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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         struct dentry *(*d_real)(struct dentry *, struct inode *);
165 } ____cacheline_aligned;
166 
167 /*
168  * Locking rules for dentry_operations callbacks are to be found in
169  * Documentation/filesystems/Locking. Keep it updated!
170  *
171  * FUrther descriptions are found in Documentation/filesystems/vfs.txt.
172  * Keep it updated too!
173  */
174 
175 /* d_flags entries */
176 #define DCACHE_OP_HASH                  0x00000001
177 #define DCACHE_OP_COMPARE               0x00000002
178 #define DCACHE_OP_REVALIDATE            0x00000004
179 #define DCACHE_OP_DELETE                0x00000008
180 #define DCACHE_OP_PRUNE                 0x00000010
181 
182 #define DCACHE_DISCONNECTED             0x00000020
183      /* This dentry is possibly not currently connected to the dcache tree, in
184       * which case its parent will either be itself, or will have this flag as
185       * well.  nfsd will not use a dentry with this bit set, but will first
186       * endeavour to clear the bit either by discovering that it is connected,
187       * or by performing lookup operations.   Any filesystem which supports
188       * nfsd_operations MUST have a lookup function which, if it finds a
189       * directory inode with a DCACHE_DISCONNECTED dentry, will d_move that
190       * dentry into place and return that dentry rather than the passed one,
191       * typically using d_splice_alias. */
192 
193 #define DCACHE_REFERENCED               0x00000040 /* Recently used, don't discard. */
194 #define DCACHE_RCUACCESS                0x00000080 /* Entry has ever been RCU-visible */
195 
196 #define DCACHE_CANT_MOUNT               0x00000100
197 #define DCACHE_GENOCIDE                 0x00000200
198 #define DCACHE_SHRINK_LIST              0x00000400
199 
200 #define DCACHE_OP_WEAK_REVALIDATE       0x00000800
201 
202 #define DCACHE_NFSFS_RENAMED            0x00001000
203      /* this dentry has been "silly renamed" and has to be deleted on the last
204       * dput() */
205 #define DCACHE_COOKIE                   0x00002000 /* For use by dcookie subsystem */
206 #define DCACHE_FSNOTIFY_PARENT_WATCHED  0x00004000
207      /* Parent inode is watched by some fsnotify listener */
208 
209 #define DCACHE_DENTRY_KILLED            0x00008000
210 
211 #define DCACHE_MOUNTED                  0x00010000 /* is a mountpoint */
212 #define DCACHE_NEED_AUTOMOUNT           0x00020000 /* handle automount on this dir */
213 #define DCACHE_MANAGE_TRANSIT           0x00040000 /* manage transit from this dirent */
214 #define DCACHE_MANAGED_DENTRY \
215         (DCACHE_MOUNTED|DCACHE_NEED_AUTOMOUNT|DCACHE_MANAGE_TRANSIT)
216 
217 #define DCACHE_LRU_LIST                 0x00080000
218 
219 #define DCACHE_ENTRY_TYPE               0x00700000
220 #define DCACHE_MISS_TYPE                0x00000000 /* Negative dentry (maybe fallthru to nowhere) */
221 #define DCACHE_WHITEOUT_TYPE            0x00100000 /* Whiteout dentry (stop pathwalk) */
222 #define DCACHE_DIRECTORY_TYPE           0x00200000 /* Normal directory */
223 #define DCACHE_AUTODIR_TYPE             0x00300000 /* Lookupless directory (presumed automount) */
224 #define DCACHE_REGULAR_TYPE             0x00400000 /* Regular file type (or fallthru to such) */
225 #define DCACHE_SPECIAL_TYPE             0x00500000 /* Other file type (or fallthru to such) */
226 #define DCACHE_SYMLINK_TYPE             0x00600000 /* Symlink (or fallthru to such) */
227 
228 #define DCACHE_MAY_FREE                 0x00800000
229 #define DCACHE_FALLTHRU                 0x01000000 /* Fall through to lower layer */
230 #define DCACHE_OP_SELECT_INODE          0x02000000 /* Unioned entry: dcache op selects inode */
231 
232 #define DCACHE_ENCRYPTED_WITH_KEY       0x04000000 /* dir is encrypted with a valid key */
233 #define DCACHE_OP_REAL                  0x08000000
234 
235 extern seqlock_t rename_lock;
236 
237 /*
238  * These are the low-level FS interfaces to the dcache..
239  */
240 extern void d_instantiate(struct dentry *, struct inode *);
241 extern struct dentry * d_instantiate_unique(struct dentry *, struct inode *);
242 extern int d_instantiate_no_diralias(struct dentry *, struct inode *);
243 extern void __d_drop(struct dentry *dentry);
244 extern void d_drop(struct dentry *dentry);
245 extern void d_delete(struct dentry *);
246 extern void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op);
247 
248 /* allocate/de-allocate */
249 extern struct dentry * d_alloc(struct dentry *, const struct qstr *);
250 extern struct dentry * d_alloc_pseudo(struct super_block *, const struct qstr *);
251 extern struct dentry * d_splice_alias(struct inode *, struct dentry *);
252 extern struct dentry * d_add_ci(struct dentry *, struct inode *, struct qstr *);
253 extern struct dentry * d_exact_alias(struct dentry *, struct inode *);
254 extern struct dentry *d_find_any_alias(struct inode *inode);
255 extern struct dentry * d_obtain_alias(struct inode *);
256 extern struct dentry * d_obtain_root(struct inode *);
257 extern void shrink_dcache_sb(struct super_block *);
258 extern void shrink_dcache_parent(struct dentry *);
259 extern void shrink_dcache_for_umount(struct super_block *);
260 extern void d_invalidate(struct dentry *);
261 
262 /* only used at mount-time */
263 extern struct dentry * d_make_root(struct inode *);
264 
265 /* <clickety>-<click> the ramfs-type tree */
266 extern void d_genocide(struct dentry *);
267 
268 extern void d_tmpfile(struct dentry *, struct inode *);
269 
270 extern struct dentry *d_find_alias(struct inode *);
271 extern void d_prune_aliases(struct inode *);
272 
273 /* test whether we have any submounts in a subdir tree */
274 extern int have_submounts(struct dentry *);
275 
276 /*
277  * This adds the entry to the hash queues.
278  */
279 extern void d_rehash(struct dentry *);
280  
281 extern void d_add(struct dentry *, struct inode *);
282 
283 extern void dentry_update_name_case(struct dentry *, struct qstr *);
284 
285 /* used for rename() and baskets */
286 extern void d_move(struct dentry *, struct dentry *);
287 extern void d_exchange(struct dentry *, struct dentry *);
288 extern struct dentry *d_ancestor(struct dentry *, struct dentry *);
289 
290 /* appendix may either be NULL or be used for transname suffixes */
291 extern struct dentry *d_lookup(const struct dentry *, const struct qstr *);
292 extern struct dentry *d_hash_and_lookup(struct dentry *, struct qstr *);
293 extern struct dentry *__d_lookup(const struct dentry *, const struct qstr *);
294 extern struct dentry *__d_lookup_rcu(const struct dentry *parent,
295                                 const struct qstr *name, unsigned *seq);
296 
297 static inline unsigned d_count(const struct dentry *dentry)
298 {
299         return dentry->d_lockref.count;
300 }
301 
302 /*
303  * helper function for dentry_operations.d_dname() members
304  */
305 extern __printf(4, 5)
306 char *dynamic_dname(struct dentry *, char *, int, const char *, ...);
307 extern char *simple_dname(struct dentry *, char *, int);
308 
309 extern char *__d_path(const struct path *, const struct path *, char *, int);
310 extern char *d_absolute_path(const struct path *, char *, int);
311 extern char *d_path(const struct path *, char *, int);
312 extern char *dentry_path_raw(struct dentry *, char *, int);
313 extern char *dentry_path(struct dentry *, char *, int);
314 
315 /* Allocation counts.. */
316 
317 /**
318  *      dget, dget_dlock -      get a reference to a dentry
319  *      @dentry: dentry to get a reference to
320  *
321  *      Given a dentry or %NULL pointer increment the reference count
322  *      if appropriate and return the dentry. A dentry will not be 
323  *      destroyed when it has references.
324  */
325 static inline struct dentry *dget_dlock(struct dentry *dentry)
326 {
327         if (dentry)
328                 dentry->d_lockref.count++;
329         return dentry;
330 }
331 
332 static inline struct dentry *dget(struct dentry *dentry)
333 {
334         if (dentry)
335                 lockref_get(&dentry->d_lockref);
336         return dentry;
337 }
338 
339 extern struct dentry *dget_parent(struct dentry *dentry);
340 
341 /**
342  *      d_unhashed -    is dentry hashed
343  *      @dentry: entry to check
344  *
345  *      Returns true if the dentry passed is not currently hashed.
346  */
347  
348 static inline int d_unhashed(const struct dentry *dentry)
349 {
350         return hlist_bl_unhashed(&dentry->d_hash);
351 }
352 
353 static inline int d_unlinked(const struct dentry *dentry)
354 {
355         return d_unhashed(dentry) && !IS_ROOT(dentry);
356 }
357 
358 static inline int cant_mount(const struct dentry *dentry)
359 {
360         return (dentry->d_flags & DCACHE_CANT_MOUNT);
361 }
362 
363 static inline void dont_mount(struct dentry *dentry)
364 {
365         spin_lock(&dentry->d_lock);
366         dentry->d_flags |= DCACHE_CANT_MOUNT;
367         spin_unlock(&dentry->d_lock);
368 }
369 
370 extern void dput(struct dentry *);
371 
372 static inline bool d_managed(const struct dentry *dentry)
373 {
374         return dentry->d_flags & DCACHE_MANAGED_DENTRY;
375 }
376 
377 static inline bool d_mountpoint(const struct dentry *dentry)
378 {
379         return dentry->d_flags & DCACHE_MOUNTED;
380 }
381 
382 /*
383  * Directory cache entry type accessor functions.
384  */
385 static inline unsigned __d_entry_type(const struct dentry *dentry)
386 {
387         return dentry->d_flags & DCACHE_ENTRY_TYPE;
388 }
389 
390 static inline bool d_is_miss(const struct dentry *dentry)
391 {
392         return __d_entry_type(dentry) == DCACHE_MISS_TYPE;
393 }
394 
395 static inline bool d_is_whiteout(const struct dentry *dentry)
396 {
397         return __d_entry_type(dentry) == DCACHE_WHITEOUT_TYPE;
398 }
399 
400 static inline bool d_can_lookup(const struct dentry *dentry)
401 {
402         return __d_entry_type(dentry) == DCACHE_DIRECTORY_TYPE;
403 }
404 
405 static inline bool d_is_autodir(const struct dentry *dentry)
406 {
407         return __d_entry_type(dentry) == DCACHE_AUTODIR_TYPE;
408 }
409 
410 static inline bool d_is_dir(const struct dentry *dentry)
411 {
412         return d_can_lookup(dentry) || d_is_autodir(dentry);
413 }
414 
415 static inline bool d_is_symlink(const struct dentry *dentry)
416 {
417         return __d_entry_type(dentry) == DCACHE_SYMLINK_TYPE;
418 }
419 
420 static inline bool d_is_reg(const struct dentry *dentry)
421 {
422         return __d_entry_type(dentry) == DCACHE_REGULAR_TYPE;
423 }
424 
425 static inline bool d_is_special(const struct dentry *dentry)
426 {
427         return __d_entry_type(dentry) == DCACHE_SPECIAL_TYPE;
428 }
429 
430 static inline bool d_is_file(const struct dentry *dentry)
431 {
432         return d_is_reg(dentry) || d_is_special(dentry);
433 }
434 
435 static inline bool d_is_negative(const struct dentry *dentry)
436 {
437         // TODO: check d_is_whiteout(dentry) also.
438         return d_is_miss(dentry);
439 }
440 
441 static inline bool d_is_positive(const struct dentry *dentry)
442 {
443         return !d_is_negative(dentry);
444 }
445 
446 /**
447  * d_really_is_negative - Determine if a dentry is really negative (ignoring fallthroughs)
448  * @dentry: The dentry in question
449  *
450  * Returns true if the dentry represents either an absent name or a name that
451  * doesn't map to an inode (ie. ->d_inode is NULL).  The dentry could represent
452  * a true miss, a whiteout that isn't represented by a 0,0 chardev or a
453  * fallthrough marker in an opaque directory.
454  *
455  * Note!  (1) This should be used *only* by a filesystem to examine its own
456  * dentries.  It should not be used to look at some other filesystem's
457  * dentries.  (2) It should also be used in combination with d_inode() to get
458  * the inode.  (3) The dentry may have something attached to ->d_lower and the
459  * type field of the flags may be set to something other than miss or whiteout.
460  */
461 static inline bool d_really_is_negative(const struct dentry *dentry)
462 {
463         return dentry->d_inode == NULL;
464 }
465 
466 /**
467  * d_really_is_positive - Determine if a dentry is really positive (ignoring fallthroughs)
468  * @dentry: The dentry in question
469  *
470  * Returns true if the dentry represents a name that maps to an inode
471  * (ie. ->d_inode is not NULL).  The dentry might still represent a whiteout if
472  * that is represented on medium as a 0,0 chardev.
473  *
474  * Note!  (1) This should be used *only* by a filesystem to examine its own
475  * dentries.  It should not be used to look at some other filesystem's
476  * dentries.  (2) It should also be used in combination with d_inode() to get
477  * the inode.
478  */
479 static inline bool d_really_is_positive(const struct dentry *dentry)
480 {
481         return dentry->d_inode != NULL;
482 }
483 
484 static inline int simple_positive(struct dentry *dentry)
485 {
486         return d_really_is_positive(dentry) && !d_unhashed(dentry);
487 }
488 
489 extern void d_set_fallthru(struct dentry *dentry);
490 
491 static inline bool d_is_fallthru(const struct dentry *dentry)
492 {
493         return dentry->d_flags & DCACHE_FALLTHRU;
494 }
495 
496 
497 extern int sysctl_vfs_cache_pressure;
498 
499 static inline unsigned long vfs_pressure_ratio(unsigned long val)
500 {
501         return mult_frac(val, sysctl_vfs_cache_pressure, 100);
502 }
503 
504 /**
505  * d_inode - Get the actual inode of this dentry
506  * @dentry: The dentry to query
507  *
508  * This is the helper normal filesystems should use to get at their own inodes
509  * in their own dentries and ignore the layering superimposed upon them.
510  */
511 static inline struct inode *d_inode(const struct dentry *dentry)
512 {
513         return dentry->d_inode;
514 }
515 
516 /**
517  * d_inode_rcu - Get the actual inode of this dentry with ACCESS_ONCE()
518  * @dentry: The dentry to query
519  *
520  * This is the helper normal filesystems should use to get at their own inodes
521  * in their own dentries and ignore the layering superimposed upon them.
522  */
523 static inline struct inode *d_inode_rcu(const struct dentry *dentry)
524 {
525         return ACCESS_ONCE(dentry->d_inode);
526 }
527 
528 /**
529  * d_backing_inode - Get upper or lower inode we should be using
530  * @upper: The upper layer
531  *
532  * This is the helper that should be used to get at the inode that will be used
533  * if this dentry were to be opened as a file.  The inode may be on the upper
534  * dentry or it may be on a lower dentry pinned by the upper.
535  *
536  * Normal filesystems should not use this to access their own inodes.
537  */
538 static inline struct inode *d_backing_inode(const struct dentry *upper)
539 {
540         struct inode *inode = upper->d_inode;
541 
542         return inode;
543 }
544 
545 /**
546  * d_backing_dentry - Get upper or lower dentry we should be using
547  * @upper: The upper layer
548  *
549  * This is the helper that should be used to get the dentry of the inode that
550  * will be used if this dentry were opened as a file.  It may be the upper
551  * dentry or it may be a lower dentry pinned by the upper.
552  *
553  * Normal filesystems should not use this to access their own dentries.
554  */
555 static inline struct dentry *d_backing_dentry(struct dentry *upper)
556 {
557         return upper;
558 }
559 
560 static inline struct dentry *d_real(struct dentry *dentry)
561 {
562         if (unlikely(dentry->d_flags & DCACHE_OP_REAL))
563                 return dentry->d_op->d_real(dentry, NULL);
564         else
565                 return dentry;
566 }
567 
568 static inline struct inode *vfs_select_inode(struct dentry *dentry,
569                                              unsigned open_flags)
570 {
571         struct inode *inode = d_inode(dentry);
572 
573         if (inode && unlikely(dentry->d_flags & DCACHE_OP_SELECT_INODE))
574                 inode = dentry->d_op->d_select_inode(dentry, open_flags);
575 
576         return inode;
577 }
578 
579 
580 #endif  /* __LINUX_DCACHE_H */
581 

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