include/linux/dcache.h

   1 #ifndef __LINUX_DCACHE_H
   2 #define __LINUX_DCACHE_H
   3
   4 #ifdef __KERNEL__
   5
   6 #include <asm/atomic.h>
   7 #include <linux/list.h>
   8 #include <linux/spinlock.h>
   9 #include <linux/cache.h>
  10 #include <linux/rcupdate.h>
  11 #include <asm/bug.h>
  12
  13 struct nameidata;
  14 struct vfsmount;
  15
  16 /*
  17  * linux/include/linux/dcache.h
  18  *
  19  * Dirent cache data structures
  20  *
  21  * (C) Copyright 1997 Thomas Schoebel-Theuer,
  22  * with heavy changes by Linus Torvalds
  23  */
  24
  25 #define IS_ROOT(x) ((x) == (x)->d_parent)
  26
  27 /*
  28  * "quick string" -- eases parameter passing, but more importantly
  29  * saves "metadata" about the string (ie length and the hash).
  30  *
  31  * hash comes first so it snuggles against d_parent in the
  32  * dentry.
  33  */
  34 struct qstr {
  35         unsigned int hash;
  36         unsigned int len;
  37         const unsigned char *name;
  38 };
  39
  40 struct dentry_stat_t {
  41         int nr_dentry;
  42         int nr_unused;
  43         int age_limit;          /* age in seconds */
  44         int want_pages;         /* pages requested by system */
  45         int dummy[2];
  46 };
  47 extern struct dentry_stat_t dentry_stat;
  48
  49 /* Name hashing routines. Initial hash value */
  50 /* Hash courtesy of the R5 hash in reiserfs modulo sign bits */
  51 #define init_name_hash()                0
  52
  53 /* partial hash update function. Assume roughly 4 bits per character */
  54 static inline unsigned long
  55 partial_name_hash(unsigned long c, unsigned long prevhash)
  56 {
  57         return (prevhash + (c << 4) + (c >> 4)) * 11;
  58 }
  59
  60 /*
  61  * Finally: cut down the number of bits to a int value (and try to avoid
  62  * losing bits)
  63  */
  64 static inline unsigned long end_name_hash(unsigned long hash)
  65 {
  66         return (unsigned int) hash;
  67 }
  68
  69 /* Compute the hash for a name string. */
  70 static inline unsigned int
  71 full_name_hash(const unsigned char *name, unsigned int len)
  72 {
  73         unsigned long hash = init_name_hash();
  74         while (len--)
  75                 hash = partial_name_hash(*name++, hash);
  76         return end_name_hash(hash);
  77 }
  78
  79 struct dcookie_struct;
  80
  81 #define DNAME_INLINE_LEN_MIN 36
  82
  83 struct dentry {
  84         atomic_t d_count;
  85         unsigned int d_flags;           /* protected by d_lock */
  86         spinlock_t d_lock;              /* per dentry lock */
  87         struct inode *d_inode;          /* Where the name belongs to - NULL is
  88                                          * negative */
  89         /*
  90          * The next three fields are touched by __d_lookup.  Place them here
  91          * so they all fit in a cache line.
  92          */
  93         struct hlist_node d_hash;       /* lookup hash list */
  94         struct dentry *d_parent;        /* parent directory */
  95         struct qstr d_name;
  96
  97         struct list_head d_lru;         /* LRU list */
  98         struct list_head d_child;       /* child of parent list */
  99         struct list_head d_subdirs;     /* our children */
 100         struct list_head d_alias;       /* inode alias list */
 101         unsigned long d_time;           /* used by d_revalidate */
 102         struct dentry_operations *d_op;
 103         struct super_block *d_sb;       /* The root of the dentry tree */
 104         void *d_fsdata;                 /* fs-specific data */
 105         struct rcu_head d_rcu;
 106         struct dcookie_struct *d_cookie; /* cookie, if any */
 107         int d_mounted;
 108         unsigned char d_iname[DNAME_INLINE_LEN_MIN];    /* small names */
 109 };
 110
 111 struct dentry_operations {
 112         int (*d_revalidate)(struct dentry *, struct nameidata *);
 113         int (*d_hash) (struct dentry *, struct qstr *);
 114         int (*d_compare) (struct dentry *, struct qstr *, struct qstr *);
 115         int (*d_delete)(struct dentry *);
 116         void (*d_release)(struct dentry *);
 117         void (*d_iput)(struct dentry *, struct inode *);
 118 };
 119
 120 /* the dentry parameter passed to d_hash and d_compare is the parent
 121  * directory of the entries to be compared. It is used in case these
 122  * functions need any directory specific information for determining
 123  * equivalency classes.  Using the dentry itself might not work, as it
 124  * might be a negative dentry which has no information associated with
 125  * it */
 126
 127 /*
 128 locking rules:
 129                 big lock        dcache_lock     d_lock   may block
 130 d_revalidate:   no              no              no       yes
 131 d_hash          no              no              no       yes
 132 d_compare:      no              yes             yes      no
 133 d_delete:       no              yes             no       no
 134 d_release:      no              no              no       yes
 135 d_iput:         no              no              no       yes
 136  */
 137
 138 /* d_flags entries */
 139 #define DCACHE_AUTOFS_PENDING 0x0001    /* autofs: "under construction" */
 140 #define DCACHE_NFSFS_RENAMED  0x0002    /* this dentry has been "silly
 141                                          * renamed" and has to be
 142                                          * deleted on the last dput()
 143                                          */
 144 #define DCACHE_DISCONNECTED 0x0004
 145      /* This dentry is possibly not currently connected to the dcache tree,
 146       * in which case its parent will either be itself, or will have this
 147       * flag as well.  nfsd will not use a dentry with this bit set, but will
 148       * first endeavour to clear the bit either by discovering that it is
 149       * connected, or by performing lookup operations.   Any filesystem which
 150       * supports nfsd_operations MUST have a lookup function which, if it finds
 151       * a directory inode with a DCACHE_DISCONNECTED dentry, will d_move
 152       * that dentry into place and return that dentry rather than the passed one,
 153       * typically using d_splice_alias.
 154       */
 155
 156 #define DCACHE_REFERENCED       0x0008  /* Recently used, don't discard. */
 157 #define DCACHE_UNHASHED         0x0010
 158
 159 extern spinlock_t dcache_lock;
 160
 161 /**
 162  * d_drop - drop a dentry
 163  * @dentry: dentry to drop
 164  *
 165  * d_drop() unhashes the entry from the parent dentry hashes, so that it won't
 166  * be found through a VFS lookup any more. Note that this is different from
 167  * deleting the dentry - d_delete will try to mark the dentry negative if
 168  * possible, giving a successful _negative_ lookup, while d_drop will
 169  * just make the cache lookup fail.
 170  *
 171  * d_drop() is used mainly for stuff that wants to invalidate a dentry for some
 172  * reason (NFS timeouts or autofs deletes).
 173  *
 174  * __d_drop requires dentry->d_lock.
 175  */
 176
 177 static inline void __d_drop(struct dentry *dentry)
 178 {
 179         if (!(dentry->d_flags & DCACHE_UNHASHED)) {
 180                 dentry->d_flags |= DCACHE_UNHASHED;
 181                 hlist_del_rcu(&dentry->d_hash);
 182         }
 183 }
 184
 185 static inline void d_drop(struct dentry *dentry)
 186 {
 187         spin_lock(&dcache_lock);
 188         spin_lock(&dentry->d_lock);
 189         __d_drop(dentry);
 190         spin_unlock(&dentry->d_lock);
 191         spin_unlock(&dcache_lock);
 192 }
 193
 194 static inline int dname_external(struct dentry *dentry)
 195 {
 196         return dentry->d_name.name != dentry->d_iname;
 197 }
 198
 199 /*
 200  * These are the low-level FS interfaces to the dcache..
 201  */
 202 extern void d_instantiate(struct dentry *, struct inode *);
 203 extern struct dentry * d_instantiate_unique(struct dentry *, struct inode *);
 204 extern void d_delete(struct dentry *);
 205
 206 /* allocate/de-allocate */
 207 extern struct dentry * d_alloc(struct dentry *, const struct qstr *);
 208 extern struct dentry * d_alloc_anon(struct inode *);
 209 extern struct dentry * d_splice_alias(struct inode *, struct dentry *);
 210 extern void shrink_dcache_sb(struct super_block *);
 211 extern void shrink_dcache_parent(struct dentry *);
 212 extern void shrink_dcache_anon(struct hlist_head *);
 213 extern int d_invalidate(struct dentry *);
 214
 215 /* only used at mount-time */
 216 extern struct dentry * d_alloc_root(struct inode *);
 217
 218 /* <clickety>-<click> the ramfs-type tree */
 219 extern void d_genocide(struct dentry *);
 220
 221 extern struct dentry *d_find_alias(struct inode *);
 222 extern void d_prune_aliases(struct inode *);
 223
 224 /* test whether we have any submounts in a subdir tree */
 225 extern int have_submounts(struct dentry *);
 226
 227 /*
 228  * This adds the entry to the hash queues.
 229  */
 230 extern void d_rehash(struct dentry *);
 231
 232 /**
 233  * d_add - add dentry to hash queues
 234  * @entry: dentry to add
 235  * @inode: The inode to attach to this dentry
 236  *
 237  * This adds the entry to the hash queues and initializes @inode.
 238  * The entry was actually filled in earlier during d_alloc().
 239  */
 240
 241 static inline void d_add(struct dentry *entry, struct inode *inode)
 242 {
 243         d_instantiate(entry, inode);
 244         d_rehash(entry);
 245 }
 246
 247 /**
 248  * d_add_unique - add dentry to hash queues without aliasing
 249  * @entry: dentry to add
 250  * @inode: The inode to attach to this dentry
 251  *
 252  * This adds the entry to the hash queues and initializes @inode.
 253  * The entry was actually filled in earlier during d_alloc().
 254  */
 255 static inline struct dentry *d_add_unique(struct dentry *entry, struct inode *inode)
 256 {
 257         struct dentry *res;
 258
 259         res = d_instantiate_unique(entry, inode);
 260         d_rehash(res != NULL ? res : entry);
 261         return res;
 262 }
 263
 264 /* used for rename() and baskets */
 265 extern void d_move(struct dentry *, struct dentry *);
 266
 267 /* appendix may either be NULL or be used for transname suffixes */
 268 extern struct dentry * d_lookup(struct dentry *, struct qstr *);
 269 extern struct dentry * __d_lookup(struct dentry *, struct qstr *);
 270
 271 /* validate "insecure" dentry pointer */
 272 extern int d_validate(struct dentry *, struct dentry *);
 273
 274 extern char * d_path(struct dentry *, struct vfsmount *, char *, int);
 275
 276 /* Allocation counts.. */
 277
 278 /**
 279  *      dget, dget_locked       -       get a reference to a dentry
 280  *      @dentry: dentry to get a reference to
 281  *
 282  *      Given a dentry or %NULL pointer increment the reference count
 283  *      if appropriate and return the dentry. A dentry will not be
 284  *      destroyed when it has references. dget() should never be
 285  *      called for dentries with zero reference counter. For these cases
 286  *      (preferably none, functions in dcache.c are sufficient for normal
 287  *      needs and they take necessary precautions) you should hold dcache_lock
 288  *      and call dget_locked() instead of dget().
 289  */
 290
 291 static inline struct dentry *dget(struct dentry *dentry)
 292 {
 293         if (dentry) {
 294                 BUG_ON(!atomic_read(&dentry->d_count));
 295                 atomic_inc(&dentry->d_count);
 296         }
 297         return dentry;
 298 }
 299
 300 extern struct dentry * dget_locked(struct dentry *);
 301
 302 /**
 303  *      d_unhashed -    is dentry hashed
 304  *      @dentry: entry to check
 305  *
 306  *      Returns true if the dentry passed is not currently hashed.
 307  */
 308
 309 static inline int d_unhashed(struct dentry *dentry)
 310 {
 311         return (dentry->d_flags & DCACHE_UNHASHED);
 312 }
 313
 314 static inline struct dentry *dget_parent(struct dentry *dentry)
 315 {
 316         struct dentry *ret;
 317
 318         spin_lock(&dentry->d_lock);
 319         ret = dget(dentry->d_parent);
 320         spin_unlock(&dentry->d_lock);
 321         return ret;
 322 }
 323
 324 extern void dput(struct dentry *);
 325
 326 static inline int d_mountpoint(struct dentry *dentry)
 327 {
 328         return dentry->d_mounted;
 329 }
 330
 331 extern struct vfsmount *lookup_mnt(struct vfsmount *, struct dentry *);
 332 extern struct vfsmount *__lookup_mnt(struct vfsmount *, struct dentry *, int);
 333 extern struct dentry *lookup_create(struct nameidata *nd, int is_dir);
 334
 335 extern int sysctl_vfs_cache_pressure;
 336
 337 #endif /* __KERNEL__ */
 338
 339 #endif  /* __LINUX_DCACHE_H */