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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 #define hashlen_create(hash,len) (((u64)(len)<<32)|(u32)(hash))
 59 
 60 struct dentry_stat_t {
 61         long nr_dentry;
 62         long nr_unused;
 63         long age_limit;          /* age in seconds */
 64         long want_pages;         /* pages requested by system */
 65         long dummy[2];
 66 };
 67 extern struct dentry_stat_t dentry_stat;
 68 
 69 /* Name hashing routines. Initial hash value */
 70 /* Hash courtesy of the R5 hash in reiserfs modulo sign bits */
 71 #define init_name_hash()                0
 72 
 73 /* partial hash update function. Assume roughly 4 bits per character */
 74 static inline unsigned long
 75 partial_name_hash(unsigned long c, unsigned long prevhash)
 76 {
 77         return (prevhash + (c << 4) + (c >> 4)) * 11;
 78 }
 79 
 80 /*
 81  * Finally: cut down the number of bits to a int value (and try to avoid
 82  * losing bits)
 83  */
 84 static inline unsigned long end_name_hash(unsigned long hash)
 85 {
 86         return (unsigned int) hash;
 87 }
 88 
 89 /* Compute the hash for a name string. */
 90 extern unsigned int full_name_hash(const unsigned char *, unsigned int);
 91 
 92 /*
 93  * Try to keep struct dentry aligned on 64 byte cachelines (this will
 94  * give reasonable cacheline footprint with larger lines without the
 95  * large memory footprint increase).
 96  */
 97 #ifdef CONFIG_64BIT
 98 # define DNAME_INLINE_LEN 32 /* 192 bytes */
 99 #else
100 # ifdef CONFIG_SMP
101 #  define DNAME_INLINE_LEN 36 /* 128 bytes */
102 # else
103 #  define DNAME_INLINE_LEN 40 /* 128 bytes */
104 # endif
105 #endif
106 
107 #define d_lock  d_lockref.lock
108 
109 struct dentry {
110         /* RCU lookup touched fields */
111         unsigned int d_flags;           /* protected by d_lock */
112         seqcount_t d_seq;               /* per dentry seqlock */
113         struct hlist_bl_node d_hash;    /* lookup hash list */
114         struct dentry *d_parent;        /* parent directory */
115         struct qstr d_name;
116         struct inode *d_inode;          /* Where the name belongs to - NULL is
117                                          * negative */
118         unsigned char d_iname[DNAME_INLINE_LEN];        /* small names */
119 
120         /* Ref lookup also touches following */
121         struct lockref d_lockref;       /* per-dentry lock and refcount */
122         const struct dentry_operations *d_op;
123         struct super_block *d_sb;       /* The root of the dentry tree */
124         unsigned long d_time;           /* used by d_revalidate */
125         void *d_fsdata;                 /* fs-specific data */
126 
127         struct list_head d_lru;         /* LRU list */
128         /*
129          * d_child and d_rcu can share memory
130          */
131         union {
132                 struct list_head d_child;       /* child of parent list */
133                 struct rcu_head d_rcu;
134         } d_u;
135         struct list_head d_subdirs;     /* our children */
136         struct hlist_node d_alias;      /* inode alias list */
137 };
138 
139 /*
140  * dentry->d_lock spinlock nesting subclasses:
141  *
142  * 0: normal
143  * 1: nested
144  */
145 enum dentry_d_lock_class
146 {
147         DENTRY_D_LOCK_NORMAL, /* implicitly used by plain spin_lock() APIs. */
148         DENTRY_D_LOCK_NESTED
149 };
150 
151 struct dentry_operations {
152         int (*d_revalidate)(struct dentry *, unsigned int);
153         int (*d_weak_revalidate)(struct dentry *, unsigned int);
154         int (*d_hash)(const struct dentry *, struct qstr *);
155         int (*d_compare)(const struct dentry *, const struct dentry *,
156                         unsigned int, const char *, const struct qstr *);
157         int (*d_delete)(const struct dentry *);
158         void (*d_release)(struct dentry *);
159         void (*d_prune)(struct dentry *);
160         void (*d_iput)(struct dentry *, struct inode *);
161         char *(*d_dname)(struct dentry *, char *, int);
162         struct vfsmount *(*d_automount)(struct path *);
163         int (*d_manage)(struct dentry *, bool);
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 */
220 #define DCACHE_DIRECTORY_TYPE           0x00100000 /* Normal directory */
221 #define DCACHE_AUTODIR_TYPE             0x00200000 /* Lookupless directory (presumed automount) */
222 #define DCACHE_SYMLINK_TYPE             0x00300000 /* Symlink */
223 #define DCACHE_FILE_TYPE                0x00400000 /* Other file type */
224 
225 #define DCACHE_MAY_FREE                 0x00800000
226 
227 extern seqlock_t rename_lock;
228 
229 static inline int dname_external(const struct dentry *dentry)
230 {
231         return dentry->d_name.name != dentry->d_iname;
232 }
233 
234 /*
235  * These are the low-level FS interfaces to the dcache..
236  */
237 extern void d_instantiate(struct dentry *, struct inode *);
238 extern struct dentry * d_instantiate_unique(struct dentry *, struct inode *);
239 extern struct dentry * d_materialise_unique(struct dentry *, struct inode *);
240 extern int d_instantiate_no_diralias(struct dentry *, struct inode *);
241 extern void __d_drop(struct dentry *dentry);
242 extern void d_drop(struct dentry *dentry);
243 extern void d_delete(struct dentry *);
244 extern void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op);
245 
246 /* allocate/de-allocate */
247 extern struct dentry * d_alloc(struct dentry *, const struct qstr *);
248 extern struct dentry * d_alloc_pseudo(struct super_block *, const struct qstr *);
249 extern struct dentry * d_splice_alias(struct inode *, struct dentry *);
250 extern struct dentry * d_add_ci(struct dentry *, struct inode *, struct qstr *);
251 extern struct dentry *d_find_any_alias(struct inode *inode);
252 extern struct dentry * d_obtain_alias(struct inode *);
253 extern struct dentry * d_obtain_root(struct inode *);
254 extern void shrink_dcache_sb(struct super_block *);
255 extern void shrink_dcache_parent(struct dentry *);
256 extern void shrink_dcache_for_umount(struct super_block *);
257 extern int d_invalidate(struct dentry *);
258 
259 /* only used at mount-time */
260 extern struct dentry * d_make_root(struct inode *);
261 
262 /* <clickety>-<click> the ramfs-type tree */
263 extern void d_genocide(struct dentry *);
264 
265 extern void d_tmpfile(struct dentry *, struct inode *);
266 
267 extern struct dentry *d_find_alias(struct inode *);
268 extern void d_prune_aliases(struct inode *);
269 
270 /* test whether we have any submounts in a subdir tree */
271 extern int have_submounts(struct dentry *);
272 extern int check_submounts_and_drop(struct dentry *);
273 
274 /*
275  * This adds the entry to the hash queues.
276  */
277 extern void d_rehash(struct dentry *);
278 
279 /**
280  * d_add - add dentry to hash queues
281  * @entry: dentry to add
282  * @inode: The inode to attach to this dentry
283  *
284  * This adds the entry to the hash queues and initializes @inode.
285  * The entry was actually filled in earlier during d_alloc().
286  */
287  
288 static inline void d_add(struct dentry *entry, struct inode *inode)
289 {
290         d_instantiate(entry, inode);
291         d_rehash(entry);
292 }
293 
294 /**
295  * d_add_unique - add dentry to hash queues without aliasing
296  * @entry: dentry to add
297  * @inode: The inode to attach to this dentry
298  *
299  * This adds the entry to the hash queues and initializes @inode.
300  * The entry was actually filled in earlier during d_alloc().
301  */
302 static inline struct dentry *d_add_unique(struct dentry *entry, struct inode *inode)
303 {
304         struct dentry *res;
305 
306         res = d_instantiate_unique(entry, inode);
307         d_rehash(res != NULL ? res : entry);
308         return res;
309 }
310 
311 extern void dentry_update_name_case(struct dentry *, struct qstr *);
312 
313 /* used for rename() and baskets */
314 extern void d_move(struct dentry *, struct dentry *);
315 extern void d_exchange(struct dentry *, struct dentry *);
316 extern struct dentry *d_ancestor(struct dentry *, struct dentry *);
317 
318 /* appendix may either be NULL or be used for transname suffixes */
319 extern struct dentry *d_lookup(const struct dentry *, const struct qstr *);
320 extern struct dentry *d_hash_and_lookup(struct dentry *, struct qstr *);
321 extern struct dentry *__d_lookup(const struct dentry *, const struct qstr *);
322 extern struct dentry *__d_lookup_rcu(const struct dentry *parent,
323                                 const struct qstr *name, unsigned *seq);
324 
325 static inline unsigned d_count(const struct dentry *dentry)
326 {
327         return dentry->d_lockref.count;
328 }
329 
330 /* validate "insecure" dentry pointer */
331 extern int d_validate(struct dentry *, struct dentry *);
332 
333 /*
334  * helper function for dentry_operations.d_dname() members
335  */
336 extern char *dynamic_dname(struct dentry *, char *, int, const char *, ...);
337 extern char *simple_dname(struct dentry *, char *, int);
338 
339 extern char *__d_path(const struct path *, const struct path *, char *, int);
340 extern char *d_absolute_path(const struct path *, char *, int);
341 extern char *d_path(const struct path *, char *, int);
342 extern char *dentry_path_raw(struct dentry *, char *, int);
343 extern char *dentry_path(struct dentry *, char *, int);
344 
345 /* Allocation counts.. */
346 
347 /**
348  *      dget, dget_dlock -      get a reference to a dentry
349  *      @dentry: dentry to get a reference to
350  *
351  *      Given a dentry or %NULL pointer increment the reference count
352  *      if appropriate and return the dentry. A dentry will not be 
353  *      destroyed when it has references.
354  */
355 static inline struct dentry *dget_dlock(struct dentry *dentry)
356 {
357         if (dentry)
358                 dentry->d_lockref.count++;
359         return dentry;
360 }
361 
362 static inline struct dentry *dget(struct dentry *dentry)
363 {
364         if (dentry)
365                 lockref_get(&dentry->d_lockref);
366         return dentry;
367 }
368 
369 extern struct dentry *dget_parent(struct dentry *dentry);
370 
371 /**
372  *      d_unhashed -    is dentry hashed
373  *      @dentry: entry to check
374  *
375  *      Returns true if the dentry passed is not currently hashed.
376  */
377  
378 static inline int d_unhashed(const struct dentry *dentry)
379 {
380         return hlist_bl_unhashed(&dentry->d_hash);
381 }
382 
383 static inline int d_unlinked(const struct dentry *dentry)
384 {
385         return d_unhashed(dentry) && !IS_ROOT(dentry);
386 }
387 
388 static inline int cant_mount(const struct dentry *dentry)
389 {
390         return (dentry->d_flags & DCACHE_CANT_MOUNT);
391 }
392 
393 static inline void dont_mount(struct dentry *dentry)
394 {
395         spin_lock(&dentry->d_lock);
396         dentry->d_flags |= DCACHE_CANT_MOUNT;
397         spin_unlock(&dentry->d_lock);
398 }
399 
400 extern void dput(struct dentry *);
401 
402 static inline bool d_managed(const struct dentry *dentry)
403 {
404         return dentry->d_flags & DCACHE_MANAGED_DENTRY;
405 }
406 
407 static inline bool d_mountpoint(const struct dentry *dentry)
408 {
409         return dentry->d_flags & DCACHE_MOUNTED;
410 }
411 
412 /*
413  * Directory cache entry type accessor functions.
414  */
415 static inline void __d_set_type(struct dentry *dentry, unsigned type)
416 {
417         dentry->d_flags = (dentry->d_flags & ~DCACHE_ENTRY_TYPE) | type;
418 }
419 
420 static inline void __d_clear_type(struct dentry *dentry)
421 {
422         __d_set_type(dentry, DCACHE_MISS_TYPE);
423 }
424 
425 static inline void d_set_type(struct dentry *dentry, unsigned type)
426 {
427         spin_lock(&dentry->d_lock);
428         __d_set_type(dentry, type);
429         spin_unlock(&dentry->d_lock);
430 }
431 
432 static inline unsigned __d_entry_type(const struct dentry *dentry)
433 {
434         return dentry->d_flags & DCACHE_ENTRY_TYPE;
435 }
436 
437 static inline bool d_can_lookup(const struct dentry *dentry)
438 {
439         return __d_entry_type(dentry) == DCACHE_DIRECTORY_TYPE;
440 }
441 
442 static inline bool d_is_autodir(const struct dentry *dentry)
443 {
444         return __d_entry_type(dentry) == DCACHE_AUTODIR_TYPE;
445 }
446 
447 static inline bool d_is_dir(const struct dentry *dentry)
448 {
449         return d_can_lookup(dentry) || d_is_autodir(dentry);
450 }
451 
452 static inline bool d_is_symlink(const struct dentry *dentry)
453 {
454         return __d_entry_type(dentry) == DCACHE_SYMLINK_TYPE;
455 }
456 
457 static inline bool d_is_file(const struct dentry *dentry)
458 {
459         return __d_entry_type(dentry) == DCACHE_FILE_TYPE;
460 }
461 
462 static inline bool d_is_negative(const struct dentry *dentry)
463 {
464         return __d_entry_type(dentry) == DCACHE_MISS_TYPE;
465 }
466 
467 static inline bool d_is_positive(const struct dentry *dentry)
468 {
469         return !d_is_negative(dentry);
470 }
471 
472 extern int sysctl_vfs_cache_pressure;
473 
474 static inline unsigned long vfs_pressure_ratio(unsigned long val)
475 {
476         return mult_frac(val, sysctl_vfs_cache_pressure, 100);
477 }
478 #endif  /* __LINUX_DCACHE_H */
479 

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