1 #ifndef __LINUX_DCACHE_H
2 #define __LINUX_DCACHE_H
6 #include <asm/atomic.h>
7 #include <linux/list.h>
8 #include <linux/spinlock.h>
9 #include <linux/cache.h>
10 #include <linux/rcupdate.h>
17 * linux/include/linux/dcache.h
19 * Dirent cache data structures
21 * (C) Copyright 1997 Thomas Schoebel-Theuer,
22 * with heavy changes by Linus Torvalds
25 #define IS_ROOT(x) ((x) == (x)->d_parent)
28 * "quick string" -- eases parameter passing, but more importantly
29 * saves "metadata" about the string (ie length and the hash).
31 * hash comes first so it snuggles against d_parent in the
37 const unsigned char *name
;
40 struct dentry_stat_t
{
43 int age_limit
; /* age in seconds */
44 int want_pages
; /* pages requested by system */
47 extern struct dentry_stat_t dentry_stat
;
49 /* Name hashing routines. Initial hash value */
50 /* Hash courtesy of the R5 hash in reiserfs modulo sign bits */
51 #define init_name_hash() 0
53 /* partial hash update function. Assume roughly 4 bits per character */
54 static inline unsigned long
55 partial_name_hash(unsigned long c
, unsigned long prevhash
)
57 return (prevhash
+ (c
<< 4) + (c
>> 4)) * 11;
61 * Finally: cut down the number of bits to a int value (and try to avoid
64 static inline unsigned long end_name_hash(unsigned long hash
)
66 return (unsigned int) hash
;
69 /* Compute the hash for a name string. */
70 static inline unsigned int
71 full_name_hash(const unsigned char *name
, unsigned int len
)
73 unsigned long hash
= init_name_hash();
75 hash
= partial_name_hash(*name
++, hash
);
76 return end_name_hash(hash
);
79 struct dcookie_struct
;
81 #define DNAME_INLINE_LEN_MIN 36
85 unsigned int d_flags
; /* protected by d_lock */
86 spinlock_t d_lock
; /* per dentry lock */
87 struct inode
*d_inode
; /* Where the name belongs to - NULL is
90 * The next three fields are touched by __d_lookup. Place them here
91 * so they all fit in a cache line.
93 struct hlist_node d_hash
; /* lookup hash list */
94 struct dentry
*d_parent
; /* parent directory */
97 struct list_head d_lru
; /* LRU list */
99 * d_child and d_rcu can share memory
102 struct list_head d_child
; /* child of parent list */
103 struct rcu_head d_rcu
;
105 struct list_head d_subdirs
; /* our children */
106 struct list_head d_alias
; /* inode alias list */
107 unsigned long d_time
; /* used by d_revalidate */
108 struct dentry_operations
*d_op
;
109 struct super_block
*d_sb
; /* The root of the dentry tree */
110 void *d_fsdata
; /* fs-specific data */
111 struct dcookie_struct
*d_cookie
; /* cookie, if any */
113 unsigned char d_iname
[DNAME_INLINE_LEN_MIN
]; /* small names */
116 struct dentry_operations
{
117 int (*d_revalidate
)(struct dentry
*, struct nameidata
*);
118 int (*d_hash
) (struct dentry
*, struct qstr
*);
119 int (*d_compare
) (struct dentry
*, struct qstr
*, struct qstr
*);
120 int (*d_delete
)(struct dentry
*);
121 void (*d_release
)(struct dentry
*);
122 void (*d_iput
)(struct dentry
*, struct inode
*);
125 /* the dentry parameter passed to d_hash and d_compare is the parent
126 * directory of the entries to be compared. It is used in case these
127 * functions need any directory specific information for determining
128 * equivalency classes. Using the dentry itself might not work, as it
129 * might be a negative dentry which has no information associated with
134 big lock dcache_lock d_lock may block
135 d_revalidate: no no no yes
137 d_compare: no yes yes no
138 d_delete: no yes no no
139 d_release: no no no yes
143 /* d_flags entries */
144 #define DCACHE_AUTOFS_PENDING 0x0001 /* autofs: "under construction" */
145 #define DCACHE_NFSFS_RENAMED 0x0002 /* this dentry has been "silly
146 * renamed" and has to be
147 * deleted on the last dput()
149 #define DCACHE_DISCONNECTED 0x0004
150 /* This dentry is possibly not currently connected to the dcache tree,
151 * in which case its parent will either be itself, or will have this
152 * flag as well. nfsd will not use a dentry with this bit set, but will
153 * first endeavour to clear the bit either by discovering that it is
154 * connected, or by performing lookup operations. Any filesystem which
155 * supports nfsd_operations MUST have a lookup function which, if it finds
156 * a directory inode with a DCACHE_DISCONNECTED dentry, will d_move
157 * that dentry into place and return that dentry rather than the passed one,
158 * typically using d_splice_alias.
161 #define DCACHE_REFERENCED 0x0008 /* Recently used, don't discard. */
162 #define DCACHE_UNHASHED 0x0010
164 extern spinlock_t dcache_lock
;
167 * d_drop - drop a dentry
168 * @dentry: dentry to drop
170 * d_drop() unhashes the entry from the parent dentry hashes, so that it won't
171 * be found through a VFS lookup any more. Note that this is different from
172 * deleting the dentry - d_delete will try to mark the dentry negative if
173 * possible, giving a successful _negative_ lookup, while d_drop will
174 * just make the cache lookup fail.
176 * d_drop() is used mainly for stuff that wants to invalidate a dentry for some
177 * reason (NFS timeouts or autofs deletes).
179 * __d_drop requires dentry->d_lock.
182 static inline void __d_drop(struct dentry
*dentry
)
184 if (!(dentry
->d_flags
& DCACHE_UNHASHED
)) {
185 dentry
->d_flags
|= DCACHE_UNHASHED
;
186 hlist_del_rcu(&dentry
->d_hash
);
190 static inline void d_drop(struct dentry
*dentry
)
192 spin_lock(&dcache_lock
);
193 spin_lock(&dentry
->d_lock
);
195 spin_unlock(&dentry
->d_lock
);
196 spin_unlock(&dcache_lock
);
199 static inline int dname_external(struct dentry
*dentry
)
201 return dentry
->d_name
.name
!= dentry
->d_iname
;
205 * These are the low-level FS interfaces to the dcache..
207 extern void d_instantiate(struct dentry
*, struct inode
*);
208 extern struct dentry
* d_instantiate_unique(struct dentry
*, struct inode
*);
209 extern void d_delete(struct dentry
*);
211 /* allocate/de-allocate */
212 extern struct dentry
* d_alloc(struct dentry
*, const struct qstr
*);
213 extern struct dentry
* d_alloc_anon(struct inode
*);
214 extern struct dentry
* d_splice_alias(struct inode
*, struct dentry
*);
215 extern void shrink_dcache_sb(struct super_block
*);
216 extern void shrink_dcache_parent(struct dentry
*);
217 extern void shrink_dcache_anon(struct hlist_head
*);
218 extern int d_invalidate(struct dentry
*);
220 /* only used at mount-time */
221 extern struct dentry
* d_alloc_root(struct inode
*);
223 /* <clickety>-<click> the ramfs-type tree */
224 extern void d_genocide(struct dentry
*);
226 extern struct dentry
*d_find_alias(struct inode
*);
227 extern void d_prune_aliases(struct inode
*);
229 /* test whether we have any submounts in a subdir tree */
230 extern int have_submounts(struct dentry
*);
233 * This adds the entry to the hash queues.
235 extern void d_rehash(struct dentry
*);
238 * d_add - add dentry to hash queues
239 * @entry: dentry to add
240 * @inode: The inode to attach to this dentry
242 * This adds the entry to the hash queues and initializes @inode.
243 * The entry was actually filled in earlier during d_alloc().
246 static inline void d_add(struct dentry
*entry
, struct inode
*inode
)
248 d_instantiate(entry
, inode
);
253 * d_add_unique - add dentry to hash queues without aliasing
254 * @entry: dentry to add
255 * @inode: The inode to attach to this dentry
257 * This adds the entry to the hash queues and initializes @inode.
258 * The entry was actually filled in earlier during d_alloc().
260 static inline struct dentry
*d_add_unique(struct dentry
*entry
, struct inode
*inode
)
264 res
= d_instantiate_unique(entry
, inode
);
265 d_rehash(res
!= NULL
? res
: entry
);
269 /* used for rename() and baskets */
270 extern void d_move(struct dentry
*, struct dentry
*);
272 /* appendix may either be NULL or be used for transname suffixes */
273 extern struct dentry
* d_lookup(struct dentry
*, struct qstr
*);
274 extern struct dentry
* __d_lookup(struct dentry
*, struct qstr
*);
276 /* validate "insecure" dentry pointer */
277 extern int d_validate(struct dentry
*, struct dentry
*);
279 extern char * d_path(struct dentry
*, struct vfsmount
*, char *, int);
281 /* Allocation counts.. */
284 * dget, dget_locked - get a reference to a dentry
285 * @dentry: dentry to get a reference to
287 * Given a dentry or %NULL pointer increment the reference count
288 * if appropriate and return the dentry. A dentry will not be
289 * destroyed when it has references. dget() should never be
290 * called for dentries with zero reference counter. For these cases
291 * (preferably none, functions in dcache.c are sufficient for normal
292 * needs and they take necessary precautions) you should hold dcache_lock
293 * and call dget_locked() instead of dget().
296 static inline struct dentry
*dget(struct dentry
*dentry
)
299 BUG_ON(!atomic_read(&dentry
->d_count
));
300 atomic_inc(&dentry
->d_count
);
305 extern struct dentry
* dget_locked(struct dentry
*);
308 * d_unhashed - is dentry hashed
309 * @dentry: entry to check
311 * Returns true if the dentry passed is not currently hashed.
314 static inline int d_unhashed(struct dentry
*dentry
)
316 return (dentry
->d_flags
& DCACHE_UNHASHED
);
319 static inline struct dentry
*dget_parent(struct dentry
*dentry
)
323 spin_lock(&dentry
->d_lock
);
324 ret
= dget(dentry
->d_parent
);
325 spin_unlock(&dentry
->d_lock
);
329 extern void dput(struct dentry
*);
331 static inline int d_mountpoint(struct dentry
*dentry
)
333 return dentry
->d_mounted
;
336 extern struct vfsmount
*lookup_mnt(struct vfsmount
*, struct dentry
*);
337 extern struct vfsmount
*__lookup_mnt(struct vfsmount
*, struct dentry
*, int);
338 extern struct dentry
*lookup_create(struct nameidata
*nd
, int is_dir
);
340 extern int sysctl_vfs_cache_pressure
;
342 #endif /* __KERNEL__ */
344 #endif /* __LINUX_DCACHE_H */