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 32 /* 192 bytes */
72 #else
73 # ifdef CONFIG_SMP
74 #  define DNAME_INLINE_LEN 36 /* 128 bytes */
75 # else
76 #  define DNAME_INLINE_LEN 40 /* 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 
93 	/* Ref lookup also touches following */
94 	struct lockref d_lockref;	/* per-dentry lock and refcount */
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 
100 	union {
101 		struct list_head d_lru;		/* LRU list */
102 		wait_queue_head_t *d_wait;	/* in-lookup ones only */
103 	};
104 	struct list_head d_child;	/* child of parent list */
105 	struct list_head d_subdirs;	/* our children */
106 	/*
107 	 * d_alias and d_rcu can share memory
108 	 */
109 	union {
110 		struct hlist_node d_alias;	/* inode alias list */
111 		struct hlist_bl_node d_in_lookup_hash;	/* only for in-lookup ones */
112 	 	struct rcu_head d_rcu;
113 	} d_u;
114 } __randomize_layout;
115 
116 /*
117  * dentry->d_lock spinlock nesting subclasses:
118  *
119  * 0: normal
120  * 1: nested
121  */
122 enum dentry_d_lock_class
123 {
124 	DENTRY_D_LOCK_NORMAL, /* implicitly used by plain spin_lock() APIs. */
125 	DENTRY_D_LOCK_NESTED
126 };
127 
128 struct dentry_operations {
129 	int (*d_revalidate)(struct dentry *, unsigned int);
130 	int (*d_weak_revalidate)(struct dentry *, unsigned int);
131 	int (*d_hash)(const struct dentry *, struct qstr *);
132 	int (*d_compare)(const struct dentry *,
133 			unsigned int, const char *, const struct qstr *);
134 	int (*d_delete)(const struct dentry *);
135 	int (*d_init)(struct dentry *);
136 	void (*d_release)(struct dentry *);
137 	void (*d_prune)(struct dentry *);
138 	void (*d_iput)(struct dentry *, struct inode *);
139 	char *(*d_dname)(struct dentry *, char *, int);
140 	struct vfsmount *(*d_automount)(struct path *);
141 	int (*d_manage)(const struct path *, bool);
142 	struct dentry *(*d_real)(struct dentry *, const struct inode *);
143 } ____cacheline_aligned;
144 
145 /*
146  * Locking rules for dentry_operations callbacks are to be found in
147  * Documentation/filesystems/locking.rst. Keep it updated!
148  *
149  * FUrther descriptions are found in Documentation/filesystems/vfs.rst.
150  * Keep it updated too!
151  */
152 
153 /* d_flags entries */
154 #define DCACHE_OP_HASH			0x00000001
155 #define DCACHE_OP_COMPARE		0x00000002
156 #define DCACHE_OP_REVALIDATE		0x00000004
157 #define DCACHE_OP_DELETE		0x00000008
158 #define DCACHE_OP_PRUNE			0x00000010
159 
160 #define	DCACHE_DISCONNECTED		0x00000020
161      /* This dentry is possibly not currently connected to the dcache tree, in
162       * which case its parent will either be itself, or will have this flag as
163       * well.  nfsd will not use a dentry with this bit set, but will first
164       * endeavour to clear the bit either by discovering that it is connected,
165       * or by performing lookup operations.   Any filesystem which supports
166       * nfsd_operations MUST have a lookup function which, if it finds a
167       * directory inode with a DCACHE_DISCONNECTED dentry, will d_move that
168       * dentry into place and return that dentry rather than the passed one,
169       * typically using d_splice_alias. */
170 
171 #define DCACHE_REFERENCED		0x00000040 /* Recently used, don't discard. */
172 
173 #define DCACHE_DONTCACHE		0x00000080 /* Purge from memory on final dput() */
174 
175 #define DCACHE_CANT_MOUNT		0x00000100
176 #define DCACHE_GENOCIDE			0x00000200
177 #define DCACHE_SHRINK_LIST		0x00000400
178 
179 #define DCACHE_OP_WEAK_REVALIDATE	0x00000800
180 
181 #define DCACHE_NFSFS_RENAMED		0x00001000
182      /* this dentry has been "silly renamed" and has to be deleted on the last
183       * dput() */
184 #define DCACHE_COOKIE			0x00002000 /* For use by dcookie subsystem */
185 #define DCACHE_FSNOTIFY_PARENT_WATCHED	0x00004000
186      /* Parent inode is watched by some fsnotify listener */
187 
188 #define DCACHE_DENTRY_KILLED		0x00008000
189 
190 #define DCACHE_MOUNTED			0x00010000 /* is a mountpoint */
191 #define DCACHE_NEED_AUTOMOUNT		0x00020000 /* handle automount on this dir */
192 #define DCACHE_MANAGE_TRANSIT		0x00040000 /* manage transit from this dirent */
193 #define DCACHE_MANAGED_DENTRY \
194 	(DCACHE_MOUNTED|DCACHE_NEED_AUTOMOUNT|DCACHE_MANAGE_TRANSIT)
195 
196 #define DCACHE_LRU_LIST			0x00080000
197 
198 #define DCACHE_ENTRY_TYPE		0x00700000
199 #define DCACHE_MISS_TYPE		0x00000000 /* Negative dentry (maybe fallthru to nowhere) */
200 #define DCACHE_WHITEOUT_TYPE		0x00100000 /* Whiteout dentry (stop pathwalk) */
201 #define DCACHE_DIRECTORY_TYPE		0x00200000 /* Normal directory */
202 #define DCACHE_AUTODIR_TYPE		0x00300000 /* Lookupless directory (presumed automount) */
203 #define DCACHE_REGULAR_TYPE		0x00400000 /* Regular file type (or fallthru to such) */
204 #define DCACHE_SPECIAL_TYPE		0x00500000 /* Other file type (or fallthru to such) */
205 #define DCACHE_SYMLINK_TYPE		0x00600000 /* Symlink (or fallthru to such) */
206 
207 #define DCACHE_MAY_FREE			0x00800000
208 #define DCACHE_FALLTHRU			0x01000000 /* Fall through to lower layer */
209 #define DCACHE_NOKEY_NAME		0x02000000 /* Encrypted name encoded without key */
210 #define DCACHE_OP_REAL			0x04000000
211 
212 #define DCACHE_PAR_LOOKUP		0x10000000 /* being looked up (with parent locked shared) */
213 #define DCACHE_DENTRY_CURSOR		0x20000000
214 #define DCACHE_NORCU			0x40000000 /* No RCU delay for freeing */
215 
216 extern seqlock_t rename_lock;
217 
218 /*
219  * These are the low-level FS interfaces to the dcache..
220  */
221 extern void d_instantiate(struct dentry *, struct inode *);
222 extern void d_instantiate_new(struct dentry *, struct inode *);
223 extern struct dentry * d_instantiate_unique(struct dentry *, struct inode *);
224 extern struct dentry * d_instantiate_anon(struct dentry *, struct inode *);
225 extern void __d_drop(struct dentry *dentry);
226 extern void d_drop(struct dentry *dentry);
227 extern void d_delete(struct dentry *);
228 extern void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op);
229 
230 /* allocate/de-allocate */
231 extern struct dentry * d_alloc(struct dentry *, const struct qstr *);
232 extern struct dentry * d_alloc_anon(struct super_block *);
233 extern struct dentry * d_alloc_parallel(struct dentry *, const struct qstr *,
234 					wait_queue_head_t *);
235 extern struct dentry * d_splice_alias(struct inode *, struct dentry *);
236 extern struct dentry * d_add_ci(struct dentry *, struct inode *, struct qstr *);
237 extern bool d_same_name(const struct dentry *dentry, const struct dentry *parent,
238 			const struct qstr *name);
239 extern struct dentry * d_exact_alias(struct dentry *, struct inode *);
240 extern struct dentry *d_find_any_alias(struct inode *inode);
241 extern struct dentry * d_obtain_alias(struct inode *);
242 extern struct dentry * d_obtain_root(struct inode *);
243 extern void shrink_dcache_sb(struct super_block *);
244 extern void shrink_dcache_parent(struct dentry *);
245 extern void shrink_dcache_for_umount(struct super_block *);
246 extern void d_invalidate(struct dentry *);
247 
248 /* only used at mount-time */
249 extern struct dentry * d_make_root(struct inode *);
250 
251 /* <clickety>-<click> the ramfs-type tree */
252 extern void d_genocide(struct dentry *);
253 
254 extern void d_tmpfile(struct file *, struct inode *);
255 
256 extern struct dentry *d_find_alias(struct inode *);
257 extern void d_prune_aliases(struct inode *);
258 
259 extern struct dentry *d_find_alias_rcu(struct inode *);
260 
261 /* test whether we have any submounts in a subdir tree */
262 extern int path_has_submounts(const struct path *);
263 
264 /*
265  * This adds the entry to the hash queues.
266  */
267 extern void d_rehash(struct dentry *);
268 
269 extern void d_add(struct dentry *, struct inode *);
270 
271 /* used for rename() and baskets */
272 extern void d_move(struct dentry *, struct dentry *);
273 extern void d_exchange(struct dentry *, struct dentry *);
274 extern struct dentry *d_ancestor(struct dentry *, struct dentry *);
275 
276 /* appendix may either be NULL or be used for transname suffixes */
277 extern struct dentry *d_lookup(const struct dentry *, const struct qstr *);
278 extern struct dentry *d_hash_and_lookup(struct dentry *, struct qstr *);
279 extern struct dentry *__d_lookup(const struct dentry *, const struct qstr *);
280 extern struct dentry *__d_lookup_rcu(const struct dentry *parent,
281 				const struct qstr *name, unsigned *seq);
282 
d_count(const struct dentry * dentry)283 static inline unsigned d_count(const struct dentry *dentry)
284 {
285 	return dentry->d_lockref.count;
286 }
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, dget_dlock -	get a reference to a dentry
304  *	@dentry: dentry to get a reference to
305  *
306  *	Given a dentry or %NULL pointer increment the reference count
307  *	if appropriate and return the dentry. A dentry will not be
308  *	destroyed when it has references.
309  */
dget_dlock(struct dentry * dentry)310 static inline struct dentry *dget_dlock(struct dentry *dentry)
311 {
312 	if (dentry)
313 		dentry->d_lockref.count++;
314 	return dentry;
315 }
316 
dget(struct dentry * dentry)317 static inline struct dentry *dget(struct dentry *dentry)
318 {
319 	if (dentry)
320 		lockref_get(&dentry->d_lockref);
321 	return dentry;
322 }
323 
324 extern struct dentry *dget_parent(struct dentry *dentry);
325 
326 /**
327  *	d_unhashed -	is dentry hashed
328  *	@dentry: entry to check
329  *
330  *	Returns true if the dentry passed is not currently hashed.
331  */
332 
d_unhashed(const struct dentry * dentry)333 static inline int d_unhashed(const struct dentry *dentry)
334 {
335 	return hlist_bl_unhashed(&dentry->d_hash);
336 }
337 
d_unlinked(const struct dentry * dentry)338 static inline int d_unlinked(const struct dentry *dentry)
339 {
340 	return d_unhashed(dentry) && !IS_ROOT(dentry);
341 }
342 
cant_mount(const struct dentry * dentry)343 static inline int cant_mount(const struct dentry *dentry)
344 {
345 	return (dentry->d_flags & DCACHE_CANT_MOUNT);
346 }
347 
dont_mount(struct dentry * dentry)348 static inline void dont_mount(struct dentry *dentry)
349 {
350 	spin_lock(&dentry->d_lock);
351 	dentry->d_flags |= DCACHE_CANT_MOUNT;
352 	spin_unlock(&dentry->d_lock);
353 }
354 
355 extern void __d_lookup_unhash_wake(struct dentry *dentry);
356 
d_in_lookup(const struct dentry * dentry)357 static inline int d_in_lookup(const struct dentry *dentry)
358 {
359 	return dentry->d_flags & DCACHE_PAR_LOOKUP;
360 }
361 
d_lookup_done(struct dentry * dentry)362 static inline void d_lookup_done(struct dentry *dentry)
363 {
364 	if (unlikely(d_in_lookup(dentry)))
365 		__d_lookup_unhash_wake(dentry);
366 }
367 
368 extern void dput(struct dentry *);
369 
d_managed(const struct dentry * dentry)370 static inline bool d_managed(const struct dentry *dentry)
371 {
372 	return dentry->d_flags & DCACHE_MANAGED_DENTRY;
373 }
374 
d_mountpoint(const struct dentry * dentry)375 static inline bool d_mountpoint(const struct dentry *dentry)
376 {
377 	return dentry->d_flags & DCACHE_MOUNTED;
378 }
379 
380 /*
381  * Directory cache entry type accessor functions.
382  */
__d_entry_type(const struct dentry * dentry)383 static inline unsigned __d_entry_type(const struct dentry *dentry)
384 {
385 	return dentry->d_flags & DCACHE_ENTRY_TYPE;
386 }
387 
d_is_miss(const struct dentry * dentry)388 static inline bool d_is_miss(const struct dentry *dentry)
389 {
390 	return __d_entry_type(dentry) == DCACHE_MISS_TYPE;
391 }
392 
d_is_whiteout(const struct dentry * dentry)393 static inline bool d_is_whiteout(const struct dentry *dentry)
394 {
395 	return __d_entry_type(dentry) == DCACHE_WHITEOUT_TYPE;
396 }
397 
d_can_lookup(const struct dentry * dentry)398 static inline bool d_can_lookup(const struct dentry *dentry)
399 {
400 	return __d_entry_type(dentry) == DCACHE_DIRECTORY_TYPE;
401 }
402 
d_is_autodir(const struct dentry * dentry)403 static inline bool d_is_autodir(const struct dentry *dentry)
404 {
405 	return __d_entry_type(dentry) == DCACHE_AUTODIR_TYPE;
406 }
407 
d_is_dir(const struct dentry * dentry)408 static inline bool d_is_dir(const struct dentry *dentry)
409 {
410 	return d_can_lookup(dentry) || d_is_autodir(dentry);
411 }
412 
d_is_symlink(const struct dentry * dentry)413 static inline bool d_is_symlink(const struct dentry *dentry)
414 {
415 	return __d_entry_type(dentry) == DCACHE_SYMLINK_TYPE;
416 }
417 
d_is_reg(const struct dentry * dentry)418 static inline bool d_is_reg(const struct dentry *dentry)
419 {
420 	return __d_entry_type(dentry) == DCACHE_REGULAR_TYPE;
421 }
422 
d_is_special(const struct dentry * dentry)423 static inline bool d_is_special(const struct dentry *dentry)
424 {
425 	return __d_entry_type(dentry) == DCACHE_SPECIAL_TYPE;
426 }
427 
d_is_file(const struct dentry * dentry)428 static inline bool d_is_file(const struct dentry *dentry)
429 {
430 	return d_is_reg(dentry) || d_is_special(dentry);
431 }
432 
d_is_negative(const struct dentry * dentry)433 static inline bool d_is_negative(const struct dentry *dentry)
434 {
435 	// TODO: check d_is_whiteout(dentry) also.
436 	return d_is_miss(dentry);
437 }
438 
d_flags_negative(unsigned flags)439 static inline bool d_flags_negative(unsigned flags)
440 {
441 	return (flags & DCACHE_ENTRY_TYPE) == DCACHE_MISS_TYPE;
442 }
443 
d_is_positive(const struct dentry * dentry)444 static inline bool d_is_positive(const struct dentry *dentry)
445 {
446 	return !d_is_negative(dentry);
447 }
448 
449 /**
450  * d_really_is_negative - Determine if a dentry is really negative (ignoring fallthroughs)
451  * @dentry: The dentry in question
452  *
453  * Returns true if the dentry represents either an absent name or a name that
454  * doesn't map to an inode (ie. ->d_inode is NULL).  The dentry could represent
455  * a true miss, a whiteout that isn't represented by a 0,0 chardev or a
456  * fallthrough marker in an opaque directory.
457  *
458  * Note!  (1) This should be used *only* by a filesystem to examine its own
459  * dentries.  It should not be used to look at some other filesystem's
460  * dentries.  (2) It should also be used in combination with d_inode() to get
461  * the inode.  (3) The dentry may have something attached to ->d_lower and the
462  * type field of the flags may be set to something other than miss or whiteout.
463  */
d_really_is_negative(const struct dentry * dentry)464 static inline bool d_really_is_negative(const struct dentry *dentry)
465 {
466 	return dentry->d_inode == NULL;
467 }
468 
469 /**
470  * d_really_is_positive - Determine if a dentry is really positive (ignoring fallthroughs)
471  * @dentry: The dentry in question
472  *
473  * Returns true if the dentry represents a name that maps to an inode
474  * (ie. ->d_inode is not NULL).  The dentry might still represent a whiteout if
475  * that is represented on medium as a 0,0 chardev.
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.
481  */
d_really_is_positive(const struct dentry * dentry)482 static inline bool d_really_is_positive(const struct dentry *dentry)
483 {
484 	return dentry->d_inode != NULL;
485 }
486 
simple_positive(const struct dentry * dentry)487 static inline int simple_positive(const struct dentry *dentry)
488 {
489 	return d_really_is_positive(dentry) && !d_unhashed(dentry);
490 }
491 
492 extern void d_set_fallthru(struct dentry *dentry);
493 
d_is_fallthru(const struct dentry * dentry)494 static inline bool d_is_fallthru(const struct dentry *dentry)
495 {
496 	return dentry->d_flags & DCACHE_FALLTHRU;
497 }
498 
499 
500 extern int sysctl_vfs_cache_pressure;
501 
vfs_pressure_ratio(unsigned long val)502 static inline unsigned long vfs_pressure_ratio(unsigned long val)
503 {
504 	return mult_frac(val, sysctl_vfs_cache_pressure, 100);
505 }
506 
507 /**
508  * d_inode - Get the actual inode of this dentry
509  * @dentry: The dentry to query
510  *
511  * This is the helper normal filesystems should use to get at their own inodes
512  * in their own dentries and ignore the layering superimposed upon them.
513  */
d_inode(const struct dentry * dentry)514 static inline struct inode *d_inode(const struct dentry *dentry)
515 {
516 	return dentry->d_inode;
517 }
518 
519 /**
520  * d_inode_rcu - Get the actual inode of this dentry with READ_ONCE()
521  * @dentry: The dentry to query
522  *
523  * This is the helper normal filesystems should use to get at their own inodes
524  * in their own dentries and ignore the layering superimposed upon them.
525  */
d_inode_rcu(const struct dentry * dentry)526 static inline struct inode *d_inode_rcu(const struct dentry *dentry)
527 {
528 	return READ_ONCE(dentry->d_inode);
529 }
530 
531 /**
532  * d_backing_inode - Get upper or lower inode we should be using
533  * @upper: The upper layer
534  *
535  * This is the helper that should be used to get at the inode that will be used
536  * if this dentry were to be opened as a file.  The inode may be on the upper
537  * dentry or it may be on a lower dentry pinned by the upper.
538  *
539  * Normal filesystems should not use this to access their own inodes.
540  */
d_backing_inode(const struct dentry * upper)541 static inline struct inode *d_backing_inode(const struct dentry *upper)
542 {
543 	struct inode *inode = upper->d_inode;
544 
545 	return inode;
546 }
547 
548 /**
549  * d_backing_dentry - Get upper or lower dentry we should be using
550  * @upper: The upper layer
551  *
552  * This is the helper that should be used to get the dentry of the inode that
553  * will be used if this dentry were opened as a file.  It may be the upper
554  * dentry or it may be a lower dentry pinned by the upper.
555  *
556  * Normal filesystems should not use this to access their own dentries.
557  */
d_backing_dentry(struct dentry * upper)558 static inline struct dentry *d_backing_dentry(struct dentry *upper)
559 {
560 	return upper;
561 }
562 
563 /**
564  * d_real - Return the real dentry
565  * @dentry: the dentry to query
566  * @inode: inode to select the dentry from multiple layers (can be NULL)
567  *
568  * If dentry is on a union/overlay, then return the underlying, real dentry.
569  * Otherwise return the dentry itself.
570  *
571  * See also: Documentation/filesystems/vfs.rst
572  */
d_real(struct dentry * dentry,const struct inode * inode)573 static inline struct dentry *d_real(struct dentry *dentry,
574 				    const struct inode *inode)
575 {
576 	if (unlikely(dentry->d_flags & DCACHE_OP_REAL))
577 		return dentry->d_op->d_real(dentry, inode);
578 	else
579 		return dentry;
580 }
581 
582 /**
583  * d_real_inode - Return the real inode
584  * @dentry: The dentry to query
585  *
586  * If dentry is on a union/overlay, then return the underlying, real inode.
587  * Otherwise return d_inode().
588  */
d_real_inode(const struct dentry * dentry)589 static inline struct inode *d_real_inode(const struct dentry *dentry)
590 {
591 	/* This usage of d_real() results in const dentry */
592 	return d_backing_inode(d_real((struct dentry *) dentry, NULL));
593 }
594 
595 struct name_snapshot {
596 	struct qstr name;
597 	unsigned char inline_name[DNAME_INLINE_LEN];
598 };
599 void take_dentry_name_snapshot(struct name_snapshot *, struct dentry *);
600 void release_dentry_name_snapshot(struct name_snapshot *);
601 
602 #endif	/* __LINUX_DCACHE_H */
603