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_mark_tmpfile(struct file *, struct inode *); |
255 | extern void d_tmpfile(struct file *, struct inode *); |
256 | |
257 | extern struct dentry *d_find_alias(struct inode *); |
258 | extern void d_prune_aliases(struct inode *); |
259 | |
260 | extern struct dentry *d_find_alias_rcu(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 | return dentry->d_lockref.count; |
287 | } |
288 | |
289 | /* |
290 | * helper function for dentry_operations.d_dname() members |
291 | */ |
292 | extern __printf(3, 4) |
293 | char *dynamic_dname(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(const struct dentry *, char *, int); |
299 | extern char *dentry_path(const 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 | if (dentry) |
314 | dentry->d_lockref.count++; |
315 | return dentry; |
316 | } |
317 | |
318 | static inline struct dentry *dget(struct dentry *dentry) |
319 | { |
320 | if (dentry) |
321 | 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(h: &dentry->d_hash); |
337 | } |
338 | |
339 | static inline int d_unlinked(const struct dentry *dentry) |
340 | { |
341 | return d_unhashed(dentry) && !IS_ROOT(dentry); |
342 | } |
343 | |
344 | static inline int cant_mount(const struct dentry *dentry) |
345 | { |
346 | return (dentry->d_flags & DCACHE_CANT_MOUNT); |
347 | } |
348 | |
349 | static inline void dont_mount(struct dentry *dentry) |
350 | { |
351 | spin_lock(lock: &dentry->d_lock); |
352 | dentry->d_flags |= DCACHE_CANT_MOUNT; |
353 | spin_unlock(lock: &dentry->d_lock); |
354 | } |
355 | |
356 | extern void __d_lookup_unhash_wake(struct dentry *dentry); |
357 | |
358 | static inline int d_in_lookup(const struct dentry *dentry) |
359 | { |
360 | return dentry->d_flags & DCACHE_PAR_LOOKUP; |
361 | } |
362 | |
363 | static inline void d_lookup_done(struct dentry *dentry) |
364 | { |
365 | if (unlikely(d_in_lookup(dentry))) |
366 | __d_lookup_unhash_wake(dentry); |
367 | } |
368 | |
369 | extern void dput(struct dentry *); |
370 | |
371 | static inline bool d_managed(const struct dentry *dentry) |
372 | { |
373 | return dentry->d_flags & DCACHE_MANAGED_DENTRY; |
374 | } |
375 | |
376 | static inline bool d_mountpoint(const struct dentry *dentry) |
377 | { |
378 | return dentry->d_flags & DCACHE_MOUNTED; |
379 | } |
380 | |
381 | /* |
382 | * Directory cache entry type accessor functions. |
383 | */ |
384 | static inline unsigned __d_entry_type(const struct dentry *dentry) |
385 | { |
386 | return dentry->d_flags & DCACHE_ENTRY_TYPE; |
387 | } |
388 | |
389 | static inline bool d_is_miss(const struct dentry *dentry) |
390 | { |
391 | return __d_entry_type(dentry) == DCACHE_MISS_TYPE; |
392 | } |
393 | |
394 | static inline bool d_is_whiteout(const struct dentry *dentry) |
395 | { |
396 | return __d_entry_type(dentry) == DCACHE_WHITEOUT_TYPE; |
397 | } |
398 | |
399 | static inline bool d_can_lookup(const struct dentry *dentry) |
400 | { |
401 | return __d_entry_type(dentry) == DCACHE_DIRECTORY_TYPE; |
402 | } |
403 | |
404 | static inline bool d_is_autodir(const struct dentry *dentry) |
405 | { |
406 | return __d_entry_type(dentry) == DCACHE_AUTODIR_TYPE; |
407 | } |
408 | |
409 | static inline bool d_is_dir(const struct dentry *dentry) |
410 | { |
411 | return d_can_lookup(dentry) || d_is_autodir(dentry); |
412 | } |
413 | |
414 | static inline bool d_is_symlink(const struct dentry *dentry) |
415 | { |
416 | return __d_entry_type(dentry) == DCACHE_SYMLINK_TYPE; |
417 | } |
418 | |
419 | static inline bool d_is_reg(const struct dentry *dentry) |
420 | { |
421 | return __d_entry_type(dentry) == DCACHE_REGULAR_TYPE; |
422 | } |
423 | |
424 | static inline bool d_is_special(const struct dentry *dentry) |
425 | { |
426 | return __d_entry_type(dentry) == DCACHE_SPECIAL_TYPE; |
427 | } |
428 | |
429 | static inline bool d_is_file(const struct dentry *dentry) |
430 | { |
431 | return d_is_reg(dentry) || d_is_special(dentry); |
432 | } |
433 | |
434 | static inline bool d_is_negative(const struct dentry *dentry) |
435 | { |
436 | // TODO: check d_is_whiteout(dentry) also. |
437 | return d_is_miss(dentry); |
438 | } |
439 | |
440 | static inline bool d_flags_negative(unsigned flags) |
441 | { |
442 | return (flags & DCACHE_ENTRY_TYPE) == DCACHE_MISS_TYPE; |
443 | } |
444 | |
445 | static inline bool d_is_positive(const struct dentry *dentry) |
446 | { |
447 | return !d_is_negative(dentry); |
448 | } |
449 | |
450 | /** |
451 | * d_really_is_negative - Determine if a dentry is really negative (ignoring fallthroughs) |
452 | * @dentry: The dentry in question |
453 | * |
454 | * Returns true if the dentry represents either an absent name or a name that |
455 | * doesn't map to an inode (ie. ->d_inode is NULL). The dentry could represent |
456 | * a true miss, a whiteout that isn't represented by a 0,0 chardev or a |
457 | * fallthrough marker in an opaque directory. |
458 | * |
459 | * Note! (1) This should be used *only* by a filesystem to examine its own |
460 | * dentries. It should not be used to look at some other filesystem's |
461 | * dentries. (2) It should also be used in combination with d_inode() to get |
462 | * the inode. (3) The dentry may have something attached to ->d_lower and the |
463 | * type field of the flags may be set to something other than miss or whiteout. |
464 | */ |
465 | static inline bool d_really_is_negative(const struct dentry *dentry) |
466 | { |
467 | return dentry->d_inode == NULL; |
468 | } |
469 | |
470 | /** |
471 | * d_really_is_positive - Determine if a dentry is really positive (ignoring fallthroughs) |
472 | * @dentry: The dentry in question |
473 | * |
474 | * Returns true if the dentry represents a name that maps to an inode |
475 | * (ie. ->d_inode is not NULL). The dentry might still represent a whiteout if |
476 | * that is represented on medium as a 0,0 chardev. |
477 | * |
478 | * Note! (1) This should be used *only* by a filesystem to examine its own |
479 | * dentries. It should not be used to look at some other filesystem's |
480 | * dentries. (2) It should also be used in combination with d_inode() to get |
481 | * the inode. |
482 | */ |
483 | static inline bool d_really_is_positive(const struct dentry *dentry) |
484 | { |
485 | return dentry->d_inode != NULL; |
486 | } |
487 | |
488 | static inline int simple_positive(const struct dentry *dentry) |
489 | { |
490 | return d_really_is_positive(dentry) && !d_unhashed(dentry); |
491 | } |
492 | |
493 | extern void d_set_fallthru(struct dentry *dentry); |
494 | |
495 | static inline bool d_is_fallthru(const struct dentry *dentry) |
496 | { |
497 | return dentry->d_flags & DCACHE_FALLTHRU; |
498 | } |
499 | |
500 | |
501 | extern int sysctl_vfs_cache_pressure; |
502 | |
503 | static inline unsigned long vfs_pressure_ratio(unsigned long val) |
504 | { |
505 | return mult_frac(val, sysctl_vfs_cache_pressure, 100); |
506 | } |
507 | |
508 | /** |
509 | * d_inode - Get the actual inode of this dentry |
510 | * @dentry: The dentry to query |
511 | * |
512 | * This is the helper normal filesystems should use to get at their own inodes |
513 | * in their own dentries and ignore the layering superimposed upon them. |
514 | */ |
515 | static inline struct inode *d_inode(const struct dentry *dentry) |
516 | { |
517 | return dentry->d_inode; |
518 | } |
519 | |
520 | /** |
521 | * d_inode_rcu - Get the actual inode of this dentry with READ_ONCE() |
522 | * @dentry: The dentry to query |
523 | * |
524 | * This is the helper normal filesystems should use to get at their own inodes |
525 | * in their own dentries and ignore the layering superimposed upon them. |
526 | */ |
527 | static inline struct inode *d_inode_rcu(const struct dentry *dentry) |
528 | { |
529 | return READ_ONCE(dentry->d_inode); |
530 | } |
531 | |
532 | /** |
533 | * d_backing_inode - Get upper or lower inode we should be using |
534 | * @upper: The upper layer |
535 | * |
536 | * This is the helper that should be used to get at the inode that will be used |
537 | * if this dentry were to be opened as a file. The inode may be on the upper |
538 | * dentry or it may be on a lower dentry pinned by the upper. |
539 | * |
540 | * Normal filesystems should not use this to access their own inodes. |
541 | */ |
542 | static inline struct inode *d_backing_inode(const struct dentry *upper) |
543 | { |
544 | struct inode *inode = upper->d_inode; |
545 | |
546 | return inode; |
547 | } |
548 | |
549 | /** |
550 | * d_backing_dentry - Get upper or lower dentry we should be using |
551 | * @upper: The upper layer |
552 | * |
553 | * This is the helper that should be used to get the dentry of the inode that |
554 | * will be used if this dentry were opened as a file. It may be the upper |
555 | * dentry or it may be a lower dentry pinned by the upper. |
556 | * |
557 | * Normal filesystems should not use this to access their own dentries. |
558 | */ |
559 | static inline struct dentry *d_backing_dentry(struct dentry *upper) |
560 | { |
561 | return upper; |
562 | } |
563 | |
564 | /** |
565 | * d_real - Return the real dentry |
566 | * @dentry: the dentry to query |
567 | * @inode: inode to select the dentry from multiple layers (can be NULL) |
568 | * |
569 | * If dentry is on a union/overlay, then return the underlying, real dentry. |
570 | * Otherwise return the dentry itself. |
571 | * |
572 | * See also: Documentation/filesystems/vfs.rst |
573 | */ |
574 | static inline struct dentry *d_real(struct dentry *dentry, |
575 | const struct inode *inode) |
576 | { |
577 | if (unlikely(dentry->d_flags & DCACHE_OP_REAL)) |
578 | return dentry->d_op->d_real(dentry, inode); |
579 | else |
580 | return dentry; |
581 | } |
582 | |
583 | /** |
584 | * d_real_inode - Return the real inode |
585 | * @dentry: The dentry to query |
586 | * |
587 | * If dentry is on a union/overlay, then return the underlying, real inode. |
588 | * Otherwise return d_inode(). |
589 | */ |
590 | static inline struct inode *d_real_inode(const struct dentry *dentry) |
591 | { |
592 | /* This usage of d_real() results in const dentry */ |
593 | return d_backing_inode(upper: d_real(dentry: (struct dentry *) dentry, NULL)); |
594 | } |
595 | |
596 | struct name_snapshot { |
597 | struct qstr name; |
598 | unsigned char inline_name[DNAME_INLINE_LEN]; |
599 | }; |
600 | void take_dentry_name_snapshot(struct name_snapshot *, struct dentry *); |
601 | void release_dentry_name_snapshot(struct name_snapshot *); |
602 | |
603 | #endif /* __LINUX_DCACHE_H */ |
604 | |