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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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