1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef __LINUX_DCACHE_H
3 #define __LINUX_DCACHE_H
4
5 #include <linux/atomic.h>
6 #include <linux/list.h>
7 #include <linux/math.h>
8 #include <linux/rculist.h>
9 #include <linux/rculist_bl.h>
10 #include <linux/spinlock.h>
11 #include <linux/seqlock.h>
12 #include <linux/cache.h>
13 #include <linux/rcupdate.h>
14 #include <linux/lockref.h>
15 #include <linux/stringhash.h>
16 #include <linux/wait.h>
17
18 struct path;
19 struct file;
20 struct vfsmount;
21
22 /*
23 * linux/include/linux/dcache.h
24 *
25 * Dirent cache data structures
26 *
27 * (C) Copyright 1997 Thomas Schoebel-Theuer,
28 * with heavy changes by Linus Torvalds
29 */
30
31 #define IS_ROOT(x) ((x) == (x)->d_parent)
32
33 /* The hash is always the low bits of hash_len */
34 #ifdef __LITTLE_ENDIAN
35 #define HASH_LEN_DECLARE u32 hash; u32 len
36 #define bytemask_from_count(cnt) (~(~0ul << (cnt)*8))
37 #else
38 #define HASH_LEN_DECLARE u32 len; u32 hash
39 #define bytemask_from_count(cnt) (~(~0ul >> (cnt)*8))
40 #endif
41
42 /*
43 * "quick string" -- eases parameter passing, but more importantly
44 * saves "metadata" about the string (ie length and the hash).
45 *
46 * hash comes first so it snuggles against d_parent in the
47 * dentry.
48 */
49 struct qstr {
50 union {
51 struct {
52 HASH_LEN_DECLARE;
53 };
54 u64 hash_len;
55 };
56 const unsigned char *name;
57 };
58
59 #define QSTR_INIT(n,l) { { { .len = l } }, .name = n }
60
61 extern const struct qstr empty_name;
62 extern const struct qstr slash_name;
63 extern const struct qstr dotdot_name;
64
65 /*
66 * Try to keep struct dentry aligned on 64 byte cachelines (this will
67 * give reasonable cacheline footprint with larger lines without the
68 * large memory footprint increase).
69 */
70 #ifdef CONFIG_64BIT
71 # define DNAME_INLINE_LEN 40 /* 192 bytes */
72 #else
73 # ifdef CONFIG_SMP
74 # define DNAME_INLINE_LEN 36 /* 128 bytes */
75 # else
76 # define DNAME_INLINE_LEN 44 /* 128 bytes */
77 # endif
78 #endif
79
80 #define d_lock d_lockref.lock
81
82 struct dentry {
83 /* RCU lookup touched fields */
84 unsigned int d_flags; /* protected by d_lock */
85 seqcount_spinlock_t d_seq; /* per dentry seqlock */
86 struct hlist_bl_node d_hash; /* lookup hash list */
87 struct dentry *d_parent; /* parent directory */
88 struct qstr d_name;
89 struct inode *d_inode; /* Where the name belongs to - NULL is
90 * negative */
91 unsigned char d_iname[DNAME_INLINE_LEN]; /* small names */
92 /* --- cacheline 1 boundary (64 bytes) was 32 bytes ago --- */
93
94 /* Ref lookup also touches following */
95 const struct dentry_operations *d_op;
96 struct super_block *d_sb; /* The root of the dentry tree */
97 unsigned long d_time; /* used by d_revalidate */
98 void *d_fsdata; /* fs-specific data */
99 /* --- cacheline 2 boundary (128 bytes) --- */
100 struct lockref d_lockref; /* per-dentry lock and refcount
101 * keep separate from RCU lookup area if
102 * possible!
103 */
104
105 union {
106 struct list_head d_lru; /* LRU list */
107 wait_queue_head_t *d_wait; /* in-lookup ones only */
108 };
109 struct hlist_node d_sib; /* child of parent list */
110 struct hlist_head d_children; /* our children */
111 /*
112 * d_alias and d_rcu can share memory
113 */
114 union {
115 struct hlist_node d_alias; /* inode alias list */
116 struct hlist_bl_node d_in_lookup_hash; /* only for in-lookup ones */
117 struct rcu_head d_rcu;
118 } d_u;
119 };
120
121 /*
122 * dentry->d_lock spinlock nesting subclasses:
123 *
124 * 0: normal
125 * 1: nested
126 */
127 enum dentry_d_lock_class
128 {
129 DENTRY_D_LOCK_NORMAL, /* implicitly used by plain spin_lock() APIs. */
130 DENTRY_D_LOCK_NESTED
131 };
132
133 enum d_real_type {
134 D_REAL_DATA,
135 D_REAL_METADATA,
136 };
137
138 struct dentry_operations {
139 int (*d_revalidate)(struct dentry *, unsigned int);
140 int (*d_weak_revalidate)(struct dentry *, unsigned int);
141 int (*d_hash)(const struct dentry *, struct qstr *);
142 int (*d_compare)(const struct dentry *,
143 unsigned int, const char *, const struct qstr *);
144 int (*d_delete)(const struct dentry *);
145 int (*d_init)(struct dentry *);
146 void (*d_release)(struct dentry *);
147 void (*d_prune)(struct dentry *);
148 void (*d_iput)(struct dentry *, struct inode *);
149 char *(*d_dname)(struct dentry *, char *, int);
150 struct vfsmount *(*d_automount)(struct path *);
151 int (*d_manage)(const struct path *, bool);
152 struct dentry *(*d_real)(struct dentry *, enum d_real_type type);
153 } ____cacheline_aligned;
154
155 /*
156 * Locking rules for dentry_operations callbacks are to be found in
157 * Documentation/filesystems/locking.rst. Keep it updated!
158 *
159 * FUrther descriptions are found in Documentation/filesystems/vfs.rst.
160 * Keep it updated too!
161 */
162
163 /* d_flags entries */
164 #define DCACHE_OP_HASH BIT(0)
165 #define DCACHE_OP_COMPARE BIT(1)
166 #define DCACHE_OP_REVALIDATE BIT(2)
167 #define DCACHE_OP_DELETE BIT(3)
168 #define DCACHE_OP_PRUNE BIT(4)
169
170 #define DCACHE_DISCONNECTED BIT(5)
171 /* This dentry is possibly not currently connected to the dcache tree, in
172 * which case its parent will either be itself, or will have this flag as
173 * well. nfsd will not use a dentry with this bit set, but will first
174 * endeavour to clear the bit either by discovering that it is connected,
175 * or by performing lookup operations. Any filesystem which supports
176 * nfsd_operations MUST have a lookup function which, if it finds a
177 * directory inode with a DCACHE_DISCONNECTED dentry, will d_move that
178 * dentry into place and return that dentry rather than the passed one,
179 * typically using d_splice_alias. */
180
181 #define DCACHE_REFERENCED BIT(6) /* Recently used, don't discard. */
182
183 #define DCACHE_DONTCACHE BIT(7) /* Purge from memory on final dput() */
184
185 #define DCACHE_CANT_MOUNT BIT(8)
186 #define DCACHE_GENOCIDE BIT(9)
187 #define DCACHE_SHRINK_LIST BIT(10)
188
189 #define DCACHE_OP_WEAK_REVALIDATE BIT(11)
190
191 #define DCACHE_NFSFS_RENAMED BIT(12)
192 /* this dentry has been "silly renamed" and has to be deleted on the last
193 * dput() */
194 #define DCACHE_FSNOTIFY_PARENT_WATCHED BIT(14)
195 /* Parent inode is watched by some fsnotify listener */
196
197 #define DCACHE_DENTRY_KILLED BIT(15)
198
199 #define DCACHE_MOUNTED BIT(16) /* is a mountpoint */
200 #define DCACHE_NEED_AUTOMOUNT BIT(17) /* handle automount on this dir */
201 #define DCACHE_MANAGE_TRANSIT BIT(18) /* manage transit from this dirent */
202 #define DCACHE_MANAGED_DENTRY \
203 (DCACHE_MOUNTED|DCACHE_NEED_AUTOMOUNT|DCACHE_MANAGE_TRANSIT)
204
205 #define DCACHE_LRU_LIST BIT(19)
206
207 #define DCACHE_ENTRY_TYPE (7 << 20) /* bits 20..22 are for storing type: */
208 #define DCACHE_MISS_TYPE (0 << 20) /* Negative dentry */
209 #define DCACHE_WHITEOUT_TYPE (1 << 20) /* Whiteout dentry (stop pathwalk) */
210 #define DCACHE_DIRECTORY_TYPE (2 << 20) /* Normal directory */
211 #define DCACHE_AUTODIR_TYPE (3 << 20) /* Lookupless directory (presumed automount) */
212 #define DCACHE_REGULAR_TYPE (4 << 20) /* Regular file type */
213 #define DCACHE_SPECIAL_TYPE (5 << 20) /* Other file type */
214 #define DCACHE_SYMLINK_TYPE (6 << 20) /* Symlink */
215
216 #define DCACHE_NOKEY_NAME BIT(25) /* Encrypted name encoded without key */
217 #define DCACHE_OP_REAL BIT(26)
218
219 #define DCACHE_PAR_LOOKUP BIT(28) /* being looked up (with parent locked shared) */
220 #define DCACHE_DENTRY_CURSOR BIT(29)
221 #define DCACHE_NORCU BIT(30) /* No RCU delay for freeing */
222
223 extern seqlock_t rename_lock;
224
225 /*
226 * These are the low-level FS interfaces to the dcache..
227 */
228 extern void d_instantiate(struct dentry *, struct inode *);
229 extern void d_instantiate_new(struct dentry *, struct inode *);
230 extern void __d_drop(struct dentry *dentry);
231 extern void d_drop(struct dentry *dentry);
232 extern void d_delete(struct dentry *);
233 extern void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op);
234
235 /* allocate/de-allocate */
236 extern struct dentry * d_alloc(struct dentry *, const struct qstr *);
237 extern struct dentry * d_alloc_anon(struct super_block *);
238 extern struct dentry * d_alloc_parallel(struct dentry *, const struct qstr *,
239 wait_queue_head_t *);
240 extern struct dentry * d_splice_alias(struct inode *, struct dentry *);
241 extern struct dentry * d_add_ci(struct dentry *, struct inode *, struct qstr *);
242 extern bool d_same_name(const struct dentry *dentry, const struct dentry *parent,
243 const struct qstr *name);
244 extern struct dentry * d_exact_alias(struct dentry *, struct inode *);
245 extern struct dentry *d_find_any_alias(struct inode *inode);
246 extern struct dentry * d_obtain_alias(struct inode *);
247 extern struct dentry * d_obtain_root(struct inode *);
248 extern void shrink_dcache_sb(struct super_block *);
249 extern void shrink_dcache_parent(struct dentry *);
250 extern void d_invalidate(struct dentry *);
251
252 /* only used at mount-time */
253 extern struct dentry * d_make_root(struct inode *);
254
255 extern void d_mark_tmpfile(struct file *, struct inode *);
256 extern void d_tmpfile(struct file *, struct inode *);
257
258 extern struct dentry *d_find_alias(struct inode *);
259 extern void d_prune_aliases(struct inode *);
260
261 extern struct dentry *d_find_alias_rcu(struct inode *);
262
263 /* test whether we have any submounts in a subdir tree */
264 extern int path_has_submounts(const struct path *);
265
266 /*
267 * This adds the entry to the hash queues.
268 */
269 extern void d_rehash(struct dentry *);
270
271 extern void d_add(struct dentry *, struct inode *);
272
273 /* used for rename() and baskets */
274 extern void d_move(struct dentry *, struct dentry *);
275 extern void d_exchange(struct dentry *, struct dentry *);
276 extern struct dentry *d_ancestor(struct dentry *, struct dentry *);
277
278 extern struct dentry *d_lookup(const struct dentry *, const struct qstr *);
279 extern struct dentry *d_hash_and_lookup(struct dentry *, struct qstr *);
280
d_count(const struct dentry * dentry)281 static inline unsigned d_count(const struct dentry *dentry)
282 {
283 return dentry->d_lockref.count;
284 }
285
286 ino_t d_parent_ino(struct dentry *dentry);
287
288 /*
289 * helper function for dentry_operations.d_dname() members
290 */
291 extern __printf(3, 4)
292 char *dynamic_dname(char *, int, const char *, ...);
293
294 extern char *__d_path(const struct path *, const struct path *, char *, int);
295 extern char *d_absolute_path(const struct path *, char *, int);
296 extern char *d_path(const struct path *, char *, int);
297 extern char *dentry_path_raw(const struct dentry *, char *, int);
298 extern char *dentry_path(const struct dentry *, char *, int);
299
300 /* Allocation counts.. */
301
302 /**
303 * dget_dlock - get a reference to a dentry
304 * @dentry: dentry to get a reference to
305 *
306 * Given a live dentry, increment the reference count and return the dentry.
307 * Caller must hold @dentry->d_lock. Making sure that dentry is alive is
308 * caller's resonsibility. There are many conditions sufficient to guarantee
309 * that; e.g. anything with non-negative refcount is alive, so's anything
310 * hashed, anything positive, anyone's parent, etc.
311 */
dget_dlock(struct dentry * dentry)312 static inline struct dentry *dget_dlock(struct dentry *dentry)
313 {
314 dentry->d_lockref.count++;
315 return dentry;
316 }
317
318
319 /**
320 * dget - get a reference to a dentry
321 * @dentry: dentry to get a reference to
322 *
323 * Given a dentry or %NULL pointer increment the reference count
324 * if appropriate and return the dentry. A dentry will not be
325 * destroyed when it has references. Conversely, a dentry with
326 * no references can disappear for any number of reasons, starting
327 * with memory pressure. In other words, that primitive is
328 * used to clone an existing reference; using it on something with
329 * zero refcount is a bug.
330 *
331 * NOTE: it will spin if @dentry->d_lock is held. From the deadlock
332 * avoidance point of view it is equivalent to spin_lock()/increment
333 * refcount/spin_unlock(), so calling it under @dentry->d_lock is
334 * always a bug; so's calling it under ->d_lock on any of its descendents.
335 *
336 */
dget(struct dentry * dentry)337 static inline struct dentry *dget(struct dentry *dentry)
338 {
339 if (dentry)
340 lockref_get(&dentry->d_lockref);
341 return dentry;
342 }
343
344 extern struct dentry *dget_parent(struct dentry *dentry);
345
346 /**
347 * d_unhashed - is dentry hashed
348 * @dentry: entry to check
349 *
350 * Returns true if the dentry passed is not currently hashed.
351 */
d_unhashed(const struct dentry * dentry)352 static inline int d_unhashed(const struct dentry *dentry)
353 {
354 return hlist_bl_unhashed(&dentry->d_hash);
355 }
356
d_unlinked(const struct dentry * dentry)357 static inline int d_unlinked(const struct dentry *dentry)
358 {
359 return d_unhashed(dentry) && !IS_ROOT(dentry);
360 }
361
cant_mount(const struct dentry * dentry)362 static inline int cant_mount(const struct dentry *dentry)
363 {
364 return (dentry->d_flags & DCACHE_CANT_MOUNT);
365 }
366
dont_mount(struct dentry * dentry)367 static inline void dont_mount(struct dentry *dentry)
368 {
369 spin_lock(&dentry->d_lock);
370 dentry->d_flags |= DCACHE_CANT_MOUNT;
371 spin_unlock(&dentry->d_lock);
372 }
373
374 extern void __d_lookup_unhash_wake(struct dentry *dentry);
375
d_in_lookup(const struct dentry * dentry)376 static inline int d_in_lookup(const struct dentry *dentry)
377 {
378 return dentry->d_flags & DCACHE_PAR_LOOKUP;
379 }
380
d_lookup_done(struct dentry * dentry)381 static inline void d_lookup_done(struct dentry *dentry)
382 {
383 if (unlikely(d_in_lookup(dentry)))
384 __d_lookup_unhash_wake(dentry);
385 }
386
387 extern void dput(struct dentry *);
388
d_managed(const struct dentry * dentry)389 static inline bool d_managed(const struct dentry *dentry)
390 {
391 return dentry->d_flags & DCACHE_MANAGED_DENTRY;
392 }
393
d_mountpoint(const struct dentry * dentry)394 static inline bool d_mountpoint(const struct dentry *dentry)
395 {
396 return dentry->d_flags & DCACHE_MOUNTED;
397 }
398
399 /*
400 * Directory cache entry type accessor functions.
401 */
__d_entry_type(const struct dentry * dentry)402 static inline unsigned __d_entry_type(const struct dentry *dentry)
403 {
404 return dentry->d_flags & DCACHE_ENTRY_TYPE;
405 }
406
d_is_miss(const struct dentry * dentry)407 static inline bool d_is_miss(const struct dentry *dentry)
408 {
409 return __d_entry_type(dentry) == DCACHE_MISS_TYPE;
410 }
411
d_is_whiteout(const struct dentry * dentry)412 static inline bool d_is_whiteout(const struct dentry *dentry)
413 {
414 return __d_entry_type(dentry) == DCACHE_WHITEOUT_TYPE;
415 }
416
d_can_lookup(const struct dentry * dentry)417 static inline bool d_can_lookup(const struct dentry *dentry)
418 {
419 return __d_entry_type(dentry) == DCACHE_DIRECTORY_TYPE;
420 }
421
d_is_autodir(const struct dentry * dentry)422 static inline bool d_is_autodir(const struct dentry *dentry)
423 {
424 return __d_entry_type(dentry) == DCACHE_AUTODIR_TYPE;
425 }
426
d_is_dir(const struct dentry * dentry)427 static inline bool d_is_dir(const struct dentry *dentry)
428 {
429 return d_can_lookup(dentry) || d_is_autodir(dentry);
430 }
431
d_is_symlink(const struct dentry * dentry)432 static inline bool d_is_symlink(const struct dentry *dentry)
433 {
434 return __d_entry_type(dentry) == DCACHE_SYMLINK_TYPE;
435 }
436
d_is_reg(const struct dentry * dentry)437 static inline bool d_is_reg(const struct dentry *dentry)
438 {
439 return __d_entry_type(dentry) == DCACHE_REGULAR_TYPE;
440 }
441
d_is_special(const struct dentry * dentry)442 static inline bool d_is_special(const struct dentry *dentry)
443 {
444 return __d_entry_type(dentry) == DCACHE_SPECIAL_TYPE;
445 }
446
d_is_file(const struct dentry * dentry)447 static inline bool d_is_file(const struct dentry *dentry)
448 {
449 return d_is_reg(dentry) || d_is_special(dentry);
450 }
451
d_is_negative(const struct dentry * dentry)452 static inline bool d_is_negative(const struct dentry *dentry)
453 {
454 // TODO: check d_is_whiteout(dentry) also.
455 return d_is_miss(dentry);
456 }
457
d_flags_negative(unsigned flags)458 static inline bool d_flags_negative(unsigned flags)
459 {
460 return (flags & DCACHE_ENTRY_TYPE) == DCACHE_MISS_TYPE;
461 }
462
d_is_positive(const struct dentry * dentry)463 static inline bool d_is_positive(const struct dentry *dentry)
464 {
465 return !d_is_negative(dentry);
466 }
467
468 /**
469 * d_really_is_negative - Determine if a dentry is really negative (ignoring fallthroughs)
470 * @dentry: The dentry in question
471 *
472 * Returns true if the dentry represents either an absent name or a name that
473 * doesn't map to an inode (ie. ->d_inode is NULL). The dentry could represent
474 * a true miss, a whiteout that isn't represented by a 0,0 chardev or a
475 * fallthrough marker in an opaque directory.
476 *
477 * Note! (1) This should be used *only* by a filesystem to examine its own
478 * dentries. It should not be used to look at some other filesystem's
479 * dentries. (2) It should also be used in combination with d_inode() to get
480 * the inode. (3) The dentry may have something attached to ->d_lower and the
481 * type field of the flags may be set to something other than miss or whiteout.
482 */
d_really_is_negative(const struct dentry * dentry)483 static inline bool d_really_is_negative(const struct dentry *dentry)
484 {
485 return dentry->d_inode == NULL;
486 }
487
488 /**
489 * d_really_is_positive - Determine if a dentry is really positive (ignoring fallthroughs)
490 * @dentry: The dentry in question
491 *
492 * Returns true if the dentry represents a name that maps to an inode
493 * (ie. ->d_inode is not NULL). The dentry might still represent a whiteout if
494 * that is represented on medium as a 0,0 chardev.
495 *
496 * Note! (1) This should be used *only* by a filesystem to examine its own
497 * dentries. It should not be used to look at some other filesystem's
498 * dentries. (2) It should also be used in combination with d_inode() to get
499 * the inode.
500 */
d_really_is_positive(const struct dentry * dentry)501 static inline bool d_really_is_positive(const struct dentry *dentry)
502 {
503 return dentry->d_inode != NULL;
504 }
505
simple_positive(const struct dentry * dentry)506 static inline int simple_positive(const struct dentry *dentry)
507 {
508 return d_really_is_positive(dentry) && !d_unhashed(dentry);
509 }
510
511 extern int sysctl_vfs_cache_pressure;
512
vfs_pressure_ratio(unsigned long val)513 static inline unsigned long vfs_pressure_ratio(unsigned long val)
514 {
515 return mult_frac(val, sysctl_vfs_cache_pressure, 100);
516 }
517
518 /**
519 * d_inode - Get the actual inode of this dentry
520 * @dentry: The dentry to query
521 *
522 * This is the helper normal filesystems should use to get at their own inodes
523 * in their own dentries and ignore the layering superimposed upon them.
524 */
d_inode(const struct dentry * dentry)525 static inline struct inode *d_inode(const struct dentry *dentry)
526 {
527 return dentry->d_inode;
528 }
529
530 /**
531 * d_inode_rcu - Get the actual inode of this dentry with READ_ONCE()
532 * @dentry: The dentry to query
533 *
534 * This is the helper normal filesystems should use to get at their own inodes
535 * in their own dentries and ignore the layering superimposed upon them.
536 */
d_inode_rcu(const struct dentry * dentry)537 static inline struct inode *d_inode_rcu(const struct dentry *dentry)
538 {
539 return READ_ONCE(dentry->d_inode);
540 }
541
542 /**
543 * d_backing_inode - Get upper or lower inode we should be using
544 * @upper: The upper layer
545 *
546 * This is the helper that should be used to get at the inode that will be used
547 * if this dentry were to be opened as a file. The inode may be on the upper
548 * dentry or it may be on a lower dentry pinned by the upper.
549 *
550 * Normal filesystems should not use this to access their own inodes.
551 */
d_backing_inode(const struct dentry * upper)552 static inline struct inode *d_backing_inode(const struct dentry *upper)
553 {
554 struct inode *inode = upper->d_inode;
555
556 return inode;
557 }
558
559 /**
560 * d_real - Return the real dentry
561 * @dentry: the dentry to query
562 * @type: the type of real dentry (data or metadata)
563 *
564 * If dentry is on a union/overlay, then return the underlying, real dentry.
565 * Otherwise return the dentry itself.
566 *
567 * See also: Documentation/filesystems/vfs.rst
568 */
d_real(struct dentry * dentry,enum d_real_type type)569 static inline struct dentry *d_real(struct dentry *dentry, enum d_real_type type)
570 {
571 if (unlikely(dentry->d_flags & DCACHE_OP_REAL))
572 return dentry->d_op->d_real(dentry, type);
573 else
574 return dentry;
575 }
576
577 /**
578 * d_real_inode - Return the real inode hosting the data
579 * @dentry: The dentry to query
580 *
581 * If dentry is on a union/overlay, then return the underlying, real inode.
582 * Otherwise return d_inode().
583 */
d_real_inode(const struct dentry * dentry)584 static inline struct inode *d_real_inode(const struct dentry *dentry)
585 {
586 /* This usage of d_real() results in const dentry */
587 return d_inode(d_real((struct dentry *) dentry, D_REAL_DATA));
588 }
589
590 struct name_snapshot {
591 struct qstr name;
592 unsigned char inline_name[DNAME_INLINE_LEN];
593 };
594 void take_dentry_name_snapshot(struct name_snapshot *, struct dentry *);
595 void release_dentry_name_snapshot(struct name_snapshot *);
596
d_first_child(const struct dentry * dentry)597 static inline struct dentry *d_first_child(const struct dentry *dentry)
598 {
599 return hlist_entry_safe(dentry->d_children.first, struct dentry, d_sib);
600 }
601
d_next_sibling(const struct dentry * dentry)602 static inline struct dentry *d_next_sibling(const struct dentry *dentry)
603 {
604 return hlist_entry_safe(dentry->d_sib.next, struct dentry, d_sib);
605 }
606
607 #endif /* __LINUX_DCACHE_H */
608