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 and d_bucket 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 16-byte range, with 16-byte alignment.
  92          */
  93         struct dentry *d_parent;        /* parent directory */
  94         struct hlist_head *d_bucket;    /* lookup hash bucket */
  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         struct hlist_node d_hash;       /* lookup hash list */
 108         int d_mounted;
 109         unsigned char d_iname[DNAME_INLINE_LEN_MIN];    /* small names */
 110 };
 111
 112 struct dentry_operations {
 113         int (*d_revalidate)(struct dentry *, struct nameidata *);
 114         int (*d_hash) (struct dentry *, struct qstr *);
 115         int (*d_compare) (struct dentry *, struct qstr *, struct qstr *);
 116         int (*d_delete)(struct dentry *);
 117         void (*d_release)(struct dentry *);
 118         void (*d_iput)(struct dentry *, struct inode *);
 119 };
 120
 121 /* the dentry parameter passed to d_hash and d_compare is the parent
 122  * directory of the entries to be compared. It is used in case these
 123  * functions need any directory specific information for determining
 124  * equivalency classes.  Using the dentry itself might not work, as it
 125  * might be a negative dentry which has no information associated with
 126  * it */
 127
 128 /*
 129 locking rules:
 130                 big lock        dcache_lock     d_lock   may block
 131 d_revalidate:   no              no              no       yes
 132 d_hash          no              no              no       yes
 133 d_compare:      no              yes             yes      no
 134 d_delete:       no              yes             no       no
 135 d_release:      no              no              no       yes
 136 d_iput:         no              no              no       yes
 137  */
 138
 139 /* d_flags entries */
 140 #define DCACHE_AUTOFS_PENDING 0x0001    /* autofs: "under construction" */
 141 #define DCACHE_NFSFS_RENAMED  0x0002    /* this dentry has been "silly
 142                                          * renamed" and has to be
 143                                          * deleted on the last dput()
 144                                          */
 145 #define DCACHE_DISCONNECTED 0x0004
 146      /* This dentry is possibly not currently connected to the dcache tree,
 147       * in which case its parent will either be itself, or will have this
 148       * flag as well.  nfsd will not use a dentry with this bit set, but will
 149       * first endeavour to clear the bit either by discovering that it is
 150       * connected, or by performing lookup operations.   Any filesystem which
 151       * supports nfsd_operations MUST have a lookup function which, if it finds
 152       * a directory inode with a DCACHE_DISCONNECTED dentry, will d_move
 153       * that dentry into place and return that dentry rather than the passed one,
 154       * typically using d_splice_alias.
 155       */
 156
 157 #define DCACHE_REFERENCED       0x0008  /* Recently used, don't discard. */
 158 #define DCACHE_UNHASHED         0x0010
 159
 160 extern spinlock_t dcache_lock;
 161
 162 /**
 163  * d_drop - drop a dentry
 164  * @dentry: dentry to drop
 165  *
 166  * d_drop() unhashes the entry from the parent
 167  * dentry hashes, so that it won't be found through
 168  * a VFS lookup any more. Note that this is different
 169  * from deleting the dentry - d_delete will try to
 170  * mark the dentry negative if possible, giving a
 171  * successful _negative_ lookup, while d_drop will
 172  * just make the cache lookup fail.
 173  *
 174  * d_drop() is used mainly for stuff that wants
 175  * to invalidate a dentry for some reason (NFS
 176  * timeouts or autofs deletes).
 177  */
 178
 179 static inline void __d_drop(struct dentry *dentry)
 180 {
 181         if (!(dentry->d_flags & DCACHE_UNHASHED)) {
 182                 dentry->d_flags |= DCACHE_UNHASHED;
 183                 hlist_del_rcu(&dentry->d_hash);
 184         }
 185 }
 186
 187 static inline void d_drop(struct dentry *dentry)
 188 {
 189         spin_lock(&dcache_lock);
 190         __d_drop(dentry);
 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 void d_delete(struct dentry *);
 204
 205 /* allocate/de-allocate */
 206 extern struct dentry * d_alloc(struct dentry *, const struct qstr *);
 207 extern struct dentry * d_alloc_anon(struct inode *);
 208 extern struct dentry * d_splice_alias(struct inode *, struct dentry *);
 209 extern void shrink_dcache_sb(struct super_block *);
 210 extern void shrink_dcache_parent(struct dentry *);
 211 extern void shrink_dcache_anon(struct hlist_head *);
 212 extern int d_invalidate(struct dentry *);
 213
 214 /* only used at mount-time */
 215 extern struct dentry * d_alloc_root(struct inode *);
 216
 217 /* <clickety>-<click> the ramfs-type tree */
 218 extern void d_genocide(struct dentry *);
 219
 220 extern struct dentry *d_find_alias(struct inode *);
 221 extern void d_prune_aliases(struct inode *);
 222
 223 /* test whether we have any submounts in a subdir tree */
 224 extern int have_submounts(struct dentry *);
 225
 226 /*
 227  * This adds the entry to the hash queues.
 228  */
 229 extern void d_rehash(struct dentry *);
 230
 231 /**
 232  * d_add - add dentry to hash queues
 233  * @entry: dentry to add
 234  * @inode: The inode to attach to this dentry
 235  *
 236  * This adds the entry to the hash queues and initializes @inode.
 237  * The entry was actually filled in earlier during d_alloc().
 238  */
 239
 240 static inline void d_add(struct dentry *entry, struct inode *inode)
 241 {
 242         d_instantiate(entry, inode);
 243         d_rehash(entry);
 244 }
 245
 246 /* used for rename() and baskets */
 247 extern void d_move(struct dentry *, struct dentry *);
 248
 249 /* appendix may either be NULL or be used for transname suffixes */
 250 extern struct dentry * d_lookup(struct dentry *, struct qstr *);
 251 extern struct dentry * __d_lookup(struct dentry *, struct qstr *);
 252
 253 /* validate "insecure" dentry pointer */
 254 extern int d_validate(struct dentry *, struct dentry *);
 255
 256 extern char * d_path(struct dentry *, struct vfsmount *, char *, int);
 257
 258 /* Allocation counts.. */
 259
 260 /**
 261  *      dget, dget_locked       -       get a reference to a dentry
 262  *      @dentry: dentry to get a reference to
 263  *
 264  *      Given a dentry or %NULL pointer increment the reference count
 265  *      if appropriate and return the dentry. A dentry will not be
 266  *      destroyed when it has references. dget() should never be
 267  *      called for dentries with zero reference counter. For these cases
 268  *      (preferably none, functions in dcache.c are sufficient for normal
 269  *      needs and they take necessary precautions) you should hold dcache_lock
 270  *      and call dget_locked() instead of dget().
 271  */
 272
 273 static inline struct dentry *dget(struct dentry *dentry)
 274 {
 275         if (dentry) {
 276                 BUG_ON(!atomic_read(&dentry->d_count));
 277                 atomic_inc(&dentry->d_count);
 278         }
 279         return dentry;
 280 }
 281
 282 extern struct dentry * dget_locked(struct dentry *);
 283
 284 /**
 285  *      d_unhashed -    is dentry hashed
 286  *      @dentry: entry to check
 287  *
 288  *      Returns true if the dentry passed is not currently hashed.
 289  */
 290
 291 static inline int d_unhashed(struct dentry *dentry)
 292 {
 293         return (dentry->d_flags & DCACHE_UNHASHED);
 294 }
 295
 296 static inline struct dentry *dget_parent(struct dentry *dentry)
 297 {
 298         struct dentry *ret;
 299
 300         spin_lock(&dentry->d_lock);
 301         ret = dget(dentry->d_parent);
 302         spin_unlock(&dentry->d_lock);
 303         return ret;
 304 }
 305
 306 extern void dput(struct dentry *);
 307
 308 static inline int d_mountpoint(struct dentry *dentry)
 309 {
 310         return dentry->d_mounted;
 311 }
 312
 313 extern struct vfsmount *lookup_mnt(struct vfsmount *, struct dentry *);
 314 extern struct dentry *lookup_create(struct nameidata *nd, int is_dir);
 315
 316 extern int sysctl_vfs_cache_pressure;
 317
 318 #endif /* __KERNEL__ */
 319
 320 #endif  /* __LINUX_DCACHE_H */