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Linux/include/linux/dcache.h

  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 #include <linux/lockref.h>
 13 #include <linux/stringhash.h>
 14 
 15 struct path;
 16 struct vfsmount;
 17 
 18 /*
 19  * linux/include/linux/dcache.h
 20  *
 21  * Dirent cache data structures
 22  *
 23  * (C) Copyright 1997 Thomas Schoebel-Theuer,
 24  * with heavy changes by Linus Torvalds
 25  */
 26 
 27 #define IS_ROOT(x) ((x) == (x)->d_parent)
 28 
 29 /* The hash is always the low bits of hash_len */
 30 #ifdef __LITTLE_ENDIAN
 31  #define HASH_LEN_DECLARE u32 hash; u32 len
 32  #define bytemask_from_count(cnt)       (~(~0ul << (cnt)*8))
 33 #else
 34  #define HASH_LEN_DECLARE u32 len; u32 hash
 35  #define bytemask_from_count(cnt)       (~(~0ul >> (cnt)*8))
 36 #endif
 37 
 38 /*
 39  * "quick string" -- eases parameter passing, but more importantly
 40  * saves "metadata" about the string (ie length and the hash).
 41  *
 42  * hash comes first so it snuggles against d_parent in the
 43  * dentry.
 44  */
 45 struct qstr {
 46         union {
 47                 struct {
 48                         HASH_LEN_DECLARE;
 49                 };
 50                 u64 hash_len;
 51         };
 52         const unsigned char *name;
 53 };
 54 
 55 #define QSTR_INIT(n,l) { { { .len = l } }, .name = n }
 56 
 57 struct dentry_stat_t {
 58         long nr_dentry;
 59         long nr_unused;
 60         long age_limit;          /* age in seconds */
 61         long want_pages;         /* pages requested by system */
 62         long dummy[2];
 63 };
 64 extern struct dentry_stat_t dentry_stat;
 65 
 66 /*
 67  * Try to keep struct dentry aligned on 64 byte cachelines (this will
 68  * give reasonable cacheline footprint with larger lines without the
 69  * large memory footprint increase).
 70  */
 71 #ifdef CONFIG_64BIT
 72 # define DNAME_INLINE_LEN 32 /* 192 bytes */
 73 #else
 74 # ifdef CONFIG_SMP
 75 #  define DNAME_INLINE_LEN 36 /* 128 bytes */
 76 # else
 77 #  define DNAME_INLINE_LEN 40 /* 128 bytes */
 78 # endif
 79 #endif
 80 
 81 #define d_lock  d_lockref.lock
 82 
 83 struct dentry {
 84         /* RCU lookup touched fields */
 85         unsigned int d_flags;           /* protected by d_lock */
 86         seqcount_t d_seq;               /* per dentry seqlock */
 87         struct hlist_bl_node d_hash;    /* lookup hash list */
 88         struct dentry *d_parent;        /* parent directory */
 89         struct qstr d_name;
 90         struct inode *d_inode;          /* Where the name belongs to - NULL is
 91                                          * negative */
 92         unsigned char d_iname[DNAME_INLINE_LEN];        /* small names */
 93 
 94         /* Ref lookup also touches following */
 95         struct lockref d_lockref;       /* per-dentry lock and refcount */
 96         const struct dentry_operations *d_op;
 97         struct super_block *d_sb;       /* The root of the dentry tree */
 98         unsigned long d_time;           /* used by d_revalidate */
 99         void *d_fsdata;                 /* fs-specific data */
100 
101         union {
102                 struct list_head d_lru;         /* LRU list */
103                 wait_queue_head_t *d_wait;      /* in-lookup ones only */
104         };
105         struct list_head d_child;       /* child of parent list */
106         struct list_head d_subdirs;     /* our children */
107         /*
108          * d_alias and d_rcu can share memory
109          */
110         union {
111                 struct hlist_node d_alias;      /* inode alias list */
112                 struct hlist_bl_node d_in_lookup_hash;  /* only for in-lookup ones */
113                 struct rcu_head d_rcu;
114         } d_u;
115 };
116 
117 /*
118  * dentry->d_lock spinlock nesting subclasses:
119  *
120  * 0: normal
121  * 1: nested
122  */
123 enum dentry_d_lock_class
124 {
125         DENTRY_D_LOCK_NORMAL, /* implicitly used by plain spin_lock() APIs. */
126         DENTRY_D_LOCK_NESTED
127 };
128 
129 struct dentry_operations {
130         int (*d_revalidate)(struct dentry *, unsigned int);
131         int (*d_weak_revalidate)(struct dentry *, unsigned int);
132         int (*d_hash)(const struct dentry *, struct qstr *);
133         int (*d_compare)(const struct dentry *,
134                         unsigned int, const char *, const struct qstr *);
135         int (*d_delete)(const struct dentry *);
136         int (*d_init)(struct dentry *);
137         void (*d_release)(struct dentry *);
138         void (*d_prune)(struct dentry *);
139         void (*d_iput)(struct dentry *, struct inode *);
140         char *(*d_dname)(struct dentry *, char *, int);
141         struct vfsmount *(*d_automount)(struct path *);
142         int (*d_manage)(struct dentry *, bool);
143         struct dentry *(*d_real)(struct dentry *, const struct inode *,
144                                  unsigned int);
145 } ____cacheline_aligned;
146 
147 /*
148  * Locking rules for dentry_operations callbacks are to be found in
149  * Documentation/filesystems/Locking. Keep it updated!
150  *
151  * FUrther descriptions are found in Documentation/filesystems/vfs.txt.
152  * Keep it updated too!
153  */
154 
155 /* d_flags entries */
156 #define DCACHE_OP_HASH                  0x00000001
157 #define DCACHE_OP_COMPARE               0x00000002
158 #define DCACHE_OP_REVALIDATE            0x00000004
159 #define DCACHE_OP_DELETE                0x00000008
160 #define DCACHE_OP_PRUNE                 0x00000010
161 
162 #define DCACHE_DISCONNECTED             0x00000020
163      /* This dentry is possibly not currently connected to the dcache tree, in
164       * which case its parent will either be itself, or will have this flag as
165       * well.  nfsd will not use a dentry with this bit set, but will first
166       * endeavour to clear the bit either by discovering that it is connected,
167       * or by performing lookup operations.   Any filesystem which supports
168       * nfsd_operations MUST have a lookup function which, if it finds a
169       * directory inode with a DCACHE_DISCONNECTED dentry, will d_move that
170       * dentry into place and return that dentry rather than the passed one,
171       * typically using d_splice_alias. */
172 
173 #define DCACHE_REFERENCED               0x00000040 /* Recently used, don't discard. */
174 #define DCACHE_RCUACCESS                0x00000080 /* Entry has ever been RCU-visible */
175 
176 #define DCACHE_CANT_MOUNT               0x00000100
177 #define DCACHE_GENOCIDE                 0x00000200
178 #define DCACHE_SHRINK_LIST              0x00000400
179 
180 #define DCACHE_OP_WEAK_REVALIDATE       0x00000800
181 
182 #define DCACHE_NFSFS_RENAMED            0x00001000
183      /* this dentry has been "silly renamed" and has to be deleted on the last
184       * dput() */
185 #define DCACHE_COOKIE                   0x00002000 /* For use by dcookie subsystem */
186 #define DCACHE_FSNOTIFY_PARENT_WATCHED  0x00004000
187      /* Parent inode is watched by some fsnotify listener */
188 
189 #define DCACHE_DENTRY_KILLED            0x00008000
190 
191 #define DCACHE_MOUNTED                  0x00010000 /* is a mountpoint */
192 #define DCACHE_NEED_AUTOMOUNT           0x00020000 /* handle automount on this dir */
193 #define DCACHE_MANAGE_TRANSIT           0x00040000 /* manage transit from this dirent */
194 #define DCACHE_MANAGED_DENTRY \
195         (DCACHE_MOUNTED|DCACHE_NEED_AUTOMOUNT|DCACHE_MANAGE_TRANSIT)
196 
197 #define DCACHE_LRU_LIST                 0x00080000
198 
199 #define DCACHE_ENTRY_TYPE               0x00700000
200 #define DCACHE_MISS_TYPE                0x00000000 /* Negative dentry (maybe fallthru to nowhere) */
201 #define DCACHE_WHITEOUT_TYPE            0x00100000 /* Whiteout dentry (stop pathwalk) */
202 #define DCACHE_DIRECTORY_TYPE           0x00200000 /* Normal directory */
203 #define DCACHE_AUTODIR_TYPE             0x00300000 /* Lookupless directory (presumed automount) */
204 #define DCACHE_REGULAR_TYPE             0x00400000 /* Regular file type (or fallthru to such) */
205 #define DCACHE_SPECIAL_TYPE             0x00500000 /* Other file type (or fallthru to such) */
206 #define DCACHE_SYMLINK_TYPE             0x00600000 /* Symlink (or fallthru to such) */
207 
208 #define DCACHE_MAY_FREE                 0x00800000
209 #define DCACHE_FALLTHRU                 0x01000000 /* Fall through to lower layer */
210 #define DCACHE_ENCRYPTED_WITH_KEY       0x02000000 /* dir is encrypted with a valid key */
211 #define DCACHE_OP_REAL                  0x04000000
212 
213 #define DCACHE_PAR_LOOKUP               0x10000000 /* being looked up (with parent locked shared) */
214 #define DCACHE_DENTRY_CURSOR            0x20000000
215 
216 extern seqlock_t rename_lock;
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 int d_instantiate_no_diralias(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_alloc_parallel(struct dentry *, const struct qstr *,
233                                         wait_queue_head_t *);
234 extern struct dentry * d_splice_alias(struct inode *, struct dentry *);
235 extern struct dentry * d_add_ci(struct dentry *, struct inode *, struct qstr *);
236 extern struct dentry * d_exact_alias(struct dentry *, struct inode *);
237 extern struct dentry *d_find_any_alias(struct inode *inode);
238 extern struct dentry * d_obtain_alias(struct inode *);
239 extern struct dentry * d_obtain_root(struct inode *);
240 extern void shrink_dcache_sb(struct super_block *);
241 extern void shrink_dcache_parent(struct dentry *);
242 extern void shrink_dcache_for_umount(struct super_block *);
243 extern void d_invalidate(struct dentry *);
244 
245 /* only used at mount-time */
246 extern struct dentry * d_make_root(struct inode *);
247 
248 /* <clickety>-<click> the ramfs-type tree */
249 extern void d_genocide(struct dentry *);
250 
251 extern void d_tmpfile(struct dentry *, struct inode *);
252 
253 extern struct dentry *d_find_alias(struct inode *);
254 extern void d_prune_aliases(struct inode *);
255 
256 /* test whether we have any submounts in a subdir tree */
257 extern int have_submounts(struct dentry *);
258 
259 /*
260  * This adds the entry to the hash queues.
261  */
262 extern void d_rehash(struct dentry *);
263  
264 extern void d_add(struct dentry *, struct inode *);
265 
266 extern void dentry_update_name_case(struct dentry *, const struct qstr *);
267 
268 /* used for rename() and baskets */
269 extern void d_move(struct dentry *, struct dentry *);
270 extern void d_exchange(struct dentry *, struct dentry *);
271 extern struct dentry *d_ancestor(struct dentry *, struct dentry *);
272 
273 /* appendix may either be NULL or be used for transname suffixes */
274 extern struct dentry *d_lookup(const struct dentry *, const struct qstr *);
275 extern struct dentry *d_hash_and_lookup(struct dentry *, struct qstr *);
276 extern struct dentry *__d_lookup(const struct dentry *, const struct qstr *);
277 extern struct dentry *__d_lookup_rcu(const struct dentry *parent,
278                                 const struct qstr *name, unsigned *seq);
279 
280 static inline unsigned d_count(const struct dentry *dentry)
281 {
282         return dentry->d_lockref.count;
283 }
284 
285 /*
286  * helper function for dentry_operations.d_dname() members
287  */
288 extern __printf(4, 5)
289 char *dynamic_dname(struct dentry *, char *, int, const char *, ...);
290 extern char *simple_dname(struct dentry *, char *, int);
291 
292 extern char *__d_path(const struct path *, const struct path *, char *, int);
293 extern char *d_absolute_path(const struct path *, char *, int);
294 extern char *d_path(const struct path *, char *, int);
295 extern char *dentry_path_raw(struct dentry *, char *, int);
296 extern char *dentry_path(struct dentry *, char *, int);
297 
298 /* Allocation counts.. */
299 
300 /**
301  *      dget, dget_dlock -      get a reference to a dentry
302  *      @dentry: dentry to get a reference to
303  *
304  *      Given a dentry or %NULL pointer increment the reference count
305  *      if appropriate and return the dentry. A dentry will not be 
306  *      destroyed when it has references.
307  */
308 static inline struct dentry *dget_dlock(struct dentry *dentry)
309 {
310         if (dentry)
311                 dentry->d_lockref.count++;
312         return dentry;
313 }
314 
315 static inline struct dentry *dget(struct dentry *dentry)
316 {
317         if (dentry)
318                 lockref_get(&dentry->d_lockref);
319         return dentry;
320 }
321 
322 extern struct dentry *dget_parent(struct dentry *dentry);
323 
324 /**
325  *      d_unhashed -    is dentry hashed
326  *      @dentry: entry to check
327  *
328  *      Returns true if the dentry passed is not currently hashed.
329  */
330  
331 static inline int d_unhashed(const struct dentry *dentry)
332 {
333         return hlist_bl_unhashed(&dentry->d_hash);
334 }
335 
336 static inline int d_unlinked(const struct dentry *dentry)
337 {
338         return d_unhashed(dentry) && !IS_ROOT(dentry);
339 }
340 
341 static inline int cant_mount(const struct dentry *dentry)
342 {
343         return (dentry->d_flags & DCACHE_CANT_MOUNT);
344 }
345 
346 static inline void dont_mount(struct dentry *dentry)
347 {
348         spin_lock(&dentry->d_lock);
349         dentry->d_flags |= DCACHE_CANT_MOUNT;
350         spin_unlock(&dentry->d_lock);
351 }
352 
353 extern void __d_lookup_done(struct dentry *);
354 
355 static inline int d_in_lookup(struct dentry *dentry)
356 {
357         return dentry->d_flags & DCACHE_PAR_LOOKUP;
358 }
359 
360 static inline void d_lookup_done(struct dentry *dentry)
361 {
362         if (unlikely(d_in_lookup(dentry))) {
363                 spin_lock(&dentry->d_lock);
364                 __d_lookup_done(dentry);
365                 spin_unlock(&dentry->d_lock);
366         }
367 }
368 
369 extern void dput(struct dentry *);
370 
371 static inline bool d_managed(const struct dentry *dentry)
372 {
373         return dentry->d_flags & DCACHE_MANAGED_DENTRY;
374 }
375 
376 static inline bool d_mountpoint(const struct dentry *dentry)
377 {
378         return dentry->d_flags & DCACHE_MOUNTED;
379 }
380 
381 /*
382  * Directory cache entry type accessor functions.
383  */
384 static inline unsigned __d_entry_type(const struct dentry *dentry)
385 {
386         return dentry->d_flags & DCACHE_ENTRY_TYPE;
387 }
388 
389 static inline bool d_is_miss(const struct dentry *dentry)
390 {
391         return __d_entry_type(dentry) == DCACHE_MISS_TYPE;
392 }
393 
394 static inline bool d_is_whiteout(const struct dentry *dentry)
395 {
396         return __d_entry_type(dentry) == DCACHE_WHITEOUT_TYPE;
397 }
398 
399 static inline bool d_can_lookup(const struct dentry *dentry)
400 {
401         return __d_entry_type(dentry) == DCACHE_DIRECTORY_TYPE;
402 }
403 
404 static inline bool d_is_autodir(const struct dentry *dentry)
405 {
406         return __d_entry_type(dentry) == DCACHE_AUTODIR_TYPE;
407 }
408 
409 static inline bool d_is_dir(const struct dentry *dentry)
410 {
411         return d_can_lookup(dentry) || d_is_autodir(dentry);
412 }
413 
414 static inline bool d_is_symlink(const struct dentry *dentry)
415 {
416         return __d_entry_type(dentry) == DCACHE_SYMLINK_TYPE;
417 }
418 
419 static inline bool d_is_reg(const struct dentry *dentry)
420 {
421         return __d_entry_type(dentry) == DCACHE_REGULAR_TYPE;
422 }
423 
424 static inline bool d_is_special(const struct dentry *dentry)
425 {
426         return __d_entry_type(dentry) == DCACHE_SPECIAL_TYPE;
427 }
428 
429 static inline bool d_is_file(const struct dentry *dentry)
430 {
431         return d_is_reg(dentry) || d_is_special(dentry);
432 }
433 
434 static inline bool d_is_negative(const struct dentry *dentry)
435 {
436         // TODO: check d_is_whiteout(dentry) also.
437         return d_is_miss(dentry);
438 }
439 
440 static inline bool d_is_positive(const struct dentry *dentry)
441 {
442         return !d_is_negative(dentry);
443 }
444 
445 /**
446  * d_really_is_negative - Determine if a dentry is really negative (ignoring fallthroughs)
447  * @dentry: The dentry in question
448  *
449  * Returns true if the dentry represents either an absent name or a name that
450  * doesn't map to an inode (ie. ->d_inode is NULL).  The dentry could represent
451  * a true miss, a whiteout that isn't represented by a 0,0 chardev or a
452  * fallthrough marker in an opaque directory.
453  *
454  * Note!  (1) This should be used *only* by a filesystem to examine its own
455  * dentries.  It should not be used to look at some other filesystem's
456  * dentries.  (2) It should also be used in combination with d_inode() to get
457  * the inode.  (3) The dentry may have something attached to ->d_lower and the
458  * type field of the flags may be set to something other than miss or whiteout.
459  */
460 static inline bool d_really_is_negative(const struct dentry *dentry)
461 {
462         return dentry->d_inode == NULL;
463 }
464 
465 /**
466  * d_really_is_positive - Determine if a dentry is really positive (ignoring fallthroughs)
467  * @dentry: The dentry in question
468  *
469  * Returns true if the dentry represents a name that maps to an inode
470  * (ie. ->d_inode is not NULL).  The dentry might still represent a whiteout if
471  * that is represented on medium as a 0,0 chardev.
472  *
473  * Note!  (1) This should be used *only* by a filesystem to examine its own
474  * dentries.  It should not be used to look at some other filesystem's
475  * dentries.  (2) It should also be used in combination with d_inode() to get
476  * the inode.
477  */
478 static inline bool d_really_is_positive(const struct dentry *dentry)
479 {
480         return dentry->d_inode != NULL;
481 }
482 
483 static inline int simple_positive(struct dentry *dentry)
484 {
485         return d_really_is_positive(dentry) && !d_unhashed(dentry);
486 }
487 
488 extern void d_set_fallthru(struct dentry *dentry);
489 
490 static inline bool d_is_fallthru(const struct dentry *dentry)
491 {
492         return dentry->d_flags & DCACHE_FALLTHRU;
493 }
494 
495 
496 extern int sysctl_vfs_cache_pressure;
497 
498 static inline unsigned long vfs_pressure_ratio(unsigned long val)
499 {
500         return mult_frac(val, sysctl_vfs_cache_pressure, 100);
501 }
502 
503 /**
504  * d_inode - Get the actual inode of this dentry
505  * @dentry: The dentry to query
506  *
507  * This is the helper normal filesystems should use to get at their own inodes
508  * in their own dentries and ignore the layering superimposed upon them.
509  */
510 static inline struct inode *d_inode(const struct dentry *dentry)
511 {
512         return dentry->d_inode;
513 }
514 
515 /**
516  * d_inode_rcu - Get the actual inode of this dentry with ACCESS_ONCE()
517  * @dentry: The dentry to query
518  *
519  * This is the helper normal filesystems should use to get at their own inodes
520  * in their own dentries and ignore the layering superimposed upon them.
521  */
522 static inline struct inode *d_inode_rcu(const struct dentry *dentry)
523 {
524         return ACCESS_ONCE(dentry->d_inode);
525 }
526 
527 /**
528  * d_backing_inode - Get upper or lower inode we should be using
529  * @upper: The upper layer
530  *
531  * This is the helper that should be used to get at the inode that will be used
532  * if this dentry were to be opened as a file.  The inode may be on the upper
533  * dentry or it may be on a lower dentry pinned by the upper.
534  *
535  * Normal filesystems should not use this to access their own inodes.
536  */
537 static inline struct inode *d_backing_inode(const struct dentry *upper)
538 {
539         struct inode *inode = upper->d_inode;
540 
541         return inode;
542 }
543 
544 /**
545  * d_backing_dentry - Get upper or lower dentry we should be using
546  * @upper: The upper layer
547  *
548  * This is the helper that should be used to get the dentry of the inode that
549  * will be used if this dentry were opened as a file.  It may be the upper
550  * dentry or it may be a lower dentry pinned by the upper.
551  *
552  * Normal filesystems should not use this to access their own dentries.
553  */
554 static inline struct dentry *d_backing_dentry(struct dentry *upper)
555 {
556         return upper;
557 }
558 
559 /**
560  * d_real - Return the real dentry
561  * @dentry: the dentry to query
562  * @inode: inode to select the dentry from multiple layers (can be NULL)
563  * @flags: open flags to control copy-up behavior
564  *
565  * If dentry is on an union/overlay, then return the underlying, real dentry.
566  * Otherwise return the dentry itself.
567  *
568  * See also: Documentation/filesystems/vfs.txt
569  */
570 static inline struct dentry *d_real(struct dentry *dentry,
571                                     const struct inode *inode,
572                                     unsigned int flags)
573 {
574         if (unlikely(dentry->d_flags & DCACHE_OP_REAL))
575                 return dentry->d_op->d_real(dentry, inode, flags);
576         else
577                 return dentry;
578 }
579 
580 /**
581  * d_real_inode - Return the real inode
582  * @dentry: The dentry to query
583  *
584  * If dentry is on an union/overlay, then return the underlying, real inode.
585  * Otherwise return d_inode().
586  */
587 static inline struct inode *d_real_inode(struct dentry *dentry)
588 {
589         return d_backing_inode(d_real(dentry, NULL, 0));
590 }
591 
592 
593 #endif  /* __LINUX_DCACHE_H */
594 

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