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 extern unsigned int full_name_hash(const unsigned char *, unsigned int);
95 * Try to keep struct dentry aligned on 64 byte cachelines (this will
96 * give reasonable cacheline footprint with larger lines without the
97 * large memory footprint increase).
100 # define DNAME_INLINE_LEN 32 /* 192 bytes */
103 # define DNAME_INLINE_LEN 36 /* 128 bytes */
105 # define DNAME_INLINE_LEN 40 /* 128 bytes */
110 /* RCU lookup touched fields */
111 unsigned int d_flags; /* protected by d_lock */
112 seqcount_t d_seq; /* per dentry seqlock */
113 struct hlist_bl_node d_hash; /* lookup hash list */
114 struct dentry *d_parent; /* parent directory */
116 struct inode *d_inode; /* Where the name belongs to - NULL is
118 unsigned char d_iname[DNAME_INLINE_LEN]; /* small names */
120 /* Ref lookup also touches following */
121 unsigned int d_count; /* protected by d_lock */
122 spinlock_t d_lock; /* per dentry lock */
123 const struct dentry_operations *d_op;
124 struct super_block *d_sb; /* The root of the dentry tree */
125 unsigned long d_time; /* used by d_revalidate */
126 void *d_fsdata; /* fs-specific data */
128 struct list_head d_lru; /* LRU list */
130 * d_child and d_rcu can share memory
133 struct list_head d_child; /* child of parent list */
134 struct rcu_head d_rcu;
136 struct list_head d_subdirs; /* our children */
137 struct list_head d_alias; /* inode alias list */
141 * dentry->d_lock spinlock nesting subclasses:
146 enum dentry_d_lock_class
148 DENTRY_D_LOCK_NORMAL, /* implicitly used by plain spin_lock() APIs. */
152 struct dentry_operations {
153 int (*d_revalidate)(struct dentry *, struct nameidata *);
154 int (*d_hash)(const struct dentry *, const struct inode *,
156 int (*d_compare)(const struct dentry *, const struct inode *,
157 const struct dentry *, const struct inode *,
158 unsigned int, const char *, const struct qstr *);
159 int (*d_delete)(const struct dentry *);
160 void (*d_release)(struct dentry *);
161 void (*d_prune)(struct dentry *);
162 void (*d_iput)(struct dentry *, struct inode *);
163 char *(*d_dname)(struct dentry *, char *, int);
164 struct vfsmount *(*d_automount)(struct path *);
165 int (*d_manage)(struct dentry *, bool);
166 } ____cacheline_aligned;
169 * Locking rules for dentry_operations callbacks are to be found in
170 * Documentation/filesystems/Locking. Keep it updated!
172 * FUrther descriptions are found in Documentation/filesystems/vfs.txt.
173 * Keep it updated too!
176 /* d_flags entries */
177 #define DCACHE_OP_HASH 0x0001
178 #define DCACHE_OP_COMPARE 0x0002
179 #define DCACHE_OP_REVALIDATE 0x0004
180 #define DCACHE_OP_DELETE 0x0008
181 #define DCACHE_OP_PRUNE 0x0010
183 #define DCACHE_DISCONNECTED 0x0020
184 /* This dentry is possibly not currently connected to the dcache tree, in
185 * which case its parent will either be itself, or will have this flag as
186 * well. nfsd will not use a dentry with this bit set, but will first
187 * endeavour to clear the bit either by discovering that it is connected,
188 * or by performing lookup operations. Any filesystem which supports
189 * nfsd_operations MUST have a lookup function which, if it finds a
190 * directory inode with a DCACHE_DISCONNECTED dentry, will d_move that
191 * dentry into place and return that dentry rather than the passed one,
192 * typically using d_splice_alias. */
194 #define DCACHE_REFERENCED 0x0040 /* Recently used, don't discard. */
195 #define DCACHE_RCUACCESS 0x0080 /* Entry has ever been RCU-visible */
197 #define DCACHE_CANT_MOUNT 0x0100
198 #define DCACHE_GENOCIDE 0x0200
199 #define DCACHE_SHRINK_LIST 0x0400
201 #define DCACHE_NFSFS_RENAMED 0x1000
202 /* this dentry has been "silly renamed" and has to be deleted on the last
204 #define DCACHE_COOKIE 0x2000 /* For use by dcookie subsystem */
205 #define DCACHE_FSNOTIFY_PARENT_WATCHED 0x4000
206 /* Parent inode is watched by some fsnotify listener */
208 #define DCACHE_MOUNTED 0x10000 /* is a mountpoint */
209 #define DCACHE_NEED_AUTOMOUNT 0x20000 /* handle automount on this dir */
210 #define DCACHE_MANAGE_TRANSIT 0x40000 /* manage transit from this dirent */
211 #define DCACHE_NEED_LOOKUP 0x80000 /* dentry requires i_op->lookup */
212 #define DCACHE_MANAGED_DENTRY \
213 (DCACHE_MOUNTED|DCACHE_NEED_AUTOMOUNT|DCACHE_MANAGE_TRANSIT)
215 extern seqlock_t rename_lock;
217 static inline int dname_external(struct dentry *dentry)
219 return dentry->d_name.name != dentry->d_iname;
223 * These are the low-level FS interfaces to the dcache..
225 extern void d_instantiate(struct dentry *, struct inode *);
226 extern struct dentry * d_instantiate_unique(struct dentry *, struct inode *);
227 extern struct dentry * d_materialise_unique(struct dentry *, struct inode *);
228 extern void __d_drop(struct dentry *dentry);
229 extern void d_drop(struct dentry *dentry);
230 extern void d_delete(struct dentry *);
231 extern void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op);
233 /* allocate/de-allocate */
234 extern struct dentry * d_alloc(struct dentry *, const struct qstr *);
235 extern struct dentry * d_alloc_pseudo(struct super_block *, const struct qstr *);
236 extern struct dentry * d_splice_alias(struct inode *, struct dentry *);
237 extern struct dentry * d_add_ci(struct dentry *, struct inode *, struct qstr *);
238 extern struct dentry *d_find_any_alias(struct inode *inode);
239 extern struct dentry * d_obtain_alias(struct inode *);
240 extern void shrink_dcache_sb(struct super_block *);
241 extern void shrink_dcache_parent(struct dentry *);
242 extern void shrink_dcache_for_umount(struct super_block *);
243 extern int d_invalidate(struct dentry *);
245 /* only used at mount-time */
246 extern struct dentry * d_alloc_root(struct inode *);
247 extern struct dentry * d_make_root(struct inode *);
249 /* <clickety>-<click> the ramfs-type tree */
250 extern void d_genocide(struct dentry *);
252 extern struct dentry *d_find_alias(struct inode *);
253 extern void d_prune_aliases(struct inode *);
255 /* test whether we have any submounts in a subdir tree */
256 extern int have_submounts(struct dentry *);
259 * This adds the entry to the hash queues.
261 extern void d_rehash(struct dentry *);
264 * d_add - add dentry to hash queues
265 * @entry: dentry to add
266 * @inode: The inode to attach to this dentry
268 * This adds the entry to the hash queues and initializes @inode.
269 * The entry was actually filled in earlier during d_alloc().
272 static inline void d_add(struct dentry *entry, struct inode *inode)
274 d_instantiate(entry, inode);
279 * d_add_unique - add dentry to hash queues without aliasing
280 * @entry: dentry to add
281 * @inode: The inode to attach to this dentry
283 * This adds the entry to the hash queues and initializes @inode.
284 * The entry was actually filled in earlier during d_alloc().
286 static inline struct dentry *d_add_unique(struct dentry *entry, struct inode *inode)
290 res = d_instantiate_unique(entry, inode);
291 d_rehash(res != NULL ? res : entry);
295 extern void dentry_update_name_case(struct dentry *, struct qstr *);
297 /* used for rename() and baskets */
298 extern void d_move(struct dentry *, struct dentry *);
299 extern struct dentry *d_ancestor(struct dentry *, struct dentry *);
301 /* appendix may either be NULL or be used for transname suffixes */
302 extern struct dentry *d_lookup(struct dentry *, struct qstr *);
303 extern struct dentry *d_hash_and_lookup(struct dentry *, struct qstr *);
304 extern struct dentry *__d_lookup(struct dentry *, struct qstr *);
305 extern struct dentry *__d_lookup_rcu(const struct dentry *parent,
306 const struct qstr *name,
307 unsigned *seq, struct inode **inode);
310 * __d_rcu_to_refcount - take a refcount on dentry if sequence check is ok
311 * @dentry: dentry to take a ref on
312 * @seq: seqcount to verify against
313 * Returns: 0 on failure, else 1.
315 * __d_rcu_to_refcount operates on a dentry,seq pair that was returned
316 * by __d_lookup_rcu, to get a reference on an rcu-walk dentry.
318 static inline int __d_rcu_to_refcount(struct dentry *dentry, unsigned seq)
322 assert_spin_locked(&dentry->d_lock);
323 if (!read_seqcount_retry(&dentry->d_seq, seq)) {
331 /* validate "insecure" dentry pointer */
332 extern int d_validate(struct dentry *, struct dentry *);
335 * helper function for dentry_operations.d_dname() members
337 extern char *dynamic_dname(struct dentry *, char *, int, const char *, ...);
339 extern char *__d_path(const struct path *, const struct path *, char *, int);
340 extern char *d_absolute_path(const struct path *, char *, int);
341 extern char *d_path(const struct path *, char *, int);
342 extern char *d_path_with_unreachable(const struct path *, char *, int);
343 extern char *dentry_path_raw(struct dentry *, char *, int);
344 extern char *dentry_path(struct dentry *, char *, int);
346 /* Allocation counts.. */
349 * dget, dget_dlock - get a reference to a dentry
350 * @dentry: dentry to get a reference to
352 * Given a dentry or %NULL pointer increment the reference count
353 * if appropriate and return the dentry. A dentry will not be
354 * destroyed when it has references.
356 static inline struct dentry *dget_dlock(struct dentry *dentry)
363 static inline struct dentry *dget(struct dentry *dentry)
366 spin_lock(&dentry->d_lock);
368 spin_unlock(&dentry->d_lock);
373 extern struct dentry *dget_parent(struct dentry *dentry);
376 * d_unhashed - is dentry hashed
377 * @dentry: entry to check
379 * Returns true if the dentry passed is not currently hashed.
382 static inline int d_unhashed(struct dentry *dentry)
384 return hlist_bl_unhashed(&dentry->d_hash);
387 static inline int d_unlinked(struct dentry *dentry)
389 return d_unhashed(dentry) && !IS_ROOT(dentry);
392 static inline int cant_mount(struct dentry *dentry)
394 return (dentry->d_flags & DCACHE_CANT_MOUNT);
397 static inline void dont_mount(struct dentry *dentry)
399 spin_lock(&dentry->d_lock);
400 dentry->d_flags |= DCACHE_CANT_MOUNT;
401 spin_unlock(&dentry->d_lock);
404 extern void dput(struct dentry *);
406 static inline bool d_managed(struct dentry *dentry)
408 return dentry->d_flags & DCACHE_MANAGED_DENTRY;
411 static inline bool d_mountpoint(struct dentry *dentry)
413 return dentry->d_flags & DCACHE_MOUNTED;
416 static inline bool d_need_lookup(struct dentry *dentry)
418 return dentry->d_flags & DCACHE_NEED_LOOKUP;
421 extern void d_clear_need_lookup(struct dentry *dentry);
423 extern int sysctl_vfs_cache_pressure;
425 #endif /* __LINUX_DCACHE_H */