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