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Linux/include/linux/dcache.h

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  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 #else
 33  #define HASH_LEN_DECLARE u32 len; u32 hash;
 34 #endif
 35 
 36 /*
 37  * "quick string" -- eases parameter passing, but more importantly
 38  * saves "metadata" about the string (ie length and the hash).
 39  *
 40  * hash comes first so it snuggles against d_parent in the
 41  * dentry.
 42  */
 43 struct qstr {
 44         union {
 45                 struct {
 46                         HASH_LEN_DECLARE;
 47                 };
 48                 u64 hash_len;
 49         };
 50         const unsigned char *name;
 51 };
 52 
 53 #define QSTR_INIT(n,l) { { { .len = l } }, .name = n }
 54 #define hashlen_hash(hashlen) ((u32) (hashlen))
 55 #define hashlen_len(hashlen)  ((u32)((hashlen) >> 32))
 56 
 57 struct dentry_stat_t {
 58         long nr_dentry;
 59         long nr_unused;
 60         long age_limit;          /* age in seconds */
 61         long want_pages;         /* pages requested by system */
 62         long dummy[2];
 63 };
 64 extern struct dentry_stat_t dentry_stat;
 65 
 66 /* Name hashing routines. Initial hash value */
 67 /* Hash courtesy of the R5 hash in reiserfs modulo sign bits */
 68 #define init_name_hash()                0
 69 
 70 /* partial hash update function. Assume roughly 4 bits per character */
 71 static inline unsigned long
 72 partial_name_hash(unsigned long c, unsigned long prevhash)
 73 {
 74         return (prevhash + (c << 4) + (c >> 4)) * 11;
 75 }
 76 
 77 /*
 78  * Finally: cut down the number of bits to a int value (and try to avoid
 79  * losing bits)
 80  */
 81 static inline unsigned long end_name_hash(unsigned long hash)
 82 {
 83         return (unsigned int) hash;
 84 }
 85 
 86 /* Compute the hash for a name string. */
 87 extern unsigned int full_name_hash(const unsigned char *, unsigned int);
 88 
 89 /*
 90  * Try to keep struct dentry aligned on 64 byte cachelines (this will
 91  * give reasonable cacheline footprint with larger lines without the
 92  * large memory footprint increase).
 93  */
 94 #ifdef CONFIG_64BIT
 95 # define DNAME_INLINE_LEN 32 /* 192 bytes */
 96 #else
 97 # ifdef CONFIG_SMP
 98 #  define DNAME_INLINE_LEN 36 /* 128 bytes */
 99 # else
100 #  define DNAME_INLINE_LEN 40 /* 128 bytes */
101 # endif
102 #endif
103 
104 #define d_lock  d_lockref.lock
105 
106 struct dentry {
107         /* RCU lookup touched fields */
108         unsigned int d_flags;           /* protected by d_lock */
109         seqcount_t d_seq;               /* per dentry seqlock */
110         struct hlist_bl_node d_hash;    /* lookup hash list */
111         struct dentry *d_parent;        /* parent directory */
112         struct qstr d_name;
113         struct inode *d_inode;          /* Where the name belongs to - NULL is
114                                          * negative */
115         unsigned char d_iname[DNAME_INLINE_LEN];        /* small names */
116 
117         /* Ref lookup also touches following */
118         struct lockref d_lockref;       /* per-dentry lock and refcount */
119         const struct dentry_operations *d_op;
120         struct super_block *d_sb;       /* The root of the dentry tree */
121         unsigned long d_time;           /* used by d_revalidate */
122         void *d_fsdata;                 /* fs-specific data */
123 
124         struct list_head d_lru;         /* LRU list */
125         struct list_head d_child;       /* child of parent list */
126         struct list_head d_subdirs;     /* our children */
127         /*
128          * d_alias and d_rcu can share memory
129          */
130         union {
131                 struct hlist_node d_alias;      /* inode alias list */
132                 struct rcu_head d_rcu;
133         } d_u;
134 };
135 
136 /*
137  * dentry->d_lock spinlock nesting subclasses:
138  *
139  * 0: normal
140  * 1: nested
141  */
142 enum dentry_d_lock_class
143 {
144         DENTRY_D_LOCK_NORMAL, /* implicitly used by plain spin_lock() APIs. */
145         DENTRY_D_LOCK_NESTED
146 };
147 
148 struct dentry_operations {
149         int (*d_revalidate)(struct dentry *, unsigned int);
150         int (*d_weak_revalidate)(struct dentry *, unsigned int);
151         int (*d_hash)(const struct dentry *, struct qstr *);
152         int (*d_compare)(const struct dentry *, const struct dentry *,
153                         unsigned int, const char *, const struct qstr *);
154         int (*d_delete)(const struct dentry *);
155         void (*d_release)(struct dentry *);
156         void (*d_prune)(struct dentry *);
157         void (*d_iput)(struct dentry *, struct inode *);
158         char *(*d_dname)(struct dentry *, char *, int);
159         struct vfsmount *(*d_automount)(struct path *);
160         int (*d_manage)(struct dentry *, bool);
161 } ____cacheline_aligned;
162 
163 /*
164  * Locking rules for dentry_operations callbacks are to be found in
165  * Documentation/filesystems/Locking. Keep it updated!
166  *
167  * FUrther descriptions are found in Documentation/filesystems/vfs.txt.
168  * Keep it updated too!
169  */
170 
171 /* d_flags entries */
172 #define DCACHE_OP_HASH          0x0001
173 #define DCACHE_OP_COMPARE       0x0002
174 #define DCACHE_OP_REVALIDATE    0x0004
175 #define DCACHE_OP_DELETE        0x0008
176 #define DCACHE_OP_PRUNE         0x0010
177 
178 #define DCACHE_DISCONNECTED     0x0020
179      /* This dentry is possibly not currently connected to the dcache tree, in
180       * which case its parent will either be itself, or will have this flag as
181       * well.  nfsd will not use a dentry with this bit set, but will first
182       * endeavour to clear the bit either by discovering that it is connected,
183       * or by performing lookup operations.   Any filesystem which supports
184       * nfsd_operations MUST have a lookup function which, if it finds a
185       * directory inode with a DCACHE_DISCONNECTED dentry, will d_move that
186       * dentry into place and return that dentry rather than the passed one,
187       * typically using d_splice_alias. */
188 
189 #define DCACHE_REFERENCED       0x0040  /* Recently used, don't discard. */
190 #define DCACHE_RCUACCESS        0x0080  /* Entry has ever been RCU-visible */
191 
192 #define DCACHE_CANT_MOUNT       0x0100
193 #define DCACHE_GENOCIDE         0x0200
194 #define DCACHE_SHRINK_LIST      0x0400
195 
196 #define DCACHE_OP_WEAK_REVALIDATE       0x0800
197 
198 #define DCACHE_NFSFS_RENAMED    0x1000
199      /* this dentry has been "silly renamed" and has to be deleted on the last
200       * dput() */
201 #define DCACHE_COOKIE           0x2000  /* For use by dcookie subsystem */
202 #define DCACHE_FSNOTIFY_PARENT_WATCHED 0x4000
203      /* Parent inode is watched by some fsnotify listener */
204 
205 #define DCACHE_MOUNTED          0x10000 /* is a mountpoint */
206 #define DCACHE_NEED_AUTOMOUNT   0x20000 /* handle automount on this dir */
207 #define DCACHE_MANAGE_TRANSIT   0x40000 /* manage transit from this dirent */
208 #define DCACHE_MANAGED_DENTRY \
209         (DCACHE_MOUNTED|DCACHE_NEED_AUTOMOUNT|DCACHE_MANAGE_TRANSIT)
210 
211 #define DCACHE_LRU_LIST         0x80000
212 #define DCACHE_DENTRY_KILLED    0x100000
213 
214 #define DCACHE_MAY_FREE                 0x00800000
215 
216 extern seqlock_t rename_lock;
217 
218 static inline int dname_external(const struct dentry *dentry)
219 {
220         return dentry->d_name.name != dentry->d_iname;
221 }
222 
223 /*
224  * These are the low-level FS interfaces to the dcache..
225  */
226 extern void d_instantiate(struct dentry *, struct inode *);
227 extern struct dentry * d_instantiate_unique(struct dentry *, struct inode *);
228 extern struct dentry * d_materialise_unique(struct dentry *, struct inode *);
229 extern void __d_drop(struct dentry *dentry);
230 extern void d_drop(struct dentry *dentry);
231 extern void d_delete(struct dentry *);
232 extern void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op);
233 
234 /* allocate/de-allocate */
235 extern struct dentry * d_alloc(struct dentry *, const struct qstr *);
236 extern struct dentry * d_alloc_pseudo(struct super_block *, const struct qstr *);
237 extern struct dentry * d_splice_alias(struct inode *, struct dentry *);
238 extern struct dentry * d_add_ci(struct dentry *, struct inode *, struct qstr *);
239 extern struct dentry *d_find_any_alias(struct inode *inode);
240 extern struct dentry * d_obtain_alias(struct inode *);
241 extern void shrink_dcache_sb(struct super_block *);
242 extern void shrink_dcache_parent(struct dentry *);
243 extern void shrink_dcache_for_umount(struct super_block *);
244 extern int d_invalidate(struct dentry *);
245 
246 /* only used at mount-time */
247 extern struct dentry * d_make_root(struct inode *);
248 
249 /* <clickety>-<click> the ramfs-type tree */
250 extern void d_genocide(struct dentry *);
251 
252 extern void d_tmpfile(struct dentry *, struct inode *);
253 
254 extern struct dentry *d_find_alias(struct inode *);
255 extern void d_prune_aliases(struct inode *);
256 
257 /* test whether we have any submounts in a subdir tree */
258 extern int have_submounts(struct dentry *);
259 extern int check_submounts_and_drop(struct dentry *);
260 
261 /*
262  * This adds the entry to the hash queues.
263  */
264 extern void d_rehash(struct dentry *);
265 
266 /**
267  * d_add - add dentry to hash queues
268  * @entry: dentry to add
269  * @inode: The inode to attach to this dentry
270  *
271  * This adds the entry to the hash queues and initializes @inode.
272  * The entry was actually filled in earlier during d_alloc().
273  */
274  
275 static inline void d_add(struct dentry *entry, struct inode *inode)
276 {
277         d_instantiate(entry, inode);
278         d_rehash(entry);
279 }
280 
281 /**
282  * d_add_unique - add dentry to hash queues without aliasing
283  * @entry: dentry to add
284  * @inode: The inode to attach to this dentry
285  *
286  * This adds the entry to the hash queues and initializes @inode.
287  * The entry was actually filled in earlier during d_alloc().
288  */
289 static inline struct dentry *d_add_unique(struct dentry *entry, struct inode *inode)
290 {
291         struct dentry *res;
292 
293         res = d_instantiate_unique(entry, inode);
294         d_rehash(res != NULL ? res : entry);
295         return res;
296 }
297 
298 extern void dentry_update_name_case(struct dentry *, struct qstr *);
299 
300 /* used for rename() and baskets */
301 extern void d_move(struct dentry *, struct dentry *);
302 extern struct dentry *d_ancestor(struct dentry *, struct dentry *);
303 
304 /* appendix may either be NULL or be used for transname suffixes */
305 extern struct dentry *d_lookup(const struct dentry *, const struct qstr *);
306 extern struct dentry *d_hash_and_lookup(struct dentry *, struct qstr *);
307 extern struct dentry *__d_lookup(const struct dentry *, const struct qstr *);
308 extern struct dentry *__d_lookup_rcu(const struct dentry *parent,
309                                 const struct qstr *name, unsigned *seq);
310 
311 static inline unsigned d_count(const struct dentry *dentry)
312 {
313         return dentry->d_lockref.count;
314 }
315 
316 /* validate "insecure" dentry pointer */
317 extern int d_validate(struct dentry *, struct dentry *);
318 
319 /*
320  * helper function for dentry_operations.d_dname() members
321  */
322 extern char *dynamic_dname(struct dentry *, char *, int, const char *, ...);
323 extern char *simple_dname(struct dentry *, char *, int);
324 
325 extern char *__d_path(const struct path *, const struct path *, char *, int);
326 extern char *d_absolute_path(const struct path *, char *, int);
327 extern char *d_path(const struct path *, char *, int);
328 extern char *dentry_path_raw(struct dentry *, char *, int);
329 extern char *dentry_path(struct dentry *, char *, int);
330 
331 /* Allocation counts.. */
332 
333 /**
334  *      dget, dget_dlock -      get a reference to a dentry
335  *      @dentry: dentry to get a reference to
336  *
337  *      Given a dentry or %NULL pointer increment the reference count
338  *      if appropriate and return the dentry. A dentry will not be 
339  *      destroyed when it has references.
340  */
341 static inline struct dentry *dget_dlock(struct dentry *dentry)
342 {
343         if (dentry)
344                 dentry->d_lockref.count++;
345         return dentry;
346 }
347 
348 static inline struct dentry *dget(struct dentry *dentry)
349 {
350         if (dentry)
351                 lockref_get(&dentry->d_lockref);
352         return dentry;
353 }
354 
355 extern struct dentry *dget_parent(struct dentry *dentry);
356 
357 /**
358  *      d_unhashed -    is dentry hashed
359  *      @dentry: entry to check
360  *
361  *      Returns true if the dentry passed is not currently hashed.
362  */
363  
364 static inline int d_unhashed(const struct dentry *dentry)
365 {
366         return hlist_bl_unhashed(&dentry->d_hash);
367 }
368 
369 static inline int d_unlinked(const struct dentry *dentry)
370 {
371         return d_unhashed(dentry) && !IS_ROOT(dentry);
372 }
373 
374 static inline int cant_mount(const struct dentry *dentry)
375 {
376         return (dentry->d_flags & DCACHE_CANT_MOUNT);
377 }
378 
379 static inline void dont_mount(struct dentry *dentry)
380 {
381         spin_lock(&dentry->d_lock);
382         dentry->d_flags |= DCACHE_CANT_MOUNT;
383         spin_unlock(&dentry->d_lock);
384 }
385 
386 extern void dput(struct dentry *);
387 
388 static inline bool d_managed(const struct dentry *dentry)
389 {
390         return dentry->d_flags & DCACHE_MANAGED_DENTRY;
391 }
392 
393 static inline bool d_mountpoint(const struct dentry *dentry)
394 {
395         return dentry->d_flags & DCACHE_MOUNTED;
396 }
397 
398 extern int sysctl_vfs_cache_pressure;
399 
400 static inline unsigned long vfs_pressure_ratio(unsigned long val)
401 {
402         return mult_frac(val, sysctl_vfs_cache_pressure, 100);
403 }
404 #endif  /* __LINUX_DCACHE_H */
405 

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