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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 
 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  #define bytemask_from_count(cnt)       (~(~0ul << (cnt)*8))
 32 #else
 33  #define HASH_LEN_DECLARE u32 len; u32 hash
 34  #define bytemask_from_count(cnt)       (~(~0ul >> (cnt)*8))
 35 #endif
 36 
 37 /*
 38  * "quick string" -- eases parameter passing, but more importantly
 39  * saves "metadata" about the string (ie length and the hash).
 40  *
 41  * hash comes first so it snuggles against d_parent in the
 42  * dentry.
 43  */
 44 struct qstr {
 45         union {
 46                 struct {
 47                         HASH_LEN_DECLARE;
 48                 };
 49                 u64 hash_len;
 50         };
 51         const unsigned char *name;
 52 };
 53 
 54 #define QSTR_INIT(n,l) { { { .len = l } }, .name = n }
 55 #define hashlen_hash(hashlen) ((u32) (hashlen))
 56 #define hashlen_len(hashlen)  ((u32)((hashlen) >> 32))
 57 #define hashlen_create(hash,len) (((u64)(len)<<32)|(u32)(hash))
 58 
 59 struct dentry_stat_t {
 60         long nr_dentry;
 61         long nr_unused;
 62         long age_limit;          /* age in seconds */
 63         long want_pages;         /* pages requested by system */
 64         long dummy[2];
 65 };
 66 extern struct dentry_stat_t dentry_stat;
 67 
 68 /* Name hashing routines. Initial hash value */
 69 /* Hash courtesy of the R5 hash in reiserfs modulo sign bits */
 70 #define init_name_hash()                0
 71 
 72 /* partial hash update function. Assume roughly 4 bits per character */
 73 static inline unsigned long
 74 partial_name_hash(unsigned long c, unsigned long prevhash)
 75 {
 76         return (prevhash + (c << 4) + (c >> 4)) * 11;
 77 }
 78 
 79 /*
 80  * Finally: cut down the number of bits to a int value (and try to avoid
 81  * losing bits)
 82  */
 83 static inline unsigned long end_name_hash(unsigned long hash)
 84 {
 85         return (unsigned int) hash;
 86 }
 87 
 88 /* Compute the hash for a name string. */
 89 extern unsigned int full_name_hash(const unsigned char *, unsigned int);
 90 
 91 /*
 92  * Try to keep struct dentry aligned on 64 byte cachelines (this will
 93  * give reasonable cacheline footprint with larger lines without the
 94  * large memory footprint increase).
 95  */
 96 #ifdef CONFIG_64BIT
 97 # define DNAME_INLINE_LEN 32 /* 192 bytes */
 98 #else
 99 # ifdef CONFIG_SMP
100 #  define DNAME_INLINE_LEN 36 /* 128 bytes */
101 # else
102 #  define DNAME_INLINE_LEN 40 /* 128 bytes */
103 # endif
104 #endif
105 
106 #define d_lock  d_lockref.lock
107 
108 struct dentry {
109         /* RCU lookup touched fields */
110         unsigned int d_flags;           /* protected by d_lock */
111         seqcount_t d_seq;               /* per dentry seqlock */
112         struct hlist_bl_node d_hash;    /* lookup hash list */
113         struct dentry *d_parent;        /* parent directory */
114         struct qstr d_name;
115         struct inode *d_inode;          /* Where the name belongs to - NULL is
116                                          * negative */
117         unsigned char d_iname[DNAME_INLINE_LEN];        /* small names */
118 
119         /* Ref lookup also touches following */
120         struct lockref d_lockref;       /* per-dentry lock and refcount */
121         const struct dentry_operations *d_op;
122         struct super_block *d_sb;       /* The root of the dentry tree */
123         unsigned long d_time;           /* used by d_revalidate */
124         void *d_fsdata;                 /* fs-specific data */
125 
126         struct list_head d_lru;         /* LRU list */
127         struct list_head d_child;       /* child of parent list */
128         struct list_head d_subdirs;     /* our children */
129         /*
130          * d_alias and d_rcu can share memory
131          */
132         union {
133                 struct hlist_node d_alias;      /* inode alias list */
134                 struct rcu_head d_rcu;
135         } d_u;
136 };
137 
138 /*
139  * dentry->d_lock spinlock nesting subclasses:
140  *
141  * 0: normal
142  * 1: nested
143  */
144 enum dentry_d_lock_class
145 {
146         DENTRY_D_LOCK_NORMAL, /* implicitly used by plain spin_lock() APIs. */
147         DENTRY_D_LOCK_NESTED
148 };
149 
150 struct dentry_operations {
151         int (*d_revalidate)(struct dentry *, unsigned int);
152         int (*d_weak_revalidate)(struct dentry *, unsigned int);
153         int (*d_hash)(const struct dentry *, struct qstr *);
154         int (*d_compare)(const struct dentry *, const struct dentry *,
155                         unsigned int, const char *, const struct qstr *);
156         int (*d_delete)(const struct dentry *);
157         void (*d_release)(struct dentry *);
158         void (*d_prune)(struct dentry *);
159         void (*d_iput)(struct dentry *, struct inode *);
160         char *(*d_dname)(struct dentry *, char *, int);
161         struct vfsmount *(*d_automount)(struct path *);
162         int (*d_manage)(struct dentry *, bool);
163         struct inode *(*d_select_inode)(struct dentry *, unsigned);
164 } ____cacheline_aligned;
165 
166 /*
167  * Locking rules for dentry_operations callbacks are to be found in
168  * Documentation/filesystems/Locking. Keep it updated!
169  *
170  * FUrther descriptions are found in Documentation/filesystems/vfs.txt.
171  * Keep it updated too!
172  */
173 
174 /* d_flags entries */
175 #define DCACHE_OP_HASH                  0x00000001
176 #define DCACHE_OP_COMPARE               0x00000002
177 #define DCACHE_OP_REVALIDATE            0x00000004
178 #define DCACHE_OP_DELETE                0x00000008
179 #define DCACHE_OP_PRUNE                 0x00000010
180 
181 #define DCACHE_DISCONNECTED             0x00000020
182      /* This dentry is possibly not currently connected to the dcache tree, in
183       * which case its parent will either be itself, or will have this flag as
184       * well.  nfsd will not use a dentry with this bit set, but will first
185       * endeavour to clear the bit either by discovering that it is connected,
186       * or by performing lookup operations.   Any filesystem which supports
187       * nfsd_operations MUST have a lookup function which, if it finds a
188       * directory inode with a DCACHE_DISCONNECTED dentry, will d_move that
189       * dentry into place and return that dentry rather than the passed one,
190       * typically using d_splice_alias. */
191 
192 #define DCACHE_REFERENCED               0x00000040 /* Recently used, don't discard. */
193 #define DCACHE_RCUACCESS                0x00000080 /* Entry has ever been RCU-visible */
194 
195 #define DCACHE_CANT_MOUNT               0x00000100
196 #define DCACHE_GENOCIDE                 0x00000200
197 #define DCACHE_SHRINK_LIST              0x00000400
198 
199 #define DCACHE_OP_WEAK_REVALIDATE       0x00000800
200 
201 #define DCACHE_NFSFS_RENAMED            0x00001000
202      /* this dentry has been "silly renamed" and has to be deleted on the last
203       * dput() */
204 #define DCACHE_COOKIE                   0x00002000 /* For use by dcookie subsystem */
205 #define DCACHE_FSNOTIFY_PARENT_WATCHED  0x00004000
206      /* Parent inode is watched by some fsnotify listener */
207 
208 #define DCACHE_DENTRY_KILLED            0x00008000
209 
210 #define DCACHE_MOUNTED                  0x00010000 /* is a mountpoint */
211 #define DCACHE_NEED_AUTOMOUNT           0x00020000 /* handle automount on this dir */
212 #define DCACHE_MANAGE_TRANSIT           0x00040000 /* manage transit from this dirent */
213 #define DCACHE_MANAGED_DENTRY \
214         (DCACHE_MOUNTED|DCACHE_NEED_AUTOMOUNT|DCACHE_MANAGE_TRANSIT)
215 
216 #define DCACHE_LRU_LIST                 0x00080000
217 
218 #define DCACHE_ENTRY_TYPE               0x00700000
219 #define DCACHE_MISS_TYPE                0x00000000 /* Negative dentry (maybe fallthru to nowhere) */
220 #define DCACHE_WHITEOUT_TYPE            0x00100000 /* Whiteout dentry (stop pathwalk) */
221 #define DCACHE_DIRECTORY_TYPE           0x00200000 /* Normal directory */
222 #define DCACHE_AUTODIR_TYPE             0x00300000 /* Lookupless directory (presumed automount) */
223 #define DCACHE_REGULAR_TYPE             0x00400000 /* Regular file type (or fallthru to such) */
224 #define DCACHE_SPECIAL_TYPE             0x00500000 /* Other file type (or fallthru to such) */
225 #define DCACHE_SYMLINK_TYPE             0x00600000 /* Symlink (or fallthru to such) */
226 
227 #define DCACHE_MAY_FREE                 0x00800000
228 #define DCACHE_FALLTHRU                 0x01000000 /* Fall through to lower layer */
229 #define DCACHE_OP_SELECT_INODE          0x02000000 /* Unioned entry: dcache op selects inode */
230 
231 extern seqlock_t rename_lock;
232 
233 /*
234  * These are the low-level FS interfaces to the dcache..
235  */
236 extern void d_instantiate(struct dentry *, struct inode *);
237 extern struct dentry * d_instantiate_unique(struct dentry *, struct inode *);
238 extern int d_instantiate_no_diralias(struct dentry *, struct inode *);
239 extern void __d_drop(struct dentry *dentry);
240 extern void d_drop(struct dentry *dentry);
241 extern void d_delete(struct dentry *);
242 extern void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op);
243 
244 /* allocate/de-allocate */
245 extern struct dentry * d_alloc(struct dentry *, const struct qstr *);
246 extern struct dentry * d_alloc_pseudo(struct super_block *, const struct qstr *);
247 extern struct dentry * d_splice_alias(struct inode *, struct dentry *);
248 extern struct dentry * d_add_ci(struct dentry *, struct inode *, struct qstr *);
249 extern struct dentry *d_find_any_alias(struct inode *inode);
250 extern struct dentry * d_obtain_alias(struct inode *);
251 extern struct dentry * d_obtain_root(struct inode *);
252 extern void shrink_dcache_sb(struct super_block *);
253 extern void shrink_dcache_parent(struct dentry *);
254 extern void shrink_dcache_for_umount(struct super_block *);
255 extern void d_invalidate(struct dentry *);
256 
257 /* only used at mount-time */
258 extern struct dentry * d_make_root(struct inode *);
259 
260 /* <clickety>-<click> the ramfs-type tree */
261 extern void d_genocide(struct dentry *);
262 
263 extern void d_tmpfile(struct dentry *, struct inode *);
264 
265 extern struct dentry *d_find_alias(struct inode *);
266 extern void d_prune_aliases(struct inode *);
267 
268 /* test whether we have any submounts in a subdir tree */
269 extern int have_submounts(struct dentry *);
270 
271 /*
272  * This adds the entry to the hash queues.
273  */
274 extern void d_rehash(struct dentry *);
275 
276 /**
277  * d_add - add dentry to hash queues
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  */
284  
285 static inline void d_add(struct dentry *entry, struct inode *inode)
286 {
287         d_instantiate(entry, inode);
288         d_rehash(entry);
289 }
290 
291 /**
292  * d_add_unique - add dentry to hash queues without aliasing
293  * @entry: dentry to add
294  * @inode: The inode to attach to this dentry
295  *
296  * This adds the entry to the hash queues and initializes @inode.
297  * The entry was actually filled in earlier during d_alloc().
298  */
299 static inline struct dentry *d_add_unique(struct dentry *entry, struct inode *inode)
300 {
301         struct dentry *res;
302 
303         res = d_instantiate_unique(entry, inode);
304         d_rehash(res != NULL ? res : entry);
305         return res;
306 }
307 
308 extern void dentry_update_name_case(struct dentry *, struct qstr *);
309 
310 /* used for rename() and baskets */
311 extern void d_move(struct dentry *, struct dentry *);
312 extern void d_exchange(struct dentry *, struct dentry *);
313 extern struct dentry *d_ancestor(struct dentry *, struct dentry *);
314 
315 /* appendix may either be NULL or be used for transname suffixes */
316 extern struct dentry *d_lookup(const struct dentry *, const struct qstr *);
317 extern struct dentry *d_hash_and_lookup(struct dentry *, struct qstr *);
318 extern struct dentry *__d_lookup(const struct dentry *, const struct qstr *);
319 extern struct dentry *__d_lookup_rcu(const struct dentry *parent,
320                                 const struct qstr *name, unsigned *seq);
321 
322 static inline unsigned d_count(const struct dentry *dentry)
323 {
324         return dentry->d_lockref.count;
325 }
326 
327 /*
328  * helper function for dentry_operations.d_dname() members
329  */
330 extern __printf(4, 5)
331 char *dynamic_dname(struct dentry *, char *, int, const char *, ...);
332 extern char *simple_dname(struct dentry *, char *, int);
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 *dentry_path_raw(struct dentry *, char *, int);
338 extern char *dentry_path(struct dentry *, char *, int);
339 
340 /* Allocation counts.. */
341 
342 /**
343  *      dget, dget_dlock -      get a reference to a dentry
344  *      @dentry: dentry to get a reference to
345  *
346  *      Given a dentry or %NULL pointer increment the reference count
347  *      if appropriate and return the dentry. A dentry will not be 
348  *      destroyed when it has references.
349  */
350 static inline struct dentry *dget_dlock(struct dentry *dentry)
351 {
352         if (dentry)
353                 dentry->d_lockref.count++;
354         return dentry;
355 }
356 
357 static inline struct dentry *dget(struct dentry *dentry)
358 {
359         if (dentry)
360                 lockref_get(&dentry->d_lockref);
361         return dentry;
362 }
363 
364 extern struct dentry *dget_parent(struct dentry *dentry);
365 
366 /**
367  *      d_unhashed -    is dentry hashed
368  *      @dentry: entry to check
369  *
370  *      Returns true if the dentry passed is not currently hashed.
371  */
372  
373 static inline int d_unhashed(const struct dentry *dentry)
374 {
375         return hlist_bl_unhashed(&dentry->d_hash);
376 }
377 
378 static inline int d_unlinked(const struct dentry *dentry)
379 {
380         return d_unhashed(dentry) && !IS_ROOT(dentry);
381 }
382 
383 static inline int cant_mount(const struct dentry *dentry)
384 {
385         return (dentry->d_flags & DCACHE_CANT_MOUNT);
386 }
387 
388 static inline void dont_mount(struct dentry *dentry)
389 {
390         spin_lock(&dentry->d_lock);
391         dentry->d_flags |= DCACHE_CANT_MOUNT;
392         spin_unlock(&dentry->d_lock);
393 }
394 
395 extern void dput(struct dentry *);
396 
397 static inline bool d_managed(const struct dentry *dentry)
398 {
399         return dentry->d_flags & DCACHE_MANAGED_DENTRY;
400 }
401 
402 static inline bool d_mountpoint(const struct dentry *dentry)
403 {
404         return dentry->d_flags & DCACHE_MOUNTED;
405 }
406 
407 /*
408  * Directory cache entry type accessor functions.
409  */
410 static inline unsigned __d_entry_type(const struct dentry *dentry)
411 {
412         return dentry->d_flags & DCACHE_ENTRY_TYPE;
413 }
414 
415 static inline bool d_is_miss(const struct dentry *dentry)
416 {
417         return __d_entry_type(dentry) == DCACHE_MISS_TYPE;
418 }
419 
420 static inline bool d_is_whiteout(const struct dentry *dentry)
421 {
422         return __d_entry_type(dentry) == DCACHE_WHITEOUT_TYPE;
423 }
424 
425 static inline bool d_can_lookup(const struct dentry *dentry)
426 {
427         return __d_entry_type(dentry) == DCACHE_DIRECTORY_TYPE;
428 }
429 
430 static inline bool d_is_autodir(const struct dentry *dentry)
431 {
432         return __d_entry_type(dentry) == DCACHE_AUTODIR_TYPE;
433 }
434 
435 static inline bool d_is_dir(const struct dentry *dentry)
436 {
437         return d_can_lookup(dentry) || d_is_autodir(dentry);
438 }
439 
440 static inline bool d_is_symlink(const struct dentry *dentry)
441 {
442         return __d_entry_type(dentry) == DCACHE_SYMLINK_TYPE;
443 }
444 
445 static inline bool d_is_reg(const struct dentry *dentry)
446 {
447         return __d_entry_type(dentry) == DCACHE_REGULAR_TYPE;
448 }
449 
450 static inline bool d_is_special(const struct dentry *dentry)
451 {
452         return __d_entry_type(dentry) == DCACHE_SPECIAL_TYPE;
453 }
454 
455 static inline bool d_is_file(const struct dentry *dentry)
456 {
457         return d_is_reg(dentry) || d_is_special(dentry);
458 }
459 
460 static inline bool d_is_negative(const struct dentry *dentry)
461 {
462         // TODO: check d_is_whiteout(dentry) also.
463         return d_is_miss(dentry);
464 }
465 
466 static inline bool d_is_positive(const struct dentry *dentry)
467 {
468         return !d_is_negative(dentry);
469 }
470 
471 /**
472  * d_really_is_negative - Determine if a dentry is really negative (ignoring fallthroughs)
473  * @dentry: The dentry in question
474  *
475  * Returns true if the dentry represents either an absent name or a name that
476  * doesn't map to an inode (ie. ->d_inode is NULL).  The dentry could represent
477  * a true miss, a whiteout that isn't represented by a 0,0 chardev or a
478  * fallthrough marker in an opaque directory.
479  *
480  * Note!  (1) This should be used *only* by a filesystem to examine its own
481  * dentries.  It should not be used to look at some other filesystem's
482  * dentries.  (2) It should also be used in combination with d_inode() to get
483  * the inode.  (3) The dentry may have something attached to ->d_lower and the
484  * type field of the flags may be set to something other than miss or whiteout.
485  */
486 static inline bool d_really_is_negative(const struct dentry *dentry)
487 {
488         return dentry->d_inode == NULL;
489 }
490 
491 /**
492  * d_really_is_positive - Determine if a dentry is really positive (ignoring fallthroughs)
493  * @dentry: The dentry in question
494  *
495  * Returns true if the dentry represents a name that maps to an inode
496  * (ie. ->d_inode is not NULL).  The dentry might still represent a whiteout if
497  * that is represented on medium as a 0,0 chardev.
498  *
499  * Note!  (1) This should be used *only* by a filesystem to examine its own
500  * dentries.  It should not be used to look at some other filesystem's
501  * dentries.  (2) It should also be used in combination with d_inode() to get
502  * the inode.
503  */
504 static inline bool d_really_is_positive(const struct dentry *dentry)
505 {
506         return dentry->d_inode != NULL;
507 }
508 
509 static inline int simple_positive(struct dentry *dentry)
510 {
511         return d_really_is_positive(dentry) && !d_unhashed(dentry);
512 }
513 
514 extern void d_set_fallthru(struct dentry *dentry);
515 
516 static inline bool d_is_fallthru(const struct dentry *dentry)
517 {
518         return dentry->d_flags & DCACHE_FALLTHRU;
519 }
520 
521 
522 extern int sysctl_vfs_cache_pressure;
523 
524 static inline unsigned long vfs_pressure_ratio(unsigned long val)
525 {
526         return mult_frac(val, sysctl_vfs_cache_pressure, 100);
527 }
528 
529 /**
530  * d_inode - Get the actual inode of this dentry
531  * @dentry: The dentry to query
532  *
533  * This is the helper normal filesystems should use to get at their own inodes
534  * in their own dentries and ignore the layering superimposed upon them.
535  */
536 static inline struct inode *d_inode(const struct dentry *dentry)
537 {
538         return dentry->d_inode;
539 }
540 
541 /**
542  * d_inode_rcu - Get the actual inode of this dentry with ACCESS_ONCE()
543  * @dentry: The dentry to query
544  *
545  * This is the helper normal filesystems should use to get at their own inodes
546  * in their own dentries and ignore the layering superimposed upon them.
547  */
548 static inline struct inode *d_inode_rcu(const struct dentry *dentry)
549 {
550         return ACCESS_ONCE(dentry->d_inode);
551 }
552 
553 /**
554  * d_backing_inode - Get upper or lower inode we should be using
555  * @upper: The upper layer
556  *
557  * This is the helper that should be used to get at the inode that will be used
558  * if this dentry were to be opened as a file.  The inode may be on the upper
559  * dentry or it may be on a lower dentry pinned by the upper.
560  *
561  * Normal filesystems should not use this to access their own inodes.
562  */
563 static inline struct inode *d_backing_inode(const struct dentry *upper)
564 {
565         struct inode *inode = upper->d_inode;
566 
567         return inode;
568 }
569 
570 /**
571  * d_backing_dentry - Get upper or lower dentry we should be using
572  * @upper: The upper layer
573  *
574  * This is the helper that should be used to get the dentry of the inode that
575  * will be used if this dentry were opened as a file.  It may be the upper
576  * dentry or it may be a lower dentry pinned by the upper.
577  *
578  * Normal filesystems should not use this to access their own dentries.
579  */
580 static inline struct dentry *d_backing_dentry(struct dentry *upper)
581 {
582         return upper;
583 }
584 
585 #endif  /* __LINUX_DCACHE_H */
586 

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