ni_pathlen));
5822 }
5823
5824 static void
cache_fpl_pathlen_sub(struct cache_fpl * fpl,size_t n)5825 cache_fpl_pathlen_sub(struct cache_fpl *fpl, size_t n)
5826 {
5827
5828 fpl->debug.ni_pathlen -= n;
5829 KASSERT(fpl->debug.ni_pathlen <= PATH_MAX,
5830 ("%s: pathlen underflow to %zd\n", __func__, fpl->debug.ni_pathlen));
5831 }
5832
5833 static void
cache_fpl_pathlen_inc(struct cache_fpl * fpl)5834 cache_fpl_pathlen_inc(struct cache_fpl *fpl)
5835 {
5836
5837 cache_fpl_pathlen_add(fpl, 1);
5838 }
5839
5840 static void
cache_fpl_pathlen_dec(struct cache_fpl * fpl)5841 cache_fpl_pathlen_dec(struct cache_fpl *fpl)
5842 {
5843
5844 cache_fpl_pathlen_sub(fpl, 1);
5845 }
5846 #else
5847 static void
cache_fpl_pathlen_add(struct cache_fpl * fpl,size_t n)5848 cache_fpl_pathlen_add(struct cache_fpl *fpl, size_t n)
5849 {
5850 }
5851
5852 static void
cache_fpl_pathlen_sub(struct cache_fpl * fpl,size_t n)5853 cache_fpl_pathlen_sub(struct cache_fpl *fpl, size_t n)
5854 {
5855 }
5856
5857 static void
cache_fpl_pathlen_inc(struct cache_fpl * fpl)5858 cache_fpl_pathlen_inc(struct cache_fpl *fpl)
5859 {
5860 }
5861
5862 static void
cache_fpl_pathlen_dec(struct cache_fpl * fpl)5863 cache_fpl_pathlen_dec(struct cache_fpl *fpl)
5864 {
5865 }
5866 #endif
5867
5868 static void
cache_fplookup_parse(struct cache_fpl * fpl)5869 cache_fplookup_parse(struct cache_fpl *fpl)
5870 {
5871 struct nameidata *ndp;
5872 struct componentname *cnp;
5873 struct vnode *dvp;
5874 char *cp;
5875 uint32_t hash;
5876
5877 ndp = fpl->ndp;
5878 cnp = fpl->cnp;
5879 dvp = fpl->dvp;
5880
5881 /*
5882 * Find the end of this path component, it is either / or nul.
5883 *
5884 * Store / as a temporary sentinel so that we only have one character
5885 * to test for. Pathnames tend to be short so this should not be
5886 * resulting in cache misses.
5887 *
5888 * TODO: fix this to be word-sized.
5889 */
5890 MPASS(&cnp->cn_nameptr[fpl->debug.ni_pathlen - 1] >= cnp->cn_pnbuf);
5891 KASSERT(&cnp->cn_nameptr[fpl->debug.ni_pathlen - 1] == fpl->nulchar,
5892 ("%s: mismatch between pathlen (%zu) and nulchar (%p != %p), string [%s]\n",
5893 __func__, fpl->debug.ni_pathlen, &cnp->cn_nameptr[fpl->debug.ni_pathlen - 1],
5894 fpl->nulchar, cnp->cn_pnbuf));
5895 KASSERT(*fpl->nulchar == '\0',
5896 ("%s: expected nul at %p; string [%s]\n", __func__, fpl->nulchar,
5897 cnp->cn_pnbuf));
5898 hash = cache_get_hash_iter_start(dvp);
5899 *fpl->nulchar = '/';
5900 for (cp = cnp->cn_nameptr; *cp != '/'; cp++) {
5901 KASSERT(*cp != '\0',
5902 ("%s: encountered unexpected nul; string [%s]\n", __func__,
5903 cnp->cn_nameptr));
5904 hash = cache_get_hash_iter(*cp, hash);
5905 continue;
5906 }
5907 *fpl->nulchar = '\0';
5908 fpl->hash = cache_get_hash_iter_finish(hash);
5909
5910 cnp->cn_namelen = cp - cnp->cn_nameptr;
5911 cache_fpl_pathlen_sub(fpl, cnp->cn_namelen);
5912
5913 #ifdef INVARIANTS
5914 /*
5915 * cache_get_hash only accepts lengths up to NAME_MAX. This is fine since
5916 * we are going to fail this lookup with ENAMETOOLONG (see below).
5917 */
5918 if (cnp->cn_namelen <= NAME_MAX) {
5919 if (fpl->hash != cache_get_hash(cnp->cn_nameptr, cnp->cn_namelen, dvp)) {
5920 panic("%s: mismatched hash for [%s] len %ld", __func__,
5921 cnp->cn_nameptr, cnp->cn_namelen);
5922 }
5923 }
5924 #endif
5925
5926 /*
5927 * Hack: we have to check if the found path component's length exceeds
5928 * NAME_MAX. However, the condition is very rarely true and check can
5929 * be elided in the common case -- if an entry was found in the cache,
5930 * then it could not have been too long to begin with.
5931 */
5932 ndp->ni_next = cp;
5933 }
5934
5935 static void
cache_fplookup_parse_advance(struct cache_fpl * fpl)5936 cache_fplookup_parse_advance(struct cache_fpl *fpl)
5937 {
5938 struct nameidata *ndp;
5939 struct componentname *cnp;
5940
5941 ndp = fpl->ndp;
5942 cnp = fpl->cnp;
5943
5944 cnp->cn_nameptr = ndp->ni_next;
5945 KASSERT(*(cnp->cn_nameptr) == '/',
5946 ("%s: should have seen slash at %p ; buf %p [%s]\n", __func__,
5947 cnp->cn_nameptr, cnp->cn_pnbuf, cnp->cn_pnbuf));
5948 cnp->cn_nameptr++;
5949 cache_fpl_pathlen_dec(fpl);
5950 }
5951
5952 /*
5953 * Skip spurious slashes in a pathname (e.g., "foo///bar") and retry.
5954 *
5955 * Lockless lookup tries to elide checking for spurious slashes and should they
5956 * be present is guaranteed to fail to find an entry. In this case the caller
5957 * must check if the name starts with a slash and call this routine. It is
5958 * going to fast forward across the spurious slashes and set the state up for
5959 * retry.
5960 */
5961 static int __noinline
cache_fplookup_skip_slashes(struct cache_fpl * fpl)5962 cache_fplookup_skip_slashes(struct cache_fpl *fpl)
5963 {
5964 struct nameidata *ndp;
5965 struct componentname *cnp;
5966
5967 ndp = fpl->ndp;
5968 cnp = fpl->cnp;
5969
5970 MPASS(*(cnp->cn_nameptr) == '/');
5971 do {
5972 cnp->cn_nameptr++;
5973 cache_fpl_pathlen_dec(fpl);
5974 } while (*(cnp->cn_nameptr) == '/');
5975
5976 /*
5977 * Go back to one slash so that cache_fplookup_parse_advance has
5978 * something to skip.
5979 */
5980 cnp->cn_nameptr--;
5981 cache_fpl_pathlen_inc(fpl);
5982
5983 /*
5984 * cache_fplookup_parse_advance starts from ndp->ni_next
5985 */
5986 ndp->ni_next = cnp->cn_nameptr;
5987
5988 /*
5989 * See cache_fplookup_dot.
5990 */
5991 fpl->tvp = fpl->dvp;
5992 fpl->tvp_seqc = fpl->dvp_seqc;
5993
5994 return (0);
5995 }
5996
5997 /*
5998 * Handle trailing slashes (e.g., "foo/").
5999 *
6000 * If a trailing slash is found the terminal vnode must be a directory.
6001 * Regular lookup shortens the path by nulifying the first trailing slash and
6002 * sets the TRAILINGSLASH flag to denote this took place. There are several
6003 * checks on it performed later.
6004 *
6005 * Similarly to spurious slashes, lockless lookup handles this in a speculative
6006 * manner relying on an invariant that a non-directory vnode will get a miss.
6007 * In this case cn_nameptr[0] == '\0' and cn_namelen == 0.
6008 *
6009 * Thus for a path like "foo/bar/" the code unwinds the state back to "bar/"
6010 * and denotes this is the last path component, which avoids looping back.
6011 *
6012 * Only plain lookups are supported for now to restrict corner cases to handle.
6013 */
6014 static int __noinline
cache_fplookup_trailingslash(struct cache_fpl * fpl)6015 cache_fplookup_trailingslash(struct cache_fpl *fpl)
6016 {
6017 #ifdef INVARIANTS
6018 size_t ni_pathlen;
6019 #endif
6020 struct nameidata *ndp;
6021 struct componentname *cnp;
6022 struct namecache *ncp;
6023 struct vnode *tvp;
6024 char *cn_nameptr_orig, *cn_nameptr_slash;
6025 seqc_t tvp_seqc;
6026 u_char nc_flag;
6027
6028 ndp = fpl->ndp;
6029 cnp = fpl->cnp;
6030 tvp = fpl->tvp;
6031 tvp_seqc = fpl->tvp_seqc;
6032
6033 MPASS(fpl->dvp == fpl->tvp);
6034 KASSERT(cache_fpl_istrailingslash(fpl),
6035 ("%s: expected trailing slash at %p; string [%s]\n", __func__, fpl->nulchar - 1,
6036 cnp->cn_pnbuf));
6037 KASSERT(cnp->cn_nameptr[0] == '\0',
6038 ("%s: expected nul char at %p; string [%s]\n", __func__, &cnp->cn_nameptr[0],
6039 cnp->cn_pnbuf));
6040 KASSERT(cnp->cn_namelen == 0,
6041 ("%s: namelen 0 but got %ld; string [%s]\n", __func__, cnp->cn_namelen,
6042 cnp->cn_pnbuf));
6043 MPASS(cnp->cn_nameptr > cnp->cn_pnbuf);
6044
6045 if (cnp->cn_nameiop != LOOKUP) {
6046 return (cache_fpl_aborted(fpl));
6047 }
6048
6049 if (__predict_false(tvp->v_type != VDIR)) {
6050 if (!vn_seqc_consistent(tvp, tvp_seqc)) {
6051 return (cache_fpl_aborted(fpl));
6052 }
6053 cache_fpl_smr_exit(fpl);
6054 return (cache_fpl_handled_error(fpl, ENOTDIR));
6055 }
6056
6057 /*
6058 * Denote the last component.
6059 */
6060 ndp->ni_next = &cnp->cn_nameptr[0];
6061 MPASS(cache_fpl_islastcn(ndp));
6062
6063 /*
6064 * Unwind trailing slashes.
6065 */
6066 cn_nameptr_orig = cnp->cn_nameptr;
6067 while (cnp->cn_nameptr >= cnp->cn_pnbuf) {
6068 cnp->cn_nameptr--;
6069 if (cnp->cn_nameptr[0] != '/') {
6070 break;
6071 }
6072 }
6073
6074 /*
6075 * Unwind to the beginning of the path component.
6076 *
6077 * Note the path may or may not have started with a slash.
6078 */
6079 cn_nameptr_slash = cnp->cn_nameptr;
6080 while (cnp->cn_nameptr > cnp->cn_pnbuf) {
6081 cnp->cn_nameptr--;
6082 if (cnp->cn_nameptr[0] == '/') {
6083 break;
6084 }
6085 }
6086 if (cnp->cn_nameptr[0] == '/') {
6087 cnp->cn_nameptr++;
6088 }
6089
6090 cnp->cn_namelen = cn_nameptr_slash - cnp->cn_nameptr + 1;
6091 cache_fpl_pathlen_add(fpl, cn_nameptr_orig - cnp->cn_nameptr);
6092 cache_fpl_checkpoint(fpl);
6093
6094 #ifdef INVARIANTS
6095 ni_pathlen = fpl->nulchar - cnp->cn_nameptr + 1;
6096 if (ni_pathlen != fpl->debug.ni_pathlen) {
6097 panic("%s: mismatch (%zu != %zu) nulchar %p nameptr %p [%s] ; full string [%s]\n",
6098 __func__, ni_pathlen, fpl->debug.ni_pathlen, fpl->nulchar,
6099 cnp->cn_nameptr, cnp->cn_nameptr, cnp->cn_pnbuf);
6100 }
6101 #endif
6102
6103 /*
6104 * If this was a "./" lookup the parent directory is already correct.
6105 */
6106 if (cnp->cn_nameptr[0] == '.' && cnp->cn_namelen == 1) {
6107 return (0);
6108 }
6109
6110 /*
6111 * Otherwise we need to look it up.
6112 */
6113 tvp = fpl->tvp;
6114 ncp = atomic_load_consume_ptr(&tvp->v_cache_dd);
6115 if (__predict_false(ncp == NULL)) {
6116 return (cache_fpl_aborted(fpl));
6117 }
6118 nc_flag = atomic_load_char(&ncp->nc_flag);
6119 if ((nc_flag & NCF_ISDOTDOT) != 0) {
6120 return (cache_fpl_aborted(fpl));
6121 }
6122 fpl->dvp = ncp->nc_dvp;
6123 fpl->dvp_seqc = vn_seqc_read_any(fpl->dvp);
6124 if (seqc_in_modify(fpl->dvp_seqc)) {
6125 return (cache_fpl_aborted(fpl));
6126 }
6127 return (0);
6128 }
6129
6130 /*
6131 * See the API contract for VOP_FPLOOKUP_VEXEC.
6132 */
6133 static int __noinline
cache_fplookup_failed_vexec(struct cache_fpl * fpl,int error)6134 cache_fplookup_failed_vexec(struct cache_fpl *fpl, int error)
6135 {
6136 struct componentname *cnp;
6137 struct vnode *dvp;
6138 seqc_t dvp_seqc;
6139
6140 cnp = fpl->cnp;
6141 dvp = fpl->dvp;
6142 dvp_seqc = fpl->dvp_seqc;
6143
6144 /*
6145 * Hack: delayed empty path checking.
6146 */
6147 if (cnp->cn_pnbuf[0] == '\0') {
6148 return (cache_fplookup_emptypath(fpl));
6149 }
6150
6151 /*
6152 * TODO: Due to ignoring trailing slashes lookup will perform a
6153 * permission check on the last dir when it should not be doing it. It
6154 * may fail, but said failure should be ignored. It is possible to fix
6155 * it up fully without resorting to regular lookup, but for now just
6156 * abort.
6157 */
6158 if (cache_fpl_istrailingslash(fpl)) {
6159 return (cache_fpl_aborted(fpl));
6160 }
6161
6162 /*
6163 * Hack: delayed degenerate path checking.
6164 */
6165 if (cnp->cn_nameptr[0] == '\0' && fpl->tvp == NULL) {
6166 return (cache_fplookup_degenerate(fpl));
6167 }
6168
6169 /*
6170 * Hack: delayed name len checking.
6171 */
6172 if (__predict_false(cnp->cn_namelen > NAME_MAX)) {
6173 cache_fpl_smr_exit(fpl);
6174 return (cache_fpl_handled_error(fpl, ENAMETOOLONG));
6175 }
6176
6177 /*
6178 * Hack: they may be looking up foo/bar, where foo is not a directory.
6179 * In such a case we need to return ENOTDIR, but we may happen to get
6180 * here with a different error.
6181 */
6182 if (dvp->v_type != VDIR) {
6183 error = ENOTDIR;
6184 }
6185
6186 /*
6187 * Hack: handle O_SEARCH.
6188 *
6189 * Open Group Base Specifications Issue 7, 2018 edition states:
6190 * <quote>
6191 * If the access mode of the open file description associated with the
6192 * file descriptor is not O_SEARCH, the function shall check whether
6193 * directory searches are permitted using the current permissions of
6194 * the directory underlying the file descriptor. If the access mode is
6195 * O_SEARCH, the function shall not perform the check.
6196 * </quote>
6197 *
6198 * Regular lookup tests for the NOEXECCHECK flag for every path
6199 * component to decide whether to do the permission check. However,
6200 * since most lookups never have the flag (and when they do it is only
6201 * present for the first path component), lockless lookup only acts on
6202 * it if there is a permission problem. Here the flag is represented
6203 * with a boolean so that we don't have to clear it on the way out.
6204 *
6205 * For simplicity this always aborts.
6206 * TODO: check if this is the first lookup and ignore the permission
6207 * problem. Note the flag has to survive fallback (if it happens to be
6208 * performed).
6209 */
6210 if (fpl->fsearch) {
6211 return (cache_fpl_aborted(fpl));
6212 }
6213
6214 switch (error) {
6215 case EAGAIN:
6216 if (!vn_seqc_consistent(dvp, dvp_seqc)) {
6217 error = cache_fpl_aborted(fpl);
6218 } else {
6219 cache_fpl_partial(fpl);
6220 }
6221 break;
6222 default:
6223 if (!vn_seqc_consistent(dvp, dvp_seqc)) {
6224 error = cache_fpl_aborted(fpl);
6225 } else {
6226 cache_fpl_smr_exit(fpl);
6227 cache_fpl_handled_error(fpl, error);
6228 }
6229 break;
6230 }
6231 return (error);
6232 }
6233
6234 static int
cache_fplookup_impl(struct vnode * dvp,struct cache_fpl * fpl)6235 cache_fplookup_impl(struct vnode *dvp, struct cache_fpl *fpl)
6236 {
6237 struct nameidata *ndp;
6238 struct componentname *cnp;
6239 struct mount *mp;
6240 int error;
6241
6242 ndp = fpl->ndp;
6243 cnp = fpl->cnp;
6244
6245 cache_fpl_checkpoint(fpl);
6246
6247 /*
6248 * The vnode at hand is almost always stable, skip checking for it.
6249 * Worst case this postpones the check towards the end of the iteration
6250 * of the main loop.
6251 */
6252 fpl->dvp = dvp;
6253 fpl->dvp_seqc = vn_seqc_read_notmodify(fpl->dvp);
6254
6255 mp = atomic_load_ptr(&dvp->v_mount);
6256 if (__predict_false(mp == NULL || !cache_fplookup_mp_supported(mp))) {
6257 return (cache_fpl_aborted(fpl));
6258 }
6259
6260 MPASS(fpl->tvp == NULL);
6261
6262 for (;;) {
6263 cache_fplookup_parse(fpl);
6264
6265 error = VOP_FPLOOKUP_VEXEC(fpl->dvp, cnp->cn_cred);
6266 if (__predict_false(error != 0)) {
6267 error = cache_fplookup_failed_vexec(fpl, error);
6268 break;
6269 }
6270
6271 error = cache_fplookup_next(fpl);
6272 if (__predict_false(cache_fpl_terminated(fpl))) {
6273 break;
6274 }
6275
6276 VNPASS(!seqc_in_modify(fpl->tvp_seqc), fpl->tvp);
6277
6278 if (fpl->tvp->v_type == VLNK) {
6279 error = cache_fplookup_symlink(fpl);
6280 if (cache_fpl_terminated(fpl)) {
6281 break;
6282 }
6283 } else {
6284 if (cache_fpl_islastcn(ndp)) {
6285 error = cache_fplookup_final(fpl);
6286 break;
6287 }
6288
6289 if (!vn_seqc_consistent(fpl->dvp, fpl->dvp_seqc)) {
6290 error = cache_fpl_aborted(fpl);
6291 break;
6292 }
6293
6294 fpl->dvp = fpl->tvp;
6295 fpl->dvp_seqc = fpl->tvp_seqc;
6296 cache_fplookup_parse_advance(fpl);
6297 }
6298
6299 cache_fpl_checkpoint(fpl);
6300 }
6301
6302 return (error);
6303 }
6304
6305 /*
6306 * Fast path lookup protected with SMR and sequence counters.
6307 *
6308 * Note: all VOP_FPLOOKUP_VEXEC routines have a comment referencing this one.
6309 *
6310 * Filesystems can opt in by setting the MNTK_FPLOOKUP flag and meeting criteria
6311 * outlined at the end.
6312 *
6313 * Traversing from one vnode to another requires atomicity with regard to
6314 * permissions, mount points and of course their relative placement (if you are
6315 * looking up "bar" in "foo" and you found it, it better be in that directory
6316 * at the time).
6317 *
6318 * Normally this is accomplished with locking, but it comes with a significant
6319 * performance hit and is untenable as a fast path even in a moderate core
6320 * count environment (at the time of writing this comment this would be a
6321 * little south of 100).
6322 *
6323 * The same guarantee can be provided with a combination of safe memory
6324 * reclamation and sequence counters instead. If all operations which affect
6325 * the relationship between the current vnode and the one we are looking for
6326 * also modify the counter, we can verify whether all the conditions held as
6327 * we made the jump.
6328 *
6329 * See places which issue vn_seqc_write_begin()/vn_seqc_write_end() for
6330 * operations affected.
6331 *
6332 * Suppose the variable "cnp" contains lookup metadata (the path etc.), then
6333 * locked lookup conceptually looks like this:
6334 *
6335 * // lock the current directory
6336 * vn_lock(dvp);
6337 * for (;;) {
6338 * // permission check
6339 * if (!canlookup(dvp, cnp))
6340 * abort();
6341 * // look for the target name inside dvp
6342 * tvp = findnext(dvp, cnp);
6343 * vn_lock(tvp);
6344 * // tvp is still guaranteed to be inside of dvp because of the lock on dvp
6345 * vn_unlock(dvp);
6346 * // dvp is unlocked. its state is now arbitrary, but that's fine as we
6347 * // made the jump while everything relevant was correct, continue with tvp
6348 * // as the directory to look up names in
6349 * tvp = dvp;
6350 * if (last)
6351 * break;
6352 * // if not last loop back and continue until done
6353 * }
6354 * vget(tvp);
6355 * return (tvp);
6356 *
6357 * Lockless lookup replaces locking with sequence counter checks:
6358 *
6359 * vfs_smr_enter();
6360 * dvp_seqc = seqc_read_any(dvp);
6361 * // fail if someone is altering the directory vnode
6362 * if (seqc_in_modify(dvp_seqc))
6363 * abort();
6364 * for (;;) {
6365 * // permission check. note it can race, but we will validate the outcome
6366 * // with a seqc
6367 * if (!canlookup_smr(dvp, cnp)) {
6368 * // has dvp changed from under us? if so, the denial may be invalid
6369 * if (!seqc_consistent(dvp, dvp_seqc)
6370 * fallback_to_locked();
6371 * // nothing changed, lookup denial is valid
6372 * fail();
6373 * }
6374 * // look for the target name inside dvp
6375 * tvp = findnext(dvp, cnp);
6376 * tvp_seqc = seqc_read_any(tvp);
6377 * // bail if someone is altering the target vnode
6378 * if (seqc_in_modify(tvp_seqc))
6379 * fallback_to_locked();
6380 * // bail if someone is altering the directory vnode
6381 * if (!seqc_consistent(dvp, dvp_seqc)
6382 * fallback_to_locked();
6383 * // we confirmed neither dvp nor tvp changed while we were making the
6384 * // jump to the next component, thus the result is the same as if we
6385 * // held the lock on dvp and tvp the entire time, continue with tvp
6386 * // as the directory to look up names in
6387 * dvp = tvp;
6388 * dvp_seqc = tvp_seqc;
6389 * if (last)
6390 * break;
6391 * }
6392 * vget(); // secure the vnode
6393 * if (!seqc_consistent(tvp, tvp_seqc) // final check
6394 * fallback_to_locked();
6395 * // at this point we know nothing has changed for any parent<->child pair
6396 * // as they were crossed during the lookup, meaning we matched the guarantee
6397 * // of the locked variant
6398 * return (tvp);
6399 *
6400 * The API contract for VOP_FPLOOKUP_VEXEC routines is as follows:
6401 * - they are called while within vfs_smr protection which they must never exit
6402 * - EAGAIN can be returned to denote checking could not be performed, it is
6403 * always valid to return it
6404 * - if the sequence counter has not changed the result must be valid
6405 * - if the sequence counter has changed both false positives and false negatives
6406 * are permitted (since the result will be rejected later)
6407 * - for simple cases of unix permission checks vaccess_vexec_smr can be used
6408 *
6409 * Caveats to watch out for:
6410 * - vnodes are passed unlocked and unreferenced with nothing stopping
6411 * VOP_RECLAIM, in turn meaning that ->v_data can become NULL. It is advised
6412 * to use atomic_load_ptr to fetch it.
6413 * - the aforementioned object can also get freed, meaning absent other means it
6414 * should be protected with vfs_smr
6415 * - either safely checking permissions as they are modified or guaranteeing
6416 * their stability is left to the routine
6417 */
6418 int
cache_fplookup(struct nameidata * ndp,enum cache_fpl_status * status,struct pwd ** pwdp)6419 cache_fplookup(struct nameidata *ndp, enum cache_fpl_status *status,
6420 struct pwd **pwdp)
6421 {
6422 struct cache_fpl fpl;
6423 struct pwd *pwd;
6424 struct vnode *dvp;
6425 struct componentname *cnp;
6426 int error;
6427
6428 fpl.status = CACHE_FPL_STATUS_UNSET;
6429 fpl.in_smr = false;
6430 fpl.ndp = ndp;
6431 fpl.cnp = cnp = &ndp->ni_cnd;
6432 MPASS(ndp->ni_lcf == 0);
6433 KASSERT ((cnp->cn_flags & CACHE_FPL_INTERNAL_CN_FLAGS) == 0,
6434 ("%s: internal flags found in cn_flags %" PRIx64, __func__,
6435 cnp->cn_flags));
6436 MPASS(cnp->cn_nameptr == cnp->cn_pnbuf);
6437 MPASS(ndp->ni_resflags == 0);
6438
6439 if (__predict_false(!cache_can_fplookup(&fpl))) {
6440 *status = fpl.status;
6441 SDT_PROBE3(vfs, fplookup, lookup, done, ndp, fpl.line, fpl.status);
6442 return (EOPNOTSUPP);
6443 }
6444
6445 cache_fpl_checkpoint_outer(&fpl);
6446
6447 cache_fpl_smr_enter_initial(&fpl);
6448 #ifdef INVARIANTS
6449 fpl.debug.ni_pathlen = ndp->ni_pathlen;
6450 #endif
6451 fpl.nulchar = &cnp->cn_nameptr[ndp->ni_pathlen - 1];
6452 fpl.fsearch = false;
6453 fpl.tvp = NULL; /* for degenerate path handling */
6454 fpl.pwd = pwdp;
6455 pwd = pwd_get_smr();
6456 *(fpl.pwd) = pwd;
6457 namei_setup_rootdir(ndp, cnp, pwd);
6458 ndp->ni_topdir = pwd->pwd_jdir;
6459
6460 if (cnp->cn_pnbuf[0] == '/') {
6461 dvp = cache_fpl_handle_root(&fpl);
6462 ndp->ni_resflags = NIRES_ABS;
6463 } else {
6464 if (ndp->ni_dirfd == AT_FDCWD) {
6465 dvp = pwd->pwd_cdir;
6466 } else {
6467 error = cache_fplookup_dirfd(&fpl, &dvp);
6468 if (__predict_false(error != 0)) {
6469 goto out;
6470 }
6471 }
6472 }
6473
6474 SDT_PROBE4(vfs, namei, lookup, entry, dvp, cnp->cn_pnbuf, cnp->cn_flags, true);
6475 error = cache_fplookup_impl(dvp, &fpl);
6476 out:
6477 cache_fpl_smr_assert_not_entered(&fpl);
6478 cache_fpl_assert_status(&fpl);
6479 *status = fpl.status;
6480 SDT_PROBE3(vfs, fplookup, lookup, done, ndp, fpl.line, fpl.status);
6481 if (__predict_true(fpl.status == CACHE_FPL_STATUS_HANDLED)) {
6482 MPASS(error != CACHE_FPL_FAILED);
6483 SDT_PROBE4(vfs, namei, lookup, return, error, ndp->ni_vp, true,
6484 ndp);
6485 if (error != 0) {
6486 cache_fpl_cleanup_cnp(fpl.cnp);
6487 MPASS(fpl.dvp == NULL);
6488 MPASS(fpl.tvp == NULL);
6489 }
6490 ndp->ni_dvp = fpl.dvp;
6491 ndp->ni_vp = fpl.tvp;
6492 }
6493 return (error);
6494 }
6495