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 enum d_real_type {
129 D_REAL_DATA,
130 D_REAL_METADATA,
131 };
132
133 struct dentry_operations {
134 int (*d_revalidate)(struct dentry *, unsigned int);
135 int (*d_weak_revalidate)(struct dentry *, unsigned int);
136 int (*d_hash)(const struct dentry *, struct qstr *);
137 int (*d_compare)(const struct dentry *,
138 unsigned int, const char *, const struct qstr *);
139 int (*d_delete)(const struct dentry *);
140 int (*d_init)(struct dentry *);
141 void (*d_release)(struct dentry *);
142 void (*d_prune)(struct dentry *);
143 void (*d_iput)(struct dentry *, struct inode *);
144 char *(*d_dname)(struct dentry *, char *, int);
145 struct vfsmount *(*d_automount)(struct path *);
146 int (*d_manage)(const struct path *, bool);
147 struct dentry *(*d_real)(struct dentry *, enum d_real_type type);
148 } ____cacheline_aligned;
149
150 /*
151 * Locking rules for dentry_operations callbacks are to be found in
152 * Documentation/filesystems/locking.rst. Keep it updated!
153 *
154 * FUrther descriptions are found in Documentation/filesystems/vfs.rst.
155 * Keep it updated too!
156 */
157
158 /* d_flags entries */
159 #define DCACHE_OP_HASH BIT(0)
160 #define DCACHE_OP_COMPARE BIT(1)
161 #define DCACHE_OP_REVALIDATE BIT(2)
162 #define DCACHE_OP_DELETE BIT(3)
163 #define DCACHE_OP_PRUNE BIT(4)
164
165 #define DCACHE_DISCONNECTED BIT(5)
166 /* This dentry is possibly not currently connected to the dcache tree, in
167 * which case its parent will either be itself, or will have this flag as
168 * well. nfsd will not use a dentry with this bit set, but will first
169 * endeavour to clear the bit either by discovering that it is connected,
170 * or by performing lookup operations. Any filesystem which supports
171 * nfsd_operations MUST have a lookup function which, if it finds a
172 * directory inode with a DCACHE_DISCONNECTED dentry, will d_move that
173 * dentry into place and return that dentry rather than the passed one,
174 * typically using d_splice_alias. */
175
176 #define DCACHE_REFERENCED BIT(6) /* Recently used, don't discard. */
177
178 #define DCACHE_DONTCACHE BIT(7) /* Purge from memory on final dput() */
179
180 #define DCACHE_CANT_MOUNT BIT(8)
181 #define DCACHE_GENOCIDE BIT(9)
182 #define DCACHE_SHRINK_LIST BIT(10)
183
184 #define DCACHE_OP_WEAK_REVALIDATE BIT(11)
185
186 #define DCACHE_NFSFS_RENAMED BIT(12)
187 /* this dentry has been "silly renamed" and has to be deleted on the last
188 * dput() */
189 #define DCACHE_FSNOTIFY_PARENT_WATCHED BIT(14)
190 /* Parent inode is watched by some fsnotify listener */
191
192 #define DCACHE_DENTRY_KILLED BIT(15)
193
194 #define DCACHE_MOUNTED BIT(16) /* is a mountpoint */
195 #define DCACHE_NEED_AUTOMOUNT BIT(17) /* handle automount on this dir */
196 #define DCACHE_MANAGE_TRANSIT BIT(18) /* 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 BIT(19)
201
202 #define DCACHE_ENTRY_TYPE (7 << 20) /* bits 20..22 are for storing type: */
203 #define DCACHE_MISS_TYPE (0 << 20) /* Negative dentry */
204 #define DCACHE_WHITEOUT_TYPE (1 << 20) /* Whiteout dentry (stop pathwalk) */
205 #define DCACHE_DIRECTORY_TYPE (2 << 20) /* Normal directory */
206 #define DCACHE_AUTODIR_TYPE (3 << 20) /* Lookupless directory (presumed automount) */
207 #define DCACHE_REGULAR_TYPE (4 << 20) /* Regular file type */
208 #define DCACHE_SPECIAL_TYPE (5 << 20) /* Other file type */
209 #define DCACHE_SYMLINK_TYPE (6 << 20) /* Symlink */
210
211 #define DCACHE_NOKEY_NAME BIT(25) /* Encrypted name encoded without key */
212 #define DCACHE_OP_REAL BIT(26)
213
214 #define DCACHE_PAR_LOOKUP BIT(28) /* being looked up (with parent locked shared) */
215 #define DCACHE_DENTRY_CURSOR BIT(29)
216 #define DCACHE_NORCU BIT(30) /* No RCU delay for freeing */
217
218 extern seqlock_t rename_lock;
219
220 /*
221 * These are the low-level FS interfaces to the dcache..
222 */
223 extern void d_instantiate(struct dentry *, struct inode *);
224 extern void d_instantiate_new(struct dentry *, struct inode *);
225 extern void __d_drop(struct dentry *dentry);
226 extern void d_drop(struct dentry *dentry);
227 extern void d_delete(struct dentry *);
228 extern void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op);
229
230 /* allocate/de-allocate */
231 extern struct dentry * d_alloc(struct dentry *, const struct qstr *);
232 extern struct dentry * d_alloc_anon(struct super_block *);
233 extern struct dentry * d_alloc_parallel(struct dentry *, const struct qstr *,
234 wait_queue_head_t *);
235 extern struct dentry * d_splice_alias(struct inode *, struct dentry *);
236 extern struct dentry * d_add_ci(struct dentry *, struct inode *, struct qstr *);
237 extern bool d_same_name(const struct dentry *dentry, const struct dentry *parent,
238 const struct qstr *name);
239 extern struct dentry * d_exact_alias(struct dentry *, struct inode *);
240 extern struct dentry *d_find_any_alias(struct inode *inode);
241 extern struct dentry * d_obtain_alias(struct inode *);
242 extern struct dentry * d_obtain_root(struct inode *);
243 extern void shrink_dcache_sb(struct super_block *);
244 extern void shrink_dcache_parent(struct dentry *);
245 extern void d_invalidate(struct dentry *);
246
247 /* only used at mount-time */
248 extern struct dentry * d_make_root(struct inode *);
249
250 extern void d_mark_tmpfile(struct file *, struct inode *);
251 extern void d_tmpfile(struct file *, struct inode *);
252
253 extern struct dentry *d_find_alias(struct inode *);
254 extern void d_prune_aliases(struct inode *);
255
256 extern struct dentry *d_find_alias_rcu(struct inode *);
257
258 /* test whether we have any submounts in a subdir tree */
259 extern int path_has_submounts(const struct path *);
260
261 /*
262 * This adds the entry to the hash queues.
263 */
264 extern void d_rehash(struct dentry *);
265
266 extern void d_add(struct dentry *, struct inode *);
267
268 /* used for rename() and baskets */
269 extern void d_move(struct dentry *, struct dentry *);
270 extern void d_exchange(struct dentry *, struct dentry *);
271 extern struct dentry *d_ancestor(struct dentry *, struct dentry *);
272
273 extern struct dentry *d_lookup(const struct dentry *, const struct qstr *);
274 extern struct dentry *d_hash_and_lookup(struct dentry *, struct qstr *);
275
d_count(const struct dentry * dentry)276 static inline unsigned d_count(const struct dentry *dentry)
277 {
278 return dentry->d_lockref.count;
279 }
280
281 /*
282 * helper function for dentry_operations.d_dname() members
283 */
284 extern __printf(3, 4)
285 char *dynamic_dname(char *, int, const char *, ...);
286
287 extern char *__d_path(const struct path *, const struct path *, char *, int);
288 extern char *d_absolute_path(const struct path *, char *, int);
289 extern char *d_path(const struct path *, char *, int);
290 extern char *dentry_path_raw(const struct dentry *, char *, int);
291 extern char *dentry_path(const struct dentry *, char *, int);
292
293 /* Allocation counts.. */
294
295 /**
296 * dget_dlock - get a reference to a dentry
297 * @dentry: dentry to get a reference to
298 *
299 * Given a live dentry, increment the reference count and return the dentry.
300 * Caller must hold @dentry->d_lock. Making sure that dentry is alive is
301 * caller's resonsibility. There are many conditions sufficient to guarantee
302 * that; e.g. anything with non-negative refcount is alive, so's anything
303 * hashed, anything positive, anyone's parent, etc.
304 */
dget_dlock(struct dentry * dentry)305 static inline struct dentry *dget_dlock(struct dentry *dentry)
306 {
307 dentry->d_lockref.count++;
308 return dentry;
309 }
310
311
312 /**
313 * dget - get a reference to a dentry
314 * @dentry: dentry to get a reference to
315 *
316 * Given a dentry or %NULL pointer increment the reference count
317 * if appropriate and return the dentry. A dentry will not be
318 * destroyed when it has references. Conversely, a dentry with
319 * no references can disappear for any number of reasons, starting
320 * with memory pressure. In other words, that primitive is
321 * used to clone an existing reference; using it on something with
322 * zero refcount is a bug.
323 *
324 * NOTE: it will spin if @dentry->d_lock is held. From the deadlock
325 * avoidance point of view it is equivalent to spin_lock()/increment
326 * refcount/spin_unlock(), so calling it under @dentry->d_lock is
327 * always a bug; so's calling it under ->d_lock on any of its descendents.
328 *
329 */
dget(struct dentry * dentry)330 static inline struct dentry *dget(struct dentry *dentry)
331 {
332 if (dentry)
333 lockref_get(&dentry->d_lockref);
334 return dentry;
335 }
336
337 extern struct dentry *dget_parent(struct dentry *dentry);
338
339 /**
340 * d_unhashed - is dentry hashed
341 * @dentry: entry to check
342 *
343 * Returns true if the dentry passed is not currently hashed.
344 */
d_unhashed(const struct dentry * dentry)345 static inline int d_unhashed(const struct dentry *dentry)
346 {
347 return hlist_bl_unhashed(&dentry->d_hash);
348 }
349
d_unlinked(const struct dentry * dentry)350 static inline int d_unlinked(const struct dentry *dentry)
351 {
352 return d_unhashed(dentry) && !IS_ROOT(dentry);
353 }
354
cant_mount(const struct dentry * dentry)355 static inline int cant_mount(const struct dentry *dentry)
356 {
357 return (dentry->d_flags & DCACHE_CANT_MOUNT);
358 }
359
dont_mount(struct dentry * dentry)360 static inline void dont_mount(struct dentry *dentry)
361 {
362 spin_lock(&dentry->d_lock);
363 dentry->d_flags |= DCACHE_CANT_MOUNT;
364 spin_unlock(&dentry->d_lock);
365 }
366
367 extern void __d_lookup_unhash_wake(struct dentry *dentry);
368
d_in_lookup(const struct dentry * dentry)369 static inline int d_in_lookup(const struct dentry *dentry)
370 {
371 return dentry->d_flags & DCACHE_PAR_LOOKUP;
372 }
373
d_lookup_done(struct dentry * dentry)374 static inline void d_lookup_done(struct dentry *dentry)
375 {
376 if (unlikely(d_in_lookup(dentry)))
377 __d_lookup_unhash_wake(dentry);
378 }
379
380 extern void dput(struct dentry *);
381
d_managed(const struct dentry * dentry)382 static inline bool d_managed(const struct dentry *dentry)
383 {
384 return dentry->d_flags & DCACHE_MANAGED_DENTRY;
385 }
386
d_mountpoint(const struct dentry * dentry)387 static inline bool d_mountpoint(const struct dentry *dentry)
388 {
389 return dentry->d_flags & DCACHE_MOUNTED;
390 }
391
392 /*
393 * Directory cache entry type accessor functions.
394 */
__d_entry_type(const struct dentry * dentry)395 static inline unsigned __d_entry_type(const struct dentry *dentry)
396 {
397 return dentry->d_flags & DCACHE_ENTRY_TYPE;
398 }
399
d_is_miss(const struct dentry * dentry)400 static inline bool d_is_miss(const struct dentry *dentry)
401 {
402 return __d_entry_type(dentry) == DCACHE_MISS_TYPE;
403 }
404
d_is_whiteout(const struct dentry * dentry)405 static inline bool d_is_whiteout(const struct dentry *dentry)
406 {
407 return __d_entry_type(dentry) == DCACHE_WHITEOUT_TYPE;
408 }
409
d_can_lookup(const struct dentry * dentry)410 static inline bool d_can_lookup(const struct dentry *dentry)
411 {
412 return __d_entry_type(dentry) == DCACHE_DIRECTORY_TYPE;
413 }
414
d_is_autodir(const struct dentry * dentry)415 static inline bool d_is_autodir(const struct dentry *dentry)
416 {
417 return __d_entry_type(dentry) == DCACHE_AUTODIR_TYPE;
418 }
419
d_is_dir(const struct dentry * dentry)420 static inline bool d_is_dir(const struct dentry *dentry)
421 {
422 return d_can_lookup(dentry) || d_is_autodir(dentry);
423 }
424
d_is_symlink(const struct dentry * dentry)425 static inline bool d_is_symlink(const struct dentry *dentry)
426 {
427 return __d_entry_type(dentry) == DCACHE_SYMLINK_TYPE;
428 }
429
d_is_reg(const struct dentry * dentry)430 static inline bool d_is_reg(const struct dentry *dentry)
431 {
432 return __d_entry_type(dentry) == DCACHE_REGULAR_TYPE;
433 }
434
d_is_special(const struct dentry * dentry)435 static inline bool d_is_special(const struct dentry *dentry)
436 {
437 return __d_entry_type(dentry) == DCACHE_SPECIAL_TYPE;
438 }
439
d_is_file(const struct dentry * dentry)440 static inline bool d_is_file(const struct dentry *dentry)
441 {
442 return d_is_reg(dentry) || d_is_special(dentry);
443 }
444
d_is_negative(const struct dentry * dentry)445 static inline bool d_is_negative(const struct dentry *dentry)
446 {
447 // TODO: check d_is_whiteout(dentry) also.
448 return d_is_miss(dentry);
449 }
450
d_flags_negative(unsigned flags)451 static inline bool d_flags_negative(unsigned flags)
452 {
453 return (flags & DCACHE_ENTRY_TYPE) == DCACHE_MISS_TYPE;
454 }
455
d_is_positive(const struct dentry * dentry)456 static inline bool d_is_positive(const struct dentry *dentry)
457 {
458 return !d_is_negative(dentry);
459 }
460
461 /**
462 * d_really_is_negative - Determine if a dentry is really negative (ignoring fallthroughs)
463 * @dentry: The dentry in question
464 *
465 * Returns true if the dentry represents either an absent name or a name that
466 * doesn't map to an inode (ie. ->d_inode is NULL). The dentry could represent
467 * a true miss, a whiteout that isn't represented by a 0,0 chardev or a
468 * fallthrough marker in an opaque directory.
469 *
470 * Note! (1) This should be used *only* by a filesystem to examine its own
471 * dentries. It should not be used to look at some other filesystem's
472 * dentries. (2) It should also be used in combination with d_inode() to get
473 * the inode. (3) The dentry may have something attached to ->d_lower and the
474 * type field of the flags may be set to something other than miss or whiteout.
475 */
d_really_is_negative(const struct dentry * dentry)476 static inline bool d_really_is_negative(const struct dentry *dentry)
477 {
478 return dentry->d_inode == NULL;
479 }
480
481 /**
482 * d_really_is_positive - Determine if a dentry is really positive (ignoring fallthroughs)
483 * @dentry: The dentry in question
484 *
485 * Returns true if the dentry represents a name that maps to an inode
486 * (ie. ->d_inode is not NULL). The dentry might still represent a whiteout if
487 * that is represented on medium as a 0,0 chardev.
488 *
489 * Note! (1) This should be used *only* by a filesystem to examine its own
490 * dentries. It should not be used to look at some other filesystem's
491 * dentries. (2) It should also be used in combination with d_inode() to get
492 * the inode.
493 */
d_really_is_positive(const struct dentry * dentry)494 static inline bool d_really_is_positive(const struct dentry *dentry)
495 {
496 return dentry->d_inode != NULL;
497 }
498
simple_positive(const struct dentry * dentry)499 static inline int simple_positive(const struct dentry *dentry)
500 {
501 return d_really_is_positive(dentry) && !d_unhashed(dentry);
502 }
503
504 extern int sysctl_vfs_cache_pressure;
505
vfs_pressure_ratio(unsigned long val)506 static inline unsigned long vfs_pressure_ratio(unsigned long val)
507 {
508 return mult_frac(val, sysctl_vfs_cache_pressure, 100);
509 }
510
511 /**
512 * d_inode - Get the actual inode of this dentry
513 * @dentry: The dentry to query
514 *
515 * This is the helper normal filesystems should use to get at their own inodes
516 * in their own dentries and ignore the layering superimposed upon them.
517 */
d_inode(const struct dentry * dentry)518 static inline struct inode *d_inode(const struct dentry *dentry)
519 {
520 return dentry->d_inode;
521 }
522
523 /**
524 * d_inode_rcu - Get the actual inode of this dentry with READ_ONCE()
525 * @dentry: The dentry to query
526 *
527 * This is the helper normal filesystems should use to get at their own inodes
528 * in their own dentries and ignore the layering superimposed upon them.
529 */
d_inode_rcu(const struct dentry * dentry)530 static inline struct inode *d_inode_rcu(const struct dentry *dentry)
531 {
532 return READ_ONCE(dentry->d_inode);
533 }
534
535 /**
536 * d_backing_inode - Get upper or lower inode we should be using
537 * @upper: The upper layer
538 *
539 * This is the helper that should be used to get at the inode that will be used
540 * if this dentry were to be opened as a file. The inode may be on the upper
541 * dentry or it may be on a lower dentry pinned by the upper.
542 *
543 * Normal filesystems should not use this to access their own inodes.
544 */
d_backing_inode(const struct dentry * upper)545 static inline struct inode *d_backing_inode(const struct dentry *upper)
546 {
547 struct inode *inode = upper->d_inode;
548
549 return inode;
550 }
551
552 /**
553 * d_real - Return the real dentry
554 * @dentry: the dentry to query
555 * @type: the type of real dentry (data or metadata)
556 *
557 * If dentry is on a union/overlay, then return the underlying, real dentry.
558 * Otherwise return the dentry itself.
559 *
560 * See also: Documentation/filesystems/vfs.rst
561 */
d_real(struct dentry * dentry,enum d_real_type type)562 static inline struct dentry *d_real(struct dentry *dentry, enum d_real_type type)
563 {
564 if (unlikely(dentry->d_flags & DCACHE_OP_REAL))
565 return dentry->d_op->d_real(dentry, type);
566 else
567 return dentry;
568 }
569
570 /**
571 * d_real_inode - Return the real inode hosting the data
572 * @dentry: The dentry to query
573 *
574 * If dentry is on a union/overlay, then return the underlying, real inode.
575 * Otherwise return d_inode().
576 */
d_real_inode(const struct dentry * dentry)577 static inline struct inode *d_real_inode(const struct dentry *dentry)
578 {
579 /* This usage of d_real() results in const dentry */
580 return d_inode(d_real((struct dentry *) dentry, D_REAL_DATA));
581 }
582
583 struct name_snapshot {
584 struct qstr name;
585 unsigned char inline_name[DNAME_INLINE_LEN];
586 };
587 void take_dentry_name_snapshot(struct name_snapshot *, struct dentry *);
588 void release_dentry_name_snapshot(struct name_snapshot *);
589
d_first_child(const struct dentry * dentry)590 static inline struct dentry *d_first_child(const struct dentry *dentry)
591 {
592 return hlist_entry_safe(dentry->d_children.first, struct dentry, d_sib);
593 }
594
d_next_sibling(const struct dentry * dentry)595 static inline struct dentry *d_next_sibling(const struct dentry *dentry)
596 {
597 return hlist_entry_safe(dentry->d_sib.next, struct dentry, d_sib);
598 }
599
600 #endif /* __LINUX_DCACHE_H */
601