xref: /freebsd/sys/kern/vfs_cache.c (revision d500a85e640d1cd270747c12e17c511b53864436)
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  *	@(#)vfs_cache.c	8.5 (Berkeley) 3/22/95
35  */
36 
37 #include <sys/cdefs.h>
38 __FBSDID("$FreeBSD$");
39 
40 #include "opt_ddb.h"
41 #include "opt_ktrace.h"
42 
43 #include <sys/param.h>
44 #include <sys/systm.h>
45 #include <sys/capsicum.h>
46 #include <sys/counter.h>
47 #include <sys/filedesc.h>
48 #include <sys/fnv_hash.h>
49 #include <sys/kernel.h>
50 #include <sys/ktr.h>
51 #include <sys/lock.h>
52 #include <sys/malloc.h>
53 #include <sys/fcntl.h>
54 #include <sys/jail.h>
55 #include <sys/mount.h>
56 #include <sys/namei.h>
57 #include <sys/proc.h>
58 #include <sys/seqc.h>
59 #include <sys/sdt.h>
60 #include <sys/smr.h>
61 #include <sys/smp.h>
62 #include <sys/syscallsubr.h>
63 #include <sys/sysctl.h>
64 #include <sys/sysproto.h>
65 #include <sys/vnode.h>
66 #include <ck_queue.h>
67 #ifdef KTRACE
68 #include <sys/ktrace.h>
69 #endif
70 #ifdef INVARIANTS
71 #include <machine/_inttypes.h>
72 #endif
73 
74 #include <sys/capsicum.h>
75 
76 #include <security/audit/audit.h>
77 #include <security/mac/mac_framework.h>
78 
79 #ifdef DDB
80 #include <ddb/ddb.h>
81 #endif
82 
83 #include <vm/uma.h>
84 
85 /*
86  * High level overview of name caching in the VFS layer.
87  *
88  * Originally caching was implemented as part of UFS, later extracted to allow
89  * use by other filesystems. A decision was made to make it optional and
90  * completely detached from the rest of the kernel, which comes with limitations
91  * outlined near the end of this comment block.
92  *
93  * This fundamental choice needs to be revisited. In the meantime, the current
94  * state is described below. Significance of all notable routines is explained
95  * in comments placed above their implementation. Scattered thoroughout the
96  * file are TODO comments indicating shortcomings which can be fixed without
97  * reworking everything (most of the fixes will likely be reusable). Various
98  * details are omitted from this explanation to not clutter the overview, they
99  * have to be checked by reading the code and associated commentary.
100  *
101  * Keep in mind that it's individual path components which are cached, not full
102  * paths. That is, for a fully cached path "foo/bar/baz" there are 3 entries,
103  * one for each name.
104  *
105  * I. Data organization
106  *
107  * Entries are described by "struct namecache" objects and stored in a hash
108  * table. See cache_get_hash for more information.
109  *
110  * "struct vnode" contains pointers to source entries (names which can be found
111  * when traversing through said vnode), destination entries (names of that
112  * vnode (see "Limitations" for a breakdown on the subject) and a pointer to
113  * the parent vnode.
114  *
115  * The (directory vnode; name) tuple reliably determines the target entry if
116  * it exists.
117  *
118  * Since there are no small locks at this time (all are 32 bytes in size on
119  * LP64), the code works around the problem by introducing lock arrays to
120  * protect hash buckets and vnode lists.
121  *
122  * II. Filesystem integration
123  *
124  * Filesystems participating in name caching do the following:
125  * - set vop_lookup routine to vfs_cache_lookup
126  * - set vop_cachedlookup to whatever can perform the lookup if the above fails
127  * - if they support lockless lookup (see below), vop_fplookup_vexec and
128  *   vop_fplookup_symlink are set along with the MNTK_FPLOOKUP flag on the
129  *   mount point
130  * - call cache_purge or cache_vop_* routines to eliminate stale entries as
131  *   applicable
132  * - call cache_enter to add entries depending on the MAKEENTRY flag
133  *
134  * With the above in mind, there are 2 entry points when doing lookups:
135  * - ... -> namei -> cache_fplookup -- this is the default
136  * - ... -> VOP_LOOKUP -> vfs_cache_lookup -- normally only called by namei
137  *   should the above fail
138  *
139  * Example code flow how an entry is added:
140  * ... -> namei -> cache_fplookup -> cache_fplookup_noentry -> VOP_LOOKUP ->
141  * vfs_cache_lookup -> VOP_CACHEDLOOKUP -> ufs_lookup_ino -> cache_enter
142  *
143  * III. Performance considerations
144  *
145  * For lockless case forward lookup avoids any writes to shared areas apart
146  * from the terminal path component. In other words non-modifying lookups of
147  * different files don't suffer any scalability problems in the namecache.
148  * Looking up the same file is limited by VFS and goes beyond the scope of this
149  * file.
150  *
151  * At least on amd64 the single-threaded bottleneck for long paths is hashing
152  * (see cache_get_hash). There are cases where the code issues acquire fence
153  * multiple times, they can be combined on architectures which suffer from it.
154  *
155  * For locked case each encountered vnode has to be referenced and locked in
156  * order to be handed out to the caller (normally that's namei). This
157  * introduces significant hit single-threaded and serialization multi-threaded.
158  *
159  * Reverse lookup (e.g., "getcwd") fully scales provided it is fully cached --
160  * avoids any writes to shared areas to any components.
161  *
162  * Unrelated insertions are partially serialized on updating the global entry
163  * counter and possibly serialized on colliding bucket or vnode locks.
164  *
165  * IV. Observability
166  *
167  * Note not everything has an explicit dtrace probe nor it should have, thus
168  * some of the one-liners below depend on implementation details.
169  *
170  * Examples:
171  *
172  * # Check what lookups failed to be handled in a lockless manner. Column 1 is
173  * # line number, column 2 is status code (see cache_fpl_status)
174  * dtrace -n 'vfs:fplookup:lookup:done { @[arg1, arg2] = count(); }'
175  *
176  * # Lengths of names added by binary name
177  * dtrace -n 'fbt::cache_enter_time:entry { @[execname] = quantize(args[2]->cn_namelen); }'
178  *
179  * # Same as above but only those which exceed 64 characters
180  * dtrace -n 'fbt::cache_enter_time:entry /args[2]->cn_namelen > 64/ { @[execname] = quantize(args[2]->cn_namelen); }'
181  *
182  * # Who is performing lookups with spurious slashes (e.g., "foo//bar") and what
183  * # path is it
184  * dtrace -n 'fbt::cache_fplookup_skip_slashes:entry { @[execname, stringof(args[0]->cnp->cn_pnbuf)] = count(); }'
185  *
186  * V. Limitations and implementation defects
187  *
188  * - since it is possible there is no entry for an open file, tools like
189  *   "procstat" may fail to resolve fd -> vnode -> path to anything
190  * - even if a filesystem adds an entry, it may get purged (e.g., due to memory
191  *   shortage) in which case the above problem applies
192  * - hardlinks are not tracked, thus if a vnode is reachable in more than one
193  *   way, resolving a name may return a different path than the one used to
194  *   open it (even if said path is still valid)
195  * - by default entries are not added for newly created files
196  * - adding an entry may need to evict negative entry first, which happens in 2
197  *   distinct places (evicting on lookup, adding in a later VOP) making it
198  *   impossible to simply reuse it
199  * - there is a simple scheme to evict negative entries as the cache is approaching
200  *   its capacity, but it is very unclear if doing so is a good idea to begin with
201  * - vnodes are subject to being recycled even if target inode is left in memory,
202  *   which loses the name cache entries when it perhaps should not. in case of tmpfs
203  *   names get duplicated -- kept by filesystem itself and namecache separately
204  * - struct namecache has a fixed size and comes in 2 variants, often wasting space.
205  *   now hard to replace with malloc due to dependence on SMR.
206  * - lack of better integration with the kernel also turns nullfs into a layered
207  *   filesystem instead of something which can take advantage of caching
208  */
209 
210 static SYSCTL_NODE(_vfs, OID_AUTO, cache, CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
211     "Name cache");
212 
213 SDT_PROVIDER_DECLARE(vfs);
214 SDT_PROBE_DEFINE3(vfs, namecache, enter, done, "struct vnode *", "char *",
215     "struct vnode *");
216 SDT_PROBE_DEFINE3(vfs, namecache, enter, duplicate, "struct vnode *", "char *",
217     "struct vnode *");
218 SDT_PROBE_DEFINE2(vfs, namecache, enter_negative, done, "struct vnode *",
219     "char *");
220 SDT_PROBE_DEFINE2(vfs, namecache, fullpath_smr, hit, "struct vnode *",
221     "const char *");
222 SDT_PROBE_DEFINE4(vfs, namecache, fullpath_smr, miss, "struct vnode *",
223     "struct namecache *", "int", "int");
224 SDT_PROBE_DEFINE1(vfs, namecache, fullpath, entry, "struct vnode *");
225 SDT_PROBE_DEFINE3(vfs, namecache, fullpath, hit, "struct vnode *",
226     "char *", "struct vnode *");
227 SDT_PROBE_DEFINE1(vfs, namecache, fullpath, miss, "struct vnode *");
228 SDT_PROBE_DEFINE3(vfs, namecache, fullpath, return, "int",
229     "struct vnode *", "char *");
230 SDT_PROBE_DEFINE3(vfs, namecache, lookup, hit, "struct vnode *", "char *",
231     "struct vnode *");
232 SDT_PROBE_DEFINE2(vfs, namecache, lookup, hit__negative,
233     "struct vnode *", "char *");
234 SDT_PROBE_DEFINE2(vfs, namecache, lookup, miss, "struct vnode *",
235     "char *");
236 SDT_PROBE_DEFINE2(vfs, namecache, removecnp, hit, "struct vnode *",
237     "struct componentname *");
238 SDT_PROBE_DEFINE2(vfs, namecache, removecnp, miss, "struct vnode *",
239     "struct componentname *");
240 SDT_PROBE_DEFINE1(vfs, namecache, purge, done, "struct vnode *");
241 SDT_PROBE_DEFINE1(vfs, namecache, purge, batch, "int");
242 SDT_PROBE_DEFINE1(vfs, namecache, purge_negative, done, "struct vnode *");
243 SDT_PROBE_DEFINE1(vfs, namecache, purgevfs, done, "struct mount *");
244 SDT_PROBE_DEFINE3(vfs, namecache, zap, done, "struct vnode *", "char *",
245     "struct vnode *");
246 SDT_PROBE_DEFINE2(vfs, namecache, zap_negative, done, "struct vnode *",
247     "char *");
248 SDT_PROBE_DEFINE2(vfs, namecache, evict_negative, done, "struct vnode *",
249     "char *");
250 SDT_PROBE_DEFINE1(vfs, namecache, symlink, alloc__fail, "size_t");
251 
252 SDT_PROBE_DEFINE3(vfs, fplookup, lookup, done, "struct nameidata", "int", "bool");
253 SDT_PROBE_DECLARE(vfs, namei, lookup, entry);
254 SDT_PROBE_DECLARE(vfs, namei, lookup, return);
255 
256 /*
257  * This structure describes the elements in the cache of recent
258  * names looked up by namei.
259  */
260 struct negstate {
261 	u_char neg_flag;
262 	u_char neg_hit;
263 };
264 _Static_assert(sizeof(struct negstate) <= sizeof(struct vnode *),
265     "the state must fit in a union with a pointer without growing it");
266 
267 struct	namecache {
268 	LIST_ENTRY(namecache) nc_src;	/* source vnode list */
269 	TAILQ_ENTRY(namecache) nc_dst;	/* destination vnode list */
270 	CK_SLIST_ENTRY(namecache) nc_hash;/* hash chain */
271 	struct	vnode *nc_dvp;		/* vnode of parent of name */
272 	union {
273 		struct	vnode *nu_vp;	/* vnode the name refers to */
274 		struct	negstate nu_neg;/* negative entry state */
275 	} n_un;
276 	u_char	nc_flag;		/* flag bits */
277 	u_char	nc_nlen;		/* length of name */
278 	char	nc_name[0];		/* segment name + nul */
279 };
280 
281 /*
282  * struct namecache_ts repeats struct namecache layout up to the
283  * nc_nlen member.
284  * struct namecache_ts is used in place of struct namecache when time(s) need
285  * to be stored.  The nc_dotdottime field is used when a cache entry is mapping
286  * both a non-dotdot directory name plus dotdot for the directory's
287  * parent.
288  *
289  * See below for alignment requirement.
290  */
291 struct	namecache_ts {
292 	struct	timespec nc_time;	/* timespec provided by fs */
293 	struct	timespec nc_dotdottime;	/* dotdot timespec provided by fs */
294 	int	nc_ticks;		/* ticks value when entry was added */
295 	int	nc_pad;
296 	struct namecache nc_nc;
297 };
298 
299 TAILQ_HEAD(cache_freebatch, namecache);
300 
301 /*
302  * At least mips n32 performs 64-bit accesses to timespec as found
303  * in namecache_ts and requires them to be aligned. Since others
304  * may be in the same spot suffer a little bit and enforce the
305  * alignment for everyone. Note this is a nop for 64-bit platforms.
306  */
307 #define CACHE_ZONE_ALIGNMENT	UMA_ALIGNOF(time_t)
308 
309 /*
310  * TODO: the initial value of CACHE_PATH_CUTOFF was inherited from the
311  * 4.4 BSD codebase. Later on struct namecache was tweaked to become
312  * smaller and the value was bumped to retain the total size, but it
313  * was never re-evaluated for suitability. A simple test counting
314  * lengths during package building shows that the value of 45 covers
315  * about 86% of all added entries, reaching 99% at 65.
316  *
317  * Regardless of the above, use of dedicated zones instead of malloc may be
318  * inducing additional waste. This may be hard to address as said zones are
319  * tied to VFS SMR. Even if retaining them, the current split should be
320  * re-evaluated.
321  */
322 #ifdef __LP64__
323 #define	CACHE_PATH_CUTOFF	45
324 #define	CACHE_LARGE_PAD		6
325 #else
326 #define	CACHE_PATH_CUTOFF	41
327 #define	CACHE_LARGE_PAD		2
328 #endif
329 
330 #define CACHE_ZONE_SMALL_SIZE		(offsetof(struct namecache, nc_name) + CACHE_PATH_CUTOFF + 1)
331 #define CACHE_ZONE_SMALL_TS_SIZE	(offsetof(struct namecache_ts, nc_nc) + CACHE_ZONE_SMALL_SIZE)
332 #define CACHE_ZONE_LARGE_SIZE		(offsetof(struct namecache, nc_name) + NAME_MAX + 1 + CACHE_LARGE_PAD)
333 #define CACHE_ZONE_LARGE_TS_SIZE	(offsetof(struct namecache_ts, nc_nc) + CACHE_ZONE_LARGE_SIZE)
334 
335 _Static_assert((CACHE_ZONE_SMALL_SIZE % (CACHE_ZONE_ALIGNMENT + 1)) == 0, "bad zone size");
336 _Static_assert((CACHE_ZONE_SMALL_TS_SIZE % (CACHE_ZONE_ALIGNMENT + 1)) == 0, "bad zone size");
337 _Static_assert((CACHE_ZONE_LARGE_SIZE % (CACHE_ZONE_ALIGNMENT + 1)) == 0, "bad zone size");
338 _Static_assert((CACHE_ZONE_LARGE_TS_SIZE % (CACHE_ZONE_ALIGNMENT + 1)) == 0, "bad zone size");
339 
340 #define	nc_vp		n_un.nu_vp
341 #define	nc_neg		n_un.nu_neg
342 
343 /*
344  * Flags in namecache.nc_flag
345  */
346 #define NCF_WHITE	0x01
347 #define NCF_ISDOTDOT	0x02
348 #define	NCF_TS		0x04
349 #define	NCF_DTS		0x08
350 #define	NCF_DVDROP	0x10
351 #define	NCF_NEGATIVE	0x20
352 #define	NCF_INVALID	0x40
353 #define	NCF_WIP		0x80
354 
355 /*
356  * Flags in negstate.neg_flag
357  */
358 #define NEG_HOT		0x01
359 
360 static bool	cache_neg_evict_cond(u_long lnumcache);
361 
362 /*
363  * Mark an entry as invalid.
364  *
365  * This is called before it starts getting deconstructed.
366  */
367 static void
368 cache_ncp_invalidate(struct namecache *ncp)
369 {
370 
371 	KASSERT((ncp->nc_flag & NCF_INVALID) == 0,
372 	    ("%s: entry %p already invalid", __func__, ncp));
373 	atomic_store_char(&ncp->nc_flag, ncp->nc_flag | NCF_INVALID);
374 	atomic_thread_fence_rel();
375 }
376 
377 /*
378  * Check whether the entry can be safely used.
379  *
380  * All places which elide locks are supposed to call this after they are
381  * done with reading from an entry.
382  */
383 #define cache_ncp_canuse(ncp)	({					\
384 	struct namecache *_ncp = (ncp);					\
385 	u_char _nc_flag;						\
386 									\
387 	atomic_thread_fence_acq();					\
388 	_nc_flag = atomic_load_char(&_ncp->nc_flag);			\
389 	__predict_true((_nc_flag & (NCF_INVALID | NCF_WIP)) == 0);	\
390 })
391 
392 /*
393  * Like the above but also checks NCF_WHITE.
394  */
395 #define cache_fpl_neg_ncp_canuse(ncp)	({				\
396 	struct namecache *_ncp = (ncp);					\
397 	u_char _nc_flag;						\
398 									\
399 	atomic_thread_fence_acq();					\
400 	_nc_flag = atomic_load_char(&_ncp->nc_flag);			\
401 	__predict_true((_nc_flag & (NCF_INVALID | NCF_WIP | NCF_WHITE)) == 0);	\
402 })
403 
404 VFS_SMR_DECLARE;
405 
406 static SYSCTL_NODE(_vfs_cache, OID_AUTO, param, CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
407     "Name cache parameters");
408 
409 static u_int __read_mostly	ncsize; /* the size as computed on creation or resizing */
410 SYSCTL_UINT(_vfs_cache_param, OID_AUTO, size, CTLFLAG_RW, &ncsize, 0,
411     "Total namecache capacity");
412 
413 u_int ncsizefactor = 2;
414 SYSCTL_UINT(_vfs_cache_param, OID_AUTO, sizefactor, CTLFLAG_RW, &ncsizefactor, 0,
415     "Size factor for namecache");
416 
417 static u_long __read_mostly	ncnegfactor = 5; /* ratio of negative entries */
418 SYSCTL_ULONG(_vfs_cache_param, OID_AUTO, negfactor, CTLFLAG_RW, &ncnegfactor, 0,
419     "Ratio of negative namecache entries");
420 
421 /*
422  * Negative entry % of namecache capacity above which automatic eviction is allowed.
423  *
424  * Check cache_neg_evict_cond for details.
425  */
426 static u_int ncnegminpct = 3;
427 
428 static u_int __read_mostly     neg_min; /* the above recomputed against ncsize */
429 SYSCTL_UINT(_vfs_cache_param, OID_AUTO, negmin, CTLFLAG_RD, &neg_min, 0,
430     "Negative entry count above which automatic eviction is allowed");
431 
432 /*
433  * Structures associated with name caching.
434  */
435 #define NCHHASH(hash) \
436 	(&nchashtbl[(hash) & nchash])
437 static __read_mostly CK_SLIST_HEAD(nchashhead, namecache) *nchashtbl;/* Hash Table */
438 static u_long __read_mostly	nchash;			/* size of hash table */
439 SYSCTL_ULONG(_debug, OID_AUTO, nchash, CTLFLAG_RD, &nchash, 0,
440     "Size of namecache hash table");
441 static u_long __exclusive_cache_line	numneg;	/* number of negative entries allocated */
442 static u_long __exclusive_cache_line	numcache;/* number of cache entries allocated */
443 
444 struct nchstats	nchstats;		/* cache effectiveness statistics */
445 
446 static bool __read_frequently cache_fast_revlookup = true;
447 SYSCTL_BOOL(_vfs, OID_AUTO, cache_fast_revlookup, CTLFLAG_RW,
448     &cache_fast_revlookup, 0, "");
449 
450 static bool __read_mostly cache_rename_add = true;
451 SYSCTL_BOOL(_vfs, OID_AUTO, cache_rename_add, CTLFLAG_RW,
452     &cache_rename_add, 0, "");
453 
454 static u_int __exclusive_cache_line neg_cycle;
455 
456 #define ncneghash	3
457 #define	numneglists	(ncneghash + 1)
458 
459 struct neglist {
460 	struct mtx		nl_evict_lock;
461 	struct mtx		nl_lock __aligned(CACHE_LINE_SIZE);
462 	TAILQ_HEAD(, namecache) nl_list;
463 	TAILQ_HEAD(, namecache) nl_hotlist;
464 	u_long			nl_hotnum;
465 } __aligned(CACHE_LINE_SIZE);
466 
467 static struct neglist neglists[numneglists];
468 
469 static inline struct neglist *
470 NCP2NEGLIST(struct namecache *ncp)
471 {
472 
473 	return (&neglists[(((uintptr_t)(ncp) >> 8) & ncneghash)]);
474 }
475 
476 static inline struct negstate *
477 NCP2NEGSTATE(struct namecache *ncp)
478 {
479 
480 	MPASS(atomic_load_char(&ncp->nc_flag) & NCF_NEGATIVE);
481 	return (&ncp->nc_neg);
482 }
483 
484 #define	numbucketlocks (ncbuckethash + 1)
485 static u_int __read_mostly  ncbuckethash;
486 static struct mtx_padalign __read_mostly  *bucketlocks;
487 #define	HASH2BUCKETLOCK(hash) \
488 	((struct mtx *)(&bucketlocks[((hash) & ncbuckethash)]))
489 
490 #define	numvnodelocks (ncvnodehash + 1)
491 static u_int __read_mostly  ncvnodehash;
492 static struct mtx __read_mostly *vnodelocks;
493 static inline struct mtx *
494 VP2VNODELOCK(struct vnode *vp)
495 {
496 
497 	return (&vnodelocks[(((uintptr_t)(vp) >> 8) & ncvnodehash)]);
498 }
499 
500 static void
501 cache_out_ts(struct namecache *ncp, struct timespec *tsp, int *ticksp)
502 {
503 	struct namecache_ts *ncp_ts;
504 
505 	KASSERT((ncp->nc_flag & NCF_TS) != 0 ||
506 	    (tsp == NULL && ticksp == NULL),
507 	    ("No NCF_TS"));
508 
509 	if (tsp == NULL)
510 		return;
511 
512 	ncp_ts = __containerof(ncp, struct namecache_ts, nc_nc);
513 	*tsp = ncp_ts->nc_time;
514 	*ticksp = ncp_ts->nc_ticks;
515 }
516 
517 #ifdef DEBUG_CACHE
518 static int __read_mostly	doingcache = 1;	/* 1 => enable the cache */
519 SYSCTL_INT(_debug, OID_AUTO, vfscache, CTLFLAG_RW, &doingcache, 0,
520     "VFS namecache enabled");
521 #endif
522 
523 /* Export size information to userland */
524 SYSCTL_INT(_debug_sizeof, OID_AUTO, namecache, CTLFLAG_RD, SYSCTL_NULL_INT_PTR,
525     sizeof(struct namecache), "sizeof(struct namecache)");
526 
527 /*
528  * The new name cache statistics
529  */
530 static SYSCTL_NODE(_vfs_cache, OID_AUTO, stats, CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
531     "Name cache statistics");
532 
533 #define STATNODE_ULONG(name, varname, descr)					\
534 	SYSCTL_ULONG(_vfs_cache_stats, OID_AUTO, name, CTLFLAG_RD, &varname, 0, descr);
535 #define STATNODE_COUNTER(name, varname, descr)					\
536 	static COUNTER_U64_DEFINE_EARLY(varname);				\
537 	SYSCTL_COUNTER_U64(_vfs_cache_stats, OID_AUTO, name, CTLFLAG_RD, &varname, \
538 	    descr);
539 STATNODE_ULONG(neg, numneg, "Number of negative cache entries");
540 STATNODE_ULONG(count, numcache, "Number of cache entries");
541 STATNODE_COUNTER(heldvnodes, numcachehv, "Number of namecache entries with vnodes held");
542 STATNODE_COUNTER(drops, numdrops, "Number of dropped entries due to reaching the limit");
543 STATNODE_COUNTER(dothits, dothits, "Number of '.' hits");
544 STATNODE_COUNTER(dotdothis, dotdothits, "Number of '..' hits");
545 STATNODE_COUNTER(miss, nummiss, "Number of cache misses");
546 STATNODE_COUNTER(misszap, nummisszap, "Number of cache misses we do not want to cache");
547 STATNODE_COUNTER(posszaps, numposzaps,
548     "Number of cache hits (positive) we do not want to cache");
549 STATNODE_COUNTER(poshits, numposhits, "Number of cache hits (positive)");
550 STATNODE_COUNTER(negzaps, numnegzaps,
551     "Number of cache hits (negative) we do not want to cache");
552 STATNODE_COUNTER(neghits, numneghits, "Number of cache hits (negative)");
553 /* These count for vn_getcwd(), too. */
554 STATNODE_COUNTER(fullpathcalls, numfullpathcalls, "Number of fullpath search calls");
555 STATNODE_COUNTER(fullpathfail1, numfullpathfail1, "Number of fullpath search errors (ENOTDIR)");
556 STATNODE_COUNTER(fullpathfail2, numfullpathfail2,
557     "Number of fullpath search errors (VOP_VPTOCNP failures)");
558 STATNODE_COUNTER(fullpathfail4, numfullpathfail4, "Number of fullpath search errors (ENOMEM)");
559 STATNODE_COUNTER(fullpathfound, numfullpathfound, "Number of successful fullpath calls");
560 STATNODE_COUNTER(symlinktoobig, symlinktoobig, "Number of times symlink did not fit the cache");
561 
562 /*
563  * Debug or developer statistics.
564  */
565 static SYSCTL_NODE(_vfs_cache, OID_AUTO, debug, CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
566     "Name cache debugging");
567 #define DEBUGNODE_ULONG(name, varname, descr)					\
568 	SYSCTL_ULONG(_vfs_cache_debug, OID_AUTO, name, CTLFLAG_RD, &varname, 0, descr);
569 #define DEBUGNODE_COUNTER(name, varname, descr)					\
570 	static COUNTER_U64_DEFINE_EARLY(varname);				\
571 	SYSCTL_COUNTER_U64(_vfs_cache_debug, OID_AUTO, name, CTLFLAG_RD, &varname, \
572 	    descr);
573 DEBUGNODE_COUNTER(zap_bucket_relock_success, zap_bucket_relock_success,
574     "Number of successful removals after relocking");
575 static long zap_bucket_fail;
576 DEBUGNODE_ULONG(zap_bucket_fail, zap_bucket_fail, "");
577 static long zap_bucket_fail2;
578 DEBUGNODE_ULONG(zap_bucket_fail2, zap_bucket_fail2, "");
579 static long cache_lock_vnodes_cel_3_failures;
580 DEBUGNODE_ULONG(vnodes_cel_3_failures, cache_lock_vnodes_cel_3_failures,
581     "Number of times 3-way vnode locking failed");
582 
583 static void cache_fplookup_lockout(void);
584 static void cache_fplookup_restore(void);
585 
586 static void cache_zap_locked(struct namecache *ncp);
587 static int vn_fullpath_hardlink(struct nameidata *ndp, char **retbuf,
588     char **freebuf, size_t *buflen);
589 static int vn_fullpath_any_smr(struct vnode *vp, struct vnode *rdir, char *buf,
590     char **retbuf, size_t *buflen, size_t addend);
591 static int vn_fullpath_any(struct vnode *vp, struct vnode *rdir, char *buf,
592     char **retbuf, size_t *buflen);
593 static int vn_fullpath_dir(struct vnode *vp, struct vnode *rdir, char *buf,
594     char **retbuf, size_t *len, size_t addend);
595 
596 static MALLOC_DEFINE(M_VFSCACHE, "vfscache", "VFS name cache entries");
597 
598 static inline void
599 cache_assert_vlp_locked(struct mtx *vlp)
600 {
601 
602 	if (vlp != NULL)
603 		mtx_assert(vlp, MA_OWNED);
604 }
605 
606 static inline void
607 cache_assert_vnode_locked(struct vnode *vp)
608 {
609 	struct mtx *vlp;
610 
611 	vlp = VP2VNODELOCK(vp);
612 	cache_assert_vlp_locked(vlp);
613 }
614 
615 /*
616  * Directory vnodes with entries are held for two reasons:
617  * 1. make them less of a target for reclamation in vnlru
618  * 2. suffer smaller performance penalty in locked lookup as requeieing is avoided
619  *
620  * It will be feasible to stop doing it altogether if all filesystems start
621  * supporting lockless lookup.
622  */
623 static void
624 cache_hold_vnode(struct vnode *vp)
625 {
626 
627 	cache_assert_vnode_locked(vp);
628 	VNPASS(LIST_EMPTY(&vp->v_cache_src), vp);
629 	vhold(vp);
630 	counter_u64_add(numcachehv, 1);
631 }
632 
633 static void
634 cache_drop_vnode(struct vnode *vp)
635 {
636 
637 	/*
638 	 * Called after all locks are dropped, meaning we can't assert
639 	 * on the state of v_cache_src.
640 	 */
641 	vdrop(vp);
642 	counter_u64_add(numcachehv, -1);
643 }
644 
645 /*
646  * UMA zones.
647  */
648 static uma_zone_t __read_mostly cache_zone_small;
649 static uma_zone_t __read_mostly cache_zone_small_ts;
650 static uma_zone_t __read_mostly cache_zone_large;
651 static uma_zone_t __read_mostly cache_zone_large_ts;
652 
653 char *
654 cache_symlink_alloc(size_t size, int flags)
655 {
656 
657 	if (size < CACHE_ZONE_SMALL_SIZE) {
658 		return (uma_zalloc_smr(cache_zone_small, flags));
659 	}
660 	if (size < CACHE_ZONE_LARGE_SIZE) {
661 		return (uma_zalloc_smr(cache_zone_large, flags));
662 	}
663 	counter_u64_add(symlinktoobig, 1);
664 	SDT_PROBE1(vfs, namecache, symlink, alloc__fail, size);
665 	return (NULL);
666 }
667 
668 void
669 cache_symlink_free(char *string, size_t size)
670 {
671 
672 	MPASS(string != NULL);
673 	KASSERT(size < CACHE_ZONE_LARGE_SIZE,
674 	    ("%s: size %zu too big", __func__, size));
675 
676 	if (size < CACHE_ZONE_SMALL_SIZE) {
677 		uma_zfree_smr(cache_zone_small, string);
678 		return;
679 	}
680 	if (size < CACHE_ZONE_LARGE_SIZE) {
681 		uma_zfree_smr(cache_zone_large, string);
682 		return;
683 	}
684 	__assert_unreachable();
685 }
686 
687 static struct namecache *
688 cache_alloc_uma(int len, bool ts)
689 {
690 	struct namecache_ts *ncp_ts;
691 	struct namecache *ncp;
692 
693 	if (__predict_false(ts)) {
694 		if (len <= CACHE_PATH_CUTOFF)
695 			ncp_ts = uma_zalloc_smr(cache_zone_small_ts, M_WAITOK);
696 		else
697 			ncp_ts = uma_zalloc_smr(cache_zone_large_ts, M_WAITOK);
698 		ncp = &ncp_ts->nc_nc;
699 	} else {
700 		if (len <= CACHE_PATH_CUTOFF)
701 			ncp = uma_zalloc_smr(cache_zone_small, M_WAITOK);
702 		else
703 			ncp = uma_zalloc_smr(cache_zone_large, M_WAITOK);
704 	}
705 	return (ncp);
706 }
707 
708 static void
709 cache_free_uma(struct namecache *ncp)
710 {
711 	struct namecache_ts *ncp_ts;
712 
713 	if (__predict_false(ncp->nc_flag & NCF_TS)) {
714 		ncp_ts = __containerof(ncp, struct namecache_ts, nc_nc);
715 		if (ncp->nc_nlen <= CACHE_PATH_CUTOFF)
716 			uma_zfree_smr(cache_zone_small_ts, ncp_ts);
717 		else
718 			uma_zfree_smr(cache_zone_large_ts, ncp_ts);
719 	} else {
720 		if (ncp->nc_nlen <= CACHE_PATH_CUTOFF)
721 			uma_zfree_smr(cache_zone_small, ncp);
722 		else
723 			uma_zfree_smr(cache_zone_large, ncp);
724 	}
725 }
726 
727 static struct namecache *
728 cache_alloc(int len, bool ts)
729 {
730 	u_long lnumcache;
731 
732 	/*
733 	 * Avoid blowout in namecache entries.
734 	 *
735 	 * Bugs:
736 	 * 1. filesystems may end up trying to add an already existing entry
737 	 * (for example this can happen after a cache miss during concurrent
738 	 * lookup), in which case we will call cache_neg_evict despite not
739 	 * adding anything.
740 	 * 2. the routine may fail to free anything and no provisions are made
741 	 * to make it try harder (see the inside for failure modes)
742 	 * 3. it only ever looks at negative entries.
743 	 */
744 	lnumcache = atomic_fetchadd_long(&numcache, 1) + 1;
745 	if (cache_neg_evict_cond(lnumcache)) {
746 		lnumcache = atomic_load_long(&numcache);
747 	}
748 	if (__predict_false(lnumcache >= ncsize)) {
749 		atomic_subtract_long(&numcache, 1);
750 		counter_u64_add(numdrops, 1);
751 		return (NULL);
752 	}
753 	return (cache_alloc_uma(len, ts));
754 }
755 
756 static void
757 cache_free(struct namecache *ncp)
758 {
759 
760 	MPASS(ncp != NULL);
761 	if ((ncp->nc_flag & NCF_DVDROP) != 0) {
762 		cache_drop_vnode(ncp->nc_dvp);
763 	}
764 	cache_free_uma(ncp);
765 	atomic_subtract_long(&numcache, 1);
766 }
767 
768 static void
769 cache_free_batch(struct cache_freebatch *batch)
770 {
771 	struct namecache *ncp, *nnp;
772 	int i;
773 
774 	i = 0;
775 	if (TAILQ_EMPTY(batch))
776 		goto out;
777 	TAILQ_FOREACH_SAFE(ncp, batch, nc_dst, nnp) {
778 		if ((ncp->nc_flag & NCF_DVDROP) != 0) {
779 			cache_drop_vnode(ncp->nc_dvp);
780 		}
781 		cache_free_uma(ncp);
782 		i++;
783 	}
784 	atomic_subtract_long(&numcache, i);
785 out:
786 	SDT_PROBE1(vfs, namecache, purge, batch, i);
787 }
788 
789 /*
790  * Hashing.
791  *
792  * The code was made to use FNV in 2001 and this choice needs to be revisited.
793  *
794  * Short summary of the difficulty:
795  * The longest name which can be inserted is NAME_MAX characters in length (or
796  * 255 at the time of writing this comment), while majority of names used in
797  * practice are significantly shorter (mostly below 10). More importantly
798  * majority of lookups performed find names are even shorter than that.
799  *
800  * This poses a problem where hashes which do better than FNV past word size
801  * (or so) tend to come with additional overhead when finalizing the result,
802  * making them noticeably slower for the most commonly used range.
803  *
804  * Consider a path like: /usr/obj/usr/src/sys/amd64/GENERIC/vnode_if.c
805  *
806  * When looking it up the most time consuming part by a large margin (at least
807  * on amd64) is hashing.  Replacing FNV with something which pessimizes short
808  * input would make the slowest part stand out even more.
809  */
810 
811 /*
812  * TODO: With the value stored we can do better than computing the hash based
813  * on the address.
814  */
815 static void
816 cache_prehash(struct vnode *vp)
817 {
818 
819 	vp->v_nchash = fnv_32_buf(&vp, sizeof(vp), FNV1_32_INIT);
820 }
821 
822 static uint32_t
823 cache_get_hash(char *name, u_char len, struct vnode *dvp)
824 {
825 
826 	return (fnv_32_buf(name, len, dvp->v_nchash));
827 }
828 
829 static uint32_t
830 cache_get_hash_iter_start(struct vnode *dvp)
831 {
832 
833 	return (dvp->v_nchash);
834 }
835 
836 static uint32_t
837 cache_get_hash_iter(char c, uint32_t hash)
838 {
839 
840 	return (fnv_32_buf(&c, 1, hash));
841 }
842 
843 static uint32_t
844 cache_get_hash_iter_finish(uint32_t hash)
845 {
846 
847 	return (hash);
848 }
849 
850 static inline struct nchashhead *
851 NCP2BUCKET(struct namecache *ncp)
852 {
853 	uint32_t hash;
854 
855 	hash = cache_get_hash(ncp->nc_name, ncp->nc_nlen, ncp->nc_dvp);
856 	return (NCHHASH(hash));
857 }
858 
859 static inline struct mtx *
860 NCP2BUCKETLOCK(struct namecache *ncp)
861 {
862 	uint32_t hash;
863 
864 	hash = cache_get_hash(ncp->nc_name, ncp->nc_nlen, ncp->nc_dvp);
865 	return (HASH2BUCKETLOCK(hash));
866 }
867 
868 #ifdef INVARIANTS
869 static void
870 cache_assert_bucket_locked(struct namecache *ncp)
871 {
872 	struct mtx *blp;
873 
874 	blp = NCP2BUCKETLOCK(ncp);
875 	mtx_assert(blp, MA_OWNED);
876 }
877 
878 static void
879 cache_assert_bucket_unlocked(struct namecache *ncp)
880 {
881 	struct mtx *blp;
882 
883 	blp = NCP2BUCKETLOCK(ncp);
884 	mtx_assert(blp, MA_NOTOWNED);
885 }
886 #else
887 #define cache_assert_bucket_locked(x) do { } while (0)
888 #define cache_assert_bucket_unlocked(x) do { } while (0)
889 #endif
890 
891 #define cache_sort_vnodes(x, y)	_cache_sort_vnodes((void **)(x), (void **)(y))
892 static void
893 _cache_sort_vnodes(void **p1, void **p2)
894 {
895 	void *tmp;
896 
897 	MPASS(*p1 != NULL || *p2 != NULL);
898 
899 	if (*p1 > *p2) {
900 		tmp = *p2;
901 		*p2 = *p1;
902 		*p1 = tmp;
903 	}
904 }
905 
906 static void
907 cache_lock_all_buckets(void)
908 {
909 	u_int i;
910 
911 	for (i = 0; i < numbucketlocks; i++)
912 		mtx_lock(&bucketlocks[i]);
913 }
914 
915 static void
916 cache_unlock_all_buckets(void)
917 {
918 	u_int i;
919 
920 	for (i = 0; i < numbucketlocks; i++)
921 		mtx_unlock(&bucketlocks[i]);
922 }
923 
924 static void
925 cache_lock_all_vnodes(void)
926 {
927 	u_int i;
928 
929 	for (i = 0; i < numvnodelocks; i++)
930 		mtx_lock(&vnodelocks[i]);
931 }
932 
933 static void
934 cache_unlock_all_vnodes(void)
935 {
936 	u_int i;
937 
938 	for (i = 0; i < numvnodelocks; i++)
939 		mtx_unlock(&vnodelocks[i]);
940 }
941 
942 static int
943 cache_trylock_vnodes(struct mtx *vlp1, struct mtx *vlp2)
944 {
945 
946 	cache_sort_vnodes(&vlp1, &vlp2);
947 
948 	if (vlp1 != NULL) {
949 		if (!mtx_trylock(vlp1))
950 			return (EAGAIN);
951 	}
952 	if (!mtx_trylock(vlp2)) {
953 		if (vlp1 != NULL)
954 			mtx_unlock(vlp1);
955 		return (EAGAIN);
956 	}
957 
958 	return (0);
959 }
960 
961 static void
962 cache_lock_vnodes(struct mtx *vlp1, struct mtx *vlp2)
963 {
964 
965 	MPASS(vlp1 != NULL || vlp2 != NULL);
966 	MPASS(vlp1 <= vlp2);
967 
968 	if (vlp1 != NULL)
969 		mtx_lock(vlp1);
970 	if (vlp2 != NULL)
971 		mtx_lock(vlp2);
972 }
973 
974 static void
975 cache_unlock_vnodes(struct mtx *vlp1, struct mtx *vlp2)
976 {
977 
978 	MPASS(vlp1 != NULL || vlp2 != NULL);
979 
980 	if (vlp1 != NULL)
981 		mtx_unlock(vlp1);
982 	if (vlp2 != NULL)
983 		mtx_unlock(vlp2);
984 }
985 
986 static int
987 sysctl_nchstats(SYSCTL_HANDLER_ARGS)
988 {
989 	struct nchstats snap;
990 
991 	if (req->oldptr == NULL)
992 		return (SYSCTL_OUT(req, 0, sizeof(snap)));
993 
994 	snap = nchstats;
995 	snap.ncs_goodhits = counter_u64_fetch(numposhits);
996 	snap.ncs_neghits = counter_u64_fetch(numneghits);
997 	snap.ncs_badhits = counter_u64_fetch(numposzaps) +
998 	    counter_u64_fetch(numnegzaps);
999 	snap.ncs_miss = counter_u64_fetch(nummisszap) +
1000 	    counter_u64_fetch(nummiss);
1001 
1002 	return (SYSCTL_OUT(req, &snap, sizeof(snap)));
1003 }
1004 SYSCTL_PROC(_vfs_cache, OID_AUTO, nchstats, CTLTYPE_OPAQUE | CTLFLAG_RD |
1005     CTLFLAG_MPSAFE, 0, 0, sysctl_nchstats, "LU",
1006     "VFS cache effectiveness statistics");
1007 
1008 static void
1009 cache_recalc_neg_min(u_int val)
1010 {
1011 
1012 	neg_min = (ncsize * val) / 100;
1013 }
1014 
1015 static int
1016 sysctl_negminpct(SYSCTL_HANDLER_ARGS)
1017 {
1018 	u_int val;
1019 	int error;
1020 
1021 	val = ncnegminpct;
1022 	error = sysctl_handle_int(oidp, &val, 0, req);
1023 	if (error != 0 || req->newptr == NULL)
1024 		return (error);
1025 
1026 	if (val == ncnegminpct)
1027 		return (0);
1028 	if (val < 0 || val > 99)
1029 		return (EINVAL);
1030 	ncnegminpct = val;
1031 	cache_recalc_neg_min(val);
1032 	return (0);
1033 }
1034 
1035 SYSCTL_PROC(_vfs_cache_param, OID_AUTO, negminpct,
1036     CTLTYPE_INT | CTLFLAG_MPSAFE | CTLFLAG_RW, NULL, 0, sysctl_negminpct,
1037     "I", "Negative entry \% of namecache capacity above which automatic eviction is allowed");
1038 
1039 #ifdef DIAGNOSTIC
1040 /*
1041  * Grab an atomic snapshot of the name cache hash chain lengths
1042  */
1043 static SYSCTL_NODE(_debug, OID_AUTO, hashstat,
1044     CTLFLAG_RW | CTLFLAG_MPSAFE, NULL,
1045     "hash table stats");
1046 
1047 static int
1048 sysctl_debug_hashstat_rawnchash(SYSCTL_HANDLER_ARGS)
1049 {
1050 	struct nchashhead *ncpp;
1051 	struct namecache *ncp;
1052 	int i, error, n_nchash, *cntbuf;
1053 
1054 retry:
1055 	n_nchash = nchash + 1;	/* nchash is max index, not count */
1056 	if (req->oldptr == NULL)
1057 		return SYSCTL_OUT(req, 0, n_nchash * sizeof(int));
1058 	cntbuf = malloc(n_nchash * sizeof(int), M_TEMP, M_ZERO | M_WAITOK);
1059 	cache_lock_all_buckets();
1060 	if (n_nchash != nchash + 1) {
1061 		cache_unlock_all_buckets();
1062 		free(cntbuf, M_TEMP);
1063 		goto retry;
1064 	}
1065 	/* Scan hash tables counting entries */
1066 	for (ncpp = nchashtbl, i = 0; i < n_nchash; ncpp++, i++)
1067 		CK_SLIST_FOREACH(ncp, ncpp, nc_hash)
1068 			cntbuf[i]++;
1069 	cache_unlock_all_buckets();
1070 	for (error = 0, i = 0; i < n_nchash; i++)
1071 		if ((error = SYSCTL_OUT(req, &cntbuf[i], sizeof(int))) != 0)
1072 			break;
1073 	free(cntbuf, M_TEMP);
1074 	return (error);
1075 }
1076 SYSCTL_PROC(_debug_hashstat, OID_AUTO, rawnchash, CTLTYPE_INT|CTLFLAG_RD|
1077     CTLFLAG_MPSAFE, 0, 0, sysctl_debug_hashstat_rawnchash, "S,int",
1078     "nchash chain lengths");
1079 
1080 static int
1081 sysctl_debug_hashstat_nchash(SYSCTL_HANDLER_ARGS)
1082 {
1083 	int error;
1084 	struct nchashhead *ncpp;
1085 	struct namecache *ncp;
1086 	int n_nchash;
1087 	int count, maxlength, used, pct;
1088 
1089 	if (!req->oldptr)
1090 		return SYSCTL_OUT(req, 0, 4 * sizeof(int));
1091 
1092 	cache_lock_all_buckets();
1093 	n_nchash = nchash + 1;	/* nchash is max index, not count */
1094 	used = 0;
1095 	maxlength = 0;
1096 
1097 	/* Scan hash tables for applicable entries */
1098 	for (ncpp = nchashtbl; n_nchash > 0; n_nchash--, ncpp++) {
1099 		count = 0;
1100 		CK_SLIST_FOREACH(ncp, ncpp, nc_hash) {
1101 			count++;
1102 		}
1103 		if (count)
1104 			used++;
1105 		if (maxlength < count)
1106 			maxlength = count;
1107 	}
1108 	n_nchash = nchash + 1;
1109 	cache_unlock_all_buckets();
1110 	pct = (used * 100) / (n_nchash / 100);
1111 	error = SYSCTL_OUT(req, &n_nchash, sizeof(n_nchash));
1112 	if (error)
1113 		return (error);
1114 	error = SYSCTL_OUT(req, &used, sizeof(used));
1115 	if (error)
1116 		return (error);
1117 	error = SYSCTL_OUT(req, &maxlength, sizeof(maxlength));
1118 	if (error)
1119 		return (error);
1120 	error = SYSCTL_OUT(req, &pct, sizeof(pct));
1121 	if (error)
1122 		return (error);
1123 	return (0);
1124 }
1125 SYSCTL_PROC(_debug_hashstat, OID_AUTO, nchash, CTLTYPE_INT|CTLFLAG_RD|
1126     CTLFLAG_MPSAFE, 0, 0, sysctl_debug_hashstat_nchash, "I",
1127     "nchash statistics (number of total/used buckets, maximum chain length, usage percentage)");
1128 #endif
1129 
1130 /*
1131  * Negative entries management
1132  *
1133  * Various workloads create plenty of negative entries and barely use them
1134  * afterwards. Moreover malicious users can keep performing bogus lookups
1135  * adding even more entries. For example "make tinderbox" as of writing this
1136  * comment ends up with 2.6M namecache entries in total, 1.2M of which are
1137  * negative.
1138  *
1139  * As such, a rather aggressive eviction method is needed. The currently
1140  * employed method is a placeholder.
1141  *
1142  * Entries are split over numneglists separate lists, each of which is further
1143  * split into hot and cold entries. Entries get promoted after getting a hit.
1144  * Eviction happens on addition of new entry.
1145  */
1146 static SYSCTL_NODE(_vfs_cache, OID_AUTO, neg, CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
1147     "Name cache negative entry statistics");
1148 
1149 SYSCTL_ULONG(_vfs_cache_neg, OID_AUTO, count, CTLFLAG_RD, &numneg, 0,
1150     "Number of negative cache entries");
1151 
1152 static COUNTER_U64_DEFINE_EARLY(neg_created);
1153 SYSCTL_COUNTER_U64(_vfs_cache_neg, OID_AUTO, created, CTLFLAG_RD, &neg_created,
1154     "Number of created negative entries");
1155 
1156 static COUNTER_U64_DEFINE_EARLY(neg_evicted);
1157 SYSCTL_COUNTER_U64(_vfs_cache_neg, OID_AUTO, evicted, CTLFLAG_RD, &neg_evicted,
1158     "Number of evicted negative entries");
1159 
1160 static COUNTER_U64_DEFINE_EARLY(neg_evict_skipped_empty);
1161 SYSCTL_COUNTER_U64(_vfs_cache_neg, OID_AUTO, evict_skipped_empty, CTLFLAG_RD,
1162     &neg_evict_skipped_empty,
1163     "Number of times evicting failed due to lack of entries");
1164 
1165 static COUNTER_U64_DEFINE_EARLY(neg_evict_skipped_missed);
1166 SYSCTL_COUNTER_U64(_vfs_cache_neg, OID_AUTO, evict_skipped_missed, CTLFLAG_RD,
1167     &neg_evict_skipped_missed,
1168     "Number of times evicting failed due to target entry disappearing");
1169 
1170 static COUNTER_U64_DEFINE_EARLY(neg_evict_skipped_contended);
1171 SYSCTL_COUNTER_U64(_vfs_cache_neg, OID_AUTO, evict_skipped_contended, CTLFLAG_RD,
1172     &neg_evict_skipped_contended,
1173     "Number of times evicting failed due to contention");
1174 
1175 SYSCTL_COUNTER_U64(_vfs_cache_neg, OID_AUTO, hits, CTLFLAG_RD, &numneghits,
1176     "Number of cache hits (negative)");
1177 
1178 static int
1179 sysctl_neg_hot(SYSCTL_HANDLER_ARGS)
1180 {
1181 	int i, out;
1182 
1183 	out = 0;
1184 	for (i = 0; i < numneglists; i++)
1185 		out += neglists[i].nl_hotnum;
1186 
1187 	return (SYSCTL_OUT(req, &out, sizeof(out)));
1188 }
1189 SYSCTL_PROC(_vfs_cache_neg, OID_AUTO, hot, CTLTYPE_INT | CTLFLAG_RD |
1190     CTLFLAG_MPSAFE, 0, 0, sysctl_neg_hot, "I",
1191     "Number of hot negative entries");
1192 
1193 static void
1194 cache_neg_init(struct namecache *ncp)
1195 {
1196 	struct negstate *ns;
1197 
1198 	ncp->nc_flag |= NCF_NEGATIVE;
1199 	ns = NCP2NEGSTATE(ncp);
1200 	ns->neg_flag = 0;
1201 	ns->neg_hit = 0;
1202 	counter_u64_add(neg_created, 1);
1203 }
1204 
1205 #define CACHE_NEG_PROMOTION_THRESH 2
1206 
1207 static bool
1208 cache_neg_hit_prep(struct namecache *ncp)
1209 {
1210 	struct negstate *ns;
1211 	u_char n;
1212 
1213 	ns = NCP2NEGSTATE(ncp);
1214 	n = atomic_load_char(&ns->neg_hit);
1215 	for (;;) {
1216 		if (n >= CACHE_NEG_PROMOTION_THRESH)
1217 			return (false);
1218 		if (atomic_fcmpset_8(&ns->neg_hit, &n, n + 1))
1219 			break;
1220 	}
1221 	return (n + 1 == CACHE_NEG_PROMOTION_THRESH);
1222 }
1223 
1224 /*
1225  * Nothing to do here but it is provided for completeness as some
1226  * cache_neg_hit_prep callers may end up returning without even
1227  * trying to promote.
1228  */
1229 #define cache_neg_hit_abort(ncp)	do { } while (0)
1230 
1231 static void
1232 cache_neg_hit_finish(struct namecache *ncp)
1233 {
1234 
1235 	SDT_PROBE2(vfs, namecache, lookup, hit__negative, ncp->nc_dvp, ncp->nc_name);
1236 	counter_u64_add(numneghits, 1);
1237 }
1238 
1239 /*
1240  * Move a negative entry to the hot list.
1241  */
1242 static void
1243 cache_neg_promote_locked(struct namecache *ncp)
1244 {
1245 	struct neglist *nl;
1246 	struct negstate *ns;
1247 
1248 	ns = NCP2NEGSTATE(ncp);
1249 	nl = NCP2NEGLIST(ncp);
1250 	mtx_assert(&nl->nl_lock, MA_OWNED);
1251 	if ((ns->neg_flag & NEG_HOT) == 0) {
1252 		TAILQ_REMOVE(&nl->nl_list, ncp, nc_dst);
1253 		TAILQ_INSERT_TAIL(&nl->nl_hotlist, ncp, nc_dst);
1254 		nl->nl_hotnum++;
1255 		ns->neg_flag |= NEG_HOT;
1256 	}
1257 }
1258 
1259 /*
1260  * Move a hot negative entry to the cold list.
1261  */
1262 static void
1263 cache_neg_demote_locked(struct namecache *ncp)
1264 {
1265 	struct neglist *nl;
1266 	struct negstate *ns;
1267 
1268 	ns = NCP2NEGSTATE(ncp);
1269 	nl = NCP2NEGLIST(ncp);
1270 	mtx_assert(&nl->nl_lock, MA_OWNED);
1271 	MPASS(ns->neg_flag & NEG_HOT);
1272 	TAILQ_REMOVE(&nl->nl_hotlist, ncp, nc_dst);
1273 	TAILQ_INSERT_TAIL(&nl->nl_list, ncp, nc_dst);
1274 	nl->nl_hotnum--;
1275 	ns->neg_flag &= ~NEG_HOT;
1276 	atomic_store_char(&ns->neg_hit, 0);
1277 }
1278 
1279 /*
1280  * Move a negative entry to the hot list if it matches the lookup.
1281  *
1282  * We have to take locks, but they may be contended and in the worst
1283  * case we may need to go off CPU. We don't want to spin within the
1284  * smr section and we can't block with it. Exiting the section means
1285  * the found entry could have been evicted. We are going to look it
1286  * up again.
1287  */
1288 static bool
1289 cache_neg_promote_cond(struct vnode *dvp, struct componentname *cnp,
1290     struct namecache *oncp, uint32_t hash)
1291 {
1292 	struct namecache *ncp;
1293 	struct neglist *nl;
1294 	u_char nc_flag;
1295 
1296 	nl = NCP2NEGLIST(oncp);
1297 
1298 	mtx_lock(&nl->nl_lock);
1299 	/*
1300 	 * For hash iteration.
1301 	 */
1302 	vfs_smr_enter();
1303 
1304 	/*
1305 	 * Avoid all surprises by only succeeding if we got the same entry and
1306 	 * bailing completely otherwise.
1307 	 * XXX There are no provisions to keep the vnode around, meaning we may
1308 	 * end up promoting a negative entry for a *new* vnode and returning
1309 	 * ENOENT on its account. This is the error we want to return anyway
1310 	 * and promotion is harmless.
1311 	 *
1312 	 * In particular at this point there can be a new ncp which matches the
1313 	 * search but hashes to a different neglist.
1314 	 */
1315 	CK_SLIST_FOREACH(ncp, (NCHHASH(hash)), nc_hash) {
1316 		if (ncp == oncp)
1317 			break;
1318 	}
1319 
1320 	/*
1321 	 * No match to begin with.
1322 	 */
1323 	if (__predict_false(ncp == NULL)) {
1324 		goto out_abort;
1325 	}
1326 
1327 	/*
1328 	 * The newly found entry may be something different...
1329 	 */
1330 	if (!(ncp->nc_dvp == dvp && ncp->nc_nlen == cnp->cn_namelen &&
1331 	    !bcmp(ncp->nc_name, cnp->cn_nameptr, ncp->nc_nlen))) {
1332 		goto out_abort;
1333 	}
1334 
1335 	/*
1336 	 * ... and not even negative.
1337 	 */
1338 	nc_flag = atomic_load_char(&ncp->nc_flag);
1339 	if ((nc_flag & NCF_NEGATIVE) == 0) {
1340 		goto out_abort;
1341 	}
1342 
1343 	if (!cache_ncp_canuse(ncp)) {
1344 		goto out_abort;
1345 	}
1346 
1347 	cache_neg_promote_locked(ncp);
1348 	cache_neg_hit_finish(ncp);
1349 	vfs_smr_exit();
1350 	mtx_unlock(&nl->nl_lock);
1351 	return (true);
1352 out_abort:
1353 	vfs_smr_exit();
1354 	mtx_unlock(&nl->nl_lock);
1355 	return (false);
1356 }
1357 
1358 static void
1359 cache_neg_promote(struct namecache *ncp)
1360 {
1361 	struct neglist *nl;
1362 
1363 	nl = NCP2NEGLIST(ncp);
1364 	mtx_lock(&nl->nl_lock);
1365 	cache_neg_promote_locked(ncp);
1366 	mtx_unlock(&nl->nl_lock);
1367 }
1368 
1369 static void
1370 cache_neg_insert(struct namecache *ncp)
1371 {
1372 	struct neglist *nl;
1373 
1374 	MPASS(ncp->nc_flag & NCF_NEGATIVE);
1375 	cache_assert_bucket_locked(ncp);
1376 	nl = NCP2NEGLIST(ncp);
1377 	mtx_lock(&nl->nl_lock);
1378 	TAILQ_INSERT_TAIL(&nl->nl_list, ncp, nc_dst);
1379 	mtx_unlock(&nl->nl_lock);
1380 	atomic_add_long(&numneg, 1);
1381 }
1382 
1383 static void
1384 cache_neg_remove(struct namecache *ncp)
1385 {
1386 	struct neglist *nl;
1387 	struct negstate *ns;
1388 
1389 	cache_assert_bucket_locked(ncp);
1390 	nl = NCP2NEGLIST(ncp);
1391 	ns = NCP2NEGSTATE(ncp);
1392 	mtx_lock(&nl->nl_lock);
1393 	if ((ns->neg_flag & NEG_HOT) != 0) {
1394 		TAILQ_REMOVE(&nl->nl_hotlist, ncp, nc_dst);
1395 		nl->nl_hotnum--;
1396 	} else {
1397 		TAILQ_REMOVE(&nl->nl_list, ncp, nc_dst);
1398 	}
1399 	mtx_unlock(&nl->nl_lock);
1400 	atomic_subtract_long(&numneg, 1);
1401 }
1402 
1403 static struct neglist *
1404 cache_neg_evict_select_list(void)
1405 {
1406 	struct neglist *nl;
1407 	u_int c;
1408 
1409 	c = atomic_fetchadd_int(&neg_cycle, 1) + 1;
1410 	nl = &neglists[c % numneglists];
1411 	if (!mtx_trylock(&nl->nl_evict_lock)) {
1412 		counter_u64_add(neg_evict_skipped_contended, 1);
1413 		return (NULL);
1414 	}
1415 	return (nl);
1416 }
1417 
1418 static struct namecache *
1419 cache_neg_evict_select_entry(struct neglist *nl)
1420 {
1421 	struct namecache *ncp, *lncp;
1422 	struct negstate *ns, *lns;
1423 	int i;
1424 
1425 	mtx_assert(&nl->nl_evict_lock, MA_OWNED);
1426 	mtx_assert(&nl->nl_lock, MA_OWNED);
1427 	ncp = TAILQ_FIRST(&nl->nl_list);
1428 	if (ncp == NULL)
1429 		return (NULL);
1430 	lncp = ncp;
1431 	lns = NCP2NEGSTATE(lncp);
1432 	for (i = 1; i < 4; i++) {
1433 		ncp = TAILQ_NEXT(ncp, nc_dst);
1434 		if (ncp == NULL)
1435 			break;
1436 		ns = NCP2NEGSTATE(ncp);
1437 		if (ns->neg_hit < lns->neg_hit) {
1438 			lncp = ncp;
1439 			lns = ns;
1440 		}
1441 	}
1442 	return (lncp);
1443 }
1444 
1445 static bool
1446 cache_neg_evict(void)
1447 {
1448 	struct namecache *ncp, *ncp2;
1449 	struct neglist *nl;
1450 	struct vnode *dvp;
1451 	struct mtx *dvlp;
1452 	struct mtx *blp;
1453 	uint32_t hash;
1454 	u_char nlen;
1455 	bool evicted;
1456 
1457 	nl = cache_neg_evict_select_list();
1458 	if (nl == NULL) {
1459 		return (false);
1460 	}
1461 
1462 	mtx_lock(&nl->nl_lock);
1463 	ncp = TAILQ_FIRST(&nl->nl_hotlist);
1464 	if (ncp != NULL) {
1465 		cache_neg_demote_locked(ncp);
1466 	}
1467 	ncp = cache_neg_evict_select_entry(nl);
1468 	if (ncp == NULL) {
1469 		counter_u64_add(neg_evict_skipped_empty, 1);
1470 		mtx_unlock(&nl->nl_lock);
1471 		mtx_unlock(&nl->nl_evict_lock);
1472 		return (false);
1473 	}
1474 	nlen = ncp->nc_nlen;
1475 	dvp = ncp->nc_dvp;
1476 	hash = cache_get_hash(ncp->nc_name, nlen, dvp);
1477 	dvlp = VP2VNODELOCK(dvp);
1478 	blp = HASH2BUCKETLOCK(hash);
1479 	mtx_unlock(&nl->nl_lock);
1480 	mtx_unlock(&nl->nl_evict_lock);
1481 	mtx_lock(dvlp);
1482 	mtx_lock(blp);
1483 	/*
1484 	 * Note that since all locks were dropped above, the entry may be
1485 	 * gone or reallocated to be something else.
1486 	 */
1487 	CK_SLIST_FOREACH(ncp2, (NCHHASH(hash)), nc_hash) {
1488 		if (ncp2 == ncp && ncp2->nc_dvp == dvp &&
1489 		    ncp2->nc_nlen == nlen && (ncp2->nc_flag & NCF_NEGATIVE) != 0)
1490 			break;
1491 	}
1492 	if (ncp2 == NULL) {
1493 		counter_u64_add(neg_evict_skipped_missed, 1);
1494 		ncp = NULL;
1495 		evicted = false;
1496 	} else {
1497 		MPASS(dvlp == VP2VNODELOCK(ncp->nc_dvp));
1498 		MPASS(blp == NCP2BUCKETLOCK(ncp));
1499 		SDT_PROBE2(vfs, namecache, evict_negative, done, ncp->nc_dvp,
1500 		    ncp->nc_name);
1501 		cache_zap_locked(ncp);
1502 		counter_u64_add(neg_evicted, 1);
1503 		evicted = true;
1504 	}
1505 	mtx_unlock(blp);
1506 	mtx_unlock(dvlp);
1507 	if (ncp != NULL)
1508 		cache_free(ncp);
1509 	return (evicted);
1510 }
1511 
1512 /*
1513  * Maybe evict a negative entry to create more room.
1514  *
1515  * The ncnegfactor parameter limits what fraction of the total count
1516  * can comprise of negative entries. However, if the cache is just
1517  * warming up this leads to excessive evictions.  As such, ncnegminpct
1518  * (recomputed to neg_min) dictates whether the above should be
1519  * applied.
1520  *
1521  * Try evicting if the cache is close to full capacity regardless of
1522  * other considerations.
1523  */
1524 static bool
1525 cache_neg_evict_cond(u_long lnumcache)
1526 {
1527 	u_long lnumneg;
1528 
1529 	if (ncsize - 1000 < lnumcache)
1530 		goto out_evict;
1531 	lnumneg = atomic_load_long(&numneg);
1532 	if (lnumneg < neg_min)
1533 		return (false);
1534 	if (lnumneg * ncnegfactor < lnumcache)
1535 		return (false);
1536 out_evict:
1537 	return (cache_neg_evict());
1538 }
1539 
1540 /*
1541  * cache_zap_locked():
1542  *
1543  *   Removes a namecache entry from cache, whether it contains an actual
1544  *   pointer to a vnode or if it is just a negative cache entry.
1545  */
1546 static void
1547 cache_zap_locked(struct namecache *ncp)
1548 {
1549 	struct nchashhead *ncpp;
1550 	struct vnode *dvp, *vp;
1551 
1552 	dvp = ncp->nc_dvp;
1553 	vp = ncp->nc_vp;
1554 
1555 	if (!(ncp->nc_flag & NCF_NEGATIVE))
1556 		cache_assert_vnode_locked(vp);
1557 	cache_assert_vnode_locked(dvp);
1558 	cache_assert_bucket_locked(ncp);
1559 
1560 	cache_ncp_invalidate(ncp);
1561 
1562 	ncpp = NCP2BUCKET(ncp);
1563 	CK_SLIST_REMOVE(ncpp, ncp, namecache, nc_hash);
1564 	if (!(ncp->nc_flag & NCF_NEGATIVE)) {
1565 		SDT_PROBE3(vfs, namecache, zap, done, dvp, ncp->nc_name, vp);
1566 		TAILQ_REMOVE(&vp->v_cache_dst, ncp, nc_dst);
1567 		if (ncp == vp->v_cache_dd) {
1568 			atomic_store_ptr(&vp->v_cache_dd, NULL);
1569 		}
1570 	} else {
1571 		SDT_PROBE2(vfs, namecache, zap_negative, done, dvp, ncp->nc_name);
1572 		cache_neg_remove(ncp);
1573 	}
1574 	if (ncp->nc_flag & NCF_ISDOTDOT) {
1575 		if (ncp == dvp->v_cache_dd) {
1576 			atomic_store_ptr(&dvp->v_cache_dd, NULL);
1577 		}
1578 	} else {
1579 		LIST_REMOVE(ncp, nc_src);
1580 		if (LIST_EMPTY(&dvp->v_cache_src)) {
1581 			ncp->nc_flag |= NCF_DVDROP;
1582 		}
1583 	}
1584 }
1585 
1586 static void
1587 cache_zap_negative_locked_vnode_kl(struct namecache *ncp, struct vnode *vp)
1588 {
1589 	struct mtx *blp;
1590 
1591 	MPASS(ncp->nc_dvp == vp);
1592 	MPASS(ncp->nc_flag & NCF_NEGATIVE);
1593 	cache_assert_vnode_locked(vp);
1594 
1595 	blp = NCP2BUCKETLOCK(ncp);
1596 	mtx_lock(blp);
1597 	cache_zap_locked(ncp);
1598 	mtx_unlock(blp);
1599 }
1600 
1601 static bool
1602 cache_zap_locked_vnode_kl2(struct namecache *ncp, struct vnode *vp,
1603     struct mtx **vlpp)
1604 {
1605 	struct mtx *pvlp, *vlp1, *vlp2, *to_unlock;
1606 	struct mtx *blp;
1607 
1608 	MPASS(vp == ncp->nc_dvp || vp == ncp->nc_vp);
1609 	cache_assert_vnode_locked(vp);
1610 
1611 	if (ncp->nc_flag & NCF_NEGATIVE) {
1612 		if (*vlpp != NULL) {
1613 			mtx_unlock(*vlpp);
1614 			*vlpp = NULL;
1615 		}
1616 		cache_zap_negative_locked_vnode_kl(ncp, vp);
1617 		return (true);
1618 	}
1619 
1620 	pvlp = VP2VNODELOCK(vp);
1621 	blp = NCP2BUCKETLOCK(ncp);
1622 	vlp1 = VP2VNODELOCK(ncp->nc_dvp);
1623 	vlp2 = VP2VNODELOCK(ncp->nc_vp);
1624 
1625 	if (*vlpp == vlp1 || *vlpp == vlp2) {
1626 		to_unlock = *vlpp;
1627 		*vlpp = NULL;
1628 	} else {
1629 		if (*vlpp != NULL) {
1630 			mtx_unlock(*vlpp);
1631 			*vlpp = NULL;
1632 		}
1633 		cache_sort_vnodes(&vlp1, &vlp2);
1634 		if (vlp1 == pvlp) {
1635 			mtx_lock(vlp2);
1636 			to_unlock = vlp2;
1637 		} else {
1638 			if (!mtx_trylock(vlp1))
1639 				goto out_relock;
1640 			to_unlock = vlp1;
1641 		}
1642 	}
1643 	mtx_lock(blp);
1644 	cache_zap_locked(ncp);
1645 	mtx_unlock(blp);
1646 	if (to_unlock != NULL)
1647 		mtx_unlock(to_unlock);
1648 	return (true);
1649 
1650 out_relock:
1651 	mtx_unlock(vlp2);
1652 	mtx_lock(vlp1);
1653 	mtx_lock(vlp2);
1654 	MPASS(*vlpp == NULL);
1655 	*vlpp = vlp1;
1656 	return (false);
1657 }
1658 
1659 /*
1660  * If trylocking failed we can get here. We know enough to take all needed locks
1661  * in the right order and re-lookup the entry.
1662  */
1663 static int
1664 cache_zap_unlocked_bucket(struct namecache *ncp, struct componentname *cnp,
1665     struct vnode *dvp, struct mtx *dvlp, struct mtx *vlp, uint32_t hash,
1666     struct mtx *blp)
1667 {
1668 	struct namecache *rncp;
1669 
1670 	cache_assert_bucket_unlocked(ncp);
1671 
1672 	cache_sort_vnodes(&dvlp, &vlp);
1673 	cache_lock_vnodes(dvlp, vlp);
1674 	mtx_lock(blp);
1675 	CK_SLIST_FOREACH(rncp, (NCHHASH(hash)), nc_hash) {
1676 		if (rncp == ncp && rncp->nc_dvp == dvp &&
1677 		    rncp->nc_nlen == cnp->cn_namelen &&
1678 		    !bcmp(rncp->nc_name, cnp->cn_nameptr, rncp->nc_nlen))
1679 			break;
1680 	}
1681 	if (rncp != NULL) {
1682 		cache_zap_locked(rncp);
1683 		mtx_unlock(blp);
1684 		cache_unlock_vnodes(dvlp, vlp);
1685 		counter_u64_add(zap_bucket_relock_success, 1);
1686 		return (0);
1687 	}
1688 
1689 	mtx_unlock(blp);
1690 	cache_unlock_vnodes(dvlp, vlp);
1691 	return (EAGAIN);
1692 }
1693 
1694 static int __noinline
1695 cache_zap_locked_bucket(struct namecache *ncp, struct componentname *cnp,
1696     uint32_t hash, struct mtx *blp)
1697 {
1698 	struct mtx *dvlp, *vlp;
1699 	struct vnode *dvp;
1700 
1701 	cache_assert_bucket_locked(ncp);
1702 
1703 	dvlp = VP2VNODELOCK(ncp->nc_dvp);
1704 	vlp = NULL;
1705 	if (!(ncp->nc_flag & NCF_NEGATIVE))
1706 		vlp = VP2VNODELOCK(ncp->nc_vp);
1707 	if (cache_trylock_vnodes(dvlp, vlp) == 0) {
1708 		cache_zap_locked(ncp);
1709 		mtx_unlock(blp);
1710 		cache_unlock_vnodes(dvlp, vlp);
1711 		return (0);
1712 	}
1713 
1714 	dvp = ncp->nc_dvp;
1715 	mtx_unlock(blp);
1716 	return (cache_zap_unlocked_bucket(ncp, cnp, dvp, dvlp, vlp, hash, blp));
1717 }
1718 
1719 static __noinline int
1720 cache_remove_cnp(struct vnode *dvp, struct componentname *cnp)
1721 {
1722 	struct namecache *ncp;
1723 	struct mtx *blp;
1724 	struct mtx *dvlp, *dvlp2;
1725 	uint32_t hash;
1726 	int error;
1727 
1728 	if (cnp->cn_namelen == 2 &&
1729 	    cnp->cn_nameptr[0] == '.' && cnp->cn_nameptr[1] == '.') {
1730 		dvlp = VP2VNODELOCK(dvp);
1731 		dvlp2 = NULL;
1732 		mtx_lock(dvlp);
1733 retry_dotdot:
1734 		ncp = dvp->v_cache_dd;
1735 		if (ncp == NULL) {
1736 			mtx_unlock(dvlp);
1737 			if (dvlp2 != NULL)
1738 				mtx_unlock(dvlp2);
1739 			SDT_PROBE2(vfs, namecache, removecnp, miss, dvp, cnp);
1740 			return (0);
1741 		}
1742 		if ((ncp->nc_flag & NCF_ISDOTDOT) != 0) {
1743 			if (!cache_zap_locked_vnode_kl2(ncp, dvp, &dvlp2))
1744 				goto retry_dotdot;
1745 			MPASS(dvp->v_cache_dd == NULL);
1746 			mtx_unlock(dvlp);
1747 			if (dvlp2 != NULL)
1748 				mtx_unlock(dvlp2);
1749 			cache_free(ncp);
1750 		} else {
1751 			atomic_store_ptr(&dvp->v_cache_dd, NULL);
1752 			mtx_unlock(dvlp);
1753 			if (dvlp2 != NULL)
1754 				mtx_unlock(dvlp2);
1755 		}
1756 		SDT_PROBE2(vfs, namecache, removecnp, hit, dvp, cnp);
1757 		return (1);
1758 	}
1759 
1760 	hash = cache_get_hash(cnp->cn_nameptr, cnp->cn_namelen, dvp);
1761 	blp = HASH2BUCKETLOCK(hash);
1762 retry:
1763 	if (CK_SLIST_EMPTY(NCHHASH(hash)))
1764 		goto out_no_entry;
1765 
1766 	mtx_lock(blp);
1767 
1768 	CK_SLIST_FOREACH(ncp, (NCHHASH(hash)), nc_hash) {
1769 		if (ncp->nc_dvp == dvp && ncp->nc_nlen == cnp->cn_namelen &&
1770 		    !bcmp(ncp->nc_name, cnp->cn_nameptr, ncp->nc_nlen))
1771 			break;
1772 	}
1773 
1774 	if (ncp == NULL) {
1775 		mtx_unlock(blp);
1776 		goto out_no_entry;
1777 	}
1778 
1779 	error = cache_zap_locked_bucket(ncp, cnp, hash, blp);
1780 	if (__predict_false(error != 0)) {
1781 		zap_bucket_fail++;
1782 		goto retry;
1783 	}
1784 	counter_u64_add(numposzaps, 1);
1785 	SDT_PROBE2(vfs, namecache, removecnp, hit, dvp, cnp);
1786 	cache_free(ncp);
1787 	return (1);
1788 out_no_entry:
1789 	counter_u64_add(nummisszap, 1);
1790 	SDT_PROBE2(vfs, namecache, removecnp, miss, dvp, cnp);
1791 	return (0);
1792 }
1793 
1794 static int __noinline
1795 cache_lookup_dot(struct vnode *dvp, struct vnode **vpp, struct componentname *cnp,
1796     struct timespec *tsp, int *ticksp)
1797 {
1798 	int ltype;
1799 
1800 	*vpp = dvp;
1801 	counter_u64_add(dothits, 1);
1802 	SDT_PROBE3(vfs, namecache, lookup, hit, dvp, ".", *vpp);
1803 	if (tsp != NULL)
1804 		timespecclear(tsp);
1805 	if (ticksp != NULL)
1806 		*ticksp = ticks;
1807 	vrefact(*vpp);
1808 	/*
1809 	 * When we lookup "." we still can be asked to lock it
1810 	 * differently...
1811 	 */
1812 	ltype = cnp->cn_lkflags & LK_TYPE_MASK;
1813 	if (ltype != VOP_ISLOCKED(*vpp)) {
1814 		if (ltype == LK_EXCLUSIVE) {
1815 			vn_lock(*vpp, LK_UPGRADE | LK_RETRY);
1816 			if (VN_IS_DOOMED((*vpp))) {
1817 				/* forced unmount */
1818 				vrele(*vpp);
1819 				*vpp = NULL;
1820 				return (ENOENT);
1821 			}
1822 		} else
1823 			vn_lock(*vpp, LK_DOWNGRADE | LK_RETRY);
1824 	}
1825 	return (-1);
1826 }
1827 
1828 static int __noinline
1829 cache_lookup_dotdot(struct vnode *dvp, struct vnode **vpp, struct componentname *cnp,
1830     struct timespec *tsp, int *ticksp)
1831 {
1832 	struct namecache_ts *ncp_ts;
1833 	struct namecache *ncp;
1834 	struct mtx *dvlp;
1835 	enum vgetstate vs;
1836 	int error, ltype;
1837 	bool whiteout;
1838 
1839 	MPASS((cnp->cn_flags & ISDOTDOT) != 0);
1840 
1841 	if ((cnp->cn_flags & MAKEENTRY) == 0) {
1842 		cache_remove_cnp(dvp, cnp);
1843 		return (0);
1844 	}
1845 
1846 	counter_u64_add(dotdothits, 1);
1847 retry:
1848 	dvlp = VP2VNODELOCK(dvp);
1849 	mtx_lock(dvlp);
1850 	ncp = dvp->v_cache_dd;
1851 	if (ncp == NULL) {
1852 		SDT_PROBE2(vfs, namecache, lookup, miss, dvp, "..");
1853 		mtx_unlock(dvlp);
1854 		return (0);
1855 	}
1856 	if ((ncp->nc_flag & NCF_ISDOTDOT) != 0) {
1857 		if (ncp->nc_flag & NCF_NEGATIVE)
1858 			*vpp = NULL;
1859 		else
1860 			*vpp = ncp->nc_vp;
1861 	} else
1862 		*vpp = ncp->nc_dvp;
1863 	if (*vpp == NULL)
1864 		goto negative_success;
1865 	SDT_PROBE3(vfs, namecache, lookup, hit, dvp, "..", *vpp);
1866 	cache_out_ts(ncp, tsp, ticksp);
1867 	if ((ncp->nc_flag & (NCF_ISDOTDOT | NCF_DTS)) ==
1868 	    NCF_DTS && tsp != NULL) {
1869 		ncp_ts = __containerof(ncp, struct namecache_ts, nc_nc);
1870 		*tsp = ncp_ts->nc_dotdottime;
1871 	}
1872 
1873 	MPASS(dvp != *vpp);
1874 	ltype = VOP_ISLOCKED(dvp);
1875 	VOP_UNLOCK(dvp);
1876 	vs = vget_prep(*vpp);
1877 	mtx_unlock(dvlp);
1878 	error = vget_finish(*vpp, cnp->cn_lkflags, vs);
1879 	vn_lock(dvp, ltype | LK_RETRY);
1880 	if (VN_IS_DOOMED(dvp)) {
1881 		if (error == 0)
1882 			vput(*vpp);
1883 		*vpp = NULL;
1884 		return (ENOENT);
1885 	}
1886 	if (error) {
1887 		*vpp = NULL;
1888 		goto retry;
1889 	}
1890 	return (-1);
1891 negative_success:
1892 	if (__predict_false(cnp->cn_nameiop == CREATE)) {
1893 		if (cnp->cn_flags & ISLASTCN) {
1894 			counter_u64_add(numnegzaps, 1);
1895 			cache_zap_negative_locked_vnode_kl(ncp, dvp);
1896 			mtx_unlock(dvlp);
1897 			cache_free(ncp);
1898 			return (0);
1899 		}
1900 	}
1901 
1902 	whiteout = (ncp->nc_flag & NCF_WHITE);
1903 	cache_out_ts(ncp, tsp, ticksp);
1904 	if (cache_neg_hit_prep(ncp))
1905 		cache_neg_promote(ncp);
1906 	else
1907 		cache_neg_hit_finish(ncp);
1908 	mtx_unlock(dvlp);
1909 	if (whiteout)
1910 		cnp->cn_flags |= ISWHITEOUT;
1911 	return (ENOENT);
1912 }
1913 
1914 /**
1915  * Lookup a name in the name cache
1916  *
1917  * # Arguments
1918  *
1919  * - dvp:	Parent directory in which to search.
1920  * - vpp:	Return argument.  Will contain desired vnode on cache hit.
1921  * - cnp:	Parameters of the name search.  The most interesting bits of
1922  *   		the cn_flags field have the following meanings:
1923  *   	- MAKEENTRY:	If clear, free an entry from the cache rather than look
1924  *   			it up.
1925  *   	- ISDOTDOT:	Must be set if and only if cn_nameptr == ".."
1926  * - tsp:	Return storage for cache timestamp.  On a successful (positive
1927  *   		or negative) lookup, tsp will be filled with any timespec that
1928  *   		was stored when this cache entry was created.  However, it will
1929  *   		be clear for "." entries.
1930  * - ticks:	Return storage for alternate cache timestamp.  On a successful
1931  *   		(positive or negative) lookup, it will contain the ticks value
1932  *   		that was current when the cache entry was created, unless cnp
1933  *   		was ".".
1934  *
1935  * Either both tsp and ticks have to be provided or neither of them.
1936  *
1937  * # Returns
1938  *
1939  * - -1:	A positive cache hit.  vpp will contain the desired vnode.
1940  * - ENOENT:	A negative cache hit, or dvp was recycled out from under us due
1941  *		to a forced unmount.  vpp will not be modified.  If the entry
1942  *		is a whiteout, then the ISWHITEOUT flag will be set in
1943  *		cnp->cn_flags.
1944  * - 0:		A cache miss.  vpp will not be modified.
1945  *
1946  * # Locking
1947  *
1948  * On a cache hit, vpp will be returned locked and ref'd.  If we're looking up
1949  * .., dvp is unlocked.  If we're looking up . an extra ref is taken, but the
1950  * lock is not recursively acquired.
1951  */
1952 static int __noinline
1953 cache_lookup_fallback(struct vnode *dvp, struct vnode **vpp, struct componentname *cnp,
1954     struct timespec *tsp, int *ticksp)
1955 {
1956 	struct namecache *ncp;
1957 	struct mtx *blp;
1958 	uint32_t hash;
1959 	enum vgetstate vs;
1960 	int error;
1961 	bool whiteout;
1962 
1963 	MPASS((cnp->cn_flags & ISDOTDOT) == 0);
1964 	MPASS((cnp->cn_flags & (MAKEENTRY | NC_KEEPPOSENTRY)) != 0);
1965 
1966 retry:
1967 	hash = cache_get_hash(cnp->cn_nameptr, cnp->cn_namelen, dvp);
1968 	blp = HASH2BUCKETLOCK(hash);
1969 	mtx_lock(blp);
1970 
1971 	CK_SLIST_FOREACH(ncp, (NCHHASH(hash)), nc_hash) {
1972 		if (ncp->nc_dvp == dvp && ncp->nc_nlen == cnp->cn_namelen &&
1973 		    !bcmp(ncp->nc_name, cnp->cn_nameptr, ncp->nc_nlen))
1974 			break;
1975 	}
1976 
1977 	if (__predict_false(ncp == NULL)) {
1978 		mtx_unlock(blp);
1979 		SDT_PROBE2(vfs, namecache, lookup, miss, dvp, cnp->cn_nameptr);
1980 		counter_u64_add(nummiss, 1);
1981 		return (0);
1982 	}
1983 
1984 	if (ncp->nc_flag & NCF_NEGATIVE)
1985 		goto negative_success;
1986 
1987 	counter_u64_add(numposhits, 1);
1988 	*vpp = ncp->nc_vp;
1989 	SDT_PROBE3(vfs, namecache, lookup, hit, dvp, ncp->nc_name, *vpp);
1990 	cache_out_ts(ncp, tsp, ticksp);
1991 	MPASS(dvp != *vpp);
1992 	vs = vget_prep(*vpp);
1993 	mtx_unlock(blp);
1994 	error = vget_finish(*vpp, cnp->cn_lkflags, vs);
1995 	if (error) {
1996 		*vpp = NULL;
1997 		goto retry;
1998 	}
1999 	return (-1);
2000 negative_success:
2001 	/*
2002 	 * We don't get here with regular lookup apart from corner cases.
2003 	 */
2004 	if (__predict_true(cnp->cn_nameiop == CREATE)) {
2005 		if (cnp->cn_flags & ISLASTCN) {
2006 			counter_u64_add(numnegzaps, 1);
2007 			error = cache_zap_locked_bucket(ncp, cnp, hash, blp);
2008 			if (__predict_false(error != 0)) {
2009 				zap_bucket_fail2++;
2010 				goto retry;
2011 			}
2012 			cache_free(ncp);
2013 			return (0);
2014 		}
2015 	}
2016 
2017 	whiteout = (ncp->nc_flag & NCF_WHITE);
2018 	cache_out_ts(ncp, tsp, ticksp);
2019 	if (cache_neg_hit_prep(ncp))
2020 		cache_neg_promote(ncp);
2021 	else
2022 		cache_neg_hit_finish(ncp);
2023 	mtx_unlock(blp);
2024 	if (whiteout)
2025 		cnp->cn_flags |= ISWHITEOUT;
2026 	return (ENOENT);
2027 }
2028 
2029 int
2030 cache_lookup(struct vnode *dvp, struct vnode **vpp, struct componentname *cnp,
2031     struct timespec *tsp, int *ticksp)
2032 {
2033 	struct namecache *ncp;
2034 	uint32_t hash;
2035 	enum vgetstate vs;
2036 	int error;
2037 	bool whiteout, neg_promote;
2038 	u_short nc_flag;
2039 
2040 	MPASS((tsp == NULL && ticksp == NULL) || (tsp != NULL && ticksp != NULL));
2041 
2042 #ifdef DEBUG_CACHE
2043 	if (__predict_false(!doingcache)) {
2044 		cnp->cn_flags &= ~MAKEENTRY;
2045 		return (0);
2046 	}
2047 #endif
2048 
2049 	if (__predict_false(cnp->cn_nameptr[0] == '.')) {
2050 		if (cnp->cn_namelen == 1)
2051 			return (cache_lookup_dot(dvp, vpp, cnp, tsp, ticksp));
2052 		if (cnp->cn_namelen == 2 && cnp->cn_nameptr[1] == '.')
2053 			return (cache_lookup_dotdot(dvp, vpp, cnp, tsp, ticksp));
2054 	}
2055 
2056 	MPASS((cnp->cn_flags & ISDOTDOT) == 0);
2057 
2058 	if ((cnp->cn_flags & (MAKEENTRY | NC_KEEPPOSENTRY)) == 0) {
2059 		cache_remove_cnp(dvp, cnp);
2060 		return (0);
2061 	}
2062 
2063 	hash = cache_get_hash(cnp->cn_nameptr, cnp->cn_namelen, dvp);
2064 	vfs_smr_enter();
2065 
2066 	CK_SLIST_FOREACH(ncp, (NCHHASH(hash)), nc_hash) {
2067 		if (ncp->nc_dvp == dvp && ncp->nc_nlen == cnp->cn_namelen &&
2068 		    !bcmp(ncp->nc_name, cnp->cn_nameptr, ncp->nc_nlen))
2069 			break;
2070 	}
2071 
2072 	if (__predict_false(ncp == NULL)) {
2073 		vfs_smr_exit();
2074 		SDT_PROBE2(vfs, namecache, lookup, miss, dvp, cnp->cn_nameptr);
2075 		counter_u64_add(nummiss, 1);
2076 		return (0);
2077 	}
2078 
2079 	nc_flag = atomic_load_char(&ncp->nc_flag);
2080 	if (nc_flag & NCF_NEGATIVE)
2081 		goto negative_success;
2082 
2083 	counter_u64_add(numposhits, 1);
2084 	*vpp = ncp->nc_vp;
2085 	SDT_PROBE3(vfs, namecache, lookup, hit, dvp, ncp->nc_name, *vpp);
2086 	cache_out_ts(ncp, tsp, ticksp);
2087 	MPASS(dvp != *vpp);
2088 	if (!cache_ncp_canuse(ncp)) {
2089 		vfs_smr_exit();
2090 		*vpp = NULL;
2091 		goto out_fallback;
2092 	}
2093 	vs = vget_prep_smr(*vpp);
2094 	vfs_smr_exit();
2095 	if (__predict_false(vs == VGET_NONE)) {
2096 		*vpp = NULL;
2097 		goto out_fallback;
2098 	}
2099 	error = vget_finish(*vpp, cnp->cn_lkflags, vs);
2100 	if (error) {
2101 		*vpp = NULL;
2102 		goto out_fallback;
2103 	}
2104 	return (-1);
2105 negative_success:
2106 	if (cnp->cn_nameiop == CREATE) {
2107 		if (cnp->cn_flags & ISLASTCN) {
2108 			vfs_smr_exit();
2109 			goto out_fallback;
2110 		}
2111 	}
2112 
2113 	cache_out_ts(ncp, tsp, ticksp);
2114 	whiteout = (atomic_load_char(&ncp->nc_flag) & NCF_WHITE);
2115 	neg_promote = cache_neg_hit_prep(ncp);
2116 	if (!cache_ncp_canuse(ncp)) {
2117 		cache_neg_hit_abort(ncp);
2118 		vfs_smr_exit();
2119 		goto out_fallback;
2120 	}
2121 	if (neg_promote) {
2122 		vfs_smr_exit();
2123 		if (!cache_neg_promote_cond(dvp, cnp, ncp, hash))
2124 			goto out_fallback;
2125 	} else {
2126 		cache_neg_hit_finish(ncp);
2127 		vfs_smr_exit();
2128 	}
2129 	if (whiteout)
2130 		cnp->cn_flags |= ISWHITEOUT;
2131 	return (ENOENT);
2132 out_fallback:
2133 	return (cache_lookup_fallback(dvp, vpp, cnp, tsp, ticksp));
2134 }
2135 
2136 struct celockstate {
2137 	struct mtx *vlp[3];
2138 	struct mtx *blp[2];
2139 };
2140 CTASSERT((nitems(((struct celockstate *)0)->vlp) == 3));
2141 CTASSERT((nitems(((struct celockstate *)0)->blp) == 2));
2142 
2143 static inline void
2144 cache_celockstate_init(struct celockstate *cel)
2145 {
2146 
2147 	bzero(cel, sizeof(*cel));
2148 }
2149 
2150 static void
2151 cache_lock_vnodes_cel(struct celockstate *cel, struct vnode *vp,
2152     struct vnode *dvp)
2153 {
2154 	struct mtx *vlp1, *vlp2;
2155 
2156 	MPASS(cel->vlp[0] == NULL);
2157 	MPASS(cel->vlp[1] == NULL);
2158 	MPASS(cel->vlp[2] == NULL);
2159 
2160 	MPASS(vp != NULL || dvp != NULL);
2161 
2162 	vlp1 = VP2VNODELOCK(vp);
2163 	vlp2 = VP2VNODELOCK(dvp);
2164 	cache_sort_vnodes(&vlp1, &vlp2);
2165 
2166 	if (vlp1 != NULL) {
2167 		mtx_lock(vlp1);
2168 		cel->vlp[0] = vlp1;
2169 	}
2170 	mtx_lock(vlp2);
2171 	cel->vlp[1] = vlp2;
2172 }
2173 
2174 static void
2175 cache_unlock_vnodes_cel(struct celockstate *cel)
2176 {
2177 
2178 	MPASS(cel->vlp[0] != NULL || cel->vlp[1] != NULL);
2179 
2180 	if (cel->vlp[0] != NULL)
2181 		mtx_unlock(cel->vlp[0]);
2182 	if (cel->vlp[1] != NULL)
2183 		mtx_unlock(cel->vlp[1]);
2184 	if (cel->vlp[2] != NULL)
2185 		mtx_unlock(cel->vlp[2]);
2186 }
2187 
2188 static bool
2189 cache_lock_vnodes_cel_3(struct celockstate *cel, struct vnode *vp)
2190 {
2191 	struct mtx *vlp;
2192 	bool ret;
2193 
2194 	cache_assert_vlp_locked(cel->vlp[0]);
2195 	cache_assert_vlp_locked(cel->vlp[1]);
2196 	MPASS(cel->vlp[2] == NULL);
2197 
2198 	MPASS(vp != NULL);
2199 	vlp = VP2VNODELOCK(vp);
2200 
2201 	ret = true;
2202 	if (vlp >= cel->vlp[1]) {
2203 		mtx_lock(vlp);
2204 	} else {
2205 		if (mtx_trylock(vlp))
2206 			goto out;
2207 		cache_lock_vnodes_cel_3_failures++;
2208 		cache_unlock_vnodes_cel(cel);
2209 		if (vlp < cel->vlp[0]) {
2210 			mtx_lock(vlp);
2211 			mtx_lock(cel->vlp[0]);
2212 			mtx_lock(cel->vlp[1]);
2213 		} else {
2214 			if (cel->vlp[0] != NULL)
2215 				mtx_lock(cel->vlp[0]);
2216 			mtx_lock(vlp);
2217 			mtx_lock(cel->vlp[1]);
2218 		}
2219 		ret = false;
2220 	}
2221 out:
2222 	cel->vlp[2] = vlp;
2223 	return (ret);
2224 }
2225 
2226 static void
2227 cache_lock_buckets_cel(struct celockstate *cel, struct mtx *blp1,
2228     struct mtx *blp2)
2229 {
2230 
2231 	MPASS(cel->blp[0] == NULL);
2232 	MPASS(cel->blp[1] == NULL);
2233 
2234 	cache_sort_vnodes(&blp1, &blp2);
2235 
2236 	if (blp1 != NULL) {
2237 		mtx_lock(blp1);
2238 		cel->blp[0] = blp1;
2239 	}
2240 	mtx_lock(blp2);
2241 	cel->blp[1] = blp2;
2242 }
2243 
2244 static void
2245 cache_unlock_buckets_cel(struct celockstate *cel)
2246 {
2247 
2248 	if (cel->blp[0] != NULL)
2249 		mtx_unlock(cel->blp[0]);
2250 	mtx_unlock(cel->blp[1]);
2251 }
2252 
2253 /*
2254  * Lock part of the cache affected by the insertion.
2255  *
2256  * This means vnodelocks for dvp, vp and the relevant bucketlock.
2257  * However, insertion can result in removal of an old entry. In this
2258  * case we have an additional vnode and bucketlock pair to lock.
2259  *
2260  * That is, in the worst case we have to lock 3 vnodes and 2 bucketlocks, while
2261  * preserving the locking order (smaller address first).
2262  */
2263 static void
2264 cache_enter_lock(struct celockstate *cel, struct vnode *dvp, struct vnode *vp,
2265     uint32_t hash)
2266 {
2267 	struct namecache *ncp;
2268 	struct mtx *blps[2];
2269 	u_char nc_flag;
2270 
2271 	blps[0] = HASH2BUCKETLOCK(hash);
2272 	for (;;) {
2273 		blps[1] = NULL;
2274 		cache_lock_vnodes_cel(cel, dvp, vp);
2275 		if (vp == NULL || vp->v_type != VDIR)
2276 			break;
2277 		ncp = atomic_load_consume_ptr(&vp->v_cache_dd);
2278 		if (ncp == NULL)
2279 			break;
2280 		nc_flag = atomic_load_char(&ncp->nc_flag);
2281 		if ((nc_flag & NCF_ISDOTDOT) == 0)
2282 			break;
2283 		MPASS(ncp->nc_dvp == vp);
2284 		blps[1] = NCP2BUCKETLOCK(ncp);
2285 		if ((nc_flag & NCF_NEGATIVE) != 0)
2286 			break;
2287 		if (cache_lock_vnodes_cel_3(cel, ncp->nc_vp))
2288 			break;
2289 		/*
2290 		 * All vnodes got re-locked. Re-validate the state and if
2291 		 * nothing changed we are done. Otherwise restart.
2292 		 */
2293 		if (ncp == vp->v_cache_dd &&
2294 		    (ncp->nc_flag & NCF_ISDOTDOT) != 0 &&
2295 		    blps[1] == NCP2BUCKETLOCK(ncp) &&
2296 		    VP2VNODELOCK(ncp->nc_vp) == cel->vlp[2])
2297 			break;
2298 		cache_unlock_vnodes_cel(cel);
2299 		cel->vlp[0] = NULL;
2300 		cel->vlp[1] = NULL;
2301 		cel->vlp[2] = NULL;
2302 	}
2303 	cache_lock_buckets_cel(cel, blps[0], blps[1]);
2304 }
2305 
2306 static void
2307 cache_enter_lock_dd(struct celockstate *cel, struct vnode *dvp, struct vnode *vp,
2308     uint32_t hash)
2309 {
2310 	struct namecache *ncp;
2311 	struct mtx *blps[2];
2312 	u_char nc_flag;
2313 
2314 	blps[0] = HASH2BUCKETLOCK(hash);
2315 	for (;;) {
2316 		blps[1] = NULL;
2317 		cache_lock_vnodes_cel(cel, dvp, vp);
2318 		ncp = atomic_load_consume_ptr(&dvp->v_cache_dd);
2319 		if (ncp == NULL)
2320 			break;
2321 		nc_flag = atomic_load_char(&ncp->nc_flag);
2322 		if ((nc_flag & NCF_ISDOTDOT) == 0)
2323 			break;
2324 		MPASS(ncp->nc_dvp == dvp);
2325 		blps[1] = NCP2BUCKETLOCK(ncp);
2326 		if ((nc_flag & NCF_NEGATIVE) != 0)
2327 			break;
2328 		if (cache_lock_vnodes_cel_3(cel, ncp->nc_vp))
2329 			break;
2330 		if (ncp == dvp->v_cache_dd &&
2331 		    (ncp->nc_flag & NCF_ISDOTDOT) != 0 &&
2332 		    blps[1] == NCP2BUCKETLOCK(ncp) &&
2333 		    VP2VNODELOCK(ncp->nc_vp) == cel->vlp[2])
2334 			break;
2335 		cache_unlock_vnodes_cel(cel);
2336 		cel->vlp[0] = NULL;
2337 		cel->vlp[1] = NULL;
2338 		cel->vlp[2] = NULL;
2339 	}
2340 	cache_lock_buckets_cel(cel, blps[0], blps[1]);
2341 }
2342 
2343 static void
2344 cache_enter_unlock(struct celockstate *cel)
2345 {
2346 
2347 	cache_unlock_buckets_cel(cel);
2348 	cache_unlock_vnodes_cel(cel);
2349 }
2350 
2351 static void __noinline
2352 cache_enter_dotdot_prep(struct vnode *dvp, struct vnode *vp,
2353     struct componentname *cnp)
2354 {
2355 	struct celockstate cel;
2356 	struct namecache *ncp;
2357 	uint32_t hash;
2358 	int len;
2359 
2360 	if (atomic_load_ptr(&dvp->v_cache_dd) == NULL)
2361 		return;
2362 	len = cnp->cn_namelen;
2363 	cache_celockstate_init(&cel);
2364 	hash = cache_get_hash(cnp->cn_nameptr, len, dvp);
2365 	cache_enter_lock_dd(&cel, dvp, vp, hash);
2366 	ncp = dvp->v_cache_dd;
2367 	if (ncp != NULL && (ncp->nc_flag & NCF_ISDOTDOT)) {
2368 		KASSERT(ncp->nc_dvp == dvp, ("wrong isdotdot parent"));
2369 		cache_zap_locked(ncp);
2370 	} else {
2371 		ncp = NULL;
2372 	}
2373 	atomic_store_ptr(&dvp->v_cache_dd, NULL);
2374 	cache_enter_unlock(&cel);
2375 	if (ncp != NULL)
2376 		cache_free(ncp);
2377 }
2378 
2379 /*
2380  * Add an entry to the cache.
2381  */
2382 void
2383 cache_enter_time(struct vnode *dvp, struct vnode *vp, struct componentname *cnp,
2384     struct timespec *tsp, struct timespec *dtsp)
2385 {
2386 	struct celockstate cel;
2387 	struct namecache *ncp, *n2, *ndd;
2388 	struct namecache_ts *ncp_ts;
2389 	struct nchashhead *ncpp;
2390 	uint32_t hash;
2391 	int flag;
2392 	int len;
2393 
2394 	KASSERT(cnp->cn_namelen <= NAME_MAX,
2395 	    ("%s: passed len %ld exceeds NAME_MAX (%d)", __func__, cnp->cn_namelen,
2396 	    NAME_MAX));
2397 #ifdef notyet
2398 	/*
2399 	 * Not everything doing this is weeded out yet.
2400 	 */
2401 	VNPASS(dvp != vp, dvp);
2402 #endif
2403 	VNPASS(!VN_IS_DOOMED(dvp), dvp);
2404 	VNPASS(dvp->v_type != VNON, dvp);
2405 	if (vp != NULL) {
2406 		VNPASS(!VN_IS_DOOMED(vp), vp);
2407 		VNPASS(vp->v_type != VNON, vp);
2408 	}
2409 
2410 #ifdef DEBUG_CACHE
2411 	if (__predict_false(!doingcache))
2412 		return;
2413 #endif
2414 
2415 	flag = 0;
2416 	if (__predict_false(cnp->cn_nameptr[0] == '.')) {
2417 		if (cnp->cn_namelen == 1)
2418 			return;
2419 		if (cnp->cn_namelen == 2 && cnp->cn_nameptr[1] == '.') {
2420 			cache_enter_dotdot_prep(dvp, vp, cnp);
2421 			flag = NCF_ISDOTDOT;
2422 		}
2423 	}
2424 
2425 	ncp = cache_alloc(cnp->cn_namelen, tsp != NULL);
2426 	if (ncp == NULL)
2427 		return;
2428 
2429 	cache_celockstate_init(&cel);
2430 	ndd = NULL;
2431 	ncp_ts = NULL;
2432 
2433 	/*
2434 	 * Calculate the hash key and setup as much of the new
2435 	 * namecache entry as possible before acquiring the lock.
2436 	 */
2437 	ncp->nc_flag = flag | NCF_WIP;
2438 	ncp->nc_vp = vp;
2439 	if (vp == NULL)
2440 		cache_neg_init(ncp);
2441 	ncp->nc_dvp = dvp;
2442 	if (tsp != NULL) {
2443 		ncp_ts = __containerof(ncp, struct namecache_ts, nc_nc);
2444 		ncp_ts->nc_time = *tsp;
2445 		ncp_ts->nc_ticks = ticks;
2446 		ncp_ts->nc_nc.nc_flag |= NCF_TS;
2447 		if (dtsp != NULL) {
2448 			ncp_ts->nc_dotdottime = *dtsp;
2449 			ncp_ts->nc_nc.nc_flag |= NCF_DTS;
2450 		}
2451 	}
2452 	len = ncp->nc_nlen = cnp->cn_namelen;
2453 	hash = cache_get_hash(cnp->cn_nameptr, len, dvp);
2454 	memcpy(ncp->nc_name, cnp->cn_nameptr, len);
2455 	ncp->nc_name[len] = '\0';
2456 	cache_enter_lock(&cel, dvp, vp, hash);
2457 
2458 	/*
2459 	 * See if this vnode or negative entry is already in the cache
2460 	 * with this name.  This can happen with concurrent lookups of
2461 	 * the same path name.
2462 	 */
2463 	ncpp = NCHHASH(hash);
2464 	CK_SLIST_FOREACH(n2, ncpp, nc_hash) {
2465 		if (n2->nc_dvp == dvp &&
2466 		    n2->nc_nlen == cnp->cn_namelen &&
2467 		    !bcmp(n2->nc_name, cnp->cn_nameptr, n2->nc_nlen)) {
2468 			MPASS(cache_ncp_canuse(n2));
2469 			if ((n2->nc_flag & NCF_NEGATIVE) != 0)
2470 				KASSERT(vp == NULL,
2471 				    ("%s: found entry pointing to a different vnode (%p != %p) ; name [%s]",
2472 				    __func__, NULL, vp, cnp->cn_nameptr));
2473 			else
2474 				KASSERT(n2->nc_vp == vp,
2475 				    ("%s: found entry pointing to a different vnode (%p != %p) ; name [%s]",
2476 				    __func__, n2->nc_vp, vp, cnp->cn_nameptr));
2477 			/*
2478 			 * Entries are supposed to be immutable unless in the
2479 			 * process of getting destroyed. Accommodating for
2480 			 * changing timestamps is possible but not worth it.
2481 			 * This should be harmless in terms of correctness, in
2482 			 * the worst case resulting in an earlier expiration.
2483 			 * Alternatively, the found entry can be replaced
2484 			 * altogether.
2485 			 */
2486 			MPASS((n2->nc_flag & (NCF_TS | NCF_DTS)) == (ncp->nc_flag & (NCF_TS | NCF_DTS)));
2487 #if 0
2488 			if (tsp != NULL) {
2489 				KASSERT((n2->nc_flag & NCF_TS) != 0,
2490 				    ("no NCF_TS"));
2491 				n2_ts = __containerof(n2, struct namecache_ts, nc_nc);
2492 				n2_ts->nc_time = ncp_ts->nc_time;
2493 				n2_ts->nc_ticks = ncp_ts->nc_ticks;
2494 				if (dtsp != NULL) {
2495 					n2_ts->nc_dotdottime = ncp_ts->nc_dotdottime;
2496 					n2_ts->nc_nc.nc_flag |= NCF_DTS;
2497 				}
2498 			}
2499 #endif
2500 			SDT_PROBE3(vfs, namecache, enter, duplicate, dvp, ncp->nc_name,
2501 			    vp);
2502 			goto out_unlock_free;
2503 		}
2504 	}
2505 
2506 	if (flag == NCF_ISDOTDOT) {
2507 		/*
2508 		 * See if we are trying to add .. entry, but some other lookup
2509 		 * has populated v_cache_dd pointer already.
2510 		 */
2511 		if (dvp->v_cache_dd != NULL)
2512 			goto out_unlock_free;
2513 		KASSERT(vp == NULL || vp->v_type == VDIR,
2514 		    ("wrong vnode type %p", vp));
2515 		atomic_thread_fence_rel();
2516 		atomic_store_ptr(&dvp->v_cache_dd, ncp);
2517 	}
2518 
2519 	if (vp != NULL) {
2520 		if (flag != NCF_ISDOTDOT) {
2521 			/*
2522 			 * For this case, the cache entry maps both the
2523 			 * directory name in it and the name ".." for the
2524 			 * directory's parent.
2525 			 */
2526 			if ((ndd = vp->v_cache_dd) != NULL) {
2527 				if ((ndd->nc_flag & NCF_ISDOTDOT) != 0)
2528 					cache_zap_locked(ndd);
2529 				else
2530 					ndd = NULL;
2531 			}
2532 			atomic_thread_fence_rel();
2533 			atomic_store_ptr(&vp->v_cache_dd, ncp);
2534 		} else if (vp->v_type != VDIR) {
2535 			if (vp->v_cache_dd != NULL) {
2536 				atomic_store_ptr(&vp->v_cache_dd, NULL);
2537 			}
2538 		}
2539 	}
2540 
2541 	if (flag != NCF_ISDOTDOT) {
2542 		if (LIST_EMPTY(&dvp->v_cache_src)) {
2543 			cache_hold_vnode(dvp);
2544 		}
2545 		LIST_INSERT_HEAD(&dvp->v_cache_src, ncp, nc_src);
2546 	}
2547 
2548 	/*
2549 	 * If the entry is "negative", we place it into the
2550 	 * "negative" cache queue, otherwise, we place it into the
2551 	 * destination vnode's cache entries queue.
2552 	 */
2553 	if (vp != NULL) {
2554 		TAILQ_INSERT_HEAD(&vp->v_cache_dst, ncp, nc_dst);
2555 		SDT_PROBE3(vfs, namecache, enter, done, dvp, ncp->nc_name,
2556 		    vp);
2557 	} else {
2558 		if (cnp->cn_flags & ISWHITEOUT)
2559 			atomic_store_char(&ncp->nc_flag, ncp->nc_flag | NCF_WHITE);
2560 		cache_neg_insert(ncp);
2561 		SDT_PROBE2(vfs, namecache, enter_negative, done, dvp,
2562 		    ncp->nc_name);
2563 	}
2564 
2565 	/*
2566 	 * Insert the new namecache entry into the appropriate chain
2567 	 * within the cache entries table.
2568 	 */
2569 	CK_SLIST_INSERT_HEAD(ncpp, ncp, nc_hash);
2570 
2571 	atomic_thread_fence_rel();
2572 	/*
2573 	 * Mark the entry as fully constructed.
2574 	 * It is immutable past this point until its removal.
2575 	 */
2576 	atomic_store_char(&ncp->nc_flag, ncp->nc_flag & ~NCF_WIP);
2577 
2578 	cache_enter_unlock(&cel);
2579 	if (ndd != NULL)
2580 		cache_free(ndd);
2581 	return;
2582 out_unlock_free:
2583 	cache_enter_unlock(&cel);
2584 	cache_free(ncp);
2585 	return;
2586 }
2587 
2588 static u_int
2589 cache_roundup_2(u_int val)
2590 {
2591 	u_int res;
2592 
2593 	for (res = 1; res <= val; res <<= 1)
2594 		continue;
2595 
2596 	return (res);
2597 }
2598 
2599 static struct nchashhead *
2600 nchinittbl(u_long elements, u_long *hashmask)
2601 {
2602 	struct nchashhead *hashtbl;
2603 	u_long hashsize, i;
2604 
2605 	hashsize = cache_roundup_2(elements) / 2;
2606 
2607 	hashtbl = malloc((u_long)hashsize * sizeof(*hashtbl), M_VFSCACHE, M_WAITOK);
2608 	for (i = 0; i < hashsize; i++)
2609 		CK_SLIST_INIT(&hashtbl[i]);
2610 	*hashmask = hashsize - 1;
2611 	return (hashtbl);
2612 }
2613 
2614 static void
2615 ncfreetbl(struct nchashhead *hashtbl)
2616 {
2617 
2618 	free(hashtbl, M_VFSCACHE);
2619 }
2620 
2621 /*
2622  * Name cache initialization, from vfs_init() when we are booting
2623  */
2624 static void
2625 nchinit(void *dummy __unused)
2626 {
2627 	u_int i;
2628 
2629 	cache_zone_small = uma_zcreate("S VFS Cache", CACHE_ZONE_SMALL_SIZE,
2630 	    NULL, NULL, NULL, NULL, CACHE_ZONE_ALIGNMENT, UMA_ZONE_ZINIT);
2631 	cache_zone_small_ts = uma_zcreate("STS VFS Cache", CACHE_ZONE_SMALL_TS_SIZE,
2632 	    NULL, NULL, NULL, NULL, CACHE_ZONE_ALIGNMENT, UMA_ZONE_ZINIT);
2633 	cache_zone_large = uma_zcreate("L VFS Cache", CACHE_ZONE_LARGE_SIZE,
2634 	    NULL, NULL, NULL, NULL, CACHE_ZONE_ALIGNMENT, UMA_ZONE_ZINIT);
2635 	cache_zone_large_ts = uma_zcreate("LTS VFS Cache", CACHE_ZONE_LARGE_TS_SIZE,
2636 	    NULL, NULL, NULL, NULL, CACHE_ZONE_ALIGNMENT, UMA_ZONE_ZINIT);
2637 
2638 	VFS_SMR_ZONE_SET(cache_zone_small);
2639 	VFS_SMR_ZONE_SET(cache_zone_small_ts);
2640 	VFS_SMR_ZONE_SET(cache_zone_large);
2641 	VFS_SMR_ZONE_SET(cache_zone_large_ts);
2642 
2643 	ncsize = desiredvnodes * ncsizefactor;
2644 	cache_recalc_neg_min(ncnegminpct);
2645 	nchashtbl = nchinittbl(desiredvnodes * 2, &nchash);
2646 	ncbuckethash = cache_roundup_2(mp_ncpus * mp_ncpus) - 1;
2647 	if (ncbuckethash < 7) /* arbitrarily chosen to avoid having one lock */
2648 		ncbuckethash = 7;
2649 	if (ncbuckethash > nchash)
2650 		ncbuckethash = nchash;
2651 	bucketlocks = malloc(sizeof(*bucketlocks) * numbucketlocks, M_VFSCACHE,
2652 	    M_WAITOK | M_ZERO);
2653 	for (i = 0; i < numbucketlocks; i++)
2654 		mtx_init(&bucketlocks[i], "ncbuc", NULL, MTX_DUPOK | MTX_RECURSE);
2655 	ncvnodehash = ncbuckethash;
2656 	vnodelocks = malloc(sizeof(*vnodelocks) * numvnodelocks, M_VFSCACHE,
2657 	    M_WAITOK | M_ZERO);
2658 	for (i = 0; i < numvnodelocks; i++)
2659 		mtx_init(&vnodelocks[i], "ncvn", NULL, MTX_DUPOK | MTX_RECURSE);
2660 
2661 	for (i = 0; i < numneglists; i++) {
2662 		mtx_init(&neglists[i].nl_evict_lock, "ncnege", NULL, MTX_DEF);
2663 		mtx_init(&neglists[i].nl_lock, "ncnegl", NULL, MTX_DEF);
2664 		TAILQ_INIT(&neglists[i].nl_list);
2665 		TAILQ_INIT(&neglists[i].nl_hotlist);
2666 	}
2667 }
2668 SYSINIT(vfs, SI_SUB_VFS, SI_ORDER_SECOND, nchinit, NULL);
2669 
2670 void
2671 cache_vnode_init(struct vnode *vp)
2672 {
2673 
2674 	LIST_INIT(&vp->v_cache_src);
2675 	TAILQ_INIT(&vp->v_cache_dst);
2676 	vp->v_cache_dd = NULL;
2677 	cache_prehash(vp);
2678 }
2679 
2680 /*
2681  * Induce transient cache misses for lockless operation in cache_lookup() by
2682  * using a temporary hash table.
2683  *
2684  * This will force a fs lookup.
2685  *
2686  * Synchronisation is done in 2 steps, calling vfs_smr_synchronize each time
2687  * to observe all CPUs not performing the lookup.
2688  */
2689 static void
2690 cache_changesize_set_temp(struct nchashhead *temptbl, u_long temphash)
2691 {
2692 
2693 	MPASS(temphash < nchash);
2694 	/*
2695 	 * Change the size. The new size is smaller and can safely be used
2696 	 * against the existing table. All lookups which now hash wrong will
2697 	 * result in a cache miss, which all callers are supposed to know how
2698 	 * to handle.
2699 	 */
2700 	atomic_store_long(&nchash, temphash);
2701 	atomic_thread_fence_rel();
2702 	vfs_smr_synchronize();
2703 	/*
2704 	 * At this point everyone sees the updated hash value, but they still
2705 	 * see the old table.
2706 	 */
2707 	atomic_store_ptr(&nchashtbl, temptbl);
2708 	atomic_thread_fence_rel();
2709 	vfs_smr_synchronize();
2710 	/*
2711 	 * At this point everyone sees the updated table pointer and size pair.
2712 	 */
2713 }
2714 
2715 /*
2716  * Set the new hash table.
2717  *
2718  * Similarly to cache_changesize_set_temp(), this has to synchronize against
2719  * lockless operation in cache_lookup().
2720  */
2721 static void
2722 cache_changesize_set_new(struct nchashhead *new_tbl, u_long new_hash)
2723 {
2724 
2725 	MPASS(nchash < new_hash);
2726 	/*
2727 	 * Change the pointer first. This wont result in out of bounds access
2728 	 * since the temporary table is guaranteed to be smaller.
2729 	 */
2730 	atomic_store_ptr(&nchashtbl, new_tbl);
2731 	atomic_thread_fence_rel();
2732 	vfs_smr_synchronize();
2733 	/*
2734 	 * At this point everyone sees the updated pointer value, but they
2735 	 * still see the old size.
2736 	 */
2737 	atomic_store_long(&nchash, new_hash);
2738 	atomic_thread_fence_rel();
2739 	vfs_smr_synchronize();
2740 	/*
2741 	 * At this point everyone sees the updated table pointer and size pair.
2742 	 */
2743 }
2744 
2745 void
2746 cache_changesize(u_long newmaxvnodes)
2747 {
2748 	struct nchashhead *new_nchashtbl, *old_nchashtbl, *temptbl;
2749 	u_long new_nchash, old_nchash, temphash;
2750 	struct namecache *ncp;
2751 	uint32_t hash;
2752 	u_long newncsize;
2753 	int i;
2754 
2755 	newncsize = newmaxvnodes * ncsizefactor;
2756 	newmaxvnodes = cache_roundup_2(newmaxvnodes * 2);
2757 	if (newmaxvnodes < numbucketlocks)
2758 		newmaxvnodes = numbucketlocks;
2759 
2760 	new_nchashtbl = nchinittbl(newmaxvnodes, &new_nchash);
2761 	/* If same hash table size, nothing to do */
2762 	if (nchash == new_nchash) {
2763 		ncfreetbl(new_nchashtbl);
2764 		return;
2765 	}
2766 
2767 	temptbl = nchinittbl(1, &temphash);
2768 
2769 	/*
2770 	 * Move everything from the old hash table to the new table.
2771 	 * None of the namecache entries in the table can be removed
2772 	 * because to do so, they have to be removed from the hash table.
2773 	 */
2774 	cache_fplookup_lockout();
2775 	cache_lock_all_vnodes();
2776 	cache_lock_all_buckets();
2777 	old_nchashtbl = nchashtbl;
2778 	old_nchash = nchash;
2779 	cache_changesize_set_temp(temptbl, temphash);
2780 	for (i = 0; i <= old_nchash; i++) {
2781 		while ((ncp = CK_SLIST_FIRST(&old_nchashtbl[i])) != NULL) {
2782 			hash = cache_get_hash(ncp->nc_name, ncp->nc_nlen,
2783 			    ncp->nc_dvp);
2784 			CK_SLIST_REMOVE(&old_nchashtbl[i], ncp, namecache, nc_hash);
2785 			CK_SLIST_INSERT_HEAD(&new_nchashtbl[hash & new_nchash], ncp, nc_hash);
2786 		}
2787 	}
2788 	ncsize = newncsize;
2789 	cache_recalc_neg_min(ncnegminpct);
2790 	cache_changesize_set_new(new_nchashtbl, new_nchash);
2791 	cache_unlock_all_buckets();
2792 	cache_unlock_all_vnodes();
2793 	cache_fplookup_restore();
2794 	ncfreetbl(old_nchashtbl);
2795 	ncfreetbl(temptbl);
2796 }
2797 
2798 /*
2799  * Remove all entries from and to a particular vnode.
2800  */
2801 static void
2802 cache_purge_impl(struct vnode *vp)
2803 {
2804 	struct cache_freebatch batch;
2805 	struct namecache *ncp;
2806 	struct mtx *vlp, *vlp2;
2807 
2808 	TAILQ_INIT(&batch);
2809 	vlp = VP2VNODELOCK(vp);
2810 	vlp2 = NULL;
2811 	mtx_lock(vlp);
2812 retry:
2813 	while (!LIST_EMPTY(&vp->v_cache_src)) {
2814 		ncp = LIST_FIRST(&vp->v_cache_src);
2815 		if (!cache_zap_locked_vnode_kl2(ncp, vp, &vlp2))
2816 			goto retry;
2817 		TAILQ_INSERT_TAIL(&batch, ncp, nc_dst);
2818 	}
2819 	while (!TAILQ_EMPTY(&vp->v_cache_dst)) {
2820 		ncp = TAILQ_FIRST(&vp->v_cache_dst);
2821 		if (!cache_zap_locked_vnode_kl2(ncp, vp, &vlp2))
2822 			goto retry;
2823 		TAILQ_INSERT_TAIL(&batch, ncp, nc_dst);
2824 	}
2825 	ncp = vp->v_cache_dd;
2826 	if (ncp != NULL) {
2827 		KASSERT(ncp->nc_flag & NCF_ISDOTDOT,
2828 		   ("lost dotdot link"));
2829 		if (!cache_zap_locked_vnode_kl2(ncp, vp, &vlp2))
2830 			goto retry;
2831 		TAILQ_INSERT_TAIL(&batch, ncp, nc_dst);
2832 	}
2833 	KASSERT(vp->v_cache_dd == NULL, ("incomplete purge"));
2834 	mtx_unlock(vlp);
2835 	if (vlp2 != NULL)
2836 		mtx_unlock(vlp2);
2837 	cache_free_batch(&batch);
2838 }
2839 
2840 /*
2841  * Opportunistic check to see if there is anything to do.
2842  */
2843 static bool
2844 cache_has_entries(struct vnode *vp)
2845 {
2846 
2847 	if (LIST_EMPTY(&vp->v_cache_src) && TAILQ_EMPTY(&vp->v_cache_dst) &&
2848 	    atomic_load_ptr(&vp->v_cache_dd) == NULL)
2849 		return (false);
2850 	return (true);
2851 }
2852 
2853 void
2854 cache_purge(struct vnode *vp)
2855 {
2856 
2857 	SDT_PROBE1(vfs, namecache, purge, done, vp);
2858 	if (!cache_has_entries(vp))
2859 		return;
2860 	cache_purge_impl(vp);
2861 }
2862 
2863 /*
2864  * Only to be used by vgone.
2865  */
2866 void
2867 cache_purge_vgone(struct vnode *vp)
2868 {
2869 	struct mtx *vlp;
2870 
2871 	VNPASS(VN_IS_DOOMED(vp), vp);
2872 	if (cache_has_entries(vp)) {
2873 		cache_purge_impl(vp);
2874 		return;
2875 	}
2876 
2877 	/*
2878 	 * Serialize against a potential thread doing cache_purge.
2879 	 */
2880 	vlp = VP2VNODELOCK(vp);
2881 	mtx_wait_unlocked(vlp);
2882 	if (cache_has_entries(vp)) {
2883 		cache_purge_impl(vp);
2884 		return;
2885 	}
2886 	return;
2887 }
2888 
2889 /*
2890  * Remove all negative entries for a particular directory vnode.
2891  */
2892 void
2893 cache_purge_negative(struct vnode *vp)
2894 {
2895 	struct cache_freebatch batch;
2896 	struct namecache *ncp, *nnp;
2897 	struct mtx *vlp;
2898 
2899 	SDT_PROBE1(vfs, namecache, purge_negative, done, vp);
2900 	if (LIST_EMPTY(&vp->v_cache_src))
2901 		return;
2902 	TAILQ_INIT(&batch);
2903 	vlp = VP2VNODELOCK(vp);
2904 	mtx_lock(vlp);
2905 	LIST_FOREACH_SAFE(ncp, &vp->v_cache_src, nc_src, nnp) {
2906 		if (!(ncp->nc_flag & NCF_NEGATIVE))
2907 			continue;
2908 		cache_zap_negative_locked_vnode_kl(ncp, vp);
2909 		TAILQ_INSERT_TAIL(&batch, ncp, nc_dst);
2910 	}
2911 	mtx_unlock(vlp);
2912 	cache_free_batch(&batch);
2913 }
2914 
2915 /*
2916  * Entry points for modifying VOP operations.
2917  */
2918 void
2919 cache_vop_rename(struct vnode *fdvp, struct vnode *fvp, struct vnode *tdvp,
2920     struct vnode *tvp, struct componentname *fcnp, struct componentname *tcnp)
2921 {
2922 
2923 	ASSERT_VOP_IN_SEQC(fdvp);
2924 	ASSERT_VOP_IN_SEQC(fvp);
2925 	ASSERT_VOP_IN_SEQC(tdvp);
2926 	if (tvp != NULL)
2927 		ASSERT_VOP_IN_SEQC(tvp);
2928 
2929 	cache_purge(fvp);
2930 	if (tvp != NULL) {
2931 		cache_purge(tvp);
2932 		KASSERT(!cache_remove_cnp(tdvp, tcnp),
2933 		    ("%s: lingering negative entry", __func__));
2934 	} else {
2935 		cache_remove_cnp(tdvp, tcnp);
2936 	}
2937 
2938 	/*
2939 	 * TODO
2940 	 *
2941 	 * Historically renaming was always purging all revelang entries,
2942 	 * but that's quite wasteful. In particular turns out that in many cases
2943 	 * the target file is immediately accessed after rename, inducing a cache
2944 	 * miss.
2945 	 *
2946 	 * Recode this to reduce relocking and reuse the existing entry (if any)
2947 	 * instead of just removing it above and allocating a new one here.
2948 	 */
2949 	if (cache_rename_add) {
2950 		cache_enter(tdvp, fvp, tcnp);
2951 	}
2952 }
2953 
2954 void
2955 cache_vop_rmdir(struct vnode *dvp, struct vnode *vp)
2956 {
2957 
2958 	ASSERT_VOP_IN_SEQC(dvp);
2959 	ASSERT_VOP_IN_SEQC(vp);
2960 	cache_purge(vp);
2961 }
2962 
2963 #ifdef INVARIANTS
2964 /*
2965  * Validate that if an entry exists it matches.
2966  */
2967 void
2968 cache_validate(struct vnode *dvp, struct vnode *vp, struct componentname *cnp)
2969 {
2970 	struct namecache *ncp;
2971 	struct mtx *blp;
2972 	uint32_t hash;
2973 
2974 	hash = cache_get_hash(cnp->cn_nameptr, cnp->cn_namelen, dvp);
2975 	if (CK_SLIST_EMPTY(NCHHASH(hash)))
2976 		return;
2977 	blp = HASH2BUCKETLOCK(hash);
2978 	mtx_lock(blp);
2979 	CK_SLIST_FOREACH(ncp, (NCHHASH(hash)), nc_hash) {
2980 		if (ncp->nc_dvp == dvp && ncp->nc_nlen == cnp->cn_namelen &&
2981 		    !bcmp(ncp->nc_name, cnp->cn_nameptr, ncp->nc_nlen)) {
2982 			if (ncp->nc_vp != vp)
2983 				panic("%s: mismatch (%p != %p); ncp %p [%s] dvp %p\n",
2984 				    __func__, vp, ncp->nc_vp, ncp, ncp->nc_name, ncp->nc_dvp);
2985 		}
2986 	}
2987 	mtx_unlock(blp);
2988 }
2989 #endif
2990 
2991 /*
2992  * Flush all entries referencing a particular filesystem.
2993  */
2994 void
2995 cache_purgevfs(struct mount *mp)
2996 {
2997 	struct vnode *vp, *mvp;
2998 
2999 	SDT_PROBE1(vfs, namecache, purgevfs, done, mp);
3000 	/*
3001 	 * Somewhat wasteful iteration over all vnodes. Would be better to
3002 	 * support filtering and avoid the interlock to begin with.
3003 	 */
3004 	MNT_VNODE_FOREACH_ALL(vp, mp, mvp) {
3005 		if (!cache_has_entries(vp)) {
3006 			VI_UNLOCK(vp);
3007 			continue;
3008 		}
3009 		vholdl(vp);
3010 		VI_UNLOCK(vp);
3011 		cache_purge(vp);
3012 		vdrop(vp);
3013 	}
3014 }
3015 
3016 /*
3017  * Perform canonical checks and cache lookup and pass on to filesystem
3018  * through the vop_cachedlookup only if needed.
3019  */
3020 
3021 int
3022 vfs_cache_lookup(struct vop_lookup_args *ap)
3023 {
3024 	struct vnode *dvp;
3025 	int error;
3026 	struct vnode **vpp = ap->a_vpp;
3027 	struct componentname *cnp = ap->a_cnp;
3028 	int flags = cnp->cn_flags;
3029 
3030 	*vpp = NULL;
3031 	dvp = ap->a_dvp;
3032 
3033 	if (dvp->v_type != VDIR)
3034 		return (ENOTDIR);
3035 
3036 	if ((flags & ISLASTCN) && (dvp->v_mount->mnt_flag & MNT_RDONLY) &&
3037 	    (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME))
3038 		return (EROFS);
3039 
3040 	error = vn_dir_check_exec(dvp, cnp);
3041 	if (error != 0)
3042 		return (error);
3043 
3044 	error = cache_lookup(dvp, vpp, cnp, NULL, NULL);
3045 	if (error == 0)
3046 		return (VOP_CACHEDLOOKUP(dvp, vpp, cnp));
3047 	if (error == -1)
3048 		return (0);
3049 	return (error);
3050 }
3051 
3052 /* Implementation of the getcwd syscall. */
3053 int
3054 sys___getcwd(struct thread *td, struct __getcwd_args *uap)
3055 {
3056 	char *buf, *retbuf;
3057 	size_t buflen;
3058 	int error;
3059 
3060 	buflen = uap->buflen;
3061 	if (__predict_false(buflen < 2))
3062 		return (EINVAL);
3063 	if (buflen > MAXPATHLEN)
3064 		buflen = MAXPATHLEN;
3065 
3066 	buf = uma_zalloc(namei_zone, M_WAITOK);
3067 	error = vn_getcwd(buf, &retbuf, &buflen);
3068 	if (error == 0)
3069 		error = copyout(retbuf, uap->buf, buflen);
3070 	uma_zfree(namei_zone, buf);
3071 	return (error);
3072 }
3073 
3074 int
3075 vn_getcwd(char *buf, char **retbuf, size_t *buflen)
3076 {
3077 	struct pwd *pwd;
3078 	int error;
3079 
3080 	vfs_smr_enter();
3081 	pwd = pwd_get_smr();
3082 	error = vn_fullpath_any_smr(pwd->pwd_cdir, pwd->pwd_rdir, buf, retbuf,
3083 	    buflen, 0);
3084 	VFS_SMR_ASSERT_NOT_ENTERED();
3085 	if (error < 0) {
3086 		pwd = pwd_hold(curthread);
3087 		error = vn_fullpath_any(pwd->pwd_cdir, pwd->pwd_rdir, buf,
3088 		    retbuf, buflen);
3089 		pwd_drop(pwd);
3090 	}
3091 
3092 #ifdef KTRACE
3093 	if (KTRPOINT(curthread, KTR_NAMEI) && error == 0)
3094 		ktrnamei(*retbuf);
3095 #endif
3096 	return (error);
3097 }
3098 
3099 static int
3100 kern___realpathat(struct thread *td, int fd, const char *path, char *buf,
3101     size_t size, int flags, enum uio_seg pathseg)
3102 {
3103 	struct nameidata nd;
3104 	char *retbuf, *freebuf;
3105 	int error;
3106 
3107 	if (flags != 0)
3108 		return (EINVAL);
3109 	NDINIT_ATRIGHTS(&nd, LOOKUP, FOLLOW | SAVENAME | WANTPARENT | AUDITVNODE1,
3110 	    pathseg, path, fd, &cap_fstat_rights, td);
3111 	if ((error = namei(&nd)) != 0)
3112 		return (error);
3113 	error = vn_fullpath_hardlink(&nd, &retbuf, &freebuf, &size);
3114 	if (error == 0) {
3115 		error = copyout(retbuf, buf, size);
3116 		free(freebuf, M_TEMP);
3117 	}
3118 	NDFREE(&nd, 0);
3119 	return (error);
3120 }
3121 
3122 int
3123 sys___realpathat(struct thread *td, struct __realpathat_args *uap)
3124 {
3125 
3126 	return (kern___realpathat(td, uap->fd, uap->path, uap->buf, uap->size,
3127 	    uap->flags, UIO_USERSPACE));
3128 }
3129 
3130 /*
3131  * Retrieve the full filesystem path that correspond to a vnode from the name
3132  * cache (if available)
3133  */
3134 int
3135 vn_fullpath(struct vnode *vp, char **retbuf, char **freebuf)
3136 {
3137 	struct pwd *pwd;
3138 	char *buf;
3139 	size_t buflen;
3140 	int error;
3141 
3142 	if (__predict_false(vp == NULL))
3143 		return (EINVAL);
3144 
3145 	buflen = MAXPATHLEN;
3146 	buf = malloc(buflen, M_TEMP, M_WAITOK);
3147 	vfs_smr_enter();
3148 	pwd = pwd_get_smr();
3149 	error = vn_fullpath_any_smr(vp, pwd->pwd_rdir, buf, retbuf, &buflen, 0);
3150 	VFS_SMR_ASSERT_NOT_ENTERED();
3151 	if (error < 0) {
3152 		pwd = pwd_hold(curthread);
3153 		error = vn_fullpath_any(vp, pwd->pwd_rdir, buf, retbuf, &buflen);
3154 		pwd_drop(pwd);
3155 	}
3156 	if (error == 0)
3157 		*freebuf = buf;
3158 	else
3159 		free(buf, M_TEMP);
3160 	return (error);
3161 }
3162 
3163 /*
3164  * This function is similar to vn_fullpath, but it attempts to lookup the
3165  * pathname relative to the global root mount point.  This is required for the
3166  * auditing sub-system, as audited pathnames must be absolute, relative to the
3167  * global root mount point.
3168  */
3169 int
3170 vn_fullpath_global(struct vnode *vp, char **retbuf, char **freebuf)
3171 {
3172 	char *buf;
3173 	size_t buflen;
3174 	int error;
3175 
3176 	if (__predict_false(vp == NULL))
3177 		return (EINVAL);
3178 	buflen = MAXPATHLEN;
3179 	buf = malloc(buflen, M_TEMP, M_WAITOK);
3180 	vfs_smr_enter();
3181 	error = vn_fullpath_any_smr(vp, rootvnode, buf, retbuf, &buflen, 0);
3182 	VFS_SMR_ASSERT_NOT_ENTERED();
3183 	if (error < 0) {
3184 		error = vn_fullpath_any(vp, rootvnode, buf, retbuf, &buflen);
3185 	}
3186 	if (error == 0)
3187 		*freebuf = buf;
3188 	else
3189 		free(buf, M_TEMP);
3190 	return (error);
3191 }
3192 
3193 static struct namecache *
3194 vn_dd_from_dst(struct vnode *vp)
3195 {
3196 	struct namecache *ncp;
3197 
3198 	cache_assert_vnode_locked(vp);
3199 	TAILQ_FOREACH(ncp, &vp->v_cache_dst, nc_dst) {
3200 		if ((ncp->nc_flag & NCF_ISDOTDOT) == 0)
3201 			return (ncp);
3202 	}
3203 	return (NULL);
3204 }
3205 
3206 int
3207 vn_vptocnp(struct vnode **vp, char *buf, size_t *buflen)
3208 {
3209 	struct vnode *dvp;
3210 	struct namecache *ncp;
3211 	struct mtx *vlp;
3212 	int error;
3213 
3214 	vlp = VP2VNODELOCK(*vp);
3215 	mtx_lock(vlp);
3216 	ncp = (*vp)->v_cache_dd;
3217 	if (ncp != NULL && (ncp->nc_flag & NCF_ISDOTDOT) == 0) {
3218 		KASSERT(ncp == vn_dd_from_dst(*vp),
3219 		    ("%s: mismatch for dd entry (%p != %p)", __func__,
3220 		    ncp, vn_dd_from_dst(*vp)));
3221 	} else {
3222 		ncp = vn_dd_from_dst(*vp);
3223 	}
3224 	if (ncp != NULL) {
3225 		if (*buflen < ncp->nc_nlen) {
3226 			mtx_unlock(vlp);
3227 			vrele(*vp);
3228 			counter_u64_add(numfullpathfail4, 1);
3229 			error = ENOMEM;
3230 			SDT_PROBE3(vfs, namecache, fullpath, return, error,
3231 			    vp, NULL);
3232 			return (error);
3233 		}
3234 		*buflen -= ncp->nc_nlen;
3235 		memcpy(buf + *buflen, ncp->nc_name, ncp->nc_nlen);
3236 		SDT_PROBE3(vfs, namecache, fullpath, hit, ncp->nc_dvp,
3237 		    ncp->nc_name, vp);
3238 		dvp = *vp;
3239 		*vp = ncp->nc_dvp;
3240 		vref(*vp);
3241 		mtx_unlock(vlp);
3242 		vrele(dvp);
3243 		return (0);
3244 	}
3245 	SDT_PROBE1(vfs, namecache, fullpath, miss, vp);
3246 
3247 	mtx_unlock(vlp);
3248 	vn_lock(*vp, LK_SHARED | LK_RETRY);
3249 	error = VOP_VPTOCNP(*vp, &dvp, buf, buflen);
3250 	vput(*vp);
3251 	if (error) {
3252 		counter_u64_add(numfullpathfail2, 1);
3253 		SDT_PROBE3(vfs, namecache, fullpath, return,  error, vp, NULL);
3254 		return (error);
3255 	}
3256 
3257 	*vp = dvp;
3258 	if (VN_IS_DOOMED(dvp)) {
3259 		/* forced unmount */
3260 		vrele(dvp);
3261 		error = ENOENT;
3262 		SDT_PROBE3(vfs, namecache, fullpath, return, error, vp, NULL);
3263 		return (error);
3264 	}
3265 	/*
3266 	 * *vp has its use count incremented still.
3267 	 */
3268 
3269 	return (0);
3270 }
3271 
3272 /*
3273  * Resolve a directory to a pathname.
3274  *
3275  * The name of the directory can always be found in the namecache or fetched
3276  * from the filesystem. There is also guaranteed to be only one parent, meaning
3277  * we can just follow vnodes up until we find the root.
3278  *
3279  * The vnode must be referenced.
3280  */
3281 static int
3282 vn_fullpath_dir(struct vnode *vp, struct vnode *rdir, char *buf, char **retbuf,
3283     size_t *len, size_t addend)
3284 {
3285 #ifdef KDTRACE_HOOKS
3286 	struct vnode *startvp = vp;
3287 #endif
3288 	struct vnode *vp1;
3289 	size_t buflen;
3290 	int error;
3291 	bool slash_prefixed;
3292 
3293 	VNPASS(vp->v_type == VDIR || VN_IS_DOOMED(vp), vp);
3294 	VNPASS(vp->v_usecount > 0, vp);
3295 
3296 	buflen = *len;
3297 
3298 	slash_prefixed = true;
3299 	if (addend == 0) {
3300 		MPASS(*len >= 2);
3301 		buflen--;
3302 		buf[buflen] = '\0';
3303 		slash_prefixed = false;
3304 	}
3305 
3306 	error = 0;
3307 
3308 	SDT_PROBE1(vfs, namecache, fullpath, entry, vp);
3309 	counter_u64_add(numfullpathcalls, 1);
3310 	while (vp != rdir && vp != rootvnode) {
3311 		/*
3312 		 * The vp vnode must be already fully constructed,
3313 		 * since it is either found in namecache or obtained
3314 		 * from VOP_VPTOCNP().  We may test for VV_ROOT safely
3315 		 * without obtaining the vnode lock.
3316 		 */
3317 		if ((vp->v_vflag & VV_ROOT) != 0) {
3318 			vn_lock(vp, LK_RETRY | LK_SHARED);
3319 
3320 			/*
3321 			 * With the vnode locked, check for races with
3322 			 * unmount, forced or not.  Note that we
3323 			 * already verified that vp is not equal to
3324 			 * the root vnode, which means that
3325 			 * mnt_vnodecovered can be NULL only for the
3326 			 * case of unmount.
3327 			 */
3328 			if (VN_IS_DOOMED(vp) ||
3329 			    (vp1 = vp->v_mount->mnt_vnodecovered) == NULL ||
3330 			    vp1->v_mountedhere != vp->v_mount) {
3331 				vput(vp);
3332 				error = ENOENT;
3333 				SDT_PROBE3(vfs, namecache, fullpath, return,
3334 				    error, vp, NULL);
3335 				break;
3336 			}
3337 
3338 			vref(vp1);
3339 			vput(vp);
3340 			vp = vp1;
3341 			continue;
3342 		}
3343 		if (vp->v_type != VDIR) {
3344 			vrele(vp);
3345 			counter_u64_add(numfullpathfail1, 1);
3346 			error = ENOTDIR;
3347 			SDT_PROBE3(vfs, namecache, fullpath, return,
3348 			    error, vp, NULL);
3349 			break;
3350 		}
3351 		error = vn_vptocnp(&vp, buf, &buflen);
3352 		if (error)
3353 			break;
3354 		if (buflen == 0) {
3355 			vrele(vp);
3356 			error = ENOMEM;
3357 			SDT_PROBE3(vfs, namecache, fullpath, return, error,
3358 			    startvp, NULL);
3359 			break;
3360 		}
3361 		buf[--buflen] = '/';
3362 		slash_prefixed = true;
3363 	}
3364 	if (error)
3365 		return (error);
3366 	if (!slash_prefixed) {
3367 		if (buflen == 0) {
3368 			vrele(vp);
3369 			counter_u64_add(numfullpathfail4, 1);
3370 			SDT_PROBE3(vfs, namecache, fullpath, return, ENOMEM,
3371 			    startvp, NULL);
3372 			return (ENOMEM);
3373 		}
3374 		buf[--buflen] = '/';
3375 	}
3376 	counter_u64_add(numfullpathfound, 1);
3377 	vrele(vp);
3378 
3379 	*retbuf = buf + buflen;
3380 	SDT_PROBE3(vfs, namecache, fullpath, return, 0, startvp, *retbuf);
3381 	*len -= buflen;
3382 	*len += addend;
3383 	return (0);
3384 }
3385 
3386 /*
3387  * Resolve an arbitrary vnode to a pathname.
3388  *
3389  * Note 2 caveats:
3390  * - hardlinks are not tracked, thus if the vnode is not a directory this can
3391  *   resolve to a different path than the one used to find it
3392  * - namecache is not mandatory, meaning names are not guaranteed to be added
3393  *   (in which case resolving fails)
3394  */
3395 static void __inline
3396 cache_rev_failed_impl(int *reason, int line)
3397 {
3398 
3399 	*reason = line;
3400 }
3401 #define cache_rev_failed(var)	cache_rev_failed_impl((var), __LINE__)
3402 
3403 static int
3404 vn_fullpath_any_smr(struct vnode *vp, struct vnode *rdir, char *buf,
3405     char **retbuf, size_t *buflen, size_t addend)
3406 {
3407 #ifdef KDTRACE_HOOKS
3408 	struct vnode *startvp = vp;
3409 #endif
3410 	struct vnode *tvp;
3411 	struct mount *mp;
3412 	struct namecache *ncp;
3413 	size_t orig_buflen;
3414 	int reason;
3415 	int error;
3416 #ifdef KDTRACE_HOOKS
3417 	int i;
3418 #endif
3419 	seqc_t vp_seqc, tvp_seqc;
3420 	u_char nc_flag;
3421 
3422 	VFS_SMR_ASSERT_ENTERED();
3423 
3424 	if (!cache_fast_revlookup) {
3425 		vfs_smr_exit();
3426 		return (-1);
3427 	}
3428 
3429 	orig_buflen = *buflen;
3430 
3431 	if (addend == 0) {
3432 		MPASS(*buflen >= 2);
3433 		*buflen -= 1;
3434 		buf[*buflen] = '\0';
3435 	}
3436 
3437 	if (vp == rdir || vp == rootvnode) {
3438 		if (addend == 0) {
3439 			*buflen -= 1;
3440 			buf[*buflen] = '/';
3441 		}
3442 		goto out_ok;
3443 	}
3444 
3445 #ifdef KDTRACE_HOOKS
3446 	i = 0;
3447 #endif
3448 	error = -1;
3449 	ncp = NULL; /* for sdt probe down below */
3450 	vp_seqc = vn_seqc_read_any(vp);
3451 	if (seqc_in_modify(vp_seqc)) {
3452 		cache_rev_failed(&reason);
3453 		goto out_abort;
3454 	}
3455 
3456 	for (;;) {
3457 #ifdef KDTRACE_HOOKS
3458 		i++;
3459 #endif
3460 		if ((vp->v_vflag & VV_ROOT) != 0) {
3461 			mp = atomic_load_ptr(&vp->v_mount);
3462 			if (mp == NULL) {
3463 				cache_rev_failed(&reason);
3464 				goto out_abort;
3465 			}
3466 			tvp = atomic_load_ptr(&mp->mnt_vnodecovered);
3467 			tvp_seqc = vn_seqc_read_any(tvp);
3468 			if (seqc_in_modify(tvp_seqc)) {
3469 				cache_rev_failed(&reason);
3470 				goto out_abort;
3471 			}
3472 			if (!vn_seqc_consistent(vp, vp_seqc)) {
3473 				cache_rev_failed(&reason);
3474 				goto out_abort;
3475 			}
3476 			vp = tvp;
3477 			vp_seqc = tvp_seqc;
3478 			continue;
3479 		}
3480 		ncp = atomic_load_consume_ptr(&vp->v_cache_dd);
3481 		if (ncp == NULL) {
3482 			cache_rev_failed(&reason);
3483 			goto out_abort;
3484 		}
3485 		nc_flag = atomic_load_char(&ncp->nc_flag);
3486 		if ((nc_flag & NCF_ISDOTDOT) != 0) {
3487 			cache_rev_failed(&reason);
3488 			goto out_abort;
3489 		}
3490 		if (ncp->nc_nlen >= *buflen) {
3491 			cache_rev_failed(&reason);
3492 			error = ENOMEM;
3493 			goto out_abort;
3494 		}
3495 		*buflen -= ncp->nc_nlen;
3496 		memcpy(buf + *buflen, ncp->nc_name, ncp->nc_nlen);
3497 		*buflen -= 1;
3498 		buf[*buflen] = '/';
3499 		tvp = ncp->nc_dvp;
3500 		tvp_seqc = vn_seqc_read_any(tvp);
3501 		if (seqc_in_modify(tvp_seqc)) {
3502 			cache_rev_failed(&reason);
3503 			goto out_abort;
3504 		}
3505 		if (!vn_seqc_consistent(vp, vp_seqc)) {
3506 			cache_rev_failed(&reason);
3507 			goto out_abort;
3508 		}
3509 		/*
3510 		 * Acquire fence provided by vn_seqc_read_any above.
3511 		 */
3512 		if (__predict_false(atomic_load_ptr(&vp->v_cache_dd) != ncp)) {
3513 			cache_rev_failed(&reason);
3514 			goto out_abort;
3515 		}
3516 		if (!cache_ncp_canuse(ncp)) {
3517 			cache_rev_failed(&reason);
3518 			goto out_abort;
3519 		}
3520 		vp = tvp;
3521 		vp_seqc = tvp_seqc;
3522 		if (vp == rdir || vp == rootvnode)
3523 			break;
3524 	}
3525 out_ok:
3526 	vfs_smr_exit();
3527 	*retbuf = buf + *buflen;
3528 	*buflen = orig_buflen - *buflen + addend;
3529 	SDT_PROBE2(vfs, namecache, fullpath_smr, hit, startvp, *retbuf);
3530 	return (0);
3531 
3532 out_abort:
3533 	*buflen = orig_buflen;
3534 	SDT_PROBE4(vfs, namecache, fullpath_smr, miss, startvp, ncp, reason, i);
3535 	vfs_smr_exit();
3536 	return (error);
3537 }
3538 
3539 static int
3540 vn_fullpath_any(struct vnode *vp, struct vnode *rdir, char *buf, char **retbuf,
3541     size_t *buflen)
3542 {
3543 	size_t orig_buflen, addend;
3544 	int error;
3545 
3546 	if (*buflen < 2)
3547 		return (EINVAL);
3548 
3549 	orig_buflen = *buflen;
3550 
3551 	vref(vp);
3552 	addend = 0;
3553 	if (vp->v_type != VDIR) {
3554 		*buflen -= 1;
3555 		buf[*buflen] = '\0';
3556 		error = vn_vptocnp(&vp, buf, buflen);
3557 		if (error)
3558 			return (error);
3559 		if (*buflen == 0) {
3560 			vrele(vp);
3561 			return (ENOMEM);
3562 		}
3563 		*buflen -= 1;
3564 		buf[*buflen] = '/';
3565 		addend = orig_buflen - *buflen;
3566 	}
3567 
3568 	return (vn_fullpath_dir(vp, rdir, buf, retbuf, buflen, addend));
3569 }
3570 
3571 /*
3572  * Resolve an arbitrary vnode to a pathname (taking care of hardlinks).
3573  *
3574  * Since the namecache does not track hardlinks, the caller is expected to first
3575  * look up the target vnode with SAVENAME | WANTPARENT flags passed to namei.
3576  *
3577  * Then we have 2 cases:
3578  * - if the found vnode is a directory, the path can be constructed just by
3579  *   following names up the chain
3580  * - otherwise we populate the buffer with the saved name and start resolving
3581  *   from the parent
3582  */
3583 static int
3584 vn_fullpath_hardlink(struct nameidata *ndp, char **retbuf, char **freebuf,
3585     size_t *buflen)
3586 {
3587 	char *buf, *tmpbuf;
3588 	struct pwd *pwd;
3589 	struct componentname *cnp;
3590 	struct vnode *vp;
3591 	size_t addend;
3592 	int error;
3593 	enum vtype type;
3594 
3595 	if (*buflen < 2)
3596 		return (EINVAL);
3597 	if (*buflen > MAXPATHLEN)
3598 		*buflen = MAXPATHLEN;
3599 
3600 	buf = malloc(*buflen, M_TEMP, M_WAITOK);
3601 
3602 	addend = 0;
3603 	vp = ndp->ni_vp;
3604 	/*
3605 	 * Check for VBAD to work around the vp_crossmp bug in lookup().
3606 	 *
3607 	 * For example consider tmpfs on /tmp and realpath /tmp. ni_vp will be
3608 	 * set to mount point's root vnode while ni_dvp will be vp_crossmp.
3609 	 * If the type is VDIR (like in this very case) we can skip looking
3610 	 * at ni_dvp in the first place. However, since vnodes get passed here
3611 	 * unlocked the target may transition to doomed state (type == VBAD)
3612 	 * before we get to evaluate the condition. If this happens, we will
3613 	 * populate part of the buffer and descend to vn_fullpath_dir with
3614 	 * vp == vp_crossmp. Prevent the problem by checking for VBAD.
3615 	 *
3616 	 * This should be atomic_load(&vp->v_type) but it is illegal to take
3617 	 * an address of a bit field, even if said field is sized to char.
3618 	 * Work around the problem by reading the value into a full-sized enum
3619 	 * and then re-reading it with atomic_load which will still prevent
3620 	 * the compiler from re-reading down the road.
3621 	 */
3622 	type = vp->v_type;
3623 	type = atomic_load_int(&type);
3624 	if (type == VBAD) {
3625 		error = ENOENT;
3626 		goto out_bad;
3627 	}
3628 	if (type != VDIR) {
3629 		cnp = &ndp->ni_cnd;
3630 		addend = cnp->cn_namelen + 2;
3631 		if (*buflen < addend) {
3632 			error = ENOMEM;
3633 			goto out_bad;
3634 		}
3635 		*buflen -= addend;
3636 		tmpbuf = buf + *buflen;
3637 		tmpbuf[0] = '/';
3638 		memcpy(&tmpbuf[1], cnp->cn_nameptr, cnp->cn_namelen);
3639 		tmpbuf[addend - 1] = '\0';
3640 		vp = ndp->ni_dvp;
3641 	}
3642 
3643 	vfs_smr_enter();
3644 	pwd = pwd_get_smr();
3645 	error = vn_fullpath_any_smr(vp, pwd->pwd_rdir, buf, retbuf, buflen,
3646 	    addend);
3647 	VFS_SMR_ASSERT_NOT_ENTERED();
3648 	if (error < 0) {
3649 		pwd = pwd_hold(curthread);
3650 		vref(vp);
3651 		error = vn_fullpath_dir(vp, pwd->pwd_rdir, buf, retbuf, buflen,
3652 		    addend);
3653 		pwd_drop(pwd);
3654 		if (error != 0)
3655 			goto out_bad;
3656 	}
3657 
3658 	*freebuf = buf;
3659 
3660 	return (0);
3661 out_bad:
3662 	free(buf, M_TEMP);
3663 	return (error);
3664 }
3665 
3666 struct vnode *
3667 vn_dir_dd_ino(struct vnode *vp)
3668 {
3669 	struct namecache *ncp;
3670 	struct vnode *ddvp;
3671 	struct mtx *vlp;
3672 	enum vgetstate vs;
3673 
3674 	ASSERT_VOP_LOCKED(vp, "vn_dir_dd_ino");
3675 	vlp = VP2VNODELOCK(vp);
3676 	mtx_lock(vlp);
3677 	TAILQ_FOREACH(ncp, &(vp->v_cache_dst), nc_dst) {
3678 		if ((ncp->nc_flag & NCF_ISDOTDOT) != 0)
3679 			continue;
3680 		ddvp = ncp->nc_dvp;
3681 		vs = vget_prep(ddvp);
3682 		mtx_unlock(vlp);
3683 		if (vget_finish(ddvp, LK_SHARED | LK_NOWAIT, vs))
3684 			return (NULL);
3685 		return (ddvp);
3686 	}
3687 	mtx_unlock(vlp);
3688 	return (NULL);
3689 }
3690 
3691 int
3692 vn_commname(struct vnode *vp, char *buf, u_int buflen)
3693 {
3694 	struct namecache *ncp;
3695 	struct mtx *vlp;
3696 	int l;
3697 
3698 	vlp = VP2VNODELOCK(vp);
3699 	mtx_lock(vlp);
3700 	TAILQ_FOREACH(ncp, &vp->v_cache_dst, nc_dst)
3701 		if ((ncp->nc_flag & NCF_ISDOTDOT) == 0)
3702 			break;
3703 	if (ncp == NULL) {
3704 		mtx_unlock(vlp);
3705 		return (ENOENT);
3706 	}
3707 	l = min(ncp->nc_nlen, buflen - 1);
3708 	memcpy(buf, ncp->nc_name, l);
3709 	mtx_unlock(vlp);
3710 	buf[l] = '\0';
3711 	return (0);
3712 }
3713 
3714 /*
3715  * This function updates path string to vnode's full global path
3716  * and checks the size of the new path string against the pathlen argument.
3717  *
3718  * Requires a locked, referenced vnode.
3719  * Vnode is re-locked on success or ENODEV, otherwise unlocked.
3720  *
3721  * If vp is a directory, the call to vn_fullpath_global() always succeeds
3722  * because it falls back to the ".." lookup if the namecache lookup fails.
3723  */
3724 int
3725 vn_path_to_global_path(struct thread *td, struct vnode *vp, char *path,
3726     u_int pathlen)
3727 {
3728 	struct nameidata nd;
3729 	struct vnode *vp1;
3730 	char *rpath, *fbuf;
3731 	int error;
3732 
3733 	ASSERT_VOP_ELOCKED(vp, __func__);
3734 
3735 	/* Construct global filesystem path from vp. */
3736 	VOP_UNLOCK(vp);
3737 	error = vn_fullpath_global(vp, &rpath, &fbuf);
3738 
3739 	if (error != 0) {
3740 		vrele(vp);
3741 		return (error);
3742 	}
3743 
3744 	if (strlen(rpath) >= pathlen) {
3745 		vrele(vp);
3746 		error = ENAMETOOLONG;
3747 		goto out;
3748 	}
3749 
3750 	/*
3751 	 * Re-lookup the vnode by path to detect a possible rename.
3752 	 * As a side effect, the vnode is relocked.
3753 	 * If vnode was renamed, return ENOENT.
3754 	 */
3755 	NDINIT(&nd, LOOKUP, FOLLOW | LOCKLEAF | AUDITVNODE1,
3756 	    UIO_SYSSPACE, path, td);
3757 	error = namei(&nd);
3758 	if (error != 0) {
3759 		vrele(vp);
3760 		goto out;
3761 	}
3762 	NDFREE(&nd, NDF_ONLY_PNBUF);
3763 	vp1 = nd.ni_vp;
3764 	vrele(vp);
3765 	if (vp1 == vp)
3766 		strcpy(path, rpath);
3767 	else {
3768 		vput(vp1);
3769 		error = ENOENT;
3770 	}
3771 
3772 out:
3773 	free(fbuf, M_TEMP);
3774 	return (error);
3775 }
3776 
3777 #ifdef DDB
3778 static void
3779 db_print_vpath(struct vnode *vp)
3780 {
3781 
3782 	while (vp != NULL) {
3783 		db_printf("%p: ", vp);
3784 		if (vp == rootvnode) {
3785 			db_printf("/");
3786 			vp = NULL;
3787 		} else {
3788 			if (vp->v_vflag & VV_ROOT) {
3789 				db_printf("<mount point>");
3790 				vp = vp->v_mount->mnt_vnodecovered;
3791 			} else {
3792 				struct namecache *ncp;
3793 				char *ncn;
3794 				int i;
3795 
3796 				ncp = TAILQ_FIRST(&vp->v_cache_dst);
3797 				if (ncp != NULL) {
3798 					ncn = ncp->nc_name;
3799 					for (i = 0; i < ncp->nc_nlen; i++)
3800 						db_printf("%c", *ncn++);
3801 					vp = ncp->nc_dvp;
3802 				} else {
3803 					vp = NULL;
3804 				}
3805 			}
3806 		}
3807 		db_printf("\n");
3808 	}
3809 
3810 	return;
3811 }
3812 
3813 DB_SHOW_COMMAND(vpath, db_show_vpath)
3814 {
3815 	struct vnode *vp;
3816 
3817 	if (!have_addr) {
3818 		db_printf("usage: show vpath <struct vnode *>\n");
3819 		return;
3820 	}
3821 
3822 	vp = (struct vnode *)addr;
3823 	db_print_vpath(vp);
3824 }
3825 
3826 #endif
3827 
3828 static int cache_fast_lookup = 1;
3829 static char __read_frequently cache_fast_lookup_enabled = true;
3830 
3831 #define CACHE_FPL_FAILED	-2020
3832 
3833 void
3834 cache_fast_lookup_enabled_recalc(void)
3835 {
3836 	int lookup_flag;
3837 	int mac_on;
3838 
3839 #ifdef MAC
3840 	mac_on = mac_vnode_check_lookup_enabled();
3841 	mac_on |= mac_vnode_check_readlink_enabled();
3842 #else
3843 	mac_on = 0;
3844 #endif
3845 
3846 	lookup_flag = atomic_load_int(&cache_fast_lookup);
3847 	if (lookup_flag && !mac_on) {
3848 		atomic_store_char(&cache_fast_lookup_enabled, true);
3849 	} else {
3850 		atomic_store_char(&cache_fast_lookup_enabled, false);
3851 	}
3852 }
3853 
3854 static int
3855 syscal_vfs_cache_fast_lookup(SYSCTL_HANDLER_ARGS)
3856 {
3857 	int error, old;
3858 
3859 	old = atomic_load_int(&cache_fast_lookup);
3860 	error = sysctl_handle_int(oidp, arg1, arg2, req);
3861 	if (error == 0 && req->newptr && old != atomic_load_int(&cache_fast_lookup))
3862 		cache_fast_lookup_enabled_recalc();
3863 	return (error);
3864 }
3865 SYSCTL_PROC(_vfs, OID_AUTO, cache_fast_lookup, CTLTYPE_INT|CTLFLAG_RW|CTLFLAG_MPSAFE,
3866     &cache_fast_lookup, 0, syscal_vfs_cache_fast_lookup, "IU", "");
3867 
3868 /*
3869  * Disable lockless lookup and observe all CPUs not executing it.
3870  *
3871  * Used when resizing the hash table.
3872  *
3873  * TODO: no provisions are made to handle tweaking of the knob at the same time
3874  */
3875 static void
3876 cache_fplookup_lockout(void)
3877 {
3878 	bool on;
3879 
3880 	on = atomic_load_char(&cache_fast_lookup_enabled);
3881 	if (on) {
3882 		atomic_store_char(&cache_fast_lookup_enabled, false);
3883 		atomic_thread_fence_rel();
3884 		vfs_smr_synchronize();
3885 	}
3886 }
3887 
3888 static void
3889 cache_fplookup_restore(void)
3890 {
3891 
3892 	cache_fast_lookup_enabled_recalc();
3893 }
3894 
3895 /*
3896  * Components of nameidata (or objects it can point to) which may
3897  * need restoring in case fast path lookup fails.
3898  */
3899 struct nameidata_outer {
3900 	size_t ni_pathlen;
3901 	int cn_flags;
3902 };
3903 
3904 struct nameidata_saved {
3905 #ifdef INVARIANTS
3906 	char *cn_nameptr;
3907 	size_t ni_pathlen;
3908 #endif
3909 };
3910 
3911 #ifdef INVARIANTS
3912 struct cache_fpl_debug {
3913 	size_t ni_pathlen;
3914 };
3915 #endif
3916 
3917 struct cache_fpl {
3918 	struct nameidata *ndp;
3919 	struct componentname *cnp;
3920 	char *nulchar;
3921 	struct vnode *dvp;
3922 	struct vnode *tvp;
3923 	seqc_t dvp_seqc;
3924 	seqc_t tvp_seqc;
3925 	uint32_t hash;
3926 	struct nameidata_saved snd;
3927 	struct nameidata_outer snd_outer;
3928 	int line;
3929 	enum cache_fpl_status status:8;
3930 	bool in_smr;
3931 	bool fsearch;
3932 	bool savename;
3933 	struct pwd **pwd;
3934 #ifdef INVARIANTS
3935 	struct cache_fpl_debug debug;
3936 #endif
3937 };
3938 
3939 static bool cache_fplookup_is_mp(struct cache_fpl *fpl);
3940 static int cache_fplookup_cross_mount(struct cache_fpl *fpl);
3941 static int cache_fplookup_partial_setup(struct cache_fpl *fpl);
3942 static int cache_fplookup_skip_slashes(struct cache_fpl *fpl);
3943 static int cache_fplookup_trailingslash(struct cache_fpl *fpl);
3944 static void cache_fpl_pathlen_dec(struct cache_fpl *fpl);
3945 static void cache_fpl_pathlen_inc(struct cache_fpl *fpl);
3946 static void cache_fpl_pathlen_add(struct cache_fpl *fpl, size_t n);
3947 static void cache_fpl_pathlen_sub(struct cache_fpl *fpl, size_t n);
3948 
3949 static void
3950 cache_fpl_cleanup_cnp(struct componentname *cnp)
3951 {
3952 
3953 	uma_zfree(namei_zone, cnp->cn_pnbuf);
3954 #ifdef DIAGNOSTIC
3955 	cnp->cn_pnbuf = NULL;
3956 	cnp->cn_nameptr = NULL;
3957 #endif
3958 }
3959 
3960 static struct vnode *
3961 cache_fpl_handle_root(struct cache_fpl *fpl)
3962 {
3963 	struct nameidata *ndp;
3964 	struct componentname *cnp;
3965 
3966 	ndp = fpl->ndp;
3967 	cnp = fpl->cnp;
3968 
3969 	MPASS(*(cnp->cn_nameptr) == '/');
3970 	cnp->cn_nameptr++;
3971 	cache_fpl_pathlen_dec(fpl);
3972 
3973 	if (__predict_false(*(cnp->cn_nameptr) == '/')) {
3974 		do {
3975 			cnp->cn_nameptr++;
3976 			cache_fpl_pathlen_dec(fpl);
3977 		} while (*(cnp->cn_nameptr) == '/');
3978 	}
3979 
3980 	return (ndp->ni_rootdir);
3981 }
3982 
3983 static void
3984 cache_fpl_checkpoint_outer(struct cache_fpl *fpl)
3985 {
3986 
3987 	fpl->snd_outer.ni_pathlen = fpl->ndp->ni_pathlen;
3988 	fpl->snd_outer.cn_flags = fpl->ndp->ni_cnd.cn_flags;
3989 }
3990 
3991 static void
3992 cache_fpl_checkpoint(struct cache_fpl *fpl)
3993 {
3994 
3995 #ifdef INVARIANTS
3996 	fpl->snd.cn_nameptr = fpl->ndp->ni_cnd.cn_nameptr;
3997 	fpl->snd.ni_pathlen = fpl->debug.ni_pathlen;
3998 #endif
3999 }
4000 
4001 static void
4002 cache_fpl_restore_partial(struct cache_fpl *fpl)
4003 {
4004 
4005 	fpl->ndp->ni_cnd.cn_flags = fpl->snd_outer.cn_flags;
4006 #ifdef INVARIANTS
4007 	fpl->debug.ni_pathlen = fpl->snd.ni_pathlen;
4008 #endif
4009 }
4010 
4011 static void
4012 cache_fpl_restore_abort(struct cache_fpl *fpl)
4013 {
4014 
4015 	cache_fpl_restore_partial(fpl);
4016 	/*
4017 	 * It is 0 on entry by API contract.
4018 	 */
4019 	fpl->ndp->ni_resflags = 0;
4020 	fpl->ndp->ni_cnd.cn_nameptr = fpl->ndp->ni_cnd.cn_pnbuf;
4021 	fpl->ndp->ni_pathlen = fpl->snd_outer.ni_pathlen;
4022 }
4023 
4024 #ifdef INVARIANTS
4025 #define cache_fpl_smr_assert_entered(fpl) ({			\
4026 	struct cache_fpl *_fpl = (fpl);				\
4027 	MPASS(_fpl->in_smr == true);				\
4028 	VFS_SMR_ASSERT_ENTERED();				\
4029 })
4030 #define cache_fpl_smr_assert_not_entered(fpl) ({		\
4031 	struct cache_fpl *_fpl = (fpl);				\
4032 	MPASS(_fpl->in_smr == false);				\
4033 	VFS_SMR_ASSERT_NOT_ENTERED();				\
4034 })
4035 static void
4036 cache_fpl_assert_status(struct cache_fpl *fpl)
4037 {
4038 
4039 	switch (fpl->status) {
4040 	case CACHE_FPL_STATUS_UNSET:
4041 		__assert_unreachable();
4042 		break;
4043 	case CACHE_FPL_STATUS_DESTROYED:
4044 	case CACHE_FPL_STATUS_ABORTED:
4045 	case CACHE_FPL_STATUS_PARTIAL:
4046 	case CACHE_FPL_STATUS_HANDLED:
4047 		break;
4048 	}
4049 }
4050 #else
4051 #define cache_fpl_smr_assert_entered(fpl) do { } while (0)
4052 #define cache_fpl_smr_assert_not_entered(fpl) do { } while (0)
4053 #define cache_fpl_assert_status(fpl) do { } while (0)
4054 #endif
4055 
4056 #define cache_fpl_smr_enter_initial(fpl) ({			\
4057 	struct cache_fpl *_fpl = (fpl);				\
4058 	vfs_smr_enter();					\
4059 	_fpl->in_smr = true;					\
4060 })
4061 
4062 #define cache_fpl_smr_enter(fpl) ({				\
4063 	struct cache_fpl *_fpl = (fpl);				\
4064 	MPASS(_fpl->in_smr == false);				\
4065 	vfs_smr_enter();					\
4066 	_fpl->in_smr = true;					\
4067 })
4068 
4069 #define cache_fpl_smr_exit(fpl) ({				\
4070 	struct cache_fpl *_fpl = (fpl);				\
4071 	MPASS(_fpl->in_smr == true);				\
4072 	vfs_smr_exit();						\
4073 	_fpl->in_smr = false;					\
4074 })
4075 
4076 static int
4077 cache_fpl_aborted_early_impl(struct cache_fpl *fpl, int line)
4078 {
4079 
4080 	if (fpl->status != CACHE_FPL_STATUS_UNSET) {
4081 		KASSERT(fpl->status == CACHE_FPL_STATUS_PARTIAL,
4082 		    ("%s: converting to abort from %d at %d, set at %d\n",
4083 		    __func__, fpl->status, line, fpl->line));
4084 	}
4085 	cache_fpl_smr_assert_not_entered(fpl);
4086 	fpl->status = CACHE_FPL_STATUS_ABORTED;
4087 	fpl->line = line;
4088 	return (CACHE_FPL_FAILED);
4089 }
4090 
4091 #define cache_fpl_aborted_early(x)	cache_fpl_aborted_early_impl((x), __LINE__)
4092 
4093 static int __noinline
4094 cache_fpl_aborted_impl(struct cache_fpl *fpl, int line)
4095 {
4096 	struct nameidata *ndp;
4097 	struct componentname *cnp;
4098 
4099 	ndp = fpl->ndp;
4100 	cnp = fpl->cnp;
4101 
4102 	if (fpl->status != CACHE_FPL_STATUS_UNSET) {
4103 		KASSERT(fpl->status == CACHE_FPL_STATUS_PARTIAL,
4104 		    ("%s: converting to abort from %d at %d, set at %d\n",
4105 		    __func__, fpl->status, line, fpl->line));
4106 	}
4107 	fpl->status = CACHE_FPL_STATUS_ABORTED;
4108 	fpl->line = line;
4109 	if (fpl->in_smr)
4110 		cache_fpl_smr_exit(fpl);
4111 	cache_fpl_restore_abort(fpl);
4112 	/*
4113 	 * Resolving symlinks overwrites data passed by the caller.
4114 	 * Let namei know.
4115 	 */
4116 	if (ndp->ni_loopcnt > 0) {
4117 		fpl->status = CACHE_FPL_STATUS_DESTROYED;
4118 		cache_fpl_cleanup_cnp(cnp);
4119 	}
4120 	return (CACHE_FPL_FAILED);
4121 }
4122 
4123 #define cache_fpl_aborted(x)	cache_fpl_aborted_impl((x), __LINE__)
4124 
4125 static int __noinline
4126 cache_fpl_partial_impl(struct cache_fpl *fpl, int line)
4127 {
4128 
4129 	KASSERT(fpl->status == CACHE_FPL_STATUS_UNSET,
4130 	    ("%s: setting to partial at %d, but already set to %d at %d\n",
4131 	    __func__, line, fpl->status, fpl->line));
4132 	cache_fpl_smr_assert_entered(fpl);
4133 	fpl->status = CACHE_FPL_STATUS_PARTIAL;
4134 	fpl->line = line;
4135 	return (cache_fplookup_partial_setup(fpl));
4136 }
4137 
4138 #define cache_fpl_partial(x)	cache_fpl_partial_impl((x), __LINE__)
4139 
4140 static int
4141 cache_fpl_handled_impl(struct cache_fpl *fpl, int line)
4142 {
4143 
4144 	KASSERT(fpl->status == CACHE_FPL_STATUS_UNSET,
4145 	    ("%s: setting to handled at %d, but already set to %d at %d\n",
4146 	    __func__, line, fpl->status, fpl->line));
4147 	cache_fpl_smr_assert_not_entered(fpl);
4148 	fpl->status = CACHE_FPL_STATUS_HANDLED;
4149 	fpl->line = line;
4150 	return (0);
4151 }
4152 
4153 #define cache_fpl_handled(x)	cache_fpl_handled_impl((x), __LINE__)
4154 
4155 static int
4156 cache_fpl_handled_error_impl(struct cache_fpl *fpl, int error, int line)
4157 {
4158 
4159 	KASSERT(fpl->status == CACHE_FPL_STATUS_UNSET,
4160 	    ("%s: setting to handled at %d, but already set to %d at %d\n",
4161 	    __func__, line, fpl->status, fpl->line));
4162 	MPASS(error != 0);
4163 	MPASS(error != CACHE_FPL_FAILED);
4164 	cache_fpl_smr_assert_not_entered(fpl);
4165 	fpl->status = CACHE_FPL_STATUS_HANDLED;
4166 	fpl->line = line;
4167 	fpl->dvp = NULL;
4168 	fpl->tvp = NULL;
4169 	fpl->savename = false;
4170 	return (error);
4171 }
4172 
4173 #define cache_fpl_handled_error(x, e)	cache_fpl_handled_error_impl((x), (e), __LINE__)
4174 
4175 static bool
4176 cache_fpl_terminated(struct cache_fpl *fpl)
4177 {
4178 
4179 	return (fpl->status != CACHE_FPL_STATUS_UNSET);
4180 }
4181 
4182 #define CACHE_FPL_SUPPORTED_CN_FLAGS \
4183 	(NC_NOMAKEENTRY | NC_KEEPPOSENTRY | LOCKLEAF | LOCKPARENT | WANTPARENT | \
4184 	 FAILIFEXISTS | FOLLOW | LOCKSHARED | SAVENAME | SAVESTART | WILLBEDIR | \
4185 	 ISOPEN | NOMACCHECK | AUDITVNODE1 | AUDITVNODE2 | NOCAPCHECK)
4186 
4187 #define CACHE_FPL_INTERNAL_CN_FLAGS \
4188 	(ISDOTDOT | MAKEENTRY | ISLASTCN)
4189 
4190 _Static_assert((CACHE_FPL_SUPPORTED_CN_FLAGS & CACHE_FPL_INTERNAL_CN_FLAGS) == 0,
4191     "supported and internal flags overlap");
4192 
4193 static bool
4194 cache_fpl_islastcn(struct nameidata *ndp)
4195 {
4196 
4197 	return (*ndp->ni_next == 0);
4198 }
4199 
4200 static bool
4201 cache_fpl_istrailingslash(struct cache_fpl *fpl)
4202 {
4203 
4204 	return (*(fpl->nulchar - 1) == '/');
4205 }
4206 
4207 static bool
4208 cache_fpl_isdotdot(struct componentname *cnp)
4209 {
4210 
4211 	if (cnp->cn_namelen == 2 &&
4212 	    cnp->cn_nameptr[1] == '.' && cnp->cn_nameptr[0] == '.')
4213 		return (true);
4214 	return (false);
4215 }
4216 
4217 static bool
4218 cache_can_fplookup(struct cache_fpl *fpl)
4219 {
4220 	struct nameidata *ndp;
4221 	struct componentname *cnp;
4222 	struct thread *td;
4223 
4224 	ndp = fpl->ndp;
4225 	cnp = fpl->cnp;
4226 	td = cnp->cn_thread;
4227 
4228 	if (!atomic_load_char(&cache_fast_lookup_enabled)) {
4229 		cache_fpl_aborted_early(fpl);
4230 		return (false);
4231 	}
4232 	if ((cnp->cn_flags & ~CACHE_FPL_SUPPORTED_CN_FLAGS) != 0) {
4233 		cache_fpl_aborted_early(fpl);
4234 		return (false);
4235 	}
4236 	if (IN_CAPABILITY_MODE(td)) {
4237 		cache_fpl_aborted_early(fpl);
4238 		return (false);
4239 	}
4240 	if (AUDITING_TD(td)) {
4241 		cache_fpl_aborted_early(fpl);
4242 		return (false);
4243 	}
4244 	if (ndp->ni_startdir != NULL) {
4245 		cache_fpl_aborted_early(fpl);
4246 		return (false);
4247 	}
4248 	return (true);
4249 }
4250 
4251 static int
4252 cache_fplookup_dirfd(struct cache_fpl *fpl, struct vnode **vpp)
4253 {
4254 	struct nameidata *ndp;
4255 	int error;
4256 	bool fsearch;
4257 
4258 	ndp = fpl->ndp;
4259 	error = fgetvp_lookup_smr(ndp->ni_dirfd, ndp, vpp, &fsearch);
4260 	if (__predict_false(error != 0)) {
4261 		return (cache_fpl_aborted(fpl));
4262 	}
4263 	fpl->fsearch = fsearch;
4264 	return (0);
4265 }
4266 
4267 static int __noinline
4268 cache_fplookup_negative_promote(struct cache_fpl *fpl, struct namecache *oncp,
4269     uint32_t hash)
4270 {
4271 	struct componentname *cnp;
4272 	struct vnode *dvp;
4273 
4274 	cnp = fpl->cnp;
4275 	dvp = fpl->dvp;
4276 
4277 	cache_fpl_smr_exit(fpl);
4278 	if (cache_neg_promote_cond(dvp, cnp, oncp, hash))
4279 		return (cache_fpl_handled_error(fpl, ENOENT));
4280 	else
4281 		return (cache_fpl_aborted(fpl));
4282 }
4283 
4284 /*
4285  * The target vnode is not supported, prepare for the slow path to take over.
4286  */
4287 static int __noinline
4288 cache_fplookup_partial_setup(struct cache_fpl *fpl)
4289 {
4290 	struct nameidata *ndp;
4291 	struct componentname *cnp;
4292 	enum vgetstate dvs;
4293 	struct vnode *dvp;
4294 	struct pwd *pwd;
4295 	seqc_t dvp_seqc;
4296 
4297 	ndp = fpl->ndp;
4298 	cnp = fpl->cnp;
4299 	pwd = *(fpl->pwd);
4300 	dvp = fpl->dvp;
4301 	dvp_seqc = fpl->dvp_seqc;
4302 
4303 	if (!pwd_hold_smr(pwd)) {
4304 		return (cache_fpl_aborted(fpl));
4305 	}
4306 
4307 	/*
4308 	 * Note that seqc is checked before the vnode is locked, so by
4309 	 * the time regular lookup gets to it it may have moved.
4310 	 *
4311 	 * Ultimately this does not affect correctness, any lookup errors
4312 	 * are userspace racing with itself. It is guaranteed that any
4313 	 * path which ultimately gets found could also have been found
4314 	 * by regular lookup going all the way in absence of concurrent
4315 	 * modifications.
4316 	 */
4317 	dvs = vget_prep_smr(dvp);
4318 	cache_fpl_smr_exit(fpl);
4319 	if (__predict_false(dvs == VGET_NONE)) {
4320 		pwd_drop(pwd);
4321 		return (cache_fpl_aborted(fpl));
4322 	}
4323 
4324 	vget_finish_ref(dvp, dvs);
4325 	if (!vn_seqc_consistent(dvp, dvp_seqc)) {
4326 		vrele(dvp);
4327 		pwd_drop(pwd);
4328 		return (cache_fpl_aborted(fpl));
4329 	}
4330 
4331 	cache_fpl_restore_partial(fpl);
4332 #ifdef INVARIANTS
4333 	if (cnp->cn_nameptr != fpl->snd.cn_nameptr) {
4334 		panic("%s: cn_nameptr mismatch (%p != %p) full [%s]\n", __func__,
4335 		    cnp->cn_nameptr, fpl->snd.cn_nameptr, cnp->cn_pnbuf);
4336 	}
4337 #endif
4338 
4339 	ndp->ni_startdir = dvp;
4340 	cnp->cn_flags |= MAKEENTRY;
4341 	if (cache_fpl_islastcn(ndp))
4342 		cnp->cn_flags |= ISLASTCN;
4343 	if (cache_fpl_isdotdot(cnp))
4344 		cnp->cn_flags |= ISDOTDOT;
4345 
4346 	/*
4347 	 * Skip potential extra slashes parsing did not take care of.
4348 	 * cache_fplookup_skip_slashes explains the mechanism.
4349 	 */
4350 	if (__predict_false(*(cnp->cn_nameptr) == '/')) {
4351 		do {
4352 			cnp->cn_nameptr++;
4353 			cache_fpl_pathlen_dec(fpl);
4354 		} while (*(cnp->cn_nameptr) == '/');
4355 	}
4356 
4357 	ndp->ni_pathlen = fpl->nulchar - cnp->cn_nameptr + 1;
4358 #ifdef INVARIANTS
4359 	if (ndp->ni_pathlen != fpl->debug.ni_pathlen) {
4360 		panic("%s: mismatch (%zu != %zu) nulchar %p nameptr %p [%s] ; full string [%s]\n",
4361 		    __func__, ndp->ni_pathlen, fpl->debug.ni_pathlen, fpl->nulchar,
4362 		    cnp->cn_nameptr, cnp->cn_nameptr, cnp->cn_pnbuf);
4363 	}
4364 #endif
4365 	return (0);
4366 }
4367 
4368 static int
4369 cache_fplookup_final_child(struct cache_fpl *fpl, enum vgetstate tvs)
4370 {
4371 	struct componentname *cnp;
4372 	struct vnode *tvp;
4373 	seqc_t tvp_seqc;
4374 	int error, lkflags;
4375 
4376 	cnp = fpl->cnp;
4377 	tvp = fpl->tvp;
4378 	tvp_seqc = fpl->tvp_seqc;
4379 
4380 	if ((cnp->cn_flags & LOCKLEAF) != 0) {
4381 		lkflags = LK_SHARED;
4382 		if ((cnp->cn_flags & LOCKSHARED) == 0)
4383 			lkflags = LK_EXCLUSIVE;
4384 		error = vget_finish(tvp, lkflags, tvs);
4385 		if (__predict_false(error != 0)) {
4386 			return (cache_fpl_aborted(fpl));
4387 		}
4388 	} else {
4389 		vget_finish_ref(tvp, tvs);
4390 	}
4391 
4392 	if (!vn_seqc_consistent(tvp, tvp_seqc)) {
4393 		if ((cnp->cn_flags & LOCKLEAF) != 0)
4394 			vput(tvp);
4395 		else
4396 			vrele(tvp);
4397 		return (cache_fpl_aborted(fpl));
4398 	}
4399 
4400 	return (cache_fpl_handled(fpl));
4401 }
4402 
4403 /*
4404  * They want to possibly modify the state of the namecache.
4405  */
4406 static int __noinline
4407 cache_fplookup_final_modifying(struct cache_fpl *fpl)
4408 {
4409 	struct nameidata *ndp;
4410 	struct componentname *cnp;
4411 	enum vgetstate dvs;
4412 	struct vnode *dvp, *tvp;
4413 	struct mount *mp;
4414 	seqc_t dvp_seqc;
4415 	int error;
4416 	bool docache;
4417 
4418 	ndp = fpl->ndp;
4419 	cnp = fpl->cnp;
4420 	dvp = fpl->dvp;
4421 	dvp_seqc = fpl->dvp_seqc;
4422 
4423 	MPASS(*(cnp->cn_nameptr) != '/');
4424 	MPASS(cache_fpl_islastcn(ndp));
4425 	if ((cnp->cn_flags & LOCKPARENT) == 0)
4426 		MPASS((cnp->cn_flags & WANTPARENT) != 0);
4427 	MPASS((cnp->cn_flags & TRAILINGSLASH) == 0);
4428 	MPASS(cnp->cn_nameiop == CREATE || cnp->cn_nameiop == DELETE ||
4429 	    cnp->cn_nameiop == RENAME);
4430 	MPASS((cnp->cn_flags & MAKEENTRY) == 0);
4431 	MPASS((cnp->cn_flags & ISDOTDOT) == 0);
4432 
4433 	docache = (cnp->cn_flags & NOCACHE) ^ NOCACHE;
4434 	if (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME)
4435 		docache = false;
4436 
4437 	/*
4438 	 * Regular lookup nulifies the slash, which we don't do here.
4439 	 * Don't take chances with filesystem routines seeing it for
4440 	 * the last entry.
4441 	 */
4442 	if (cache_fpl_istrailingslash(fpl)) {
4443 		return (cache_fpl_partial(fpl));
4444 	}
4445 
4446 	mp = atomic_load_ptr(&dvp->v_mount);
4447 	if (__predict_false(mp == NULL)) {
4448 		return (cache_fpl_aborted(fpl));
4449 	}
4450 
4451 	if (__predict_false(mp->mnt_flag & MNT_RDONLY)) {
4452 		cache_fpl_smr_exit(fpl);
4453 		/*
4454 		 * Original code keeps not checking for CREATE which
4455 		 * might be a bug. For now let the old lookup decide.
4456 		 */
4457 		if (cnp->cn_nameiop == CREATE) {
4458 			return (cache_fpl_aborted(fpl));
4459 		}
4460 		return (cache_fpl_handled_error(fpl, EROFS));
4461 	}
4462 
4463 	if (fpl->tvp != NULL && (cnp->cn_flags & FAILIFEXISTS) != 0) {
4464 		cache_fpl_smr_exit(fpl);
4465 		return (cache_fpl_handled_error(fpl, EEXIST));
4466 	}
4467 
4468 	/*
4469 	 * Secure access to dvp; check cache_fplookup_partial_setup for
4470 	 * reasoning.
4471 	 *
4472 	 * XXX At least UFS requires its lookup routine to be called for
4473 	 * the last path component, which leads to some level of complication
4474 	 * and inefficiency:
4475 	 * - the target routine always locks the target vnode, but our caller
4476 	 *   may not need it locked
4477 	 * - some of the VOP machinery asserts that the parent is locked, which
4478 	 *   once more may be not required
4479 	 *
4480 	 * TODO: add a flag for filesystems which don't need this.
4481 	 */
4482 	dvs = vget_prep_smr(dvp);
4483 	cache_fpl_smr_exit(fpl);
4484 	if (__predict_false(dvs == VGET_NONE)) {
4485 		return (cache_fpl_aborted(fpl));
4486 	}
4487 
4488 	vget_finish_ref(dvp, dvs);
4489 	if (!vn_seqc_consistent(dvp, dvp_seqc)) {
4490 		vrele(dvp);
4491 		return (cache_fpl_aborted(fpl));
4492 	}
4493 
4494 	error = vn_lock(dvp, LK_EXCLUSIVE);
4495 	if (__predict_false(error != 0)) {
4496 		vrele(dvp);
4497 		return (cache_fpl_aborted(fpl));
4498 	}
4499 
4500 	tvp = NULL;
4501 	cnp->cn_flags |= ISLASTCN;
4502 	if (docache)
4503 		cnp->cn_flags |= MAKEENTRY;
4504 	if (cache_fpl_isdotdot(cnp))
4505 		cnp->cn_flags |= ISDOTDOT;
4506 	cnp->cn_lkflags = LK_EXCLUSIVE;
4507 	error = VOP_LOOKUP(dvp, &tvp, cnp);
4508 	switch (error) {
4509 	case EJUSTRETURN:
4510 	case 0:
4511 		break;
4512 	case ENOTDIR:
4513 	case ENOENT:
4514 		vput(dvp);
4515 		return (cache_fpl_handled_error(fpl, error));
4516 	default:
4517 		vput(dvp);
4518 		return (cache_fpl_aborted(fpl));
4519 	}
4520 
4521 	fpl->tvp = tvp;
4522 	fpl->savename = (cnp->cn_flags & SAVENAME) != 0;
4523 
4524 	if (tvp == NULL) {
4525 		if ((cnp->cn_flags & SAVESTART) != 0) {
4526 			ndp->ni_startdir = dvp;
4527 			vrefact(ndp->ni_startdir);
4528 			cnp->cn_flags |= SAVENAME;
4529 			fpl->savename = true;
4530 		}
4531 		MPASS(error == EJUSTRETURN);
4532 		if ((cnp->cn_flags & LOCKPARENT) == 0) {
4533 			VOP_UNLOCK(dvp);
4534 		}
4535 		return (cache_fpl_handled(fpl));
4536 	}
4537 
4538 	/*
4539 	 * There are very hairy corner cases concerning various flag combinations
4540 	 * and locking state. In particular here we only hold one lock instead of
4541 	 * two.
4542 	 *
4543 	 * Skip the complexity as it is of no significance for normal workloads.
4544 	 */
4545 	if (__predict_false(tvp == dvp)) {
4546 		vput(dvp);
4547 		vrele(tvp);
4548 		return (cache_fpl_aborted(fpl));
4549 	}
4550 
4551 	/*
4552 	 * If they want the symlink itself we are fine, but if they want to
4553 	 * follow it regular lookup has to be engaged.
4554 	 */
4555 	if (tvp->v_type == VLNK) {
4556 		if ((cnp->cn_flags & FOLLOW) != 0) {
4557 			vput(dvp);
4558 			vput(tvp);
4559 			return (cache_fpl_aborted(fpl));
4560 		}
4561 	}
4562 
4563 	/*
4564 	 * Since we expect this to be the terminal vnode it should almost never
4565 	 * be a mount point.
4566 	 */
4567 	if (__predict_false(cache_fplookup_is_mp(fpl))) {
4568 		vput(dvp);
4569 		vput(tvp);
4570 		return (cache_fpl_aborted(fpl));
4571 	}
4572 
4573 	if ((cnp->cn_flags & FAILIFEXISTS) != 0) {
4574 		vput(dvp);
4575 		vput(tvp);
4576 		return (cache_fpl_handled_error(fpl, EEXIST));
4577 	}
4578 
4579 	if ((cnp->cn_flags & LOCKLEAF) == 0) {
4580 		VOP_UNLOCK(tvp);
4581 	}
4582 
4583 	if ((cnp->cn_flags & LOCKPARENT) == 0) {
4584 		VOP_UNLOCK(dvp);
4585 	}
4586 
4587 	if ((cnp->cn_flags & SAVESTART) != 0) {
4588 		ndp->ni_startdir = dvp;
4589 		vrefact(ndp->ni_startdir);
4590 		cnp->cn_flags |= SAVENAME;
4591 		fpl->savename = true;
4592 	}
4593 
4594 	return (cache_fpl_handled(fpl));
4595 }
4596 
4597 static int __noinline
4598 cache_fplookup_modifying(struct cache_fpl *fpl)
4599 {
4600 	struct nameidata *ndp;
4601 
4602 	ndp = fpl->ndp;
4603 
4604 	if (!cache_fpl_islastcn(ndp)) {
4605 		return (cache_fpl_partial(fpl));
4606 	}
4607 	return (cache_fplookup_final_modifying(fpl));
4608 }
4609 
4610 static int __noinline
4611 cache_fplookup_final_withparent(struct cache_fpl *fpl)
4612 {
4613 	struct componentname *cnp;
4614 	enum vgetstate dvs, tvs;
4615 	struct vnode *dvp, *tvp;
4616 	seqc_t dvp_seqc;
4617 	int error;
4618 
4619 	cnp = fpl->cnp;
4620 	dvp = fpl->dvp;
4621 	dvp_seqc = fpl->dvp_seqc;
4622 	tvp = fpl->tvp;
4623 
4624 	MPASS((cnp->cn_flags & (LOCKPARENT|WANTPARENT)) != 0);
4625 
4626 	/*
4627 	 * This is less efficient than it can be for simplicity.
4628 	 */
4629 	dvs = vget_prep_smr(dvp);
4630 	if (__predict_false(dvs == VGET_NONE)) {
4631 		return (cache_fpl_aborted(fpl));
4632 	}
4633 	tvs = vget_prep_smr(tvp);
4634 	if (__predict_false(tvs == VGET_NONE)) {
4635 		cache_fpl_smr_exit(fpl);
4636 		vget_abort(dvp, dvs);
4637 		return (cache_fpl_aborted(fpl));
4638 	}
4639 
4640 	cache_fpl_smr_exit(fpl);
4641 
4642 	if ((cnp->cn_flags & LOCKPARENT) != 0) {
4643 		error = vget_finish(dvp, LK_EXCLUSIVE, dvs);
4644 		if (__predict_false(error != 0)) {
4645 			vget_abort(tvp, tvs);
4646 			return (cache_fpl_aborted(fpl));
4647 		}
4648 	} else {
4649 		vget_finish_ref(dvp, dvs);
4650 	}
4651 
4652 	if (!vn_seqc_consistent(dvp, dvp_seqc)) {
4653 		vget_abort(tvp, tvs);
4654 		if ((cnp->cn_flags & LOCKPARENT) != 0)
4655 			vput(dvp);
4656 		else
4657 			vrele(dvp);
4658 		return (cache_fpl_aborted(fpl));
4659 	}
4660 
4661 	error = cache_fplookup_final_child(fpl, tvs);
4662 	if (__predict_false(error != 0)) {
4663 		MPASS(fpl->status == CACHE_FPL_STATUS_ABORTED ||
4664 		    fpl->status == CACHE_FPL_STATUS_DESTROYED);
4665 		if ((cnp->cn_flags & LOCKPARENT) != 0)
4666 			vput(dvp);
4667 		else
4668 			vrele(dvp);
4669 		return (error);
4670 	}
4671 
4672 	MPASS(fpl->status == CACHE_FPL_STATUS_HANDLED);
4673 	return (0);
4674 }
4675 
4676 static int
4677 cache_fplookup_final(struct cache_fpl *fpl)
4678 {
4679 	struct componentname *cnp;
4680 	enum vgetstate tvs;
4681 	struct vnode *dvp, *tvp;
4682 	seqc_t dvp_seqc;
4683 
4684 	cnp = fpl->cnp;
4685 	dvp = fpl->dvp;
4686 	dvp_seqc = fpl->dvp_seqc;
4687 	tvp = fpl->tvp;
4688 
4689 	MPASS(*(cnp->cn_nameptr) != '/');
4690 
4691 	if (cnp->cn_nameiop != LOOKUP) {
4692 		return (cache_fplookup_final_modifying(fpl));
4693 	}
4694 
4695 	if ((cnp->cn_flags & (LOCKPARENT|WANTPARENT)) != 0)
4696 		return (cache_fplookup_final_withparent(fpl));
4697 
4698 	tvs = vget_prep_smr(tvp);
4699 	if (__predict_false(tvs == VGET_NONE)) {
4700 		return (cache_fpl_partial(fpl));
4701 	}
4702 
4703 	if (!vn_seqc_consistent(dvp, dvp_seqc)) {
4704 		cache_fpl_smr_exit(fpl);
4705 		vget_abort(tvp, tvs);
4706 		return (cache_fpl_aborted(fpl));
4707 	}
4708 
4709 	cache_fpl_smr_exit(fpl);
4710 	return (cache_fplookup_final_child(fpl, tvs));
4711 }
4712 
4713 /*
4714  * Comment from locked lookup:
4715  * Check for degenerate name (e.g. / or "") which is a way of talking about a
4716  * directory, e.g. like "/." or ".".
4717  */
4718 static int __noinline
4719 cache_fplookup_degenerate(struct cache_fpl *fpl)
4720 {
4721 	struct componentname *cnp;
4722 	struct vnode *dvp;
4723 	enum vgetstate dvs;
4724 	int error, lkflags;
4725 #ifdef INVARIANTS
4726 	char *cp;
4727 #endif
4728 
4729 	fpl->tvp = fpl->dvp;
4730 	fpl->tvp_seqc = fpl->dvp_seqc;
4731 
4732 	cnp = fpl->cnp;
4733 	dvp = fpl->dvp;
4734 
4735 #ifdef INVARIANTS
4736 	for (cp = cnp->cn_pnbuf; *cp != '\0'; cp++) {
4737 		KASSERT(*cp == '/',
4738 		    ("%s: encountered non-slash; string [%s]\n", __func__,
4739 		    cnp->cn_pnbuf));
4740 	}
4741 #endif
4742 
4743 	if (__predict_false(cnp->cn_nameiop != LOOKUP)) {
4744 		cache_fpl_smr_exit(fpl);
4745 		return (cache_fpl_handled_error(fpl, EISDIR));
4746 	}
4747 
4748 	MPASS((cnp->cn_flags & SAVESTART) == 0);
4749 
4750 	if ((cnp->cn_flags & (LOCKPARENT|WANTPARENT)) != 0) {
4751 		return (cache_fplookup_final_withparent(fpl));
4752 	}
4753 
4754 	dvs = vget_prep_smr(dvp);
4755 	cache_fpl_smr_exit(fpl);
4756 	if (__predict_false(dvs == VGET_NONE)) {
4757 		return (cache_fpl_aborted(fpl));
4758 	}
4759 
4760 	if ((cnp->cn_flags & LOCKLEAF) != 0) {
4761 		lkflags = LK_SHARED;
4762 		if ((cnp->cn_flags & LOCKSHARED) == 0)
4763 			lkflags = LK_EXCLUSIVE;
4764 		error = vget_finish(dvp, lkflags, dvs);
4765 		if (__predict_false(error != 0)) {
4766 			return (cache_fpl_aborted(fpl));
4767 		}
4768 	} else {
4769 		vget_finish_ref(dvp, dvs);
4770 	}
4771 	return (cache_fpl_handled(fpl));
4772 }
4773 
4774 static int __noinline
4775 cache_fplookup_noentry(struct cache_fpl *fpl)
4776 {
4777 	struct nameidata *ndp;
4778 	struct componentname *cnp;
4779 	enum vgetstate dvs;
4780 	struct vnode *dvp, *tvp;
4781 	seqc_t dvp_seqc;
4782 	int error;
4783 	bool docache;
4784 
4785 	ndp = fpl->ndp;
4786 	cnp = fpl->cnp;
4787 	dvp = fpl->dvp;
4788 	dvp_seqc = fpl->dvp_seqc;
4789 
4790 	MPASS((cnp->cn_flags & MAKEENTRY) == 0);
4791 	MPASS((cnp->cn_flags & ISDOTDOT) == 0);
4792 	MPASS(!cache_fpl_isdotdot(cnp));
4793 
4794 	/*
4795 	 * Hack: delayed name len checking.
4796 	 */
4797 	if (__predict_false(cnp->cn_namelen > NAME_MAX)) {
4798 		cache_fpl_smr_exit(fpl);
4799 		return (cache_fpl_handled_error(fpl, ENAMETOOLONG));
4800 	}
4801 
4802 	if (cnp->cn_nameptr[0] == '/') {
4803 		return (cache_fplookup_skip_slashes(fpl));
4804 	}
4805 
4806 	if (cnp->cn_nameptr[0] == '\0') {
4807 		if (fpl->tvp == NULL) {
4808 			return (cache_fplookup_degenerate(fpl));
4809 		}
4810 		return (cache_fplookup_trailingslash(fpl));
4811 	}
4812 
4813 	if (cnp->cn_nameiop != LOOKUP) {
4814 		fpl->tvp = NULL;
4815 		return (cache_fplookup_modifying(fpl));
4816 	}
4817 
4818 	MPASS((cnp->cn_flags & SAVESTART) == 0);
4819 
4820 	/*
4821 	 * Only try to fill in the component if it is the last one,
4822 	 * otherwise not only there may be several to handle but the
4823 	 * walk may be complicated.
4824 	 */
4825 	if (!cache_fpl_islastcn(ndp)) {
4826 		return (cache_fpl_partial(fpl));
4827 	}
4828 
4829 	/*
4830 	 * Regular lookup nulifies the slash, which we don't do here.
4831 	 * Don't take chances with filesystem routines seeing it for
4832 	 * the last entry.
4833 	 */
4834 	if (cache_fpl_istrailingslash(fpl)) {
4835 		return (cache_fpl_partial(fpl));
4836 	}
4837 
4838 	/*
4839 	 * Secure access to dvp; check cache_fplookup_partial_setup for
4840 	 * reasoning.
4841 	 */
4842 	dvs = vget_prep_smr(dvp);
4843 	cache_fpl_smr_exit(fpl);
4844 	if (__predict_false(dvs == VGET_NONE)) {
4845 		return (cache_fpl_aborted(fpl));
4846 	}
4847 
4848 	vget_finish_ref(dvp, dvs);
4849 	if (!vn_seqc_consistent(dvp, dvp_seqc)) {
4850 		vrele(dvp);
4851 		return (cache_fpl_aborted(fpl));
4852 	}
4853 
4854 	error = vn_lock(dvp, LK_SHARED);
4855 	if (__predict_false(error != 0)) {
4856 		vrele(dvp);
4857 		return (cache_fpl_aborted(fpl));
4858 	}
4859 
4860 	tvp = NULL;
4861 	/*
4862 	 * TODO: provide variants which don't require locking either vnode.
4863 	 */
4864 	cnp->cn_flags |= ISLASTCN;
4865 	docache = (cnp->cn_flags & NOCACHE) ^ NOCACHE;
4866 	if (docache)
4867 		cnp->cn_flags |= MAKEENTRY;
4868 	cnp->cn_lkflags = LK_SHARED;
4869 	if ((cnp->cn_flags & LOCKSHARED) == 0) {
4870 		cnp->cn_lkflags = LK_EXCLUSIVE;
4871 	}
4872 	error = VOP_LOOKUP(dvp, &tvp, cnp);
4873 	switch (error) {
4874 	case EJUSTRETURN:
4875 	case 0:
4876 		break;
4877 	case ENOTDIR:
4878 	case ENOENT:
4879 		vput(dvp);
4880 		return (cache_fpl_handled_error(fpl, error));
4881 	default:
4882 		vput(dvp);
4883 		return (cache_fpl_aborted(fpl));
4884 	}
4885 
4886 	fpl->tvp = tvp;
4887 	if (!fpl->savename) {
4888 		MPASS((cnp->cn_flags & SAVENAME) == 0);
4889 	}
4890 
4891 	if (tvp == NULL) {
4892 		MPASS(error == EJUSTRETURN);
4893 		if ((cnp->cn_flags & (WANTPARENT | LOCKPARENT)) == 0) {
4894 			vput(dvp);
4895 		} else if ((cnp->cn_flags & LOCKPARENT) == 0) {
4896 			VOP_UNLOCK(dvp);
4897 		}
4898 		return (cache_fpl_handled(fpl));
4899 	}
4900 
4901 	if (tvp->v_type == VLNK) {
4902 		if ((cnp->cn_flags & FOLLOW) != 0) {
4903 			vput(dvp);
4904 			vput(tvp);
4905 			return (cache_fpl_aborted(fpl));
4906 		}
4907 	}
4908 
4909 	if (__predict_false(cache_fplookup_is_mp(fpl))) {
4910 		vput(dvp);
4911 		vput(tvp);
4912 		return (cache_fpl_aborted(fpl));
4913 	}
4914 
4915 	if ((cnp->cn_flags & LOCKLEAF) == 0) {
4916 		VOP_UNLOCK(tvp);
4917 	}
4918 
4919 	if ((cnp->cn_flags & (WANTPARENT | LOCKPARENT)) == 0) {
4920 		vput(dvp);
4921 	} else if ((cnp->cn_flags & LOCKPARENT) == 0) {
4922 		VOP_UNLOCK(dvp);
4923 	}
4924 	return (cache_fpl_handled(fpl));
4925 }
4926 
4927 static int __noinline
4928 cache_fplookup_dot(struct cache_fpl *fpl)
4929 {
4930 	int error;
4931 
4932 	MPASS(!seqc_in_modify(fpl->dvp_seqc));
4933 	/*
4934 	 * Just re-assign the value. seqc will be checked later for the first
4935 	 * non-dot path component in line and/or before deciding to return the
4936 	 * vnode.
4937 	 */
4938 	fpl->tvp = fpl->dvp;
4939 	fpl->tvp_seqc = fpl->dvp_seqc;
4940 
4941 	counter_u64_add(dothits, 1);
4942 	SDT_PROBE3(vfs, namecache, lookup, hit, fpl->dvp, ".", fpl->dvp);
4943 
4944 	error = 0;
4945 	if (cache_fplookup_is_mp(fpl)) {
4946 		error = cache_fplookup_cross_mount(fpl);
4947 	}
4948 	return (error);
4949 }
4950 
4951 static int __noinline
4952 cache_fplookup_dotdot(struct cache_fpl *fpl)
4953 {
4954 	struct nameidata *ndp;
4955 	struct componentname *cnp;
4956 	struct namecache *ncp;
4957 	struct vnode *dvp;
4958 	struct prison *pr;
4959 	u_char nc_flag;
4960 
4961 	ndp = fpl->ndp;
4962 	cnp = fpl->cnp;
4963 	dvp = fpl->dvp;
4964 
4965 	MPASS(cache_fpl_isdotdot(cnp));
4966 
4967 	/*
4968 	 * XXX this is racy the same way regular lookup is
4969 	 */
4970 	for (pr = cnp->cn_cred->cr_prison; pr != NULL;
4971 	    pr = pr->pr_parent)
4972 		if (dvp == pr->pr_root)
4973 			break;
4974 
4975 	if (dvp == ndp->ni_rootdir ||
4976 	    dvp == ndp->ni_topdir ||
4977 	    dvp == rootvnode ||
4978 	    pr != NULL) {
4979 		fpl->tvp = dvp;
4980 		fpl->tvp_seqc = vn_seqc_read_any(dvp);
4981 		if (seqc_in_modify(fpl->tvp_seqc)) {
4982 			return (cache_fpl_aborted(fpl));
4983 		}
4984 		return (0);
4985 	}
4986 
4987 	if ((dvp->v_vflag & VV_ROOT) != 0) {
4988 		/*
4989 		 * TODO
4990 		 * The opposite of climb mount is needed here.
4991 		 */
4992 		return (cache_fpl_partial(fpl));
4993 	}
4994 
4995 	ncp = atomic_load_consume_ptr(&dvp->v_cache_dd);
4996 	if (ncp == NULL) {
4997 		return (cache_fpl_aborted(fpl));
4998 	}
4999 
5000 	nc_flag = atomic_load_char(&ncp->nc_flag);
5001 	if ((nc_flag & NCF_ISDOTDOT) != 0) {
5002 		if ((nc_flag & NCF_NEGATIVE) != 0)
5003 			return (cache_fpl_aborted(fpl));
5004 		fpl->tvp = ncp->nc_vp;
5005 	} else {
5006 		fpl->tvp = ncp->nc_dvp;
5007 	}
5008 
5009 	fpl->tvp_seqc = vn_seqc_read_any(fpl->tvp);
5010 	if (seqc_in_modify(fpl->tvp_seqc)) {
5011 		return (cache_fpl_partial(fpl));
5012 	}
5013 
5014 	/*
5015 	 * Acquire fence provided by vn_seqc_read_any above.
5016 	 */
5017 	if (__predict_false(atomic_load_ptr(&dvp->v_cache_dd) != ncp)) {
5018 		return (cache_fpl_aborted(fpl));
5019 	}
5020 
5021 	if (!cache_ncp_canuse(ncp)) {
5022 		return (cache_fpl_aborted(fpl));
5023 	}
5024 
5025 	counter_u64_add(dotdothits, 1);
5026 	return (0);
5027 }
5028 
5029 static int __noinline
5030 cache_fplookup_neg(struct cache_fpl *fpl, struct namecache *ncp, uint32_t hash)
5031 {
5032 	u_char nc_flag;
5033 	bool neg_promote;
5034 
5035 	nc_flag = atomic_load_char(&ncp->nc_flag);
5036 	MPASS((nc_flag & NCF_NEGATIVE) != 0);
5037 	/*
5038 	 * If they want to create an entry we need to replace this one.
5039 	 */
5040 	if (__predict_false(fpl->cnp->cn_nameiop != LOOKUP)) {
5041 		fpl->tvp = NULL;
5042 		return (cache_fplookup_modifying(fpl));
5043 	}
5044 	neg_promote = cache_neg_hit_prep(ncp);
5045 	if (!cache_fpl_neg_ncp_canuse(ncp)) {
5046 		cache_neg_hit_abort(ncp);
5047 		return (cache_fpl_partial(fpl));
5048 	}
5049 	if (neg_promote) {
5050 		return (cache_fplookup_negative_promote(fpl, ncp, hash));
5051 	}
5052 	cache_neg_hit_finish(ncp);
5053 	cache_fpl_smr_exit(fpl);
5054 	return (cache_fpl_handled_error(fpl, ENOENT));
5055 }
5056 
5057 /*
5058  * Resolve a symlink. Called by filesystem-specific routines.
5059  *
5060  * Code flow is:
5061  * ... -> cache_fplookup_symlink -> VOP_FPLOOKUP_SYMLINK -> cache_symlink_resolve
5062  */
5063 int
5064 cache_symlink_resolve(struct cache_fpl *fpl, const char *string, size_t len)
5065 {
5066 	struct nameidata *ndp;
5067 	struct componentname *cnp;
5068 	size_t adjust;
5069 
5070 	ndp = fpl->ndp;
5071 	cnp = fpl->cnp;
5072 
5073 	if (__predict_false(len == 0)) {
5074 		return (ENOENT);
5075 	}
5076 
5077 	if (__predict_false(len > MAXPATHLEN - 2)) {
5078 		if (cache_fpl_istrailingslash(fpl)) {
5079 			return (EAGAIN);
5080 		}
5081 	}
5082 
5083 	ndp->ni_pathlen = fpl->nulchar - cnp->cn_nameptr - cnp->cn_namelen + 1;
5084 #ifdef INVARIANTS
5085 	if (ndp->ni_pathlen != fpl->debug.ni_pathlen) {
5086 		panic("%s: mismatch (%zu != %zu) nulchar %p nameptr %p [%s] ; full string [%s]\n",
5087 		    __func__, ndp->ni_pathlen, fpl->debug.ni_pathlen, fpl->nulchar,
5088 		    cnp->cn_nameptr, cnp->cn_nameptr, cnp->cn_pnbuf);
5089 	}
5090 #endif
5091 
5092 	if (__predict_false(len + ndp->ni_pathlen > MAXPATHLEN)) {
5093 		return (ENAMETOOLONG);
5094 	}
5095 
5096 	if (__predict_false(ndp->ni_loopcnt++ >= MAXSYMLINKS)) {
5097 		return (ELOOP);
5098 	}
5099 
5100 	adjust = len;
5101 	if (ndp->ni_pathlen > 1) {
5102 		bcopy(ndp->ni_next, cnp->cn_pnbuf + len, ndp->ni_pathlen);
5103 	} else {
5104 		if (cache_fpl_istrailingslash(fpl)) {
5105 			adjust = len + 1;
5106 			cnp->cn_pnbuf[len] = '/';
5107 			cnp->cn_pnbuf[len + 1] = '\0';
5108 		} else {
5109 			cnp->cn_pnbuf[len] = '\0';
5110 		}
5111 	}
5112 	bcopy(string, cnp->cn_pnbuf, len);
5113 
5114 	ndp->ni_pathlen += adjust;
5115 	cache_fpl_pathlen_add(fpl, adjust);
5116 	cnp->cn_nameptr = cnp->cn_pnbuf;
5117 	fpl->nulchar = &cnp->cn_nameptr[ndp->ni_pathlen - 1];
5118 	fpl->tvp = NULL;
5119 	return (0);
5120 }
5121 
5122 static int __noinline
5123 cache_fplookup_symlink(struct cache_fpl *fpl)
5124 {
5125 	struct mount *mp;
5126 	struct nameidata *ndp;
5127 	struct componentname *cnp;
5128 	struct vnode *dvp, *tvp;
5129 	int error;
5130 
5131 	ndp = fpl->ndp;
5132 	cnp = fpl->cnp;
5133 	dvp = fpl->dvp;
5134 	tvp = fpl->tvp;
5135 
5136 	if (cache_fpl_islastcn(ndp)) {
5137 		if ((cnp->cn_flags & FOLLOW) == 0) {
5138 			return (cache_fplookup_final(fpl));
5139 		}
5140 	}
5141 
5142 	mp = atomic_load_ptr(&dvp->v_mount);
5143 	if (__predict_false(mp == NULL)) {
5144 		return (cache_fpl_aborted(fpl));
5145 	}
5146 
5147 	/*
5148 	 * Note this check races against setting the flag just like regular
5149 	 * lookup.
5150 	 */
5151 	if (__predict_false((mp->mnt_flag & MNT_NOSYMFOLLOW) != 0)) {
5152 		cache_fpl_smr_exit(fpl);
5153 		return (cache_fpl_handled_error(fpl, EACCES));
5154 	}
5155 
5156 	error = VOP_FPLOOKUP_SYMLINK(tvp, fpl);
5157 	if (__predict_false(error != 0)) {
5158 		switch (error) {
5159 		case EAGAIN:
5160 			return (cache_fpl_partial(fpl));
5161 		case ENOENT:
5162 		case ENAMETOOLONG:
5163 		case ELOOP:
5164 			cache_fpl_smr_exit(fpl);
5165 			return (cache_fpl_handled_error(fpl, error));
5166 		default:
5167 			return (cache_fpl_aborted(fpl));
5168 		}
5169 	}
5170 
5171 	if (*(cnp->cn_nameptr) == '/') {
5172 		fpl->dvp = cache_fpl_handle_root(fpl);
5173 		fpl->dvp_seqc = vn_seqc_read_any(fpl->dvp);
5174 		if (seqc_in_modify(fpl->dvp_seqc)) {
5175 			return (cache_fpl_aborted(fpl));
5176 		}
5177 	}
5178 	return (0);
5179 }
5180 
5181 static int
5182 cache_fplookup_next(struct cache_fpl *fpl)
5183 {
5184 	struct componentname *cnp;
5185 	struct namecache *ncp;
5186 	struct vnode *dvp, *tvp;
5187 	u_char nc_flag;
5188 	uint32_t hash;
5189 	int error;
5190 
5191 	cnp = fpl->cnp;
5192 	dvp = fpl->dvp;
5193 	hash = fpl->hash;
5194 
5195 	if (__predict_false(cnp->cn_nameptr[0] == '.')) {
5196 		if (cnp->cn_namelen == 1) {
5197 			return (cache_fplookup_dot(fpl));
5198 		}
5199 		if (cnp->cn_namelen == 2 && cnp->cn_nameptr[1] == '.') {
5200 			return (cache_fplookup_dotdot(fpl));
5201 		}
5202 	}
5203 
5204 	MPASS(!cache_fpl_isdotdot(cnp));
5205 
5206 	CK_SLIST_FOREACH(ncp, (NCHHASH(hash)), nc_hash) {
5207 		if (ncp->nc_dvp == dvp && ncp->nc_nlen == cnp->cn_namelen &&
5208 		    !bcmp(ncp->nc_name, cnp->cn_nameptr, ncp->nc_nlen))
5209 			break;
5210 	}
5211 
5212 	if (__predict_false(ncp == NULL)) {
5213 		return (cache_fplookup_noentry(fpl));
5214 	}
5215 
5216 	tvp = atomic_load_ptr(&ncp->nc_vp);
5217 	nc_flag = atomic_load_char(&ncp->nc_flag);
5218 	if ((nc_flag & NCF_NEGATIVE) != 0) {
5219 		return (cache_fplookup_neg(fpl, ncp, hash));
5220 	}
5221 
5222 	if (!cache_ncp_canuse(ncp)) {
5223 		return (cache_fpl_partial(fpl));
5224 	}
5225 
5226 	fpl->tvp = tvp;
5227 	fpl->tvp_seqc = vn_seqc_read_any(tvp);
5228 	if (seqc_in_modify(fpl->tvp_seqc)) {
5229 		return (cache_fpl_partial(fpl));
5230 	}
5231 
5232 	counter_u64_add(numposhits, 1);
5233 	SDT_PROBE3(vfs, namecache, lookup, hit, dvp, ncp->nc_name, tvp);
5234 
5235 	error = 0;
5236 	if (cache_fplookup_is_mp(fpl)) {
5237 		error = cache_fplookup_cross_mount(fpl);
5238 	}
5239 	return (error);
5240 }
5241 
5242 static bool
5243 cache_fplookup_mp_supported(struct mount *mp)
5244 {
5245 
5246 	MPASS(mp != NULL);
5247 	if ((mp->mnt_kern_flag & MNTK_FPLOOKUP) == 0)
5248 		return (false);
5249 	return (true);
5250 }
5251 
5252 /*
5253  * Walk up the mount stack (if any).
5254  *
5255  * Correctness is provided in the following ways:
5256  * - all vnodes are protected from freeing with SMR
5257  * - struct mount objects are type stable making them always safe to access
5258  * - stability of the particular mount is provided by busying it
5259  * - relationship between the vnode which is mounted on and the mount is
5260  *   verified with the vnode sequence counter after busying
5261  * - association between root vnode of the mount and the mount is protected
5262  *   by busy
5263  *
5264  * From that point on we can read the sequence counter of the root vnode
5265  * and get the next mount on the stack (if any) using the same protection.
5266  *
5267  * By the end of successful walk we are guaranteed the reached state was
5268  * indeed present at least at some point which matches the regular lookup.
5269  */
5270 static int __noinline
5271 cache_fplookup_climb_mount(struct cache_fpl *fpl)
5272 {
5273 	struct mount *mp, *prev_mp;
5274 	struct mount_pcpu *mpcpu, *prev_mpcpu;
5275 	struct vnode *vp;
5276 	seqc_t vp_seqc;
5277 
5278 	vp = fpl->tvp;
5279 	vp_seqc = fpl->tvp_seqc;
5280 
5281 	VNPASS(vp->v_type == VDIR || vp->v_type == VBAD, vp);
5282 	mp = atomic_load_ptr(&vp->v_mountedhere);
5283 	if (__predict_false(mp == NULL)) {
5284 		return (0);
5285 	}
5286 
5287 	prev_mp = NULL;
5288 	for (;;) {
5289 		if (!vfs_op_thread_enter_crit(mp, mpcpu)) {
5290 			if (prev_mp != NULL)
5291 				vfs_op_thread_exit_crit(prev_mp, prev_mpcpu);
5292 			return (cache_fpl_partial(fpl));
5293 		}
5294 		if (prev_mp != NULL)
5295 			vfs_op_thread_exit_crit(prev_mp, prev_mpcpu);
5296 		if (!vn_seqc_consistent(vp, vp_seqc)) {
5297 			vfs_op_thread_exit_crit(mp, mpcpu);
5298 			return (cache_fpl_partial(fpl));
5299 		}
5300 		if (!cache_fplookup_mp_supported(mp)) {
5301 			vfs_op_thread_exit_crit(mp, mpcpu);
5302 			return (cache_fpl_partial(fpl));
5303 		}
5304 		vp = atomic_load_ptr(&mp->mnt_rootvnode);
5305 		if (vp == NULL) {
5306 			vfs_op_thread_exit_crit(mp, mpcpu);
5307 			return (cache_fpl_partial(fpl));
5308 		}
5309 		vp_seqc = vn_seqc_read_any(vp);
5310 		if (seqc_in_modify(vp_seqc)) {
5311 			vfs_op_thread_exit_crit(mp, mpcpu);
5312 			return (cache_fpl_partial(fpl));
5313 		}
5314 		prev_mp = mp;
5315 		prev_mpcpu = mpcpu;
5316 		mp = atomic_load_ptr(&vp->v_mountedhere);
5317 		if (mp == NULL)
5318 			break;
5319 	}
5320 
5321 	vfs_op_thread_exit_crit(prev_mp, prev_mpcpu);
5322 	fpl->tvp = vp;
5323 	fpl->tvp_seqc = vp_seqc;
5324 	return (0);
5325 }
5326 
5327 static int __noinline
5328 cache_fplookup_cross_mount(struct cache_fpl *fpl)
5329 {
5330 	struct mount *mp;
5331 	struct mount_pcpu *mpcpu;
5332 	struct vnode *vp;
5333 	seqc_t vp_seqc;
5334 
5335 	vp = fpl->tvp;
5336 	vp_seqc = fpl->tvp_seqc;
5337 
5338 	VNPASS(vp->v_type == VDIR || vp->v_type == VBAD, vp);
5339 	mp = atomic_load_ptr(&vp->v_mountedhere);
5340 	if (__predict_false(mp == NULL)) {
5341 		return (0);
5342 	}
5343 
5344 	if (!vfs_op_thread_enter_crit(mp, mpcpu)) {
5345 		return (cache_fpl_partial(fpl));
5346 	}
5347 	if (!vn_seqc_consistent(vp, vp_seqc)) {
5348 		vfs_op_thread_exit_crit(mp, mpcpu);
5349 		return (cache_fpl_partial(fpl));
5350 	}
5351 	if (!cache_fplookup_mp_supported(mp)) {
5352 		vfs_op_thread_exit_crit(mp, mpcpu);
5353 		return (cache_fpl_partial(fpl));
5354 	}
5355 	vp = atomic_load_ptr(&mp->mnt_rootvnode);
5356 	if (__predict_false(vp == NULL)) {
5357 		vfs_op_thread_exit_crit(mp, mpcpu);
5358 		return (cache_fpl_partial(fpl));
5359 	}
5360 	vp_seqc = vn_seqc_read_any(vp);
5361 	vfs_op_thread_exit_crit(mp, mpcpu);
5362 	if (seqc_in_modify(vp_seqc)) {
5363 		return (cache_fpl_partial(fpl));
5364 	}
5365 	mp = atomic_load_ptr(&vp->v_mountedhere);
5366 	if (__predict_false(mp != NULL)) {
5367 		/*
5368 		 * There are possibly more mount points on top.
5369 		 * Normally this does not happen so for simplicity just start
5370 		 * over.
5371 		 */
5372 		return (cache_fplookup_climb_mount(fpl));
5373 	}
5374 
5375 	fpl->tvp = vp;
5376 	fpl->tvp_seqc = vp_seqc;
5377 	return (0);
5378 }
5379 
5380 /*
5381  * Check if a vnode is mounted on.
5382  */
5383 static bool
5384 cache_fplookup_is_mp(struct cache_fpl *fpl)
5385 {
5386 	struct vnode *vp;
5387 
5388 	vp = fpl->tvp;
5389 	return ((vn_irflag_read(vp) & VIRF_MOUNTPOINT) != 0);
5390 }
5391 
5392 /*
5393  * Parse the path.
5394  *
5395  * The code was originally copy-pasted from regular lookup and despite
5396  * clean ups leaves performance on the table. Any modifications here
5397  * must take into account that in case off fallback the resulting
5398  * nameidata state has to be compatible with the original.
5399  */
5400 
5401 /*
5402  * Debug ni_pathlen tracking.
5403  */
5404 #ifdef INVARIANTS
5405 static void
5406 cache_fpl_pathlen_add(struct cache_fpl *fpl, size_t n)
5407 {
5408 
5409 	fpl->debug.ni_pathlen += n;
5410 	KASSERT(fpl->debug.ni_pathlen <= PATH_MAX,
5411 	    ("%s: pathlen overflow to %zd\n", __func__, fpl->debug.ni_pathlen));
5412 }
5413 
5414 static void
5415 cache_fpl_pathlen_sub(struct cache_fpl *fpl, size_t n)
5416 {
5417 
5418 	fpl->debug.ni_pathlen -= n;
5419 	KASSERT(fpl->debug.ni_pathlen <= PATH_MAX,
5420 	    ("%s: pathlen underflow to %zd\n", __func__, fpl->debug.ni_pathlen));
5421 }
5422 
5423 static void
5424 cache_fpl_pathlen_inc(struct cache_fpl *fpl)
5425 {
5426 
5427 	cache_fpl_pathlen_add(fpl, 1);
5428 }
5429 
5430 static void
5431 cache_fpl_pathlen_dec(struct cache_fpl *fpl)
5432 {
5433 
5434 	cache_fpl_pathlen_sub(fpl, 1);
5435 }
5436 #else
5437 static void
5438 cache_fpl_pathlen_add(struct cache_fpl *fpl, size_t n)
5439 {
5440 }
5441 
5442 static void
5443 cache_fpl_pathlen_sub(struct cache_fpl *fpl, size_t n)
5444 {
5445 }
5446 
5447 static void
5448 cache_fpl_pathlen_inc(struct cache_fpl *fpl)
5449 {
5450 }
5451 
5452 static void
5453 cache_fpl_pathlen_dec(struct cache_fpl *fpl)
5454 {
5455 }
5456 #endif
5457 
5458 static void
5459 cache_fplookup_parse(struct cache_fpl *fpl)
5460 {
5461 	struct nameidata *ndp;
5462 	struct componentname *cnp;
5463 	struct vnode *dvp;
5464 	char *cp;
5465 	uint32_t hash;
5466 
5467 	ndp = fpl->ndp;
5468 	cnp = fpl->cnp;
5469 	dvp = fpl->dvp;
5470 
5471 	/*
5472 	 * Find the end of this path component, it is either / or nul.
5473 	 *
5474 	 * Store / as a temporary sentinel so that we only have one character
5475 	 * to test for. Pathnames tend to be short so this should not be
5476 	 * resulting in cache misses.
5477 	 *
5478 	 * TODO: fix this to be word-sized.
5479 	 */
5480 	KASSERT(&cnp->cn_nameptr[fpl->debug.ni_pathlen - 1] == fpl->nulchar,
5481 	    ("%s: mismatch between pathlen (%zu) and nulchar (%p != %p), string [%s]\n",
5482 	    __func__, fpl->debug.ni_pathlen, &cnp->cn_nameptr[fpl->debug.ni_pathlen - 1],
5483 	    fpl->nulchar, cnp->cn_pnbuf));
5484 	KASSERT(*fpl->nulchar == '\0',
5485 	    ("%s: expected nul at %p; string [%s]\n", __func__, fpl->nulchar,
5486 	    cnp->cn_pnbuf));
5487 	hash = cache_get_hash_iter_start(dvp);
5488 	*fpl->nulchar = '/';
5489 	for (cp = cnp->cn_nameptr; *cp != '/'; cp++) {
5490 		KASSERT(*cp != '\0',
5491 		    ("%s: encountered unexpected nul; string [%s]\n", __func__,
5492 		    cnp->cn_nameptr));
5493 		hash = cache_get_hash_iter(*cp, hash);
5494 		continue;
5495 	}
5496 	*fpl->nulchar = '\0';
5497 	fpl->hash = cache_get_hash_iter_finish(hash);
5498 
5499 	cnp->cn_namelen = cp - cnp->cn_nameptr;
5500 	cache_fpl_pathlen_sub(fpl, cnp->cn_namelen);
5501 
5502 #ifdef INVARIANTS
5503 	/*
5504 	 * cache_get_hash only accepts lengths up to NAME_MAX. This is fine since
5505 	 * we are going to fail this lookup with ENAMETOOLONG (see below).
5506 	 */
5507 	if (cnp->cn_namelen <= NAME_MAX) {
5508 		if (fpl->hash != cache_get_hash(cnp->cn_nameptr, cnp->cn_namelen, dvp)) {
5509 			panic("%s: mismatched hash for [%s] len %ld", __func__,
5510 			    cnp->cn_nameptr, cnp->cn_namelen);
5511 		}
5512 	}
5513 #endif
5514 
5515 	/*
5516 	 * Hack: we have to check if the found path component's length exceeds
5517 	 * NAME_MAX. However, the condition is very rarely true and check can
5518 	 * be elided in the common case -- if an entry was found in the cache,
5519 	 * then it could not have been too long to begin with.
5520 	 */
5521 	ndp->ni_next = cp;
5522 }
5523 
5524 static void
5525 cache_fplookup_parse_advance(struct cache_fpl *fpl)
5526 {
5527 	struct nameidata *ndp;
5528 	struct componentname *cnp;
5529 
5530 	ndp = fpl->ndp;
5531 	cnp = fpl->cnp;
5532 
5533 	cnp->cn_nameptr = ndp->ni_next;
5534 	KASSERT(*(cnp->cn_nameptr) == '/',
5535 	    ("%s: should have seen slash at %p ; buf %p [%s]\n", __func__,
5536 	    cnp->cn_nameptr, cnp->cn_pnbuf, cnp->cn_pnbuf));
5537 	cnp->cn_nameptr++;
5538 	cache_fpl_pathlen_dec(fpl);
5539 }
5540 
5541 /*
5542  * Skip spurious slashes in a pathname (e.g., "foo///bar") and retry.
5543  *
5544  * Lockless lookup tries to elide checking for spurious slashes and should they
5545  * be present is guaranteed to fail to find an entry. In this case the caller
5546  * must check if the name starts with a slash and call this routine.  It is
5547  * going to fast forward across the spurious slashes and set the state up for
5548  * retry.
5549  */
5550 static int __noinline
5551 cache_fplookup_skip_slashes(struct cache_fpl *fpl)
5552 {
5553 	struct nameidata *ndp;
5554 	struct componentname *cnp;
5555 
5556 	ndp = fpl->ndp;
5557 	cnp = fpl->cnp;
5558 
5559 	MPASS(*(cnp->cn_nameptr) == '/');
5560 	do {
5561 		cnp->cn_nameptr++;
5562 		cache_fpl_pathlen_dec(fpl);
5563 	} while (*(cnp->cn_nameptr) == '/');
5564 
5565 	/*
5566 	 * Go back to one slash so that cache_fplookup_parse_advance has
5567 	 * something to skip.
5568 	 */
5569 	cnp->cn_nameptr--;
5570 	cache_fpl_pathlen_inc(fpl);
5571 
5572 	/*
5573 	 * cache_fplookup_parse_advance starts from ndp->ni_next
5574 	 */
5575 	ndp->ni_next = cnp->cn_nameptr;
5576 
5577 	/*
5578 	 * See cache_fplookup_dot.
5579 	 */
5580 	fpl->tvp = fpl->dvp;
5581 	fpl->tvp_seqc = fpl->dvp_seqc;
5582 
5583 	return (0);
5584 }
5585 
5586 /*
5587  * Handle trailing slashes (e.g., "foo/").
5588  *
5589  * If a trailing slash is found the terminal vnode must be a directory.
5590  * Regular lookup shortens the path by nulifying the first trailing slash and
5591  * sets the TRAILINGSLASH flag to denote this took place. There are several
5592  * checks on it performed later.
5593  *
5594  * Similarly to spurious slashes, lockless lookup handles this in a speculative
5595  * manner relying on an invariant that a non-directory vnode will get a miss.
5596  * In this case cn_nameptr[0] == '\0' and cn_namelen == 0.
5597  *
5598  * Thus for a path like "foo/bar/" the code unwinds the state back to "bar/"
5599  * and denotes this is the last path component, which avoids looping back.
5600  *
5601  * Only plain lookups are supported for now to restrict corner cases to handle.
5602  */
5603 static int __noinline
5604 cache_fplookup_trailingslash(struct cache_fpl *fpl)
5605 {
5606 #ifdef INVARIANTS
5607 	size_t ni_pathlen;
5608 #endif
5609 	struct nameidata *ndp;
5610 	struct componentname *cnp;
5611 	struct namecache *ncp;
5612 	struct vnode *tvp;
5613 	char *cn_nameptr_orig, *cn_nameptr_slash;
5614 	seqc_t tvp_seqc;
5615 	u_char nc_flag;
5616 
5617 	ndp = fpl->ndp;
5618 	cnp = fpl->cnp;
5619 	tvp = fpl->tvp;
5620 	tvp_seqc = fpl->tvp_seqc;
5621 
5622 	MPASS(fpl->dvp == fpl->tvp);
5623 	KASSERT(cache_fpl_istrailingslash(fpl),
5624 	    ("%s: expected trailing slash at %p; string [%s]\n", __func__, fpl->nulchar - 1,
5625 	    cnp->cn_pnbuf));
5626 	KASSERT(cnp->cn_nameptr[0] == '\0',
5627 	    ("%s: expected nul char at %p; string [%s]\n", __func__, &cnp->cn_nameptr[0],
5628 	    cnp->cn_pnbuf));
5629 	KASSERT(cnp->cn_namelen == 0,
5630 	    ("%s: namelen 0 but got %ld; string [%s]\n", __func__, cnp->cn_namelen,
5631 	    cnp->cn_pnbuf));
5632 	MPASS(cnp->cn_nameptr > cnp->cn_pnbuf);
5633 
5634 	if (cnp->cn_nameiop != LOOKUP) {
5635 		return (cache_fpl_aborted(fpl));
5636 	}
5637 
5638 	if (__predict_false(tvp->v_type != VDIR)) {
5639 		if (!vn_seqc_consistent(tvp, tvp_seqc)) {
5640 			return (cache_fpl_aborted(fpl));
5641 		}
5642 		cache_fpl_smr_exit(fpl);
5643 		return (cache_fpl_handled_error(fpl, ENOTDIR));
5644 	}
5645 
5646 	/*
5647 	 * Denote the last component.
5648 	 */
5649 	ndp->ni_next = &cnp->cn_nameptr[0];
5650 	MPASS(cache_fpl_islastcn(ndp));
5651 
5652 	/*
5653 	 * Unwind trailing slashes.
5654 	 */
5655 	cn_nameptr_orig = cnp->cn_nameptr;
5656 	while (cnp->cn_nameptr >= cnp->cn_pnbuf) {
5657 		cnp->cn_nameptr--;
5658 		if (cnp->cn_nameptr[0] != '/') {
5659 			break;
5660 		}
5661 	}
5662 
5663 	/*
5664 	 * Unwind to the beginning of the path component.
5665 	 *
5666 	 * Note the path may or may not have started with a slash.
5667 	 */
5668 	cn_nameptr_slash = cnp->cn_nameptr;
5669 	while (cnp->cn_nameptr > cnp->cn_pnbuf) {
5670 		cnp->cn_nameptr--;
5671 		if (cnp->cn_nameptr[0] == '/') {
5672 			break;
5673 		}
5674 	}
5675 	if (cnp->cn_nameptr[0] == '/') {
5676 		cnp->cn_nameptr++;
5677 	}
5678 
5679 	cnp->cn_namelen = cn_nameptr_slash - cnp->cn_nameptr + 1;
5680 	cache_fpl_pathlen_add(fpl, cn_nameptr_orig - cnp->cn_nameptr);
5681 	cache_fpl_checkpoint(fpl);
5682 
5683 #ifdef INVARIANTS
5684 	ni_pathlen = fpl->nulchar - cnp->cn_nameptr + 1;
5685 	if (ni_pathlen != fpl->debug.ni_pathlen) {
5686 		panic("%s: mismatch (%zu != %zu) nulchar %p nameptr %p [%s] ; full string [%s]\n",
5687 		    __func__, ni_pathlen, fpl->debug.ni_pathlen, fpl->nulchar,
5688 		    cnp->cn_nameptr, cnp->cn_nameptr, cnp->cn_pnbuf);
5689 	}
5690 #endif
5691 
5692 	/*
5693 	 * If this was a "./" lookup the parent directory is already correct.
5694 	 */
5695 	if (cnp->cn_nameptr[0] == '.' && cnp->cn_namelen == 1) {
5696 		return (0);
5697 	}
5698 
5699 	/*
5700 	 * Otherwise we need to look it up.
5701 	 */
5702 	tvp = fpl->tvp;
5703 	ncp = atomic_load_consume_ptr(&tvp->v_cache_dd);
5704 	if (__predict_false(ncp == NULL)) {
5705 		return (cache_fpl_aborted(fpl));
5706 	}
5707 	nc_flag = atomic_load_char(&ncp->nc_flag);
5708 	if ((nc_flag & NCF_ISDOTDOT) != 0) {
5709 		return (cache_fpl_aborted(fpl));
5710 	}
5711 	fpl->dvp = ncp->nc_dvp;
5712 	fpl->dvp_seqc = vn_seqc_read_any(fpl->dvp);
5713 	if (seqc_in_modify(fpl->dvp_seqc)) {
5714 		return (cache_fpl_aborted(fpl));
5715 	}
5716 	return (0);
5717 }
5718 
5719 /*
5720  * See the API contract for VOP_FPLOOKUP_VEXEC.
5721  */
5722 static int __noinline
5723 cache_fplookup_failed_vexec(struct cache_fpl *fpl, int error)
5724 {
5725 	struct componentname *cnp;
5726 	struct vnode *dvp;
5727 	seqc_t dvp_seqc;
5728 
5729 	cnp = fpl->cnp;
5730 	dvp = fpl->dvp;
5731 	dvp_seqc = fpl->dvp_seqc;
5732 
5733 	/*
5734 	 * TODO: Due to ignoring trailing slashes lookup will perform a
5735 	 * permission check on the last dir when it should not be doing it.  It
5736 	 * may fail, but said failure should be ignored. It is possible to fix
5737 	 * it up fully without resorting to regular lookup, but for now just
5738 	 * abort.
5739 	 */
5740 	if (cache_fpl_istrailingslash(fpl)) {
5741 		return (cache_fpl_aborted(fpl));
5742 	}
5743 
5744 	/*
5745 	 * Hack: delayed degenerate path checking.
5746 	 */
5747 	if (cnp->cn_nameptr[0] == '\0' && fpl->tvp == NULL) {
5748 		return (cache_fplookup_degenerate(fpl));
5749 	}
5750 
5751 	/*
5752 	 * Hack: delayed name len checking.
5753 	 */
5754 	if (__predict_false(cnp->cn_namelen > NAME_MAX)) {
5755 		cache_fpl_smr_exit(fpl);
5756 		return (cache_fpl_handled_error(fpl, ENAMETOOLONG));
5757 	}
5758 
5759 	/*
5760 	 * Hack: they may be looking up foo/bar, where foo is not a directory.
5761 	 * In such a case we need to return ENOTDIR, but we may happen to get
5762 	 * here with a different error.
5763 	 */
5764 	if (dvp->v_type != VDIR) {
5765 		error = ENOTDIR;
5766 	}
5767 
5768 	/*
5769 	 * Hack: handle O_SEARCH.
5770 	 *
5771 	 * Open Group Base Specifications Issue 7, 2018 edition states:
5772 	 * <quote>
5773 	 * If the access mode of the open file description associated with the
5774 	 * file descriptor is not O_SEARCH, the function shall check whether
5775 	 * directory searches are permitted using the current permissions of
5776 	 * the directory underlying the file descriptor. If the access mode is
5777 	 * O_SEARCH, the function shall not perform the check.
5778 	 * </quote>
5779 	 *
5780 	 * Regular lookup tests for the NOEXECCHECK flag for every path
5781 	 * component to decide whether to do the permission check. However,
5782 	 * since most lookups never have the flag (and when they do it is only
5783 	 * present for the first path component), lockless lookup only acts on
5784 	 * it if there is a permission problem. Here the flag is represented
5785 	 * with a boolean so that we don't have to clear it on the way out.
5786 	 *
5787 	 * For simplicity this always aborts.
5788 	 * TODO: check if this is the first lookup and ignore the permission
5789 	 * problem. Note the flag has to survive fallback (if it happens to be
5790 	 * performed).
5791 	 */
5792 	if (fpl->fsearch) {
5793 		return (cache_fpl_aborted(fpl));
5794 	}
5795 
5796 	switch (error) {
5797 	case EAGAIN:
5798 		if (!vn_seqc_consistent(dvp, dvp_seqc)) {
5799 			error = cache_fpl_aborted(fpl);
5800 		} else {
5801 			cache_fpl_partial(fpl);
5802 		}
5803 		break;
5804 	default:
5805 		if (!vn_seqc_consistent(dvp, dvp_seqc)) {
5806 			error = cache_fpl_aborted(fpl);
5807 		} else {
5808 			cache_fpl_smr_exit(fpl);
5809 			cache_fpl_handled_error(fpl, error);
5810 		}
5811 		break;
5812 	}
5813 	return (error);
5814 }
5815 
5816 static int
5817 cache_fplookup_impl(struct vnode *dvp, struct cache_fpl *fpl)
5818 {
5819 	struct nameidata *ndp;
5820 	struct componentname *cnp;
5821 	struct mount *mp;
5822 	int error;
5823 
5824 	ndp = fpl->ndp;
5825 	cnp = fpl->cnp;
5826 
5827 	cache_fpl_checkpoint(fpl);
5828 
5829 	/*
5830 	 * The vnode at hand is almost always stable, skip checking for it.
5831 	 * Worst case this postpones the check towards the end of the iteration
5832 	 * of the main loop.
5833 	 */
5834 	fpl->dvp = dvp;
5835 	fpl->dvp_seqc = vn_seqc_read_notmodify(fpl->dvp);
5836 
5837 	mp = atomic_load_ptr(&dvp->v_mount);
5838 	if (__predict_false(mp == NULL || !cache_fplookup_mp_supported(mp))) {
5839 		return (cache_fpl_aborted(fpl));
5840 	}
5841 
5842 	MPASS(fpl->tvp == NULL);
5843 
5844 	for (;;) {
5845 		cache_fplookup_parse(fpl);
5846 
5847 		error = VOP_FPLOOKUP_VEXEC(fpl->dvp, cnp->cn_cred);
5848 		if (__predict_false(error != 0)) {
5849 			error = cache_fplookup_failed_vexec(fpl, error);
5850 			break;
5851 		}
5852 
5853 		error = cache_fplookup_next(fpl);
5854 		if (__predict_false(cache_fpl_terminated(fpl))) {
5855 			break;
5856 		}
5857 
5858 		VNPASS(!seqc_in_modify(fpl->tvp_seqc), fpl->tvp);
5859 
5860 		if (fpl->tvp->v_type == VLNK) {
5861 			error = cache_fplookup_symlink(fpl);
5862 			if (cache_fpl_terminated(fpl)) {
5863 				break;
5864 			}
5865 		} else {
5866 			if (cache_fpl_islastcn(ndp)) {
5867 				error = cache_fplookup_final(fpl);
5868 				break;
5869 			}
5870 
5871 			if (!vn_seqc_consistent(fpl->dvp, fpl->dvp_seqc)) {
5872 				error = cache_fpl_aborted(fpl);
5873 				break;
5874 			}
5875 
5876 			fpl->dvp = fpl->tvp;
5877 			fpl->dvp_seqc = fpl->tvp_seqc;
5878 			cache_fplookup_parse_advance(fpl);
5879 		}
5880 
5881 		cache_fpl_checkpoint(fpl);
5882 	}
5883 
5884 	return (error);
5885 }
5886 
5887 /*
5888  * Fast path lookup protected with SMR and sequence counters.
5889  *
5890  * Note: all VOP_FPLOOKUP_VEXEC routines have a comment referencing this one.
5891  *
5892  * Filesystems can opt in by setting the MNTK_FPLOOKUP flag and meeting criteria
5893  * outlined below.
5894  *
5895  * Traditional vnode lookup conceptually looks like this:
5896  *
5897  * vn_lock(current);
5898  * for (;;) {
5899  *	next = find();
5900  *	vn_lock(next);
5901  *	vn_unlock(current);
5902  *	current = next;
5903  *	if (last)
5904  *	    break;
5905  * }
5906  * return (current);
5907  *
5908  * Each jump to the next vnode is safe memory-wise and atomic with respect to
5909  * any modifications thanks to holding respective locks.
5910  *
5911  * The same guarantee can be provided with a combination of safe memory
5912  * reclamation and sequence counters instead. If all operations which affect
5913  * the relationship between the current vnode and the one we are looking for
5914  * also modify the counter, we can verify whether all the conditions held as
5915  * we made the jump. This includes things like permissions, mount points etc.
5916  * Counter modification is provided by enclosing relevant places in
5917  * vn_seqc_write_begin()/end() calls.
5918  *
5919  * Thus this translates to:
5920  *
5921  * vfs_smr_enter();
5922  * dvp_seqc = seqc_read_any(dvp);
5923  * if (seqc_in_modify(dvp_seqc)) // someone is altering the vnode
5924  *     abort();
5925  * for (;;) {
5926  * 	tvp = find();
5927  * 	tvp_seqc = seqc_read_any(tvp);
5928  * 	if (seqc_in_modify(tvp_seqc)) // someone is altering the target vnode
5929  * 	    abort();
5930  * 	if (!seqc_consistent(dvp, dvp_seqc) // someone is altering the vnode
5931  * 	    abort();
5932  * 	dvp = tvp; // we know nothing of importance has changed
5933  * 	dvp_seqc = tvp_seqc; // store the counter for the tvp iteration
5934  * 	if (last)
5935  * 	    break;
5936  * }
5937  * vget(); // secure the vnode
5938  * if (!seqc_consistent(tvp, tvp_seqc) // final check
5939  * 	    abort();
5940  * // at this point we know nothing has changed for any parent<->child pair
5941  * // as they were crossed during the lookup, meaning we matched the guarantee
5942  * // of the locked variant
5943  * return (tvp);
5944  *
5945  * The API contract for VOP_FPLOOKUP_VEXEC routines is as follows:
5946  * - they are called while within vfs_smr protection which they must never exit
5947  * - EAGAIN can be returned to denote checking could not be performed, it is
5948  *   always valid to return it
5949  * - if the sequence counter has not changed the result must be valid
5950  * - if the sequence counter has changed both false positives and false negatives
5951  *   are permitted (since the result will be rejected later)
5952  * - for simple cases of unix permission checks vaccess_vexec_smr can be used
5953  *
5954  * Caveats to watch out for:
5955  * - vnodes are passed unlocked and unreferenced with nothing stopping
5956  *   VOP_RECLAIM, in turn meaning that ->v_data can become NULL. It is advised
5957  *   to use atomic_load_ptr to fetch it.
5958  * - the aforementioned object can also get freed, meaning absent other means it
5959  *   should be protected with vfs_smr
5960  * - either safely checking permissions as they are modified or guaranteeing
5961  *   their stability is left to the routine
5962  */
5963 int
5964 cache_fplookup(struct nameidata *ndp, enum cache_fpl_status *status,
5965     struct pwd **pwdp)
5966 {
5967 	struct cache_fpl fpl;
5968 	struct pwd *pwd;
5969 	struct vnode *dvp;
5970 	struct componentname *cnp;
5971 	int error;
5972 
5973 	fpl.status = CACHE_FPL_STATUS_UNSET;
5974 	fpl.in_smr = false;
5975 	fpl.ndp = ndp;
5976 	fpl.cnp = cnp = &ndp->ni_cnd;
5977 	MPASS(ndp->ni_lcf == 0);
5978 	MPASS(curthread == cnp->cn_thread);
5979 	KASSERT ((cnp->cn_flags & CACHE_FPL_INTERNAL_CN_FLAGS) == 0,
5980 	    ("%s: internal flags found in cn_flags %" PRIx64, __func__,
5981 	    cnp->cn_flags));
5982 	if ((cnp->cn_flags & SAVESTART) != 0) {
5983 		MPASS(cnp->cn_nameiop != LOOKUP);
5984 	}
5985 	MPASS(cnp->cn_nameptr == cnp->cn_pnbuf);
5986 
5987 	if (__predict_false(!cache_can_fplookup(&fpl))) {
5988 		*status = fpl.status;
5989 		SDT_PROBE3(vfs, fplookup, lookup, done, ndp, fpl.line, fpl.status);
5990 		return (EOPNOTSUPP);
5991 	}
5992 
5993 	cache_fpl_checkpoint_outer(&fpl);
5994 
5995 	cache_fpl_smr_enter_initial(&fpl);
5996 #ifdef INVARIANTS
5997 	fpl.debug.ni_pathlen = ndp->ni_pathlen;
5998 #endif
5999 	fpl.nulchar = &cnp->cn_nameptr[ndp->ni_pathlen - 1];
6000 	fpl.fsearch = false;
6001 	fpl.savename = (cnp->cn_flags & SAVENAME) != 0;
6002 	fpl.tvp = NULL; /* for degenerate path handling */
6003 	fpl.pwd = pwdp;
6004 	pwd = pwd_get_smr();
6005 	*(fpl.pwd) = pwd;
6006 	ndp->ni_rootdir = pwd->pwd_rdir;
6007 	ndp->ni_topdir = pwd->pwd_jdir;
6008 
6009 	if (cnp->cn_pnbuf[0] == '/') {
6010 		dvp = cache_fpl_handle_root(&fpl);
6011 		MPASS(ndp->ni_resflags == 0);
6012 		ndp->ni_resflags = NIRES_ABS;
6013 	} else {
6014 		if (ndp->ni_dirfd == AT_FDCWD) {
6015 			dvp = pwd->pwd_cdir;
6016 		} else {
6017 			error = cache_fplookup_dirfd(&fpl, &dvp);
6018 			if (__predict_false(error != 0)) {
6019 				goto out;
6020 			}
6021 		}
6022 	}
6023 
6024 	SDT_PROBE4(vfs, namei, lookup, entry, dvp, cnp->cn_pnbuf, cnp->cn_flags, true);
6025 	error = cache_fplookup_impl(dvp, &fpl);
6026 out:
6027 	cache_fpl_smr_assert_not_entered(&fpl);
6028 	cache_fpl_assert_status(&fpl);
6029 	*status = fpl.status;
6030 	if (SDT_PROBES_ENABLED()) {
6031 		SDT_PROBE3(vfs, fplookup, lookup, done, ndp, fpl.line, fpl.status);
6032 		if (fpl.status == CACHE_FPL_STATUS_HANDLED)
6033 			SDT_PROBE4(vfs, namei, lookup, return, error, ndp->ni_vp, true,
6034 			    ndp);
6035 	}
6036 
6037 	if (__predict_true(fpl.status == CACHE_FPL_STATUS_HANDLED)) {
6038 		MPASS(error != CACHE_FPL_FAILED);
6039 		if (error != 0) {
6040 			MPASS(fpl.dvp == NULL);
6041 			MPASS(fpl.tvp == NULL);
6042 			MPASS(fpl.savename == false);
6043 		}
6044 		ndp->ni_dvp = fpl.dvp;
6045 		ndp->ni_vp = fpl.tvp;
6046 		if (fpl.savename) {
6047 			cnp->cn_flags |= HASBUF;
6048 		} else {
6049 			cache_fpl_cleanup_cnp(cnp);
6050 		}
6051 	}
6052 	return (error);
6053 }
6054