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         unsigned int d_count;           /* protected by d_lock */
  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)(const struct dentry *, const struct inode *,
 137                         struct qstr *);
 138         int (*d_compare)(const struct dentry *, const struct inode *,
 139                         const struct dentry *, const struct inode *,
 140                         unsigned int, const char *, const struct qstr *);
 141         int (*d_delete)(const struct dentry *);
 142         void (*d_release)(struct dentry *);
 143         void (*d_iput)(struct dentry *, struct inode *);
 144         char *(*d_dname)(struct dentry *, char *, int);
 145 };
 146
 147 /*
 148  * Locking rules for dentry_operations callbacks are to be found in
 149  * Documentation/filesystems/Locking. Keep it updated!
 150  *
 151  * FUrther descriptions are found in Documentation/filesystems/vfs.txt.
 152  * Keep it updated too!
 153  */
 154
 155 /* d_flags entries */
 156 #define DCACHE_AUTOFS_PENDING 0x0001    /* autofs: "under construction" */
 157 #define DCACHE_NFSFS_RENAMED  0x0002    /* this dentry has been "silly
 158                                          * renamed" and has to be
 159                                          * deleted on the last dput()
 160                                          */
 161 #define DCACHE_DISCONNECTED 0x0004
 162      /* This dentry is possibly not currently connected to the dcache tree,
 163       * in which case its parent will either be itself, or will have this
 164       * flag as well.  nfsd will not use a dentry with this bit set, but will
 165       * first endeavour to clear the bit either by discovering that it is
 166       * connected, or by performing lookup operations.   Any filesystem which
 167       * supports nfsd_operations MUST have a lookup function which, if it finds
 168       * a directory inode with a DCACHE_DISCONNECTED dentry, will d_move
 169       * that dentry into place and return that dentry rather than the passed one,
 170       * typically using d_splice_alias.
 171       */
 172
 173 #define DCACHE_REFERENCED       0x0008  /* Recently used, don't discard. */
 174 #define DCACHE_UNHASHED         0x0010
 175
 176 #define DCACHE_INOTIFY_PARENT_WATCHED   0x0020 /* Parent inode is watched by inotify */
 177
 178 #define DCACHE_COOKIE           0x0040  /* For use by dcookie subsystem */
 179
 180 #define DCACHE_FSNOTIFY_PARENT_WATCHED  0x0080 /* Parent inode is watched by some fsnotify listener */
 181
 182 #define DCACHE_CANT_MOUNT       0x0100
 183 #define DCACHE_GENOCIDE         0x0200
 184
 185 extern spinlock_t dcache_inode_lock;
 186 extern spinlock_t dcache_lock;
 187 extern seqlock_t rename_lock;
 188
 189 static inline int dname_external(struct dentry *dentry)
 190 {
 191         return dentry->d_name.name != dentry->d_iname;
 192 }
 193
 194 /*
 195  * These are the low-level FS interfaces to the dcache..
 196  */
 197 extern void d_instantiate(struct dentry *, struct inode *);
 198 extern struct dentry * d_instantiate_unique(struct dentry *, struct inode *);
 199 extern struct dentry * d_materialise_unique(struct dentry *, struct inode *);
 200 extern void __d_drop(struct dentry *dentry);
 201 extern void d_drop(struct dentry *dentry);
 202 extern void d_delete(struct dentry *);
 203
 204 /* allocate/de-allocate */
 205 extern struct dentry * d_alloc(struct dentry *, const struct qstr *);
 206 extern struct dentry * d_splice_alias(struct inode *, struct dentry *);
 207 extern struct dentry * d_add_ci(struct dentry *, struct inode *, struct qstr *);
 208 extern struct dentry * d_obtain_alias(struct inode *);
 209 extern void shrink_dcache_sb(struct super_block *);
 210 extern void shrink_dcache_parent(struct dentry *);
 211 extern void shrink_dcache_for_umount(struct super_block *);
 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 /**
 247  * d_add_unique - add dentry to hash queues without aliasing
 248  * @entry: dentry to add
 249  * @inode: The inode to attach to this dentry
 250  *
 251  * This adds the entry to the hash queues and initializes @inode.
 252  * The entry was actually filled in earlier during d_alloc().
 253  */
 254 static inline struct dentry *d_add_unique(struct dentry *entry, struct inode *inode)
 255 {
 256         struct dentry *res;
 257
 258         res = d_instantiate_unique(entry, inode);
 259         d_rehash(res != NULL ? res : entry);
 260         return res;
 261 }
 262
 263 extern void dentry_update_name_case(struct dentry *, struct qstr *);
 264
 265 /* used for rename() and baskets */
 266 extern void d_move(struct dentry *, struct dentry *);
 267 extern struct dentry *d_ancestor(struct dentry *, struct dentry *);
 268
 269 /* appendix may either be NULL or be used for transname suffixes */
 270 extern struct dentry * d_lookup(struct dentry *, struct qstr *);
 271 extern struct dentry * __d_lookup(struct dentry *, struct qstr *);
 272 extern struct dentry * d_hash_and_lookup(struct dentry *, struct qstr *);
 273
 274 /* validate "insecure" dentry pointer */
 275 extern int d_validate(struct dentry *, struct dentry *);
 276
 277 /*
 278  * helper function for dentry_operations.d_dname() members
 279  */
 280 extern char *dynamic_dname(struct dentry *, char *, int, const char *, ...);
 281
 282 extern char *__d_path(const struct path *path, struct path *root, char *, int);
 283 extern char *d_path(const struct path *, char *, int);
 284 extern char *d_path_with_unreachable(const struct path *, char *, int);
 285 extern char *dentry_path_raw(struct dentry *, char *, int);
 286 extern char *dentry_path(struct dentry *, char *, int);
 287
 288 /* Allocation counts.. */
 289
 290 /**
 291  *      dget, dget_locked       -       get a reference to a dentry
 292  *      @dentry: dentry to get a reference to
 293  *
 294  *      Given a dentry or %NULL pointer increment the reference count
 295  *      if appropriate and return the dentry. A dentry will not be
 296  *      destroyed when it has references. dget() should never be
 297  *      called for dentries with zero reference counter. For these cases
 298  *      (preferably none, functions in dcache.c are sufficient for normal
 299  *      needs and they take necessary precautions) you should hold dcache_lock
 300  *      and call dget_locked() instead of dget().
 301  */
 302 static inline struct dentry *dget_dlock(struct dentry *dentry)
 303 {
 304         if (dentry) {
 305                 BUG_ON(!dentry->d_count);
 306                 dentry->d_count++;
 307         }
 308         return dentry;
 309 }
 310
 311 static inline struct dentry *dget(struct dentry *dentry)
 312 {
 313         if (dentry) {
 314                 spin_lock(&dentry->d_lock);
 315                 dget_dlock(dentry);
 316                 spin_unlock(&dentry->d_lock);
 317         }
 318         return dentry;
 319 }
 320
 321 extern struct dentry * dget_locked(struct dentry *);
 322 extern struct dentry * dget_locked_dlock(struct dentry *);
 323
 324 extern struct dentry *dget_parent(struct dentry *dentry);
 325
 326 /**
 327  *      d_unhashed -    is dentry hashed
 328  *      @dentry: entry to check
 329  *
 330  *      Returns true if the dentry passed is not currently hashed.
 331  */
 332
 333 static inline int d_unhashed(struct dentry *dentry)
 334 {
 335         return (dentry->d_flags & DCACHE_UNHASHED);
 336 }
 337
 338 static inline int d_unlinked(struct dentry *dentry)
 339 {
 340         return d_unhashed(dentry) && !IS_ROOT(dentry);
 341 }
 342
 343 static inline int cant_mount(struct dentry *dentry)
 344 {
 345         return (dentry->d_flags & DCACHE_CANT_MOUNT);
 346 }
 347
 348 static inline void dont_mount(struct dentry *dentry)
 349 {
 350         spin_lock(&dentry->d_lock);
 351         dentry->d_flags |= DCACHE_CANT_MOUNT;
 352         spin_unlock(&dentry->d_lock);
 353 }
 354
 355 extern void dput(struct dentry *);
 356
 357 static inline int d_mountpoint(struct dentry *dentry)
 358 {
 359         return dentry->d_mounted;
 360 }
 361
 362 extern struct vfsmount *lookup_mnt(struct path *);
 363 extern struct dentry *lookup_create(struct nameidata *nd, int is_dir);
 364
 365 extern int sysctl_vfs_cache_pressure;
 366
 367 #endif  /* __LINUX_DCACHE_H */