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;
50 /* Name hashing routines. Initial hash value */
51 /* Hash courtesy of the R5 hash in reiserfs modulo sign bits */
52 #define init_name_hash() 0
54 /* partial hash update function. Assume roughly 4 bits per character */
55 static inline unsigned long
56 partial_name_hash(unsigned long c, unsigned long prevhash)
58 return (prevhash + (c << 4) + (c >> 4)) * 11;
62 * Finally: cut down the number of bits to a int value (and try to avoid
65 static inline unsigned long end_name_hash(unsigned long hash)
67 return (unsigned int) hash;
70 /* Compute the hash for a name string. */
71 static inline unsigned int
72 full_name_hash(const unsigned char *name, unsigned int len)
74 unsigned long hash = init_name_hash();
76 hash = partial_name_hash(*name++, hash);
77 return end_name_hash(hash);
81 * Try to keep struct dentry aligned on 64 byte cachelines (this will
82 * give reasonable cacheline footprint with larger lines without the
83 * large memory footprint increase).
86 # define DNAME_INLINE_LEN 32 /* 192 bytes */
89 # define DNAME_INLINE_LEN 36 /* 128 bytes */
91 # define DNAME_INLINE_LEN 40 /* 128 bytes */
96 /* RCU lookup touched fields */
97 unsigned int d_flags; /* protected by d_lock */
98 seqcount_t d_seq; /* per dentry seqlock */
99 struct hlist_bl_node d_hash; /* lookup hash list */
100 struct dentry *d_parent; /* parent directory */
102 struct inode *d_inode; /* Where the name belongs to - NULL is
104 unsigned char d_iname[DNAME_INLINE_LEN]; /* small names */
106 /* Ref lookup also touches following */
107 unsigned int d_count; /* protected by d_lock */
108 spinlock_t d_lock; /* per dentry lock */
109 const struct dentry_operations *d_op;
110 struct super_block *d_sb; /* The root of the dentry tree */
111 unsigned long d_time; /* used by d_revalidate */
112 void *d_fsdata; /* fs-specific data */
114 struct list_head d_lru; /* LRU list */
116 * d_child and d_rcu can share memory
119 struct list_head d_child; /* child of parent list */
120 struct rcu_head d_rcu;
122 struct list_head d_subdirs; /* our children */
123 struct list_head d_alias; /* inode alias list */
127 * dentry->d_lock spinlock nesting subclasses:
132 enum dentry_d_lock_class
134 DENTRY_D_LOCK_NORMAL, /* implicitly used by plain spin_lock() APIs. */
138 struct dentry_operations {
139 int (*d_revalidate)(struct dentry *, struct nameidata *);
140 int (*d_hash)(const struct dentry *, const struct inode *,
142 int (*d_compare)(const struct dentry *, const struct inode *,
143 const struct dentry *, const struct inode *,
144 unsigned int, const char *, const struct qstr *);
145 int (*d_delete)(const struct dentry *);
146 void (*d_release)(struct dentry *);
147 void (*d_iput)(struct dentry *, struct inode *);
148 char *(*d_dname)(struct dentry *, char *, int);
149 } ____cacheline_aligned;
152 * Locking rules for dentry_operations callbacks are to be found in
153 * Documentation/filesystems/Locking. Keep it updated!
155 * FUrther descriptions are found in Documentation/filesystems/vfs.txt.
156 * Keep it updated too!
159 /* d_flags entries */
160 #define DCACHE_AUTOFS_PENDING 0x0001 /* autofs: "under construction" */
161 #define DCACHE_NFSFS_RENAMED 0x0002
162 /* this dentry has been "silly renamed" and has to be deleted on the last
165 #define DCACHE_DISCONNECTED 0x0004
166 /* This dentry is possibly not currently connected to the dcache tree, in
167 * which case its parent will either be itself, or will have this flag as
168 * well. nfsd will not use a dentry with this bit set, but will first
169 * endeavour to clear the bit either by discovering that it is connected,
170 * or by performing lookup operations. Any filesystem which supports
171 * nfsd_operations MUST have a lookup function which, if it finds a
172 * directory inode with a DCACHE_DISCONNECTED dentry, will d_move that
173 * dentry into place and return that dentry rather than the passed one,
174 * typically using d_splice_alias. */
176 #define DCACHE_REFERENCED 0x0008 /* Recently used, don't discard. */
177 #define DCACHE_UNHASHED 0x0010
178 #define DCACHE_INOTIFY_PARENT_WATCHED 0x0020
179 /* Parent inode is watched by inotify */
181 #define DCACHE_COOKIE 0x0040 /* For use by dcookie subsystem */
182 #define DCACHE_FSNOTIFY_PARENT_WATCHED 0x0080
183 /* Parent inode is watched by some fsnotify listener */
185 #define DCACHE_CANT_MOUNT 0x0100
186 #define DCACHE_GENOCIDE 0x0200
187 #define DCACHE_MOUNTED 0x0400 /* is a mountpoint */
189 #define DCACHE_OP_HASH 0x1000
190 #define DCACHE_OP_COMPARE 0x2000
191 #define DCACHE_OP_REVALIDATE 0x4000
192 #define DCACHE_OP_DELETE 0x8000
194 extern spinlock_t dcache_inode_lock;
195 extern seqlock_t rename_lock;
197 static inline int dname_external(struct dentry *dentry)
199 return dentry->d_name.name != dentry->d_iname;
203 * These are the low-level FS interfaces to the dcache..
205 extern void d_instantiate(struct dentry *, struct inode *);
206 extern struct dentry * d_instantiate_unique(struct dentry *, struct inode *);
207 extern struct dentry * d_materialise_unique(struct dentry *, struct inode *);
208 extern void __d_drop(struct dentry *dentry);
209 extern void d_drop(struct dentry *dentry);
210 extern void d_delete(struct dentry *);
211 extern void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op);
213 /* allocate/de-allocate */
214 extern struct dentry * d_alloc(struct dentry *, const struct qstr *);
215 extern struct dentry * d_splice_alias(struct inode *, struct dentry *);
216 extern struct dentry * d_add_ci(struct dentry *, struct inode *, struct qstr *);
217 extern struct dentry * d_obtain_alias(struct inode *);
218 extern void shrink_dcache_sb(struct super_block *);
219 extern void shrink_dcache_parent(struct dentry *);
220 extern void shrink_dcache_for_umount(struct super_block *);
221 extern int d_invalidate(struct dentry *);
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 extern void dentry_update_name_case(struct dentry *, struct qstr *);
274 /* used for rename() and baskets */
275 extern void d_move(struct dentry *, struct dentry *);
276 extern struct dentry *d_ancestor(struct dentry *, struct dentry *);
278 /* appendix may either be NULL or be used for transname suffixes */
279 extern struct dentry *d_lookup(struct dentry *, struct qstr *);
280 extern struct dentry *d_hash_and_lookup(struct dentry *, struct qstr *);
281 extern struct dentry *__d_lookup(struct dentry *, struct qstr *);
282 extern struct dentry *__d_lookup_rcu(struct dentry *parent, struct qstr *name,
283 unsigned *seq, struct inode **inode);
286 * __d_rcu_to_refcount - take a refcount on dentry if sequence check is ok
287 * @dentry: dentry to take a ref on
288 * @seq: seqcount to verify against
289 * @Returns: 0 on failure, else 1.
291 * __d_rcu_to_refcount operates on a dentry,seq pair that was returned
292 * by __d_lookup_rcu, to get a reference on an rcu-walk dentry.
294 static inline int __d_rcu_to_refcount(struct dentry *dentry, unsigned seq)
298 assert_spin_locked(&dentry->d_lock);
299 if (!read_seqcount_retry(&dentry->d_seq, seq)) {
307 /* validate "insecure" dentry pointer */
308 extern int d_validate(struct dentry *, struct dentry *);
311 * helper function for dentry_operations.d_dname() members
313 extern char *dynamic_dname(struct dentry *, char *, int, const char *, ...);
315 extern char *__d_path(const struct path *path, struct path *root, char *, int);
316 extern char *d_path(const struct path *, char *, int);
317 extern char *d_path_with_unreachable(const struct path *, char *, int);
318 extern char *dentry_path_raw(struct dentry *, char *, int);
319 extern char *dentry_path(struct dentry *, char *, int);
321 /* Allocation counts.. */
324 * dget, dget_dlock - get a reference to a dentry
325 * @dentry: dentry to get a reference to
327 * Given a dentry or %NULL pointer increment the reference count
328 * if appropriate and return the dentry. A dentry will not be
329 * destroyed when it has references.
331 static inline struct dentry *dget_dlock(struct dentry *dentry)
338 static inline struct dentry *dget(struct dentry *dentry)
341 spin_lock(&dentry->d_lock);
343 spin_unlock(&dentry->d_lock);
348 extern struct dentry *dget_parent(struct dentry *dentry);
351 * d_unhashed - is dentry hashed
352 * @dentry: entry to check
354 * Returns true if the dentry passed is not currently hashed.
357 static inline int d_unhashed(struct dentry *dentry)
359 return (dentry->d_flags & DCACHE_UNHASHED);
362 static inline int d_unlinked(struct dentry *dentry)
364 return d_unhashed(dentry) && !IS_ROOT(dentry);
367 static inline int cant_mount(struct dentry *dentry)
369 return (dentry->d_flags & DCACHE_CANT_MOUNT);
372 static inline void dont_mount(struct dentry *dentry)
374 spin_lock(&dentry->d_lock);
375 dentry->d_flags |= DCACHE_CANT_MOUNT;
376 spin_unlock(&dentry->d_lock);
379 extern void dput(struct dentry *);
381 static inline int d_mountpoint(struct dentry *dentry)
383 return dentry->d_flags & DCACHE_MOUNTED;
386 extern struct vfsmount *lookup_mnt(struct path *);
387 extern struct dentry *lookup_create(struct nameidata *nd, int is_dir);
389 extern int sysctl_vfs_cache_pressure;
391 #endif /* __LINUX_DCACHE_H */