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