xref: /linux/include/linux/dcache.h (revision dc99c0ff)
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