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dcache.h
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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 {
46  };
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
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  */
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  */
141 {
142  DENTRY_D_LOCK_NORMAL, /* implicitly used by plain spin_lock() APIs. */
144 };
145 
147  int (*d_revalidate)(struct dentry *, unsigned int);
148  int (*d_hash)(const struct dentry *, const struct inode *,
149  struct qstr *);
150  int (*d_compare)(const struct dentry *, const struct inode *,
151  const struct dentry *, const struct inode *,
152  unsigned int, const char *, const struct qstr *);
153  int (*d_delete)(const struct dentry *);
154  void (*d_release)(struct dentry *);
155  void (*d_prune)(struct dentry *);
156  void (*d_iput)(struct dentry *, struct inode *);
157  char *(*d_dname)(struct dentry *, char *, int);
158  struct vfsmount *(*d_automount)(struct path *);
159  int (*d_manage)(struct dentry *, bool);
161 
162 /*
163  * Locking rules for dentry_operations callbacks are to be found in
164  * Documentation/filesystems/Locking. Keep it updated!
165  *
166  * FUrther descriptions are found in Documentation/filesystems/vfs.txt.
167  * Keep it updated too!
168  */
169 
170 /* d_flags entries */
171 #define DCACHE_OP_HASH 0x0001
172 #define DCACHE_OP_COMPARE 0x0002
173 #define DCACHE_OP_REVALIDATE 0x0004
174 #define DCACHE_OP_DELETE 0x0008
175 #define DCACHE_OP_PRUNE 0x0010
176 
177 #define DCACHE_DISCONNECTED 0x0020
178  /* This dentry is possibly not currently connected to the dcache tree, in
179  * which case its parent will either be itself, or will have this flag as
180  * well. nfsd will not use a dentry with this bit set, but will first
181  * endeavour to clear the bit either by discovering that it is connected,
182  * or by performing lookup operations. Any filesystem which supports
183  * nfsd_operations MUST have a lookup function which, if it finds a
184  * directory inode with a DCACHE_DISCONNECTED dentry, will d_move that
185  * dentry into place and return that dentry rather than the passed one,
186  * typically using d_splice_alias. */
187 
188 #define DCACHE_REFERENCED 0x0040 /* Recently used, don't discard. */
189 #define DCACHE_RCUACCESS 0x0080 /* Entry has ever been RCU-visible */
190 
191 #define DCACHE_CANT_MOUNT 0x0100
192 #define DCACHE_GENOCIDE 0x0200
193 #define DCACHE_SHRINK_LIST 0x0400
194 
195 #define DCACHE_NFSFS_RENAMED 0x1000
196  /* this dentry has been "silly renamed" and has to be deleted on the last
197  * dput() */
198 #define DCACHE_COOKIE 0x2000 /* For use by dcookie subsystem */
199 #define DCACHE_FSNOTIFY_PARENT_WATCHED 0x4000
200  /* Parent inode is watched by some fsnotify listener */
201 
202 #define DCACHE_MOUNTED 0x10000 /* is a mountpoint */
203 #define DCACHE_NEED_AUTOMOUNT 0x20000 /* handle automount on this dir */
204 #define DCACHE_MANAGE_TRANSIT 0x40000 /* manage transit from this dirent */
205 #define DCACHE_NEED_LOOKUP 0x80000 /* dentry requires i_op->lookup */
206 #define DCACHE_MANAGED_DENTRY \
207  (DCACHE_MOUNTED|DCACHE_NEED_AUTOMOUNT|DCACHE_MANAGE_TRANSIT)
208 
209 #define DCACHE_DENTRY_KILLED 0x100000
210 
211 extern seqlock_t rename_lock;
212 
213 static inline int dname_external(struct dentry *dentry)
214 {
215  return dentry->d_name.name != dentry->d_iname;
216 }
217 
218 /*
219  * These are the low-level FS interfaces to the dcache..
220  */
221 extern void d_instantiate(struct dentry *, struct inode *);
222 extern struct dentry * d_instantiate_unique(struct dentry *, struct inode *);
223 extern struct dentry * d_materialise_unique(struct dentry *, struct inode *);
224 extern void __d_drop(struct dentry *dentry);
225 extern void d_drop(struct dentry *dentry);
226 extern void d_delete(struct dentry *);
227 extern void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op);
228 
229 /* allocate/de-allocate */
230 extern struct dentry * d_alloc(struct dentry *, const struct qstr *);
231 extern struct dentry * d_alloc_pseudo(struct super_block *, const struct qstr *);
232 extern struct dentry * d_splice_alias(struct inode *, struct dentry *);
233 extern struct dentry * d_add_ci(struct dentry *, struct inode *, struct qstr *);
234 extern struct dentry *d_find_any_alias(struct inode *inode);
235 extern struct dentry * d_obtain_alias(struct inode *);
236 extern void shrink_dcache_sb(struct super_block *);
237 extern void shrink_dcache_parent(struct dentry *);
238 extern void shrink_dcache_for_umount(struct super_block *);
239 extern int d_invalidate(struct dentry *);
240 
241 /* only used at mount-time */
242 extern struct dentry * d_make_root(struct inode *);
243 
244 /* <clickety>-<click> the ramfs-type tree */
245 extern void d_genocide(struct dentry *);
246 
247 extern struct dentry *d_find_alias(struct inode *);
248 extern void d_prune_aliases(struct inode *);
249 
250 /* test whether we have any submounts in a subdir tree */
251 extern int have_submounts(struct dentry *);
252 
253 /*
254  * This adds the entry to the hash queues.
255  */
256 extern void d_rehash(struct dentry *);
257 
267 static inline void d_add(struct dentry *entry, struct inode *inode)
268 {
269  d_instantiate(entry, inode);
270  d_rehash(entry);
271 }
272 
281 static inline struct dentry *d_add_unique(struct dentry *entry, struct inode *inode)
282 {
283  struct dentry *res;
284 
285  res = d_instantiate_unique(entry, inode);
286  d_rehash(res != NULL ? res : entry);
287  return res;
288 }
289 
290 extern void dentry_update_name_case(struct dentry *, struct qstr *);
291 
292 /* used for rename() and baskets */
293 extern void d_move(struct dentry *, struct dentry *);
294 extern struct dentry *d_ancestor(struct dentry *, struct dentry *);
295 
296 /* appendix may either be NULL or be used for transname suffixes */
297 extern struct dentry *d_lookup(struct dentry *, struct qstr *);
298 extern struct dentry *d_hash_and_lookup(struct dentry *, struct qstr *);
299 extern struct dentry *__d_lookup(struct dentry *, struct qstr *);
300 extern struct dentry *__d_lookup_rcu(const struct dentry *parent,
301  const struct qstr *name,
302  unsigned *seq, struct inode *inode);
303 
313 static inline int __d_rcu_to_refcount(struct dentry *dentry, unsigned seq)
314 {
315  int ret = 0;
316 
317  assert_spin_locked(&dentry->d_lock);
318  if (!read_seqcount_retry(&dentry->d_seq, seq)) {
319  ret = 1;
320  dentry->d_count++;
321  }
322 
323  return ret;
324 }
325 
326 /* validate "insecure" dentry pointer */
327 extern int d_validate(struct dentry *, struct dentry *);
328 
329 /*
330  * helper function for dentry_operations.d_dname() members
331  */
332 extern char *dynamic_dname(struct dentry *, char *, int, const char *, ...);
333 
334 extern char *__d_path(const struct path *, const struct path *, char *, int);
335 extern char *d_absolute_path(const struct path *, char *, int);
336 extern char *d_path(const struct path *, char *, int);
337 extern char *d_path_with_unreachable(const struct path *, char *, int);
338 extern char *dentry_path_raw(struct dentry *, char *, int);
339 extern char *dentry_path(struct dentry *, char *, int);
340 
341 /* Allocation counts.. */
342 
351 static inline struct dentry *dget_dlock(struct dentry *dentry)
352 {
353  if (dentry)
354  dentry->d_count++;
355  return dentry;
356 }
357 
358 static inline struct dentry *dget(struct dentry *dentry)
359 {
360  if (dentry) {
361  spin_lock(&dentry->d_lock);
362  dget_dlock(dentry);
363  spin_unlock(&dentry->d_lock);
364  }
365  return dentry;
366 }
367 
368 extern struct dentry *dget_parent(struct dentry *dentry);
369 
377 static inline int d_unhashed(struct dentry *dentry)
378 {
379  return hlist_bl_unhashed(&dentry->d_hash);
380 }
381 
382 static inline int d_unlinked(struct dentry *dentry)
383 {
384  return d_unhashed(dentry) && !IS_ROOT(dentry);
385 }
386 
387 static inline int cant_mount(struct dentry *dentry)
388 {
389  return (dentry->d_flags & DCACHE_CANT_MOUNT);
390 }
391 
392 static inline void dont_mount(struct dentry *dentry)
393 {
394  spin_lock(&dentry->d_lock);
395  dentry->d_flags |= DCACHE_CANT_MOUNT;
396  spin_unlock(&dentry->d_lock);
397 }
398 
399 extern void dput(struct dentry *);
400 
401 static inline bool d_managed(struct dentry *dentry)
402 {
403  return dentry->d_flags & DCACHE_MANAGED_DENTRY;
404 }
405 
406 static inline bool d_mountpoint(struct dentry *dentry)
407 {
408  return dentry->d_flags & DCACHE_MOUNTED;
409 }
410 
411 static inline bool d_need_lookup(struct dentry *dentry)
412 {
413  return dentry->d_flags & DCACHE_NEED_LOOKUP;
414 }
415 
416 extern void d_clear_need_lookup(struct dentry *dentry);
417 
418 extern int sysctl_vfs_cache_pressure;
419 
420 #endif /* __LINUX_DCACHE_H */