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;
82 /* Total dentry size=256 bytes */
83 #define DNAME_INLINE_LEN_MIN 60
85 /* Total dentry size=128 bytes */
86 #define DNAME_INLINE_LEN_MIN 16
91 unsigned int d_flags; /* protected by d_lock */
92 spinlock_t d_lock; /* per dentry lock */
93 struct inode *d_inode; /* Where the name belongs to - NULL is
96 * The next three fields are touched by __d_lookup. Place them here
97 * so they all fit in a 16-byte range, with 16-byte alignment.
99 struct dentry *d_parent; /* parent directory */
102 struct list_head d_lru; /* LRU list */
103 struct list_head d_child; /* child of parent list */
104 struct list_head d_subdirs; /* our children */
105 struct list_head d_alias; /* inode alias list */
106 unsigned long d_time; /* used by d_revalidate */
107 struct dentry_operations *d_op;
108 struct super_block *d_sb; /* The root of the dentry tree */
109 void *d_fsdata; /* fs-specific data */
110 void * d_extra_attributes; /* TUX-specific data */
111 struct rcu_head d_rcu;
112 struct dcookie_struct *d_cookie; /* cookie, if any */
113 struct hlist_node d_hash; /* lookup hash list */
115 unsigned char d_iname[DNAME_INLINE_LEN_MIN]; /* small names */
118 struct dentry_operations {
119 int (*d_revalidate)(struct dentry *, struct nameidata *);
120 int (*d_hash) (struct dentry *, struct qstr *);
121 int (*d_compare) (struct dentry *, struct qstr *, struct qstr *);
122 int (*d_delete)(struct dentry *);
123 void (*d_release)(struct dentry *);
124 void (*d_iput)(struct dentry *, struct inode *);
127 /* the dentry parameter passed to d_hash and d_compare is the parent
128 * directory of the entries to be compared. It is used in case these
129 * functions need any directory specific information for determining
130 * equivalency classes. Using the dentry itself might not work, as it
131 * might be a negative dentry which has no information associated with
136 big lock dcache_lock d_lock may block
137 d_revalidate: no no no yes
139 d_compare: no yes yes no
140 d_delete: no yes no no
141 d_release: no no no yes
145 /* d_flags entries */
146 #define DCACHE_AUTOFS_PENDING 0x0001 /* autofs: "under construction" */
147 #define DCACHE_NFSFS_RENAMED 0x0002 /* this dentry has been "silly
148 * renamed" and has to be
149 * deleted on the last dput()
151 #define DCACHE_DISCONNECTED 0x0004
152 /* This dentry is possibly not currently connected to the dcache tree,
153 * in which case its parent will either be itself, or will have this
154 * flag as well. nfsd will not use a dentry with this bit set, but will
155 * first endeavour to clear the bit either by discovering that it is
156 * connected, or by performing lookup operations. Any filesystem which
157 * supports nfsd_operations MUST have a lookup function which, if it finds
158 * a directory inode with a DCACHE_DISCONNECTED dentry, will d_move
159 * that dentry into place and return that dentry rather than the passed one,
160 * typically using d_splice_alias.
163 #define DCACHE_REFERENCED 0x0008 /* Recently used, don't discard. */
164 #define DCACHE_UNHASHED 0x0010
166 extern spinlock_t dcache_lock;
169 * d_drop - drop a dentry
170 * @dentry: dentry to drop
172 * d_drop() unhashes the entry from the parent dentry hashes, so that it won't
173 * be found through a VFS lookup any more. Note that this is different from
174 * deleting the dentry - d_delete will try to mark the dentry negative if
175 * possible, giving a successful _negative_ lookup, while d_drop will
176 * just make the cache lookup fail.
178 * d_drop() is used mainly for stuff that wants to invalidate a dentry for some
179 * reason (NFS timeouts or autofs deletes).
181 * __d_drop requires dentry->d_lock.
184 static inline void __d_drop(struct dentry *dentry)
186 if (!(dentry->d_flags & DCACHE_UNHASHED)) {
187 dentry->d_flags |= DCACHE_UNHASHED;
188 hlist_del_rcu(&dentry->d_hash);
192 static inline void d_drop(struct dentry *dentry)
194 spin_lock(&dcache_lock);
195 spin_lock(&dentry->d_lock);
197 spin_unlock(&dentry->d_lock);
198 spin_unlock(&dcache_lock);
201 static inline int dname_external(struct dentry *dentry)
203 return dentry->d_name.name != dentry->d_iname;
207 * These are the low-level FS interfaces to the dcache..
209 extern void d_instantiate(struct dentry *, struct inode *);
210 extern struct dentry * d_instantiate_unique(struct dentry *, struct inode *);
211 extern void d_delete(struct dentry *);
213 /* allocate/de-allocate */
214 extern struct dentry * d_alloc(struct dentry *, const struct qstr *);
215 extern struct dentry * d_alloc_anon(struct inode *);
216 extern struct dentry * d_splice_alias(struct inode *, struct dentry *);
217 extern void shrink_dcache_sb(struct super_block *);
218 extern void shrink_dcache_parent(struct dentry *);
219 extern void shrink_dcache_anon(struct hlist_head *);
220 extern int d_invalidate(struct dentry *);
221 extern void flush_dentry_attributes(void);
223 /* only used at mount-time */
224 extern struct dentry * d_alloc_root(struct inode *);
226 /* <clickety>-<click> the ramfs-type tree */
227 extern void d_genocide(struct dentry *);
229 extern struct dentry *d_find_alias(struct inode *);
230 extern void d_prune_aliases(struct inode *);
232 /* test whether we have any submounts in a subdir tree */
233 extern int have_submounts(struct dentry *);
236 * This adds the entry to the hash queues.
238 extern void d_rehash(struct dentry *);
241 * d_add - add dentry to hash queues
242 * @entry: dentry to add
243 * @inode: The inode to attach to this dentry
245 * This adds the entry to the hash queues and initializes @inode.
246 * The entry was actually filled in earlier during d_alloc().
249 static inline void d_add(struct dentry *entry, struct inode *inode)
251 d_instantiate(entry, inode);
256 * d_add_unique - add dentry to hash queues without aliasing
257 * @entry: dentry to add
258 * @inode: The inode to attach to this dentry
260 * This adds the entry to the hash queues and initializes @inode.
261 * The entry was actually filled in earlier during d_alloc().
263 static inline struct dentry *d_add_unique(struct dentry *entry, struct inode *inode)
267 res = d_instantiate_unique(entry, inode);
268 d_rehash(res != NULL ? res : entry);
272 /* used for rename() and baskets */
273 extern void d_move(struct dentry *, struct dentry *);
275 /* appendix may either be NULL or be used for transname suffixes */
276 extern struct dentry * d_lookup(struct dentry *, struct qstr *);
277 extern struct dentry * __d_lookup(struct dentry *, struct qstr *);
279 /* validate "insecure" dentry pointer */
280 extern int d_validate(struct dentry *, struct dentry *);
282 char * __d_path( struct dentry *dentry, struct vfsmount *vfsmnt,
283 struct dentry *root, struct vfsmount *rootmnt,
284 char *buffer, int buflen);
286 extern char * d_path(struct dentry *, struct vfsmount *, char *, int);
288 /* Allocation counts.. */
291 * dget, dget_locked - get a reference to a dentry
292 * @dentry: dentry to get a reference to
294 * Given a dentry or %NULL pointer increment the reference count
295 * if appropriate and return the dentry. A dentry will not be
296 * destroyed when it has references. dget() should never be
297 * called for dentries with zero reference counter. For these cases
298 * (preferably none, functions in dcache.c are sufficient for normal
299 * needs and they take necessary precautions) you should hold dcache_lock
300 * and call dget_locked() instead of dget().
303 static inline struct dentry *dget(struct dentry *dentry)
306 BUG_ON(!atomic_read(&dentry->d_count));
307 atomic_inc(&dentry->d_count);
312 extern struct dentry * dget_locked(struct dentry *);
315 * d_unhashed - is dentry hashed
316 * @dentry: entry to check
318 * Returns true if the dentry passed is not currently hashed.
321 static inline int d_unhashed(struct dentry *dentry)
323 return (dentry->d_flags & DCACHE_UNHASHED);
326 static inline struct dentry *dget_parent(struct dentry *dentry)
330 spin_lock(&dentry->d_lock);
331 ret = dget(dentry->d_parent);
332 spin_unlock(&dentry->d_lock);
336 extern void dput(struct dentry *);
338 static inline int d_mountpoint(struct dentry *dentry)
340 return dentry->d_mounted;
343 extern struct vfsmount *lookup_mnt(struct vfsmount *, struct dentry *);
344 extern struct dentry *lookup_create(struct nameidata *nd, int is_dir);
346 extern int sysctl_vfs_cache_pressure;
348 #endif /* __KERNEL__ */
350 #endif /* __LINUX_DCACHE_H */