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/rculist_bl.h>
8 #include <linux/spinlock.h>
9 #include <linux/seqlock.h>
10 #include <linux/cache.h>
11 #include <linux/rcupdate.h>
18 * linux/include/linux/dcache.h
20 * Dirent cache data structures
22 * (C) Copyright 1997 Thomas Schoebel-Theuer,
23 * with heavy changes by Linus Torvalds
26 #define IS_ROOT(x) ((x) == (x)->d_parent)
29 * "quick string" -- eases parameter passing, but more importantly
30 * saves "metadata" about the string (ie length and the hash).
32 * hash comes first so it snuggles against d_parent in the
38 const unsigned char *name;
41 struct dentry_stat_t {
44 int age_limit; /* age in seconds */
45 int want_pages; /* pages requested by system */
48 extern struct dentry_stat_t dentry_stat;
51 * Compare 2 name strings, return 0 if they match, otherwise non-zero.
52 * The strings are both count bytes long, and count is non-zero.
54 static inline int dentry_cmp(const unsigned char *cs, size_t scount,
55 const unsigned char *ct, size_t tcount)
71 /* Name hashing routines. Initial hash value */
72 /* Hash courtesy of the R5 hash in reiserfs modulo sign bits */
73 #define init_name_hash() 0
75 /* partial hash update function. Assume roughly 4 bits per character */
76 static inline unsigned long
77 partial_name_hash(unsigned long c, unsigned long prevhash)
79 return (prevhash + (c << 4) + (c >> 4)) * 11;
83 * Finally: cut down the number of bits to a int value (and try to avoid
86 static inline unsigned long end_name_hash(unsigned long hash)
88 return (unsigned int) hash;
91 /* Compute the hash for a name string. */
92 static inline unsigned int
93 full_name_hash(const unsigned char *name, unsigned int len)
95 unsigned long hash = init_name_hash();
97 hash = partial_name_hash(*name++, hash);
98 return end_name_hash(hash);
102 * Try to keep struct dentry aligned on 64 byte cachelines (this will
103 * give reasonable cacheline footprint with larger lines without the
104 * large memory footprint increase).
107 # define DNAME_INLINE_LEN 32 /* 192 bytes */
110 # define DNAME_INLINE_LEN 36 /* 128 bytes */
112 # define DNAME_INLINE_LEN 40 /* 128 bytes */
117 /* RCU lookup touched fields */
118 unsigned int d_flags; /* protected by d_lock */
119 seqcount_t d_seq; /* per dentry seqlock */
120 struct hlist_bl_node d_hash; /* lookup hash list */
121 struct dentry *d_parent; /* parent directory */
123 struct inode *d_inode; /* Where the name belongs to - NULL is
125 unsigned char d_iname[DNAME_INLINE_LEN]; /* small names */
127 /* Ref lookup also touches following */
128 unsigned int d_count; /* protected by d_lock */
129 spinlock_t d_lock; /* per dentry lock */
130 const struct dentry_operations *d_op;
131 struct super_block *d_sb; /* The root of the dentry tree */
132 unsigned long d_time; /* used by d_revalidate */
133 void *d_fsdata; /* fs-specific data */
135 struct list_head d_lru; /* LRU list */
137 * d_child and d_rcu can share memory
140 struct list_head d_child; /* child of parent list */
141 struct rcu_head d_rcu;
143 struct list_head d_subdirs; /* our children */
144 struct list_head d_alias; /* inode alias list */
148 * dentry->d_lock spinlock nesting subclasses:
153 enum dentry_d_lock_class
155 DENTRY_D_LOCK_NORMAL, /* implicitly used by plain spin_lock() APIs. */
159 struct dentry_operations {
160 int (*d_revalidate)(struct dentry *, struct nameidata *);
161 int (*d_hash)(const struct dentry *, const struct inode *,
163 int (*d_compare)(const struct dentry *, const struct inode *,
164 const struct dentry *, const struct inode *,
165 unsigned int, const char *, const struct qstr *);
166 int (*d_delete)(const struct dentry *);
167 void (*d_release)(struct dentry *);
168 void (*d_iput)(struct dentry *, struct inode *);
169 char *(*d_dname)(struct dentry *, char *, int);
170 struct vfsmount *(*d_automount)(struct path *);
171 } ____cacheline_aligned;
174 * Locking rules for dentry_operations callbacks are to be found in
175 * Documentation/filesystems/Locking. Keep it updated!
177 * FUrther descriptions are found in Documentation/filesystems/vfs.txt.
178 * Keep it updated too!
181 /* d_flags entries */
182 #define DCACHE_AUTOFS_PENDING 0x0001 /* autofs: "under construction" */
183 #define DCACHE_NFSFS_RENAMED 0x0002
184 /* this dentry has been "silly renamed" and has to be deleted on the last
187 #define DCACHE_DISCONNECTED 0x0004
188 /* This dentry is possibly not currently connected to the dcache tree, in
189 * which case its parent will either be itself, or will have this flag as
190 * well. nfsd will not use a dentry with this bit set, but will first
191 * endeavour to clear the bit either by discovering that it is connected,
192 * or by performing lookup operations. Any filesystem which supports
193 * nfsd_operations MUST have a lookup function which, if it finds a
194 * directory inode with a DCACHE_DISCONNECTED dentry, will d_move that
195 * dentry into place and return that dentry rather than the passed one,
196 * typically using d_splice_alias. */
198 #define DCACHE_REFERENCED 0x0008 /* Recently used, don't discard. */
199 #define DCACHE_UNHASHED 0x0010
200 #define DCACHE_INOTIFY_PARENT_WATCHED 0x0020
201 /* Parent inode is watched by inotify */
203 #define DCACHE_COOKIE 0x0040 /* For use by dcookie subsystem */
204 #define DCACHE_FSNOTIFY_PARENT_WATCHED 0x0080
205 /* Parent inode is watched by some fsnotify listener */
207 #define DCACHE_CANT_MOUNT 0x0100
208 #define DCACHE_GENOCIDE 0x0200
210 #define DCACHE_OP_HASH 0x1000
211 #define DCACHE_OP_COMPARE 0x2000
212 #define DCACHE_OP_REVALIDATE 0x4000
213 #define DCACHE_OP_DELETE 0x8000
215 #define DCACHE_MOUNTED 0x10000 /* is a mountpoint */
216 #define DCACHE_NEED_AUTOMOUNT 0x20000 /* handle automount on this dir */
217 #define DCACHE_MANAGED_DENTRY \
218 (DCACHE_MOUNTED|DCACHE_NEED_AUTOMOUNT)
220 extern seqlock_t rename_lock;
222 static inline int dname_external(struct dentry *dentry)
224 return dentry->d_name.name != dentry->d_iname;
228 * These are the low-level FS interfaces to the dcache..
230 extern void d_instantiate(struct dentry *, struct inode *);
231 extern struct dentry * d_instantiate_unique(struct dentry *, struct inode *);
232 extern struct dentry * d_materialise_unique(struct dentry *, struct inode *);
233 extern void __d_drop(struct dentry *dentry);
234 extern void d_drop(struct dentry *dentry);
235 extern void d_delete(struct dentry *);
236 extern void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op);
238 /* allocate/de-allocate */
239 extern struct dentry * d_alloc(struct dentry *, const struct qstr *);
240 extern struct dentry * d_alloc_pseudo(struct super_block *, const struct qstr *);
241 extern struct dentry * d_splice_alias(struct inode *, struct dentry *);
242 extern struct dentry * d_add_ci(struct dentry *, struct inode *, struct qstr *);
243 extern struct dentry * d_obtain_alias(struct inode *);
244 extern void shrink_dcache_sb(struct super_block *);
245 extern void shrink_dcache_parent(struct dentry *);
246 extern void shrink_dcache_for_umount(struct super_block *);
247 extern int d_invalidate(struct dentry *);
249 /* only used at mount-time */
250 extern struct dentry * d_alloc_root(struct inode *);
252 /* <clickety>-<click> the ramfs-type tree */
253 extern void d_genocide(struct dentry *);
255 extern struct dentry *d_find_alias(struct inode *);
256 extern void d_prune_aliases(struct inode *);
258 /* test whether we have any submounts in a subdir tree */
259 extern int have_submounts(struct dentry *);
262 * This adds the entry to the hash queues.
264 extern void d_rehash(struct dentry *);
267 * d_add - add dentry to hash queues
268 * @entry: dentry to add
269 * @inode: The inode to attach to this dentry
271 * This adds the entry to the hash queues and initializes @inode.
272 * The entry was actually filled in earlier during d_alloc().
275 static inline void d_add(struct dentry *entry, struct inode *inode)
277 d_instantiate(entry, inode);
282 * d_add_unique - add dentry to hash queues without aliasing
283 * @entry: dentry to add
284 * @inode: The inode to attach to this dentry
286 * This adds the entry to the hash queues and initializes @inode.
287 * The entry was actually filled in earlier during d_alloc().
289 static inline struct dentry *d_add_unique(struct dentry *entry, struct inode *inode)
293 res = d_instantiate_unique(entry, inode);
294 d_rehash(res != NULL ? res : entry);
298 extern void dentry_update_name_case(struct dentry *, struct qstr *);
300 /* used for rename() and baskets */
301 extern void d_move(struct dentry *, struct dentry *);
302 extern struct dentry *d_ancestor(struct dentry *, struct dentry *);
304 /* appendix may either be NULL or be used for transname suffixes */
305 extern struct dentry *d_lookup(struct dentry *, struct qstr *);
306 extern struct dentry *d_hash_and_lookup(struct dentry *, struct qstr *);
307 extern struct dentry *__d_lookup(struct dentry *, struct qstr *);
308 extern struct dentry *__d_lookup_rcu(struct dentry *parent, struct qstr *name,
309 unsigned *seq, struct inode **inode);
312 * __d_rcu_to_refcount - take a refcount on dentry if sequence check is ok
313 * @dentry: dentry to take a ref on
314 * @seq: seqcount to verify against
315 * Returns: 0 on failure, else 1.
317 * __d_rcu_to_refcount operates on a dentry,seq pair that was returned
318 * by __d_lookup_rcu, to get a reference on an rcu-walk dentry.
320 static inline int __d_rcu_to_refcount(struct dentry *dentry, unsigned seq)
324 assert_spin_locked(&dentry->d_lock);
325 if (!read_seqcount_retry(&dentry->d_seq, seq)) {
333 /* validate "insecure" dentry pointer */
334 extern int d_validate(struct dentry *, struct dentry *);
337 * helper function for dentry_operations.d_dname() members
339 extern char *dynamic_dname(struct dentry *, char *, int, const char *, ...);
341 extern char *__d_path(const struct path *path, struct path *root, char *, int);
342 extern char *d_path(const struct path *, char *, int);
343 extern char *d_path_with_unreachable(const struct path *, char *, int);
344 extern char *dentry_path_raw(struct dentry *, char *, int);
345 extern char *dentry_path(struct dentry *, char *, int);
347 /* Allocation counts.. */
350 * dget, dget_dlock - get a reference to a dentry
351 * @dentry: dentry to get a reference to
353 * Given a dentry or %NULL pointer increment the reference count
354 * if appropriate and return the dentry. A dentry will not be
355 * destroyed when it has references.
357 static inline struct dentry *dget_dlock(struct dentry *dentry)
364 static inline struct dentry *dget(struct dentry *dentry)
367 spin_lock(&dentry->d_lock);
369 spin_unlock(&dentry->d_lock);
374 extern struct dentry *dget_parent(struct dentry *dentry);
377 * d_unhashed - is dentry hashed
378 * @dentry: entry to check
380 * Returns true if the dentry passed is not currently hashed.
383 static inline int d_unhashed(struct dentry *dentry)
385 return (dentry->d_flags & DCACHE_UNHASHED);
388 static inline int d_unlinked(struct dentry *dentry)
390 return d_unhashed(dentry) && !IS_ROOT(dentry);
393 static inline int cant_mount(struct dentry *dentry)
395 return (dentry->d_flags & DCACHE_CANT_MOUNT);
398 static inline void dont_mount(struct dentry *dentry)
400 spin_lock(&dentry->d_lock);
401 dentry->d_flags |= DCACHE_CANT_MOUNT;
402 spin_unlock(&dentry->d_lock);
405 extern void dput(struct dentry *);
407 static inline int d_mountpoint(struct dentry *dentry)
409 return dentry->d_flags & DCACHE_MOUNTED;
412 extern struct vfsmount *lookup_mnt(struct path *);
413 extern struct dentry *lookup_create(struct nameidata *nd, int is_dir);
415 extern int sysctl_vfs_cache_pressure;
417 #endif /* __LINUX_DCACHE_H */