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>
18 * linux/include/linux/dcache.h
20 * Dirent cache data structures
22 * (C) Copyright 1997 Thomas Schoebel-Theuer,
23 * with heavy changes by Linus Torvalds
26 #define IS_ROOT(x) ((x) == (x)->d_parent)
28 /* The hash is always the low bits of hash_len */
29 #ifdef __LITTLE_ENDIAN
30 #define HASH_LEN_DECLARE u32 hash; u32 len
31 #define bytemask_from_count(cnt) (~(~0ul << (cnt)*8))
33 #define HASH_LEN_DECLARE u32 len; u32 hash
34 #define bytemask_from_count(cnt) (~(~0ul >> (cnt)*8))
38 * "quick string" -- eases parameter passing, but more importantly
39 * saves "metadata" about the string (ie length and the hash).
41 * hash comes first so it snuggles against d_parent in the
51 const unsigned char *name
;
54 #define QSTR_INIT(n,l) { { { .len = l } }, .name = n }
55 #define hashlen_hash(hashlen) ((u32) (hashlen))
56 #define hashlen_len(hashlen) ((u32)((hashlen) >> 32))
57 #define hashlen_create(hash,len) (((u64)(len)<<32)|(u32)(hash))
59 struct dentry_stat_t
{
62 long age_limit
; /* age in seconds */
63 long want_pages
; /* pages requested by system */
66 extern struct dentry_stat_t dentry_stat
;
68 /* Name hashing routines. Initial hash value */
69 /* Hash courtesy of the R5 hash in reiserfs modulo sign bits */
70 #define init_name_hash() 0
72 /* partial hash update function. Assume roughly 4 bits per character */
73 static inline unsigned long
74 partial_name_hash(unsigned long c
, unsigned long prevhash
)
76 return (prevhash
+ (c
<< 4) + (c
>> 4)) * 11;
80 * Finally: cut down the number of bits to a int value (and try to avoid
83 static inline unsigned long end_name_hash(unsigned long hash
)
85 return (unsigned int) hash
;
88 /* Compute the hash for a name string. */
89 extern unsigned int full_name_hash(const unsigned char *, unsigned int);
92 * Try to keep struct dentry aligned on 64 byte cachelines (this will
93 * give reasonable cacheline footprint with larger lines without the
94 * large memory footprint increase).
97 # define DNAME_INLINE_LEN 32 /* 192 bytes */
100 # define DNAME_INLINE_LEN 36 /* 128 bytes */
102 # define DNAME_INLINE_LEN 40 /* 128 bytes */
106 #define d_lock d_lockref.lock
109 /* RCU lookup touched fields */
110 unsigned int d_flags
; /* protected by d_lock */
111 seqcount_t d_seq
; /* per dentry seqlock */
112 struct hlist_bl_node d_hash
; /* lookup hash list */
113 struct dentry
*d_parent
; /* parent directory */
115 struct inode
*d_inode
; /* Where the name belongs to - NULL is
117 unsigned char d_iname
[DNAME_INLINE_LEN
]; /* small names */
119 /* Ref lookup also touches following */
120 struct lockref d_lockref
; /* per-dentry lock and refcount */
121 const struct dentry_operations
*d_op
;
122 struct super_block
*d_sb
; /* The root of the dentry tree */
123 unsigned long d_time
; /* used by d_revalidate */
124 void *d_fsdata
; /* fs-specific data */
126 struct list_head d_lru
; /* LRU list */
127 struct list_head d_child
; /* child of parent list */
128 struct list_head d_subdirs
; /* our children */
130 * d_alias and d_rcu can share memory
133 struct hlist_node d_alias
; /* inode alias list */
134 struct rcu_head d_rcu
;
139 * dentry->d_lock spinlock nesting subclasses:
144 enum dentry_d_lock_class
146 DENTRY_D_LOCK_NORMAL
, /* implicitly used by plain spin_lock() APIs. */
150 struct dentry_operations
{
151 int (*d_revalidate
)(struct dentry
*, unsigned int);
152 int (*d_weak_revalidate
)(struct dentry
*, unsigned int);
153 int (*d_hash
)(const struct dentry
*, struct qstr
*);
154 int (*d_compare
)(const struct dentry
*, const struct dentry
*,
155 unsigned int, const char *, const struct qstr
*);
156 int (*d_delete
)(const struct dentry
*);
157 void (*d_release
)(struct dentry
*);
158 void (*d_prune
)(struct dentry
*);
159 void (*d_iput
)(struct dentry
*, struct inode
*);
160 char *(*d_dname
)(struct dentry
*, char *, int);
161 struct vfsmount
*(*d_automount
)(struct path
*);
162 int (*d_manage
)(struct dentry
*, bool);
163 struct inode
*(*d_select_inode
)(struct dentry
*, unsigned);
164 struct dentry
*(*d_real
)(struct dentry
*, struct inode
*);
165 } ____cacheline_aligned
;
168 * Locking rules for dentry_operations callbacks are to be found in
169 * Documentation/filesystems/Locking. Keep it updated!
171 * FUrther descriptions are found in Documentation/filesystems/vfs.txt.
172 * Keep it updated too!
175 /* d_flags entries */
176 #define DCACHE_OP_HASH 0x00000001
177 #define DCACHE_OP_COMPARE 0x00000002
178 #define DCACHE_OP_REVALIDATE 0x00000004
179 #define DCACHE_OP_DELETE 0x00000008
180 #define DCACHE_OP_PRUNE 0x00000010
182 #define DCACHE_DISCONNECTED 0x00000020
183 /* This dentry is possibly not currently connected to the dcache tree, in
184 * which case its parent will either be itself, or will have this flag as
185 * well. nfsd will not use a dentry with this bit set, but will first
186 * endeavour to clear the bit either by discovering that it is connected,
187 * or by performing lookup operations. Any filesystem which supports
188 * nfsd_operations MUST have a lookup function which, if it finds a
189 * directory inode with a DCACHE_DISCONNECTED dentry, will d_move that
190 * dentry into place and return that dentry rather than the passed one,
191 * typically using d_splice_alias. */
193 #define DCACHE_REFERENCED 0x00000040 /* Recently used, don't discard. */
194 #define DCACHE_RCUACCESS 0x00000080 /* Entry has ever been RCU-visible */
196 #define DCACHE_CANT_MOUNT 0x00000100
197 #define DCACHE_GENOCIDE 0x00000200
198 #define DCACHE_SHRINK_LIST 0x00000400
200 #define DCACHE_OP_WEAK_REVALIDATE 0x00000800
202 #define DCACHE_NFSFS_RENAMED 0x00001000
203 /* this dentry has been "silly renamed" and has to be deleted on the last
205 #define DCACHE_COOKIE 0x00002000 /* For use by dcookie subsystem */
206 #define DCACHE_FSNOTIFY_PARENT_WATCHED 0x00004000
207 /* Parent inode is watched by some fsnotify listener */
209 #define DCACHE_DENTRY_KILLED 0x00008000
211 #define DCACHE_MOUNTED 0x00010000 /* is a mountpoint */
212 #define DCACHE_NEED_AUTOMOUNT 0x00020000 /* handle automount on this dir */
213 #define DCACHE_MANAGE_TRANSIT 0x00040000 /* manage transit from this dirent */
214 #define DCACHE_MANAGED_DENTRY \
215 (DCACHE_MOUNTED|DCACHE_NEED_AUTOMOUNT|DCACHE_MANAGE_TRANSIT)
217 #define DCACHE_LRU_LIST 0x00080000
219 #define DCACHE_ENTRY_TYPE 0x00700000
220 #define DCACHE_MISS_TYPE 0x00000000 /* Negative dentry (maybe fallthru to nowhere) */
221 #define DCACHE_WHITEOUT_TYPE 0x00100000 /* Whiteout dentry (stop pathwalk) */
222 #define DCACHE_DIRECTORY_TYPE 0x00200000 /* Normal directory */
223 #define DCACHE_AUTODIR_TYPE 0x00300000 /* Lookupless directory (presumed automount) */
224 #define DCACHE_REGULAR_TYPE 0x00400000 /* Regular file type (or fallthru to such) */
225 #define DCACHE_SPECIAL_TYPE 0x00500000 /* Other file type (or fallthru to such) */
226 #define DCACHE_SYMLINK_TYPE 0x00600000 /* Symlink (or fallthru to such) */
228 #define DCACHE_MAY_FREE 0x00800000
229 #define DCACHE_FALLTHRU 0x01000000 /* Fall through to lower layer */
230 #define DCACHE_OP_SELECT_INODE 0x02000000 /* Unioned entry: dcache op selects inode */
232 #define DCACHE_ENCRYPTED_WITH_KEY 0x04000000 /* dir is encrypted with a valid key */
233 #define DCACHE_OP_REAL 0x08000000
235 #define DCACHE_PAR_LOOKUP 0x10000000 /* being looked up (with parent locked shared) */
237 extern seqlock_t rename_lock
;
240 * These are the low-level FS interfaces to the dcache..
242 extern void d_instantiate(struct dentry
*, struct inode
*);
243 extern struct dentry
* d_instantiate_unique(struct dentry
*, struct inode
*);
244 extern int d_instantiate_no_diralias(struct dentry
*, struct inode
*);
245 extern void __d_drop(struct dentry
*dentry
);
246 extern void d_drop(struct dentry
*dentry
);
247 extern void d_delete(struct dentry
*);
248 extern void d_set_d_op(struct dentry
*dentry
, const struct dentry_operations
*op
);
250 /* allocate/de-allocate */
251 extern struct dentry
* d_alloc(struct dentry
*, const struct qstr
*);
252 extern struct dentry
* d_alloc_pseudo(struct super_block
*, const struct qstr
*);
253 extern struct dentry
* d_splice_alias(struct inode
*, struct dentry
*);
254 extern struct dentry
* d_add_ci(struct dentry
*, struct inode
*, struct qstr
*);
255 extern struct dentry
* d_exact_alias(struct dentry
*, struct inode
*);
256 extern struct dentry
*d_find_any_alias(struct inode
*inode
);
257 extern struct dentry
* d_obtain_alias(struct inode
*);
258 extern struct dentry
* d_obtain_root(struct inode
*);
259 extern void shrink_dcache_sb(struct super_block
*);
260 extern void shrink_dcache_parent(struct dentry
*);
261 extern void shrink_dcache_for_umount(struct super_block
*);
262 extern void d_invalidate(struct dentry
*);
264 /* only used at mount-time */
265 extern struct dentry
* d_make_root(struct inode
*);
267 /* <clickety>-<click> the ramfs-type tree */
268 extern void d_genocide(struct dentry
*);
270 extern void d_tmpfile(struct dentry
*, struct inode
*);
272 extern struct dentry
*d_find_alias(struct inode
*);
273 extern void d_prune_aliases(struct inode
*);
275 /* test whether we have any submounts in a subdir tree */
276 extern int have_submounts(struct dentry
*);
279 * This adds the entry to the hash queues.
281 extern void d_rehash(struct dentry
*);
283 extern void d_add(struct dentry
*, struct inode
*);
285 extern void dentry_update_name_case(struct dentry
*, struct qstr
*);
287 /* used for rename() and baskets */
288 extern void d_move(struct dentry
*, struct dentry
*);
289 extern void d_exchange(struct dentry
*, struct dentry
*);
290 extern struct dentry
*d_ancestor(struct dentry
*, struct dentry
*);
292 /* appendix may either be NULL or be used for transname suffixes */
293 extern struct dentry
*d_lookup(const struct dentry
*, const struct qstr
*);
294 extern struct dentry
*d_hash_and_lookup(struct dentry
*, struct qstr
*);
295 extern struct dentry
*__d_lookup(const struct dentry
*, const struct qstr
*);
296 extern struct dentry
*__d_lookup_rcu(const struct dentry
*parent
,
297 const struct qstr
*name
, unsigned *seq
);
299 static inline unsigned d_count(const struct dentry
*dentry
)
301 return dentry
->d_lockref
.count
;
305 * helper function for dentry_operations.d_dname() members
307 extern __printf(4, 5)
308 char *dynamic_dname(struct dentry
*, char *, int, const char *, ...);
309 extern char *simple_dname(struct dentry
*, char *, int);
311 extern char *__d_path(const struct path
*, const struct path
*, char *, int);
312 extern char *d_absolute_path(const struct path
*, char *, int);
313 extern char *d_path(const struct path
*, char *, int);
314 extern char *dentry_path_raw(struct dentry
*, char *, int);
315 extern char *dentry_path(struct dentry
*, char *, int);
317 /* Allocation counts.. */
320 * dget, dget_dlock - get a reference to a dentry
321 * @dentry: dentry to get a reference to
323 * Given a dentry or %NULL pointer increment the reference count
324 * if appropriate and return the dentry. A dentry will not be
325 * destroyed when it has references.
327 static inline struct dentry
*dget_dlock(struct dentry
*dentry
)
330 dentry
->d_lockref
.count
++;
334 static inline struct dentry
*dget(struct dentry
*dentry
)
337 lockref_get(&dentry
->d_lockref
);
341 extern struct dentry
*dget_parent(struct dentry
*dentry
);
344 * d_unhashed - is dentry hashed
345 * @dentry: entry to check
347 * Returns true if the dentry passed is not currently hashed.
350 static inline int d_unhashed(const struct dentry
*dentry
)
352 return hlist_bl_unhashed(&dentry
->d_hash
);
355 static inline int d_unlinked(const struct dentry
*dentry
)
357 return d_unhashed(dentry
) && !IS_ROOT(dentry
);
360 static inline int cant_mount(const struct dentry
*dentry
)
362 return (dentry
->d_flags
& DCACHE_CANT_MOUNT
);
365 static inline void dont_mount(struct dentry
*dentry
)
367 spin_lock(&dentry
->d_lock
);
368 dentry
->d_flags
|= DCACHE_CANT_MOUNT
;
369 spin_unlock(&dentry
->d_lock
);
372 extern void __d_lookup_done(struct dentry
*);
374 static inline int d_in_lookup(struct dentry
*dentry
)
376 return dentry
->d_flags
& DCACHE_PAR_LOOKUP
;
379 static inline void d_lookup_done(struct dentry
*dentry
)
381 if (unlikely(d_in_lookup(dentry
))) {
382 spin_lock(&dentry
->d_lock
);
383 __d_lookup_done(dentry
);
384 spin_unlock(&dentry
->d_lock
);
388 extern void dput(struct dentry
*);
390 static inline bool d_managed(const struct dentry
*dentry
)
392 return dentry
->d_flags
& DCACHE_MANAGED_DENTRY
;
395 static inline bool d_mountpoint(const struct dentry
*dentry
)
397 return dentry
->d_flags
& DCACHE_MOUNTED
;
401 * Directory cache entry type accessor functions.
403 static inline unsigned __d_entry_type(const struct dentry
*dentry
)
405 return dentry
->d_flags
& DCACHE_ENTRY_TYPE
;
408 static inline bool d_is_miss(const struct dentry
*dentry
)
410 return __d_entry_type(dentry
) == DCACHE_MISS_TYPE
;
413 static inline bool d_is_whiteout(const struct dentry
*dentry
)
415 return __d_entry_type(dentry
) == DCACHE_WHITEOUT_TYPE
;
418 static inline bool d_can_lookup(const struct dentry
*dentry
)
420 return __d_entry_type(dentry
) == DCACHE_DIRECTORY_TYPE
;
423 static inline bool d_is_autodir(const struct dentry
*dentry
)
425 return __d_entry_type(dentry
) == DCACHE_AUTODIR_TYPE
;
428 static inline bool d_is_dir(const struct dentry
*dentry
)
430 return d_can_lookup(dentry
) || d_is_autodir(dentry
);
433 static inline bool d_is_symlink(const struct dentry
*dentry
)
435 return __d_entry_type(dentry
) == DCACHE_SYMLINK_TYPE
;
438 static inline bool d_is_reg(const struct dentry
*dentry
)
440 return __d_entry_type(dentry
) == DCACHE_REGULAR_TYPE
;
443 static inline bool d_is_special(const struct dentry
*dentry
)
445 return __d_entry_type(dentry
) == DCACHE_SPECIAL_TYPE
;
448 static inline bool d_is_file(const struct dentry
*dentry
)
450 return d_is_reg(dentry
) || d_is_special(dentry
);
453 static inline bool d_is_negative(const struct dentry
*dentry
)
455 // TODO: check d_is_whiteout(dentry) also.
456 return d_is_miss(dentry
);
459 static inline bool d_is_positive(const struct dentry
*dentry
)
461 return !d_is_negative(dentry
);
465 * d_really_is_negative - Determine if a dentry is really negative (ignoring fallthroughs)
466 * @dentry: The dentry in question
468 * Returns true if the dentry represents either an absent name or a name that
469 * doesn't map to an inode (ie. ->d_inode is NULL). The dentry could represent
470 * a true miss, a whiteout that isn't represented by a 0,0 chardev or a
471 * fallthrough marker in an opaque directory.
473 * Note! (1) This should be used *only* by a filesystem to examine its own
474 * dentries. It should not be used to look at some other filesystem's
475 * dentries. (2) It should also be used in combination with d_inode() to get
476 * the inode. (3) The dentry may have something attached to ->d_lower and the
477 * type field of the flags may be set to something other than miss or whiteout.
479 static inline bool d_really_is_negative(const struct dentry
*dentry
)
481 return dentry
->d_inode
== NULL
;
485 * d_really_is_positive - Determine if a dentry is really positive (ignoring fallthroughs)
486 * @dentry: The dentry in question
488 * Returns true if the dentry represents a name that maps to an inode
489 * (ie. ->d_inode is not NULL). The dentry might still represent a whiteout if
490 * that is represented on medium as a 0,0 chardev.
492 * Note! (1) This should be used *only* by a filesystem to examine its own
493 * dentries. It should not be used to look at some other filesystem's
494 * dentries. (2) It should also be used in combination with d_inode() to get
497 static inline bool d_really_is_positive(const struct dentry
*dentry
)
499 return dentry
->d_inode
!= NULL
;
502 static inline int simple_positive(struct dentry
*dentry
)
504 return d_really_is_positive(dentry
) && !d_unhashed(dentry
);
507 extern void d_set_fallthru(struct dentry
*dentry
);
509 static inline bool d_is_fallthru(const struct dentry
*dentry
)
511 return dentry
->d_flags
& DCACHE_FALLTHRU
;
515 extern int sysctl_vfs_cache_pressure
;
517 static inline unsigned long vfs_pressure_ratio(unsigned long val
)
519 return mult_frac(val
, sysctl_vfs_cache_pressure
, 100);
523 * d_inode - Get the actual inode of this dentry
524 * @dentry: The dentry to query
526 * This is the helper normal filesystems should use to get at their own inodes
527 * in their own dentries and ignore the layering superimposed upon them.
529 static inline struct inode
*d_inode(const struct dentry
*dentry
)
531 return dentry
->d_inode
;
535 * d_inode_rcu - Get the actual inode of this dentry with ACCESS_ONCE()
536 * @dentry: The dentry to query
538 * This is the helper normal filesystems should use to get at their own inodes
539 * in their own dentries and ignore the layering superimposed upon them.
541 static inline struct inode
*d_inode_rcu(const struct dentry
*dentry
)
543 return ACCESS_ONCE(dentry
->d_inode
);
547 * d_backing_inode - Get upper or lower inode we should be using
548 * @upper: The upper layer
550 * This is the helper that should be used to get at the inode that will be used
551 * if this dentry were to be opened as a file. The inode may be on the upper
552 * dentry or it may be on a lower dentry pinned by the upper.
554 * Normal filesystems should not use this to access their own inodes.
556 static inline struct inode
*d_backing_inode(const struct dentry
*upper
)
558 struct inode
*inode
= upper
->d_inode
;
564 * d_backing_dentry - Get upper or lower dentry we should be using
565 * @upper: The upper layer
567 * This is the helper that should be used to get the dentry of the inode that
568 * will be used if this dentry were opened as a file. It may be the upper
569 * dentry or it may be a lower dentry pinned by the upper.
571 * Normal filesystems should not use this to access their own dentries.
573 static inline struct dentry
*d_backing_dentry(struct dentry
*upper
)
578 static inline struct dentry
*d_real(struct dentry
*dentry
)
580 if (unlikely(dentry
->d_flags
& DCACHE_OP_REAL
))
581 return dentry
->d_op
->d_real(dentry
, NULL
);
586 #endif /* __LINUX_DCACHE_H */