[PATCH] AUTOFS: Make sure all dentries refs are released before calling kill_anon_super()
[linux-2.6-block.git] / include / linux / dcache.h
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1da177e4
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1#ifndef __LINUX_DCACHE_H
2#define __LINUX_DCACHE_H
3
4#ifdef __KERNEL__
5
6#include <asm/atomic.h>
7#include <linux/list.h>
8#include <linux/spinlock.h>
9#include <linux/cache.h>
10#include <linux/rcupdate.h>
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11
12struct nameidata;
13struct vfsmount;
14
15/*
16 * linux/include/linux/dcache.h
17 *
18 * Dirent cache data structures
19 *
20 * (C) Copyright 1997 Thomas Schoebel-Theuer,
21 * with heavy changes by Linus Torvalds
22 */
23
24#define IS_ROOT(x) ((x) == (x)->d_parent)
25
26/*
27 * "quick string" -- eases parameter passing, but more importantly
28 * saves "metadata" about the string (ie length and the hash).
29 *
30 * hash comes first so it snuggles against d_parent in the
31 * dentry.
32 */
33struct qstr {
34 unsigned int hash;
35 unsigned int len;
36 const unsigned char *name;
37};
38
39struct dentry_stat_t {
40 int nr_dentry;
41 int nr_unused;
42 int age_limit; /* age in seconds */
43 int want_pages; /* pages requested by system */
44 int dummy[2];
45};
46extern struct dentry_stat_t dentry_stat;
47
48/* Name hashing routines. Initial hash value */
49/* Hash courtesy of the R5 hash in reiserfs modulo sign bits */
50#define init_name_hash() 0
51
52/* partial hash update function. Assume roughly 4 bits per character */
53static inline unsigned long
54partial_name_hash(unsigned long c, unsigned long prevhash)
55{
56 return (prevhash + (c << 4) + (c >> 4)) * 11;
57}
58
59/*
60 * Finally: cut down the number of bits to a int value (and try to avoid
61 * losing bits)
62 */
63static inline unsigned long end_name_hash(unsigned long hash)
64{
65 return (unsigned int) hash;
66}
67
68/* Compute the hash for a name string. */
69static inline unsigned int
70full_name_hash(const unsigned char *name, unsigned int len)
71{
72 unsigned long hash = init_name_hash();
73 while (len--)
74 hash = partial_name_hash(*name++, hash);
75 return end_name_hash(hash);
76}
77
78struct dcookie_struct;
79
80#define DNAME_INLINE_LEN_MIN 36
81
82struct dentry {
83 atomic_t d_count;
84 unsigned int d_flags; /* protected by d_lock */
85 spinlock_t d_lock; /* per dentry lock */
86 struct inode *d_inode; /* Where the name belongs to - NULL is
87 * negative */
88 /*
89 * The next three fields are touched by __d_lookup. Place them here
3f4bb1f4 90 * so they all fit in a cache line.
1da177e4 91 */
3f4bb1f4 92 struct hlist_node d_hash; /* lookup hash list */
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93 struct dentry *d_parent; /* parent directory */
94 struct qstr d_name;
95
96 struct list_head d_lru; /* LRU list */
5160ee6f
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97 /*
98 * d_child and d_rcu can share memory
99 */
100 union {
101 struct list_head d_child; /* child of parent list */
102 struct rcu_head d_rcu;
103 } d_u;
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104 struct list_head d_subdirs; /* our children */
105 struct list_head d_alias; /* inode alias list */
106 unsigned long d_time; /* used by d_revalidate */
107 struct dentry_operations *d_op;
108 struct super_block *d_sb; /* The root of the dentry tree */
109 void *d_fsdata; /* fs-specific data */
47ba87e0 110#ifdef CONFIG_PROFILING
1da177e4 111 struct dcookie_struct *d_cookie; /* cookie, if any */
47ba87e0 112#endif
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113 int d_mounted;
114 unsigned char d_iname[DNAME_INLINE_LEN_MIN]; /* small names */
115};
116
a90b9c05
IM
117/*
118 * dentry->d_lock spinlock nesting subclasses:
119 *
120 * 0: normal
121 * 1: nested
122 */
123enum dentry_d_lock_class
124{
125 DENTRY_D_LOCK_NORMAL, /* implicitly used by plain spin_lock() APIs. */
126 DENTRY_D_LOCK_NESTED
127};
128
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129struct dentry_operations {
130 int (*d_revalidate)(struct dentry *, struct nameidata *);
131 int (*d_hash) (struct dentry *, struct qstr *);
132 int (*d_compare) (struct dentry *, struct qstr *, struct qstr *);
133 int (*d_delete)(struct dentry *);
134 void (*d_release)(struct dentry *);
135 void (*d_iput)(struct dentry *, struct inode *);
136};
137
138/* the dentry parameter passed to d_hash and d_compare is the parent
139 * directory of the entries to be compared. It is used in case these
140 * functions need any directory specific information for determining
141 * equivalency classes. Using the dentry itself might not work, as it
142 * might be a negative dentry which has no information associated with
143 * it */
144
145/*
146locking rules:
147 big lock dcache_lock d_lock may block
148d_revalidate: no no no yes
149d_hash no no no yes
150d_compare: no yes yes no
151d_delete: no yes no no
152d_release: no no no yes
153d_iput: no no no yes
154 */
155
156/* d_flags entries */
157#define DCACHE_AUTOFS_PENDING 0x0001 /* autofs: "under construction" */
158#define DCACHE_NFSFS_RENAMED 0x0002 /* this dentry has been "silly
159 * renamed" and has to be
160 * deleted on the last dput()
161 */
162#define DCACHE_DISCONNECTED 0x0004
163 /* This dentry is possibly not currently connected to the dcache tree,
164 * in which case its parent will either be itself, or will have this
165 * flag as well. nfsd will not use a dentry with this bit set, but will
166 * first endeavour to clear the bit either by discovering that it is
167 * connected, or by performing lookup operations. Any filesystem which
168 * supports nfsd_operations MUST have a lookup function which, if it finds
169 * a directory inode with a DCACHE_DISCONNECTED dentry, will d_move
170 * that dentry into place and return that dentry rather than the passed one,
171 * typically using d_splice_alias.
172 */
173
174#define DCACHE_REFERENCED 0x0008 /* Recently used, don't discard. */
175#define DCACHE_UNHASHED 0x0010
176
c32ccd87
NP
177#define DCACHE_INOTIFY_PARENT_WATCHED 0x0020 /* Parent inode is watched */
178
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179extern spinlock_t dcache_lock;
180
181/**
182 * d_drop - drop a dentry
183 * @dentry: dentry to drop
184 *
185 * d_drop() unhashes the entry from the parent dentry hashes, so that it won't
186 * be found through a VFS lookup any more. Note that this is different from
187 * deleting the dentry - d_delete will try to mark the dentry negative if
188 * possible, giving a successful _negative_ lookup, while d_drop will
189 * just make the cache lookup fail.
190 *
191 * d_drop() is used mainly for stuff that wants to invalidate a dentry for some
192 * reason (NFS timeouts or autofs deletes).
193 *
194 * __d_drop requires dentry->d_lock.
195 */
196
197static inline void __d_drop(struct dentry *dentry)
198{
199 if (!(dentry->d_flags & DCACHE_UNHASHED)) {
200 dentry->d_flags |= DCACHE_UNHASHED;
201 hlist_del_rcu(&dentry->d_hash);
202 }
203}
204
205static inline void d_drop(struct dentry *dentry)
206{
207 spin_lock(&dcache_lock);
208 spin_lock(&dentry->d_lock);
209 __d_drop(dentry);
210 spin_unlock(&dentry->d_lock);
211 spin_unlock(&dcache_lock);
212}
213
214static inline int dname_external(struct dentry *dentry)
215{
216 return dentry->d_name.name != dentry->d_iname;
217}
218
219/*
220 * These are the low-level FS interfaces to the dcache..
221 */
222extern void d_instantiate(struct dentry *, struct inode *);
223extern struct dentry * d_instantiate_unique(struct dentry *, struct inode *);
770bfad8 224extern struct dentry * d_materialise_unique(struct dentry *, struct inode *);
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225extern void d_delete(struct dentry *);
226
227/* allocate/de-allocate */
228extern struct dentry * d_alloc(struct dentry *, const struct qstr *);
229extern struct dentry * d_alloc_anon(struct inode *);
230extern struct dentry * d_splice_alias(struct inode *, struct dentry *);
231extern void shrink_dcache_sb(struct super_block *);
232extern void shrink_dcache_parent(struct dentry *);
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233extern int d_invalidate(struct dentry *);
234
235/* only used at mount-time */
236extern struct dentry * d_alloc_root(struct inode *);
237
238/* <clickety>-<click> the ramfs-type tree */
239extern void d_genocide(struct dentry *);
240
241extern struct dentry *d_find_alias(struct inode *);
242extern void d_prune_aliases(struct inode *);
243
244/* test whether we have any submounts in a subdir tree */
245extern int have_submounts(struct dentry *);
246
247/*
248 * This adds the entry to the hash queues.
249 */
250extern void d_rehash(struct dentry *);
251
252/**
253 * d_add - add dentry to hash queues
254 * @entry: dentry to add
255 * @inode: The inode to attach to this dentry
256 *
257 * This adds the entry to the hash queues and initializes @inode.
258 * The entry was actually filled in earlier during d_alloc().
259 */
260
261static inline void d_add(struct dentry *entry, struct inode *inode)
262{
263 d_instantiate(entry, inode);
264 d_rehash(entry);
265}
266
267/**
268 * d_add_unique - add dentry to hash queues without aliasing
269 * @entry: dentry to add
270 * @inode: The inode to attach to this dentry
271 *
272 * This adds the entry to the hash queues and initializes @inode.
273 * The entry was actually filled in earlier during d_alloc().
274 */
275static inline struct dentry *d_add_unique(struct dentry *entry, struct inode *inode)
276{
277 struct dentry *res;
278
279 res = d_instantiate_unique(entry, inode);
280 d_rehash(res != NULL ? res : entry);
281 return res;
282}
283
284/* used for rename() and baskets */
285extern void d_move(struct dentry *, struct dentry *);
286
287/* appendix may either be NULL or be used for transname suffixes */
288extern struct dentry * d_lookup(struct dentry *, struct qstr *);
289extern struct dentry * __d_lookup(struct dentry *, struct qstr *);
3e7e241f 290extern struct dentry * d_hash_and_lookup(struct dentry *, struct qstr *);
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291
292/* validate "insecure" dentry pointer */
293extern int d_validate(struct dentry *, struct dentry *);
294
295extern char * d_path(struct dentry *, struct vfsmount *, char *, int);
296
297/* Allocation counts.. */
298
299/**
300 * dget, dget_locked - get a reference to a dentry
301 * @dentry: dentry to get a reference to
302 *
303 * Given a dentry or %NULL pointer increment the reference count
304 * if appropriate and return the dentry. A dentry will not be
305 * destroyed when it has references. dget() should never be
306 * called for dentries with zero reference counter. For these cases
307 * (preferably none, functions in dcache.c are sufficient for normal
308 * needs and they take necessary precautions) you should hold dcache_lock
309 * and call dget_locked() instead of dget().
310 */
311
312static inline struct dentry *dget(struct dentry *dentry)
313{
314 if (dentry) {
315 BUG_ON(!atomic_read(&dentry->d_count));
316 atomic_inc(&dentry->d_count);
317 }
318 return dentry;
319}
320
321extern struct dentry * dget_locked(struct dentry *);
322
323/**
324 * d_unhashed - is dentry hashed
325 * @dentry: entry to check
326 *
327 * Returns true if the dentry passed is not currently hashed.
328 */
329
330static inline int d_unhashed(struct dentry *dentry)
331{
332 return (dentry->d_flags & DCACHE_UNHASHED);
333}
334
335static inline struct dentry *dget_parent(struct dentry *dentry)
336{
337 struct dentry *ret;
338
339 spin_lock(&dentry->d_lock);
340 ret = dget(dentry->d_parent);
341 spin_unlock(&dentry->d_lock);
342 return ret;
343}
344
345extern void dput(struct dentry *);
346
347static inline int d_mountpoint(struct dentry *dentry)
348{
349 return dentry->d_mounted;
350}
351
352extern struct vfsmount *lookup_mnt(struct vfsmount *, struct dentry *);
a05964f3 353extern struct vfsmount *__lookup_mnt(struct vfsmount *, struct dentry *, int);
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354extern struct dentry *lookup_create(struct nameidata *nd, int is_dir);
355
356extern int sysctl_vfs_cache_pressure;
357
358#endif /* __KERNEL__ */
359
360#endif /* __LINUX_DCACHE_H */