1 #ifndef __LINUX_DCACHE_H
2 #define __LINUX_DCACHE_H
4 #include <linux/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 int (*d_manage)(struct dentry *, bool);
172 } ____cacheline_aligned;
175 * Locking rules for dentry_operations callbacks are to be found in
176 * Documentation/filesystems/Locking. Keep it updated!
178 * FUrther descriptions are found in Documentation/filesystems/vfs.txt.
179 * Keep it updated too!
182 /* d_flags entries */
183 #define DCACHE_AUTOFS_PENDING 0x0001 /* autofs: "under construction" */
184 #define DCACHE_NFSFS_RENAMED 0x0002
185 /* this dentry has been "silly renamed" and has to be deleted on the last
188 #define DCACHE_DISCONNECTED 0x0004
189 /* This dentry is possibly not currently connected to the dcache tree, in
190 * which case its parent will either be itself, or will have this flag as
191 * well. nfsd will not use a dentry with this bit set, but will first
192 * endeavour to clear the bit either by discovering that it is connected,
193 * or by performing lookup operations. Any filesystem which supports
194 * nfsd_operations MUST have a lookup function which, if it finds a
195 * directory inode with a DCACHE_DISCONNECTED dentry, will d_move that
196 * dentry into place and return that dentry rather than the passed one,
197 * typically using d_splice_alias. */
199 #define DCACHE_REFERENCED 0x0008 /* Recently used, don't discard. */
200 #define DCACHE_RCUACCESS 0x0010 /* Entry has ever been RCU-visible */
201 #define DCACHE_INOTIFY_PARENT_WATCHED 0x0020
202 /* Parent inode is watched by inotify */
204 #define DCACHE_COOKIE 0x0040 /* For use by dcookie subsystem */
205 #define DCACHE_FSNOTIFY_PARENT_WATCHED 0x0080
206 /* Parent inode is watched by some fsnotify listener */
208 #define DCACHE_CANT_MOUNT 0x0100
209 #define DCACHE_GENOCIDE 0x0200
211 #define DCACHE_OP_HASH 0x1000
212 #define DCACHE_OP_COMPARE 0x2000
213 #define DCACHE_OP_REVALIDATE 0x4000
214 #define DCACHE_OP_DELETE 0x8000
216 #define DCACHE_MOUNTED 0x10000 /* is a mountpoint */
217 #define DCACHE_NEED_AUTOMOUNT 0x20000 /* handle automount on this dir */
218 #define DCACHE_MANAGE_TRANSIT 0x40000 /* manage transit from this dirent */
219 #define DCACHE_NEED_LOOKUP 0x80000 /* dentry requires i_op->lookup */
220 #define DCACHE_MANAGED_DENTRY \
221 (DCACHE_MOUNTED|DCACHE_NEED_AUTOMOUNT|DCACHE_MANAGE_TRANSIT)
223 extern seqlock_t rename_lock;
225 static inline int dname_external(struct dentry *dentry)
227 return dentry->d_name.name != dentry->d_iname;
231 * These are the low-level FS interfaces to the dcache..
233 extern void d_instantiate(struct dentry *, struct inode *);
234 extern struct dentry * d_instantiate_unique(struct dentry *, struct inode *);
235 extern struct dentry * d_materialise_unique(struct dentry *, struct inode *);
236 extern void __d_drop(struct dentry *dentry);
237 extern void d_drop(struct dentry *dentry);
238 extern void d_delete(struct dentry *);
239 extern void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op);
241 /* allocate/de-allocate */
242 extern struct dentry * d_alloc(struct dentry *, const struct qstr *);
243 extern struct dentry * d_alloc_pseudo(struct super_block *, const struct qstr *);
244 extern struct dentry * d_splice_alias(struct inode *, struct dentry *);
245 extern struct dentry * d_add_ci(struct dentry *, struct inode *, struct qstr *);
246 extern struct dentry * d_obtain_alias(struct inode *);
247 extern void shrink_dcache_sb(struct super_block *);
248 extern void shrink_dcache_parent(struct dentry *);
249 extern void shrink_dcache_for_umount(struct super_block *);
250 extern int d_invalidate(struct dentry *);
252 /* only used at mount-time */
253 extern struct dentry * d_alloc_root(struct inode *);
255 /* <clickety>-<click> the ramfs-type tree */
256 extern void d_genocide(struct dentry *);
258 extern struct dentry *d_find_alias(struct inode *);
259 extern void d_prune_aliases(struct inode *);
261 /* test whether we have any submounts in a subdir tree */
262 extern int have_submounts(struct dentry *);
265 * This adds the entry to the hash queues.
267 extern void d_rehash(struct dentry *);
270 * d_add - add dentry to hash queues
271 * @entry: dentry to add
272 * @inode: The inode to attach to this dentry
274 * This adds the entry to the hash queues and initializes @inode.
275 * The entry was actually filled in earlier during d_alloc().
278 static inline void d_add(struct dentry *entry, struct inode *inode)
280 d_instantiate(entry, inode);
285 * d_add_unique - add dentry to hash queues without aliasing
286 * @entry: dentry to add
287 * @inode: The inode to attach to this dentry
289 * This adds the entry to the hash queues and initializes @inode.
290 * The entry was actually filled in earlier during d_alloc().
292 static inline struct dentry *d_add_unique(struct dentry *entry, struct inode *inode)
296 res = d_instantiate_unique(entry, inode);
297 d_rehash(res != NULL ? res : entry);
301 extern void dentry_update_name_case(struct dentry *, struct qstr *);
303 /* used for rename() and baskets */
304 extern void d_move(struct dentry *, struct dentry *);
305 extern struct dentry *d_ancestor(struct dentry *, struct dentry *);
307 /* appendix may either be NULL or be used for transname suffixes */
308 extern struct dentry *d_lookup(struct dentry *, struct qstr *);
309 extern struct dentry *d_hash_and_lookup(struct dentry *, struct qstr *);
310 extern struct dentry *__d_lookup(struct dentry *, struct qstr *);
311 extern struct dentry *__d_lookup_rcu(struct dentry *parent, struct qstr *name,
312 unsigned *seq, struct inode **inode);
315 * __d_rcu_to_refcount - take a refcount on dentry if sequence check is ok
316 * @dentry: dentry to take a ref on
317 * @seq: seqcount to verify against
318 * Returns: 0 on failure, else 1.
320 * __d_rcu_to_refcount operates on a dentry,seq pair that was returned
321 * by __d_lookup_rcu, to get a reference on an rcu-walk dentry.
323 static inline int __d_rcu_to_refcount(struct dentry *dentry, unsigned seq)
327 assert_spin_locked(&dentry->d_lock);
328 if (!read_seqcount_retry(&dentry->d_seq, seq)) {
336 /* validate "insecure" dentry pointer */
337 extern int d_validate(struct dentry *, struct dentry *);
340 * helper function for dentry_operations.d_dname() members
342 extern char *dynamic_dname(struct dentry *, char *, int, const char *, ...);
344 extern char *__d_path(const struct path *path, struct path *root, char *, int);
345 extern char *d_path(const struct path *, char *, int);
346 extern char *d_path_with_unreachable(const struct path *, char *, int);
347 extern char *dentry_path_raw(struct dentry *, char *, int);
348 extern char *dentry_path(struct dentry *, char *, int);
350 /* Allocation counts.. */
353 * dget, dget_dlock - get a reference to a dentry
354 * @dentry: dentry to get a reference to
356 * Given a dentry or %NULL pointer increment the reference count
357 * if appropriate and return the dentry. A dentry will not be
358 * destroyed when it has references.
360 static inline struct dentry *dget_dlock(struct dentry *dentry)
367 static inline struct dentry *dget(struct dentry *dentry)
370 spin_lock(&dentry->d_lock);
372 spin_unlock(&dentry->d_lock);
377 extern struct dentry *dget_parent(struct dentry *dentry);
380 * d_unhashed - is dentry hashed
381 * @dentry: entry to check
383 * Returns true if the dentry passed is not currently hashed.
386 static inline int d_unhashed(struct dentry *dentry)
388 return hlist_bl_unhashed(&dentry->d_hash);
391 static inline int d_unlinked(struct dentry *dentry)
393 return d_unhashed(dentry) && !IS_ROOT(dentry);
396 static inline int cant_mount(struct dentry *dentry)
398 return (dentry->d_flags & DCACHE_CANT_MOUNT);
401 static inline void dont_mount(struct dentry *dentry)
403 spin_lock(&dentry->d_lock);
404 dentry->d_flags |= DCACHE_CANT_MOUNT;
405 spin_unlock(&dentry->d_lock);
408 extern void dput(struct dentry *);
410 static inline bool d_managed(struct dentry *dentry)
412 return dentry->d_flags & DCACHE_MANAGED_DENTRY;
415 static inline bool d_mountpoint(struct dentry *dentry)
417 return dentry->d_flags & DCACHE_MOUNTED;
420 static inline bool d_need_lookup(struct dentry *dentry)
422 return dentry->d_flags & DCACHE_NEED_LOOKUP;
425 extern void d_clear_need_lookup(struct dentry *dentry);
427 extern int sysctl_vfs_cache_pressure;
429 #endif /* __LINUX_DCACHE_H */