1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef __LINUX_DCACHE_H
3 #define __LINUX_DCACHE_H
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>
22 * linux/include/linux/dcache.h
24 * Dirent cache data structures
26 * (C) Copyright 1997 Thomas Schoebel-Theuer,
27 * with heavy changes by Linus Torvalds
30 #define IS_ROOT(x) ((x) == (x)->d_parent)
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))
37 #define HASH_LEN_DECLARE u32 len; u32 hash
38 #define bytemask_from_count(cnt) (~(~0ul >> (cnt)*8))
42 * "quick string" -- eases parameter passing, but more importantly
43 * saves "metadata" about the string (ie length and the hash).
45 * hash comes first so it snuggles against d_parent in the
55 const unsigned char *name;
58 #define QSTR_INIT(n,l) { { { .len = l } }, .name = n }
60 extern const struct qstr empty_name;
61 extern const struct qstr slash_name;
62 extern const struct qstr dotdot_name;
65 * Try to keep struct dentry aligned on 64 byte cachelines (this will
66 * give reasonable cacheline footprint with larger lines without the
67 * large memory footprint increase).
70 # define DNAME_INLINE_LEN 32 /* 192 bytes */
73 # define DNAME_INLINE_LEN 36 /* 128 bytes */
75 # define DNAME_INLINE_LEN 40 /* 128 bytes */
79 #define d_lock d_lockref.lock
82 /* RCU lookup touched fields */
83 unsigned int d_flags; /* protected by d_lock */
84 seqcount_spinlock_t d_seq; /* per dentry seqlock */
85 struct hlist_bl_node d_hash; /* lookup hash list */
86 struct dentry *d_parent; /* parent directory */
88 struct inode *d_inode; /* Where the name belongs to - NULL is
90 unsigned char d_iname[DNAME_INLINE_LEN]; /* small names */
92 /* Ref lookup also touches following */
93 struct lockref d_lockref; /* per-dentry lock and refcount */
94 const struct dentry_operations *d_op;
95 struct super_block *d_sb; /* The root of the dentry tree */
96 unsigned long d_time; /* used by d_revalidate */
97 void *d_fsdata; /* fs-specific data */
100 struct list_head d_lru; /* LRU list */
101 wait_queue_head_t *d_wait; /* in-lookup ones only */
103 struct list_head d_child; /* child of parent list */
104 struct list_head d_subdirs; /* our children */
106 * d_alias and d_rcu can share memory
109 struct hlist_node d_alias; /* inode alias list */
110 struct hlist_bl_node d_in_lookup_hash; /* only for in-lookup ones */
111 struct rcu_head d_rcu;
113 } __randomize_layout;
116 * dentry->d_lock spinlock nesting subclasses:
121 enum dentry_d_lock_class
123 DENTRY_D_LOCK_NORMAL, /* implicitly used by plain spin_lock() APIs. */
127 struct dentry_operations {
128 int (*d_revalidate)(struct dentry *, unsigned int);
129 int (*d_weak_revalidate)(struct dentry *, unsigned int);
130 int (*d_hash)(const struct dentry *, struct qstr *);
131 int (*d_compare)(const struct dentry *,
132 unsigned int, const char *, const struct qstr *);
133 int (*d_delete)(const struct dentry *);
134 int (*d_init)(struct dentry *);
135 void (*d_release)(struct dentry *);
136 void (*d_prune)(struct dentry *);
137 void (*d_iput)(struct dentry *, struct inode *);
138 char *(*d_dname)(struct dentry *, char *, int);
139 struct vfsmount *(*d_automount)(struct path *);
140 int (*d_manage)(const struct path *, bool);
141 struct dentry *(*d_real)(struct dentry *, const struct inode *);
142 } ____cacheline_aligned;
145 * Locking rules for dentry_operations callbacks are to be found in
146 * Documentation/filesystems/locking.rst. Keep it updated!
148 * FUrther descriptions are found in Documentation/filesystems/vfs.rst.
149 * Keep it updated too!
152 /* d_flags entries */
153 #define DCACHE_OP_HASH 0x00000001
154 #define DCACHE_OP_COMPARE 0x00000002
155 #define DCACHE_OP_REVALIDATE 0x00000004
156 #define DCACHE_OP_DELETE 0x00000008
157 #define DCACHE_OP_PRUNE 0x00000010
159 #define DCACHE_DISCONNECTED 0x00000020
160 /* This dentry is possibly not currently connected to the dcache tree, in
161 * which case its parent will either be itself, or will have this flag as
162 * well. nfsd will not use a dentry with this bit set, but will first
163 * endeavour to clear the bit either by discovering that it is connected,
164 * or by performing lookup operations. Any filesystem which supports
165 * nfsd_operations MUST have a lookup function which, if it finds a
166 * directory inode with a DCACHE_DISCONNECTED dentry, will d_move that
167 * dentry into place and return that dentry rather than the passed one,
168 * typically using d_splice_alias. */
170 #define DCACHE_REFERENCED 0x00000040 /* Recently used, don't discard. */
172 #define DCACHE_DONTCACHE 0x00000080 /* Purge from memory on final dput() */
174 #define DCACHE_CANT_MOUNT 0x00000100
175 #define DCACHE_GENOCIDE 0x00000200
176 #define DCACHE_SHRINK_LIST 0x00000400
178 #define DCACHE_OP_WEAK_REVALIDATE 0x00000800
180 #define DCACHE_NFSFS_RENAMED 0x00001000
181 /* this dentry has been "silly renamed" and has to be deleted on the last
183 #define DCACHE_COOKIE 0x00002000 /* For use by dcookie subsystem */
184 #define DCACHE_FSNOTIFY_PARENT_WATCHED 0x00004000
185 /* Parent inode is watched by some fsnotify listener */
187 #define DCACHE_DENTRY_KILLED 0x00008000
189 #define DCACHE_MOUNTED 0x00010000 /* is a mountpoint */
190 #define DCACHE_NEED_AUTOMOUNT 0x00020000 /* handle automount on this dir */
191 #define DCACHE_MANAGE_TRANSIT 0x00040000 /* manage transit from this dirent */
192 #define DCACHE_MANAGED_DENTRY \
193 (DCACHE_MOUNTED|DCACHE_NEED_AUTOMOUNT|DCACHE_MANAGE_TRANSIT)
195 #define DCACHE_LRU_LIST 0x00080000
197 #define DCACHE_ENTRY_TYPE 0x00700000
198 #define DCACHE_MISS_TYPE 0x00000000 /* Negative dentry (maybe fallthru to nowhere) */
199 #define DCACHE_WHITEOUT_TYPE 0x00100000 /* Whiteout dentry (stop pathwalk) */
200 #define DCACHE_DIRECTORY_TYPE 0x00200000 /* Normal directory */
201 #define DCACHE_AUTODIR_TYPE 0x00300000 /* Lookupless directory (presumed automount) */
202 #define DCACHE_REGULAR_TYPE 0x00400000 /* Regular file type (or fallthru to such) */
203 #define DCACHE_SPECIAL_TYPE 0x00500000 /* Other file type (or fallthru to such) */
204 #define DCACHE_SYMLINK_TYPE 0x00600000 /* Symlink (or fallthru to such) */
206 #define DCACHE_MAY_FREE 0x00800000
207 #define DCACHE_FALLTHRU 0x01000000 /* Fall through to lower layer */
208 #define DCACHE_NOKEY_NAME 0x02000000 /* Encrypted name encoded without key */
209 #define DCACHE_OP_REAL 0x04000000
211 #define DCACHE_PAR_LOOKUP 0x10000000 /* being looked up (with parent locked shared) */
212 #define DCACHE_DENTRY_CURSOR 0x20000000
213 #define DCACHE_NORCU 0x40000000 /* No RCU delay for freeing */
215 extern seqlock_t rename_lock;
218 * These are the low-level FS interfaces to the dcache..
220 extern void d_instantiate(struct dentry *, struct inode *);
221 extern void d_instantiate_new(struct dentry *, struct inode *);
222 extern struct dentry * d_instantiate_unique(struct dentry *, struct inode *);
223 extern struct dentry * d_instantiate_anon(struct dentry *, struct inode *);
224 extern void __d_drop(struct dentry *dentry);
225 extern void d_drop(struct dentry *dentry);
226 extern void d_delete(struct dentry *);
227 extern void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op);
229 /* allocate/de-allocate */
230 extern struct dentry * d_alloc(struct dentry *, const struct qstr *);
231 extern struct dentry * d_alloc_anon(struct super_block *);
232 extern struct dentry * d_alloc_parallel(struct dentry *, const struct qstr *,
233 wait_queue_head_t *);
234 extern struct dentry * d_splice_alias(struct inode *, struct dentry *);
235 extern struct dentry * d_add_ci(struct dentry *, struct inode *, struct qstr *);
236 extern struct dentry * d_exact_alias(struct dentry *, struct inode *);
237 extern struct dentry *d_find_any_alias(struct inode *inode);
238 extern struct dentry * d_obtain_alias(struct inode *);
239 extern struct dentry * d_obtain_root(struct inode *);
240 extern void shrink_dcache_sb(struct super_block *);
241 extern void shrink_dcache_parent(struct dentry *);
242 extern void shrink_dcache_for_umount(struct super_block *);
243 extern void d_invalidate(struct dentry *);
245 /* only used at mount-time */
246 extern struct dentry * d_make_root(struct inode *);
248 /* <clickety>-<click> the ramfs-type tree */
249 extern void d_genocide(struct dentry *);
251 extern void d_tmpfile(struct dentry *, struct inode *);
253 extern struct dentry *d_find_alias(struct inode *);
254 extern void d_prune_aliases(struct inode *);
256 extern struct dentry *d_find_alias_rcu(struct inode *);
258 /* test whether we have any submounts in a subdir tree */
259 extern int path_has_submounts(const struct path *);
262 * This adds the entry to the hash queues.
264 extern void d_rehash(struct dentry *);
266 extern void d_add(struct dentry *, struct inode *);
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 *);
273 /* appendix may either be NULL or be used for transname suffixes */
274 extern struct dentry *d_lookup(const struct dentry *, const struct qstr *);
275 extern struct dentry *d_hash_and_lookup(struct dentry *, struct qstr *);
276 extern struct dentry *__d_lookup(const struct dentry *, const struct qstr *);
277 extern struct dentry *__d_lookup_rcu(const struct dentry *parent,
278 const struct qstr *name, unsigned *seq);
280 static inline unsigned d_count(const struct dentry *dentry)
282 return dentry->d_lockref.count;
286 * helper function for dentry_operations.d_dname() members
288 extern __printf(4, 5)
289 char *dynamic_dname(struct dentry *, char *, int, const char *, ...);
291 extern char *__d_path(const struct path *, const struct path *, char *, int);
292 extern char *d_absolute_path(const struct path *, char *, int);
293 extern char *d_path(const struct path *, char *, int);
294 extern char *dentry_path_raw(const struct dentry *, char *, int);
295 extern char *dentry_path(const struct dentry *, char *, int);
297 /* Allocation counts.. */
300 * dget, dget_dlock - get a reference to a dentry
301 * @dentry: dentry to get a reference to
303 * Given a dentry or %NULL pointer increment the reference count
304 * if appropriate and return the dentry. A dentry will not be
305 * destroyed when it has references.
307 static inline struct dentry *dget_dlock(struct dentry *dentry)
310 dentry->d_lockref.count++;
314 static inline struct dentry *dget(struct dentry *dentry)
317 lockref_get(&dentry->d_lockref);
321 extern struct dentry *dget_parent(struct dentry *dentry);
324 * d_unhashed - is dentry hashed
325 * @dentry: entry to check
327 * Returns true if the dentry passed is not currently hashed.
330 static inline int d_unhashed(const struct dentry *dentry)
332 return hlist_bl_unhashed(&dentry->d_hash);
335 static inline int d_unlinked(const struct dentry *dentry)
337 return d_unhashed(dentry) && !IS_ROOT(dentry);
340 static inline int cant_mount(const struct dentry *dentry)
342 return (dentry->d_flags & DCACHE_CANT_MOUNT);
345 static inline void dont_mount(struct dentry *dentry)
347 spin_lock(&dentry->d_lock);
348 dentry->d_flags |= DCACHE_CANT_MOUNT;
349 spin_unlock(&dentry->d_lock);
352 extern void __d_lookup_done(struct dentry *);
354 static inline int d_in_lookup(const struct dentry *dentry)
356 return dentry->d_flags & DCACHE_PAR_LOOKUP;
359 static inline void d_lookup_done(struct dentry *dentry)
361 if (unlikely(d_in_lookup(dentry))) {
362 spin_lock(&dentry->d_lock);
363 __d_lookup_done(dentry);
364 spin_unlock(&dentry->d_lock);
368 extern void dput(struct dentry *);
370 static inline bool d_managed(const struct dentry *dentry)
372 return dentry->d_flags & DCACHE_MANAGED_DENTRY;
375 static inline bool d_mountpoint(const struct dentry *dentry)
377 return dentry->d_flags & DCACHE_MOUNTED;
381 * Directory cache entry type accessor functions.
383 static inline unsigned __d_entry_type(const struct dentry *dentry)
385 return dentry->d_flags & DCACHE_ENTRY_TYPE;
388 static inline bool d_is_miss(const struct dentry *dentry)
390 return __d_entry_type(dentry) == DCACHE_MISS_TYPE;
393 static inline bool d_is_whiteout(const struct dentry *dentry)
395 return __d_entry_type(dentry) == DCACHE_WHITEOUT_TYPE;
398 static inline bool d_can_lookup(const struct dentry *dentry)
400 return __d_entry_type(dentry) == DCACHE_DIRECTORY_TYPE;
403 static inline bool d_is_autodir(const struct dentry *dentry)
405 return __d_entry_type(dentry) == DCACHE_AUTODIR_TYPE;
408 static inline bool d_is_dir(const struct dentry *dentry)
410 return d_can_lookup(dentry) || d_is_autodir(dentry);
413 static inline bool d_is_symlink(const struct dentry *dentry)
415 return __d_entry_type(dentry) == DCACHE_SYMLINK_TYPE;
418 static inline bool d_is_reg(const struct dentry *dentry)
420 return __d_entry_type(dentry) == DCACHE_REGULAR_TYPE;
423 static inline bool d_is_special(const struct dentry *dentry)
425 return __d_entry_type(dentry) == DCACHE_SPECIAL_TYPE;
428 static inline bool d_is_file(const struct dentry *dentry)
430 return d_is_reg(dentry) || d_is_special(dentry);
433 static inline bool d_is_negative(const struct dentry *dentry)
435 // TODO: check d_is_whiteout(dentry) also.
436 return d_is_miss(dentry);
439 static inline bool d_flags_negative(unsigned flags)
441 return (flags & DCACHE_ENTRY_TYPE) == DCACHE_MISS_TYPE;
444 static inline bool d_is_positive(const struct dentry *dentry)
446 return !d_is_negative(dentry);
450 * d_really_is_negative - Determine if a dentry is really negative (ignoring fallthroughs)
451 * @dentry: The dentry in question
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.
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.
464 static inline bool d_really_is_negative(const struct dentry *dentry)
466 return dentry->d_inode == NULL;
470 * d_really_is_positive - Determine if a dentry is really positive (ignoring fallthroughs)
471 * @dentry: The dentry in question
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.
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
482 static inline bool d_really_is_positive(const struct dentry *dentry)
484 return dentry->d_inode != NULL;
487 static inline int simple_positive(const struct dentry *dentry)
489 return d_really_is_positive(dentry) && !d_unhashed(dentry);
492 extern void d_set_fallthru(struct dentry *dentry);
494 static inline bool d_is_fallthru(const struct dentry *dentry)
496 return dentry->d_flags & DCACHE_FALLTHRU;
500 extern int sysctl_vfs_cache_pressure;
502 static inline unsigned long vfs_pressure_ratio(unsigned long val)
504 return mult_frac(val, sysctl_vfs_cache_pressure, 100);
508 * d_inode - Get the actual inode of this dentry
509 * @dentry: The dentry to query
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.
514 static inline struct inode *d_inode(const struct dentry *dentry)
516 return dentry->d_inode;
520 * d_inode_rcu - Get the actual inode of this dentry with READ_ONCE()
521 * @dentry: The dentry to query
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.
526 static inline struct inode *d_inode_rcu(const struct dentry *dentry)
528 return READ_ONCE(dentry->d_inode);
532 * d_backing_inode - Get upper or lower inode we should be using
533 * @upper: The upper layer
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.
539 * Normal filesystems should not use this to access their own inodes.
541 static inline struct inode *d_backing_inode(const struct dentry *upper)
543 struct inode *inode = upper->d_inode;
549 * d_backing_dentry - Get upper or lower dentry we should be using
550 * @upper: The upper layer
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.
556 * Normal filesystems should not use this to access their own dentries.
558 static inline struct dentry *d_backing_dentry(struct dentry *upper)
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)
568 * If dentry is on a union/overlay, then return the underlying, real dentry.
569 * Otherwise return the dentry itself.
571 * See also: Documentation/filesystems/vfs.rst
573 static inline struct dentry *d_real(struct dentry *dentry,
574 const struct inode *inode)
576 if (unlikely(dentry->d_flags & DCACHE_OP_REAL))
577 return dentry->d_op->d_real(dentry, inode);
583 * d_real_inode - Return the real inode
584 * @dentry: The dentry to query
586 * If dentry is on a union/overlay, then return the underlying, real inode.
587 * Otherwise return d_inode().
589 static inline struct inode *d_real_inode(const struct dentry *dentry)
591 /* This usage of d_real() results in const dentry */
592 return d_backing_inode(d_real((struct dentry *) dentry, NULL));
595 struct name_snapshot {
597 unsigned char inline_name[DNAME_INLINE_LEN];
599 void take_dentry_name_snapshot(struct name_snapshot *, struct dentry *);
600 void release_dentry_name_snapshot(struct name_snapshot *);
602 #endif /* __LINUX_DCACHE_H */