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 #define QSTR_LEN(n,l) (struct qstr)QSTR_INIT(n,l)
61 #define QSTR(n) QSTR_LEN(n, strlen(n))
62
63 extern const struct qstr empty_name;
64 extern const struct qstr slash_name;
65 extern const struct qstr dotdot_name;
66
67 /*
68 * Try to keep struct dentry aligned on 64 byte cachelines (this will
69 * give reasonable cacheline footprint with larger lines without the
70 * large memory footprint increase).
71 */
72 #ifdef CONFIG_64BIT
73 # define DNAME_INLINE_WORDS 5 /* 192 bytes */
74 #else
75 # ifdef CONFIG_SMP
76 # define DNAME_INLINE_WORDS 9 /* 128 bytes */
77 # else
78 # define DNAME_INLINE_WORDS 11 /* 128 bytes */
79 # endif
80 #endif
81
82 #define DNAME_INLINE_LEN (DNAME_INLINE_WORDS*sizeof(unsigned long))
83
84 union shortname_store {
85 unsigned char string[DNAME_INLINE_LEN];
86 unsigned long words[DNAME_INLINE_WORDS];
87 };
88
89 #define d_lock d_lockref.lock
90 #define d_iname d_shortname.string
91 struct completion_list;
92
93 struct dentry {
94 /* RCU lookup touched fields */
95 unsigned int d_flags; /* protected by d_lock */
96 seqcount_spinlock_t d_seq; /* per dentry seqlock */
97 struct hlist_bl_node d_hash; /* lookup hash list */
98 struct dentry *d_parent; /* parent directory */
99 union {
100 struct qstr __d_name; /* for use ONLY in fs/dcache.c */
101 const struct qstr d_name;
102 };
103 struct inode *d_inode; /* Where the name belongs to - NULL is
104 * negative */
105 union shortname_store d_shortname;
106 /* --- cacheline 1 boundary (64 bytes) was 32 bytes ago --- */
107
108 /* Ref lookup also touches following */
109 const struct dentry_operations *d_op;
110 struct super_block *d_sb; /* The root of the dentry tree */
111 unsigned long d_time; /* used by d_revalidate */
112 void *d_fsdata; /* fs-specific data */
113 /* --- cacheline 2 boundary (128 bytes) --- */
114 struct lockref d_lockref; /* per-dentry lock and refcount
115 * keep separate from RCU lookup area if
116 * possible!
117 */
118
119 /* lockdep tracking of DCACHE_PAR_LOOKUP locks */
120 struct lockdep_map dep_map;
121 struct list_head d_lru; /* LRU list */
122 struct hlist_node d_sib; /* child of parent list */
123 struct hlist_head d_children; /* our children */
124 /*
125 * the following members can share memory - their uses are
126 * mutually exclusive.
127 */
128 union {
129 /* positives: inode alias list */
130 struct hlist_node d_alias;
131 /* in-lookup ones (all negative, live): hash chain */
132 struct hlist_bl_node d_in_lookup_hash;
133 /* killed ones: (already negative) used to schedule freeing */
134 struct rcu_head d_rcu;
135 /*
136 * live non-in-lookup negatives: used if shrink_dcache_tree()
137 * races with eviction by another thread and needs to wait for
138 * this dentry to get killed . Remains NULL for almost all
139 * negative dentries.
140 */
141 struct completion_list *waiters;
142 };
143 };
144
145 /*
146 * dentry->d_lock spinlock nesting subclasses:
147 *
148 * 0: normal
149 * 1: nested
150 */
151 enum dentry_d_lock_class
152 {
153 DENTRY_D_LOCK_NORMAL, /* implicitly used by plain spin_lock() APIs. */
154 DENTRY_D_LOCK_NESTED
155 };
156
157 enum d_real_type {
158 D_REAL_DATA,
159 D_REAL_METADATA,
160 };
161
162 struct dentry_operations {
163 int (*d_revalidate)(struct inode *, const struct qstr *,
164 struct dentry *, unsigned int);
165 int (*d_weak_revalidate)(struct dentry *, unsigned int);
166 int (*d_hash)(const struct dentry *, struct qstr *);
167 int (*d_compare)(const struct dentry *,
168 unsigned int, const char *, const struct qstr *);
169 int (*d_delete)(const struct dentry *);
170 int (*d_init)(struct dentry *);
171 void (*d_release)(struct dentry *);
172 void (*d_prune)(struct dentry *);
173 void (*d_iput)(struct dentry *, struct inode *);
174 char *(*d_dname)(struct dentry *, char *, int);
175 struct vfsmount *(*d_automount)(struct path *);
176 int (*d_manage)(const struct path *, bool);
177 struct dentry *(*d_real)(struct dentry *, enum d_real_type type);
178 bool (*d_unalias_trylock)(const struct dentry *);
179 void (*d_unalias_unlock)(const struct dentry *);
180 } ____cacheline_aligned;
181
182 /*
183 * Locking rules for dentry_operations callbacks are to be found in
184 * Documentation/filesystems/locking.rst. Keep it updated!
185 *
186 * FUrther descriptions are found in Documentation/filesystems/vfs.rst.
187 * Keep it updated too!
188 */
189
190 /* d_flags entries */
191 enum dentry_flags {
192 DCACHE_OP_HASH = BIT(0),
193 DCACHE_OP_COMPARE = BIT(1),
194 DCACHE_OP_REVALIDATE = BIT(2),
195 DCACHE_OP_DELETE = BIT(3),
196 DCACHE_OP_PRUNE = BIT(4),
197 /*
198 * This dentry is possibly not currently connected to the dcache tree,
199 * in which case its parent will either be itself, or will have this
200 * flag as well. nfsd will not use a dentry with this bit set, but will
201 * first endeavour to clear the bit either by discovering that it is
202 * connected, or by performing lookup operations. Any filesystem which
203 * supports nfsd_operations MUST have a lookup function which, if it
204 * finds a directory inode with a DCACHE_DISCONNECTED dentry, will
205 * d_move that dentry into place and return that dentry rather than the
206 * passed one, typically using d_splice_alias.
207 */
208 DCACHE_DISCONNECTED = BIT(5),
209 DCACHE_REFERENCED = BIT(6), /* Recently used, don't discard. */
210 DCACHE_DONTCACHE = BIT(7), /* Purge from memory on final dput() */
211 DCACHE_CANT_MOUNT = BIT(8),
212 DCACHE_LOOKUP_WAITERS = BIT(9), /* A thread is waiting for
213 * PAR_LOOKUP to clear
214 */
215 DCACHE_SHRINK_LIST = BIT(10),
216 DCACHE_OP_WEAK_REVALIDATE = BIT(11),
217 /*
218 * this dentry has been "silly renamed" and has to be deleted on the
219 * last dput()
220 */
221 DCACHE_NFSFS_RENAMED = BIT(12),
222 DCACHE_FSNOTIFY_PARENT_WATCHED = BIT(13), /* Parent inode is watched by some fsnotify listener */
223 DCACHE_DENTRY_KILLED = BIT(14),
224 DCACHE_MOUNTED = BIT(15), /* is a mountpoint */
225 DCACHE_NEED_AUTOMOUNT = BIT(16), /* handle automount on this dir */
226 DCACHE_MANAGE_TRANSIT = BIT(17), /* manage transit from this dirent */
227 DCACHE_LRU_LIST = BIT(18),
228 DCACHE_ENTRY_TYPE = (7 << 19), /* bits 19..21 are for storing type: */
229 DCACHE_MISS_TYPE = (0 << 19), /* Negative dentry */
230 DCACHE_WHITEOUT_TYPE = (1 << 19), /* Whiteout dentry (stop pathwalk) */
231 DCACHE_DIRECTORY_TYPE = (2 << 19), /* Normal directory */
232 DCACHE_AUTODIR_TYPE = (3 << 19), /* Lookupless directory (presumed automount) */
233 DCACHE_REGULAR_TYPE = (4 << 19), /* Regular file type */
234 DCACHE_SPECIAL_TYPE = (5 << 19), /* Other file type */
235 DCACHE_SYMLINK_TYPE = (6 << 19), /* Symlink */
236 DCACHE_NOKEY_NAME = BIT(22), /* Encrypted name encoded without key */
237 DCACHE_OP_REAL = BIT(23),
238 DCACHE_PAR_LOOKUP = BIT(24), /* being looked up (with parent locked shared) */
239 DCACHE_DENTRY_CURSOR = BIT(25),
240 DCACHE_NORCU = BIT(26), /* No RCU delay for freeing */
241 DCACHE_PERSISTENT = BIT(27),
242 /* 28, 29, 30 free */
243 DCACHE_PRIVATE = BIT(31) /* fs-specific flag */
244 };
245
246 #define DCACHE_MANAGED_DENTRY \
247 (DCACHE_MOUNTED|DCACHE_NEED_AUTOMOUNT|DCACHE_MANAGE_TRANSIT)
248
249 extern seqlock_t rename_lock;
250
251 /*
252 * These are the low-level FS interfaces to the dcache..
253 */
254 extern void d_instantiate(struct dentry *, struct inode *);
255 extern void d_instantiate_new(struct dentry *, struct inode *);
256 extern void __d_drop(struct dentry *dentry);
257 extern void d_drop(struct dentry *dentry);
258 extern void d_delete(struct dentry *);
259
260 /* allocate/de-allocate */
261 extern struct dentry * d_alloc(struct dentry *, const struct qstr *);
262 extern struct dentry * d_alloc_anon(struct super_block *);
263 extern struct dentry * d_alloc_parallel(struct dentry *, const struct qstr *);
264 extern struct dentry * d_alloc_trylock(struct dentry *, struct qstr *);
265 extern struct dentry * d_splice_alias(struct inode *, struct dentry *);
266 struct dentry *d_duplicate(struct dentry *dentry);
267 /* weird procfs mess; *NOT* exported */
268 extern struct dentry * d_splice_alias_ops(struct inode *, struct dentry *,
269 const struct dentry_operations *);
270 extern struct dentry * d_add_ci(struct dentry *, struct inode *, struct qstr *);
271 extern bool d_same_name(const struct dentry *dentry, const struct dentry *parent,
272 const struct qstr *name);
273 extern struct dentry *d_find_any_alias(struct inode *inode);
274 extern struct dentry * d_obtain_alias(struct inode *);
275 extern struct dentry * d_obtain_root(struct inode *);
276 extern void shrink_dcache_sb(struct super_block *);
277 extern void shrink_dcache_parent(struct dentry *);
278 extern void d_invalidate(struct dentry *);
279
280 /* only used at mount-time */
281 extern struct dentry * d_make_root(struct inode *);
282
283 extern void d_mark_tmpfile(struct file *, struct inode *);
284 int d_mark_tmpfile_name(struct file *file, const struct qstr *name);
285 extern void d_tmpfile(struct file *, struct inode *);
286
287 extern struct dentry *d_find_alias(struct inode *);
288 extern void d_prune_aliases(struct inode *);
289 extern bool __move_to_shrink_list(struct dentry *, struct list_head *);
290 extern void shrink_dentry_list(struct list_head *);
291
292 extern struct dentry *d_find_alias_rcu(struct inode *);
293
294 /* test whether we have any submounts in a subdir tree */
295 extern int path_has_submounts(const struct path *);
296
297 /*
298 * This adds the entry to the hash queues.
299 */
300 extern void d_rehash(struct dentry *);
301
302 extern void d_add(struct dentry *, struct inode *);
303
304 /* used for rename() and baskets */
305 extern void d_move(struct dentry *, struct dentry *);
306 extern void d_exchange(struct dentry *, struct dentry *);
307 extern struct dentry *d_ancestor(struct dentry *, struct dentry *);
308
309 extern struct dentry *d_lookup(const struct dentry *, const struct qstr *);
310
d_count(const struct dentry * dentry)311 static inline unsigned d_count(const struct dentry *dentry)
312 {
313 return dentry->d_lockref.count;
314 }
315
316 ino_t d_parent_ino(struct dentry *dentry);
317
318 /*
319 * helper function for dentry_operations.d_dname() members
320 */
321 extern __printf(3, 4)
322 char *dynamic_dname(char *, int, const char *, ...);
323
324 extern char *__d_path(const struct path *, const struct path *, char *, int);
325 extern char *d_absolute_path(const struct path *, char *, int);
326 extern char *d_path(const struct path *, char *, int);
327 extern char *dentry_path_raw(const struct dentry *, char *, int);
328 extern char *dentry_path(const struct dentry *, char *, int);
329
330 /* Allocation counts.. */
331
332 /**
333 * dget_dlock - get a reference to a dentry
334 * @dentry: dentry to get a reference to
335 *
336 * Given a live dentry, increment the reference count and return the dentry.
337 * Caller must hold @dentry->d_lock. Making sure that dentry is alive is
338 * caller's resonsibility. There are many conditions sufficient to guarantee
339 * that; e.g. anything with non-negative refcount is alive, so's anything
340 * hashed, anything positive, anyone's parent, etc.
341 */
dget_dlock(struct dentry * dentry)342 static inline struct dentry *dget_dlock(struct dentry *dentry)
343 {
344 dentry->d_lockref.count++;
345 return dentry;
346 }
347
348
349 /**
350 * dget - get a reference to a dentry
351 * @dentry: dentry to get a reference to
352 *
353 * Given a dentry or %NULL pointer increment the reference count
354 * if appropriate and return the dentry. A dentry will not be
355 * destroyed when it has references. Conversely, a dentry with
356 * no references can disappear for any number of reasons, starting
357 * with memory pressure. In other words, that primitive is
358 * used to clone an existing reference; using it on something with
359 * zero refcount is a bug.
360 *
361 * NOTE: it will spin if @dentry->d_lock is held. From the deadlock
362 * avoidance point of view it is equivalent to spin_lock()/increment
363 * refcount/spin_unlock(), so calling it under @dentry->d_lock is
364 * always a bug; so's calling it under ->d_lock on any of its descendents.
365 *
366 */
dget(struct dentry * dentry)367 static inline struct dentry *dget(struct dentry *dentry)
368 {
369 if (dentry)
370 lockref_get(&dentry->d_lockref);
371 return dentry;
372 }
373
374 /* dentry->d_inode->i_lock must be held by caller */
dget_alias_ilocked(struct dentry * dentry)375 static inline bool dget_alias_ilocked(struct dentry *dentry)
376 {
377 if (likely(!(READ_ONCE(dentry->d_flags) & DCACHE_NORCU))) {
378 lockref_get(&dentry->d_lockref);
379 return true;
380 }
381 // NORCU dentries with zero refcount MUST NOT be grabbed
382 spin_lock(&dentry->d_lock);
383 if (dentry->d_lockref.count > 0) {
384 dget_dlock(dentry);
385 spin_unlock(&dentry->d_lock);
386 return true;
387 }
388 spin_unlock(&dentry->d_lock);
389 return false;
390 }
391
392 extern struct dentry *dget_parent(struct dentry *dentry);
393
394 /**
395 * d_unhashed - is dentry hashed
396 * @dentry: entry to check
397 *
398 * Returns true if the dentry passed is not currently hashed.
399 */
d_unhashed(const struct dentry * dentry)400 static inline int d_unhashed(const struct dentry *dentry)
401 {
402 return hlist_bl_unhashed(&dentry->d_hash);
403 }
404
d_unlinked(const struct dentry * dentry)405 static inline int d_unlinked(const struct dentry *dentry)
406 {
407 return d_unhashed(dentry) && !IS_ROOT(dentry);
408 }
409
cant_mount(const struct dentry * dentry)410 static inline int cant_mount(const struct dentry *dentry)
411 {
412 return (dentry->d_flags & DCACHE_CANT_MOUNT);
413 }
414
dont_mount(struct dentry * dentry)415 static inline void dont_mount(struct dentry *dentry)
416 {
417 spin_lock(&dentry->d_lock);
418 dentry->d_flags |= DCACHE_CANT_MOUNT;
419 spin_unlock(&dentry->d_lock);
420 }
421
422 extern void __d_lookup_unhash_wake(struct dentry *dentry);
423
d_in_lookup(const struct dentry * dentry)424 static inline int d_in_lookup(const struct dentry *dentry)
425 {
426 return dentry->d_flags & DCACHE_PAR_LOOKUP;
427 }
428
d_lookup_done(struct dentry * dentry)429 static inline void d_lookup_done(struct dentry *dentry)
430 {
431 if (unlikely(d_in_lookup(dentry)))
432 __d_lookup_unhash_wake(dentry);
433 }
434
435 extern void dput(struct dentry *);
436
d_managed(const struct dentry * dentry)437 static inline bool d_managed(const struct dentry *dentry)
438 {
439 return dentry->d_flags & DCACHE_MANAGED_DENTRY;
440 }
441
d_mountpoint(const struct dentry * dentry)442 static inline bool d_mountpoint(const struct dentry *dentry)
443 {
444 return dentry->d_flags & DCACHE_MOUNTED;
445 }
446
447 /*
448 * Directory cache entry type accessor functions.
449 */
__d_entry_type(const struct dentry * dentry)450 static inline unsigned __d_entry_type(const struct dentry *dentry)
451 {
452 return dentry->d_flags & DCACHE_ENTRY_TYPE;
453 }
454
d_is_miss(const struct dentry * dentry)455 static inline bool d_is_miss(const struct dentry *dentry)
456 {
457 return __d_entry_type(dentry) == DCACHE_MISS_TYPE;
458 }
459
d_is_whiteout(const struct dentry * dentry)460 static inline bool d_is_whiteout(const struct dentry *dentry)
461 {
462 return __d_entry_type(dentry) == DCACHE_WHITEOUT_TYPE;
463 }
464
d_can_lookup(const struct dentry * dentry)465 static inline bool d_can_lookup(const struct dentry *dentry)
466 {
467 return __d_entry_type(dentry) == DCACHE_DIRECTORY_TYPE;
468 }
469
d_is_autodir(const struct dentry * dentry)470 static inline bool d_is_autodir(const struct dentry *dentry)
471 {
472 return __d_entry_type(dentry) == DCACHE_AUTODIR_TYPE;
473 }
474
d_is_dir(const struct dentry * dentry)475 static inline bool d_is_dir(const struct dentry *dentry)
476 {
477 return d_can_lookup(dentry) || d_is_autodir(dentry);
478 }
479
d_is_symlink(const struct dentry * dentry)480 static inline bool d_is_symlink(const struct dentry *dentry)
481 {
482 return __d_entry_type(dentry) == DCACHE_SYMLINK_TYPE;
483 }
484
d_is_reg(const struct dentry * dentry)485 static inline bool d_is_reg(const struct dentry *dentry)
486 {
487 return __d_entry_type(dentry) == DCACHE_REGULAR_TYPE;
488 }
489
d_is_special(const struct dentry * dentry)490 static inline bool d_is_special(const struct dentry *dentry)
491 {
492 return __d_entry_type(dentry) == DCACHE_SPECIAL_TYPE;
493 }
494
d_is_file(const struct dentry * dentry)495 static inline bool d_is_file(const struct dentry *dentry)
496 {
497 return d_is_reg(dentry) || d_is_special(dentry);
498 }
499
d_is_negative(const struct dentry * dentry)500 static inline bool d_is_negative(const struct dentry *dentry)
501 {
502 // TODO: check d_is_whiteout(dentry) also.
503 return d_is_miss(dentry);
504 }
505
d_flags_negative(unsigned flags)506 static inline bool d_flags_negative(unsigned flags)
507 {
508 return (flags & DCACHE_ENTRY_TYPE) == DCACHE_MISS_TYPE;
509 }
510
d_is_positive(const struct dentry * dentry)511 static inline bool d_is_positive(const struct dentry *dentry)
512 {
513 return !d_is_negative(dentry);
514 }
515
516 /**
517 * d_really_is_negative - Determine if a dentry is really negative (ignoring fallthroughs)
518 * @dentry: The dentry in question
519 *
520 * Returns true if the dentry represents either an absent name or a name that
521 * doesn't map to an inode (ie. ->d_inode is NULL). The dentry could represent
522 * a true miss, a whiteout that isn't represented by a 0,0 chardev or a
523 * fallthrough marker in an opaque directory.
524 *
525 * Note! (1) This should be used *only* by a filesystem to examine its own
526 * dentries. It should not be used to look at some other filesystem's
527 * dentries. (2) It should also be used in combination with d_inode() to get
528 * the inode. (3) The dentry may have something attached to ->d_lower and the
529 * type field of the flags may be set to something other than miss or whiteout.
530 */
d_really_is_negative(const struct dentry * dentry)531 static inline bool d_really_is_negative(const struct dentry *dentry)
532 {
533 return dentry->d_inode == NULL;
534 }
535
536 /**
537 * d_really_is_positive - Determine if a dentry is really positive (ignoring fallthroughs)
538 * @dentry: The dentry in question
539 *
540 * Returns true if the dentry represents a name that maps to an inode
541 * (ie. ->d_inode is not NULL). The dentry might still represent a whiteout if
542 * that is represented on medium as a 0,0 chardev.
543 *
544 * Note! (1) This should be used *only* by a filesystem to examine its own
545 * dentries. It should not be used to look at some other filesystem's
546 * dentries. (2) It should also be used in combination with d_inode() to get
547 * the inode.
548 */
d_really_is_positive(const struct dentry * dentry)549 static inline bool d_really_is_positive(const struct dentry *dentry)
550 {
551 return dentry->d_inode != NULL;
552 }
553
simple_positive(const struct dentry * dentry)554 static inline int simple_positive(const struct dentry *dentry)
555 {
556 return d_really_is_positive(dentry) && !d_unhashed(dentry);
557 }
558
559 unsigned long vfs_pressure_ratio(unsigned long val);
560
561 /**
562 * d_lookup_release - release ownership of DCACHE_PAR_LOOKUP lock
563 * @dentry: dentry that is locked
564 *
565 * If an in-lookup dentry is to be passed to another thread which
566 * will drop the in-lookup lock, then d_lookup_release() must be called
567 * to tell lockdep that this thread no lock holds the lock. The
568 * thread that receives the lock must call d_lookup_acquire() to
569 * acquire the lock.
570 */
d_lookup_release(struct dentry * dentry)571 static inline void d_lookup_release(struct dentry *dentry)
572 {
573 if (d_in_lookup(dentry))
574 lock_map_release(&dentry->dep_map);
575 }
576
577 /**
578 * d_lookup_acquire - acquire ownership of DCACHE_PAR_LOOKUP lock
579 * @dentry: dentry that is locked
580 *
581 * If an in-lookup dentry was passed to this thread, the
582 * d_lookup_acquire() must be called to tell lockdep that this
583 * thread now owns the DCACHE_PAR_LOOKUP lock.
584 */
d_lookup_acquire(struct dentry * dentry)585 static inline void d_lookup_acquire(struct dentry *dentry)
586 {
587 if (d_in_lookup(dentry))
588 lock_map_acquire_try(&dentry->dep_map);
589 }
590
591 /**
592 * d_inode - Get the actual inode of this dentry
593 * @dentry: The dentry to query
594 *
595 * This is the helper normal filesystems should use to get at their own inodes
596 * in their own dentries and ignore the layering superimposed upon them.
597 */
d_inode(const struct dentry * dentry)598 static inline struct inode *d_inode(const struct dentry *dentry)
599 {
600 return dentry->d_inode;
601 }
602
603 /**
604 * d_inode_rcu - Get the actual inode of this dentry with READ_ONCE()
605 * @dentry: The dentry to query
606 *
607 * This is the helper normal filesystems should use to get at their own inodes
608 * in their own dentries and ignore the layering superimposed upon them.
609 */
d_inode_rcu(const struct dentry * dentry)610 static inline struct inode *d_inode_rcu(const struct dentry *dentry)
611 {
612 return READ_ONCE(dentry->d_inode);
613 }
614
615 /**
616 * d_backing_inode - Get upper or lower inode we should be using
617 * @upper: The upper layer
618 *
619 * This is the helper that should be used to get at the inode that will be used
620 * if this dentry were to be opened as a file. The inode may be on the upper
621 * dentry or it may be on a lower dentry pinned by the upper.
622 *
623 * Normal filesystems should not use this to access their own inodes.
624 */
d_backing_inode(const struct dentry * upper)625 static inline struct inode *d_backing_inode(const struct dentry *upper)
626 {
627 struct inode *inode = upper->d_inode;
628
629 return inode;
630 }
631
632 /**
633 * d_real - Return the real dentry
634 * @dentry: the dentry to query
635 * @type: the type of real dentry (data or metadata)
636 *
637 * If dentry is on a union/overlay, then return the underlying, real dentry.
638 * Otherwise return the dentry itself.
639 *
640 * See also: Documentation/filesystems/vfs.rst
641 */
d_real(struct dentry * dentry,enum d_real_type type)642 static inline struct dentry *d_real(struct dentry *dentry, enum d_real_type type)
643 {
644 if (unlikely(dentry->d_flags & DCACHE_OP_REAL))
645 return dentry->d_op->d_real(dentry, type);
646 else
647 return dentry;
648 }
649
650 /**
651 * d_real_inode - Return the real inode hosting the data
652 * @dentry: The dentry to query
653 *
654 * If dentry is on a union/overlay, then return the underlying, real inode.
655 * Otherwise return d_inode().
656 */
d_real_inode(const struct dentry * dentry)657 static inline struct inode *d_real_inode(const struct dentry *dentry)
658 {
659 /* This usage of d_real() results in const dentry */
660 return d_inode(d_real((struct dentry *) dentry, D_REAL_DATA));
661 }
662
663 struct name_snapshot {
664 struct qstr name;
665 union shortname_store inline_name;
666 };
667 void take_dentry_name_snapshot(struct name_snapshot *, struct dentry *);
668 void release_dentry_name_snapshot(struct name_snapshot *);
669
d_first_child(const struct dentry * dentry)670 static inline struct dentry *d_first_child(const struct dentry *dentry)
671 {
672 return hlist_entry_safe(dentry->d_children.first, struct dentry, d_sib);
673 }
674
d_next_sibling(const struct dentry * dentry)675 static inline struct dentry *d_next_sibling(const struct dentry *dentry)
676 {
677 return hlist_entry_safe(dentry->d_sib.next, struct dentry, d_sib);
678 }
679
680 void set_default_d_op(struct super_block *, const struct dentry_operations *);
681 struct dentry *d_make_persistent(struct dentry *, struct inode *);
682 void d_make_discardable(struct dentry *dentry);
683
684 /* inode->i_lock must be held over that */
685 #define for_each_alias(dentry, inode) \
686 hlist_for_each_entry(dentry, &(inode)->i_dentry, d_alias)
687
688 #endif /* __LINUX_DCACHE_H */
689