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 */
90 unsigned int d_count; /* protected by d_lock */
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)(const struct dentry *, const struct inode *,
138 int (*d_compare)(const struct dentry *, const struct inode *,
139 const struct dentry *, const struct inode *,
140 unsigned int, const char *, const struct qstr *);
141 int (*d_delete)(const struct dentry *);
142 void (*d_release)(struct dentry *);
143 void (*d_iput)(struct dentry *, struct inode *);
144 char *(*d_dname)(struct dentry *, char *, int);
148 * Locking rules for dentry_operations callbacks are to be found in
149 * Documentation/filesystems/Locking. Keep it updated!
151 * FUrther descriptions are found in Documentation/filesystems/vfs.txt.
152 * Keep it updated too!
155 /* d_flags entries */
156 #define DCACHE_AUTOFS_PENDING 0x0001 /* autofs: "under construction" */
157 #define DCACHE_NFSFS_RENAMED 0x0002 /* this dentry has been "silly
158 * renamed" and has to be
159 * deleted on the last dput()
161 #define DCACHE_DISCONNECTED 0x0004
162 /* This dentry is possibly not currently connected to the dcache tree,
163 * in which case its parent will either be itself, or will have this
164 * flag as well. nfsd will not use a dentry with this bit set, but will
165 * first endeavour to clear the bit either by discovering that it is
166 * connected, or by performing lookup operations. Any filesystem which
167 * supports nfsd_operations MUST have a lookup function which, if it finds
168 * a directory inode with a DCACHE_DISCONNECTED dentry, will d_move
169 * that dentry into place and return that dentry rather than the passed one,
170 * typically using d_splice_alias.
173 #define DCACHE_REFERENCED 0x0008 /* Recently used, don't discard. */
174 #define DCACHE_UNHASHED 0x0010
176 #define DCACHE_INOTIFY_PARENT_WATCHED 0x0020 /* Parent inode is watched by inotify */
178 #define DCACHE_COOKIE 0x0040 /* For use by dcookie subsystem */
180 #define DCACHE_FSNOTIFY_PARENT_WATCHED 0x0080 /* Parent inode is watched by some fsnotify listener */
182 #define DCACHE_CANT_MOUNT 0x0100
184 extern spinlock_t dcache_lock;
185 extern seqlock_t rename_lock;
187 static inline int dname_external(struct dentry *dentry)
189 return dentry->d_name.name != dentry->d_iname;
193 * These are the low-level FS interfaces to the dcache..
195 extern void d_instantiate(struct dentry *, struct inode *);
196 extern struct dentry * d_instantiate_unique(struct dentry *, struct inode *);
197 extern struct dentry * d_materialise_unique(struct dentry *, struct inode *);
198 extern void __d_drop(struct dentry *dentry);
199 extern void d_drop(struct dentry *dentry);
200 extern void d_delete(struct dentry *);
202 /* allocate/de-allocate */
203 extern struct dentry * d_alloc(struct dentry *, const struct qstr *);
204 extern struct dentry * d_splice_alias(struct inode *, struct dentry *);
205 extern struct dentry * d_add_ci(struct dentry *, struct inode *, struct qstr *);
206 extern struct dentry * d_obtain_alias(struct inode *);
207 extern void shrink_dcache_sb(struct super_block *);
208 extern void shrink_dcache_parent(struct dentry *);
209 extern void shrink_dcache_for_umount(struct super_block *);
210 extern int d_invalidate(struct dentry *);
212 /* only used at mount-time */
213 extern struct dentry * d_alloc_root(struct inode *);
215 /* <clickety>-<click> the ramfs-type tree */
216 extern void d_genocide(struct dentry *);
218 extern struct dentry *d_find_alias(struct inode *);
219 extern void d_prune_aliases(struct inode *);
221 /* test whether we have any submounts in a subdir tree */
222 extern int have_submounts(struct dentry *);
225 * This adds the entry to the hash queues.
227 extern void d_rehash(struct dentry *);
230 * d_add - add dentry to hash queues
231 * @entry: dentry to add
232 * @inode: The inode to attach to this dentry
234 * This adds the entry to the hash queues and initializes @inode.
235 * The entry was actually filled in earlier during d_alloc().
238 static inline void d_add(struct dentry *entry, struct inode *inode)
240 d_instantiate(entry, inode);
245 * d_add_unique - add dentry to hash queues without aliasing
246 * @entry: dentry to add
247 * @inode: The inode to attach to this dentry
249 * This adds the entry to the hash queues and initializes @inode.
250 * The entry was actually filled in earlier during d_alloc().
252 static inline struct dentry *d_add_unique(struct dentry *entry, struct inode *inode)
256 res = d_instantiate_unique(entry, inode);
257 d_rehash(res != NULL ? res : entry);
261 extern void dentry_update_name_case(struct dentry *, struct qstr *);
263 /* used for rename() and baskets */
264 extern void d_move(struct dentry *, struct dentry *);
265 extern struct dentry *d_ancestor(struct dentry *, struct dentry *);
267 /* appendix may either be NULL or be used for transname suffixes */
268 extern struct dentry * d_lookup(struct dentry *, struct qstr *);
269 extern struct dentry * __d_lookup(struct dentry *, struct qstr *);
270 extern struct dentry * d_hash_and_lookup(struct dentry *, struct qstr *);
272 /* validate "insecure" dentry pointer */
273 extern int d_validate(struct dentry *, struct dentry *);
276 * helper function for dentry_operations.d_dname() members
278 extern char *dynamic_dname(struct dentry *, char *, int, const char *, ...);
280 extern char *__d_path(const struct path *path, struct path *root, char *, int);
281 extern char *d_path(const struct path *, char *, int);
282 extern char *d_path_with_unreachable(const struct path *, char *, int);
283 extern char *dentry_path_raw(struct dentry *, char *, int);
284 extern char *dentry_path(struct dentry *, char *, int);
286 /* Allocation counts.. */
289 * dget, dget_locked - get a reference to a dentry
290 * @dentry: dentry to get a reference to
292 * Given a dentry or %NULL pointer increment the reference count
293 * if appropriate and return the dentry. A dentry will not be
294 * destroyed when it has references. dget() should never be
295 * called for dentries with zero reference counter. For these cases
296 * (preferably none, functions in dcache.c are sufficient for normal
297 * needs and they take necessary precautions) you should hold dcache_lock
298 * and call dget_locked() instead of dget().
300 static inline struct dentry *dget_dlock(struct dentry *dentry)
303 BUG_ON(!dentry->d_count);
309 static inline struct dentry *dget(struct dentry *dentry)
312 spin_lock(&dentry->d_lock);
314 spin_unlock(&dentry->d_lock);
319 extern struct dentry * dget_locked(struct dentry *);
320 extern struct dentry * dget_locked_dlock(struct dentry *);
322 extern struct dentry *dget_parent(struct dentry *dentry);
325 * d_unhashed - is dentry hashed
326 * @dentry: entry to check
328 * Returns true if the dentry passed is not currently hashed.
331 static inline int d_unhashed(struct dentry *dentry)
333 return (dentry->d_flags & DCACHE_UNHASHED);
336 static inline int d_unlinked(struct dentry *dentry)
338 return d_unhashed(dentry) && !IS_ROOT(dentry);
341 static inline int cant_mount(struct dentry *dentry)
343 return (dentry->d_flags & DCACHE_CANT_MOUNT);
346 static inline void dont_mount(struct dentry *dentry)
348 spin_lock(&dentry->d_lock);
349 dentry->d_flags |= DCACHE_CANT_MOUNT;
350 spin_unlock(&dentry->d_lock);
353 extern void dput(struct dentry *);
355 static inline int d_mountpoint(struct dentry *dentry)
357 return dentry->d_mounted;
360 extern struct vfsmount *lookup_mnt(struct path *);
361 extern struct dentry *lookup_create(struct nameidata *nd, int is_dir);
363 extern int sysctl_vfs_cache_pressure;
365 #endif /* __LINUX_DCACHE_H */