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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/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
18struct path;
19struct file;
20struct 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 */
49struct 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
63extern const struct qstr empty_name;
64extern const struct qstr slash_name;
65extern 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
84union 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
91struct completion_list;
92
93struct 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 union {
120 struct list_head d_lru; /* LRU list */
121 wait_queue_head_t *d_wait; /* in-lookup ones only */
122 };
123 struct hlist_node d_sib; /* child of parent list */
124 struct hlist_head d_children; /* our children */
125 /*
126 * the following members can share memory - their uses are
127 * mutually exclusive.
128 */
129 union {
130 /* positives: inode alias list */
131 struct hlist_node d_alias;
132 /* in-lookup ones (all negative, live): hash chain */
133 struct hlist_bl_node d_in_lookup_hash;
134 /* killed ones: (already negative) used to schedule freeing */
135 struct rcu_head d_rcu;
136 /*
137 * live non-in-lookup negatives: used if shrink_dcache_tree()
138 * races with eviction by another thread and needs to wait for
139 * this dentry to get killed . Remains NULL for almost all
140 * negative dentries.
141 */
142 struct completion_list *waiters;
143 };
144};
145
146/*
147 * dentry->d_lock spinlock nesting subclasses:
148 *
149 * 0: normal
150 * 1: nested
151 */
152enum dentry_d_lock_class
153{
154 DENTRY_D_LOCK_NORMAL, /* implicitly used by plain spin_lock() APIs. */
155 DENTRY_D_LOCK_NESTED
156};
157
158enum d_real_type {
159 D_REAL_DATA,
160 D_REAL_METADATA,
161};
162
163struct dentry_operations {
164 int (*d_revalidate)(struct inode *, const struct qstr *,
165 struct dentry *, unsigned int);
166 int (*d_weak_revalidate)(struct dentry *, unsigned int);
167 int (*d_hash)(const struct dentry *, struct qstr *);
168 int (*d_compare)(const struct dentry *,
169 unsigned int, const char *, const struct qstr *);
170 int (*d_delete)(const struct dentry *);
171 int (*d_init)(struct dentry *);
172 void (*d_release)(struct dentry *);
173 void (*d_prune)(struct dentry *);
174 void (*d_iput)(struct dentry *, struct inode *);
175 char *(*d_dname)(struct dentry *, char *, int);
176 struct vfsmount *(*d_automount)(struct path *);
177 int (*d_manage)(const struct path *, bool);
178 struct dentry *(*d_real)(struct dentry *, enum d_real_type type);
179 bool (*d_unalias_trylock)(const struct dentry *);
180 void (*d_unalias_unlock)(const struct dentry *);
181} ____cacheline_aligned;
182
183/*
184 * Locking rules for dentry_operations callbacks are to be found in
185 * Documentation/filesystems/locking.rst. Keep it updated!
186 *
187 * FUrther descriptions are found in Documentation/filesystems/vfs.rst.
188 * Keep it updated too!
189 */
190
191/* d_flags entries */
192enum dentry_flags {
193 DCACHE_OP_HASH = BIT(0),
194 DCACHE_OP_COMPARE = BIT(1),
195 DCACHE_OP_REVALIDATE = BIT(2),
196 DCACHE_OP_DELETE = BIT(3),
197 DCACHE_OP_PRUNE = BIT(4),
198 /*
199 * This dentry is possibly not currently connected to the dcache tree,
200 * in which case its parent will either be itself, or will have this
201 * flag as well. nfsd will not use a dentry with this bit set, but will
202 * first endeavour to clear the bit either by discovering that it is
203 * connected, or by performing lookup operations. Any filesystem which
204 * supports nfsd_operations MUST have a lookup function which, if it
205 * finds a directory inode with a DCACHE_DISCONNECTED dentry, will
206 * d_move that dentry into place and return that dentry rather than the
207 * passed one, typically using d_splice_alias.
208 */
209 DCACHE_DISCONNECTED = BIT(5),
210 DCACHE_REFERENCED = BIT(6), /* Recently used, don't discard. */
211 DCACHE_DONTCACHE = BIT(7), /* Purge from memory on final dput() */
212 DCACHE_CANT_MOUNT = BIT(8),
213 DCACHE_SHRINK_LIST = BIT(10),
214 DCACHE_OP_WEAK_REVALIDATE = BIT(11),
215 /*
216 * this dentry has been "silly renamed" and has to be deleted on the
217 * last dput()
218 */
219 DCACHE_NFSFS_RENAMED = BIT(12),
220 DCACHE_FSNOTIFY_PARENT_WATCHED = BIT(13), /* Parent inode is watched by some fsnotify listener */
221 DCACHE_DENTRY_KILLED = BIT(14),
222 DCACHE_MOUNTED = BIT(15), /* is a mountpoint */
223 DCACHE_NEED_AUTOMOUNT = BIT(16), /* handle automount on this dir */
224 DCACHE_MANAGE_TRANSIT = BIT(17), /* manage transit from this dirent */
225 DCACHE_LRU_LIST = BIT(18),
226 DCACHE_ENTRY_TYPE = (7 << 19), /* bits 19..21 are for storing type: */
227 DCACHE_MISS_TYPE = (0 << 19), /* Negative dentry */
228 DCACHE_WHITEOUT_TYPE = (1 << 19), /* Whiteout dentry (stop pathwalk) */
229 DCACHE_DIRECTORY_TYPE = (2 << 19), /* Normal directory */
230 DCACHE_AUTODIR_TYPE = (3 << 19), /* Lookupless directory (presumed automount) */
231 DCACHE_REGULAR_TYPE = (4 << 19), /* Regular file type */
232 DCACHE_SPECIAL_TYPE = (5 << 19), /* Other file type */
233 DCACHE_SYMLINK_TYPE = (6 << 19), /* Symlink */
234 DCACHE_NOKEY_NAME = BIT(22), /* Encrypted name encoded without key */
235 DCACHE_OP_REAL = BIT(23),
236 DCACHE_PAR_LOOKUP = BIT(24), /* being looked up (with parent locked shared) */
237 DCACHE_DENTRY_CURSOR = BIT(25),
238 DCACHE_NORCU = BIT(26), /* No RCU delay for freeing */
239 DCACHE_PERSISTENT = BIT(27)
240};
241
242#define DCACHE_MANAGED_DENTRY \
243 (DCACHE_MOUNTED|DCACHE_NEED_AUTOMOUNT|DCACHE_MANAGE_TRANSIT)
244
245extern seqlock_t rename_lock;
246
247/*
248 * These are the low-level FS interfaces to the dcache..
249 */
250extern void d_instantiate(struct dentry *, struct inode *);
251extern void d_instantiate_new(struct dentry *, struct inode *);
252extern void __d_drop(struct dentry *dentry);
253extern void d_drop(struct dentry *dentry);
254extern void d_delete(struct dentry *);
255
256/* allocate/de-allocate */
257extern struct dentry * d_alloc(struct dentry *, const struct qstr *);
258extern struct dentry * d_alloc_anon(struct super_block *);
259extern struct dentry * d_alloc_parallel(struct dentry *, const struct qstr *,
260 wait_queue_head_t *);
261extern struct dentry * d_splice_alias(struct inode *, struct dentry *);
262/* weird procfs mess; *NOT* exported */
263extern struct dentry * d_splice_alias_ops(struct inode *, struct dentry *,
264 const struct dentry_operations *);
265extern struct dentry * d_add_ci(struct dentry *, struct inode *, struct qstr *);
266extern bool d_same_name(const struct dentry *dentry, const struct dentry *parent,
267 const struct qstr *name);
268extern struct dentry *d_find_any_alias(struct inode *inode);
269extern struct dentry * d_obtain_alias(struct inode *);
270extern struct dentry * d_obtain_root(struct inode *);
271extern void shrink_dcache_sb(struct super_block *);
272extern void shrink_dcache_parent(struct dentry *);
273extern void d_invalidate(struct dentry *);
274
275/* only used at mount-time */
276extern struct dentry * d_make_root(struct inode *);
277
278extern void d_mark_tmpfile(struct file *, struct inode *);
279int d_mark_tmpfile_name(struct file *file, const struct qstr *name);
280extern void d_tmpfile(struct file *, struct inode *);
281
282extern struct dentry *d_find_alias(struct inode *);
283extern void d_prune_aliases(struct inode *);
284extern void d_dispose_if_unused(struct dentry *, struct list_head *);
285extern void shrink_dentry_list(struct list_head *);
286
287extern struct dentry *d_find_alias_rcu(struct inode *);
288
289/* test whether we have any submounts in a subdir tree */
290extern int path_has_submounts(const struct path *);
291
292/*
293 * This adds the entry to the hash queues.
294 */
295extern void d_rehash(struct dentry *);
296
297extern void d_add(struct dentry *, struct inode *);
298
299/* used for rename() and baskets */
300extern void d_move(struct dentry *, struct dentry *);
301extern void d_exchange(struct dentry *, struct dentry *);
302extern struct dentry *d_ancestor(struct dentry *, struct dentry *);
303
304extern struct dentry *d_lookup(const struct dentry *, const struct qstr *);
305
306static inline unsigned d_count(const struct dentry *dentry)
307{
308 return dentry->d_lockref.count;
309}
310
311ino_t d_parent_ino(struct dentry *dentry);
312
313/*
314 * helper function for dentry_operations.d_dname() members
315 */
316extern __printf(3, 4)
317char *dynamic_dname(char *, int, const char *, ...);
318
319extern char *__d_path(const struct path *, const struct path *, char *, int);
320extern char *d_absolute_path(const struct path *, char *, int);
321extern char *d_path(const struct path *, char *, int);
322extern char *dentry_path_raw(const struct dentry *, char *, int);
323extern char *dentry_path(const struct dentry *, char *, int);
324
325/* Allocation counts.. */
326
327/**
328 * dget_dlock - get a reference to a dentry
329 * @dentry: dentry to get a reference to
330 *
331 * Given a live dentry, increment the reference count and return the dentry.
332 * Caller must hold @dentry->d_lock. Making sure that dentry is alive is
333 * caller's resonsibility. There are many conditions sufficient to guarantee
334 * that; e.g. anything with non-negative refcount is alive, so's anything
335 * hashed, anything positive, anyone's parent, etc.
336 */
337static inline struct dentry *dget_dlock(struct dentry *dentry)
338{
339 dentry->d_lockref.count++;
340 return dentry;
341}
342
343
344/**
345 * dget - get a reference to a dentry
346 * @dentry: dentry to get a reference to
347 *
348 * Given a dentry or %NULL pointer increment the reference count
349 * if appropriate and return the dentry. A dentry will not be
350 * destroyed when it has references. Conversely, a dentry with
351 * no references can disappear for any number of reasons, starting
352 * with memory pressure. In other words, that primitive is
353 * used to clone an existing reference; using it on something with
354 * zero refcount is a bug.
355 *
356 * NOTE: it will spin if @dentry->d_lock is held. From the deadlock
357 * avoidance point of view it is equivalent to spin_lock()/increment
358 * refcount/spin_unlock(), so calling it under @dentry->d_lock is
359 * always a bug; so's calling it under ->d_lock on any of its descendents.
360 *
361 */
362static inline struct dentry *dget(struct dentry *dentry)
363{
364 if (dentry)
365 lockref_get(&dentry->d_lockref);
366 return dentry;
367}
368
369extern struct dentry *dget_parent(struct dentry *dentry);
370
371/**
372 * d_unhashed - is dentry hashed
373 * @dentry: entry to check
374 *
375 * Returns true if the dentry passed is not currently hashed.
376 */
377static inline int d_unhashed(const struct dentry *dentry)
378{
379 return hlist_bl_unhashed(&dentry->d_hash);
380}
381
382static inline int d_unlinked(const struct dentry *dentry)
383{
384 return d_unhashed(dentry) && !IS_ROOT(dentry);
385}
386
387static inline int cant_mount(const struct dentry *dentry)
388{
389 return (dentry->d_flags & DCACHE_CANT_MOUNT);
390}
391
392static inline void dont_mount(struct dentry *dentry)
393{
394 spin_lock(&dentry->d_lock);
395 dentry->d_flags |= DCACHE_CANT_MOUNT;
396 spin_unlock(&dentry->d_lock);
397}
398
399extern void __d_lookup_unhash_wake(struct dentry *dentry);
400
401static inline int d_in_lookup(const struct dentry *dentry)
402{
403 return dentry->d_flags & DCACHE_PAR_LOOKUP;
404}
405
406static inline void d_lookup_done(struct dentry *dentry)
407{
408 if (unlikely(d_in_lookup(dentry)))
409 __d_lookup_unhash_wake(dentry);
410}
411
412extern void dput(struct dentry *);
413
414static inline bool d_managed(const struct dentry *dentry)
415{
416 return dentry->d_flags & DCACHE_MANAGED_DENTRY;
417}
418
419static inline bool d_mountpoint(const struct dentry *dentry)
420{
421 return dentry->d_flags & DCACHE_MOUNTED;
422}
423
424/*
425 * Directory cache entry type accessor functions.
426 */
427static inline unsigned __d_entry_type(const struct dentry *dentry)
428{
429 return dentry->d_flags & DCACHE_ENTRY_TYPE;
430}
431
432static inline bool d_is_miss(const struct dentry *dentry)
433{
434 return __d_entry_type(dentry) == DCACHE_MISS_TYPE;
435}
436
437static inline bool d_is_whiteout(const struct dentry *dentry)
438{
439 return __d_entry_type(dentry) == DCACHE_WHITEOUT_TYPE;
440}
441
442static inline bool d_can_lookup(const struct dentry *dentry)
443{
444 return __d_entry_type(dentry) == DCACHE_DIRECTORY_TYPE;
445}
446
447static inline bool d_is_autodir(const struct dentry *dentry)
448{
449 return __d_entry_type(dentry) == DCACHE_AUTODIR_TYPE;
450}
451
452static inline bool d_is_dir(const struct dentry *dentry)
453{
454 return d_can_lookup(dentry) || d_is_autodir(dentry);
455}
456
457static inline bool d_is_symlink(const struct dentry *dentry)
458{
459 return __d_entry_type(dentry) == DCACHE_SYMLINK_TYPE;
460}
461
462static inline bool d_is_reg(const struct dentry *dentry)
463{
464 return __d_entry_type(dentry) == DCACHE_REGULAR_TYPE;
465}
466
467static inline bool d_is_special(const struct dentry *dentry)
468{
469 return __d_entry_type(dentry) == DCACHE_SPECIAL_TYPE;
470}
471
472static inline bool d_is_file(const struct dentry *dentry)
473{
474 return d_is_reg(dentry) || d_is_special(dentry);
475}
476
477static inline bool d_is_negative(const struct dentry *dentry)
478{
479 // TODO: check d_is_whiteout(dentry) also.
480 return d_is_miss(dentry);
481}
482
483static inline bool d_flags_negative(unsigned flags)
484{
485 return (flags & DCACHE_ENTRY_TYPE) == DCACHE_MISS_TYPE;
486}
487
488static inline bool d_is_positive(const struct dentry *dentry)
489{
490 return !d_is_negative(dentry);
491}
492
493/**
494 * d_really_is_negative - Determine if a dentry is really negative (ignoring fallthroughs)
495 * @dentry: The dentry in question
496 *
497 * Returns true if the dentry represents either an absent name or a name that
498 * doesn't map to an inode (ie. ->d_inode is NULL). The dentry could represent
499 * a true miss, a whiteout that isn't represented by a 0,0 chardev or a
500 * fallthrough marker in an opaque directory.
501 *
502 * Note! (1) This should be used *only* by a filesystem to examine its own
503 * dentries. It should not be used to look at some other filesystem's
504 * dentries. (2) It should also be used in combination with d_inode() to get
505 * the inode. (3) The dentry may have something attached to ->d_lower and the
506 * type field of the flags may be set to something other than miss or whiteout.
507 */
508static inline bool d_really_is_negative(const struct dentry *dentry)
509{
510 return dentry->d_inode == NULL;
511}
512
513/**
514 * d_really_is_positive - Determine if a dentry is really positive (ignoring fallthroughs)
515 * @dentry: The dentry in question
516 *
517 * Returns true if the dentry represents a name that maps to an inode
518 * (ie. ->d_inode is not NULL). The dentry might still represent a whiteout if
519 * that is represented on medium as a 0,0 chardev.
520 *
521 * Note! (1) This should be used *only* by a filesystem to examine its own
522 * dentries. It should not be used to look at some other filesystem's
523 * dentries. (2) It should also be used in combination with d_inode() to get
524 * the inode.
525 */
526static inline bool d_really_is_positive(const struct dentry *dentry)
527{
528 return dentry->d_inode != NULL;
529}
530
531static inline int simple_positive(const struct dentry *dentry)
532{
533 return d_really_is_positive(dentry) && !d_unhashed(dentry);
534}
535
536unsigned long vfs_pressure_ratio(unsigned long val);
537
538/**
539 * d_inode - Get the actual inode of this dentry
540 * @dentry: The dentry to query
541 *
542 * This is the helper normal filesystems should use to get at their own inodes
543 * in their own dentries and ignore the layering superimposed upon them.
544 */
545static inline struct inode *d_inode(const struct dentry *dentry)
546{
547 return dentry->d_inode;
548}
549
550/**
551 * d_inode_rcu - Get the actual inode of this dentry with READ_ONCE()
552 * @dentry: The dentry to query
553 *
554 * This is the helper normal filesystems should use to get at their own inodes
555 * in their own dentries and ignore the layering superimposed upon them.
556 */
557static inline struct inode *d_inode_rcu(const struct dentry *dentry)
558{
559 return READ_ONCE(dentry->d_inode);
560}
561
562/**
563 * d_backing_inode - Get upper or lower inode we should be using
564 * @upper: The upper layer
565 *
566 * This is the helper that should be used to get at the inode that will be used
567 * if this dentry were to be opened as a file. The inode may be on the upper
568 * dentry or it may be on a lower dentry pinned by the upper.
569 *
570 * Normal filesystems should not use this to access their own inodes.
571 */
572static inline struct inode *d_backing_inode(const struct dentry *upper)
573{
574 struct inode *inode = upper->d_inode;
575
576 return inode;
577}
578
579/**
580 * d_real - Return the real dentry
581 * @dentry: the dentry to query
582 * @type: the type of real dentry (data or metadata)
583 *
584 * If dentry is on a union/overlay, then return the underlying, real dentry.
585 * Otherwise return the dentry itself.
586 *
587 * See also: Documentation/filesystems/vfs.rst
588 */
589static inline struct dentry *d_real(struct dentry *dentry, enum d_real_type type)
590{
591 if (unlikely(dentry->d_flags & DCACHE_OP_REAL))
592 return dentry->d_op->d_real(dentry, type);
593 else
594 return dentry;
595}
596
597/**
598 * d_real_inode - Return the real inode hosting the data
599 * @dentry: The dentry to query
600 *
601 * If dentry is on a union/overlay, then return the underlying, real inode.
602 * Otherwise return d_inode().
603 */
604static inline struct inode *d_real_inode(const struct dentry *dentry)
605{
606 /* This usage of d_real() results in const dentry */
607 return d_inode(d_real((struct dentry *) dentry, D_REAL_DATA));
608}
609
610struct name_snapshot {
611 struct qstr name;
612 union shortname_store inline_name;
613};
614void take_dentry_name_snapshot(struct name_snapshot *, struct dentry *);
615void release_dentry_name_snapshot(struct name_snapshot *);
616
617static inline struct dentry *d_first_child(const struct dentry *dentry)
618{
619 return hlist_entry_safe(dentry->d_children.first, struct dentry, d_sib);
620}
621
622static inline struct dentry *d_next_sibling(const struct dentry *dentry)
623{
624 return hlist_entry_safe(dentry->d_sib.next, struct dentry, d_sib);
625}
626
627void set_default_d_op(struct super_block *, const struct dentry_operations *);
628struct dentry *d_make_persistent(struct dentry *, struct inode *);
629void d_make_discardable(struct dentry *dentry);
630
631/* inode->i_lock must be held over that */
632#define for_each_alias(dentry, inode) \
633 hlist_for_each_entry(dentry, &(inode)->i_dentry, d_alias)
634
635#endif /* __LINUX_DCACHE_H */