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         atomic_t d_count;
  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
 184 extern spinlock_t dcache_lock;
 185 extern seqlock_t rename_lock;
 186
 187 static inline int dname_external(struct dentry *dentry)
 188 {
 189         return dentry->d_name.name != dentry->d_iname;
 190 }
 191
 192 /*
 193  * These are the low-level FS interfaces to the dcache..
 194  */
 195 extern void d_instantiate(struct dentry *, struct inode *);
 196 extern struct dentry * d_instantiate_unique(struct dentry *, struct inode *);
 197 extern struct dentry * d_materialise_unique(struct dentry *, struct inode *);
 198 extern void __d_drop(struct dentry *dentry);
 199 extern void d_drop(struct dentry *dentry);
 200 extern void d_delete(struct dentry *);
 201
 202 /* allocate/de-allocate */
 203 extern struct dentry * d_alloc(struct dentry *, const struct qstr *);
 204 extern struct dentry * d_splice_alias(struct inode *, struct dentry *);
 205 extern struct dentry * d_add_ci(struct dentry *, struct inode *, struct qstr *);
 206 extern struct dentry * d_obtain_alias(struct inode *);
 207 extern void shrink_dcache_sb(struct super_block *);
 208 extern void shrink_dcache_parent(struct dentry *);
 209 extern void shrink_dcache_for_umount(struct super_block *);
 210 extern int d_invalidate(struct dentry *);
 211
 212 /* only used at mount-time */
 213 extern struct dentry * d_alloc_root(struct inode *);
 214
 215 /* <clickety>-<click> the ramfs-type tree */
 216 extern void d_genocide(struct dentry *);
 217
 218 extern struct dentry *d_find_alias(struct inode *);
 219 extern void d_prune_aliases(struct inode *);
 220
 221 /* test whether we have any submounts in a subdir tree */
 222 extern int have_submounts(struct dentry *);
 223
 224 /*
 225  * This adds the entry to the hash queues.
 226  */
 227 extern void d_rehash(struct dentry *);
 228
 229 /**
 230  * d_add - add dentry to hash queues
 231  * @entry: dentry to add
 232  * @inode: The inode to attach to this dentry
 233  *
 234  * This adds the entry to the hash queues and initializes @inode.
 235  * The entry was actually filled in earlier during d_alloc().
 236  */
 237
 238 static inline void d_add(struct dentry *entry, struct inode *inode)
 239 {
 240         d_instantiate(entry, inode);
 241         d_rehash(entry);
 242 }
 243
 244 /**
 245  * d_add_unique - add dentry to hash queues without aliasing
 246  * @entry: dentry to add
 247  * @inode: The inode to attach to this dentry
 248  *
 249  * This adds the entry to the hash queues and initializes @inode.
 250  * The entry was actually filled in earlier during d_alloc().
 251  */
 252 static inline struct dentry *d_add_unique(struct dentry *entry, struct inode *inode)
 253 {
 254         struct dentry *res;
 255
 256         res = d_instantiate_unique(entry, inode);
 257         d_rehash(res != NULL ? res : entry);
 258         return res;
 259 }
 260
 261 extern void dentry_update_name_case(struct dentry *, struct qstr *);
 262
 263 /* used for rename() and baskets */
 264 extern void d_move(struct dentry *, struct dentry *);
 265 extern struct dentry *d_ancestor(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 extern struct dentry * d_hash_and_lookup(struct dentry *, struct qstr *);
 271
 272 /* validate "insecure" dentry pointer */
 273 extern int d_validate(struct dentry *, struct dentry *);
 274
 275 /*
 276  * helper function for dentry_operations.d_dname() members
 277  */
 278 extern char *dynamic_dname(struct dentry *, char *, int, const char *, ...);
 279
 280 extern char *__d_path(const struct path *path, struct path *root, char *, int);
 281 extern char *d_path(const struct path *, char *, int);
 282 extern char *d_path_with_unreachable(const struct path *, char *, int);
 283 extern char *dentry_path_raw(struct dentry *, char *, int);
 284 extern char *dentry_path(struct dentry *, char *, int);
 285
 286 /* Allocation counts.. */
 287
 288 /**
 289  *      dget, dget_locked       -       get a reference to a dentry
 290  *      @dentry: dentry to get a reference to
 291  *
 292  *      Given a dentry or %NULL pointer increment the reference count
 293  *      if appropriate and return the dentry. A dentry will not be
 294  *      destroyed when it has references. dget() should never be
 295  *      called for dentries with zero reference counter. For these cases
 296  *      (preferably none, functions in dcache.c are sufficient for normal
 297  *      needs and they take necessary precautions) you should hold dcache_lock
 298  *      and call dget_locked() instead of dget().
 299  */
 300
 301 static inline struct dentry *dget(struct dentry *dentry)
 302 {
 303         if (dentry) {
 304                 BUG_ON(!atomic_read(&dentry->d_count));
 305                 atomic_inc(&dentry->d_count);
 306         }
 307         return dentry;
 308 }
 309
 310 extern struct dentry * dget_locked(struct dentry *);
 311
 312 /**
 313  *      d_unhashed -    is dentry hashed
 314  *      @dentry: entry to check
 315  *
 316  *      Returns true if the dentry passed is not currently hashed.
 317  */
 318
 319 static inline int d_unhashed(struct dentry *dentry)
 320 {
 321         return (dentry->d_flags & DCACHE_UNHASHED);
 322 }
 323
 324 static inline int d_unlinked(struct dentry *dentry)
 325 {
 326         return d_unhashed(dentry) && !IS_ROOT(dentry);
 327 }
 328
 329 static inline int cant_mount(struct dentry *dentry)
 330 {
 331         return (dentry->d_flags & DCACHE_CANT_MOUNT);
 332 }
 333
 334 static inline void dont_mount(struct dentry *dentry)
 335 {
 336         spin_lock(&dentry->d_lock);
 337         dentry->d_flags |= DCACHE_CANT_MOUNT;
 338         spin_unlock(&dentry->d_lock);
 339 }
 340
 341 static inline struct dentry *dget_parent(struct dentry *dentry)
 342 {
 343         struct dentry *ret;
 344
 345         spin_lock(&dentry->d_lock);
 346         ret = dget(dentry->d_parent);
 347         spin_unlock(&dentry->d_lock);
 348         return ret;
 349 }
 350
 351 extern void dput(struct dentry *);
 352
 353 static inline int d_mountpoint(struct dentry *dentry)
 354 {
 355         return dentry->d_mounted;
 356 }
 357
 358 extern struct vfsmount *lookup_mnt(struct path *);
 359 extern struct dentry *lookup_create(struct nameidata *nd, int is_dir);
 360
 361 extern int sysctl_vfs_cache_pressure;
 362
 363 #endif  /* __LINUX_DCACHE_H */