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 } ____cacheline_aligned
;
166 * Locking rules for dentry_operations callbacks are to be found in
167 * Documentation/filesystems/Locking. Keep it updated!
169 * FUrther descriptions are found in Documentation/filesystems/vfs.txt.
170 * Keep it updated too!
173 /* d_flags entries */
174 #define DCACHE_OP_HASH 0x00000001
175 #define DCACHE_OP_COMPARE 0x00000002
176 #define DCACHE_OP_REVALIDATE 0x00000004
177 #define DCACHE_OP_DELETE 0x00000008
178 #define DCACHE_OP_PRUNE 0x00000010
180 #define DCACHE_DISCONNECTED 0x00000020
181 /* This dentry is possibly not currently connected to the dcache tree, in
182 * which case its parent will either be itself, or will have this flag as
183 * well. nfsd will not use a dentry with this bit set, but will first
184 * endeavour to clear the bit either by discovering that it is connected,
185 * or by performing lookup operations. Any filesystem which supports
186 * nfsd_operations MUST have a lookup function which, if it finds a
187 * directory inode with a DCACHE_DISCONNECTED dentry, will d_move that
188 * dentry into place and return that dentry rather than the passed one,
189 * typically using d_splice_alias. */
191 #define DCACHE_REFERENCED 0x00000040 /* Recently used, don't discard. */
192 #define DCACHE_RCUACCESS 0x00000080 /* Entry has ever been RCU-visible */
194 #define DCACHE_CANT_MOUNT 0x00000100
195 #define DCACHE_GENOCIDE 0x00000200
196 #define DCACHE_SHRINK_LIST 0x00000400
198 #define DCACHE_OP_WEAK_REVALIDATE 0x00000800
200 #define DCACHE_NFSFS_RENAMED 0x00001000
201 /* this dentry has been "silly renamed" and has to be deleted on the last
203 #define DCACHE_COOKIE 0x00002000 /* For use by dcookie subsystem */
204 #define DCACHE_FSNOTIFY_PARENT_WATCHED 0x00004000
205 /* Parent inode is watched by some fsnotify listener */
207 #define DCACHE_DENTRY_KILLED 0x00008000
209 #define DCACHE_MOUNTED 0x00010000 /* is a mountpoint */
210 #define DCACHE_NEED_AUTOMOUNT 0x00020000 /* handle automount on this dir */
211 #define DCACHE_MANAGE_TRANSIT 0x00040000 /* manage transit from this dirent */
212 #define DCACHE_MANAGED_DENTRY \
213 (DCACHE_MOUNTED|DCACHE_NEED_AUTOMOUNT|DCACHE_MANAGE_TRANSIT)
215 #define DCACHE_LRU_LIST 0x00080000
217 #define DCACHE_ENTRY_TYPE 0x00700000
218 #define DCACHE_MISS_TYPE 0x00000000 /* Negative dentry (maybe fallthru to nowhere) */
219 #define DCACHE_WHITEOUT_TYPE 0x00100000 /* Whiteout dentry (stop pathwalk) */
220 #define DCACHE_DIRECTORY_TYPE 0x00200000 /* Normal directory */
221 #define DCACHE_AUTODIR_TYPE 0x00300000 /* Lookupless directory (presumed automount) */
222 #define DCACHE_REGULAR_TYPE 0x00400000 /* Regular file type (or fallthru to such) */
223 #define DCACHE_SPECIAL_TYPE 0x00500000 /* Other file type (or fallthru to such) */
224 #define DCACHE_SYMLINK_TYPE 0x00600000 /* Symlink (or fallthru to such) */
226 #define DCACHE_MAY_FREE 0x00800000
227 #define DCACHE_FALLTHRU 0x01000000 /* Fall through to lower layer */
229 extern seqlock_t rename_lock
;
232 * These are the low-level FS interfaces to the dcache..
234 extern void d_instantiate(struct dentry
*, struct inode
*);
235 extern struct dentry
* d_instantiate_unique(struct dentry
*, struct inode
*);
236 extern int d_instantiate_no_diralias(struct dentry
*, struct inode
*);
237 extern void __d_drop(struct dentry
*dentry
);
238 extern void d_drop(struct dentry
*dentry
);
239 extern void d_delete(struct dentry
*);
240 extern void d_set_d_op(struct dentry
*dentry
, const struct dentry_operations
*op
);
242 /* allocate/de-allocate */
243 extern struct dentry
* d_alloc(struct dentry
*, const struct qstr
*);
244 extern struct dentry
* d_alloc_pseudo(struct super_block
*, const struct qstr
*);
245 extern struct dentry
* d_splice_alias(struct inode
*, struct dentry
*);
246 extern struct dentry
* d_add_ci(struct dentry
*, struct inode
*, struct qstr
*);
247 extern struct dentry
*d_find_any_alias(struct inode
*inode
);
248 extern struct dentry
* d_obtain_alias(struct inode
*);
249 extern struct dentry
* d_obtain_root(struct inode
*);
250 extern void shrink_dcache_sb(struct super_block
*);
251 extern void shrink_dcache_parent(struct dentry
*);
252 extern void shrink_dcache_for_umount(struct super_block
*);
253 extern void d_invalidate(struct dentry
*);
255 /* only used at mount-time */
256 extern struct dentry
* d_make_root(struct inode
*);
258 /* <clickety>-<click> the ramfs-type tree */
259 extern void d_genocide(struct dentry
*);
261 extern void d_tmpfile(struct dentry
*, struct inode
*);
263 extern struct dentry
*d_find_alias(struct inode
*);
264 extern void d_prune_aliases(struct inode
*);
266 /* test whether we have any submounts in a subdir tree */
267 extern int have_submounts(struct dentry
*);
270 * This adds the entry to the hash queues.
272 extern void d_rehash(struct dentry
*);
275 * d_add - add dentry to hash queues
276 * @entry: dentry to add
277 * @inode: The inode to attach to this dentry
279 * This adds the entry to the hash queues and initializes @inode.
280 * The entry was actually filled in earlier during d_alloc().
283 static inline void d_add(struct dentry
*entry
, struct inode
*inode
)
285 d_instantiate(entry
, inode
);
290 * d_add_unique - add dentry to hash queues without aliasing
291 * @entry: dentry to add
292 * @inode: The inode to attach to this dentry
294 * This adds the entry to the hash queues and initializes @inode.
295 * The entry was actually filled in earlier during d_alloc().
297 static inline struct dentry
*d_add_unique(struct dentry
*entry
, struct inode
*inode
)
301 res
= d_instantiate_unique(entry
, inode
);
302 d_rehash(res
!= NULL
? res
: entry
);
306 extern void dentry_update_name_case(struct dentry
*, struct qstr
*);
308 /* used for rename() and baskets */
309 extern void d_move(struct dentry
*, struct dentry
*);
310 extern void d_exchange(struct dentry
*, struct dentry
*);
311 extern struct dentry
*d_ancestor(struct dentry
*, struct dentry
*);
313 /* appendix may either be NULL or be used for transname suffixes */
314 extern struct dentry
*d_lookup(const struct dentry
*, const struct qstr
*);
315 extern struct dentry
*d_hash_and_lookup(struct dentry
*, struct qstr
*);
316 extern struct dentry
*__d_lookup(const struct dentry
*, const struct qstr
*);
317 extern struct dentry
*__d_lookup_rcu(const struct dentry
*parent
,
318 const struct qstr
*name
, unsigned *seq
);
320 static inline unsigned d_count(const struct dentry
*dentry
)
322 return dentry
->d_lockref
.count
;
326 * helper function for dentry_operations.d_dname() members
328 extern char *dynamic_dname(struct dentry
*, char *, int, const char *, ...);
329 extern char *simple_dname(struct dentry
*, char *, int);
331 extern char *__d_path(const struct path
*, const struct path
*, char *, int);
332 extern char *d_absolute_path(const struct path
*, char *, int);
333 extern char *d_path(const struct path
*, char *, int);
334 extern char *dentry_path_raw(struct dentry
*, char *, int);
335 extern char *dentry_path(struct dentry
*, char *, int);
337 /* Allocation counts.. */
340 * dget, dget_dlock - get a reference to a dentry
341 * @dentry: dentry to get a reference to
343 * Given a dentry or %NULL pointer increment the reference count
344 * if appropriate and return the dentry. A dentry will not be
345 * destroyed when it has references.
347 static inline struct dentry
*dget_dlock(struct dentry
*dentry
)
350 dentry
->d_lockref
.count
++;
354 static inline struct dentry
*dget(struct dentry
*dentry
)
357 lockref_get(&dentry
->d_lockref
);
361 extern struct dentry
*dget_parent(struct dentry
*dentry
);
364 * d_unhashed - is dentry hashed
365 * @dentry: entry to check
367 * Returns true if the dentry passed is not currently hashed.
370 static inline int d_unhashed(const struct dentry
*dentry
)
372 return hlist_bl_unhashed(&dentry
->d_hash
);
375 static inline int d_unlinked(const struct dentry
*dentry
)
377 return d_unhashed(dentry
) && !IS_ROOT(dentry
);
380 static inline int cant_mount(const struct dentry
*dentry
)
382 return (dentry
->d_flags
& DCACHE_CANT_MOUNT
);
385 static inline void dont_mount(struct dentry
*dentry
)
387 spin_lock(&dentry
->d_lock
);
388 dentry
->d_flags
|= DCACHE_CANT_MOUNT
;
389 spin_unlock(&dentry
->d_lock
);
392 extern void dput(struct dentry
*);
394 static inline bool d_managed(const struct dentry
*dentry
)
396 return dentry
->d_flags
& DCACHE_MANAGED_DENTRY
;
399 static inline bool d_mountpoint(const struct dentry
*dentry
)
401 return dentry
->d_flags
& DCACHE_MOUNTED
;
405 * Directory cache entry type accessor functions.
407 static inline unsigned __d_entry_type(const struct dentry
*dentry
)
409 unsigned type
= READ_ONCE(dentry
->d_flags
);
411 return type
& DCACHE_ENTRY_TYPE
;
414 static inline bool d_is_miss(const struct dentry
*dentry
)
416 return __d_entry_type(dentry
) == DCACHE_MISS_TYPE
;
419 static inline bool d_is_whiteout(const struct dentry
*dentry
)
421 return __d_entry_type(dentry
) == DCACHE_WHITEOUT_TYPE
;
424 static inline bool d_can_lookup(const struct dentry
*dentry
)
426 return __d_entry_type(dentry
) == DCACHE_DIRECTORY_TYPE
;
429 static inline bool d_is_autodir(const struct dentry
*dentry
)
431 return __d_entry_type(dentry
) == DCACHE_AUTODIR_TYPE
;
434 static inline bool d_is_dir(const struct dentry
*dentry
)
436 return d_can_lookup(dentry
) || d_is_autodir(dentry
);
439 static inline bool d_is_symlink(const struct dentry
*dentry
)
441 return __d_entry_type(dentry
) == DCACHE_SYMLINK_TYPE
;
444 static inline bool d_is_reg(const struct dentry
*dentry
)
446 return __d_entry_type(dentry
) == DCACHE_REGULAR_TYPE
;
449 static inline bool d_is_special(const struct dentry
*dentry
)
451 return __d_entry_type(dentry
) == DCACHE_SPECIAL_TYPE
;
454 static inline bool d_is_file(const struct dentry
*dentry
)
456 return d_is_reg(dentry
) || d_is_special(dentry
);
459 static inline bool d_is_negative(const struct dentry
*dentry
)
461 // TODO: check d_is_whiteout(dentry) also.
462 return d_is_miss(dentry
);
465 static inline bool d_is_positive(const struct dentry
*dentry
)
467 return !d_is_negative(dentry
);
471 * d_really_is_negative - Determine if a dentry is really negative (ignoring fallthroughs)
472 * @dentry: The dentry in question
474 * Returns true if the dentry represents either an absent name or a name that
475 * doesn't map to an inode (ie. ->d_inode is NULL). The dentry could represent
476 * a true miss, a whiteout that isn't represented by a 0,0 chardev or a
477 * fallthrough marker in an opaque directory.
479 * Note! (1) This should be used *only* by a filesystem to examine its own
480 * dentries. It should not be used to look at some other filesystem's
481 * dentries. (2) It should also be used in combination with d_inode() to get
482 * the inode. (3) The dentry may have something attached to ->d_lower and the
483 * type field of the flags may be set to something other than miss or whiteout.
485 static inline bool d_really_is_negative(const struct dentry
*dentry
)
487 return dentry
->d_inode
== NULL
;
491 * d_really_is_positive - Determine if a dentry is really positive (ignoring fallthroughs)
492 * @dentry: The dentry in question
494 * Returns true if the dentry represents a name that maps to an inode
495 * (ie. ->d_inode is not NULL). The dentry might still represent a whiteout if
496 * that is represented on medium as a 0,0 chardev.
498 * Note! (1) This should be used *only* by a filesystem to examine its own
499 * dentries. It should not be used to look at some other filesystem's
500 * dentries. (2) It should also be used in combination with d_inode() to get
503 static inline bool d_really_is_positive(const struct dentry
*dentry
)
505 return dentry
->d_inode
!= NULL
;
508 extern void d_set_fallthru(struct dentry
*dentry
);
510 static inline bool d_is_fallthru(const struct dentry
*dentry
)
512 return dentry
->d_flags
& DCACHE_FALLTHRU
;
516 extern int sysctl_vfs_cache_pressure
;
518 static inline unsigned long vfs_pressure_ratio(unsigned long val
)
520 return mult_frac(val
, sysctl_vfs_cache_pressure
, 100);
524 * d_inode - Get the actual inode of this dentry
525 * @dentry: The dentry to query
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.
530 static inline struct inode
*d_inode(const struct dentry
*dentry
)
532 return dentry
->d_inode
;
536 * d_inode_rcu - Get the actual inode of this dentry with ACCESS_ONCE()
537 * @dentry: The dentry to query
539 * This is the helper normal filesystems should use to get at their own inodes
540 * in their own dentries and ignore the layering superimposed upon them.
542 static inline struct inode
*d_inode_rcu(const struct dentry
*dentry
)
544 return ACCESS_ONCE(dentry
->d_inode
);
548 * d_backing_inode - Get upper or lower inode we should be using
549 * @upper: The upper layer
551 * This is the helper that should be used to get at the inode that will be used
552 * if this dentry were to be opened as a file. The inode may be on the upper
553 * dentry or it may be on a lower dentry pinned by the upper.
555 * Normal filesystems should not use this to access their own inodes.
557 static inline struct inode
*d_backing_inode(const struct dentry
*upper
)
559 struct inode
*inode
= upper
->d_inode
;
565 * d_backing_dentry - Get upper or lower dentry we should be using
566 * @upper: The upper layer
568 * This is the helper that should be used to get the dentry of the inode that
569 * will be used if this dentry were opened as a file. It may be the upper
570 * dentry or it may be a lower dentry pinned by the upper.
572 * Normal filesystems should not use this to access their own dentries.
574 static inline struct dentry
*d_backing_dentry(struct dentry
*upper
)
579 #endif /* __LINUX_DCACHE_H */