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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 } ____cacheline_aligned;
164 
165 /*
166  * Locking rules for dentry_operations callbacks are to be found in
167  * Documentation/filesystems/Locking. Keep it updated!
168  *
169  * FUrther descriptions are found in Documentation/filesystems/vfs.txt.
170  * Keep it updated too!
171  */
172 
173 /* d_flags entries */
174 #define DCACHE_OP_HASH                  0x00000001
175 #define DCACHE_OP_COMPARE               0x00000002
176 #define DCACHE_OP_REVALIDATE            0x00000004
177 #define DCACHE_OP_DELETE                0x00000008
178 #define DCACHE_OP_PRUNE                 0x00000010
179 
180 #define DCACHE_DISCONNECTED             0x00000020
181      /* This dentry is possibly not currently connected to the dcache tree, in
182       * which case its parent will either be itself, or will have this flag as
183       * well.  nfsd will not use a dentry with this bit set, but will first
184       * endeavour to clear the bit either by discovering that it is connected,
185       * or by performing lookup operations.   Any filesystem which supports
186       * nfsd_operations MUST have a lookup function which, if it finds a
187       * directory inode with a DCACHE_DISCONNECTED dentry, will d_move that
188       * dentry into place and return that dentry rather than the passed one,
189       * typically using d_splice_alias. */
190 
191 #define DCACHE_REFERENCED               0x00000040 /* Recently used, don't discard. */
192 #define DCACHE_RCUACCESS                0x00000080 /* Entry has ever been RCU-visible */
193 
194 #define DCACHE_CANT_MOUNT               0x00000100
195 #define DCACHE_GENOCIDE                 0x00000200
196 #define DCACHE_SHRINK_LIST              0x00000400
197 
198 #define DCACHE_OP_WEAK_REVALIDATE       0x00000800
199 
200 #define DCACHE_NFSFS_RENAMED            0x00001000
201      /* this dentry has been "silly renamed" and has to be deleted on the last
202       * dput() */
203 #define DCACHE_COOKIE                   0x00002000 /* For use by dcookie subsystem */
204 #define DCACHE_FSNOTIFY_PARENT_WATCHED  0x00004000
205      /* Parent inode is watched by some fsnotify listener */
206 
207 #define DCACHE_DENTRY_KILLED            0x00008000
208 
209 #define DCACHE_MOUNTED                  0x00010000 /* is a mountpoint */
210 #define DCACHE_NEED_AUTOMOUNT           0x00020000 /* handle automount on this dir */
211 #define DCACHE_MANAGE_TRANSIT           0x00040000 /* manage transit from this dirent */
212 #define DCACHE_MANAGED_DENTRY \
213         (DCACHE_MOUNTED|DCACHE_NEED_AUTOMOUNT|DCACHE_MANAGE_TRANSIT)
214 
215 #define DCACHE_LRU_LIST                 0x00080000
216 
217 #define DCACHE_ENTRY_TYPE               0x00700000
218 #define DCACHE_MISS_TYPE                0x00000000 /* Negative dentry (maybe fallthru to nowhere) */
219 #define DCACHE_WHITEOUT_TYPE            0x00100000 /* Whiteout dentry (stop pathwalk) */
220 #define DCACHE_DIRECTORY_TYPE           0x00200000 /* Normal directory */
221 #define DCACHE_AUTODIR_TYPE             0x00300000 /* Lookupless directory (presumed automount) */
222 #define DCACHE_REGULAR_TYPE             0x00400000 /* Regular file type (or fallthru to such) */
223 #define DCACHE_SPECIAL_TYPE             0x00500000 /* Other file type (or fallthru to such) */
224 #define DCACHE_SYMLINK_TYPE             0x00600000 /* Symlink (or fallthru to such) */
225 
226 #define DCACHE_MAY_FREE                 0x00800000
227 #define DCACHE_FALLTHRU                 0x01000000 /* Fall through to lower layer */
228 
229 extern seqlock_t rename_lock;
230 
231 /*
232  * These are the low-level FS interfaces to the dcache..
233  */
234 extern void d_instantiate(struct dentry *, struct inode *);
235 extern struct dentry * d_instantiate_unique(struct dentry *, struct inode *);
236 extern int d_instantiate_no_diralias(struct dentry *, struct inode *);
237 extern void __d_drop(struct dentry *dentry);
238 extern void d_drop(struct dentry *dentry);
239 extern void d_delete(struct dentry *);
240 extern void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op);
241 
242 /* allocate/de-allocate */
243 extern struct dentry * d_alloc(struct dentry *, const struct qstr *);
244 extern struct dentry * d_alloc_pseudo(struct super_block *, const struct qstr *);
245 extern struct dentry * d_splice_alias(struct inode *, struct dentry *);
246 extern struct dentry * d_add_ci(struct dentry *, struct inode *, struct qstr *);
247 extern struct dentry *d_find_any_alias(struct inode *inode);
248 extern struct dentry * d_obtain_alias(struct inode *);
249 extern struct dentry * d_obtain_root(struct inode *);
250 extern void shrink_dcache_sb(struct super_block *);
251 extern void shrink_dcache_parent(struct dentry *);
252 extern void shrink_dcache_for_umount(struct super_block *);
253 extern void d_invalidate(struct dentry *);
254 
255 /* only used at mount-time */
256 extern struct dentry * d_make_root(struct inode *);
257 
258 /* <clickety>-<click> the ramfs-type tree */
259 extern void d_genocide(struct dentry *);
260 
261 extern void d_tmpfile(struct dentry *, struct inode *);
262 
263 extern struct dentry *d_find_alias(struct inode *);
264 extern void d_prune_aliases(struct inode *);
265 
266 /* test whether we have any submounts in a subdir tree */
267 extern int have_submounts(struct dentry *);
268 
269 /*
270  * This adds the entry to the hash queues.
271  */
272 extern void d_rehash(struct dentry *);
273 
274 /**
275  * d_add - add dentry to hash queues
276  * @entry: dentry to add
277  * @inode: The inode to attach to this dentry
278  *
279  * This adds the entry to the hash queues and initializes @inode.
280  * The entry was actually filled in earlier during d_alloc().
281  */
282  
283 static inline void d_add(struct dentry *entry, struct inode *inode)
284 {
285         d_instantiate(entry, inode);
286         d_rehash(entry);
287 }
288 
289 /**
290  * d_add_unique - add dentry to hash queues without aliasing
291  * @entry: dentry to add
292  * @inode: The inode to attach to this dentry
293  *
294  * This adds the entry to the hash queues and initializes @inode.
295  * The entry was actually filled in earlier during d_alloc().
296  */
297 static inline struct dentry *d_add_unique(struct dentry *entry, struct inode *inode)
298 {
299         struct dentry *res;
300 
301         res = d_instantiate_unique(entry, inode);
302         d_rehash(res != NULL ? res : entry);
303         return res;
304 }
305 
306 extern void dentry_update_name_case(struct dentry *, struct qstr *);
307 
308 /* used for rename() and baskets */
309 extern void d_move(struct dentry *, struct dentry *);
310 extern void d_exchange(struct dentry *, struct dentry *);
311 extern struct dentry *d_ancestor(struct dentry *, struct dentry *);
312 
313 /* appendix may either be NULL or be used for transname suffixes */
314 extern struct dentry *d_lookup(const struct dentry *, const struct qstr *);
315 extern struct dentry *d_hash_and_lookup(struct dentry *, struct qstr *);
316 extern struct dentry *__d_lookup(const struct dentry *, const struct qstr *);
317 extern struct dentry *__d_lookup_rcu(const struct dentry *parent,
318                                 const struct qstr *name, unsigned *seq);
319 
320 static inline unsigned d_count(const struct dentry *dentry)
321 {
322         return dentry->d_lockref.count;
323 }
324 
325 /*
326  * helper function for dentry_operations.d_dname() members
327  */
328 extern char *dynamic_dname(struct dentry *, char *, int, const char *, ...);
329 extern char *simple_dname(struct dentry *, char *, int);
330 
331 extern char *__d_path(const struct path *, const struct path *, char *, int);
332 extern char *d_absolute_path(const struct path *, char *, int);
333 extern char *d_path(const struct path *, char *, int);
334 extern char *dentry_path_raw(struct dentry *, char *, int);
335 extern char *dentry_path(struct dentry *, char *, int);
336 
337 /* Allocation counts.. */
338 
339 /**
340  *      dget, dget_dlock -      get a reference to a dentry
341  *      @dentry: dentry to get a reference to
342  *
343  *      Given a dentry or %NULL pointer increment the reference count
344  *      if appropriate and return the dentry. A dentry will not be 
345  *      destroyed when it has references.
346  */
347 static inline struct dentry *dget_dlock(struct dentry *dentry)
348 {
349         if (dentry)
350                 dentry->d_lockref.count++;
351         return dentry;
352 }
353 
354 static inline struct dentry *dget(struct dentry *dentry)
355 {
356         if (dentry)
357                 lockref_get(&dentry->d_lockref);
358         return dentry;
359 }
360 
361 extern struct dentry *dget_parent(struct dentry *dentry);
362 
363 /**
364  *      d_unhashed -    is dentry hashed
365  *      @dentry: entry to check
366  *
367  *      Returns true if the dentry passed is not currently hashed.
368  */
369  
370 static inline int d_unhashed(const struct dentry *dentry)
371 {
372         return hlist_bl_unhashed(&dentry->d_hash);
373 }
374 
375 static inline int d_unlinked(const struct dentry *dentry)
376 {
377         return d_unhashed(dentry) && !IS_ROOT(dentry);
378 }
379 
380 static inline int cant_mount(const struct dentry *dentry)
381 {
382         return (dentry->d_flags & DCACHE_CANT_MOUNT);
383 }
384 
385 static inline void dont_mount(struct dentry *dentry)
386 {
387         spin_lock(&dentry->d_lock);
388         dentry->d_flags |= DCACHE_CANT_MOUNT;
389         spin_unlock(&dentry->d_lock);
390 }
391 
392 extern void dput(struct dentry *);
393 
394 static inline bool d_managed(const struct dentry *dentry)
395 {
396         return dentry->d_flags & DCACHE_MANAGED_DENTRY;
397 }
398 
399 static inline bool d_mountpoint(const struct dentry *dentry)
400 {
401         return dentry->d_flags & DCACHE_MOUNTED;
402 }
403 
404 /*
405  * Directory cache entry type accessor functions.
406  */
407 static inline void __d_set_type(struct dentry *dentry, unsigned type)
408 {
409         dentry->d_flags = (dentry->d_flags & ~DCACHE_ENTRY_TYPE) | type;
410 }
411 
412 static inline void __d_clear_type(struct dentry *dentry)
413 {
414         __d_set_type(dentry, DCACHE_MISS_TYPE);
415 }
416 
417 static inline void d_set_type(struct dentry *dentry, unsigned type)
418 {
419         spin_lock(&dentry->d_lock);
420         __d_set_type(dentry, type);
421         spin_unlock(&dentry->d_lock);
422 }
423 
424 static inline unsigned __d_entry_type(const struct dentry *dentry)
425 {
426         return dentry->d_flags & DCACHE_ENTRY_TYPE;
427 }
428 
429 static inline bool d_is_miss(const struct dentry *dentry)
430 {
431         return __d_entry_type(dentry) == DCACHE_MISS_TYPE;
432 }
433 
434 static inline bool d_is_whiteout(const struct dentry *dentry)
435 {
436         return __d_entry_type(dentry) == DCACHE_WHITEOUT_TYPE;
437 }
438 
439 static inline bool d_can_lookup(const struct dentry *dentry)
440 {
441         return __d_entry_type(dentry) == DCACHE_DIRECTORY_TYPE;
442 }
443 
444 static inline bool d_is_autodir(const struct dentry *dentry)
445 {
446         return __d_entry_type(dentry) == DCACHE_AUTODIR_TYPE;
447 }
448 
449 static inline bool d_is_dir(const struct dentry *dentry)
450 {
451         return d_can_lookup(dentry) || d_is_autodir(dentry);
452 }
453 
454 static inline bool d_is_symlink(const struct dentry *dentry)
455 {
456         return __d_entry_type(dentry) == DCACHE_SYMLINK_TYPE;
457 }
458 
459 static inline bool d_is_reg(const struct dentry *dentry)
460 {
461         return __d_entry_type(dentry) == DCACHE_REGULAR_TYPE;
462 }
463 
464 static inline bool d_is_special(const struct dentry *dentry)
465 {
466         return __d_entry_type(dentry) == DCACHE_SPECIAL_TYPE;
467 }
468 
469 static inline bool d_is_file(const struct dentry *dentry)
470 {
471         return d_is_reg(dentry) || d_is_special(dentry);
472 }
473 
474 static inline bool d_is_negative(const struct dentry *dentry)
475 {
476         // TODO: check d_is_whiteout(dentry) also.
477         return d_is_miss(dentry);
478 }
479 
480 static inline bool d_is_positive(const struct dentry *dentry)
481 {
482         return !d_is_negative(dentry);
483 }
484 
485 extern void d_set_fallthru(struct dentry *dentry);
486 
487 static inline bool d_is_fallthru(const struct dentry *dentry)
488 {
489         return dentry->d_flags & DCACHE_FALLTHRU;
490 }
491 
492 
493 extern int sysctl_vfs_cache_pressure;
494 
495 static inline unsigned long vfs_pressure_ratio(unsigned long val)
496 {
497         return mult_frac(val, sysctl_vfs_cache_pressure, 100);
498 }
499 
500 /**
501  * d_inode - Get the actual inode of this dentry
502  * @dentry: The dentry to query
503  *
504  * This is the helper normal filesystems should use to get at their own inodes
505  * in their own dentries and ignore the layering superimposed upon them.
506  */
507 static inline struct inode *d_inode(const struct dentry *dentry)
508 {
509         return dentry->d_inode;
510 }
511 
512 /**
513  * d_inode_rcu - Get the actual inode of this dentry with ACCESS_ONCE()
514  * @dentry: The dentry to query
515  *
516  * This is the helper normal filesystems should use to get at their own inodes
517  * in their own dentries and ignore the layering superimposed upon them.
518  */
519 static inline struct inode *d_inode_rcu(const struct dentry *dentry)
520 {
521         return ACCESS_ONCE(dentry->d_inode);
522 }
523 
524 /**
525  * d_backing_inode - Get upper or lower inode we should be using
526  * @upper: The upper layer
527  *
528  * This is the helper that should be used to get at the inode that will be used
529  * if this dentry were to be opened as a file.  The inode may be on the upper
530  * dentry or it may be on a lower dentry pinned by the upper.
531  *
532  * Normal filesystems should not use this to access their own inodes.
533  */
534 static inline struct inode *d_backing_inode(const struct dentry *upper)
535 {
536         struct inode *inode = upper->d_inode;
537 
538         return inode;
539 }
540 
541 /**
542  * d_backing_dentry - Get upper or lower dentry we should be using
543  * @upper: The upper layer
544  *
545  * This is the helper that should be used to get the dentry of the inode that
546  * will be used if this dentry were opened as a file.  It may be the upper
547  * dentry or it may be a lower dentry pinned by the upper.
548  *
549  * Normal filesystems should not use this to access their own dentries.
550  */
551 static inline struct dentry *d_backing_dentry(struct dentry *upper)
552 {
553         return upper;
554 }
555 
556 #endif  /* __LINUX_DCACHE_H */
557 

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