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>
12 #include <linux/lockref.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)
28 /* The hash is always the low bits of hash_len */
29 #ifdef __LITTLE_ENDIAN
30 #define HASH_LEN_DECLARE u32 hash; u32 len;
31 #define bytemask_from_count(cnt) (~(~0ul << (cnt)*8))
33 #define HASH_LEN_DECLARE u32 len; u32 hash;
34 #define bytemask_from_count(cnt) (~(~0ul >> (cnt)*8))
38 * "quick string" -- eases parameter passing, but more importantly
39 * saves "metadata" about the string (ie length and the hash).
41 * hash comes first so it snuggles against d_parent in the
51 const unsigned char *name;
54 #define QSTR_INIT(n,l) { { { .len = l } }, .name = n }
55 #define hashlen_hash(hashlen) ((u32) (hashlen))
56 #define hashlen_len(hashlen) ((u32)((hashlen) >> 32))
57 #define hashlen_create(hash,len) (((u64)(len)<<32)|(u32)(hash))
59 struct dentry_stat_t {
62 long age_limit; /* age in seconds */
63 long want_pages; /* pages requested by system */
66 extern struct dentry_stat_t dentry_stat;
68 /* Name hashing routines. Initial hash value */
69 /* Hash courtesy of the R5 hash in reiserfs modulo sign bits */
70 #define init_name_hash() 0
72 /* partial hash update function. Assume roughly 4 bits per character */
73 static inline unsigned long
74 partial_name_hash(unsigned long c, unsigned long prevhash)
76 return (prevhash + (c << 4) + (c >> 4)) * 11;
80 * Finally: cut down the number of bits to a int value (and try to avoid
83 static inline unsigned long end_name_hash(unsigned long hash)
85 return (unsigned int) hash;
88 /* Compute the hash for a name string. */
89 extern unsigned int full_name_hash(const unsigned char *, unsigned int);
92 * Try to keep struct dentry aligned on 64 byte cachelines (this will
93 * give reasonable cacheline footprint with larger lines without the
94 * large memory footprint increase).
97 # define DNAME_INLINE_LEN 32 /* 192 bytes */
100 # define DNAME_INLINE_LEN 36 /* 128 bytes */
102 # define DNAME_INLINE_LEN 40 /* 128 bytes */
106 #define d_lock d_lockref.lock
109 /* RCU lookup touched fields */
110 unsigned int d_flags; /* protected by d_lock */
111 seqcount_t d_seq; /* per dentry seqlock */
112 struct hlist_bl_node d_hash; /* lookup hash list */
113 struct dentry *d_parent; /* parent directory */
115 struct inode *d_inode; /* Where the name belongs to - NULL is
117 unsigned char d_iname[DNAME_INLINE_LEN]; /* small names */
119 /* Ref lookup also touches following */
120 struct lockref d_lockref; /* per-dentry lock and refcount */
121 const struct dentry_operations *d_op;
122 struct super_block *d_sb; /* The root of the dentry tree */
123 unsigned long d_time; /* used by d_revalidate */
124 void *d_fsdata; /* fs-specific data */
126 struct list_head d_lru; /* LRU list */
127 struct list_head d_child; /* child of parent list */
128 struct list_head d_subdirs; /* our children */
130 * d_alias and d_rcu can share memory
133 struct hlist_node d_alias; /* inode alias list */
134 struct rcu_head d_rcu;
139 * dentry->d_lock spinlock nesting subclasses:
144 enum dentry_d_lock_class
146 DENTRY_D_LOCK_NORMAL, /* implicitly used by plain spin_lock() APIs. */
150 struct dentry_operations {
151 int (*d_revalidate)(struct dentry *, unsigned int);
152 int (*d_weak_revalidate)(struct dentry *, unsigned int);
153 int (*d_hash)(const struct dentry *, struct qstr *);
154 int (*d_compare)(const struct dentry *, const struct dentry *,
155 unsigned int, const char *, const struct qstr *);
156 int (*d_delete)(const struct dentry *);
157 void (*d_release)(struct dentry *);
158 void (*d_prune)(struct dentry *);
159 void (*d_iput)(struct dentry *, struct inode *);
160 char *(*d_dname)(struct dentry *, char *, int);
161 struct vfsmount *(*d_automount)(struct path *);
162 int (*d_manage)(struct dentry *, bool);
163 struct inode *(*d_select_inode)(struct dentry *, unsigned);
164 struct dentry *(*d_real)(struct dentry *, struct inode *);
165 } ____cacheline_aligned;
168 * Locking rules for dentry_operations callbacks are to be found in
169 * Documentation/filesystems/Locking. Keep it updated!
171 * FUrther descriptions are found in Documentation/filesystems/vfs.txt.
172 * Keep it updated too!
175 /* d_flags entries */
176 #define DCACHE_OP_HASH 0x00000001
177 #define DCACHE_OP_COMPARE 0x00000002
178 #define DCACHE_OP_REVALIDATE 0x00000004
179 #define DCACHE_OP_DELETE 0x00000008
180 #define DCACHE_OP_PRUNE 0x00000010
182 #define DCACHE_DISCONNECTED 0x00000020
183 /* This dentry is possibly not currently connected to the dcache tree, in
184 * which case its parent will either be itself, or will have this flag as
185 * well. nfsd will not use a dentry with this bit set, but will first
186 * endeavour to clear the bit either by discovering that it is connected,
187 * or by performing lookup operations. Any filesystem which supports
188 * nfsd_operations MUST have a lookup function which, if it finds a
189 * directory inode with a DCACHE_DISCONNECTED dentry, will d_move that
190 * dentry into place and return that dentry rather than the passed one,
191 * typically using d_splice_alias. */
193 #define DCACHE_REFERENCED 0x00000040 /* Recently used, don't discard. */
194 #define DCACHE_RCUACCESS 0x00000080 /* Entry has ever been RCU-visible */
196 #define DCACHE_CANT_MOUNT 0x00000100
197 #define DCACHE_GENOCIDE 0x00000200
198 #define DCACHE_SHRINK_LIST 0x00000400
200 #define DCACHE_OP_WEAK_REVALIDATE 0x00000800
202 #define DCACHE_NFSFS_RENAMED 0x00001000
203 /* this dentry has been "silly renamed" and has to be deleted on the last
205 #define DCACHE_COOKIE 0x00002000 /* For use by dcookie subsystem */
206 #define DCACHE_FSNOTIFY_PARENT_WATCHED 0x00004000
207 /* Parent inode is watched by some fsnotify listener */
209 #define DCACHE_DENTRY_KILLED 0x00008000
211 #define DCACHE_MOUNTED 0x00010000 /* is a mountpoint */
212 #define DCACHE_NEED_AUTOMOUNT 0x00020000 /* handle automount on this dir */
213 #define DCACHE_MANAGE_TRANSIT 0x00040000 /* manage transit from this dirent */
214 #define DCACHE_MANAGED_DENTRY \
215 (DCACHE_MOUNTED|DCACHE_NEED_AUTOMOUNT|DCACHE_MANAGE_TRANSIT)
217 #define DCACHE_LRU_LIST 0x00080000
219 #define DCACHE_ENTRY_TYPE 0x00700000
220 #define DCACHE_MISS_TYPE 0x00000000 /* Negative dentry (maybe fallthru to nowhere) */
221 #define DCACHE_WHITEOUT_TYPE 0x00100000 /* Whiteout dentry (stop pathwalk) */
222 #define DCACHE_DIRECTORY_TYPE 0x00200000 /* Normal directory */
223 #define DCACHE_AUTODIR_TYPE 0x00300000 /* Lookupless directory (presumed automount) */
224 #define DCACHE_REGULAR_TYPE 0x00400000 /* Regular file type (or fallthru to such) */
225 #define DCACHE_SPECIAL_TYPE 0x00500000 /* Other file type (or fallthru to such) */
226 #define DCACHE_SYMLINK_TYPE 0x00600000 /* Symlink (or fallthru to such) */
228 #define DCACHE_MAY_FREE 0x00800000
229 #define DCACHE_FALLTHRU 0x01000000 /* Fall through to lower layer */
230 #define DCACHE_OP_SELECT_INODE 0x02000000 /* Unioned entry: dcache op selects inode */
231 #define DCACHE_OP_REAL 0x08000000
233 extern seqlock_t rename_lock;
236 * These are the low-level FS interfaces to the dcache..
238 extern void d_instantiate(struct dentry *, struct inode *);
239 extern void d_instantiate_new(struct dentry *, struct inode *);
240 extern struct dentry * d_instantiate_unique(struct dentry *, struct inode *);
241 extern int d_instantiate_no_diralias(struct dentry *, struct inode *);
242 extern void __d_drop(struct dentry *dentry);
243 extern void d_drop(struct dentry *dentry);
244 extern void d_delete(struct dentry *);
245 extern void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op);
247 /* allocate/de-allocate */
248 extern struct dentry * d_alloc(struct dentry *, const struct qstr *);
249 extern struct dentry * d_alloc_pseudo(struct super_block *, const struct qstr *);
250 extern struct dentry * d_splice_alias(struct inode *, struct dentry *);
251 extern struct dentry * d_add_ci(struct dentry *, struct inode *, struct qstr *);
252 extern struct dentry *d_find_any_alias(struct inode *inode);
253 extern struct dentry * d_obtain_alias(struct inode *);
254 extern struct dentry * d_obtain_root(struct inode *);
255 extern void shrink_dcache_sb(struct super_block *);
256 extern void shrink_dcache_parent(struct dentry *);
257 extern void shrink_dcache_for_umount(struct super_block *);
258 extern void d_invalidate(struct dentry *);
260 /* only used at mount-time */
261 extern struct dentry * d_make_root(struct inode *);
263 /* <clickety>-<click> the ramfs-type tree */
264 extern void d_genocide(struct dentry *);
266 extern void d_tmpfile(struct dentry *, struct inode *);
268 extern struct dentry *d_find_alias(struct inode *);
269 extern void d_prune_aliases(struct inode *);
271 /* test whether we have any submounts in a subdir tree */
272 extern int have_submounts(struct dentry *);
275 * This adds the entry to the hash queues.
277 extern void d_rehash(struct dentry *);
280 * d_add - add dentry to hash queues
281 * @entry: dentry to add
282 * @inode: The inode to attach to this dentry
284 * This adds the entry to the hash queues and initializes @inode.
285 * The entry was actually filled in earlier during d_alloc().
288 static inline void d_add(struct dentry *entry, struct inode *inode)
290 d_instantiate(entry, inode);
295 * d_add_unique - add dentry to hash queues without aliasing
296 * @entry: dentry to add
297 * @inode: The inode to attach to this dentry
299 * This adds the entry to the hash queues and initializes @inode.
300 * The entry was actually filled in earlier during d_alloc().
302 static inline struct dentry *d_add_unique(struct dentry *entry, struct inode *inode)
306 res = d_instantiate_unique(entry, inode);
307 d_rehash(res != NULL ? res : entry);
311 extern void dentry_update_name_case(struct dentry *, struct qstr *);
313 /* used for rename() and baskets */
314 extern void d_move(struct dentry *, struct dentry *);
315 extern void d_exchange(struct dentry *, struct dentry *);
316 extern struct dentry *d_ancestor(struct dentry *, struct dentry *);
318 /* appendix may either be NULL or be used for transname suffixes */
319 extern struct dentry *d_lookup(const struct dentry *, const struct qstr *);
320 extern struct dentry *d_hash_and_lookup(struct dentry *, struct qstr *);
321 extern struct dentry *__d_lookup(const struct dentry *, const struct qstr *);
322 extern struct dentry *__d_lookup_rcu(const struct dentry *parent,
323 const struct qstr *name, unsigned *seq);
325 static inline unsigned d_count(const struct dentry *dentry)
327 return dentry->d_lockref.count;
331 * helper function for dentry_operations.d_dname() members
333 extern __printf(4, 5)
334 char *dynamic_dname(struct dentry *, char *, int, const char *, ...);
335 extern char *simple_dname(struct dentry *, char *, int);
337 extern char *__d_path(const struct path *, const struct path *, char *, int);
338 extern char *d_absolute_path(const struct path *, char *, int);
339 extern char *d_path(const struct path *, char *, int);
340 extern char *dentry_path_raw(struct dentry *, char *, int);
341 extern char *dentry_path(struct dentry *, char *, int);
343 /* Allocation counts.. */
346 * dget, dget_dlock - get a reference to a dentry
347 * @dentry: dentry to get a reference to
349 * Given a dentry or %NULL pointer increment the reference count
350 * if appropriate and return the dentry. A dentry will not be
351 * destroyed when it has references.
353 static inline struct dentry *dget_dlock(struct dentry *dentry)
356 dentry->d_lockref.count++;
360 static inline struct dentry *dget(struct dentry *dentry)
363 lockref_get(&dentry->d_lockref);
367 extern struct dentry *dget_parent(struct dentry *dentry);
370 * d_unhashed - is dentry hashed
371 * @dentry: entry to check
373 * Returns true if the dentry passed is not currently hashed.
376 static inline int d_unhashed(const struct dentry *dentry)
378 return hlist_bl_unhashed(&dentry->d_hash);
381 static inline int d_unlinked(const struct dentry *dentry)
383 return d_unhashed(dentry) && !IS_ROOT(dentry);
386 static inline int cant_mount(const struct dentry *dentry)
388 return (dentry->d_flags & DCACHE_CANT_MOUNT);
391 static inline void dont_mount(struct dentry *dentry)
393 spin_lock(&dentry->d_lock);
394 dentry->d_flags |= DCACHE_CANT_MOUNT;
395 spin_unlock(&dentry->d_lock);
398 extern void dput(struct dentry *);
400 static inline bool d_managed(const struct dentry *dentry)
402 return dentry->d_flags & DCACHE_MANAGED_DENTRY;
405 static inline bool d_mountpoint(const struct dentry *dentry)
407 return dentry->d_flags & DCACHE_MOUNTED;
411 * Directory cache entry type accessor functions.
413 static inline unsigned __d_entry_type(const struct dentry *dentry)
415 return dentry->d_flags & DCACHE_ENTRY_TYPE;
418 static inline bool d_is_miss(const struct dentry *dentry)
420 return __d_entry_type(dentry) == DCACHE_MISS_TYPE;
423 static inline bool d_is_whiteout(const struct dentry *dentry)
425 return __d_entry_type(dentry) == DCACHE_WHITEOUT_TYPE;
428 static inline bool d_can_lookup(const struct dentry *dentry)
430 return __d_entry_type(dentry) == DCACHE_DIRECTORY_TYPE;
433 static inline bool d_is_autodir(const struct dentry *dentry)
435 return __d_entry_type(dentry) == DCACHE_AUTODIR_TYPE;
438 static inline bool d_is_dir(const struct dentry *dentry)
440 return d_can_lookup(dentry) || d_is_autodir(dentry);
443 static inline bool d_is_symlink(const struct dentry *dentry)
445 return __d_entry_type(dentry) == DCACHE_SYMLINK_TYPE;
448 static inline bool d_is_reg(const struct dentry *dentry)
450 return __d_entry_type(dentry) == DCACHE_REGULAR_TYPE;
453 static inline bool d_is_special(const struct dentry *dentry)
455 return __d_entry_type(dentry) == DCACHE_SPECIAL_TYPE;
458 static inline bool d_is_file(const struct dentry *dentry)
460 return d_is_reg(dentry) || d_is_special(dentry);
463 static inline bool d_is_negative(const struct dentry *dentry)
465 // TODO: check d_is_whiteout(dentry) also.
466 return d_is_miss(dentry);
469 static inline bool d_is_positive(const struct dentry *dentry)
471 return !d_is_negative(dentry);
475 * d_really_is_negative - Determine if a dentry is really negative (ignoring fallthroughs)
476 * @dentry: The dentry in question
478 * Returns true if the dentry represents either an absent name or a name that
479 * doesn't map to an inode (ie. ->d_inode is NULL). The dentry could represent
480 * a true miss, a whiteout that isn't represented by a 0,0 chardev or a
481 * fallthrough marker in an opaque directory.
483 * Note! (1) This should be used *only* by a filesystem to examine its own
484 * dentries. It should not be used to look at some other filesystem's
485 * dentries. (2) It should also be used in combination with d_inode() to get
486 * the inode. (3) The dentry may have something attached to ->d_lower and the
487 * type field of the flags may be set to something other than miss or whiteout.
489 static inline bool d_really_is_negative(const struct dentry *dentry)
491 return dentry->d_inode == NULL;
495 * d_really_is_positive - Determine if a dentry is really positive (ignoring fallthroughs)
496 * @dentry: The dentry in question
498 * Returns true if the dentry represents a name that maps to an inode
499 * (ie. ->d_inode is not NULL). The dentry might still represent a whiteout if
500 * that is represented on medium as a 0,0 chardev.
502 * Note! (1) This should be used *only* by a filesystem to examine its own
503 * dentries. It should not be used to look at some other filesystem's
504 * dentries. (2) It should also be used in combination with d_inode() to get
507 static inline bool d_really_is_positive(const struct dentry *dentry)
509 return dentry->d_inode != NULL;
512 static inline int simple_positive(struct dentry *dentry)
514 return d_really_is_positive(dentry) && !d_unhashed(dentry);
517 extern void d_set_fallthru(struct dentry *dentry);
519 static inline bool d_is_fallthru(const struct dentry *dentry)
521 return dentry->d_flags & DCACHE_FALLTHRU;
525 extern int sysctl_vfs_cache_pressure;
527 static inline unsigned long vfs_pressure_ratio(unsigned long val)
529 return mult_frac(val, sysctl_vfs_cache_pressure, 100);
533 * d_inode - Get the actual inode of this dentry
534 * @dentry: The dentry to query
536 * This is the helper normal filesystems should use to get at their own inodes
537 * in their own dentries and ignore the layering superimposed upon them.
539 static inline struct inode *d_inode(const struct dentry *dentry)
541 return dentry->d_inode;
545 * d_inode_rcu - Get the actual inode of this dentry with ACCESS_ONCE()
546 * @dentry: The dentry to query
548 * This is the helper normal filesystems should use to get at their own inodes
549 * in their own dentries and ignore the layering superimposed upon them.
551 static inline struct inode *d_inode_rcu(const struct dentry *dentry)
553 return ACCESS_ONCE(dentry->d_inode);
557 * d_backing_inode - Get upper or lower inode we should be using
558 * @upper: The upper layer
560 * This is the helper that should be used to get at the inode that will be used
561 * if this dentry were to be opened as a file. The inode may be on the upper
562 * dentry or it may be on a lower dentry pinned by the upper.
564 * Normal filesystems should not use this to access their own inodes.
566 static inline struct inode *d_backing_inode(const struct dentry *upper)
568 struct inode *inode = upper->d_inode;
574 * d_backing_dentry - Get upper or lower dentry we should be using
575 * @upper: The upper layer
577 * This is the helper that should be used to get the dentry of the inode that
578 * will be used if this dentry were opened as a file. It may be the upper
579 * dentry or it may be a lower dentry pinned by the upper.
581 * Normal filesystems should not use this to access their own dentries.
583 static inline struct dentry *d_backing_dentry(struct dentry *upper)
588 static inline struct dentry *d_real(struct dentry *dentry)
590 if (unlikely(dentry->d_flags & DCACHE_OP_REAL))
591 return dentry->d_op->d_real(dentry, NULL);
596 static inline struct inode *vfs_select_inode(struct dentry *dentry,
599 struct inode *inode = d_inode(dentry);
601 if (inode && unlikely(dentry->d_flags & DCACHE_OP_SELECT_INODE))
602 inode = dentry->d_op->d_select_inode(dentry, open_flags);
608 * d_real_inode - Return the real inode
609 * @dentry: The dentry to query
611 * If dentry is on an union/overlay, then return the underlying, real inode.
612 * Otherwise return d_inode().
614 static inline struct inode *d_real_inode(struct dentry *dentry)
616 return d_backing_inode(d_real(dentry));
619 struct name_snapshot {
621 char inline_name[DNAME_INLINE_LEN];
623 void take_dentry_name_snapshot(struct name_snapshot *, struct dentry *);
624 void release_dentry_name_snapshot(struct name_snapshot *);
626 #endif /* __LINUX_DCACHE_H */