include/linux/dcache.h

   1 #ifndef __LINUX_DCACHE_H
   2 #define __LINUX_DCACHE_H
   3
   4 #include <asm/atomic.h>
   5 #include <linux/list.h>
   6 #include <linux/rculist.h>
   7 #include <linux/spinlock.h>
   8 #include <linux/cache.h>
   9 #include <linux/rcupdate.h>
  10
  11 struct nameidata;
  12 struct path;
  13 struct vfsmount;
  14
  15 /*
  16  * linux/include/linux/dcache.h
  17  *
  18  * Dirent cache data structures
  19  *
  20  * (C) Copyright 1997 Thomas Schoebel-Theuer,
  21  * with heavy changes by Linus Torvalds
  22  */
  23
  24 #define IS_ROOT(x) ((x) == (x)->d_parent)
  25
  26 /*
  27  * "quick string" -- eases parameter passing, but more importantly
  28  * saves "metadata" about the string (ie length and the hash).
  29  *
  30  * hash comes first so it snuggles against d_parent in the
  31  * dentry.
  32  */
  33 struct qstr {
  34         unsigned int hash;
  35         unsigned int len;
  36         const unsigned char *name;
  37 };
  38
  39 struct dentry_stat_t {
  40         int nr_dentry;
  41         int nr_unused;
  42         int age_limit;          /* age in seconds */
  43         int want_pages;         /* pages requested by system */
  44         int dummy[2];
  45 };
  46 extern struct dentry_stat_t dentry_stat;
  47
  48 /* Name hashing routines. Initial hash value */
  49 /* Hash courtesy of the R5 hash in reiserfs modulo sign bits */
  50 #define init_name_hash()                0
  51
  52 /* partial hash update function. Assume roughly 4 bits per character */
  53 static inline unsigned long
  54 partial_name_hash(unsigned long c, unsigned long prevhash)
  55 {
  56         return (prevhash + (c << 4) + (c >> 4)) * 11;
  57 }
  58
  59 /*
  60  * Finally: cut down the number of bits to a int value (and try to avoid
  61  * losing bits)
  62  */
  63 static inline unsigned long end_name_hash(unsigned long hash)
  64 {
  65         return (unsigned int) hash;
  66 }
  67
  68 /* Compute the hash for a name string. */
  69 static inline unsigned int
  70 full_name_hash(const unsigned char *name, unsigned int len)
  71 {
  72         unsigned long hash = init_name_hash();
  73         while (len--)
  74                 hash = partial_name_hash(*name++, hash);
  75         return end_name_hash(hash);
  76 }
  77
  78 /*
  79  * Try to keep struct dentry aligned on 64 byte cachelines (this will
  80  * give reasonable cacheline footprint with larger lines without the
  81  * large memory footprint increase).
  82  */
  83 #ifdef CONFIG_64BIT
  84 #define DNAME_INLINE_LEN_MIN 32 /* 192 bytes */
  85 #else
  86 #define DNAME_INLINE_LEN_MIN 40 /* 128 bytes */
  87 #endif
  88
  89 struct dentry {
  90         atomic_t d_count;
  91         unsigned int d_flags;           /* protected by d_lock */
  92         spinlock_t d_lock;              /* per dentry lock */
  93         int d_mounted;
  94         struct inode *d_inode;          /* Where the name belongs to - NULL is
  95                                          * negative */
  96         /*
  97          * The next three fields are touched by __d_lookup.  Place them here
  98          * so they all fit in a cache line.
  99          */
 100         struct hlist_node d_hash;       /* lookup hash list */
 101         struct dentry *d_parent;        /* parent directory */
 102         struct qstr d_name;
 103
 104         struct list_head d_lru;         /* LRU list */
 105         /*
 106          * d_child and d_rcu can share memory
 107          */
 108         union {
 109                 struct list_head d_child;       /* child of parent list */
 110                 struct rcu_head d_rcu;
 111         } d_u;
 112         struct list_head d_subdirs;     /* our children */
 113         struct list_head d_alias;       /* inode alias list */
 114         unsigned long d_time;           /* used by d_revalidate */
 115         const struct dentry_operations *d_op;
 116         struct super_block *d_sb;       /* The root of the dentry tree */
 117         void *d_fsdata;                 /* fs-specific data */
 118
 119         unsigned char d_iname[DNAME_INLINE_LEN_MIN];    /* small names */
 120 };
 121
 122 /*
 123  * dentry->d_lock spinlock nesting subclasses:
 124  *
 125  * 0: normal
 126  * 1: nested
 127  */
 128 enum dentry_d_lock_class
 129 {
 130         DENTRY_D_LOCK_NORMAL, /* implicitly used by plain spin_lock() APIs. */
 131         DENTRY_D_LOCK_NESTED
 132 };
 133
 134 struct dentry_operations {
 135         int (*d_revalidate)(struct dentry *, struct nameidata *);
 136         int (*d_hash) (struct dentry *, struct qstr *);
 137         int (*d_compare) (struct dentry *, struct qstr *, struct qstr *);
 138         int (*d_delete)(struct dentry *);
 139         void (*d_release)(struct dentry *);
 140         void (*d_iput)(struct dentry *, struct inode *);
 141         char *(*d_dname)(struct dentry *, char *, int);
 142 };
 143
 144 /* the dentry parameter passed to d_hash and d_compare is the parent
 145  * directory of the entries to be compared. It is used in case these
 146  * functions need any directory specific information for determining
 147  * equivalency classes.  Using the dentry itself might not work, as it
 148  * might be a negative dentry which has no information associated with
 149  * it */
 150
 151 /*
 152 locking rules:
 153                 big lock        dcache_lock     d_lock   may block
 154 d_revalidate:   no              no              no       yes
 155 d_hash          no              no              no       yes
 156 d_compare:      no              yes             yes      no
 157 d_delete:       no              yes             no       no
 158 d_release:      no              no              no       yes
 159 d_iput:         no              no              no       yes
 160  */
 161
 162 /* d_flags entries */
 163 #define DCACHE_AUTOFS_PENDING 0x0001    /* autofs: "under construction" */
 164 #define DCACHE_NFSFS_RENAMED  0x0002    /* this dentry has been "silly
 165                                          * renamed" and has to be
 166                                          * deleted on the last dput()
 167                                          */
 168 #define DCACHE_DISCONNECTED 0x0004
 169      /* This dentry is possibly not currently connected to the dcache tree,
 170       * in which case its parent will either be itself, or will have this
 171       * flag as well.  nfsd will not use a dentry with this bit set, but will
 172       * first endeavour to clear the bit either by discovering that it is
 173       * connected, or by performing lookup operations.   Any filesystem which
 174       * supports nfsd_operations MUST have a lookup function which, if it finds
 175       * a directory inode with a DCACHE_DISCONNECTED dentry, will d_move
 176       * that dentry into place and return that dentry rather than the passed one,
 177       * typically using d_splice_alias.
 178       */
 179
 180 #define DCACHE_REFERENCED       0x0008  /* Recently used, don't discard. */
 181 #define DCACHE_UNHASHED         0x0010
 182
 183 #define DCACHE_INOTIFY_PARENT_WATCHED   0x0020 /* Parent inode is watched */
 184
 185 #define DCACHE_COOKIE           0x0040  /* For use by dcookie subsystem */
 186
 187 extern spinlock_t dcache_lock;
 188 extern seqlock_t rename_lock;
 189
 190 /**
 191  * d_drop - drop a dentry
 192  * @dentry: dentry to drop
 193  *
 194  * d_drop() unhashes the entry from the parent dentry hashes, so that it won't
 195  * be found through a VFS lookup any more. Note that this is different from
 196  * deleting the dentry - d_delete will try to mark the dentry negative if
 197  * possible, giving a successful _negative_ lookup, while d_drop will
 198  * just make the cache lookup fail.
 199  *
 200  * d_drop() is used mainly for stuff that wants to invalidate a dentry for some
 201  * reason (NFS timeouts or autofs deletes).
 202  *
 203  * __d_drop requires dentry->d_lock.
 204  */
 205
 206 static inline void __d_drop(struct dentry *dentry)
 207 {
 208         if (!(dentry->d_flags & DCACHE_UNHASHED)) {
 209                 dentry->d_flags |= DCACHE_UNHASHED;
 210                 hlist_del_rcu(&dentry->d_hash);
 211         }
 212 }
 213
 214 static inline void d_drop(struct dentry *dentry)
 215 {
 216         spin_lock(&dcache_lock);
 217         spin_lock(&dentry->d_lock);
 218         __d_drop(dentry);
 219         spin_unlock(&dentry->d_lock);
 220         spin_unlock(&dcache_lock);
 221 }
 222
 223 static inline int dname_external(struct dentry *dentry)
 224 {
 225         return dentry->d_name.name != dentry->d_iname;
 226 }
 227
 228 /*
 229  * These are the low-level FS interfaces to the dcache..
 230  */
 231 extern void d_instantiate(struct dentry *, struct inode *);
 232 extern struct dentry * d_instantiate_unique(struct dentry *, struct inode *);
 233 extern struct dentry * d_materialise_unique(struct dentry *, struct inode *);
 234 extern void d_delete(struct dentry *);
 235
 236 /* allocate/de-allocate */
 237 extern struct dentry * d_alloc(struct dentry *, const struct qstr *);
 238 extern struct dentry * d_splice_alias(struct inode *, struct dentry *);
 239 extern struct dentry * d_add_ci(struct dentry *, struct inode *, struct qstr *);
 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_alloc_root(struct inode *);
 248
 249 /* <clickety>-<click> the ramfs-type tree */
 250 extern void d_genocide(struct dentry *);
 251
 252 extern struct dentry *d_find_alias(struct inode *);
 253 extern void d_prune_aliases(struct inode *);
 254
 255 /* test whether we have any submounts in a subdir tree */
 256 extern int have_submounts(struct dentry *);
 257
 258 /*
 259  * This adds the entry to the hash queues.
 260  */
 261 extern void d_rehash(struct dentry *);
 262
 263 /**
 264  * d_add - add dentry to hash queues
 265  * @entry: dentry to add
 266  * @inode: The inode to attach to this dentry
 267  *
 268  * This adds the entry to the hash queues and initializes @inode.
 269  * The entry was actually filled in earlier during d_alloc().
 270  */
 271
 272 static inline void d_add(struct dentry *entry, struct inode *inode)
 273 {
 274         d_instantiate(entry, inode);
 275         d_rehash(entry);
 276 }
 277
 278 /**
 279  * d_add_unique - add dentry to hash queues without aliasing
 280  * @entry: dentry to add
 281  * @inode: The inode to attach to this dentry
 282  *
 283  * This adds the entry to the hash queues and initializes @inode.
 284  * The entry was actually filled in earlier during d_alloc().
 285  */
 286 static inline struct dentry *d_add_unique(struct dentry *entry, struct inode *inode)
 287 {
 288         struct dentry *res;
 289
 290         res = d_instantiate_unique(entry, inode);
 291         d_rehash(res != NULL ? res : entry);
 292         return res;
 293 }
 294
 295 /* used for rename() and baskets */
 296 extern void d_move(struct dentry *, struct dentry *);
 297 extern struct dentry *d_ancestor(struct dentry *, struct dentry *);
 298
 299 /* appendix may either be NULL or be used for transname suffixes */
 300 extern struct dentry * d_lookup(struct dentry *, struct qstr *);
 301 extern struct dentry * __d_lookup(struct dentry *, struct qstr *);
 302 extern struct dentry * d_hash_and_lookup(struct dentry *, struct qstr *);
 303
 304 /* validate "insecure" dentry pointer */
 305 extern int d_validate(struct dentry *, struct dentry *);
 306
 307 /*
 308  * helper function for dentry_operations.d_dname() members
 309  */
 310 extern char *dynamic_dname(struct dentry *, char *, int, const char *, ...);
 311
 312 extern char *__d_path(const struct path *path, struct path *root, char *, int);
 313 extern char *d_path(const struct path *, char *, int);
 314 extern char *dentry_path(struct dentry *, char *, int);
 315
 316 /* Allocation counts.. */
 317
 318 /**
 319  *      dget, dget_locked       -       get a reference to a dentry
 320  *      @dentry: dentry to get a reference to
 321  *
 322  *      Given a dentry or %NULL pointer increment the reference count
 323  *      if appropriate and return the dentry. A dentry will not be
 324  *      destroyed when it has references. dget() should never be
 325  *      called for dentries with zero reference counter. For these cases
 326  *      (preferably none, functions in dcache.c are sufficient for normal
 327  *      needs and they take necessary precautions) you should hold dcache_lock
 328  *      and call dget_locked() instead of dget().
 329  */
 330
 331 static inline struct dentry *dget(struct dentry *dentry)
 332 {
 333         if (dentry) {
 334                 BUG_ON(!atomic_read(&dentry->d_count));
 335                 atomic_inc(&dentry->d_count);
 336         }
 337         return dentry;
 338 }
 339
 340 extern struct dentry * dget_locked(struct dentry *);
 341
 342 /**
 343  *      d_unhashed -    is dentry hashed
 344  *      @dentry: entry to check
 345  *
 346  *      Returns true if the dentry passed is not currently hashed.
 347  */
 348
 349 static inline int d_unhashed(struct dentry *dentry)
 350 {
 351         return (dentry->d_flags & DCACHE_UNHASHED);
 352 }
 353
 354 static inline struct dentry *dget_parent(struct dentry *dentry)
 355 {
 356         struct dentry *ret;
 357
 358         spin_lock(&dentry->d_lock);
 359         ret = dget(dentry->d_parent);
 360         spin_unlock(&dentry->d_lock);
 361         return ret;
 362 }
 363
 364 extern void dput(struct dentry *);
 365
 366 static inline int d_mountpoint(struct dentry *dentry)
 367 {
 368         return dentry->d_mounted;
 369 }
 370
 371 extern struct vfsmount *lookup_mnt(struct vfsmount *, struct dentry *);
 372 extern struct dentry *lookup_create(struct nameidata *nd, int is_dir);
 373
 374 extern int sysctl_vfs_cache_pressure;
 375
 376 #endif  /* __LINUX_DCACHE_H */