1 #ifndef __LINUX_DCACHE_H
2 #define __LINUX_DCACHE_H
4 #include <linux/atomic.h>
5 #include <linux/list.h>
6 #include <linux/rculist.h>
7 #include <linux/rculist_bl.h>
8 #include <linux/spinlock.h>
9 #include <linux/seqlock.h>
10 #include <linux/cache.h>
11 #include <linux/rcupdate.h>
12 #include <linux/lockref.h>
13 #include <linux/stringhash.h>
14 #include <linux/wait.h>
20 * linux/include/linux/dcache.h
22 * Dirent cache data structures
24 * (C) Copyright 1997 Thomas Schoebel-Theuer,
25 * with heavy changes by Linus Torvalds
28 #define IS_ROOT(x) ((x) == (x)->d_parent)
30 /* The hash is always the low bits of hash_len */
31 #ifdef __LITTLE_ENDIAN
32 #define HASH_LEN_DECLARE u32 hash; u32 len
33 #define bytemask_from_count(cnt) (~(~0ul << (cnt)*8))
35 #define HASH_LEN_DECLARE u32 len; u32 hash
36 #define bytemask_from_count(cnt) (~(~0ul >> (cnt)*8))
40 * "quick string" -- eases parameter passing, but more importantly
41 * saves "metadata" about the string (ie length and the hash).
43 * hash comes first so it snuggles against d_parent in the
53 const unsigned char *name
;
56 #define QSTR_INIT(n,l) { { { .len = l } }, .name = n }
58 struct dentry_stat_t
{
61 long age_limit
; /* age in seconds */
62 long want_pages
; /* pages requested by system */
65 extern struct dentry_stat_t dentry_stat
;
68 * Try to keep struct dentry aligned on 64 byte cachelines (this will
69 * give reasonable cacheline footprint with larger lines without the
70 * large memory footprint increase).
73 # define DNAME_INLINE_LEN 32 /* 192 bytes */
76 # define DNAME_INLINE_LEN 36 /* 128 bytes */
78 # define DNAME_INLINE_LEN 40 /* 128 bytes */
82 #define d_lock d_lockref.lock
85 /* RCU lookup touched fields */
86 unsigned int d_flags
; /* protected by d_lock */
87 seqcount_t d_seq
; /* per dentry seqlock */
88 struct hlist_bl_node d_hash
; /* lookup hash list */
89 struct dentry
*d_parent
; /* parent directory */
91 struct inode
*d_inode
; /* Where the name belongs to - NULL is
93 unsigned char d_iname
[DNAME_INLINE_LEN
]; /* small names */
95 /* Ref lookup also touches following */
96 struct lockref d_lockref
; /* per-dentry lock and refcount */
97 const struct dentry_operations
*d_op
;
98 struct super_block
*d_sb
; /* The root of the dentry tree */
99 unsigned long d_time
; /* used by d_revalidate */
100 void *d_fsdata
; /* fs-specific data */
103 struct list_head d_lru
; /* LRU list */
104 wait_queue_head_t
*d_wait
; /* in-lookup ones only */
106 struct list_head d_child
; /* child of parent list */
107 struct list_head d_subdirs
; /* our children */
109 * d_alias and d_rcu can share memory
112 struct hlist_node d_alias
; /* inode alias list */
113 struct hlist_bl_node d_in_lookup_hash
; /* only for in-lookup ones */
114 struct rcu_head d_rcu
;
119 * dentry->d_lock spinlock nesting subclasses:
124 enum dentry_d_lock_class
126 DENTRY_D_LOCK_NORMAL
, /* implicitly used by plain spin_lock() APIs. */
130 struct dentry_operations
{
131 int (*d_revalidate
)(struct dentry
*, unsigned int);
132 int (*d_weak_revalidate
)(struct dentry
*, unsigned int);
133 int (*d_hash
)(const struct dentry
*, struct qstr
*);
134 int (*d_compare
)(const struct dentry
*,
135 unsigned int, const char *, const struct qstr
*);
136 int (*d_delete
)(const struct dentry
*);
137 int (*d_init
)(struct dentry
*);
138 void (*d_release
)(struct dentry
*);
139 void (*d_prune
)(struct dentry
*);
140 void (*d_iput
)(struct dentry
*, struct inode
*);
141 char *(*d_dname
)(struct dentry
*, char *, int);
142 struct vfsmount
*(*d_automount
)(struct path
*);
143 int (*d_manage
)(const struct path
*, bool);
144 struct dentry
*(*d_real
)(struct dentry
*, const struct inode
*,
146 } ____cacheline_aligned
;
149 * Locking rules for dentry_operations callbacks are to be found in
150 * Documentation/filesystems/Locking. Keep it updated!
152 * FUrther descriptions are found in Documentation/filesystems/vfs.txt.
153 * Keep it updated too!
156 /* d_flags entries */
157 #define DCACHE_OP_HASH 0x00000001
158 #define DCACHE_OP_COMPARE 0x00000002
159 #define DCACHE_OP_REVALIDATE 0x00000004
160 #define DCACHE_OP_DELETE 0x00000008
161 #define DCACHE_OP_PRUNE 0x00000010
163 #define DCACHE_DISCONNECTED 0x00000020
164 /* This dentry is possibly not currently connected to the dcache tree, in
165 * which case its parent will either be itself, or will have this flag as
166 * well. nfsd will not use a dentry with this bit set, but will first
167 * endeavour to clear the bit either by discovering that it is connected,
168 * or by performing lookup operations. Any filesystem which supports
169 * nfsd_operations MUST have a lookup function which, if it finds a
170 * directory inode with a DCACHE_DISCONNECTED dentry, will d_move that
171 * dentry into place and return that dentry rather than the passed one,
172 * typically using d_splice_alias. */
174 #define DCACHE_REFERENCED 0x00000040 /* Recently used, don't discard. */
175 #define DCACHE_RCUACCESS 0x00000080 /* Entry has ever been RCU-visible */
177 #define DCACHE_CANT_MOUNT 0x00000100
178 #define DCACHE_GENOCIDE 0x00000200
179 #define DCACHE_SHRINK_LIST 0x00000400
181 #define DCACHE_OP_WEAK_REVALIDATE 0x00000800
183 #define DCACHE_NFSFS_RENAMED 0x00001000
184 /* this dentry has been "silly renamed" and has to be deleted on the last
186 #define DCACHE_COOKIE 0x00002000 /* For use by dcookie subsystem */
187 #define DCACHE_FSNOTIFY_PARENT_WATCHED 0x00004000
188 /* Parent inode is watched by some fsnotify listener */
190 #define DCACHE_DENTRY_KILLED 0x00008000
192 #define DCACHE_MOUNTED 0x00010000 /* is a mountpoint */
193 #define DCACHE_NEED_AUTOMOUNT 0x00020000 /* handle automount on this dir */
194 #define DCACHE_MANAGE_TRANSIT 0x00040000 /* manage transit from this dirent */
195 #define DCACHE_MANAGED_DENTRY \
196 (DCACHE_MOUNTED|DCACHE_NEED_AUTOMOUNT|DCACHE_MANAGE_TRANSIT)
198 #define DCACHE_LRU_LIST 0x00080000
200 #define DCACHE_ENTRY_TYPE 0x00700000
201 #define DCACHE_MISS_TYPE 0x00000000 /* Negative dentry (maybe fallthru to nowhere) */
202 #define DCACHE_WHITEOUT_TYPE 0x00100000 /* Whiteout dentry (stop pathwalk) */
203 #define DCACHE_DIRECTORY_TYPE 0x00200000 /* Normal directory */
204 #define DCACHE_AUTODIR_TYPE 0x00300000 /* Lookupless directory (presumed automount) */
205 #define DCACHE_REGULAR_TYPE 0x00400000 /* Regular file type (or fallthru to such) */
206 #define DCACHE_SPECIAL_TYPE 0x00500000 /* Other file type (or fallthru to such) */
207 #define DCACHE_SYMLINK_TYPE 0x00600000 /* Symlink (or fallthru to such) */
209 #define DCACHE_MAY_FREE 0x00800000
210 #define DCACHE_FALLTHRU 0x01000000 /* Fall through to lower layer */
211 #define DCACHE_ENCRYPTED_WITH_KEY 0x02000000 /* dir is encrypted with a valid key */
212 #define DCACHE_OP_REAL 0x04000000
214 #define DCACHE_PAR_LOOKUP 0x10000000 /* being looked up (with parent locked shared) */
215 #define DCACHE_DENTRY_CURSOR 0x20000000
217 extern seqlock_t rename_lock
;
220 * These are the low-level FS interfaces to the dcache..
222 extern void d_instantiate(struct dentry
*, struct inode
*);
223 extern struct dentry
* d_instantiate_unique(struct dentry
*, struct inode
*);
224 extern int d_instantiate_no_diralias(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
);
230 /* allocate/de-allocate */
231 extern struct dentry
* d_alloc(struct dentry
*, const struct qstr
*);
232 extern struct dentry
* d_alloc_pseudo(struct super_block
*, const struct qstr
*);
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 struct dentry
* d_exact_alias(struct dentry
*, struct inode
*);
238 extern struct dentry
*d_find_any_alias(struct inode
*inode
);
239 extern struct dentry
* d_obtain_alias(struct inode
*);
240 extern struct dentry
* d_obtain_root(struct inode
*);
241 extern void shrink_dcache_sb(struct super_block
*);
242 extern void shrink_dcache_parent(struct dentry
*);
243 extern void shrink_dcache_for_umount(struct super_block
*);
244 extern void d_invalidate(struct dentry
*);
246 /* only used at mount-time */
247 extern struct dentry
* d_make_root(struct inode
*);
249 /* <clickety>-<click> the ramfs-type tree */
250 extern void d_genocide(struct dentry
*);
252 extern void d_tmpfile(struct dentry
*, struct inode
*);
254 extern struct dentry
*d_find_alias(struct inode
*);
255 extern void d_prune_aliases(struct inode
*);
257 /* test whether we have any submounts in a subdir tree */
258 extern int path_has_submounts(const struct path
*);
261 * This adds the entry to the hash queues.
263 extern void d_rehash(struct dentry
*);
265 extern void d_add(struct dentry
*, struct inode
*);
267 extern void dentry_update_name_case(struct dentry
*, const struct qstr
*);
269 /* used for rename() and baskets */
270 extern void d_move(struct dentry
*, struct dentry
*);
271 extern void d_exchange(struct dentry
*, struct dentry
*);
272 extern struct dentry
*d_ancestor(struct dentry
*, struct dentry
*);
274 /* appendix may either be NULL or be used for transname suffixes */
275 extern struct dentry
*d_lookup(const struct dentry
*, const struct qstr
*);
276 extern struct dentry
*d_hash_and_lookup(struct dentry
*, struct qstr
*);
277 extern struct dentry
*__d_lookup(const struct dentry
*, const struct qstr
*);
278 extern struct dentry
*__d_lookup_rcu(const struct dentry
*parent
,
279 const struct qstr
*name
, unsigned *seq
);
281 static inline unsigned d_count(const struct dentry
*dentry
)
283 return dentry
->d_lockref
.count
;
287 * helper function for dentry_operations.d_dname() members
289 extern __printf(4, 5)
290 char *dynamic_dname(struct dentry
*, char *, int, const char *, ...);
291 extern char *simple_dname(struct dentry
*, char *, int);
293 extern char *__d_path(const struct path
*, const struct path
*, char *, int);
294 extern char *d_absolute_path(const struct path
*, char *, int);
295 extern char *d_path(const struct path
*, char *, int);
296 extern char *dentry_path_raw(struct dentry
*, char *, int);
297 extern char *dentry_path(struct dentry
*, char *, int);
299 /* Allocation counts.. */
302 * dget, dget_dlock - get a reference to a dentry
303 * @dentry: dentry to get a reference to
305 * Given a dentry or %NULL pointer increment the reference count
306 * if appropriate and return the dentry. A dentry will not be
307 * destroyed when it has references.
309 static inline struct dentry
*dget_dlock(struct dentry
*dentry
)
312 dentry
->d_lockref
.count
++;
316 static inline struct dentry
*dget(struct dentry
*dentry
)
319 lockref_get(&dentry
->d_lockref
);
323 extern struct dentry
*dget_parent(struct dentry
*dentry
);
326 * d_unhashed - is dentry hashed
327 * @dentry: entry to check
329 * Returns true if the dentry passed is not currently hashed.
332 static inline int d_unhashed(const struct dentry
*dentry
)
334 return hlist_bl_unhashed(&dentry
->d_hash
);
337 static inline int d_unlinked(const struct dentry
*dentry
)
339 return d_unhashed(dentry
) && !IS_ROOT(dentry
);
342 static inline int cant_mount(const struct dentry
*dentry
)
344 return (dentry
->d_flags
& DCACHE_CANT_MOUNT
);
347 static inline void dont_mount(struct dentry
*dentry
)
349 spin_lock(&dentry
->d_lock
);
350 dentry
->d_flags
|= DCACHE_CANT_MOUNT
;
351 spin_unlock(&dentry
->d_lock
);
354 extern void __d_lookup_done(struct dentry
*);
356 static inline int d_in_lookup(struct dentry
*dentry
)
358 return dentry
->d_flags
& DCACHE_PAR_LOOKUP
;
361 static inline void d_lookup_done(struct dentry
*dentry
)
363 if (unlikely(d_in_lookup(dentry
))) {
364 spin_lock(&dentry
->d_lock
);
365 __d_lookup_done(dentry
);
366 spin_unlock(&dentry
->d_lock
);
370 extern void dput(struct dentry
*);
372 static inline bool d_managed(const struct dentry
*dentry
)
374 return dentry
->d_flags
& DCACHE_MANAGED_DENTRY
;
377 static inline bool d_mountpoint(const struct dentry
*dentry
)
379 return dentry
->d_flags
& DCACHE_MOUNTED
;
383 * Directory cache entry type accessor functions.
385 static inline unsigned __d_entry_type(const struct dentry
*dentry
)
387 return dentry
->d_flags
& DCACHE_ENTRY_TYPE
;
390 static inline bool d_is_miss(const struct dentry
*dentry
)
392 return __d_entry_type(dentry
) == DCACHE_MISS_TYPE
;
395 static inline bool d_is_whiteout(const struct dentry
*dentry
)
397 return __d_entry_type(dentry
) == DCACHE_WHITEOUT_TYPE
;
400 static inline bool d_can_lookup(const struct dentry
*dentry
)
402 return __d_entry_type(dentry
) == DCACHE_DIRECTORY_TYPE
;
405 static inline bool d_is_autodir(const struct dentry
*dentry
)
407 return __d_entry_type(dentry
) == DCACHE_AUTODIR_TYPE
;
410 static inline bool d_is_dir(const struct dentry
*dentry
)
412 return d_can_lookup(dentry
) || d_is_autodir(dentry
);
415 static inline bool d_is_symlink(const struct dentry
*dentry
)
417 return __d_entry_type(dentry
) == DCACHE_SYMLINK_TYPE
;
420 static inline bool d_is_reg(const struct dentry
*dentry
)
422 return __d_entry_type(dentry
) == DCACHE_REGULAR_TYPE
;
425 static inline bool d_is_special(const struct dentry
*dentry
)
427 return __d_entry_type(dentry
) == DCACHE_SPECIAL_TYPE
;
430 static inline bool d_is_file(const struct dentry
*dentry
)
432 return d_is_reg(dentry
) || d_is_special(dentry
);
435 static inline bool d_is_negative(const struct dentry
*dentry
)
437 // TODO: check d_is_whiteout(dentry) also.
438 return d_is_miss(dentry
);
441 static inline bool d_is_positive(const struct dentry
*dentry
)
443 return !d_is_negative(dentry
);
447 * d_really_is_negative - Determine if a dentry is really negative (ignoring fallthroughs)
448 * @dentry: The dentry in question
450 * Returns true if the dentry represents either an absent name or a name that
451 * doesn't map to an inode (ie. ->d_inode is NULL). The dentry could represent
452 * a true miss, a whiteout that isn't represented by a 0,0 chardev or a
453 * fallthrough marker in an opaque directory.
455 * Note! (1) This should be used *only* by a filesystem to examine its own
456 * dentries. It should not be used to look at some other filesystem's
457 * dentries. (2) It should also be used in combination with d_inode() to get
458 * the inode. (3) The dentry may have something attached to ->d_lower and the
459 * type field of the flags may be set to something other than miss or whiteout.
461 static inline bool d_really_is_negative(const struct dentry
*dentry
)
463 return dentry
->d_inode
== NULL
;
467 * d_really_is_positive - Determine if a dentry is really positive (ignoring fallthroughs)
468 * @dentry: The dentry in question
470 * Returns true if the dentry represents a name that maps to an inode
471 * (ie. ->d_inode is not NULL). The dentry might still represent a whiteout if
472 * that is represented on medium as a 0,0 chardev.
474 * Note! (1) This should be used *only* by a filesystem to examine its own
475 * dentries. It should not be used to look at some other filesystem's
476 * dentries. (2) It should also be used in combination with d_inode() to get
479 static inline bool d_really_is_positive(const struct dentry
*dentry
)
481 return dentry
->d_inode
!= NULL
;
484 static inline int simple_positive(struct dentry
*dentry
)
486 return d_really_is_positive(dentry
) && !d_unhashed(dentry
);
489 extern void d_set_fallthru(struct dentry
*dentry
);
491 static inline bool d_is_fallthru(const struct dentry
*dentry
)
493 return dentry
->d_flags
& DCACHE_FALLTHRU
;
497 extern int sysctl_vfs_cache_pressure
;
499 static inline unsigned long vfs_pressure_ratio(unsigned long val
)
501 return mult_frac(val
, sysctl_vfs_cache_pressure
, 100);
505 * d_inode - Get the actual inode of this dentry
506 * @dentry: The dentry to query
508 * This is the helper normal filesystems should use to get at their own inodes
509 * in their own dentries and ignore the layering superimposed upon them.
511 static inline struct inode
*d_inode(const struct dentry
*dentry
)
513 return dentry
->d_inode
;
517 * d_inode_rcu - Get the actual inode of this dentry with ACCESS_ONCE()
518 * @dentry: The dentry to query
520 * This is the helper normal filesystems should use to get at their own inodes
521 * in their own dentries and ignore the layering superimposed upon them.
523 static inline struct inode
*d_inode_rcu(const struct dentry
*dentry
)
525 return ACCESS_ONCE(dentry
->d_inode
);
529 * d_backing_inode - Get upper or lower inode we should be using
530 * @upper: The upper layer
532 * This is the helper that should be used to get at the inode that will be used
533 * if this dentry were to be opened as a file. The inode may be on the upper
534 * dentry or it may be on a lower dentry pinned by the upper.
536 * Normal filesystems should not use this to access their own inodes.
538 static inline struct inode
*d_backing_inode(const struct dentry
*upper
)
540 struct inode
*inode
= upper
->d_inode
;
546 * d_backing_dentry - Get upper or lower dentry we should be using
547 * @upper: The upper layer
549 * This is the helper that should be used to get the dentry of the inode that
550 * will be used if this dentry were opened as a file. It may be the upper
551 * dentry or it may be a lower dentry pinned by the upper.
553 * Normal filesystems should not use this to access their own dentries.
555 static inline struct dentry
*d_backing_dentry(struct dentry
*upper
)
561 * d_real - Return the real dentry
562 * @dentry: the dentry to query
563 * @inode: inode to select the dentry from multiple layers (can be NULL)
564 * @flags: open flags to control copy-up behavior
566 * If dentry is on a union/overlay, then return the underlying, real dentry.
567 * Otherwise return the dentry itself.
569 * See also: Documentation/filesystems/vfs.txt
571 static inline struct dentry
*d_real(struct dentry
*dentry
,
572 const struct inode
*inode
,
575 if (unlikely(dentry
->d_flags
& DCACHE_OP_REAL
))
576 return dentry
->d_op
->d_real(dentry
, inode
, flags
);
582 * d_real_inode - Return the real inode
583 * @dentry: The dentry to query
585 * If dentry is on a union/overlay, then return the underlying, real inode.
586 * Otherwise return d_inode().
588 static inline struct inode
*d_real_inode(const struct dentry
*dentry
)
590 /* This usage of d_real() results in const dentry */
591 return d_backing_inode(d_real((struct dentry
*) dentry
, NULL
, 0));
595 #endif /* __LINUX_DCACHE_H */