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/spinlock.h>
   7 #include <linux/cache.h>
   8 #include <linux/rcupdate.h>
   9
  10 struct nameidata;
  11 struct path;
  12 struct vfsmount;
  13
  14 /*
  15  * linux/include/linux/dcache.h
  16  *
  17  * Dirent cache data structures
  18  *
  19  * (C) Copyright 1997 Thomas Schoebel-Theuer,
  20  * with heavy changes by Linus Torvalds
  21  */
  22
  23 #define IS_ROOT(x) ((x) == (x)->d_parent)
  24
  25 /*
  26  * "quick string" -- eases parameter passing, but more importantly
  27  * saves "metadata" about the string (ie length and the hash).
  28  *
  29  * hash comes first so it snuggles against d_parent in the
  30  * dentry.
  31  */
  32 struct qstr {
  33         unsigned int hash;
  34         unsigned int len;
  35         const unsigned char *name;
  36 };
  37
  38 struct dentry_stat_t {
  39         int nr_dentry;
  40         int nr_unused;
  41         int age_limit;          /* age in seconds */
  42         int want_pages;         /* pages requested by system */
  43         int dummy[2];
  44 };
  45 extern struct dentry_stat_t dentry_stat;
  46
  47 /* Name hashing routines. Initial hash value */
  48 /* Hash courtesy of the R5 hash in reiserfs modulo sign bits */
  49 #define init_name_hash()                0
  50
  51 /* partial hash update function. Assume roughly 4 bits per character */
  52 static inline unsigned long
  53 partial_name_hash(unsigned long c, unsigned long prevhash)
  54 {
  55         return (prevhash + (c << 4) + (c >> 4)) * 11;
  56 }
  57
  58 /*
  59  * Finally: cut down the number of bits to a int value (and try to avoid
  60  * losing bits)
  61  */
  62 static inline unsigned long end_name_hash(unsigned long hash)
  63 {
  64         return (unsigned int) hash;
  65 }
  66
  67 /* Compute the hash for a name string. */
  68 static inline unsigned int
  69 full_name_hash(const unsigned char *name, unsigned int len)
  70 {
  71         unsigned long hash = init_name_hash();
  72         while (len--)
  73                 hash = partial_name_hash(*name++, hash);
  74         return end_name_hash(hash);
  75 }
  76
  77 struct dcookie_struct;
  78
  79 #define DNAME_INLINE_LEN_MIN 36
  80
  81 struct dentry {
  82         atomic_t d_count;
  83         unsigned int d_flags;           /* protected by d_lock */
  84         spinlock_t d_lock;              /* per dentry lock */
  85         struct inode *d_inode;          /* Where the name belongs to - NULL is
  86                                          * negative */
  87         /*
  88          * The next three fields are touched by __d_lookup.  Place them here
  89          * so they all fit in a cache line.
  90          */
  91         struct hlist_node d_hash;       /* lookup hash list */
  92         struct dentry *d_parent;        /* parent directory */
  93         struct qstr d_name;
  94
  95         struct list_head d_lru;         /* LRU list */
  96         /*
  97          * d_child and d_rcu can share memory
  98          */
  99         union {
 100                 struct list_head d_child;       /* child of parent list */
 101                 struct rcu_head d_rcu;
 102         } d_u;
 103         struct list_head d_subdirs;     /* our children */
 104         struct list_head d_alias;       /* inode alias list */
 105         unsigned long d_time;           /* used by d_revalidate */
 106         struct dentry_operations *d_op;
 107         struct super_block *d_sb;       /* The root of the dentry tree */
 108         void *d_fsdata;                 /* fs-specific data */
 109 #ifdef CONFIG_PROFILING
 110         struct dcookie_struct *d_cookie; /* cookie, if any */
 111 #endif
 112         int d_mounted;
 113         unsigned char d_iname[DNAME_INLINE_LEN_MIN];    /* small names */
 114 };
 115
 116 /*
 117  * dentry->d_lock spinlock nesting subclasses:
 118  *
 119  * 0: normal
 120  * 1: nested
 121  */
 122 enum dentry_d_lock_class
 123 {
 124         DENTRY_D_LOCK_NORMAL, /* implicitly used by plain spin_lock() APIs. */
 125         DENTRY_D_LOCK_NESTED
 126 };
 127
 128 struct dentry_operations {
 129         int (*d_revalidate)(struct dentry *, struct nameidata *);
 130         int (*d_hash) (struct dentry *, struct qstr *);
 131         int (*d_compare) (struct dentry *, struct qstr *, struct qstr *);
 132         int (*d_delete)(struct dentry *);
 133         void (*d_release)(struct dentry *);
 134         void (*d_iput)(struct dentry *, struct inode *);
 135         char *(*d_dname)(struct dentry *, char *, int);
 136 };
 137
 138 /* the dentry parameter passed to d_hash and d_compare is the parent
 139  * directory of the entries to be compared. It is used in case these
 140  * functions need any directory specific information for determining
 141  * equivalency classes.  Using the dentry itself might not work, as it
 142  * might be a negative dentry which has no information associated with
 143  * it */
 144
 145 /*
 146 locking rules:
 147                 big lock        dcache_lock     d_lock   may block
 148 d_revalidate:   no              no              no       yes
 149 d_hash          no              no              no       yes
 150 d_compare:      no              yes             yes      no
 151 d_delete:       no              yes             no       no
 152 d_release:      no              no              no       yes
 153 d_iput:         no              no              no       yes
 154  */
 155
 156 /* d_flags entries */
 157 #define DCACHE_AUTOFS_PENDING 0x0001    /* autofs: "under construction" */
 158 #define DCACHE_NFSFS_RENAMED  0x0002    /* this dentry has been "silly
 159                                          * renamed" and has to be
 160                                          * deleted on the last dput()
 161                                          */
 162 #define DCACHE_DISCONNECTED 0x0004
 163      /* This dentry is possibly not currently connected to the dcache tree,
 164       * in which case its parent will either be itself, or will have this
 165       * flag as well.  nfsd will not use a dentry with this bit set, but will
 166       * first endeavour to clear the bit either by discovering that it is
 167       * connected, or by performing lookup operations.   Any filesystem which
 168       * supports nfsd_operations MUST have a lookup function which, if it finds
 169       * a directory inode with a DCACHE_DISCONNECTED dentry, will d_move
 170       * that dentry into place and return that dentry rather than the passed one,
 171       * typically using d_splice_alias.
 172       */
 173
 174 #define DCACHE_REFERENCED       0x0008  /* Recently used, don't discard. */
 175 #define DCACHE_UNHASHED         0x0010
 176
 177 #define DCACHE_INOTIFY_PARENT_WATCHED   0x0020 /* Parent inode is watched */
 178
 179 extern spinlock_t dcache_lock;
 180 extern seqlock_t rename_lock;
 181
 182 /**
 183  * d_drop - drop a dentry
 184  * @dentry: dentry to drop
 185  *
 186  * d_drop() unhashes the entry from the parent dentry hashes, so that it won't
 187  * be found through a VFS lookup any more. Note that this is different from
 188  * deleting the dentry - d_delete will try to mark the dentry negative if
 189  * possible, giving a successful _negative_ lookup, while d_drop will
 190  * just make the cache lookup fail.
 191  *
 192  * d_drop() is used mainly for stuff that wants to invalidate a dentry for some
 193  * reason (NFS timeouts or autofs deletes).
 194  *
 195  * __d_drop requires dentry->d_lock.
 196  */
 197
 198 static inline void __d_drop(struct dentry *dentry)
 199 {
 200         if (!(dentry->d_flags & DCACHE_UNHASHED)) {
 201                 dentry->d_flags |= DCACHE_UNHASHED;
 202                 hlist_del_rcu(&dentry->d_hash);
 203         }
 204 }
 205
 206 static inline void d_drop(struct dentry *dentry)
 207 {
 208         spin_lock(&dcache_lock);
 209         spin_lock(&dentry->d_lock);
 210         __d_drop(dentry);
 211         spin_unlock(&dentry->d_lock);
 212         spin_unlock(&dcache_lock);
 213 }
 214
 215 static inline int dname_external(struct dentry *dentry)
 216 {
 217         return dentry->d_name.name != dentry->d_iname;
 218 }
 219
 220 /*
 221  * These are the low-level FS interfaces to the dcache..
 222  */
 223 extern void d_instantiate(struct dentry *, struct inode *);
 224 extern struct dentry * d_instantiate_unique(struct dentry *, struct inode *);
 225 extern struct dentry * d_materialise_unique(struct dentry *, struct inode *);
 226 extern void d_delete(struct dentry *);
 227
 228 /* allocate/de-allocate */
 229 extern struct dentry * d_alloc(struct dentry *, const struct qstr *);
 230 extern struct dentry * d_alloc_anon(struct inode *);
 231 extern struct dentry * d_splice_alias(struct inode *, struct dentry *);
 232 extern void shrink_dcache_sb(struct super_block *);
 233 extern void shrink_dcache_parent(struct dentry *);
 234 extern void shrink_dcache_for_umount(struct super_block *);
 235 extern int d_invalidate(struct dentry *);
 236
 237 /* only used at mount-time */
 238 extern struct dentry * d_alloc_root(struct inode *);
 239
 240 /* <clickety>-<click> the ramfs-type tree */
 241 extern void d_genocide(struct dentry *);
 242
 243 extern struct dentry *d_find_alias(struct inode *);
 244 extern void d_prune_aliases(struct inode *);
 245
 246 /* test whether we have any submounts in a subdir tree */
 247 extern int have_submounts(struct dentry *);
 248
 249 /*
 250  * This adds the entry to the hash queues.
 251  */
 252 extern void d_rehash(struct dentry *);
 253
 254 /**
 255  * d_add - add dentry to hash queues
 256  * @entry: dentry to add
 257  * @inode: The inode to attach to this dentry
 258  *
 259  * This adds the entry to the hash queues and initializes @inode.
 260  * The entry was actually filled in earlier during d_alloc().
 261  */
 262
 263 static inline void d_add(struct dentry *entry, struct inode *inode)
 264 {
 265         d_instantiate(entry, inode);
 266         d_rehash(entry);
 267 }
 268
 269 /**
 270  * d_add_unique - add dentry to hash queues without aliasing
 271  * @entry: dentry to add
 272  * @inode: The inode to attach to this dentry
 273  *
 274  * This adds the entry to the hash queues and initializes @inode.
 275  * The entry was actually filled in earlier during d_alloc().
 276  */
 277 static inline struct dentry *d_add_unique(struct dentry *entry, struct inode *inode)
 278 {
 279         struct dentry *res;
 280
 281         res = d_instantiate_unique(entry, inode);
 282         d_rehash(res != NULL ? res : entry);
 283         return res;
 284 }
 285
 286 /* used for rename() and baskets */
 287 extern void d_move(struct dentry *, struct dentry *);
 288
 289 /* appendix may either be NULL or be used for transname suffixes */
 290 extern struct dentry * d_lookup(struct dentry *, struct qstr *);
 291 extern struct dentry * __d_lookup(struct dentry *, struct qstr *);
 292 extern struct dentry * d_hash_and_lookup(struct dentry *, struct qstr *);
 293
 294 /* validate "insecure" dentry pointer */
 295 extern int d_validate(struct dentry *, struct dentry *);
 296
 297 /*
 298  * helper function for dentry_operations.d_dname() members
 299  */
 300 extern char *dynamic_dname(struct dentry *, char *, int, const char *, ...);
 301
 302 extern char *__d_path(const struct path *path, struct path *root, char *, int);
 303 extern char *d_path(struct path *, char *, int);
 304 extern char *dentry_path(struct dentry *, char *, int);
 305
 306 /* Allocation counts.. */
 307
 308 /**
 309  *      dget, dget_locked       -       get a reference to a dentry
 310  *      @dentry: dentry to get a reference to
 311  *
 312  *      Given a dentry or %NULL pointer increment the reference count
 313  *      if appropriate and return the dentry. A dentry will not be
 314  *      destroyed when it has references. dget() should never be
 315  *      called for dentries with zero reference counter. For these cases
 316  *      (preferably none, functions in dcache.c are sufficient for normal
 317  *      needs and they take necessary precautions) you should hold dcache_lock
 318  *      and call dget_locked() instead of dget().
 319  */
 320
 321 static inline struct dentry *dget(struct dentry *dentry)
 322 {
 323         if (dentry) {
 324                 BUG_ON(!atomic_read(&dentry->d_count));
 325                 atomic_inc(&dentry->d_count);
 326         }
 327         return dentry;
 328 }
 329
 330 extern struct dentry * dget_locked(struct dentry *);
 331
 332 /**
 333  *      d_unhashed -    is dentry hashed
 334  *      @dentry: entry to check
 335  *
 336  *      Returns true if the dentry passed is not currently hashed.
 337  */
 338
 339 static inline int d_unhashed(struct dentry *dentry)
 340 {
 341         return (dentry->d_flags & DCACHE_UNHASHED);
 342 }
 343
 344 static inline struct dentry *dget_parent(struct dentry *dentry)
 345 {
 346         struct dentry *ret;
 347
 348         spin_lock(&dentry->d_lock);
 349         ret = dget(dentry->d_parent);
 350         spin_unlock(&dentry->d_lock);
 351         return ret;
 352 }
 353
 354 extern void dput(struct dentry *);
 355
 356 static inline int d_mountpoint(struct dentry *dentry)
 357 {
 358         return dentry->d_mounted;
 359 }
 360
 361 extern struct vfsmount *lookup_mnt(struct vfsmount *, struct dentry *);
 362 extern struct dentry *lookup_create(struct nameidata *nd, int is_dir);
 363
 364 extern int sysctl_vfs_cache_pressure;
 365
 366 #endif  /* __LINUX_DCACHE_H */