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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/rculist.h>
8 : : #include <linux/rculist_bl.h>
9 : : #include <linux/spinlock.h>
10 : : #include <linux/seqlock.h>
11 : : #include <linux/cache.h>
12 : : #include <linux/rcupdate.h>
13 : : #include <linux/lockref.h>
14 : : #include <linux/stringhash.h>
15 : : #include <linux/wait.h>
16 : :
17 : : struct path;
18 : : struct vfsmount;
19 : :
20 : : /*
21 : : * linux/include/linux/dcache.h
22 : : *
23 : : * Dirent cache data structures
24 : : *
25 : : * (C) Copyright 1997 Thomas Schoebel-Theuer,
26 : : * with heavy changes by Linus Torvalds
27 : : */
28 : :
29 : : #define IS_ROOT(x) ((x) == (x)->d_parent)
30 : :
31 : : /* The hash is always the low bits of hash_len */
32 : : #ifdef __LITTLE_ENDIAN
33 : : #define HASH_LEN_DECLARE u32 hash; u32 len
34 : : #define bytemask_from_count(cnt) (~(~0ul << (cnt)*8))
35 : : #else
36 : : #define HASH_LEN_DECLARE u32 len; u32 hash
37 : : #define bytemask_from_count(cnt) (~(~0ul >> (cnt)*8))
38 : : #endif
39 : :
40 : : /*
41 : : * "quick string" -- eases parameter passing, but more importantly
42 : : * saves "metadata" about the string (ie length and the hash).
43 : : *
44 : : * hash comes first so it snuggles against d_parent in the
45 : : * dentry.
46 : : */
47 : : struct qstr {
48 : : union {
49 : : struct {
50 : : HASH_LEN_DECLARE;
51 : : };
52 : : u64 hash_len;
53 : : };
54 : : const unsigned char *name;
55 : : };
56 : :
57 : : #define QSTR_INIT(n,l) { { { .len = l } }, .name = n }
58 : :
59 : : extern const struct qstr empty_name;
60 : : extern const struct qstr slash_name;
61 : :
62 : : struct dentry_stat_t {
63 : : long nr_dentry;
64 : : long nr_unused;
65 : : long age_limit; /* age in seconds */
66 : : long want_pages; /* pages requested by system */
67 : : long nr_negative; /* # of unused negative dentries */
68 : : long dummy; /* Reserved for future use */
69 : : };
70 : : extern struct dentry_stat_t dentry_stat;
71 : :
72 : : /*
73 : : * Try to keep struct dentry aligned on 64 byte cachelines (this will
74 : : * give reasonable cacheline footprint with larger lines without the
75 : : * large memory footprint increase).
76 : : */
77 : : #ifdef CONFIG_64BIT
78 : : # define DNAME_INLINE_LEN 32 /* 192 bytes */
79 : : #else
80 : : # ifdef CONFIG_SMP
81 : : # define DNAME_INLINE_LEN 36 /* 128 bytes */
82 : : # else
83 : : # define DNAME_INLINE_LEN 40 /* 128 bytes */
84 : : # endif
85 : : #endif
86 : :
87 : : #define d_lock d_lockref.lock
88 : :
89 : : struct dentry {
90 : : /* RCU lookup touched fields */
91 : : unsigned int d_flags; /* protected by d_lock */
92 : : seqcount_t d_seq; /* per dentry seqlock */
93 : : struct hlist_bl_node d_hash; /* lookup hash list */
94 : : struct dentry *d_parent; /* parent directory */
95 : : struct qstr d_name;
96 : : struct inode *d_inode; /* Where the name belongs to - NULL is
97 : : * negative */
98 : : unsigned char d_iname[DNAME_INLINE_LEN]; /* small names */
99 : :
100 : : /* Ref lookup also touches following */
101 : : struct lockref d_lockref; /* per-dentry lock and refcount */
102 : : const struct dentry_operations *d_op;
103 : : struct super_block *d_sb; /* The root of the dentry tree */
104 : : unsigned long d_time; /* used by d_revalidate */
105 : : void *d_fsdata; /* fs-specific data */
106 : :
107 : : union {
108 : : struct list_head d_lru; /* LRU list */
109 : : wait_queue_head_t *d_wait; /* in-lookup ones only */
110 : : };
111 : : struct list_head d_child; /* child of parent list */
112 : : struct list_head d_subdirs; /* our children */
113 : : /*
114 : : * d_alias and d_rcu can share memory
115 : : */
116 : : union {
117 : : struct hlist_node d_alias; /* inode alias list */
118 : : struct hlist_bl_node d_in_lookup_hash; /* only for in-lookup ones */
119 : : struct rcu_head d_rcu;
120 : : } d_u;
121 : : } __randomize_layout;
122 : :
123 : : /*
124 : : * dentry->d_lock spinlock nesting subclasses:
125 : : *
126 : : * 0: normal
127 : : * 1: nested
128 : : */
129 : : enum dentry_d_lock_class
130 : : {
131 : : DENTRY_D_LOCK_NORMAL, /* implicitly used by plain spin_lock() APIs. */
132 : : DENTRY_D_LOCK_NESTED
133 : : };
134 : :
135 : : struct dentry_operations {
136 : : int (*d_revalidate)(struct dentry *, unsigned int);
137 : : int (*d_weak_revalidate)(struct dentry *, unsigned int);
138 : : int (*d_hash)(const struct dentry *, struct qstr *);
139 : : int (*d_compare)(const struct dentry *,
140 : : unsigned int, const char *, const struct qstr *);
141 : : int (*d_delete)(const struct dentry *);
142 : : int (*d_init)(struct dentry *);
143 : : void (*d_release)(struct dentry *);
144 : : void (*d_prune)(struct dentry *);
145 : : void (*d_iput)(struct dentry *, struct inode *);
146 : : char *(*d_dname)(struct dentry *, char *, int);
147 : : struct vfsmount *(*d_automount)(struct path *);
148 : : int (*d_manage)(const struct path *, bool);
149 : : struct dentry *(*d_real)(struct dentry *, const struct inode *);
150 : : } ____cacheline_aligned;
151 : :
152 : : /*
153 : : * Locking rules for dentry_operations callbacks are to be found in
154 : : * Documentation/filesystems/locking.rst. Keep it updated!
155 : : *
156 : : * FUrther descriptions are found in Documentation/filesystems/vfs.rst.
157 : : * Keep it updated too!
158 : : */
159 : :
160 : : /* d_flags entries */
161 : : #define DCACHE_OP_HASH 0x00000001
162 : : #define DCACHE_OP_COMPARE 0x00000002
163 : : #define DCACHE_OP_REVALIDATE 0x00000004
164 : : #define DCACHE_OP_DELETE 0x00000008
165 : : #define DCACHE_OP_PRUNE 0x00000010
166 : :
167 : : #define DCACHE_DISCONNECTED 0x00000020
168 : : /* This dentry is possibly not currently connected to the dcache tree, in
169 : : * which case its parent will either be itself, or will have this flag as
170 : : * well. nfsd will not use a dentry with this bit set, but will first
171 : : * endeavour to clear the bit either by discovering that it is connected,
172 : : * or by performing lookup operations. Any filesystem which supports
173 : : * nfsd_operations MUST have a lookup function which, if it finds a
174 : : * directory inode with a DCACHE_DISCONNECTED dentry, will d_move that
175 : : * dentry into place and return that dentry rather than the passed one,
176 : : * typically using d_splice_alias. */
177 : :
178 : : #define DCACHE_REFERENCED 0x00000040 /* Recently used, don't discard. */
179 : :
180 : : #define DCACHE_CANT_MOUNT 0x00000100
181 : : #define DCACHE_GENOCIDE 0x00000200
182 : : #define DCACHE_SHRINK_LIST 0x00000400
183 : :
184 : : #define DCACHE_OP_WEAK_REVALIDATE 0x00000800
185 : :
186 : : #define DCACHE_NFSFS_RENAMED 0x00001000
187 : : /* this dentry has been "silly renamed" and has to be deleted on the last
188 : : * dput() */
189 : : #define DCACHE_COOKIE 0x00002000 /* For use by dcookie subsystem */
190 : : #define DCACHE_FSNOTIFY_PARENT_WATCHED 0x00004000
191 : : /* Parent inode is watched by some fsnotify listener */
192 : :
193 : : #define DCACHE_DENTRY_KILLED 0x00008000
194 : :
195 : : #define DCACHE_MOUNTED 0x00010000 /* is a mountpoint */
196 : : #define DCACHE_NEED_AUTOMOUNT 0x00020000 /* handle automount on this dir */
197 : : #define DCACHE_MANAGE_TRANSIT 0x00040000 /* manage transit from this dirent */
198 : : #define DCACHE_MANAGED_DENTRY \
199 : : (DCACHE_MOUNTED|DCACHE_NEED_AUTOMOUNT|DCACHE_MANAGE_TRANSIT)
200 : :
201 : : #define DCACHE_LRU_LIST 0x00080000
202 : :
203 : : #define DCACHE_ENTRY_TYPE 0x00700000
204 : : #define DCACHE_MISS_TYPE 0x00000000 /* Negative dentry (maybe fallthru to nowhere) */
205 : : #define DCACHE_WHITEOUT_TYPE 0x00100000 /* Whiteout dentry (stop pathwalk) */
206 : : #define DCACHE_DIRECTORY_TYPE 0x00200000 /* Normal directory */
207 : : #define DCACHE_AUTODIR_TYPE 0x00300000 /* Lookupless directory (presumed automount) */
208 : : #define DCACHE_REGULAR_TYPE 0x00400000 /* Regular file type (or fallthru to such) */
209 : : #define DCACHE_SPECIAL_TYPE 0x00500000 /* Other file type (or fallthru to such) */
210 : : #define DCACHE_SYMLINK_TYPE 0x00600000 /* Symlink (or fallthru to such) */
211 : :
212 : : #define DCACHE_MAY_FREE 0x00800000
213 : : #define DCACHE_FALLTHRU 0x01000000 /* Fall through to lower layer */
214 : : #define DCACHE_ENCRYPTED_NAME 0x02000000 /* Encrypted name (dir key was unavailable) */
215 : : #define DCACHE_OP_REAL 0x04000000
216 : :
217 : : #define DCACHE_PAR_LOOKUP 0x10000000 /* being looked up (with parent locked shared) */
218 : : #define DCACHE_DENTRY_CURSOR 0x20000000
219 : : #define DCACHE_NORCU 0x40000000 /* No RCU delay for freeing */
220 : :
221 : : extern seqlock_t rename_lock;
222 : :
223 : : /*
224 : : * These are the low-level FS interfaces to the dcache..
225 : : */
226 : : extern void d_instantiate(struct dentry *, struct inode *);
227 : : extern void d_instantiate_new(struct dentry *, struct inode *);
228 : : extern struct dentry * d_instantiate_unique(struct dentry *, struct inode *);
229 : : extern struct dentry * d_instantiate_anon(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 struct dentry * d_exact_alias(struct dentry *, struct inode *);
243 : : extern struct dentry *d_find_any_alias(struct inode *inode);
244 : : extern struct dentry * d_obtain_alias(struct inode *);
245 : : extern struct dentry * d_obtain_root(struct inode *);
246 : : extern void shrink_dcache_sb(struct super_block *);
247 : : extern void shrink_dcache_parent(struct dentry *);
248 : : extern void shrink_dcache_for_umount(struct super_block *);
249 : : extern void d_invalidate(struct dentry *);
250 : :
251 : : /* only used at mount-time */
252 : : extern struct dentry * d_make_root(struct inode *);
253 : :
254 : : /* <clickety>-<click> the ramfs-type tree */
255 : : extern void d_genocide(struct dentry *);
256 : :
257 : : extern void d_tmpfile(struct dentry *, struct inode *);
258 : :
259 : : extern struct dentry *d_find_alias(struct inode *);
260 : : extern void d_prune_aliases(struct inode *);
261 : :
262 : : /* test whether we have any submounts in a subdir tree */
263 : : extern int path_has_submounts(const struct path *);
264 : :
265 : : /*
266 : : * This adds the entry to the hash queues.
267 : : */
268 : : extern void d_rehash(struct dentry *);
269 : :
270 : : extern void d_add(struct dentry *, struct inode *);
271 : :
272 : : /* used for rename() and baskets */
273 : : extern void d_move(struct dentry *, struct dentry *);
274 : : extern void d_exchange(struct dentry *, struct dentry *);
275 : : extern struct dentry *d_ancestor(struct dentry *, struct dentry *);
276 : :
277 : : /* appendix may either be NULL or be used for transname suffixes */
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 : : extern struct dentry *__d_lookup(const struct dentry *, const struct qstr *);
281 : : extern struct dentry *__d_lookup_rcu(const struct dentry *parent,
282 : : const struct qstr *name, unsigned *seq);
283 : :
284 : : static inline unsigned d_count(const struct dentry *dentry)
285 : : {
286 : 0 : return dentry->d_lockref.count;
287 : : }
288 : :
289 : : /*
290 : : * helper function for dentry_operations.d_dname() members
291 : : */
292 : : extern __printf(4, 5)
293 : : char *dynamic_dname(struct dentry *, char *, int, const char *, ...);
294 : :
295 : : extern char *__d_path(const struct path *, const struct path *, char *, int);
296 : : extern char *d_absolute_path(const struct path *, char *, int);
297 : : extern char *d_path(const struct path *, char *, int);
298 : : extern char *dentry_path_raw(struct dentry *, char *, int);
299 : : extern char *dentry_path(struct dentry *, char *, int);
300 : :
301 : : /* Allocation counts.. */
302 : :
303 : : /**
304 : : * dget, dget_dlock - get a reference to a dentry
305 : : * @dentry: dentry to get a reference to
306 : : *
307 : : * Given a dentry or %NULL pointer increment the reference count
308 : : * if appropriate and return the dentry. A dentry will not be
309 : : * destroyed when it has references.
310 : : */
311 : : static inline struct dentry *dget_dlock(struct dentry *dentry)
312 : : {
313 [ + - # # ]: 2364100 : if (dentry)
314 : 2364100 : dentry->d_lockref.count++;
315 : : return dentry;
316 : : }
317 : :
318 : : static inline struct dentry *dget(struct dentry *dentry)
319 : : {
320 [ + + + - : 38084096 : if (dentry)
+ - + - +
- + - + -
+ + # # #
# + + ]
321 : 38083930 : lockref_get(&dentry->d_lockref);
322 : : return dentry;
323 : : }
324 : :
325 : : extern struct dentry *dget_parent(struct dentry *dentry);
326 : :
327 : : /**
328 : : * d_unhashed - is dentry hashed
329 : : * @dentry: entry to check
330 : : *
331 : : * Returns true if the dentry passed is not currently hashed.
332 : : */
333 : :
334 : : static inline int d_unhashed(const struct dentry *dentry)
335 : : {
336 : : return hlist_bl_unhashed(&dentry->d_hash);
337 : : }
338 : :
339 : : static inline int d_unlinked(const struct dentry *dentry)
340 : : {
341 [ + + + + : 2841206 : return d_unhashed(dentry) && !IS_ROOT(dentry);
+ + + + +
+ + + ]
342 : : }
343 : :
344 : : static inline int cant_mount(const struct dentry *dentry)
345 : : {
346 : 23836 : return (dentry->d_flags & DCACHE_CANT_MOUNT);
347 : : }
348 : :
349 : 105986 : static inline void dont_mount(struct dentry *dentry)
350 : : {
351 : : spin_lock(&dentry->d_lock);
352 : 105986 : dentry->d_flags |= DCACHE_CANT_MOUNT;
353 : : spin_unlock(&dentry->d_lock);
354 : 105986 : }
355 : :
356 : : extern void __d_lookup_done(struct dentry *);
357 : :
358 : : static inline int d_in_lookup(const struct dentry *dentry)
359 : : {
360 : 77233674 : return dentry->d_flags & DCACHE_PAR_LOOKUP;
361 : : }
362 : :
363 : 18043440 : static inline void d_lookup_done(struct dentry *dentry)
364 : : {
365 [ + + ]: 18043440 : if (unlikely(d_in_lookup(dentry))) {
366 : : spin_lock(&dentry->d_lock);
367 : 2575050 : __d_lookup_done(dentry);
368 : : spin_unlock(&dentry->d_lock);
369 : : }
370 : 18043390 : }
371 : :
372 : : extern void dput(struct dentry *);
373 : :
374 : : static inline bool d_managed(const struct dentry *dentry)
375 : : {
376 : : return dentry->d_flags & DCACHE_MANAGED_DENTRY;
377 : : }
378 : :
379 : : static inline bool d_mountpoint(const struct dentry *dentry)
380 : : {
381 : 115844494 : return dentry->d_flags & DCACHE_MOUNTED;
382 : : }
383 : :
384 : : /*
385 : : * Directory cache entry type accessor functions.
386 : : */
387 : : static inline unsigned __d_entry_type(const struct dentry *dentry)
388 : : {
389 : 432688178 : return dentry->d_flags & DCACHE_ENTRY_TYPE;
390 : : }
391 : :
392 : : static inline bool d_is_miss(const struct dentry *dentry)
393 : : {
394 : 152093542 : return __d_entry_type(dentry) == DCACHE_MISS_TYPE;
395 : : }
396 : :
397 : : static inline bool d_is_whiteout(const struct dentry *dentry)
398 : : {
399 : : return __d_entry_type(dentry) == DCACHE_WHITEOUT_TYPE;
400 : : }
401 : :
402 : : static inline bool d_can_lookup(const struct dentry *dentry)
403 : : {
404 : : return __d_entry_type(dentry) == DCACHE_DIRECTORY_TYPE;
405 : : }
406 : :
407 : : static inline bool d_is_autodir(const struct dentry *dentry)
408 : : {
409 : : return __d_entry_type(dentry) == DCACHE_AUTODIR_TYPE;
410 : : }
411 : :
412 : : static inline bool d_is_dir(const struct dentry *dentry)
413 : : {
414 [ - + # # : 639812 : return d_can_lookup(dentry) || d_is_autodir(dentry);
+ + + - +
+ + - + +
+ - # # #
# + - + -
- + # # +
- + - ]
415 : : }
416 : :
417 : : static inline bool d_is_symlink(const struct dentry *dentry)
418 : : {
419 : : return __d_entry_type(dentry) == DCACHE_SYMLINK_TYPE;
420 : : }
421 : :
422 : : static inline bool d_is_reg(const struct dentry *dentry)
423 : : {
424 : : return __d_entry_type(dentry) == DCACHE_REGULAR_TYPE;
425 : : }
426 : :
427 : : static inline bool d_is_special(const struct dentry *dentry)
428 : : {
429 : : return __d_entry_type(dentry) == DCACHE_SPECIAL_TYPE;
430 : : }
431 : :
432 : : static inline bool d_is_file(const struct dentry *dentry)
433 : : {
434 : : return d_is_reg(dentry) || d_is_special(dentry);
435 : : }
436 : :
437 : : static inline bool d_is_negative(const struct dentry *dentry)
438 : : {
439 : : // TODO: check d_is_whiteout(dentry) also.
440 : : return d_is_miss(dentry);
441 : : }
442 : :
443 : : static inline bool d_is_positive(const struct dentry *dentry)
444 : : {
445 : 278446 : return !d_is_negative(dentry);
446 : : }
447 : :
448 : : /**
449 : : * d_really_is_negative - Determine if a dentry is really negative (ignoring fallthroughs)
450 : : * @dentry: The dentry in question
451 : : *
452 : : * Returns true if the dentry represents either an absent name or a name that
453 : : * doesn't map to an inode (ie. ->d_inode is NULL). The dentry could represent
454 : : * a true miss, a whiteout that isn't represented by a 0,0 chardev or a
455 : : * fallthrough marker in an opaque directory.
456 : : *
457 : : * Note! (1) This should be used *only* by a filesystem to examine its own
458 : : * dentries. It should not be used to look at some other filesystem's
459 : : * dentries. (2) It should also be used in combination with d_inode() to get
460 : : * the inode. (3) The dentry may have something attached to ->d_lower and the
461 : : * type field of the flags may be set to something other than miss or whiteout.
462 : : */
463 : : static inline bool d_really_is_negative(const struct dentry *dentry)
464 : : {
465 : 62805610 : return dentry->d_inode == NULL;
466 : : }
467 : :
468 : : /**
469 : : * d_really_is_positive - Determine if a dentry is really positive (ignoring fallthroughs)
470 : : * @dentry: The dentry in question
471 : : *
472 : : * Returns true if the dentry represents a name that maps to an inode
473 : : * (ie. ->d_inode is not NULL). The dentry might still represent a whiteout if
474 : : * that is represented on medium as a 0,0 chardev.
475 : : *
476 : : * Note! (1) This should be used *only* by a filesystem to examine its own
477 : : * dentries. It should not be used to look at some other filesystem's
478 : : * dentries. (2) It should also be used in combination with d_inode() to get
479 : : * the inode.
480 : : */
481 : : static inline bool d_really_is_positive(const struct dentry *dentry)
482 : : {
483 : 7023734 : return dentry->d_inode != NULL;
484 : : }
485 : :
486 : : static inline int simple_positive(const struct dentry *dentry)
487 : : {
488 [ + - - + : 9458016 : return d_really_is_positive(dentry) && !d_unhashed(dentry);
+ - - + +
- - + ]
489 : : }
490 : :
491 : : extern void d_set_fallthru(struct dentry *dentry);
492 : :
493 : : static inline bool d_is_fallthru(const struct dentry *dentry)
494 : : {
495 : : return dentry->d_flags & DCACHE_FALLTHRU;
496 : : }
497 : :
498 : :
499 : : extern int sysctl_vfs_cache_pressure;
500 : :
501 : : static inline unsigned long vfs_pressure_ratio(unsigned long val)
502 : : {
503 : 0 : return mult_frac(val, sysctl_vfs_cache_pressure, 100);
504 : : }
505 : :
506 : : /**
507 : : * d_inode - Get the actual inode of this dentry
508 : : * @dentry: The dentry to query
509 : : *
510 : : * This is the helper normal filesystems should use to get at their own inodes
511 : : * in their own dentries and ignore the layering superimposed upon them.
512 : : */
513 : : static inline struct inode *d_inode(const struct dentry *dentry)
514 : : {
515 : 109969468 : return dentry->d_inode;
516 : : }
517 : :
518 : : /**
519 : : * d_inode_rcu - Get the actual inode of this dentry with READ_ONCE()
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 : : */
525 : : static inline struct inode *d_inode_rcu(const struct dentry *dentry)
526 : : {
527 : 54540 : return READ_ONCE(dentry->d_inode);
528 : : }
529 : :
530 : : /**
531 : : * d_backing_inode - Get upper or lower inode we should be using
532 : : * @upper: The upper layer
533 : : *
534 : : * This is the helper that should be used to get at the inode that will be used
535 : : * if this dentry were to be opened as a file. The inode may be on the upper
536 : : * dentry or it may be on a lower dentry pinned by the upper.
537 : : *
538 : : * Normal filesystems should not use this to access their own inodes.
539 : : */
540 : : static inline struct inode *d_backing_inode(const struct dentry *upper)
541 : : {
542 : 244767914 : struct inode *inode = upper->d_inode;
543 : :
544 : : return inode;
545 : : }
546 : :
547 : : /**
548 : : * d_backing_dentry - Get upper or lower dentry we should be using
549 : : * @upper: The upper layer
550 : : *
551 : : * This is the helper that should be used to get the dentry of the inode that
552 : : * will be used if this dentry were opened as a file. It may be the upper
553 : : * dentry or it may be a lower dentry pinned by the upper.
554 : : *
555 : : * Normal filesystems should not use this to access their own dentries.
556 : : */
557 : : static inline struct dentry *d_backing_dentry(struct dentry *upper)
558 : : {
559 : : return upper;
560 : : }
561 : :
562 : : /**
563 : : * d_real - Return the real dentry
564 : : * @dentry: the dentry to query
565 : : * @inode: inode to select the dentry from multiple layers (can be NULL)
566 : : *
567 : : * If dentry is on a union/overlay, then return the underlying, real dentry.
568 : : * Otherwise return the dentry itself.
569 : : *
570 : : * See also: Documentation/filesystems/vfs.rst
571 : : */
572 : : static inline struct dentry *d_real(struct dentry *dentry,
573 : : const struct inode *inode)
574 : : {
575 [ - + # # : 6834894 : if (unlikely(dentry->d_flags & DCACHE_OP_REAL))
# # ]
576 : 0 : return dentry->d_op->d_real(dentry, inode);
577 : : else
578 : : return dentry;
579 : : }
580 : :
581 : : /**
582 : : * d_real_inode - Return the real inode
583 : : * @dentry: The dentry to query
584 : : *
585 : : * If dentry is on a union/overlay, then return the underlying, real inode.
586 : : * Otherwise return d_inode().
587 : : */
588 : : static inline struct inode *d_real_inode(const struct dentry *dentry)
589 : : {
590 : : /* This usage of d_real() results in const dentry */
591 : : return d_backing_inode(d_real((struct dentry *) dentry, NULL));
592 : : }
593 : :
594 : : struct name_snapshot {
595 : : struct qstr name;
596 : : unsigned char inline_name[DNAME_INLINE_LEN];
597 : : };
598 : : void take_dentry_name_snapshot(struct name_snapshot *, struct dentry *);
599 : : void release_dentry_name_snapshot(struct name_snapshot *);
600 : :
601 : : #endif /* __LINUX_DCACHE_H */
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