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         /*
  99          * d_child and d_rcu can share memory
 100          */
 101         union {
 102                 struct list_head d_child;       /* child of parent list */
 103                 struct rcu_head d_rcu;
 104         } d_u;
 105         struct list_head d_subdirs;     /* our children */
 106         struct list_head d_alias;       /* inode alias list */
 107         unsigned long d_time;           /* used by d_revalidate */
 108         struct dentry_operations *d_op;
 109         struct super_block *d_sb;       /* The root of the dentry tree */
 110         void *d_fsdata;                 /* fs-specific data */
 111         struct dcookie_struct *d_cookie; /* cookie, if any */
 112         int d_mounted;
 113         unsigned char d_iname[DNAME_INLINE_LEN_MIN];    /* small names */
 114 };
 115
 116 struct dentry_operations {
 117         int (*d_revalidate)(struct dentry *, struct nameidata *);
 118         int (*d_hash) (struct dentry *, struct qstr *);
 119         int (*d_compare) (struct dentry *, struct qstr *, struct qstr *);
 120         int (*d_delete)(struct dentry *);
 121         void (*d_release)(struct dentry *);
 122         void (*d_iput)(struct dentry *, struct inode *);
 123 };
 124
 125 /* the dentry parameter passed to d_hash and d_compare is the parent
 126  * directory of the entries to be compared. It is used in case these
 127  * functions need any directory specific information for determining
 128  * equivalency classes.  Using the dentry itself might not work, as it
 129  * might be a negative dentry which has no information associated with
 130  * it */
 131
 132 /*
 133 locking rules:
 134                 big lock        dcache_lock     d_lock   may block
 135 d_revalidate:   no              no              no       yes
 136 d_hash          no              no              no       yes
 137 d_compare:      no              yes             yes      no
 138 d_delete:       no              yes             no       no
 139 d_release:      no              no              no       yes
 140 d_iput:         no              no              no       yes
 141  */
 142
 143 /* d_flags entries */
 144 #define DCACHE_AUTOFS_PENDING 0x0001    /* autofs: "under construction" */
 145 #define DCACHE_NFSFS_RENAMED  0x0002    /* this dentry has been "silly
 146                                          * renamed" and has to be
 147                                          * deleted on the last dput()
 148                                          */
 149 #define DCACHE_DISCONNECTED 0x0004
 150      /* This dentry is possibly not currently connected to the dcache tree,
 151       * in which case its parent will either be itself, or will have this
 152       * flag as well.  nfsd will not use a dentry with this bit set, but will
 153       * first endeavour to clear the bit either by discovering that it is
 154       * connected, or by performing lookup operations.   Any filesystem which
 155       * supports nfsd_operations MUST have a lookup function which, if it finds
 156       * a directory inode with a DCACHE_DISCONNECTED dentry, will d_move
 157       * that dentry into place and return that dentry rather than the passed one,
 158       * typically using d_splice_alias.
 159       */
 160
 161 #define DCACHE_REFERENCED       0x0008  /* Recently used, don't discard. */
 162 #define DCACHE_UNHASHED         0x0010
 163
 164 extern spinlock_t dcache_lock;
 165
 166 /**
 167  * d_drop - drop a dentry
 168  * @dentry: dentry to drop
 169  *
 170  * d_drop() unhashes the entry from the parent dentry hashes, so that it won't
 171  * be found through a VFS lookup any more. Note that this is different from
 172  * deleting the dentry - d_delete will try to mark the dentry negative if
 173  * possible, giving a successful _negative_ lookup, while d_drop will
 174  * just make the cache lookup fail.
 175  *
 176  * d_drop() is used mainly for stuff that wants to invalidate a dentry for some
 177  * reason (NFS timeouts or autofs deletes).
 178  *
 179  * __d_drop requires dentry->d_lock.
 180  */
 181
 182 static inline void __d_drop(struct dentry *dentry)
 183 {
 184         if (!(dentry->d_flags & DCACHE_UNHASHED)) {
 185                 dentry->d_flags |= DCACHE_UNHASHED;
 186                 hlist_del_rcu(&dentry->d_hash);
 187         }
 188 }
 189
 190 static inline void d_drop(struct dentry *dentry)
 191 {
 192         spin_lock(&dcache_lock);
 193         spin_lock(&dentry->d_lock);
 194         __d_drop(dentry);
 195         spin_unlock(&dentry->d_lock);
 196         spin_unlock(&dcache_lock);
 197 }
 198
 199 static inline int dname_external(struct dentry *dentry)
 200 {
 201         return dentry->d_name.name != dentry->d_iname;
 202 }
 203
 204 /*
 205  * These are the low-level FS interfaces to the dcache..
 206  */
 207 extern void d_instantiate(struct dentry *, struct inode *);
 208 extern struct dentry * d_instantiate_unique(struct dentry *, struct inode *);
 209 extern void d_delete(struct dentry *);
 210
 211 /* allocate/de-allocate */
 212 extern struct dentry * d_alloc(struct dentry *, const struct qstr *);
 213 extern struct dentry * d_alloc_anon(struct inode *);
 214 extern struct dentry * d_splice_alias(struct inode *, struct dentry *);
 215 extern void shrink_dcache_sb(struct super_block *);
 216 extern void shrink_dcache_parent(struct dentry *);
 217 extern void shrink_dcache_anon(struct hlist_head *);
 218 extern int d_invalidate(struct dentry *);
 219
 220 /* only used at mount-time */
 221 extern struct dentry * d_alloc_root(struct inode *);
 222
 223 /* <clickety>-<click> the ramfs-type tree */
 224 extern void d_genocide(struct dentry *);
 225
 226 extern struct dentry *d_find_alias(struct inode *);
 227 extern void d_prune_aliases(struct inode *);
 228
 229 /* test whether we have any submounts in a subdir tree */
 230 extern int have_submounts(struct dentry *);
 231
 232 /*
 233  * This adds the entry to the hash queues.
 234  */
 235 extern void d_rehash(struct dentry *);
 236
 237 /**
 238  * d_add - add dentry to hash queues
 239  * @entry: dentry to add
 240  * @inode: The inode to attach to this dentry
 241  *
 242  * This adds the entry to the hash queues and initializes @inode.
 243  * The entry was actually filled in earlier during d_alloc().
 244  */
 245
 246 static inline void d_add(struct dentry *entry, struct inode *inode)
 247 {
 248         d_instantiate(entry, inode);
 249         d_rehash(entry);
 250 }
 251
 252 /**
 253  * d_add_unique - add dentry to hash queues without aliasing
 254  * @entry: dentry to add
 255  * @inode: The inode to attach to this dentry
 256  *
 257  * This adds the entry to the hash queues and initializes @inode.
 258  * The entry was actually filled in earlier during d_alloc().
 259  */
 260 static inline struct dentry *d_add_unique(struct dentry *entry, struct inode *inode)
 261 {
 262         struct dentry *res;
 263
 264         res = d_instantiate_unique(entry, inode);
 265         d_rehash(res != NULL ? res : entry);
 266         return res;
 267 }
 268
 269 /* used for rename() and baskets */
 270 extern void d_move(struct dentry *, struct dentry *);
 271
 272 /* appendix may either be NULL or be used for transname suffixes */
 273 extern struct dentry * d_lookup(struct dentry *, struct qstr *);
 274 extern struct dentry * __d_lookup(struct dentry *, struct qstr *);
 275
 276 /* validate "insecure" dentry pointer */
 277 extern int d_validate(struct dentry *, struct dentry *);
 278
 279 extern char * d_path(struct dentry *, struct vfsmount *, char *, int);
 280
 281 /* Allocation counts.. */
 282
 283 /**
 284  *      dget, dget_locked       -       get a reference to a dentry
 285  *      @dentry: dentry to get a reference to
 286  *
 287  *      Given a dentry or %NULL pointer increment the reference count
 288  *      if appropriate and return the dentry. A dentry will not be
 289  *      destroyed when it has references. dget() should never be
 290  *      called for dentries with zero reference counter. For these cases
 291  *      (preferably none, functions in dcache.c are sufficient for normal
 292  *      needs and they take necessary precautions) you should hold dcache_lock
 293  *      and call dget_locked() instead of dget().
 294  */
 295
 296 static inline struct dentry *dget(struct dentry *dentry)
 297 {
 298         if (dentry) {
 299                 BUG_ON(!atomic_read(&dentry->d_count));
 300                 atomic_inc(&dentry->d_count);
 301         }
 302         return dentry;
 303 }
 304
 305 extern struct dentry * dget_locked(struct dentry *);
 306
 307 /**
 308  *      d_unhashed -    is dentry hashed
 309  *      @dentry: entry to check
 310  *
 311  *      Returns true if the dentry passed is not currently hashed.
 312  */
 313
 314 static inline int d_unhashed(struct dentry *dentry)
 315 {
 316         return (dentry->d_flags & DCACHE_UNHASHED);
 317 }
 318
 319 static inline struct dentry *dget_parent(struct dentry *dentry)
 320 {
 321         struct dentry *ret;
 322
 323         spin_lock(&dentry->d_lock);
 324         ret = dget(dentry->d_parent);
 325         spin_unlock(&dentry->d_lock);
 326         return ret;
 327 }
 328
 329 extern void dput(struct dentry *);
 330
 331 static inline int d_mountpoint(struct dentry *dentry)
 332 {
 333         return dentry->d_mounted;
 334 }
 335
 336 extern struct vfsmount *lookup_mnt(struct vfsmount *, struct dentry *);
 337 extern struct vfsmount *__lookup_mnt(struct vfsmount *, struct dentry *, int);
 338 extern struct dentry *lookup_create(struct nameidata *nd, int is_dir);
 339
 340 extern int sysctl_vfs_cache_pressure;
 341
 342 #endif /* __KERNEL__ */
 343
 344 #endif  /* __LINUX_DCACHE_H */