1 #ifndef __LINUX_DCACHE_H
2 #define __LINUX_DCACHE_H
4 #include <asm/atomic.h>
5 #include <linux/list.h>
6 #include <linux/rculist.h>
7 #include <linux/spinlock.h>
8 #include <linux/cache.h>
9 #include <linux/rcupdate.h>
16 * linux/include/linux/dcache.h
18 * Dirent cache data structures
20 * (C) Copyright 1997 Thomas Schoebel-Theuer,
21 * with heavy changes by Linus Torvalds
24 #define IS_ROOT(x) ((x) == (x)->d_parent)
27 * "quick string" -- eases parameter passing, but more importantly
28 * saves "metadata" about the string (ie length and the hash).
30 * hash comes first so it snuggles against d_parent in the
36 const unsigned char *name
;
39 struct dentry_stat_t
{
42 int age_limit
; /* age in seconds */
43 int want_pages
; /* pages requested by system */
46 extern struct dentry_stat_t dentry_stat
;
48 /* Name hashing routines. Initial hash value */
49 /* Hash courtesy of the R5 hash in reiserfs modulo sign bits */
50 #define init_name_hash() 0
52 /* partial hash update function. Assume roughly 4 bits per character */
53 static inline unsigned long
54 partial_name_hash(unsigned long c
, unsigned long prevhash
)
56 return (prevhash
+ (c
<< 4) + (c
>> 4)) * 11;
60 * Finally: cut down the number of bits to a int value (and try to avoid
63 static inline unsigned long end_name_hash(unsigned long hash
)
65 return (unsigned int) hash
;
68 /* Compute the hash for a name string. */
69 static inline unsigned int
70 full_name_hash(const unsigned char *name
, unsigned int len
)
72 unsigned long hash
= init_name_hash();
74 hash
= partial_name_hash(*name
++, hash
);
75 return end_name_hash(hash
);
79 * Try to keep struct dentry aligned on 64 byte cachelines (this will
80 * give reasonable cacheline footprint with larger lines without the
81 * large memory footprint increase).
84 #define DNAME_INLINE_LEN_MIN 32 /* 192 bytes */
86 #define DNAME_INLINE_LEN_MIN 40 /* 128 bytes */
91 unsigned int d_flags
; /* protected by d_lock */
92 spinlock_t d_lock
; /* per dentry lock */
94 struct inode
*d_inode
; /* Where the name belongs to - NULL is
97 * The next three fields are touched by __d_lookup. Place them here
98 * so they all fit in a cache line.
100 struct hlist_node d_hash
; /* lookup hash list */
101 struct dentry
*d_parent
; /* parent directory */
104 struct list_head d_lru
; /* LRU list */
106 * d_child and d_rcu can share memory
109 struct list_head d_child
; /* child of parent list */
110 struct rcu_head d_rcu
;
112 struct list_head d_subdirs
; /* our children */
113 struct list_head d_alias
; /* inode alias list */
114 unsigned long d_time
; /* used by d_revalidate */
115 const struct dentry_operations
*d_op
;
116 struct super_block
*d_sb
; /* The root of the dentry tree */
117 void *d_fsdata
; /* fs-specific data */
119 unsigned char d_iname
[DNAME_INLINE_LEN_MIN
]; /* small names */
123 * dentry->d_lock spinlock nesting subclasses:
128 enum dentry_d_lock_class
130 DENTRY_D_LOCK_NORMAL
, /* implicitly used by plain spin_lock() APIs. */
134 struct dentry_operations
{
135 int (*d_revalidate
)(struct dentry
*, struct nameidata
*);
136 int (*d_hash
)(struct dentry
*, struct qstr
*);
137 int (*d_compare
)(const struct dentry
*, const struct inode
*,
138 const struct dentry
*, const struct inode
*,
139 unsigned int, const char *, const struct qstr
*);
140 int (*d_delete
)(const struct dentry
*);
141 void (*d_release
)(struct dentry
*);
142 void (*d_iput
)(struct dentry
*, struct inode
*);
143 char *(*d_dname
)(struct dentry
*, char *, int);
147 * Locking rules for dentry_operations callbacks are to be found in
148 * Documentation/filesystems/Locking. Keep it updated!
150 * FUrther descriptions are found in Documentation/filesystems/vfs.txt.
151 * Keep it updated too!
154 /* d_flags entries */
155 #define DCACHE_AUTOFS_PENDING 0x0001 /* autofs: "under construction" */
156 #define DCACHE_NFSFS_RENAMED 0x0002 /* this dentry has been "silly
157 * renamed" and has to be
158 * deleted on the last dput()
160 #define DCACHE_DISCONNECTED 0x0004
161 /* This dentry is possibly not currently connected to the dcache tree,
162 * in which case its parent will either be itself, or will have this
163 * flag as well. nfsd will not use a dentry with this bit set, but will
164 * first endeavour to clear the bit either by discovering that it is
165 * connected, or by performing lookup operations. Any filesystem which
166 * supports nfsd_operations MUST have a lookup function which, if it finds
167 * a directory inode with a DCACHE_DISCONNECTED dentry, will d_move
168 * that dentry into place and return that dentry rather than the passed one,
169 * typically using d_splice_alias.
172 #define DCACHE_REFERENCED 0x0008 /* Recently used, don't discard. */
173 #define DCACHE_UNHASHED 0x0010
175 #define DCACHE_INOTIFY_PARENT_WATCHED 0x0020 /* Parent inode is watched by inotify */
177 #define DCACHE_COOKIE 0x0040 /* For use by dcookie subsystem */
179 #define DCACHE_FSNOTIFY_PARENT_WATCHED 0x0080 /* Parent inode is watched by some fsnotify listener */
181 #define DCACHE_CANT_MOUNT 0x0100
183 extern spinlock_t dcache_lock
;
184 extern seqlock_t rename_lock
;
187 * d_drop - drop a dentry
188 * @dentry: dentry to drop
190 * d_drop() unhashes the entry from the parent dentry hashes, so that it won't
191 * be found through a VFS lookup any more. Note that this is different from
192 * deleting the dentry - d_delete will try to mark the dentry negative if
193 * possible, giving a successful _negative_ lookup, while d_drop will
194 * just make the cache lookup fail.
196 * d_drop() is used mainly for stuff that wants to invalidate a dentry for some
197 * reason (NFS timeouts or autofs deletes).
199 * __d_drop requires dentry->d_lock.
202 static inline void __d_drop(struct dentry
*dentry
)
204 if (!(dentry
->d_flags
& DCACHE_UNHASHED
)) {
205 dentry
->d_flags
|= DCACHE_UNHASHED
;
206 hlist_del_rcu(&dentry
->d_hash
);
210 static inline void d_drop(struct dentry
*dentry
)
212 spin_lock(&dcache_lock
);
213 spin_lock(&dentry
->d_lock
);
215 spin_unlock(&dentry
->d_lock
);
216 spin_unlock(&dcache_lock
);
219 static inline int dname_external(struct dentry
*dentry
)
221 return dentry
->d_name
.name
!= dentry
->d_iname
;
225 * These are the low-level FS interfaces to the dcache..
227 extern void d_instantiate(struct dentry
*, struct inode
*);
228 extern struct dentry
* d_instantiate_unique(struct dentry
*, struct inode
*);
229 extern struct dentry
* d_materialise_unique(struct dentry
*, struct inode
*);
230 extern void d_delete(struct dentry
*);
232 /* allocate/de-allocate */
233 extern struct dentry
* d_alloc(struct dentry
*, const struct qstr
*);
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_obtain_alias(struct inode
*);
237 extern void shrink_dcache_sb(struct super_block
*);
238 extern void shrink_dcache_parent(struct dentry
*);
239 extern void shrink_dcache_for_umount(struct super_block
*);
240 extern int d_invalidate(struct dentry
*);
242 /* only used at mount-time */
243 extern struct dentry
* d_alloc_root(struct inode
*);
245 /* <clickety>-<click> the ramfs-type tree */
246 extern void d_genocide(struct dentry
*);
248 extern struct dentry
*d_find_alias(struct inode
*);
249 extern void d_prune_aliases(struct inode
*);
251 /* test whether we have any submounts in a subdir tree */
252 extern int have_submounts(struct dentry
*);
255 * This adds the entry to the hash queues.
257 extern void d_rehash(struct dentry
*);
260 * d_add - add dentry to hash queues
261 * @entry: dentry to add
262 * @inode: The inode to attach to this dentry
264 * This adds the entry to the hash queues and initializes @inode.
265 * The entry was actually filled in earlier during d_alloc().
268 static inline void d_add(struct dentry
*entry
, struct inode
*inode
)
270 d_instantiate(entry
, inode
);
275 * d_add_unique - add dentry to hash queues without aliasing
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().
282 static inline struct dentry
*d_add_unique(struct dentry
*entry
, struct inode
*inode
)
286 res
= d_instantiate_unique(entry
, inode
);
287 d_rehash(res
!= NULL
? res
: entry
);
291 extern void dentry_update_name_case(struct dentry
*, struct qstr
*);
293 /* used for rename() and baskets */
294 extern void d_move(struct dentry
*, struct dentry
*);
295 extern struct dentry
*d_ancestor(struct dentry
*, struct dentry
*);
297 /* appendix may either be NULL or be used for transname suffixes */
298 extern struct dentry
* d_lookup(struct dentry
*, struct qstr
*);
299 extern struct dentry
* __d_lookup(struct dentry
*, struct qstr
*);
300 extern struct dentry
* d_hash_and_lookup(struct dentry
*, struct qstr
*);
302 /* validate "insecure" dentry pointer */
303 extern int d_validate(struct dentry
*, struct dentry
*);
306 * helper function for dentry_operations.d_dname() members
308 extern char *dynamic_dname(struct dentry
*, char *, int, const char *, ...);
310 extern char *__d_path(const struct path
*path
, struct path
*root
, char *, int);
311 extern char *d_path(const struct path
*, char *, int);
312 extern char *d_path_with_unreachable(const struct path
*, char *, int);
313 extern char *__dentry_path(struct dentry
*, char *, int);
314 extern char *dentry_path(struct dentry
*, char *, int);
316 /* Allocation counts.. */
319 * dget, dget_locked - get a reference to a dentry
320 * @dentry: dentry to get a reference to
322 * Given a dentry or %NULL pointer increment the reference count
323 * if appropriate and return the dentry. A dentry will not be
324 * destroyed when it has references. dget() should never be
325 * called for dentries with zero reference counter. For these cases
326 * (preferably none, functions in dcache.c are sufficient for normal
327 * needs and they take necessary precautions) you should hold dcache_lock
328 * and call dget_locked() instead of dget().
331 static inline struct dentry
*dget(struct dentry
*dentry
)
334 BUG_ON(!atomic_read(&dentry
->d_count
));
335 atomic_inc(&dentry
->d_count
);
340 extern struct dentry
* dget_locked(struct dentry
*);
343 * d_unhashed - is dentry hashed
344 * @dentry: entry to check
346 * Returns true if the dentry passed is not currently hashed.
349 static inline int d_unhashed(struct dentry
*dentry
)
351 return (dentry
->d_flags
& DCACHE_UNHASHED
);
354 static inline int d_unlinked(struct dentry
*dentry
)
356 return d_unhashed(dentry
) && !IS_ROOT(dentry
);
359 static inline int cant_mount(struct dentry
*dentry
)
361 return (dentry
->d_flags
& DCACHE_CANT_MOUNT
);
364 static inline void dont_mount(struct dentry
*dentry
)
366 spin_lock(&dentry
->d_lock
);
367 dentry
->d_flags
|= DCACHE_CANT_MOUNT
;
368 spin_unlock(&dentry
->d_lock
);
371 static inline struct dentry
*dget_parent(struct dentry
*dentry
)
375 spin_lock(&dentry
->d_lock
);
376 ret
= dget(dentry
->d_parent
);
377 spin_unlock(&dentry
->d_lock
);
381 extern void dput(struct dentry
*);
383 static inline int d_mountpoint(struct dentry
*dentry
)
385 return dentry
->d_mounted
;
388 extern struct vfsmount
*lookup_mnt(struct path
*);
389 extern struct dentry
*lookup_create(struct nameidata
*nd
, int is_dir
);
391 extern int sysctl_vfs_cache_pressure
;
393 #endif /* __LINUX_DCACHE_H */