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. Keep it updated!
155 *
156 * FUrther descriptions are found in Documentation/filesystems/vfs.txt.
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#define DCACHE_RCUACCESS 0x00000080 /* Entry has ever been RCU-visible */
180
181#define DCACHE_CANT_MOUNT 0x00000100
182#define DCACHE_GENOCIDE 0x00000200
183#define DCACHE_SHRINK_LIST 0x00000400
184
185#define DCACHE_OP_WEAK_REVALIDATE 0x00000800
186
187#define DCACHE_NFSFS_RENAMED 0x00001000
188 /* this dentry has been "silly renamed" and has to be deleted on the last
189 * dput() */
190#define DCACHE_COOKIE 0x00002000 /* For use by dcookie subsystem */
191#define DCACHE_FSNOTIFY_PARENT_WATCHED 0x00004000
192 /* Parent inode is watched by some fsnotify listener */
193
194#define DCACHE_DENTRY_KILLED 0x00008000
195
196#define DCACHE_MOUNTED 0x00010000 /* is a mountpoint */
197#define DCACHE_NEED_AUTOMOUNT 0x00020000 /* handle automount on this dir */
198#define DCACHE_MANAGE_TRANSIT 0x00040000 /* manage transit from this dirent */
199#define DCACHE_MANAGED_DENTRY \
200 (DCACHE_MOUNTED|DCACHE_NEED_AUTOMOUNT|DCACHE_MANAGE_TRANSIT)
201
202#define DCACHE_LRU_LIST 0x00080000
203
204#define DCACHE_ENTRY_TYPE 0x00700000
205#define DCACHE_MISS_TYPE 0x00000000 /* Negative dentry (maybe fallthru to nowhere) */
206#define DCACHE_WHITEOUT_TYPE 0x00100000 /* Whiteout dentry (stop pathwalk) */
207#define DCACHE_DIRECTORY_TYPE 0x00200000 /* Normal directory */
208#define DCACHE_AUTODIR_TYPE 0x00300000 /* Lookupless directory (presumed automount) */
209#define DCACHE_REGULAR_TYPE 0x00400000 /* Regular file type (or fallthru to such) */
210#define DCACHE_SPECIAL_TYPE 0x00500000 /* Other file type (or fallthru to such) */
211#define DCACHE_SYMLINK_TYPE 0x00600000 /* Symlink (or fallthru to such) */
212
213#define DCACHE_MAY_FREE 0x00800000
214#define DCACHE_FALLTHRU 0x01000000 /* Fall through to lower layer */
215#define DCACHE_ENCRYPTED_WITH_KEY 0x02000000 /* dir is encrypted with a valid key */
216#define DCACHE_OP_REAL 0x04000000
217
218#define DCACHE_PAR_LOOKUP 0x10000000 /* being looked up (with parent locked shared) */
219#define DCACHE_DENTRY_CURSOR 0x20000000
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_pseudo(struct super_block *, const struct qstr *);
239extern struct dentry * d_alloc_parallel(struct dentry *, const struct qstr *,
240 wait_queue_head_t *);
241extern struct dentry * d_splice_alias(struct inode *, struct dentry *);
242extern struct dentry * d_add_ci(struct dentry *, struct inode *, struct qstr *);
243extern struct dentry * d_exact_alias(struct dentry *, struct inode *);
244extern struct dentry *d_find_any_alias(struct inode *inode);
245extern struct dentry * d_obtain_alias(struct inode *);
246extern struct dentry * d_obtain_root(struct inode *);
247extern void shrink_dcache_sb(struct super_block *);
248extern void shrink_dcache_parent(struct dentry *);
249extern void shrink_dcache_for_umount(struct super_block *);
250extern void d_invalidate(struct dentry *);
251
252/* only used at mount-time */
253extern struct dentry * d_make_root(struct inode *);
254
255/* <clickety>-<click> the ramfs-type tree */
256extern void d_genocide(struct dentry *);
257
258extern void d_tmpfile(struct dentry *, struct inode *);
259
260extern struct dentry *d_find_alias(struct inode *);
261extern void d_prune_aliases(struct inode *);
262
263/* test whether we have any submounts in a subdir tree */
264extern int path_has_submounts(const struct path *);
265
266/*
267 * This adds the entry to the hash queues.
268 */
269extern void d_rehash(struct dentry *);
270
271extern void d_add(struct dentry *, struct inode *);
272
273/* used for rename() and baskets */
274extern void d_move(struct dentry *, struct dentry *);
275extern void d_exchange(struct dentry *, struct dentry *);
276extern struct dentry *d_ancestor(struct dentry *, struct dentry *);
277
278/* appendix may either be NULL or be used for transname suffixes */
279extern struct dentry *d_lookup(const struct dentry *, const struct qstr *);
280extern struct dentry *d_hash_and_lookup(struct dentry *, struct qstr *);
281extern struct dentry *__d_lookup(const struct dentry *, const struct qstr *);
282extern struct dentry *__d_lookup_rcu(const struct dentry *parent,
283 const struct qstr *name, unsigned *seq);
284
285static inline unsigned d_count(const struct dentry *dentry)
286{
287 return dentry->d_lockref.count;
288}
289
290/*
291 * helper function for dentry_operations.d_dname() members
292 */
293extern __printf(4, 5)
294char *dynamic_dname(struct dentry *, char *, int, const char *, ...);
295extern char *simple_dname(struct dentry *, char *, int);
296
297extern char *__d_path(const struct path *, const struct path *, char *, int);
298extern char *d_absolute_path(const struct path *, char *, int);
299extern char *d_path(const struct path *, char *, int);
300extern char *dentry_path_raw(struct dentry *, char *, int);
301extern char *dentry_path(struct dentry *, char *, int);
302
303/* Allocation counts.. */
304
305/**
306 * dget, dget_dlock - get a reference to a dentry
307 * @dentry: dentry to get a reference to
308 *
309 * Given a dentry or %NULL pointer increment the reference count
310 * if appropriate and return the dentry. A dentry will not be
311 * destroyed when it has references.
312 */
313static inline struct dentry *dget_dlock(struct dentry *dentry)
314{
315 if (dentry)
316 dentry->d_lockref.count++;
317 return dentry;
318}
319
320static inline struct dentry *dget(struct dentry *dentry)
321{
322 if (dentry)
323 lockref_get(&dentry->d_lockref);
324 return dentry;
325}
326
327extern struct dentry *dget_parent(struct dentry *dentry);
328
329/**
330 * d_unhashed - is dentry hashed
331 * @dentry: entry to check
332 *
333 * Returns true if the dentry passed is not currently hashed.
334 */
335
336static inline int d_unhashed(const struct dentry *dentry)
337{
338 return hlist_bl_unhashed(&dentry->d_hash);
339}
340
341static inline int d_unlinked(const struct dentry *dentry)
342{
343 return d_unhashed(dentry) && !IS_ROOT(dentry);
344}
345
346static inline int cant_mount(const struct dentry *dentry)
347{
348 return (dentry->d_flags & DCACHE_CANT_MOUNT);
349}
350
351static inline void dont_mount(struct dentry *dentry)
352{
353 spin_lock(&dentry->d_lock);
354 dentry->d_flags |= DCACHE_CANT_MOUNT;
355 spin_unlock(&dentry->d_lock);
356}
357
358extern void __d_lookup_done(struct dentry *);
359
360static inline int d_in_lookup(const struct dentry *dentry)
361{
362 return dentry->d_flags & DCACHE_PAR_LOOKUP;
363}
364
365static inline void d_lookup_done(struct dentry *dentry)
366{
367 if (unlikely(d_in_lookup(dentry))) {
368 spin_lock(&dentry->d_lock);
369 __d_lookup_done(dentry);
370 spin_unlock(&dentry->d_lock);
371 }
372}
373
374extern void dput(struct dentry *);
375
376static inline bool d_managed(const struct dentry *dentry)
377{
378 return dentry->d_flags & DCACHE_MANAGED_DENTRY;
379}
380
381static inline bool d_mountpoint(const struct dentry *dentry)
382{
383 return dentry->d_flags & DCACHE_MOUNTED;
384}
385
386/*
387 * Directory cache entry type accessor functions.
388 */
389static inline unsigned __d_entry_type(const struct dentry *dentry)
390{
391 return dentry->d_flags & DCACHE_ENTRY_TYPE;
392}
393
394static inline bool d_is_miss(const struct dentry *dentry)
395{
396 return __d_entry_type(dentry) == DCACHE_MISS_TYPE;
397}
398
399static inline bool d_is_whiteout(const struct dentry *dentry)
400{
401 return __d_entry_type(dentry) == DCACHE_WHITEOUT_TYPE;
402}
403
404static inline bool d_can_lookup(const struct dentry *dentry)
405{
406 return __d_entry_type(dentry) == DCACHE_DIRECTORY_TYPE;
407}
408
409static inline bool d_is_autodir(const struct dentry *dentry)
410{
411 return __d_entry_type(dentry) == DCACHE_AUTODIR_TYPE;
412}
413
414static inline bool d_is_dir(const struct dentry *dentry)
415{
416 return d_can_lookup(dentry) || d_is_autodir(dentry);
417}
418
419static inline bool d_is_symlink(const struct dentry *dentry)
420{
421 return __d_entry_type(dentry) == DCACHE_SYMLINK_TYPE;
422}
423
424static inline bool d_is_reg(const struct dentry *dentry)
425{
426 return __d_entry_type(dentry) == DCACHE_REGULAR_TYPE;
427}
428
429static inline bool d_is_special(const struct dentry *dentry)
430{
431 return __d_entry_type(dentry) == DCACHE_SPECIAL_TYPE;
432}
433
434static inline bool d_is_file(const struct dentry *dentry)
435{
436 return d_is_reg(dentry) || d_is_special(dentry);
437}
438
439static inline bool d_is_negative(const struct dentry *dentry)
440{
441 // TODO: check d_is_whiteout(dentry) also.
442 return d_is_miss(dentry);
443}
444
445static 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 */
465static 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 */
483static inline bool d_really_is_positive(const struct dentry *dentry)
484{
485 return dentry->d_inode != NULL;
486}
487
488static inline int simple_positive(const struct dentry *dentry)
489{
490 return d_really_is_positive(dentry) && !d_unhashed(dentry);
491}
492
493extern void d_set_fallthru(struct dentry *dentry);
494
495static inline bool d_is_fallthru(const struct dentry *dentry)
496{
497 return dentry->d_flags & DCACHE_FALLTHRU;
498}
499
500
501extern int sysctl_vfs_cache_pressure;
502
503static 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 */
515static 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 */
527static 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 */
542static 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 */
559static 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.txt
573 */
574static 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 */
590static 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(d_real((struct dentry *) dentry, NULL));
594}
595
596struct name_snapshot {
597 const unsigned char *name;
598 unsigned char inline_name[DNAME_INLINE_LEN];
599};
600void take_dentry_name_snapshot(struct name_snapshot *, struct dentry *);
601void release_dentry_name_snapshot(struct name_snapshot *);
602
603#endif /* __LINUX_DCACHE_H */
604