1 #ifndef __LINUX_DCACHE_H
2 #define __LINUX_DCACHE_H
3
4 #include <asm/atomic.h>
5 #include <linux/list.h>
6 #include <linux/rculist.h>
7 #include <linux/spinlock.h>
8 #include <linux/cache.h>
9 #include <linux/rcupdate.h>
10
11 struct nameidata;
12 struct path;
13 struct 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 */
33 struct qstr {
34 unsigned int hash;
35 unsigned int len;
36 const unsigned char *name;
37 };
38
39 struct 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 };
46 extern 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 */
53 static inline unsigned long
54 partial_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 */
63 static 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. */
69 static inline unsigned int
70 full_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
78 /*
79 * Try to keep struct dentry aligned on 64 byte cachelines (this will
80 * give reasonable cacheline footprint with larger lines without the
81 * large memory footprint increase).
82 */
83 #ifdef CONFIG_64BIT
84 #define DNAME_INLINE_LEN_MIN 32 /* 192 bytes */
85 #else
86 #define DNAME_INLINE_LEN_MIN 40 /* 128 bytes */
87 #endif
88
89 struct dentry {
90 atomic_t d_count;
91 unsigned int d_flags; /* protected by d_lock */
92 spinlock_t d_lock; /* per dentry lock */
93 int d_mounted;
94 struct inode *d_inode; /* Where the name belongs to - NULL is
95 * negative */
96 /*
97 * The next three fields are touched by __d_lookup. Place them here
98 * so they all fit in a cache line.
99 */
100 struct hlist_node d_hash; /* lookup hash list */
101 struct dentry *d_parent; /* parent directory */
102 struct qstr d_name;
103
104 struct list_head d_lru; /* LRU list */
105 /*
106 * d_child and d_rcu can share memory
107 */
108 union {
109 struct list_head d_child; /* child of parent list */
110 struct rcu_head d_rcu;
111 } d_u;
112 struct list_head d_subdirs; /* our children */
113 struct list_head d_alias; /* inode alias list */
114 unsigned long d_time; /* used by d_revalidate */
115 const struct dentry_operations *d_op;
116 struct super_block *d_sb; /* The root of the dentry tree */
117 void *d_fsdata; /* fs-specific data */
118
119 unsigned char d_iname[DNAME_INLINE_LEN_MIN]; /* small names */
120 };
121
122 /*
123 * dentry->d_lock spinlock nesting subclasses:
124 *
125 * 0: normal
126 * 1: nested
127 */
128 enum dentry_d_lock_class
129 {
130 DENTRY_D_LOCK_NORMAL, /* implicitly used by plain spin_lock() APIs. */
131 DENTRY_D_LOCK_NESTED
132 };
133
134 struct dentry_operations {
135 int (*d_revalidate)(struct dentry *, struct nameidata *);
136 int (*d_hash) (struct dentry *, struct qstr *);
137 int (*d_compare) (struct dentry *, struct qstr *, struct qstr *);
138 int (*d_delete)(struct dentry *);
139 void (*d_release)(struct dentry *);
140 void (*d_iput)(struct dentry *, struct inode *);
141 char *(*d_dname)(struct dentry *, char *, int);
142 };
143
144 /* the dentry parameter passed to d_hash and d_compare is the parent
145 * directory of the entries to be compared. It is used in case these
146 * functions need any directory specific information for determining
147 * equivalency classes. Using the dentry itself might not work, as it
148 * might be a negative dentry which has no information associated with
149 * it */
150
151 /*
152 locking rules:
153 big lock dcache_lock d_lock may block
154 d_revalidate: no no no yes
155 d_hash no no no yes
156 d_compare: no yes yes no
157 d_delete: no yes no no
158 d_release: no no no yes
159 d_iput: no no no yes
160 */
161
162 /* d_flags entries */
163 #define DCACHE_AUTOFS_PENDING 0x0001 /* autofs: "under construction" */
164 #define DCACHE_NFSFS_RENAMED 0x0002 /* this dentry has been "silly
165 * renamed" and has to be
166 * deleted on the last dput()
167 */
168 #define DCACHE_DISCONNECTED 0x0004
169 /* This dentry is possibly not currently connected to the dcache tree,
170 * in which case its parent will either be itself, or will have this
171 * flag as well. nfsd will not use a dentry with this bit set, but will
172 * first endeavour to clear the bit either by discovering that it is
173 * connected, or by performing lookup operations. Any filesystem which
174 * supports nfsd_operations MUST have a lookup function which, if it finds
175 * a directory inode with a DCACHE_DISCONNECTED dentry, will d_move
176 * that dentry into place and return that dentry rather than the passed one,
177 * typically using d_splice_alias.
178 */
179
180 #define DCACHE_REFERENCED 0x0008 /* Recently used, don't discard. */
181 #define DCACHE_UNHASHED 0x0010
182
183 #define DCACHE_INOTIFY_PARENT_WATCHED 0x0020 /* Parent inode is watched by inotify */
184
185 #define DCACHE_COOKIE 0x0040 /* For use by dcookie subsystem */
186
187 #define DCACHE_FSNOTIFY_PARENT_WATCHED 0x0080 /* Parent inode is watched by some fsnotify listener */
188
189 extern spinlock_t dcache_lock;
190 extern seqlock_t rename_lock;
191
192 /**
193 * d_drop - drop a dentry
194 * @dentry: dentry to drop
195 *
196 * d_drop() unhashes the entry from the parent dentry hashes, so that it won't
197 * be found through a VFS lookup any more. Note that this is different from
198 * deleting the dentry - d_delete will try to mark the dentry negative if
199 * possible, giving a successful _negative_ lookup, while d_drop will
200 * just make the cache lookup fail.
201 *
202 * d_drop() is used mainly for stuff that wants to invalidate a dentry for some
203 * reason (NFS timeouts or autofs deletes).
204 *
205 * __d_drop requires dentry->d_lock.
206 */
207
208 static inline void __d_drop(struct dentry *dentry)
209 {
210 if (!(dentry->d_flags & DCACHE_UNHASHED)) {
211 dentry->d_flags |= DCACHE_UNHASHED;
212 hlist_del_rcu(&dentry->d_hash);
213 }
214 }
215
216 static inline void d_drop(struct dentry *dentry)
217 {
218 spin_lock(&dcache_lock);
219 spin_lock(&dentry->d_lock);
220 __d_drop(dentry);
221 spin_unlock(&dentry->d_lock);
222 spin_unlock(&dcache_lock);
223 }
224
225 static inline int dname_external(struct dentry *dentry)
226 {
227 return dentry->d_name.name != dentry->d_iname;
228 }
229
230 /*
231 * These are the low-level FS interfaces to the dcache..
232 */
233 extern void d_instantiate(struct dentry *, struct inode *);
234 extern struct dentry * d_instantiate_unique(struct dentry *, struct inode *);
235 extern struct dentry * d_materialise_unique(struct dentry *, struct inode *);
236 extern void d_delete(struct dentry *);
237
238 /* allocate/de-allocate */
239 extern struct dentry * d_alloc(struct dentry *, const struct qstr *);
240 extern struct dentry * d_splice_alias(struct inode *, struct dentry *);
241 extern struct dentry * d_add_ci(struct dentry *, struct inode *, struct qstr *);
242 extern struct dentry * d_obtain_alias(struct inode *);
243 extern void shrink_dcache_sb(struct super_block *);
244 extern void shrink_dcache_parent(struct dentry *);
245 extern void shrink_dcache_for_umount(struct super_block *);
246 extern int d_invalidate(struct dentry *);
247
248 /* only used at mount-time */
249 extern struct dentry * d_alloc_root(struct inode *);
250
251 /* <clickety>-<click> the ramfs-type tree */
252 extern void d_genocide(struct dentry *);
253
254 extern struct dentry *d_find_alias(struct inode *);
255 extern void d_prune_aliases(struct inode *);
256
257 /* test whether we have any submounts in a subdir tree */
258 extern int have_submounts(struct dentry *);
259
260 /*
261 * This adds the entry to the hash queues.
262 */
263 extern void d_rehash(struct dentry *);
264
265 /**
266 * d_add - add dentry to hash queues
267 * @entry: dentry to add
268 * @inode: The inode to attach to this dentry
269 *
270 * This adds the entry to the hash queues and initializes @inode.
271 * The entry was actually filled in earlier during d_alloc().
272 */
273
274 static inline void d_add(struct dentry *entry, struct inode *inode)
275 {
276 d_instantiate(entry, inode);
277 d_rehash(entry);
278 }
279
280 /**
281 * d_add_unique - add dentry to hash queues without aliasing
282 * @entry: dentry to add
283 * @inode: The inode to attach to this dentry
284 *
285 * This adds the entry to the hash queues and initializes @inode.
286 * The entry was actually filled in earlier during d_alloc().
287 */
288 static inline struct dentry *d_add_unique(struct dentry *entry, struct inode *inode)
289 {
290 struct dentry *res;
291
292 res = d_instantiate_unique(entry, inode);
293 d_rehash(res != NULL ? res : entry);
294 return res;
295 }
296
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 *);
300
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_lookup(struct dentry *, struct qstr *);
304 extern struct dentry * d_hash_and_lookup(struct dentry *, struct qstr *);
305
306 /* validate "insecure" dentry pointer */
307 extern int d_validate(struct dentry *, struct dentry *);
308
309 /*
310 * helper function for dentry_operations.d_dname() members
311 */
312 extern char *dynamic_dname(struct dentry *, char *, int, const char *, ...);
313
314 extern char *__d_path(const struct path *path, struct path *root, char *, int);
315 extern char *d_path(const struct path *, char *, int);
316 extern char *dentry_path(struct dentry *, char *, int);
317
318 /* Allocation counts.. */
319
320 /**
321 * dget, dget_locked - get a reference to a dentry
322 * @dentry: dentry to get a reference to
323 *
324 * Given a dentry or %NULL pointer increment the reference count
325 * if appropriate and return the dentry. A dentry will not be
326 * destroyed when it has references. dget() should never be
327 * called for dentries with zero reference counter. For these cases
328 * (preferably none, functions in dcache.c are sufficient for normal
329 * needs and they take necessary precautions) you should hold dcache_lock
330 * and call dget_locked() instead of dget().
331 */
332
333 static inline struct dentry *dget(struct dentry *dentry)
334 {
335 if (dentry) {
336 BUG_ON(!atomic_read(&dentry->d_count));
337 atomic_inc(&dentry->d_count);
338 }
339 return dentry;
340 }
341
342 extern struct dentry * dget_locked(struct dentry *);
343
344 /**
345 * d_unhashed - is dentry hashed
346 * @dentry: entry to check
347 *
348 * Returns true if the dentry passed is not currently hashed.
349 */
350
351 static inline int d_unhashed(struct dentry *dentry)
352 {
353 return (dentry->d_flags & DCACHE_UNHASHED);
354 }
355
356 static inline int d_unlinked(struct dentry *dentry)
357 {
358 return d_unhashed(dentry) && !IS_ROOT(dentry);
359 }
360
361 static inline struct dentry *dget_parent(struct dentry *dentry)
362 {
363 struct dentry *ret;
364
365 spin_lock(&dentry->d_lock);
366 ret = dget(dentry->d_parent);
367 spin_unlock(&dentry->d_lock);
368 return ret;
369 }
370
371 extern void dput(struct dentry *);
372
373 static inline int d_mountpoint(struct dentry *dentry)
374 {
375 return dentry->d_mounted;
376 }
377
378 extern struct vfsmount *lookup_mnt(struct path *);
379 extern struct dentry *lookup_create(struct nameidata *nd, int is_dir);
380
381 extern int sysctl_vfs_cache_pressure;
382
383 #endif /* __LINUX_DCACHE_H */
384
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