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/seqlock.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);
80 * Try to keep struct dentry aligned on 64 byte cachelines (this will
81 * give reasonable cacheline footprint with larger lines without the
82 * large memory footprint increase).
85 #define DNAME_INLINE_LEN_MIN 32 /* 192 bytes */
87 #define DNAME_INLINE_LEN_MIN 40 /* 128 bytes */
91 unsigned int d_count; /* protected by d_lock */
92 unsigned int d_flags; /* protected by d_lock */
93 spinlock_t d_lock; /* per dentry lock */
94 seqcount_t d_seq; /* per dentry seqlock */
95 struct inode *d_inode; /* Where the name belongs to - NULL is
98 * The next three fields are touched by __d_lookup. Place them here
99 * so they all fit in a cache line.
101 struct hlist_node d_hash; /* lookup hash list */
102 struct dentry *d_parent; /* parent directory */
105 struct list_head d_lru; /* LRU list */
107 * d_child and d_rcu can share memory
110 struct list_head d_child; /* child of parent list */
111 struct rcu_head d_rcu;
113 struct list_head d_subdirs; /* our children */
114 struct list_head d_alias; /* inode alias list */
115 unsigned long d_time; /* used by d_revalidate */
116 const struct dentry_operations *d_op;
117 struct super_block *d_sb; /* The root of the dentry tree */
118 void *d_fsdata; /* fs-specific data */
120 unsigned char d_iname[DNAME_INLINE_LEN_MIN]; /* small names */
124 * dentry->d_lock spinlock nesting subclasses:
129 enum dentry_d_lock_class
131 DENTRY_D_LOCK_NORMAL, /* implicitly used by plain spin_lock() APIs. */
135 struct dentry_operations {
136 int (*d_revalidate)(struct dentry *, struct nameidata *);
137 int (*d_hash)(const struct dentry *, const struct inode *,
139 int (*d_compare)(const struct dentry *, const struct inode *,
140 const struct dentry *, const struct inode *,
141 unsigned int, const char *, const struct qstr *);
142 int (*d_delete)(const struct dentry *);
143 void (*d_release)(struct dentry *);
144 void (*d_iput)(struct dentry *, struct inode *);
145 char *(*d_dname)(struct dentry *, char *, int);
149 * Locking rules for dentry_operations callbacks are to be found in
150 * Documentation/filesystems/Locking. Keep it updated!
152 * FUrther descriptions are found in Documentation/filesystems/vfs.txt.
153 * Keep it updated too!
156 /* d_flags entries */
157 #define DCACHE_AUTOFS_PENDING 0x0001 /* autofs: "under construction" */
158 #define DCACHE_NFSFS_RENAMED 0x0002
159 /* this dentry has been "silly renamed" and has to be deleted on the last
162 #define DCACHE_DISCONNECTED 0x0004
163 /* This dentry is possibly not currently connected to the dcache tree, in
164 * which case its parent will either be itself, or will have this flag as
165 * well. nfsd will not use a dentry with this bit set, but will first
166 * endeavour to clear the bit either by discovering that it is connected,
167 * or by performing lookup operations. Any filesystem which supports
168 * nfsd_operations MUST have a lookup function which, if it finds a
169 * directory inode with a DCACHE_DISCONNECTED dentry, will d_move that
170 * dentry into place and return that dentry rather than the passed one,
171 * typically using d_splice_alias. */
173 #define DCACHE_REFERENCED 0x0008 /* Recently used, don't discard. */
174 #define DCACHE_UNHASHED 0x0010
175 #define DCACHE_INOTIFY_PARENT_WATCHED 0x0020
176 /* Parent inode is watched by inotify */
178 #define DCACHE_COOKIE 0x0040 /* For use by dcookie subsystem */
179 #define DCACHE_FSNOTIFY_PARENT_WATCHED 0x0080
180 /* Parent inode is watched by some fsnotify listener */
182 #define DCACHE_CANT_MOUNT 0x0100
183 #define DCACHE_GENOCIDE 0x0200
184 #define DCACHE_MOUNTED 0x0400 /* is a mountpoint */
186 #define DCACHE_OP_HASH 0x1000
187 #define DCACHE_OP_COMPARE 0x2000
188 #define DCACHE_OP_REVALIDATE 0x4000
189 #define DCACHE_OP_DELETE 0x8000
192 extern spinlock_t dcache_inode_lock;
193 extern seqlock_t rename_lock;
195 static inline int dname_external(struct dentry *dentry)
197 return dentry->d_name.name != dentry->d_iname;
201 * These are the low-level FS interfaces to the dcache..
203 extern void d_instantiate(struct dentry *, struct inode *);
204 extern struct dentry * d_instantiate_unique(struct dentry *, struct inode *);
205 extern struct dentry * d_materialise_unique(struct dentry *, struct inode *);
206 extern void __d_drop(struct dentry *dentry);
207 extern void d_drop(struct dentry *dentry);
208 extern void d_delete(struct dentry *);
209 extern void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op);
211 /* allocate/de-allocate */
212 extern struct dentry * d_alloc(struct dentry *, const struct qstr *);
213 extern struct dentry * d_splice_alias(struct inode *, struct dentry *);
214 extern struct dentry * d_add_ci(struct dentry *, struct inode *, struct qstr *);
215 extern struct dentry * d_obtain_alias(struct inode *);
216 extern void shrink_dcache_sb(struct super_block *);
217 extern void shrink_dcache_parent(struct dentry *);
218 extern void shrink_dcache_for_umount(struct super_block *);
219 extern int d_invalidate(struct dentry *);
221 /* only used at mount-time */
222 extern struct dentry * d_alloc_root(struct inode *);
224 /* <clickety>-<click> the ramfs-type tree */
225 extern void d_genocide(struct dentry *);
227 extern struct dentry *d_find_alias(struct inode *);
228 extern void d_prune_aliases(struct inode *);
230 /* test whether we have any submounts in a subdir tree */
231 extern int have_submounts(struct dentry *);
234 * This adds the entry to the hash queues.
236 extern void d_rehash(struct dentry *);
239 * d_add - add dentry to hash queues
240 * @entry: dentry to add
241 * @inode: The inode to attach to this dentry
243 * This adds the entry to the hash queues and initializes @inode.
244 * The entry was actually filled in earlier during d_alloc().
247 static inline void d_add(struct dentry *entry, struct inode *inode)
249 d_instantiate(entry, inode);
254 * d_add_unique - add dentry to hash queues without aliasing
255 * @entry: dentry to add
256 * @inode: The inode to attach to this dentry
258 * This adds the entry to the hash queues and initializes @inode.
259 * The entry was actually filled in earlier during d_alloc().
261 static inline struct dentry *d_add_unique(struct dentry *entry, struct inode *inode)
265 res = d_instantiate_unique(entry, inode);
266 d_rehash(res != NULL ? res : entry);
270 extern void dentry_update_name_case(struct dentry *, struct qstr *);
272 /* used for rename() and baskets */
273 extern void d_move(struct dentry *, struct dentry *);
274 extern struct dentry *d_ancestor(struct dentry *, struct dentry *);
276 /* appendix may either be NULL or be used for transname suffixes */
277 extern struct dentry *d_lookup(struct dentry *, struct qstr *);
278 extern struct dentry *d_hash_and_lookup(struct dentry *, struct qstr *);
279 extern struct dentry *__d_lookup(struct dentry *, struct qstr *);
280 extern struct dentry *__d_lookup_rcu(struct dentry *parent, struct qstr *name,
281 unsigned *seq, struct inode **inode);
284 * __d_rcu_to_refcount - take a refcount on dentry if sequence check is ok
285 * @dentry: dentry to take a ref on
286 * @seq: seqcount to verify against
287 * @Returns: 0 on failure, else 1.
289 * __d_rcu_to_refcount operates on a dentry,seq pair that was returned
290 * by __d_lookup_rcu, to get a reference on an rcu-walk dentry.
292 static inline int __d_rcu_to_refcount(struct dentry *dentry, unsigned seq)
296 assert_spin_locked(&dentry->d_lock);
297 if (!read_seqcount_retry(&dentry->d_seq, seq)) {
305 /* validate "insecure" dentry pointer */
306 extern int d_validate(struct dentry *, struct dentry *);
309 * helper function for dentry_operations.d_dname() members
311 extern char *dynamic_dname(struct dentry *, char *, int, const char *, ...);
313 extern char *__d_path(const struct path *path, struct path *root, char *, int);
314 extern char *d_path(const struct path *, char *, int);
315 extern char *d_path_with_unreachable(const struct path *, char *, int);
316 extern char *dentry_path_raw(struct dentry *, char *, int);
317 extern char *dentry_path(struct dentry *, char *, int);
319 /* Allocation counts.. */
322 * dget, dget_dlock - get a reference to a dentry
323 * @dentry: dentry to get a reference to
325 * Given a dentry or %NULL pointer increment the reference count
326 * if appropriate and return the dentry. A dentry will not be
327 * destroyed when it has references.
329 static inline struct dentry *dget_dlock(struct dentry *dentry)
336 static inline struct dentry *dget(struct dentry *dentry)
339 spin_lock(&dentry->d_lock);
341 spin_unlock(&dentry->d_lock);
346 extern struct dentry *dget_parent(struct dentry *dentry);
349 * d_unhashed - is dentry hashed
350 * @dentry: entry to check
352 * Returns true if the dentry passed is not currently hashed.
355 static inline int d_unhashed(struct dentry *dentry)
357 return (dentry->d_flags & DCACHE_UNHASHED);
360 static inline int d_unlinked(struct dentry *dentry)
362 return d_unhashed(dentry) && !IS_ROOT(dentry);
365 static inline int cant_mount(struct dentry *dentry)
367 return (dentry->d_flags & DCACHE_CANT_MOUNT);
370 static inline void dont_mount(struct dentry *dentry)
372 spin_lock(&dentry->d_lock);
373 dentry->d_flags |= DCACHE_CANT_MOUNT;
374 spin_unlock(&dentry->d_lock);
377 extern void dput(struct dentry *);
379 static inline int d_mountpoint(struct dentry *dentry)
381 return dentry->d_flags & DCACHE_MOUNTED;
384 extern struct vfsmount *lookup_mnt(struct path *);
385 extern struct dentry *lookup_create(struct nameidata *nd, int is_dir);
387 extern int sysctl_vfs_cache_pressure;
389 #endif /* __LINUX_DCACHE_H */