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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 vfsmount;
20
21/*
22 * linux/include/linux/dcache.h
23 *
24 * Dirent cache data structures
25 *
26 * (C) Copyright 1997 Thomas Schoebel-Theuer,
27 * with heavy changes by Linus Torvalds
28 */
29
30#define IS_ROOT(x) ((x) == (x)->d_parent)
31
32/* The hash is always the low bits of hash_len */
33#ifdef __LITTLE_ENDIAN
34 #define HASH_LEN_DECLARE u32 hash; u32 len
35 #define bytemask_from_count(cnt) (~(~0ul << (cnt)*8))
36#else
37 #define HASH_LEN_DECLARE u32 len; u32 hash
38 #define bytemask_from_count(cnt) (~(~0ul >> (cnt)*8))
39#endif
40
41/*
42 * "quick string" -- eases parameter passing, but more importantly
43 * saves "metadata" about the string (ie length and the hash).
44 *
45 * hash comes first so it snuggles against d_parent in the
46 * dentry.
47 */
48struct qstr {
49 union {
50 struct {
51 HASH_LEN_DECLARE;
52 };
53 u64 hash_len;
54 };
55 const unsigned char *name;
56};
57
58#define QSTR_INIT(n,l) { { { .len = l } }, .name = n }
59
60extern const struct qstr empty_name;
61extern const struct qstr slash_name;
62extern const struct qstr dotdot_name;
63
64struct dentry_stat_t {
65 long nr_dentry;
66 long nr_unused;
67 long age_limit; /* age in seconds */
68 long want_pages; /* pages requested by system */
69 long nr_negative; /* # of unused negative dentries */
70 long dummy; /* Reserved for future use */
71};
72extern struct dentry_stat_t dentry_stat;
73
74/*
75 * Try to keep struct dentry aligned on 64 byte cachelines (this will
76 * give reasonable cacheline footprint with larger lines without the
77 * large memory footprint increase).
78 */
79#ifdef CONFIG_64BIT
80# define DNAME_INLINE_LEN 32 /* 192 bytes */
81#else
82# ifdef CONFIG_SMP
83# define DNAME_INLINE_LEN 36 /* 128 bytes */
84# else
85# define DNAME_INLINE_LEN 40 /* 128 bytes */
86# endif
87#endif
88
89#define d_lock d_lockref.lock
90
91struct dentry {
92 /* RCU lookup touched fields */
93 unsigned int d_flags; /* protected by d_lock */
94 seqcount_spinlock_t d_seq; /* per dentry seqlock */
95 struct hlist_bl_node d_hash; /* lookup hash list */
96 struct dentry *d_parent; /* parent directory */
97 struct qstr d_name;
98 struct inode *d_inode; /* Where the name belongs to - NULL is
99 * negative */
100 unsigned char d_iname[DNAME_INLINE_LEN]; /* small names */
101
102 /* Ref lookup also touches following */
103 struct lockref d_lockref; /* per-dentry lock and refcount */
104 const struct dentry_operations *d_op;
105 struct super_block *d_sb; /* The root of the dentry tree */
106 unsigned long d_time; /* used by d_revalidate */
107 void *d_fsdata; /* fs-specific data */
108
109 union {
110 struct list_head d_lru; /* LRU list */
111 wait_queue_head_t *d_wait; /* in-lookup ones only */
112 };
113 struct list_head d_child; /* child of parent list */
114 struct list_head d_subdirs; /* our children */
115 /*
116 * d_alias and d_rcu can share memory
117 */
118 union {
119 struct hlist_node d_alias; /* inode alias list */
120 struct hlist_bl_node d_in_lookup_hash; /* only for in-lookup ones */
121 struct rcu_head d_rcu;
122 } d_u;
123} __randomize_layout;
124
125/*
126 * dentry->d_lock spinlock nesting subclasses:
127 *
128 * 0: normal
129 * 1: nested
130 */
131enum dentry_d_lock_class
132{
133 DENTRY_D_LOCK_NORMAL, /* implicitly used by plain spin_lock() APIs. */
134 DENTRY_D_LOCK_NESTED
135};
136
137struct dentry_operations {
138 int (*d_revalidate)(struct dentry *, unsigned int);
139 int (*d_weak_revalidate)(struct dentry *, unsigned int);
140 int (*d_hash)(const struct dentry *, struct qstr *);
141 int (*d_compare)(const struct dentry *,
142 unsigned int, const char *, const struct qstr *);
143 int (*d_delete)(const struct dentry *);
144 int (*d_init)(struct dentry *);
145 void (*d_release)(struct dentry *);
146 void (*d_prune)(struct dentry *);
147 void (*d_iput)(struct dentry *, struct inode *);
148 char *(*d_dname)(struct dentry *, char *, int);
149 struct vfsmount *(*d_automount)(struct path *);
150 int (*d_manage)(const struct path *, bool);
151 struct dentry *(*d_real)(struct dentry *, const struct inode *);
152} ____cacheline_aligned;
153
154/*
155 * Locking rules for dentry_operations callbacks are to be found in
156 * Documentation/filesystems/locking.rst. Keep it updated!
157 *
158 * FUrther descriptions are found in Documentation/filesystems/vfs.rst.
159 * Keep it updated too!
160 */
161
162/* d_flags entries */
163#define DCACHE_OP_HASH 0x00000001
164#define DCACHE_OP_COMPARE 0x00000002
165#define DCACHE_OP_REVALIDATE 0x00000004
166#define DCACHE_OP_DELETE 0x00000008
167#define DCACHE_OP_PRUNE 0x00000010
168
169#define DCACHE_DISCONNECTED 0x00000020
170 /* This dentry is possibly not currently connected to the dcache tree, in
171 * which case its parent will either be itself, or will have this flag as
172 * well. nfsd will not use a dentry with this bit set, but will first
173 * endeavour to clear the bit either by discovering that it is connected,
174 * or by performing lookup operations. Any filesystem which supports
175 * nfsd_operations MUST have a lookup function which, if it finds a
176 * directory inode with a DCACHE_DISCONNECTED dentry, will d_move that
177 * dentry into place and return that dentry rather than the passed one,
178 * typically using d_splice_alias. */
179
180#define DCACHE_REFERENCED 0x00000040 /* Recently used, don't discard. */
181
182#define DCACHE_DONTCACHE 0x00000080 /* Purge from memory on final dput() */
183
184#define DCACHE_CANT_MOUNT 0x00000100
185#define DCACHE_GENOCIDE 0x00000200
186#define DCACHE_SHRINK_LIST 0x00000400
187
188#define DCACHE_OP_WEAK_REVALIDATE 0x00000800
189
190#define DCACHE_NFSFS_RENAMED 0x00001000
191 /* this dentry has been "silly renamed" and has to be deleted on the last
192 * dput() */
193#define DCACHE_COOKIE 0x00002000 /* For use by dcookie subsystem */
194#define DCACHE_FSNOTIFY_PARENT_WATCHED 0x00004000
195 /* Parent inode is watched by some fsnotify listener */
196
197#define DCACHE_DENTRY_KILLED 0x00008000
198
199#define DCACHE_MOUNTED 0x00010000 /* is a mountpoint */
200#define DCACHE_NEED_AUTOMOUNT 0x00020000 /* handle automount on this dir */
201#define DCACHE_MANAGE_TRANSIT 0x00040000 /* manage transit from this dirent */
202#define DCACHE_MANAGED_DENTRY \
203 (DCACHE_MOUNTED|DCACHE_NEED_AUTOMOUNT|DCACHE_MANAGE_TRANSIT)
204
205#define DCACHE_LRU_LIST 0x00080000
206
207#define DCACHE_ENTRY_TYPE 0x00700000
208#define DCACHE_MISS_TYPE 0x00000000 /* Negative dentry (maybe fallthru to nowhere) */
209#define DCACHE_WHITEOUT_TYPE 0x00100000 /* Whiteout dentry (stop pathwalk) */
210#define DCACHE_DIRECTORY_TYPE 0x00200000 /* Normal directory */
211#define DCACHE_AUTODIR_TYPE 0x00300000 /* Lookupless directory (presumed automount) */
212#define DCACHE_REGULAR_TYPE 0x00400000 /* Regular file type (or fallthru to such) */
213#define DCACHE_SPECIAL_TYPE 0x00500000 /* Other file type (or fallthru to such) */
214#define DCACHE_SYMLINK_TYPE 0x00600000 /* Symlink (or fallthru to such) */
215
216#define DCACHE_MAY_FREE 0x00800000
217#define DCACHE_FALLTHRU 0x01000000 /* Fall through to lower layer */
218#define DCACHE_NOKEY_NAME 0x02000000 /* Encrypted name encoded without key */
219#define DCACHE_OP_REAL 0x04000000
220
221#define DCACHE_PAR_LOOKUP 0x10000000 /* being looked up (with parent locked shared) */
222#define DCACHE_DENTRY_CURSOR 0x20000000
223#define DCACHE_NORCU 0x40000000 /* No RCU delay for freeing */
224
225extern seqlock_t rename_lock;
226
227/*
228 * These are the low-level FS interfaces to the dcache..
229 */
230extern void d_instantiate(struct dentry *, struct inode *);
231extern void d_instantiate_new(struct dentry *, struct inode *);
232extern struct dentry * d_instantiate_unique(struct dentry *, struct inode *);
233extern struct dentry * d_instantiate_anon(struct dentry *, struct inode *);
234extern void __d_drop(struct dentry *dentry);
235extern void d_drop(struct dentry *dentry);
236extern void d_delete(struct dentry *);
237extern void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op);
238
239/* allocate/de-allocate */
240extern struct dentry * d_alloc(struct dentry *, const struct qstr *);
241extern struct dentry * d_alloc_anon(struct super_block *);
242extern struct dentry * d_alloc_parallel(struct dentry *, const struct qstr *,
243 wait_queue_head_t *);
244extern struct dentry * d_splice_alias(struct inode *, struct dentry *);
245extern struct dentry * d_add_ci(struct dentry *, struct inode *, struct qstr *);
246extern struct dentry * d_exact_alias(struct dentry *, struct inode *);
247extern struct dentry *d_find_any_alias(struct inode *inode);
248extern struct dentry * d_obtain_alias(struct inode *);
249extern struct dentry * d_obtain_root(struct inode *);
250extern void shrink_dcache_sb(struct super_block *);
251extern void shrink_dcache_parent(struct dentry *);
252extern void shrink_dcache_for_umount(struct super_block *);
253extern void d_invalidate(struct dentry *);
254
255/* only used at mount-time */
256extern struct dentry * d_make_root(struct inode *);
257
258/* <clickety>-<click> the ramfs-type tree */
259extern void d_genocide(struct dentry *);
260
261extern void d_tmpfile(struct dentry *, struct inode *);
262
263extern struct dentry *d_find_alias(struct inode *);
264extern void d_prune_aliases(struct inode *);
265
266extern struct dentry *d_find_alias_rcu(struct inode *);
267
268/* test whether we have any submounts in a subdir tree */
269extern int path_has_submounts(const struct path *);
270
271/*
272 * This adds the entry to the hash queues.
273 */
274extern void d_rehash(struct dentry *);
275
276extern void d_add(struct dentry *, struct inode *);
277
278/* used for rename() and baskets */
279extern void d_move(struct dentry *, struct dentry *);
280extern void d_exchange(struct dentry *, struct dentry *);
281extern struct dentry *d_ancestor(struct dentry *, struct dentry *);
282
283/* appendix may either be NULL or be used for transname suffixes */
284extern struct dentry *d_lookup(const struct dentry *, const struct qstr *);
285extern struct dentry *d_hash_and_lookup(struct dentry *, struct qstr *);
286extern struct dentry *__d_lookup(const struct dentry *, const struct qstr *);
287extern struct dentry *__d_lookup_rcu(const struct dentry *parent,
288 const struct qstr *name, unsigned *seq);
289
290static inline unsigned d_count(const struct dentry *dentry)
291{
292 return dentry->d_lockref.count;
293}
294
295/*
296 * helper function for dentry_operations.d_dname() members
297 */
298extern __printf(4, 5)
299char *dynamic_dname(struct dentry *, char *, int, const char *, ...);
300
301extern char *__d_path(const struct path *, const struct path *, char *, int);
302extern char *d_absolute_path(const struct path *, char *, int);
303extern char *d_path(const struct path *, char *, int);
304extern char *dentry_path_raw(const struct dentry *, char *, int);
305extern char *dentry_path(const struct dentry *, char *, int);
306
307/* Allocation counts.. */
308
309/**
310 * dget, dget_dlock - get a reference to a dentry
311 * @dentry: dentry to get a reference to
312 *
313 * Given a dentry or %NULL pointer increment the reference count
314 * if appropriate and return the dentry. A dentry will not be
315 * destroyed when it has references.
316 */
317static inline struct dentry *dget_dlock(struct dentry *dentry)
318{
319 if (dentry)
320 dentry->d_lockref.count++;
321 return dentry;
322}
323
324static inline struct dentry *dget(struct dentry *dentry)
325{
326 if (dentry)
327 lockref_get(&dentry->d_lockref);
328 return dentry;
329}
330
331extern struct dentry *dget_parent(struct dentry *dentry);
332
333/**
334 * d_unhashed - is dentry hashed
335 * @dentry: entry to check
336 *
337 * Returns true if the dentry passed is not currently hashed.
338 */
339
340static inline int d_unhashed(const struct dentry *dentry)
341{
342 return hlist_bl_unhashed(&dentry->d_hash);
343}
344
345static inline int d_unlinked(const struct dentry *dentry)
346{
347 return d_unhashed(dentry) && !IS_ROOT(dentry);
348}
349
350static inline int cant_mount(const struct dentry *dentry)
351{
352 return (dentry->d_flags & DCACHE_CANT_MOUNT);
353}
354
355static inline void dont_mount(struct dentry *dentry)
356{
357 spin_lock(&dentry->d_lock);
358 dentry->d_flags |= DCACHE_CANT_MOUNT;
359 spin_unlock(&dentry->d_lock);
360}
361
362extern void __d_lookup_done(struct dentry *);
363
364static inline int d_in_lookup(const struct dentry *dentry)
365{
366 return dentry->d_flags & DCACHE_PAR_LOOKUP;
367}
368
369static inline void d_lookup_done(struct dentry *dentry)
370{
371 if (unlikely(d_in_lookup(dentry))) {
372 spin_lock(&dentry->d_lock);
373 __d_lookup_done(dentry);
374 spin_unlock(&dentry->d_lock);
375 }
376}
377
378extern void dput(struct dentry *);
379
380static inline bool d_managed(const struct dentry *dentry)
381{
382 return dentry->d_flags & DCACHE_MANAGED_DENTRY;
383}
384
385static inline bool d_mountpoint(const struct dentry *dentry)
386{
387 return dentry->d_flags & DCACHE_MOUNTED;
388}
389
390/*
391 * Directory cache entry type accessor functions.
392 */
393static inline unsigned __d_entry_type(const struct dentry *dentry)
394{
395 return dentry->d_flags & DCACHE_ENTRY_TYPE;
396}
397
398static inline bool d_is_miss(const struct dentry *dentry)
399{
400 return __d_entry_type(dentry) == DCACHE_MISS_TYPE;
401}
402
403static inline bool d_is_whiteout(const struct dentry *dentry)
404{
405 return __d_entry_type(dentry) == DCACHE_WHITEOUT_TYPE;
406}
407
408static inline bool d_can_lookup(const struct dentry *dentry)
409{
410 return __d_entry_type(dentry) == DCACHE_DIRECTORY_TYPE;
411}
412
413static inline bool d_is_autodir(const struct dentry *dentry)
414{
415 return __d_entry_type(dentry) == DCACHE_AUTODIR_TYPE;
416}
417
418static inline bool d_is_dir(const struct dentry *dentry)
419{
420 return d_can_lookup(dentry) || d_is_autodir(dentry);
421}
422
423static inline bool d_is_symlink(const struct dentry *dentry)
424{
425 return __d_entry_type(dentry) == DCACHE_SYMLINK_TYPE;
426}
427
428static inline bool d_is_reg(const struct dentry *dentry)
429{
430 return __d_entry_type(dentry) == DCACHE_REGULAR_TYPE;
431}
432
433static inline bool d_is_special(const struct dentry *dentry)
434{
435 return __d_entry_type(dentry) == DCACHE_SPECIAL_TYPE;
436}
437
438static inline bool d_is_file(const struct dentry *dentry)
439{
440 return d_is_reg(dentry) || d_is_special(dentry);
441}
442
443static inline bool d_is_negative(const struct dentry *dentry)
444{
445 // TODO: check d_is_whiteout(dentry) also.
446 return d_is_miss(dentry);
447}
448
449static inline bool d_flags_negative(unsigned flags)
450{
451 return (flags & DCACHE_ENTRY_TYPE) == DCACHE_MISS_TYPE;
452}
453
454static inline bool d_is_positive(const struct dentry *dentry)
455{
456 return !d_is_negative(dentry);
457}
458
459/**
460 * d_really_is_negative - Determine if a dentry is really negative (ignoring fallthroughs)
461 * @dentry: The dentry in question
462 *
463 * Returns true if the dentry represents either an absent name or a name that
464 * doesn't map to an inode (ie. ->d_inode is NULL). The dentry could represent
465 * a true miss, a whiteout that isn't represented by a 0,0 chardev or a
466 * fallthrough marker in an opaque directory.
467 *
468 * Note! (1) This should be used *only* by a filesystem to examine its own
469 * dentries. It should not be used to look at some other filesystem's
470 * dentries. (2) It should also be used in combination with d_inode() to get
471 * the inode. (3) The dentry may have something attached to ->d_lower and the
472 * type field of the flags may be set to something other than miss or whiteout.
473 */
474static inline bool d_really_is_negative(const struct dentry *dentry)
475{
476 return dentry->d_inode == NULL;
477}
478
479/**
480 * d_really_is_positive - Determine if a dentry is really positive (ignoring fallthroughs)
481 * @dentry: The dentry in question
482 *
483 * Returns true if the dentry represents a name that maps to an inode
484 * (ie. ->d_inode is not NULL). The dentry might still represent a whiteout if
485 * that is represented on medium as a 0,0 chardev.
486 *
487 * Note! (1) This should be used *only* by a filesystem to examine its own
488 * dentries. It should not be used to look at some other filesystem's
489 * dentries. (2) It should also be used in combination with d_inode() to get
490 * the inode.
491 */
492static inline bool d_really_is_positive(const struct dentry *dentry)
493{
494 return dentry->d_inode != NULL;
495}
496
497static inline int simple_positive(const struct dentry *dentry)
498{
499 return d_really_is_positive(dentry) && !d_unhashed(dentry);
500}
501
502extern void d_set_fallthru(struct dentry *dentry);
503
504static inline bool d_is_fallthru(const struct dentry *dentry)
505{
506 return dentry->d_flags & DCACHE_FALLTHRU;
507}
508
509
510extern int sysctl_vfs_cache_pressure;
511
512static inline unsigned long vfs_pressure_ratio(unsigned long val)
513{
514 return mult_frac(val, sysctl_vfs_cache_pressure, 100);
515}
516
517/**
518 * d_inode - Get the actual inode of this dentry
519 * @dentry: The dentry to query
520 *
521 * This is the helper normal filesystems should use to get at their own inodes
522 * in their own dentries and ignore the layering superimposed upon them.
523 */
524static inline struct inode *d_inode(const struct dentry *dentry)
525{
526 return dentry->d_inode;
527}
528
529/**
530 * d_inode_rcu - Get the actual inode of this dentry with READ_ONCE()
531 * @dentry: The dentry to query
532 *
533 * This is the helper normal filesystems should use to get at their own inodes
534 * in their own dentries and ignore the layering superimposed upon them.
535 */
536static inline struct inode *d_inode_rcu(const struct dentry *dentry)
537{
538 return READ_ONCE(dentry->d_inode);
539}
540
541/**
542 * d_backing_inode - Get upper or lower inode we should be using
543 * @upper: The upper layer
544 *
545 * This is the helper that should be used to get at the inode that will be used
546 * if this dentry were to be opened as a file. The inode may be on the upper
547 * dentry or it may be on a lower dentry pinned by the upper.
548 *
549 * Normal filesystems should not use this to access their own inodes.
550 */
551static inline struct inode *d_backing_inode(const struct dentry *upper)
552{
553 struct inode *inode = upper->d_inode;
554
555 return inode;
556}
557
558/**
559 * d_backing_dentry - Get upper or lower dentry we should be using
560 * @upper: The upper layer
561 *
562 * This is the helper that should be used to get the dentry of the inode that
563 * will be used if this dentry were opened as a file. It may be the upper
564 * dentry or it may be a lower dentry pinned by the upper.
565 *
566 * Normal filesystems should not use this to access their own dentries.
567 */
568static inline struct dentry *d_backing_dentry(struct dentry *upper)
569{
570 return upper;
571}
572
573/**
574 * d_real - Return the real dentry
575 * @dentry: the dentry to query
576 * @inode: inode to select the dentry from multiple layers (can be NULL)
577 *
578 * If dentry is on a union/overlay, then return the underlying, real dentry.
579 * Otherwise return the dentry itself.
580 *
581 * See also: Documentation/filesystems/vfs.rst
582 */
583static inline struct dentry *d_real(struct dentry *dentry,
584 const struct inode *inode)
585{
586 if (unlikely(dentry->d_flags & DCACHE_OP_REAL))
587 return dentry->d_op->d_real(dentry, inode);
588 else
589 return dentry;
590}
591
592/**
593 * d_real_inode - Return the real inode
594 * @dentry: The dentry to query
595 *
596 * If dentry is on a union/overlay, then return the underlying, real inode.
597 * Otherwise return d_inode().
598 */
599static inline struct inode *d_real_inode(const struct dentry *dentry)
600{
601 /* This usage of d_real() results in const dentry */
602 return d_backing_inode(d_real((struct dentry *) dentry, NULL));
603}
604
605struct name_snapshot {
606 struct qstr name;
607 unsigned char inline_name[DNAME_INLINE_LEN];
608};
609void take_dentry_name_snapshot(struct name_snapshot *, struct dentry *);
610void release_dentry_name_snapshot(struct name_snapshot *);
611
612#endif /* __LINUX_DCACHE_H */
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
17struct path;
18struct 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 */
47struct 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
59extern const struct qstr empty_name;
60extern const struct qstr slash_name;
61
62struct 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};
70extern 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
89struct 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 */
129enum dentry_d_lock_class
130{
131 DENTRY_D_LOCK_NORMAL, /* implicitly used by plain spin_lock() APIs. */
132 DENTRY_D_LOCK_NESTED
133};
134
135struct 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
221extern seqlock_t rename_lock;
222
223/*
224 * These are the low-level FS interfaces to the dcache..
225 */
226extern void d_instantiate(struct dentry *, struct inode *);
227extern void d_instantiate_new(struct dentry *, struct inode *);
228extern struct dentry * d_instantiate_unique(struct dentry *, struct inode *);
229extern struct dentry * d_instantiate_anon(struct dentry *, struct inode *);
230extern void __d_drop(struct dentry *dentry);
231extern void d_drop(struct dentry *dentry);
232extern void d_delete(struct dentry *);
233extern void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op);
234
235/* allocate/de-allocate */
236extern struct dentry * d_alloc(struct dentry *, const struct qstr *);
237extern struct dentry * d_alloc_anon(struct super_block *);
238extern struct dentry * d_alloc_parallel(struct dentry *, const struct qstr *,
239 wait_queue_head_t *);
240extern struct dentry * d_splice_alias(struct inode *, struct dentry *);
241extern struct dentry * d_add_ci(struct dentry *, struct inode *, struct qstr *);
242extern struct dentry * d_exact_alias(struct dentry *, struct inode *);
243extern struct dentry *d_find_any_alias(struct inode *inode);
244extern struct dentry * d_obtain_alias(struct inode *);
245extern struct dentry * d_obtain_root(struct inode *);
246extern void shrink_dcache_sb(struct super_block *);
247extern void shrink_dcache_parent(struct dentry *);
248extern void shrink_dcache_for_umount(struct super_block *);
249extern void d_invalidate(struct dentry *);
250
251/* only used at mount-time */
252extern struct dentry * d_make_root(struct inode *);
253
254/* <clickety>-<click> the ramfs-type tree */
255extern void d_genocide(struct dentry *);
256
257extern void d_tmpfile(struct dentry *, struct inode *);
258
259extern struct dentry *d_find_alias(struct inode *);
260extern void d_prune_aliases(struct inode *);
261
262/* test whether we have any submounts in a subdir tree */
263extern int path_has_submounts(const struct path *);
264
265/*
266 * This adds the entry to the hash queues.
267 */
268extern void d_rehash(struct dentry *);
269
270extern void d_add(struct dentry *, struct inode *);
271
272/* used for rename() and baskets */
273extern void d_move(struct dentry *, struct dentry *);
274extern void d_exchange(struct dentry *, struct dentry *);
275extern struct dentry *d_ancestor(struct dentry *, struct dentry *);
276
277/* appendix may either be NULL or be used for transname suffixes */
278extern struct dentry *d_lookup(const struct dentry *, const struct qstr *);
279extern struct dentry *d_hash_and_lookup(struct dentry *, struct qstr *);
280extern struct dentry *__d_lookup(const struct dentry *, const struct qstr *);
281extern struct dentry *__d_lookup_rcu(const struct dentry *parent,
282 const struct qstr *name, unsigned *seq);
283
284static 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 */
292extern __printf(4, 5)
293char *dynamic_dname(struct dentry *, char *, int, const char *, ...);
294
295extern char *__d_path(const struct path *, const struct path *, char *, int);
296extern char *d_absolute_path(const struct path *, char *, int);
297extern char *d_path(const struct path *, char *, int);
298extern char *dentry_path_raw(struct dentry *, char *, int);
299extern 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 */
311static inline struct dentry *dget_dlock(struct dentry *dentry)
312{
313 if (dentry)
314 dentry->d_lockref.count++;
315 return dentry;
316}
317
318static inline struct dentry *dget(struct dentry *dentry)
319{
320 if (dentry)
321 lockref_get(&dentry->d_lockref);
322 return dentry;
323}
324
325extern 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
334static inline int d_unhashed(const struct dentry *dentry)
335{
336 return hlist_bl_unhashed(&dentry->d_hash);
337}
338
339static inline int d_unlinked(const struct dentry *dentry)
340{
341 return d_unhashed(dentry) && !IS_ROOT(dentry);
342}
343
344static inline int cant_mount(const struct dentry *dentry)
345{
346 return (dentry->d_flags & DCACHE_CANT_MOUNT);
347}
348
349static inline void dont_mount(struct dentry *dentry)
350{
351 spin_lock(&dentry->d_lock);
352 dentry->d_flags |= DCACHE_CANT_MOUNT;
353 spin_unlock(&dentry->d_lock);
354}
355
356extern void __d_lookup_done(struct dentry *);
357
358static inline int d_in_lookup(const struct dentry *dentry)
359{
360 return dentry->d_flags & DCACHE_PAR_LOOKUP;
361}
362
363static inline void d_lookup_done(struct dentry *dentry)
364{
365 if (unlikely(d_in_lookup(dentry))) {
366 spin_lock(&dentry->d_lock);
367 __d_lookup_done(dentry);
368 spin_unlock(&dentry->d_lock);
369 }
370}
371
372extern void dput(struct dentry *);
373
374static inline bool d_managed(const struct dentry *dentry)
375{
376 return dentry->d_flags & DCACHE_MANAGED_DENTRY;
377}
378
379static inline bool d_mountpoint(const struct dentry *dentry)
380{
381 return dentry->d_flags & DCACHE_MOUNTED;
382}
383
384/*
385 * Directory cache entry type accessor functions.
386 */
387static inline unsigned __d_entry_type(const struct dentry *dentry)
388{
389 return dentry->d_flags & DCACHE_ENTRY_TYPE;
390}
391
392static inline bool d_is_miss(const struct dentry *dentry)
393{
394 return __d_entry_type(dentry) == DCACHE_MISS_TYPE;
395}
396
397static inline bool d_is_whiteout(const struct dentry *dentry)
398{
399 return __d_entry_type(dentry) == DCACHE_WHITEOUT_TYPE;
400}
401
402static inline bool d_can_lookup(const struct dentry *dentry)
403{
404 return __d_entry_type(dentry) == DCACHE_DIRECTORY_TYPE;
405}
406
407static inline bool d_is_autodir(const struct dentry *dentry)
408{
409 return __d_entry_type(dentry) == DCACHE_AUTODIR_TYPE;
410}
411
412static inline bool d_is_dir(const struct dentry *dentry)
413{
414 return d_can_lookup(dentry) || d_is_autodir(dentry);
415}
416
417static inline bool d_is_symlink(const struct dentry *dentry)
418{
419 return __d_entry_type(dentry) == DCACHE_SYMLINK_TYPE;
420}
421
422static inline bool d_is_reg(const struct dentry *dentry)
423{
424 return __d_entry_type(dentry) == DCACHE_REGULAR_TYPE;
425}
426
427static inline bool d_is_special(const struct dentry *dentry)
428{
429 return __d_entry_type(dentry) == DCACHE_SPECIAL_TYPE;
430}
431
432static inline bool d_is_file(const struct dentry *dentry)
433{
434 return d_is_reg(dentry) || d_is_special(dentry);
435}
436
437static 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
443static inline bool d_is_positive(const struct dentry *dentry)
444{
445 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 */
463static inline bool d_really_is_negative(const struct dentry *dentry)
464{
465 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 */
481static inline bool d_really_is_positive(const struct dentry *dentry)
482{
483 return dentry->d_inode != NULL;
484}
485
486static inline int simple_positive(const struct dentry *dentry)
487{
488 return d_really_is_positive(dentry) && !d_unhashed(dentry);
489}
490
491extern void d_set_fallthru(struct dentry *dentry);
492
493static inline bool d_is_fallthru(const struct dentry *dentry)
494{
495 return dentry->d_flags & DCACHE_FALLTHRU;
496}
497
498
499extern int sysctl_vfs_cache_pressure;
500
501static inline unsigned long vfs_pressure_ratio(unsigned long val)
502{
503 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 */
513static inline struct inode *d_inode(const struct dentry *dentry)
514{
515 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 */
525static inline struct inode *d_inode_rcu(const struct dentry *dentry)
526{
527 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 */
540static inline struct inode *d_backing_inode(const struct dentry *upper)
541{
542 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 */
557static 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 */
572static inline struct dentry *d_real(struct dentry *dentry,
573 const struct inode *inode)
574{
575 if (unlikely(dentry->d_flags & DCACHE_OP_REAL))
576 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 */
588static 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
594struct name_snapshot {
595 struct qstr name;
596 unsigned char inline_name[DNAME_INLINE_LEN];
597};
598void take_dentry_name_snapshot(struct name_snapshot *, struct dentry *);
599void release_dentry_name_snapshot(struct name_snapshot *);
600
601#endif /* __LINUX_DCACHE_H */