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
partial_name_hash(unsigned long c,unsigned long prevhash)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 */
end_name_hash(unsigned long hash)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
full_name_hash(const unsigned char * name,unsigned int len)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 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 */
184
185 #define DCACHE_COOKIE 0x0040 /* For use by dcookie subsystem */
186
187 extern spinlock_t dcache_lock;
188 extern seqlock_t rename_lock;
189
190 /**
191 * d_drop - drop a dentry
192 * @dentry: dentry to drop
193 *
194 * d_drop() unhashes the entry from the parent dentry hashes, so that it won't
195 * be found through a VFS lookup any more. Note that this is different from
196 * deleting the dentry - d_delete will try to mark the dentry negative if
197 * possible, giving a successful _negative_ lookup, while d_drop will
198 * just make the cache lookup fail.
199 *
200 * d_drop() is used mainly for stuff that wants to invalidate a dentry for some
201 * reason (NFS timeouts or autofs deletes).
202 *
203 * __d_drop requires dentry->d_lock.
204 */
205
__d_drop(struct dentry * dentry)206 static inline void __d_drop(struct dentry *dentry)
207 {
208 if (!(dentry->d_flags & DCACHE_UNHASHED)) {
209 dentry->d_flags |= DCACHE_UNHASHED;
210 hlist_del_rcu(&dentry->d_hash);
211 }
212 }
213
d_drop(struct dentry * dentry)214 static inline void d_drop(struct dentry *dentry)
215 {
216 spin_lock(&dcache_lock);
217 spin_lock(&dentry->d_lock);
218 __d_drop(dentry);
219 spin_unlock(&dentry->d_lock);
220 spin_unlock(&dcache_lock);
221 }
222
dname_external(struct dentry * dentry)223 static inline int dname_external(struct dentry *dentry)
224 {
225 return dentry->d_name.name != dentry->d_iname;
226 }
227
228 /*
229 * These are the low-level FS interfaces to the dcache..
230 */
231 extern void d_instantiate(struct dentry *, struct inode *);
232 extern struct dentry * d_instantiate_unique(struct dentry *, struct inode *);
233 extern struct dentry * d_materialise_unique(struct dentry *, struct inode *);
234 extern void d_delete(struct dentry *);
235
236 /* allocate/de-allocate */
237 extern struct dentry * d_alloc(struct dentry *, const struct qstr *);
238 extern struct dentry * d_splice_alias(struct inode *, struct dentry *);
239 extern struct dentry * d_add_ci(struct dentry *, struct inode *, struct qstr *);
240 extern struct dentry * d_obtain_alias(struct inode *);
241 extern void shrink_dcache_sb(struct super_block *);
242 extern void shrink_dcache_parent(struct dentry *);
243 extern void shrink_dcache_for_umount(struct super_block *);
244 extern int d_invalidate(struct dentry *);
245
246 /* only used at mount-time */
247 extern struct dentry * d_alloc_root(struct inode *);
248
249 /* <clickety>-<click> the ramfs-type tree */
250 extern void d_genocide(struct dentry *);
251
252 extern struct dentry *d_find_alias(struct inode *);
253 extern void d_prune_aliases(struct inode *);
254
255 /* test whether we have any submounts in a subdir tree */
256 extern int have_submounts(struct dentry *);
257
258 /*
259 * This adds the entry to the hash queues.
260 */
261 extern void d_rehash(struct dentry *);
262
263 /**
264 * d_add - add dentry to hash queues
265 * @entry: dentry to add
266 * @inode: The inode to attach to this dentry
267 *
268 * This adds the entry to the hash queues and initializes @inode.
269 * The entry was actually filled in earlier during d_alloc().
270 */
271
d_add(struct dentry * entry,struct inode * inode)272 static inline void d_add(struct dentry *entry, struct inode *inode)
273 {
274 d_instantiate(entry, inode);
275 d_rehash(entry);
276 }
277
278 /**
279 * d_add_unique - add dentry to hash queues without aliasing
280 * @entry: dentry to add
281 * @inode: The inode to attach to this dentry
282 *
283 * This adds the entry to the hash queues and initializes @inode.
284 * The entry was actually filled in earlier during d_alloc().
285 */
d_add_unique(struct dentry * entry,struct inode * inode)286 static inline struct dentry *d_add_unique(struct dentry *entry, struct inode *inode)
287 {
288 struct dentry *res;
289
290 res = d_instantiate_unique(entry, inode);
291 d_rehash(res != NULL ? res : entry);
292 return res;
293 }
294
295 /* used for rename() and baskets */
296 extern void d_move(struct dentry *, struct dentry *);
297 extern struct dentry *d_ancestor(struct dentry *, struct dentry *);
298
299 /* appendix may either be NULL or be used for transname suffixes */
300 extern struct dentry * d_lookup(struct dentry *, struct qstr *);
301 extern struct dentry * __d_lookup(struct dentry *, struct qstr *);
302 extern struct dentry * d_hash_and_lookup(struct dentry *, struct qstr *);
303
304 /* validate "insecure" dentry pointer */
305 extern int d_validate(struct dentry *, struct dentry *);
306
307 /*
308 * helper function for dentry_operations.d_dname() members
309 */
310 extern char *dynamic_dname(struct dentry *, char *, int, const char *, ...);
311
312 extern char *__d_path(const struct path *path, struct path *root, char *, int);
313 extern char *d_path(const struct path *, char *, int);
314 extern char *dentry_path(struct dentry *, char *, int);
315
316 /* Allocation counts.. */
317
318 /**
319 * dget, dget_locked - get a reference to a dentry
320 * @dentry: dentry to get a reference to
321 *
322 * Given a dentry or %NULL pointer increment the reference count
323 * if appropriate and return the dentry. A dentry will not be
324 * destroyed when it has references. dget() should never be
325 * called for dentries with zero reference counter. For these cases
326 * (preferably none, functions in dcache.c are sufficient for normal
327 * needs and they take necessary precautions) you should hold dcache_lock
328 * and call dget_locked() instead of dget().
329 */
330
dget(struct dentry * dentry)331 static inline struct dentry *dget(struct dentry *dentry)
332 {
333 if (dentry) {
334 BUG_ON(!atomic_read(&dentry->d_count));
335 atomic_inc(&dentry->d_count);
336 }
337 return dentry;
338 }
339
340 extern struct dentry * dget_locked(struct dentry *);
341
342 /**
343 * d_unhashed - is dentry hashed
344 * @dentry: entry to check
345 *
346 * Returns true if the dentry passed is not currently hashed.
347 */
348
d_unhashed(struct dentry * dentry)349 static inline int d_unhashed(struct dentry *dentry)
350 {
351 return (dentry->d_flags & DCACHE_UNHASHED);
352 }
353
dget_parent(struct dentry * dentry)354 static inline struct dentry *dget_parent(struct dentry *dentry)
355 {
356 struct dentry *ret;
357
358 spin_lock(&dentry->d_lock);
359 ret = dget(dentry->d_parent);
360 spin_unlock(&dentry->d_lock);
361 return ret;
362 }
363
364 extern void dput(struct dentry *);
365
d_mountpoint(struct dentry * dentry)366 static inline int d_mountpoint(struct dentry *dentry)
367 {
368 return dentry->d_mounted;
369 }
370
371 extern struct vfsmount *lookup_mnt(struct vfsmount *, struct dentry *);
372 extern struct dentry *lookup_create(struct nameidata *nd, int is_dir);
373
374 extern int sysctl_vfs_cache_pressure;
375
376 #endif /* __LINUX_DCACHE_H */
377