1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef __LINUX_DCACHE_H
3 #define __LINUX_DCACHE_H
4
5 #include <linux/atomic.h>
6 #include <linux/list.h>
7 #include <linux/math.h>
8 #include <linux/rculist.h>
9 #include <linux/rculist_bl.h>
10 #include <linux/spinlock.h>
11 #include <linux/seqlock.h>
12 #include <linux/cache.h>
13 #include <linux/rcupdate.h>
14 #include <linux/lockref.h>
15 #include <linux/stringhash.h>
16 #include <linux/wait.h>
17
18 struct path;
19 struct file;
20 struct vfsmount;
21
22 /*
23 * linux/include/linux/dcache.h
24 *
25 * Dirent cache data structures
26 *
27 * (C) Copyright 1997 Thomas Schoebel-Theuer,
28 * with heavy changes by Linus Torvalds
29 */
30
31 #define IS_ROOT(x) ((x) == (x)->d_parent)
32
33 /* The hash is always the low bits of hash_len */
34 #ifdef __LITTLE_ENDIAN
35 #define HASH_LEN_DECLARE u32 hash; u32 len
36 #define bytemask_from_count(cnt) (~(~0ul << (cnt)*8))
37 #else
38 #define HASH_LEN_DECLARE u32 len; u32 hash
39 #define bytemask_from_count(cnt) (~(~0ul >> (cnt)*8))
40 #endif
41
42 /*
43 * "quick string" -- eases parameter passing, but more importantly
44 * saves "metadata" about the string (ie length and the hash).
45 *
46 * hash comes first so it snuggles against d_parent in the
47 * dentry.
48 */
49 struct qstr {
50 union {
51 struct {
52 HASH_LEN_DECLARE;
53 };
54 u64 hash_len;
55 };
56 const unsigned char *name;
57 };
58
59 #define QSTR_INIT(n,l) { { { .len = l } }, .name = n }
60
61 extern const struct qstr empty_name;
62 extern const struct qstr slash_name;
63 extern const struct qstr dotdot_name;
64
65 /*
66 * Try to keep struct dentry aligned on 64 byte cachelines (this will
67 * give reasonable cacheline footprint with larger lines without the
68 * large memory footprint increase).
69 */
70 #ifdef CONFIG_64BIT
71 # define DNAME_INLINE_LEN 40 /* 192 bytes */
72 #else
73 # ifdef CONFIG_SMP
74 # define DNAME_INLINE_LEN 40 /* 128 bytes */
75 # else
76 # define DNAME_INLINE_LEN 44 /* 128 bytes */
77 # endif
78 #endif
79
80 #define d_lock d_lockref.lock
81
82 struct dentry {
83 /* RCU lookup touched fields */
84 unsigned int d_flags; /* protected by d_lock */
85 seqcount_spinlock_t d_seq; /* per dentry seqlock */
86 struct hlist_bl_node d_hash; /* lookup hash list */
87 struct dentry *d_parent; /* parent directory */
88 struct qstr d_name;
89 struct inode *d_inode; /* Where the name belongs to - NULL is
90 * negative */
91 unsigned char d_iname[DNAME_INLINE_LEN]; /* small names */
92
93 /* Ref lookup also touches following */
94 struct lockref d_lockref; /* per-dentry lock and refcount */
95 const struct dentry_operations *d_op;
96 struct super_block *d_sb; /* The root of the dentry tree */
97 unsigned long d_time; /* used by d_revalidate */
98 void *d_fsdata; /* fs-specific data */
99
100 union {
101 struct list_head d_lru; /* LRU list */
102 wait_queue_head_t *d_wait; /* in-lookup ones only */
103 };
104 struct hlist_node d_sib; /* child of parent list */
105 struct hlist_head d_children; /* our children */
106 /*
107 * d_alias and d_rcu can share memory
108 */
109 union {
110 struct hlist_node d_alias; /* inode alias list */
111 struct hlist_bl_node d_in_lookup_hash; /* only for in-lookup ones */
112 struct rcu_head d_rcu;
113 } d_u;
114 };
115
116 /*
117 * dentry->d_lock spinlock nesting subclasses:
118 *
119 * 0: normal
120 * 1: nested
121 */
122 enum dentry_d_lock_class
123 {
124 DENTRY_D_LOCK_NORMAL, /* implicitly used by plain spin_lock() APIs. */
125 DENTRY_D_LOCK_NESTED
126 };
127
128 struct dentry_operations {
129 int (*d_revalidate)(struct dentry *, unsigned int);
130 int (*d_weak_revalidate)(struct dentry *, unsigned int);
131 int (*d_hash)(const struct dentry *, struct qstr *);
132 int (*d_compare)(const struct dentry *,
133 unsigned int, const char *, const struct qstr *);
134 int (*d_delete)(const struct dentry *);
135 int (*d_init)(struct dentry *);
136 void (*d_release)(struct dentry *);
137 void (*d_prune)(struct dentry *);
138 void (*d_iput)(struct dentry *, struct inode *);
139 char *(*d_dname)(struct dentry *, char *, int);
140 struct vfsmount *(*d_automount)(struct path *);
141 int (*d_manage)(const struct path *, bool);
142 struct dentry *(*d_real)(struct dentry *, const struct inode *);
143 } ____cacheline_aligned;
144
145 /*
146 * Locking rules for dentry_operations callbacks are to be found in
147 * Documentation/filesystems/locking.rst. Keep it updated!
148 *
149 * FUrther descriptions are found in Documentation/filesystems/vfs.rst.
150 * Keep it updated too!
151 */
152
153 /* d_flags entries */
154 #define DCACHE_OP_HASH BIT(0)
155 #define DCACHE_OP_COMPARE BIT(1)
156 #define DCACHE_OP_REVALIDATE BIT(2)
157 #define DCACHE_OP_DELETE BIT(3)
158 #define DCACHE_OP_PRUNE BIT(4)
159
160 #define DCACHE_DISCONNECTED BIT(5)
161 /* This dentry is possibly not currently connected to the dcache tree, in
162 * which case its parent will either be itself, or will have this flag as
163 * well. nfsd will not use a dentry with this bit set, but will first
164 * endeavour to clear the bit either by discovering that it is connected,
165 * or by performing lookup operations. Any filesystem which supports
166 * nfsd_operations MUST have a lookup function which, if it finds a
167 * directory inode with a DCACHE_DISCONNECTED dentry, will d_move that
168 * dentry into place and return that dentry rather than the passed one,
169 * typically using d_splice_alias. */
170
171 #define DCACHE_REFERENCED BIT(6) /* Recently used, don't discard. */
172
173 #define DCACHE_DONTCACHE BIT(7) /* Purge from memory on final dput() */
174
175 #define DCACHE_CANT_MOUNT BIT(8)
176 #define DCACHE_GENOCIDE BIT(9)
177 #define DCACHE_SHRINK_LIST BIT(10)
178
179 #define DCACHE_OP_WEAK_REVALIDATE BIT(11)
180
181 #define DCACHE_NFSFS_RENAMED BIT(12)
182 /* this dentry has been "silly renamed" and has to be deleted on the last
183 * dput() */
184 #define DCACHE_FSNOTIFY_PARENT_WATCHED BIT(14)
185 /* Parent inode is watched by some fsnotify listener */
186
187 #define DCACHE_DENTRY_KILLED BIT(15)
188
189 #define DCACHE_MOUNTED BIT(16) /* is a mountpoint */
190 #define DCACHE_NEED_AUTOMOUNT BIT(17) /* handle automount on this dir */
191 #define DCACHE_MANAGE_TRANSIT BIT(18) /* manage transit from this dirent */
192 #define DCACHE_MANAGED_DENTRY \
193 (DCACHE_MOUNTED|DCACHE_NEED_AUTOMOUNT|DCACHE_MANAGE_TRANSIT)
194
195 #define DCACHE_LRU_LIST BIT(19)
196
197 #define DCACHE_ENTRY_TYPE (7 << 20) /* bits 20..22 are for storing type: */
198 #define DCACHE_MISS_TYPE (0 << 20) /* Negative dentry */
199 #define DCACHE_WHITEOUT_TYPE (1 << 20) /* Whiteout dentry (stop pathwalk) */
200 #define DCACHE_DIRECTORY_TYPE (2 << 20) /* Normal directory */
201 #define DCACHE_AUTODIR_TYPE (3 << 20) /* Lookupless directory (presumed automount) */
202 #define DCACHE_REGULAR_TYPE (4 << 20) /* Regular file type */
203 #define DCACHE_SPECIAL_TYPE (5 << 20) /* Other file type */
204 #define DCACHE_SYMLINK_TYPE (6 << 20) /* Symlink */
205
206 #define DCACHE_NOKEY_NAME BIT(25) /* Encrypted name encoded without key */
207 #define DCACHE_OP_REAL BIT(26)
208
209 #define DCACHE_PAR_LOOKUP BIT(28) /* being looked up (with parent locked shared) */
210 #define DCACHE_DENTRY_CURSOR BIT(29)
211 #define DCACHE_NORCU BIT(30) /* No RCU delay for freeing */
212
213 extern seqlock_t rename_lock;
214
215 /*
216 * These are the low-level FS interfaces to the dcache..
217 */
218 extern void d_instantiate(struct dentry *, struct inode *);
219 extern void d_instantiate_new(struct dentry *, struct inode *);
220 extern void __d_drop(struct dentry *dentry);
221 extern void d_drop(struct dentry *dentry);
222 extern void d_delete(struct dentry *);
223 extern void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op);
224
225 /* allocate/de-allocate */
226 extern struct dentry * d_alloc(struct dentry *, const struct qstr *);
227 extern struct dentry * d_alloc_anon(struct super_block *);
228 extern struct dentry * d_alloc_parallel(struct dentry *, const struct qstr *,
229 wait_queue_head_t *);
230 extern struct dentry * d_splice_alias(struct inode *, struct dentry *);
231 extern struct dentry * d_add_ci(struct dentry *, struct inode *, struct qstr *);
232 extern bool d_same_name(const struct dentry *dentry, const struct dentry *parent,
233 const struct qstr *name);
234 extern struct dentry * d_exact_alias(struct dentry *, struct inode *);
235 extern struct dentry *d_find_any_alias(struct inode *inode);
236 extern struct dentry * d_obtain_alias(struct inode *);
237 extern struct dentry * d_obtain_root(struct inode *);
238 extern void shrink_dcache_sb(struct super_block *);
239 extern void shrink_dcache_parent(struct dentry *);
240 extern void d_invalidate(struct dentry *);
241
242 /* only used at mount-time */
243 extern struct dentry * d_make_root(struct inode *);
244
245 extern void d_mark_tmpfile(struct file *, struct inode *);
246 extern void d_tmpfile(struct file *, struct inode *);
247
248 extern struct dentry *d_find_alias(struct inode *);
249 extern void d_prune_aliases(struct inode *);
250
251 extern struct dentry *d_find_alias_rcu(struct inode *);
252
253 /* test whether we have any submounts in a subdir tree */
254 extern int path_has_submounts(const struct path *);
255
256 /*
257 * This adds the entry to the hash queues.
258 */
259 extern void d_rehash(struct dentry *);
260
261 extern void d_add(struct dentry *, struct inode *);
262
263 /* used for rename() and baskets */
264 extern void d_move(struct dentry *, struct dentry *);
265 extern void d_exchange(struct dentry *, struct dentry *);
266 extern struct dentry *d_ancestor(struct dentry *, struct dentry *);
267
268 extern struct dentry *d_lookup(const struct dentry *, const struct qstr *);
269 extern struct dentry *d_hash_and_lookup(struct dentry *, struct qstr *);
270
d_count(const struct dentry * dentry)271 static inline unsigned d_count(const struct dentry *dentry)
272 {
273 return dentry->d_lockref.count;
274 }
275
276 /*
277 * helper function for dentry_operations.d_dname() members
278 */
279 extern __printf(3, 4)
280 char *dynamic_dname(char *, int, const char *, ...);
281
282 extern char *__d_path(const struct path *, const struct path *, char *, int);
283 extern char *d_absolute_path(const struct path *, char *, int);
284 extern char *d_path(const struct path *, char *, int);
285 extern char *dentry_path_raw(const struct dentry *, char *, int);
286 extern char *dentry_path(const struct dentry *, char *, int);
287
288 /* Allocation counts.. */
289
290 /**
291 * dget_dlock - get a reference to a dentry
292 * @dentry: dentry to get a reference to
293 *
294 * Given a live dentry, increment the reference count and return the dentry.
295 * Caller must hold @dentry->d_lock. Making sure that dentry is alive is
296 * caller's resonsibility. There are many conditions sufficient to guarantee
297 * that; e.g. anything with non-negative refcount is alive, so's anything
298 * hashed, anything positive, anyone's parent, etc.
299 */
dget_dlock(struct dentry * dentry)300 static inline struct dentry *dget_dlock(struct dentry *dentry)
301 {
302 dentry->d_lockref.count++;
303 return dentry;
304 }
305
306
307 /**
308 * dget - get a reference to a dentry
309 * @dentry: dentry to get a reference to
310 *
311 * Given a dentry or %NULL pointer increment the reference count
312 * if appropriate and return the dentry. A dentry will not be
313 * destroyed when it has references. Conversely, a dentry with
314 * no references can disappear for any number of reasons, starting
315 * with memory pressure. In other words, that primitive is
316 * used to clone an existing reference; using it on something with
317 * zero refcount is a bug.
318 *
319 * NOTE: it will spin if @dentry->d_lock is held. From the deadlock
320 * avoidance point of view it is equivalent to spin_lock()/increment
321 * refcount/spin_unlock(), so calling it under @dentry->d_lock is
322 * always a bug; so's calling it under ->d_lock on any of its descendents.
323 *
324 */
dget(struct dentry * dentry)325 static inline struct dentry *dget(struct dentry *dentry)
326 {
327 if (dentry)
328 lockref_get(&dentry->d_lockref);
329 return dentry;
330 }
331
332 extern struct dentry *dget_parent(struct dentry *dentry);
333
334 /**
335 * d_unhashed - is dentry hashed
336 * @dentry: entry to check
337 *
338 * Returns true if the dentry passed is not currently hashed.
339 */
d_unhashed(const struct dentry * dentry)340 static inline int d_unhashed(const struct dentry *dentry)
341 {
342 return hlist_bl_unhashed(&dentry->d_hash);
343 }
344
d_unlinked(const struct dentry * dentry)345 static inline int d_unlinked(const struct dentry *dentry)
346 {
347 return d_unhashed(dentry) && !IS_ROOT(dentry);
348 }
349
cant_mount(const struct dentry * dentry)350 static inline int cant_mount(const struct dentry *dentry)
351 {
352 return (dentry->d_flags & DCACHE_CANT_MOUNT);
353 }
354
dont_mount(struct dentry * dentry)355 static 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
362 extern void __d_lookup_unhash_wake(struct dentry *dentry);
363
d_in_lookup(const struct dentry * dentry)364 static inline int d_in_lookup(const struct dentry *dentry)
365 {
366 return dentry->d_flags & DCACHE_PAR_LOOKUP;
367 }
368
d_lookup_done(struct dentry * dentry)369 static inline void d_lookup_done(struct dentry *dentry)
370 {
371 if (unlikely(d_in_lookup(dentry)))
372 __d_lookup_unhash_wake(dentry);
373 }
374
375 extern void dput(struct dentry *);
376
d_managed(const struct dentry * dentry)377 static inline bool d_managed(const struct dentry *dentry)
378 {
379 return dentry->d_flags & DCACHE_MANAGED_DENTRY;
380 }
381
d_mountpoint(const struct dentry * dentry)382 static inline bool d_mountpoint(const struct dentry *dentry)
383 {
384 return dentry->d_flags & DCACHE_MOUNTED;
385 }
386
387 /*
388 * Directory cache entry type accessor functions.
389 */
__d_entry_type(const struct dentry * dentry)390 static inline unsigned __d_entry_type(const struct dentry *dentry)
391 {
392 return dentry->d_flags & DCACHE_ENTRY_TYPE;
393 }
394
d_is_miss(const struct dentry * dentry)395 static inline bool d_is_miss(const struct dentry *dentry)
396 {
397 return __d_entry_type(dentry) == DCACHE_MISS_TYPE;
398 }
399
d_is_whiteout(const struct dentry * dentry)400 static inline bool d_is_whiteout(const struct dentry *dentry)
401 {
402 return __d_entry_type(dentry) == DCACHE_WHITEOUT_TYPE;
403 }
404
d_can_lookup(const struct dentry * dentry)405 static inline bool d_can_lookup(const struct dentry *dentry)
406 {
407 return __d_entry_type(dentry) == DCACHE_DIRECTORY_TYPE;
408 }
409
d_is_autodir(const struct dentry * dentry)410 static inline bool d_is_autodir(const struct dentry *dentry)
411 {
412 return __d_entry_type(dentry) == DCACHE_AUTODIR_TYPE;
413 }
414
d_is_dir(const struct dentry * dentry)415 static inline bool d_is_dir(const struct dentry *dentry)
416 {
417 return d_can_lookup(dentry) || d_is_autodir(dentry);
418 }
419
d_is_symlink(const struct dentry * dentry)420 static inline bool d_is_symlink(const struct dentry *dentry)
421 {
422 return __d_entry_type(dentry) == DCACHE_SYMLINK_TYPE;
423 }
424
d_is_reg(const struct dentry * dentry)425 static inline bool d_is_reg(const struct dentry *dentry)
426 {
427 return __d_entry_type(dentry) == DCACHE_REGULAR_TYPE;
428 }
429
d_is_special(const struct dentry * dentry)430 static inline bool d_is_special(const struct dentry *dentry)
431 {
432 return __d_entry_type(dentry) == DCACHE_SPECIAL_TYPE;
433 }
434
d_is_file(const struct dentry * dentry)435 static inline bool d_is_file(const struct dentry *dentry)
436 {
437 return d_is_reg(dentry) || d_is_special(dentry);
438 }
439
d_is_negative(const struct dentry * dentry)440 static inline bool d_is_negative(const struct dentry *dentry)
441 {
442 // TODO: check d_is_whiteout(dentry) also.
443 return d_is_miss(dentry);
444 }
445
d_flags_negative(unsigned flags)446 static inline bool d_flags_negative(unsigned flags)
447 {
448 return (flags & DCACHE_ENTRY_TYPE) == DCACHE_MISS_TYPE;
449 }
450
d_is_positive(const struct dentry * dentry)451 static inline bool d_is_positive(const struct dentry *dentry)
452 {
453 return !d_is_negative(dentry);
454 }
455
456 /**
457 * d_really_is_negative - Determine if a dentry is really negative (ignoring fallthroughs)
458 * @dentry: The dentry in question
459 *
460 * Returns true if the dentry represents either an absent name or a name that
461 * doesn't map to an inode (ie. ->d_inode is NULL). The dentry could represent
462 * a true miss, a whiteout that isn't represented by a 0,0 chardev or a
463 * fallthrough marker in an opaque directory.
464 *
465 * Note! (1) This should be used *only* by a filesystem to examine its own
466 * dentries. It should not be used to look at some other filesystem's
467 * dentries. (2) It should also be used in combination with d_inode() to get
468 * the inode. (3) The dentry may have something attached to ->d_lower and the
469 * type field of the flags may be set to something other than miss or whiteout.
470 */
d_really_is_negative(const struct dentry * dentry)471 static inline bool d_really_is_negative(const struct dentry *dentry)
472 {
473 return dentry->d_inode == NULL;
474 }
475
476 /**
477 * d_really_is_positive - Determine if a dentry is really positive (ignoring fallthroughs)
478 * @dentry: The dentry in question
479 *
480 * Returns true if the dentry represents a name that maps to an inode
481 * (ie. ->d_inode is not NULL). The dentry might still represent a whiteout if
482 * that is represented on medium as a 0,0 chardev.
483 *
484 * Note! (1) This should be used *only* by a filesystem to examine its own
485 * dentries. It should not be used to look at some other filesystem's
486 * dentries. (2) It should also be used in combination with d_inode() to get
487 * the inode.
488 */
d_really_is_positive(const struct dentry * dentry)489 static inline bool d_really_is_positive(const struct dentry *dentry)
490 {
491 return dentry->d_inode != NULL;
492 }
493
simple_positive(const struct dentry * dentry)494 static inline int simple_positive(const struct dentry *dentry)
495 {
496 return d_really_is_positive(dentry) && !d_unhashed(dentry);
497 }
498
499 extern int sysctl_vfs_cache_pressure;
500
vfs_pressure_ratio(unsigned long val)501 static 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 */
d_inode(const struct dentry * dentry)513 static 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 */
d_inode_rcu(const struct dentry * dentry)525 static 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 */
d_backing_inode(const struct dentry * upper)540 static 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_real - Return the real dentry
549 * @dentry: the dentry to query
550 * @inode: inode to select the dentry from multiple layers (can be NULL)
551 *
552 * If dentry is on a union/overlay, then return the underlying, real dentry.
553 * Otherwise return the dentry itself.
554 *
555 * See also: Documentation/filesystems/vfs.rst
556 */
d_real(struct dentry * dentry,const struct inode * inode)557 static inline struct dentry *d_real(struct dentry *dentry,
558 const struct inode *inode)
559 {
560 if (unlikely(dentry->d_flags & DCACHE_OP_REAL))
561 return dentry->d_op->d_real(dentry, inode);
562 else
563 return dentry;
564 }
565
566 /**
567 * d_real_inode - Return the real inode
568 * @dentry: The dentry to query
569 *
570 * If dentry is on a union/overlay, then return the underlying, real inode.
571 * Otherwise return d_inode().
572 */
d_real_inode(const struct dentry * dentry)573 static inline struct inode *d_real_inode(const struct dentry *dentry)
574 {
575 /* This usage of d_real() results in const dentry */
576 return d_backing_inode(d_real((struct dentry *) dentry, NULL));
577 }
578
579 struct name_snapshot {
580 struct qstr name;
581 unsigned char inline_name[DNAME_INLINE_LEN];
582 };
583 void take_dentry_name_snapshot(struct name_snapshot *, struct dentry *);
584 void release_dentry_name_snapshot(struct name_snapshot *);
585
d_first_child(const struct dentry * dentry)586 static inline struct dentry *d_first_child(const struct dentry *dentry)
587 {
588 return hlist_entry_safe(dentry->d_children.first, struct dentry, d_sib);
589 }
590
d_next_sibling(const struct dentry * dentry)591 static inline struct dentry *d_next_sibling(const struct dentry *dentry)
592 {
593 return hlist_entry_safe(dentry->d_sib.next, struct dentry, d_sib);
594 }
595
596 #endif /* __LINUX_DCACHE_H */
597