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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 nameidata;
 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 #define hashlen_hash(hashlen) ((u32) (hashlen))
 57 #define hashlen_len(hashlen)  ((u32)((hashlen) >> 32))
 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         /*
128          * d_child and d_rcu can share memory
129          */
130         union {
131                 struct list_head d_child;       /* child of parent list */
132                 struct rcu_head d_rcu;
133         } d_u;
134         struct list_head d_subdirs;     /* our children */
135         struct hlist_node d_alias;      /* inode alias list */
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 */
219 #define DCACHE_DIRECTORY_TYPE           0x00100000 /* Normal directory */
220 #define DCACHE_AUTODIR_TYPE             0x00200000 /* Lookupless directory (presumed automount) */
221 #define DCACHE_SYMLINK_TYPE             0x00300000 /* Symlink */
222 #define DCACHE_FILE_TYPE                0x00400000 /* Other file type */
223 
224 #define DCACHE_MAY_FREE                 0x00800000
225 
226 extern seqlock_t rename_lock;
227 
228 static inline int dname_external(const struct dentry *dentry)
229 {
230         return dentry->d_name.name != dentry->d_iname;
231 }
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 struct dentry * d_materialise_unique(struct dentry *, struct inode *);
239 extern int d_instantiate_no_diralias(struct dentry *, struct inode *);
240 extern void __d_drop(struct dentry *dentry);
241 extern void d_drop(struct dentry *dentry);
242 extern void d_delete(struct dentry *);
243 extern void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op);
244 
245 /* allocate/de-allocate */
246 extern struct dentry * d_alloc(struct dentry *, const struct qstr *);
247 extern struct dentry * d_alloc_pseudo(struct super_block *, const struct qstr *);
248 extern struct dentry * d_splice_alias(struct inode *, struct dentry *);
249 extern struct dentry * d_add_ci(struct dentry *, struct inode *, struct qstr *);
250 extern struct dentry *d_find_any_alias(struct inode *inode);
251 extern struct dentry * d_obtain_alias(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 int 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 extern int check_submounts_and_drop(struct dentry *);
271 
272 /*
273  * This adds the entry to the hash queues.
274  */
275 extern void d_rehash(struct dentry *);
276 
277 /**
278  * d_add - add dentry to hash queues
279  * @entry: dentry to add
280  * @inode: The inode to attach to this dentry
281  *
282  * This adds the entry to the hash queues and initializes @inode.
283  * The entry was actually filled in earlier during d_alloc().
284  */
285  
286 static inline void d_add(struct dentry *entry, struct inode *inode)
287 {
288         d_instantiate(entry, inode);
289         d_rehash(entry);
290 }
291 
292 /**
293  * d_add_unique - add dentry to hash queues without aliasing
294  * @entry: dentry to add
295  * @inode: The inode to attach to this dentry
296  *
297  * This adds the entry to the hash queues and initializes @inode.
298  * The entry was actually filled in earlier during d_alloc().
299  */
300 static inline struct dentry *d_add_unique(struct dentry *entry, struct inode *inode)
301 {
302         struct dentry *res;
303 
304         res = d_instantiate_unique(entry, inode);
305         d_rehash(res != NULL ? res : entry);
306         return res;
307 }
308 
309 extern void dentry_update_name_case(struct dentry *, struct qstr *);
310 
311 /* used for rename() and baskets */
312 extern void d_move(struct dentry *, struct dentry *);
313 extern void d_exchange(struct dentry *, struct dentry *);
314 extern struct dentry *d_ancestor(struct dentry *, struct dentry *);
315 
316 /* appendix may either be NULL or be used for transname suffixes */
317 extern struct dentry *d_lookup(const struct dentry *, const struct qstr *);
318 extern struct dentry *d_hash_and_lookup(struct dentry *, struct qstr *);
319 extern struct dentry *__d_lookup(const struct dentry *, const struct qstr *);
320 extern struct dentry *__d_lookup_rcu(const struct dentry *parent,
321                                 const struct qstr *name, unsigned *seq);
322 
323 static inline unsigned d_count(const struct dentry *dentry)
324 {
325         return dentry->d_lockref.count;
326 }
327 
328 /* validate "insecure" dentry pointer */
329 extern int d_validate(struct dentry *, struct dentry *);
330 
331 /*
332  * helper function for dentry_operations.d_dname() members
333  */
334 extern char *dynamic_dname(struct dentry *, char *, int, const char *, ...);
335 extern char *simple_dname(struct dentry *, char *, int);
336 
337 extern char *__d_path(const struct path *, const struct path *, char *, int);
338 extern char *d_absolute_path(const struct path *, char *, int);
339 extern char *d_path(const struct path *, char *, int);
340 extern char *dentry_path_raw(struct dentry *, char *, int);
341 extern char *dentry_path(struct dentry *, char *, int);
342 
343 /* Allocation counts.. */
344 
345 /**
346  *      dget, dget_dlock -      get a reference to a dentry
347  *      @dentry: dentry to get a reference to
348  *
349  *      Given a dentry or %NULL pointer increment the reference count
350  *      if appropriate and return the dentry. A dentry will not be 
351  *      destroyed when it has references.
352  */
353 static inline struct dentry *dget_dlock(struct dentry *dentry)
354 {
355         if (dentry)
356                 dentry->d_lockref.count++;
357         return dentry;
358 }
359 
360 static inline struct dentry *dget(struct dentry *dentry)
361 {
362         if (dentry)
363                 lockref_get(&dentry->d_lockref);
364         return dentry;
365 }
366 
367 extern struct dentry *dget_parent(struct dentry *dentry);
368 
369 /**
370  *      d_unhashed -    is dentry hashed
371  *      @dentry: entry to check
372  *
373  *      Returns true if the dentry passed is not currently hashed.
374  */
375  
376 static inline int d_unhashed(const struct dentry *dentry)
377 {
378         return hlist_bl_unhashed(&dentry->d_hash);
379 }
380 
381 static inline int d_unlinked(const struct dentry *dentry)
382 {
383         return d_unhashed(dentry) && !IS_ROOT(dentry);
384 }
385 
386 static inline int cant_mount(const struct dentry *dentry)
387 {
388         return (dentry->d_flags & DCACHE_CANT_MOUNT);
389 }
390 
391 static inline void dont_mount(struct dentry *dentry)
392 {
393         spin_lock(&dentry->d_lock);
394         dentry->d_flags |= DCACHE_CANT_MOUNT;
395         spin_unlock(&dentry->d_lock);
396 }
397 
398 extern void dput(struct dentry *);
399 
400 static inline bool d_managed(const struct dentry *dentry)
401 {
402         return dentry->d_flags & DCACHE_MANAGED_DENTRY;
403 }
404 
405 static inline bool d_mountpoint(const struct dentry *dentry)
406 {
407         return dentry->d_flags & DCACHE_MOUNTED;
408 }
409 
410 /*
411  * Directory cache entry type accessor functions.
412  */
413 static inline void __d_set_type(struct dentry *dentry, unsigned type)
414 {
415         dentry->d_flags = (dentry->d_flags & ~DCACHE_ENTRY_TYPE) | type;
416 }
417 
418 static inline void __d_clear_type(struct dentry *dentry)
419 {
420         __d_set_type(dentry, DCACHE_MISS_TYPE);
421 }
422 
423 static inline void d_set_type(struct dentry *dentry, unsigned type)
424 {
425         spin_lock(&dentry->d_lock);
426         __d_set_type(dentry, type);
427         spin_unlock(&dentry->d_lock);
428 }
429 
430 static inline unsigned __d_entry_type(const struct dentry *dentry)
431 {
432         return dentry->d_flags & DCACHE_ENTRY_TYPE;
433 }
434 
435 static inline bool d_can_lookup(const struct dentry *dentry)
436 {
437         return __d_entry_type(dentry) == DCACHE_DIRECTORY_TYPE;
438 }
439 
440 static inline bool d_is_autodir(const struct dentry *dentry)
441 {
442         return __d_entry_type(dentry) == DCACHE_AUTODIR_TYPE;
443 }
444 
445 static inline bool d_is_dir(const struct dentry *dentry)
446 {
447         return d_can_lookup(dentry) || d_is_autodir(dentry);
448 }
449 
450 static inline bool d_is_symlink(const struct dentry *dentry)
451 {
452         return __d_entry_type(dentry) == DCACHE_SYMLINK_TYPE;
453 }
454 
455 static inline bool d_is_file(const struct dentry *dentry)
456 {
457         return __d_entry_type(dentry) == DCACHE_FILE_TYPE;
458 }
459 
460 static inline bool d_is_negative(const struct dentry *dentry)
461 {
462         return __d_entry_type(dentry) == DCACHE_MISS_TYPE;
463 }
464 
465 static inline bool d_is_positive(const struct dentry *dentry)
466 {
467         return !d_is_negative(dentry);
468 }
469 
470 extern int sysctl_vfs_cache_pressure;
471 
472 static inline unsigned long vfs_pressure_ratio(unsigned long val)
473 {
474         return mult_frac(val, sysctl_vfs_cache_pressure, 100);
475 }
476 #endif  /* __LINUX_DCACHE_H */
477 

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