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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/rculist_bl.h>
8 #include <linux/spinlock.h>
9 #include <linux/seqlock.h>
10 #include <linux/cache.h>
11 #include <linux/rcupdate.h>
12
13 struct nameidata;
14 struct path;
15 struct vfsmount;
16
17 /*
18 * linux/include/linux/dcache.h
19 *
20 * Dirent cache data structures
21 *
22 * (C) Copyright 1997 Thomas Schoebel-Theuer,
23 * with heavy changes by Linus Torvalds
24 */
25
26 #define IS_ROOT(x) ((x) == (x)->d_parent)
27
28 /*
29 * "quick string" -- eases parameter passing, but more importantly
30 * saves "metadata" about the string (ie length and the hash).
31 *
32 * hash comes first so it snuggles against d_parent in the
33 * dentry.
34 */
35 struct qstr {
36 unsigned int hash;
37 unsigned int len;
38 const unsigned char *name;
39 };
40
41 struct dentry_stat_t {
42 int nr_dentry;
43 int nr_unused;
44 int age_limit; /* age in seconds */
45 int want_pages; /* pages requested by system */
46 int dummy[2];
47 };
48 extern struct dentry_stat_t dentry_stat;
49
50 /*
51 * Compare 2 name strings, return 0 if they match, otherwise non-zero.
52 * The strings are both count bytes long, and count is non-zero.
53 */
54 static inline int dentry_cmp(const unsigned char *cs, size_t scount,
55 const unsigned char *ct, size_t tcount)
56 {
57 int ret;
58 if (scount != tcount)
59 return 1;
60 do {
61 ret = (*cs != *ct);
62 if (ret)
63 break;
64 cs++;
65 ct++;
66 tcount--;
67 } while (tcount);
68 return ret;
69 }
70
71 /* Name hashing routines. Initial hash value */
72 /* Hash courtesy of the R5 hash in reiserfs modulo sign bits */
73 #define init_name_hash() 0
74
75 /* partial hash update function. Assume roughly 4 bits per character */
76 static inline unsigned long
77 partial_name_hash(unsigned long c, unsigned long prevhash)
78 {
79 return (prevhash + (c << 4) + (c >> 4)) * 11;
80 }
81
82 /*
83 * Finally: cut down the number of bits to a int value (and try to avoid
84 * losing bits)
85 */
86 static inline unsigned long end_name_hash(unsigned long hash)
87 {
88 return (unsigned int) hash;
89 }
90
91 /* Compute the hash for a name string. */
92 static inline unsigned int
93 full_name_hash(const unsigned char *name, unsigned int len)
94 {
95 unsigned long hash = init_name_hash();
96 while (len--)
97 hash = partial_name_hash(*name++, hash);
98 return end_name_hash(hash);
99 }
100
101 /*
102 * Try to keep struct dentry aligned on 64 byte cachelines (this will
103 * give reasonable cacheline footprint with larger lines without the
104 * large memory footprint increase).
105 */
106 #ifdef CONFIG_64BIT
107 # define DNAME_INLINE_LEN 32 /* 192 bytes */
108 #else
109 # ifdef CONFIG_SMP
110 # define DNAME_INLINE_LEN 36 /* 128 bytes */
111 # else
112 # define DNAME_INLINE_LEN 40 /* 128 bytes */
113 # endif
114 #endif
115
116 struct dentry {
117 /* RCU lookup touched fields */
118 unsigned int d_flags; /* protected by d_lock */
119 seqcount_t d_seq; /* per dentry seqlock */
120 struct hlist_bl_node d_hash; /* lookup hash list */
121 struct dentry *d_parent; /* parent directory */
122 struct qstr d_name;
123 struct inode *d_inode; /* Where the name belongs to - NULL is
124 * negative */
125 unsigned char d_iname[DNAME_INLINE_LEN]; /* small names */
126
127 /* Ref lookup also touches following */
128 unsigned int d_count; /* protected by d_lock */
129 spinlock_t d_lock; /* per dentry lock */
130 const struct dentry_operations *d_op;
131 struct super_block *d_sb; /* The root of the dentry tree */
132 unsigned long d_time; /* used by d_revalidate */
133 void *d_fsdata; /* fs-specific data */
134
135 struct list_head d_lru; /* LRU list */
136 /*
137 * d_child and d_rcu can share memory
138 */
139 union {
140 struct list_head d_child; /* child of parent list */
141 struct rcu_head d_rcu;
142 } d_u;
143 struct list_head d_subdirs; /* our children */
144 struct list_head d_alias; /* inode alias list */
145 };
146
147 /*
148 * dentry->d_lock spinlock nesting subclasses:
149 *
150 * 0: normal
151 * 1: nested
152 */
153 enum dentry_d_lock_class
154 {
155 DENTRY_D_LOCK_NORMAL, /* implicitly used by plain spin_lock() APIs. */
156 DENTRY_D_LOCK_NESTED
157 };
158
159 struct dentry_operations {
160 int (*d_revalidate)(struct dentry *, struct nameidata *);
161 int (*d_hash)(const struct dentry *, const struct inode *,
162 struct qstr *);
163 int (*d_compare)(const struct dentry *, const struct inode *,
164 const struct dentry *, const struct inode *,
165 unsigned int, const char *, const struct qstr *);
166 int (*d_delete)(const struct dentry *);
167 void (*d_release)(struct dentry *);
168 void (*d_iput)(struct dentry *, struct inode *);
169 char *(*d_dname)(struct dentry *, char *, int);
170 struct vfsmount *(*d_automount)(struct path *);
171 int (*d_manage)(struct dentry *, bool, bool);
172 } ____cacheline_aligned;
173
174 /*
175 * Locking rules for dentry_operations callbacks are to be found in
176 * Documentation/filesystems/Locking. Keep it updated!
177 *
178 * FUrther descriptions are found in Documentation/filesystems/vfs.txt.
179 * Keep it updated too!
180 */
181
182 /* d_flags entries */
183 #define DCACHE_AUTOFS_PENDING 0x0001 /* autofs: "under construction" */
184 #define DCACHE_NFSFS_RENAMED 0x0002
185 /* this dentry has been "silly renamed" and has to be deleted on the last
186 * dput() */
187
188 #define DCACHE_DISCONNECTED 0x0004
189 /* This dentry is possibly not currently connected to the dcache tree, in
190 * which case its parent will either be itself, or will have this flag as
191 * well. nfsd will not use a dentry with this bit set, but will first
192 * endeavour to clear the bit either by discovering that it is connected,
193 * or by performing lookup operations. Any filesystem which supports
194 * nfsd_operations MUST have a lookup function which, if it finds a
195 * directory inode with a DCACHE_DISCONNECTED dentry, will d_move that
196 * dentry into place and return that dentry rather than the passed one,
197 * typically using d_splice_alias. */
198
199 #define DCACHE_REFERENCED 0x0008 /* Recently used, don't discard. */
200 #define DCACHE_UNHASHED 0x0010
201 #define DCACHE_INOTIFY_PARENT_WATCHED 0x0020
202 /* Parent inode is watched by inotify */
203
204 #define DCACHE_COOKIE 0x0040 /* For use by dcookie subsystem */
205 #define DCACHE_FSNOTIFY_PARENT_WATCHED 0x0080
206 /* Parent inode is watched by some fsnotify listener */
207
208 #define DCACHE_CANT_MOUNT 0x0100
209 #define DCACHE_GENOCIDE 0x0200
210
211 #define DCACHE_OP_HASH 0x1000
212 #define DCACHE_OP_COMPARE 0x2000
213 #define DCACHE_OP_REVALIDATE 0x4000
214 #define DCACHE_OP_DELETE 0x8000
215
216 #define DCACHE_MOUNTED 0x10000 /* is a mountpoint */
217 #define DCACHE_NEED_AUTOMOUNT 0x20000 /* handle automount on this dir */
218 #define DCACHE_MANAGE_TRANSIT 0x40000 /* manage transit from this dirent */
219 #define DCACHE_MANAGED_DENTRY \
220 (DCACHE_MOUNTED|DCACHE_NEED_AUTOMOUNT|DCACHE_MANAGE_TRANSIT)
221
222 extern seqlock_t rename_lock;
223
224 static inline int dname_external(struct dentry *dentry)
225 {
226 return dentry->d_name.name != dentry->d_iname;
227 }
228
229 /*
230 * These are the low-level FS interfaces to the dcache..
231 */
232 extern void d_instantiate(struct dentry *, struct inode *);
233 extern struct dentry * d_instantiate_unique(struct dentry *, struct inode *);
234 extern struct dentry * d_materialise_unique(struct dentry *, struct inode *);
235 extern void __d_drop(struct dentry *dentry);
236 extern void d_drop(struct dentry *dentry);
237 extern void d_delete(struct dentry *);
238 extern void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op);
239
240 /* allocate/de-allocate */
241 extern struct dentry * d_alloc(struct dentry *, const struct qstr *);
242 extern struct dentry * d_alloc_pseudo(struct super_block *, const struct qstr *);
243 extern struct dentry * d_splice_alias(struct inode *, struct dentry *);
244 extern struct dentry * d_add_ci(struct dentry *, struct inode *, struct qstr *);
245 extern struct dentry * d_obtain_alias(struct inode *);
246 extern void shrink_dcache_sb(struct super_block *);
247 extern void shrink_dcache_parent(struct dentry *);
248 extern void shrink_dcache_for_umount(struct super_block *);
249 extern int d_invalidate(struct dentry *);
250
251 /* only used at mount-time */
252 extern struct dentry * d_alloc_root(struct inode *);
253
254 /* <clickety>-<click> the ramfs-type tree */
255 extern void d_genocide(struct dentry *);
256
257 extern struct dentry *d_find_alias(struct inode *);
258 extern void d_prune_aliases(struct inode *);
259
260 /* test whether we have any submounts in a subdir tree */
261 extern int have_submounts(struct dentry *);
262
263 /*
264 * This adds the entry to the hash queues.
265 */
266 extern void d_rehash(struct dentry *);
267
268 /**
269 * d_add - add dentry to hash queues
270 * @entry: dentry to add
271 * @inode: The inode to attach to this dentry
272 *
273 * This adds the entry to the hash queues and initializes @inode.
274 * The entry was actually filled in earlier during d_alloc().
275 */
276
277 static inline void d_add(struct dentry *entry, struct inode *inode)
278 {
279 d_instantiate(entry, inode);
280 d_rehash(entry);
281 }
282
283 /**
284 * d_add_unique - add dentry to hash queues without aliasing
285 * @entry: dentry to add
286 * @inode: The inode to attach to this dentry
287 *
288 * This adds the entry to the hash queues and initializes @inode.
289 * The entry was actually filled in earlier during d_alloc().
290 */
291 static inline struct dentry *d_add_unique(struct dentry *entry, struct inode *inode)
292 {
293 struct dentry *res;
294
295 res = d_instantiate_unique(entry, inode);
296 d_rehash(res != NULL ? res : entry);
297 return res;
298 }
299
300 extern void dentry_update_name_case(struct dentry *, struct qstr *);
301
302 /* used for rename() and baskets */
303 extern void d_move(struct dentry *, struct dentry *);
304 extern struct dentry *d_ancestor(struct dentry *, struct dentry *);
305
306 /* appendix may either be NULL or be used for transname suffixes */
307 extern struct dentry *d_lookup(struct dentry *, struct qstr *);
308 extern struct dentry *d_hash_and_lookup(struct dentry *, struct qstr *);
309 extern struct dentry *__d_lookup(struct dentry *, struct qstr *);
310 extern struct dentry *__d_lookup_rcu(struct dentry *parent, struct qstr *name,
311 unsigned *seq, struct inode **inode);
312
313 /**
314 * __d_rcu_to_refcount - take a refcount on dentry if sequence check is ok
315 * @dentry: dentry to take a ref on
316 * @seq: seqcount to verify against
317 * Returns: 0 on failure, else 1.
318 *
319 * __d_rcu_to_refcount operates on a dentry,seq pair that was returned
320 * by __d_lookup_rcu, to get a reference on an rcu-walk dentry.
321 */
322 static inline int __d_rcu_to_refcount(struct dentry *dentry, unsigned seq)
323 {
324 int ret = 0;
325
326 assert_spin_locked(&dentry->d_lock);
327 if (!read_seqcount_retry(&dentry->d_seq, seq)) {
328 ret = 1;
329 dentry->d_count++;
330 }
331
332 return ret;
333 }
334
335 /* validate "insecure" dentry pointer */
336 extern int d_validate(struct dentry *, struct dentry *);
337
338 /*
339 * helper function for dentry_operations.d_dname() members
340 */
341 extern char *dynamic_dname(struct dentry *, char *, int, const char *, ...);
342
343 extern char *__d_path(const struct path *path, struct path *root, char *, int);
344 extern char *d_path(const struct path *, char *, int);
345 extern char *d_path_with_unreachable(const struct path *, char *, int);
346 extern char *dentry_path_raw(struct dentry *, char *, int);
347 extern char *dentry_path(struct dentry *, char *, int);
348
349 /* Allocation counts.. */
350
351 /**
352 * dget, dget_dlock - get a reference to a dentry
353 * @dentry: dentry to get a reference to
354 *
355 * Given a dentry or %NULL pointer increment the reference count
356 * if appropriate and return the dentry. A dentry will not be
357 * destroyed when it has references.
358 */
359 static inline struct dentry *dget_dlock(struct dentry *dentry)
360 {
361 if (dentry)
362 dentry->d_count++;
363 return dentry;
364 }
365
366 static inline struct dentry *dget(struct dentry *dentry)
367 {
368 if (dentry) {
369 spin_lock(&dentry->d_lock);
370 dget_dlock(dentry);
371 spin_unlock(&dentry->d_lock);
372 }
373 return dentry;
374 }
375
376 extern struct dentry *dget_parent(struct dentry *dentry);
377
378 /**
379 * d_unhashed - is dentry hashed
380 * @dentry: entry to check
381 *
382 * Returns true if the dentry passed is not currently hashed.
383 */
384
385 static inline int d_unhashed(struct dentry *dentry)
386 {
387 return (dentry->d_flags & DCACHE_UNHASHED);
388 }
389
390 static inline int d_unlinked(struct dentry *dentry)
391 {
392 return d_unhashed(dentry) && !IS_ROOT(dentry);
393 }
394
395 static inline int cant_mount(struct dentry *dentry)
396 {
397 return (dentry->d_flags & DCACHE_CANT_MOUNT);
398 }
399
400 static inline void dont_mount(struct dentry *dentry)
401 {
402 spin_lock(&dentry->d_lock);
403 dentry->d_flags |= DCACHE_CANT_MOUNT;
404 spin_unlock(&dentry->d_lock);
405 }
406
407 extern void dput(struct dentry *);
408
409 static inline bool d_managed(struct dentry *dentry)
410 {
411 return dentry->d_flags & DCACHE_MANAGED_DENTRY;
412 }
413
414 static inline bool d_mountpoint(struct dentry *dentry)
415 {
416 return dentry->d_flags & DCACHE_MOUNTED;
417 }
418
419 extern struct vfsmount *lookup_mnt(struct path *);
420 extern struct dentry *lookup_create(struct nameidata *nd, int is_dir);
421
422 extern int sysctl_vfs_cache_pressure;
423
424 #endif /* __LINUX_DCACHE_H */