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