1 #ifndef __LINUX_DCACHE_H
2 #define __LINUX_DCACHE_H
3
4 #include <linux/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 /* The hash is always the low bits of hash_len */
29 #ifdef __LITTLE_ENDIAN
30 #define HASH_LEN_DECLARE u32 hash; u32 len;
31 #else
32 #define HASH_LEN_DECLARE u32 len; u32 hash;
33 #endif
34
35 /*
36 * "quick string" -- eases parameter passing, but more importantly
37 * saves "metadata" about the string (ie length and the hash).
38 *
39 * hash comes first so it snuggles against d_parent in the
40 * dentry.
41 */
42 struct qstr {
43 union {
44 struct {
45 HASH_LEN_DECLARE;
46 };
47 u64 hash_len;
48 };
49 const unsigned char *name;
50 };
51
52 #define QSTR_INIT(n,l) { { { .len = l } }, .name = n }
53 #define hashlen_hash(hashlen) ((u32) (hashlen))
54 #define hashlen_len(hashlen) ((u32)((hashlen) >> 32))
55
56 struct dentry_stat_t {
57 int nr_dentry;
58 int nr_unused;
59 int age_limit; /* age in seconds */
60 int want_pages; /* pages requested by system */
61 int dummy[2];
62 };
63 extern struct dentry_stat_t dentry_stat;
64
65 /* Name hashing routines. Initial hash value */
66 /* Hash courtesy of the R5 hash in reiserfs modulo sign bits */
67 #define init_name_hash() 0
68
69 /* partial hash update function. Assume roughly 4 bits per character */
70 static inline unsigned long
partial_name_hash(unsigned long c,unsigned long prevhash)71 partial_name_hash(unsigned long c, unsigned long prevhash)
72 {
73 return (prevhash + (c << 4) + (c >> 4)) * 11;
74 }
75
76 /*
77 * Finally: cut down the number of bits to a int value (and try to avoid
78 * losing bits)
79 */
end_name_hash(unsigned long hash)80 static inline unsigned long end_name_hash(unsigned long hash)
81 {
82 return (unsigned int) hash;
83 }
84
85 /* Compute the hash for a name string. */
86 extern unsigned int full_name_hash(const unsigned char *, unsigned int);
87
88 /*
89 * Try to keep struct dentry aligned on 64 byte cachelines (this will
90 * give reasonable cacheline footprint with larger lines without the
91 * large memory footprint increase).
92 */
93 #ifdef CONFIG_64BIT
94 # define DNAME_INLINE_LEN 32 /* 192 bytes */
95 #else
96 # ifdef CONFIG_SMP
97 # define DNAME_INLINE_LEN 36 /* 128 bytes */
98 # else
99 # define DNAME_INLINE_LEN 40 /* 128 bytes */
100 # endif
101 #endif
102
103 struct dentry {
104 /* RCU lookup touched fields */
105 unsigned int d_flags; /* protected by d_lock */
106 seqcount_t d_seq; /* per dentry seqlock */
107 struct hlist_bl_node d_hash; /* lookup hash list */
108 struct dentry *d_parent; /* parent directory */
109 struct qstr d_name;
110 struct inode *d_inode; /* Where the name belongs to - NULL is
111 * negative */
112 unsigned char d_iname[DNAME_INLINE_LEN]; /* small names */
113
114 /* Ref lookup also touches following */
115 unsigned int d_count; /* protected by d_lock */
116 spinlock_t d_lock; /* per dentry lock */
117 const struct dentry_operations *d_op;
118 struct super_block *d_sb; /* The root of the dentry tree */
119 unsigned long d_time; /* used by d_revalidate */
120 void *d_fsdata; /* fs-specific data */
121
122 struct list_head d_lru; /* LRU list */
123 /*
124 * d_child and d_rcu can share memory
125 */
126 union {
127 struct list_head d_child; /* child of parent list */
128 struct rcu_head d_rcu;
129 } d_u;
130 struct list_head d_subdirs; /* our children */
131 struct hlist_node d_alias; /* inode alias list */
132 };
133
134 /*
135 * dentry->d_lock spinlock nesting subclasses:
136 *
137 * 0: normal
138 * 1: nested
139 */
140 enum dentry_d_lock_class
141 {
142 DENTRY_D_LOCK_NORMAL, /* implicitly used by plain spin_lock() APIs. */
143 DENTRY_D_LOCK_NESTED
144 };
145
146 struct dentry_operations {
147 int (*d_revalidate)(struct dentry *, unsigned int);
148 int (*d_weak_revalidate)(struct dentry *, unsigned int);
149 int (*d_hash)(const struct dentry *, const struct inode *,
150 struct qstr *);
151 int (*d_compare)(const struct dentry *, const struct inode *,
152 const struct dentry *, const struct inode *,
153 unsigned int, const char *, const struct qstr *);
154 int (*d_delete)(const struct dentry *);
155 void (*d_release)(struct dentry *);
156 void (*d_prune)(struct dentry *);
157 void (*d_iput)(struct dentry *, struct inode *);
158 char *(*d_dname)(struct dentry *, char *, int);
159 struct vfsmount *(*d_automount)(struct path *);
160 int (*d_manage)(struct dentry *, bool);
161 void (*d_canonical_path)(const struct path *, struct path *);
162 } ____cacheline_aligned;
163
164 /*
165 * Locking rules for dentry_operations callbacks are to be found in
166 * Documentation/filesystems/Locking. Keep it updated!
167 *
168 * FUrther descriptions are found in Documentation/filesystems/vfs.txt.
169 * Keep it updated too!
170 */
171
172 /* d_flags entries */
173 #define DCACHE_OP_HASH 0x0001
174 #define DCACHE_OP_COMPARE 0x0002
175 #define DCACHE_OP_REVALIDATE 0x0004
176 #define DCACHE_OP_DELETE 0x0008
177 #define DCACHE_OP_PRUNE 0x0010
178
179 #define DCACHE_DISCONNECTED 0x0020
180 /* This dentry is possibly not currently connected to the dcache tree, in
181 * which case its parent will either be itself, or will have this flag as
182 * well. nfsd will not use a dentry with this bit set, but will first
183 * endeavour to clear the bit either by discovering that it is connected,
184 * or by performing lookup operations. Any filesystem which supports
185 * nfsd_operations MUST have a lookup function which, if it finds a
186 * directory inode with a DCACHE_DISCONNECTED dentry, will d_move that
187 * dentry into place and return that dentry rather than the passed one,
188 * typically using d_splice_alias. */
189
190 #define DCACHE_REFERENCED 0x0040 /* Recently used, don't discard. */
191 #define DCACHE_RCUACCESS 0x0080 /* Entry has ever been RCU-visible */
192
193 #define DCACHE_CANT_MOUNT 0x0100
194 #define DCACHE_GENOCIDE 0x0200
195 #define DCACHE_SHRINK_LIST 0x0400
196
197 #define DCACHE_OP_WEAK_REVALIDATE 0x0800
198
199 #define DCACHE_NFSFS_RENAMED 0x1000
200 /* this dentry has been "silly renamed" and has to be deleted on the last
201 * dput() */
202 #define DCACHE_COOKIE 0x2000 /* For use by dcookie subsystem */
203 #define DCACHE_FSNOTIFY_PARENT_WATCHED 0x4000
204 /* Parent inode is watched by some fsnotify listener */
205
206 #define DCACHE_MOUNTED 0x10000 /* is a mountpoint */
207 #define DCACHE_NEED_AUTOMOUNT 0x20000 /* handle automount on this dir */
208 #define DCACHE_MANAGE_TRANSIT 0x40000 /* manage transit from this dirent */
209 #define DCACHE_MANAGED_DENTRY \
210 (DCACHE_MOUNTED|DCACHE_NEED_AUTOMOUNT|DCACHE_MANAGE_TRANSIT)
211
212 #define DCACHE_DENTRY_KILLED 0x100000
213
214 extern seqlock_t rename_lock;
215
dname_external(struct dentry * dentry)216 static inline int dname_external(struct dentry *dentry)
217 {
218 return dentry->d_name.name != dentry->d_iname;
219 }
220
221 /*
222 * These are the low-level FS interfaces to the dcache..
223 */
224 extern void d_instantiate(struct dentry *, struct inode *);
225 extern struct dentry * d_instantiate_unique(struct dentry *, struct inode *);
226 extern struct dentry * d_materialise_unique(struct dentry *, struct inode *);
227 extern void __d_drop(struct dentry *dentry);
228 extern void d_drop(struct dentry *dentry);
229 extern void d_delete(struct dentry *);
230 extern void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op);
231
232 /* allocate/de-allocate */
233 extern struct dentry * d_alloc(struct dentry *, const struct qstr *);
234 extern struct dentry * d_alloc_pseudo(struct super_block *, const struct qstr *);
235 extern struct dentry * d_splice_alias(struct inode *, struct dentry *);
236 extern struct dentry * d_add_ci(struct dentry *, struct inode *, struct qstr *);
237 extern struct dentry *d_find_any_alias(struct inode *inode);
238 extern struct dentry * d_obtain_alias(struct inode *);
239 extern void shrink_dcache_sb(struct super_block *);
240 extern void shrink_dcache_parent(struct dentry *);
241 extern void shrink_dcache_for_umount(struct super_block *);
242 extern int d_invalidate(struct dentry *);
243
244 /* only used at mount-time */
245 extern struct dentry * d_make_root(struct inode *);
246
247 /* <clickety>-<click> the ramfs-type tree */
248 extern void d_genocide(struct dentry *);
249
250 extern struct dentry *d_find_alias(struct inode *);
251 extern void d_prune_aliases(struct inode *);
252
253 /* test whether we have any submounts in a subdir tree */
254 extern int have_submounts(struct dentry *);
255
256 /*
257 * This adds the entry to the hash queues.
258 */
259 extern void d_rehash(struct dentry *);
260
261 /**
262 * d_add - add dentry to hash queues
263 * @entry: dentry to add
264 * @inode: The inode to attach to this dentry
265 *
266 * This adds the entry to the hash queues and initializes @inode.
267 * The entry was actually filled in earlier during d_alloc().
268 */
269
d_add(struct dentry * entry,struct inode * inode)270 static inline void d_add(struct dentry *entry, struct inode *inode)
271 {
272 d_instantiate(entry, inode);
273 d_rehash(entry);
274 }
275
276 /**
277 * d_add_unique - add dentry to hash queues without aliasing
278 * @entry: dentry to add
279 * @inode: The inode to attach to this dentry
280 *
281 * This adds the entry to the hash queues and initializes @inode.
282 * The entry was actually filled in earlier during d_alloc().
283 */
d_add_unique(struct dentry * entry,struct inode * inode)284 static inline struct dentry *d_add_unique(struct dentry *entry, struct inode *inode)
285 {
286 struct dentry *res;
287
288 res = d_instantiate_unique(entry, inode);
289 d_rehash(res != NULL ? res : entry);
290 return res;
291 }
292
293 extern void dentry_update_name_case(struct dentry *, struct qstr *);
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(const struct dentry *, const struct qstr *);
301 extern struct dentry *d_hash_and_lookup(struct dentry *, struct qstr *);
302 extern struct dentry *__d_lookup(const struct dentry *, const struct qstr *);
303 extern struct dentry *__d_lookup_rcu(const struct dentry *parent,
304 const struct qstr *name,
305 unsigned *seq, struct inode *inode);
306
307 /**
308 * __d_rcu_to_refcount - take a refcount on dentry if sequence check is ok
309 * @dentry: dentry to take a ref on
310 * @seq: seqcount to verify against
311 * Returns: 0 on failure, else 1.
312 *
313 * __d_rcu_to_refcount operates on a dentry,seq pair that was returned
314 * by __d_lookup_rcu, to get a reference on an rcu-walk dentry.
315 */
__d_rcu_to_refcount(struct dentry * dentry,unsigned seq)316 static inline int __d_rcu_to_refcount(struct dentry *dentry, unsigned seq)
317 {
318 int ret = 0;
319
320 assert_spin_locked(&dentry->d_lock);
321 if (!read_seqcount_retry(&dentry->d_seq, seq)) {
322 ret = 1;
323 dentry->d_count++;
324 }
325
326 return ret;
327 }
328
329 /* validate "insecure" dentry pointer */
330 extern int d_validate(struct dentry *, struct dentry *);
331
332 /*
333 * helper function for dentry_operations.d_dname() members
334 */
335 extern char *dynamic_dname(struct dentry *, char *, int, const char *, ...);
336 extern char *simple_dname(struct dentry *, char *, int);
337
338 extern char *__d_path(const struct path *, const struct path *, char *, int);
339 extern char *d_absolute_path(const struct path *, char *, int);
340 extern char *d_path(const struct path *, char *, int);
341 extern char *dentry_path_raw(struct dentry *, char *, int);
342 extern char *dentry_path(struct dentry *, char *, int);
343
344 /* Allocation counts.. */
345
346 /**
347 * dget, dget_dlock - get a reference to a dentry
348 * @dentry: dentry to get a reference to
349 *
350 * Given a dentry or %NULL pointer increment the reference count
351 * if appropriate and return the dentry. A dentry will not be
352 * destroyed when it has references.
353 */
dget_dlock(struct dentry * dentry)354 static inline struct dentry *dget_dlock(struct dentry *dentry)
355 {
356 if (dentry)
357 dentry->d_count++;
358 return dentry;
359 }
360
dget(struct dentry * dentry)361 static inline struct dentry *dget(struct dentry *dentry)
362 {
363 if (dentry) {
364 spin_lock(&dentry->d_lock);
365 dget_dlock(dentry);
366 spin_unlock(&dentry->d_lock);
367 }
368 return dentry;
369 }
370
371 extern struct dentry *dget_parent(struct dentry *dentry);
372
373 /**
374 * d_unhashed - is dentry hashed
375 * @dentry: entry to check
376 *
377 * Returns true if the dentry passed is not currently hashed.
378 */
379
d_unhashed(struct dentry * dentry)380 static inline int d_unhashed(struct dentry *dentry)
381 {
382 return hlist_bl_unhashed(&dentry->d_hash);
383 }
384
d_unlinked(struct dentry * dentry)385 static inline int d_unlinked(struct dentry *dentry)
386 {
387 return d_unhashed(dentry) && !IS_ROOT(dentry);
388 }
389
cant_mount(struct dentry * dentry)390 static inline int cant_mount(struct dentry *dentry)
391 {
392 return (dentry->d_flags & DCACHE_CANT_MOUNT);
393 }
394
dont_mount(struct dentry * dentry)395 static inline void dont_mount(struct dentry *dentry)
396 {
397 spin_lock(&dentry->d_lock);
398 dentry->d_flags |= DCACHE_CANT_MOUNT;
399 spin_unlock(&dentry->d_lock);
400 }
401
402 extern void dput(struct dentry *);
403
d_managed(struct dentry * dentry)404 static inline bool d_managed(struct dentry *dentry)
405 {
406 return dentry->d_flags & DCACHE_MANAGED_DENTRY;
407 }
408
d_mountpoint(struct dentry * dentry)409 static inline bool d_mountpoint(struct dentry *dentry)
410 {
411 return dentry->d_flags & DCACHE_MOUNTED;
412 }
413
414 extern int sysctl_vfs_cache_pressure;
415
416 #endif /* __LINUX_DCACHE_H */
417