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Linus Torvalds1da177e2005-04-16 15:20:36 -07001#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>
Linus Torvalds1da177e2005-04-16 15:20:36 -070011
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
Eric Dumazet3f4bb1f2005-09-06 15:18:16 -070090 * so they all fit in a cache line.
Linus Torvalds1da177e2005-04-16 15:20:36 -070091 */
Eric Dumazet3f4bb1f2005-09-06 15:18:16 -070092 struct hlist_node d_hash; /* lookup hash list */
Linus Torvalds1da177e2005-04-16 15:20:36 -070093 struct dentry *d_parent; /* parent directory */
94 struct qstr d_name;
95
96 struct list_head d_lru; /* LRU list */
Eric Dumazet5160ee62006-01-08 01:03:32 -080097 /*
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;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700104 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 */
Marcelo Tosatti47ba87e2006-02-03 03:04:06 -0800110#ifdef CONFIG_PROFILING
Linus Torvalds1da177e2005-04-16 15:20:36 -0700111 struct dcookie_struct *d_cookie; /* cookie, if any */
Marcelo Tosatti47ba87e2006-02-03 03:04:06 -0800112#endif
Linus Torvalds1da177e2005-04-16 15:20:36 -0700113 int d_mounted;
114 unsigned char d_iname[DNAME_INLINE_LEN_MIN]; /* small names */
115};
116
117struct dentry_operations {
118 int (*d_revalidate)(struct dentry *, struct nameidata *);
119 int (*d_hash) (struct dentry *, struct qstr *);
120 int (*d_compare) (struct dentry *, struct qstr *, struct qstr *);
121 int (*d_delete)(struct dentry *);
122 void (*d_release)(struct dentry *);
123 void (*d_iput)(struct dentry *, struct inode *);
124};
125
126/* the dentry parameter passed to d_hash and d_compare is the parent
127 * directory of the entries to be compared. It is used in case these
128 * functions need any directory specific information for determining
129 * equivalency classes. Using the dentry itself might not work, as it
130 * might be a negative dentry which has no information associated with
131 * it */
132
133/*
134locking rules:
135 big lock dcache_lock d_lock may block
136d_revalidate: no no no yes
137d_hash no no no yes
138d_compare: no yes yes no
139d_delete: no yes no no
140d_release: no no no yes
141d_iput: no no no yes
142 */
143
144/* d_flags entries */
145#define DCACHE_AUTOFS_PENDING 0x0001 /* autofs: "under construction" */
146#define DCACHE_NFSFS_RENAMED 0x0002 /* this dentry has been "silly
147 * renamed" and has to be
148 * deleted on the last dput()
149 */
150#define DCACHE_DISCONNECTED 0x0004
151 /* This dentry is possibly not currently connected to the dcache tree,
152 * in which case its parent will either be itself, or will have this
153 * flag as well. nfsd will not use a dentry with this bit set, but will
154 * first endeavour to clear the bit either by discovering that it is
155 * connected, or by performing lookup operations. Any filesystem which
156 * supports nfsd_operations MUST have a lookup function which, if it finds
157 * a directory inode with a DCACHE_DISCONNECTED dentry, will d_move
158 * that dentry into place and return that dentry rather than the passed one,
159 * typically using d_splice_alias.
160 */
161
162#define DCACHE_REFERENCED 0x0008 /* Recently used, don't discard. */
163#define DCACHE_UNHASHED 0x0010
164
165extern spinlock_t dcache_lock;
166
167/**
168 * d_drop - drop a dentry
169 * @dentry: dentry to drop
170 *
171 * d_drop() unhashes the entry from the parent dentry hashes, so that it won't
172 * be found through a VFS lookup any more. Note that this is different from
173 * deleting the dentry - d_delete will try to mark the dentry negative if
174 * possible, giving a successful _negative_ lookup, while d_drop will
175 * just make the cache lookup fail.
176 *
177 * d_drop() is used mainly for stuff that wants to invalidate a dentry for some
178 * reason (NFS timeouts or autofs deletes).
179 *
180 * __d_drop requires dentry->d_lock.
181 */
182
183static inline void __d_drop(struct dentry *dentry)
184{
185 if (!(dentry->d_flags & DCACHE_UNHASHED)) {
186 dentry->d_flags |= DCACHE_UNHASHED;
187 hlist_del_rcu(&dentry->d_hash);
188 }
189}
190
191static inline void d_drop(struct dentry *dentry)
192{
193 spin_lock(&dcache_lock);
194 spin_lock(&dentry->d_lock);
195 __d_drop(dentry);
196 spin_unlock(&dentry->d_lock);
197 spin_unlock(&dcache_lock);
198}
199
200static inline int dname_external(struct dentry *dentry)
201{
202 return dentry->d_name.name != dentry->d_iname;
203}
204
205/*
206 * These are the low-level FS interfaces to the dcache..
207 */
208extern void d_instantiate(struct dentry *, struct inode *);
209extern struct dentry * d_instantiate_unique(struct dentry *, struct inode *);
210extern void d_delete(struct dentry *);
211
212/* allocate/de-allocate */
213extern struct dentry * d_alloc(struct dentry *, const struct qstr *);
214extern struct dentry * d_alloc_anon(struct inode *);
215extern struct dentry * d_splice_alias(struct inode *, struct dentry *);
216extern void shrink_dcache_sb(struct super_block *);
217extern void shrink_dcache_parent(struct dentry *);
218extern void shrink_dcache_anon(struct hlist_head *);
219extern int d_invalidate(struct dentry *);
220
221/* only used at mount-time */
222extern struct dentry * d_alloc_root(struct inode *);
223
224/* <clickety>-<click> the ramfs-type tree */
225extern void d_genocide(struct dentry *);
226
227extern struct dentry *d_find_alias(struct inode *);
228extern void d_prune_aliases(struct inode *);
229
230/* test whether we have any submounts in a subdir tree */
231extern int have_submounts(struct dentry *);
232
233/*
234 * This adds the entry to the hash queues.
235 */
236extern void d_rehash(struct dentry *);
237
238/**
239 * d_add - add dentry to hash queues
240 * @entry: dentry to add
241 * @inode: The inode to attach to this dentry
242 *
243 * This adds the entry to the hash queues and initializes @inode.
244 * The entry was actually filled in earlier during d_alloc().
245 */
246
247static inline void d_add(struct dentry *entry, struct inode *inode)
248{
249 d_instantiate(entry, inode);
250 d_rehash(entry);
251}
252
253/**
254 * d_add_unique - add dentry to hash queues without aliasing
255 * @entry: dentry to add
256 * @inode: The inode to attach to this dentry
257 *
258 * This adds the entry to the hash queues and initializes @inode.
259 * The entry was actually filled in earlier during d_alloc().
260 */
261static inline struct dentry *d_add_unique(struct dentry *entry, struct inode *inode)
262{
263 struct dentry *res;
264
265 res = d_instantiate_unique(entry, inode);
266 d_rehash(res != NULL ? res : entry);
267 return res;
268}
269
270/* used for rename() and baskets */
271extern void d_move(struct dentry *, struct dentry *);
272
273/* appendix may either be NULL or be used for transname suffixes */
274extern struct dentry * d_lookup(struct dentry *, struct qstr *);
275extern struct dentry * __d_lookup(struct dentry *, struct qstr *);
276
277/* validate "insecure" dentry pointer */
278extern int d_validate(struct dentry *, struct dentry *);
279
280extern char * d_path(struct dentry *, struct vfsmount *, char *, int);
281
282/* Allocation counts.. */
283
284/**
285 * dget, dget_locked - get a reference to a dentry
286 * @dentry: dentry to get a reference to
287 *
288 * Given a dentry or %NULL pointer increment the reference count
289 * if appropriate and return the dentry. A dentry will not be
290 * destroyed when it has references. dget() should never be
291 * called for dentries with zero reference counter. For these cases
292 * (preferably none, functions in dcache.c are sufficient for normal
293 * needs and they take necessary precautions) you should hold dcache_lock
294 * and call dget_locked() instead of dget().
295 */
296
297static inline struct dentry *dget(struct dentry *dentry)
298{
299 if (dentry) {
300 BUG_ON(!atomic_read(&dentry->d_count));
301 atomic_inc(&dentry->d_count);
302 }
303 return dentry;
304}
305
306extern struct dentry * dget_locked(struct dentry *);
307
308/**
309 * d_unhashed - is dentry hashed
310 * @dentry: entry to check
311 *
312 * Returns true if the dentry passed is not currently hashed.
313 */
314
315static inline int d_unhashed(struct dentry *dentry)
316{
317 return (dentry->d_flags & DCACHE_UNHASHED);
318}
319
320static inline struct dentry *dget_parent(struct dentry *dentry)
321{
322 struct dentry *ret;
323
324 spin_lock(&dentry->d_lock);
325 ret = dget(dentry->d_parent);
326 spin_unlock(&dentry->d_lock);
327 return ret;
328}
329
330extern void dput(struct dentry *);
331
332static inline int d_mountpoint(struct dentry *dentry)
333{
334 return dentry->d_mounted;
335}
336
337extern struct vfsmount *lookup_mnt(struct vfsmount *, struct dentry *);
Ram Paia05964f2005-11-07 17:20:17 -0500338extern struct vfsmount *__lookup_mnt(struct vfsmount *, struct dentry *, int);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700339extern struct dentry *lookup_create(struct nameidata *nd, int is_dir);
340
341extern int sysctl_vfs_cache_pressure;
342
343#endif /* __KERNEL__ */
344
345#endif /* __LINUX_DCACHE_H */