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/seqlock.h>
   9 #include <linux/cache.h>
  10 #include <linux/rcupdate.h>
  11
  12 struct nameidata;
  13 struct path;
  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 /*
  80  * Try to keep struct dentry aligned on 64 byte cachelines (this will
  81  * give reasonable cacheline footprint with larger lines without the
  82  * large memory footprint increase).
  83  */
  84 #ifdef CONFIG_64BIT
  85 #define DNAME_INLINE_LEN_MIN 32 /* 192 bytes */
  86 #else
  87 #define DNAME_INLINE_LEN_MIN 40 /* 128 bytes */
  88 #endif
  89
  90 struct dentry {
  91         unsigned int d_count;           /* protected by d_lock */
  92         unsigned int d_flags;           /* protected by d_lock */
  93         spinlock_t d_lock;              /* per dentry lock */
  94         seqcount_t d_seq;               /* per dentry seqlock */
  95         int d_mounted;
  96         struct inode *d_inode;          /* Where the name belongs to - NULL is
  97                                          * negative */
  98         /*
  99          * The next three fields are touched by __d_lookup.  Place them here
 100          * so they all fit in a cache line.
 101          */
 102         struct hlist_node d_hash;       /* lookup hash list */
 103         struct dentry *d_parent;        /* parent directory */
 104         struct qstr d_name;
 105
 106         struct list_head d_lru;         /* LRU list */
 107         /*
 108          * d_child and d_rcu can share memory
 109          */
 110         union {
 111                 struct list_head d_child;       /* child of parent list */
 112                 struct rcu_head d_rcu;
 113         } d_u;
 114         struct list_head d_subdirs;     /* our children */
 115         struct list_head d_alias;       /* inode alias list */
 116         unsigned long d_time;           /* used by d_revalidate */
 117         const struct dentry_operations *d_op;
 118         struct super_block *d_sb;       /* The root of the dentry tree */
 119         void *d_fsdata;                 /* fs-specific data */
 120
 121         unsigned char d_iname[DNAME_INLINE_LEN_MIN];    /* small names */
 122 };
 123
 124 /*
 125  * dentry->d_lock spinlock nesting subclasses:
 126  *
 127  * 0: normal
 128  * 1: nested
 129  */
 130 enum dentry_d_lock_class
 131 {
 132         DENTRY_D_LOCK_NORMAL, /* implicitly used by plain spin_lock() APIs. */
 133         DENTRY_D_LOCK_NESTED
 134 };
 135
 136 struct dentry_operations {
 137         int (*d_revalidate)(struct dentry *, struct nameidata *);
 138         int (*d_hash)(const struct dentry *, const struct inode *,
 139                         struct qstr *);
 140         int (*d_compare)(const struct dentry *, const struct inode *,
 141                         const struct dentry *, const struct inode *,
 142                         unsigned int, const char *, const struct qstr *);
 143         int (*d_delete)(const struct dentry *);
 144         void (*d_release)(struct dentry *);
 145         void (*d_iput)(struct dentry *, struct inode *);
 146         char *(*d_dname)(struct dentry *, char *, int);
 147 };
 148
 149 /*
 150  * Locking rules for dentry_operations callbacks are to be found in
 151  * Documentation/filesystems/Locking. Keep it updated!
 152  *
 153  * FUrther descriptions are found in Documentation/filesystems/vfs.txt.
 154  * Keep it updated too!
 155  */
 156
 157 /* d_flags entries */
 158 #define DCACHE_AUTOFS_PENDING 0x0001    /* autofs: "under construction" */
 159 #define DCACHE_NFSFS_RENAMED  0x0002    /* this dentry has been "silly
 160                                          * renamed" and has to be
 161                                          * deleted on the last dput()
 162                                          */
 163 #define DCACHE_DISCONNECTED 0x0004
 164      /* This dentry is possibly not currently connected to the dcache tree,
 165       * in which case its parent will either be itself, or will have this
 166       * flag as well.  nfsd will not use a dentry with this bit set, but will
 167       * first endeavour to clear the bit either by discovering that it is
 168       * connected, or by performing lookup operations.   Any filesystem which
 169       * supports nfsd_operations MUST have a lookup function which, if it finds
 170       * a directory inode with a DCACHE_DISCONNECTED dentry, will d_move
 171       * that dentry into place and return that dentry rather than the passed one,
 172       * typically using d_splice_alias.
 173       */
 174
 175 #define DCACHE_REFERENCED       0x0008  /* Recently used, don't discard. */
 176 #define DCACHE_UNHASHED         0x0010
 177
 178 #define DCACHE_INOTIFY_PARENT_WATCHED   0x0020 /* Parent inode is watched by inotify */
 179
 180 #define DCACHE_COOKIE           0x0040  /* For use by dcookie subsystem */
 181
 182 #define DCACHE_FSNOTIFY_PARENT_WATCHED  0x0080 /* Parent inode is watched by some fsnotify listener */
 183
 184 #define DCACHE_CANT_MOUNT       0x0100
 185 #define DCACHE_GENOCIDE         0x0200
 186
 187 extern spinlock_t dcache_inode_lock;
 188 extern seqlock_t rename_lock;
 189
 190 static inline int dname_external(struct dentry *dentry)
 191 {
 192         return dentry->d_name.name != dentry->d_iname;
 193 }
 194
 195 /*
 196  * These are the low-level FS interfaces to the dcache..
 197  */
 198 extern void d_instantiate(struct dentry *, struct inode *);
 199 extern struct dentry * d_instantiate_unique(struct dentry *, struct inode *);
 200 extern struct dentry * d_materialise_unique(struct dentry *, struct inode *);
 201 extern void __d_drop(struct dentry *dentry);
 202 extern void d_drop(struct dentry *dentry);
 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_splice_alias(struct inode *, struct dentry *);
 208 extern struct dentry * d_add_ci(struct dentry *, struct inode *, struct qstr *);
 209 extern struct dentry * d_obtain_alias(struct inode *);
 210 extern void shrink_dcache_sb(struct super_block *);
 211 extern void shrink_dcache_parent(struct dentry *);
 212 extern void shrink_dcache_for_umount(struct super_block *);
 213 extern int d_invalidate(struct dentry *);
 214
 215 /* only used at mount-time */
 216 extern struct dentry * d_alloc_root(struct inode *);
 217
 218 /* <clickety>-<click> the ramfs-type tree */
 219 extern void d_genocide(struct dentry *);
 220
 221 extern struct dentry *d_find_alias(struct inode *);
 222 extern void d_prune_aliases(struct inode *);
 223
 224 /* test whether we have any submounts in a subdir tree */
 225 extern int have_submounts(struct dentry *);
 226
 227 /*
 228  * This adds the entry to the hash queues.
 229  */
 230 extern void d_rehash(struct dentry *);
 231
 232 /**
 233  * d_add - add dentry to hash queues
 234  * @entry: dentry to add
 235  * @inode: The inode to attach to this dentry
 236  *
 237  * This adds the entry to the hash queues and initializes @inode.
 238  * The entry was actually filled in earlier during d_alloc().
 239  */
 240
 241 static inline void d_add(struct dentry *entry, struct inode *inode)
 242 {
 243         d_instantiate(entry, inode);
 244         d_rehash(entry);
 245 }
 246
 247 /**
 248  * d_add_unique - add dentry to hash queues without aliasing
 249  * @entry: dentry to add
 250  * @inode: The inode to attach to this dentry
 251  *
 252  * This adds the entry to the hash queues and initializes @inode.
 253  * The entry was actually filled in earlier during d_alloc().
 254  */
 255 static inline struct dentry *d_add_unique(struct dentry *entry, struct inode *inode)
 256 {
 257         struct dentry *res;
 258
 259         res = d_instantiate_unique(entry, inode);
 260         d_rehash(res != NULL ? res : entry);
 261         return res;
 262 }
 263
 264 extern void dentry_update_name_case(struct dentry *, struct qstr *);
 265
 266 /* used for rename() and baskets */
 267 extern void d_move(struct dentry *, struct dentry *);
 268 extern struct dentry *d_ancestor(struct dentry *, struct dentry *);
 269
 270 /* appendix may either be NULL or be used for transname suffixes */
 271 extern struct dentry *d_lookup(struct dentry *, struct qstr *);
 272 extern struct dentry *d_hash_and_lookup(struct dentry *, struct qstr *);
 273 extern struct dentry *__d_lookup(struct dentry *, struct qstr *);
 274 extern struct dentry *__d_lookup_rcu(struct dentry *parent, struct qstr *name,
 275                                 unsigned *seq, struct inode **inode);
 276
 277 /**
 278  * __d_rcu_to_refcount - take a refcount on dentry if sequence check is ok
 279  * @dentry: dentry to take a ref on
 280  * @seq: seqcount to verify against
 281  * @Returns: 0 on failure, else 1.
 282  *
 283  * __d_rcu_to_refcount operates on a dentry,seq pair that was returned
 284  * by __d_lookup_rcu, to get a reference on an rcu-walk dentry.
 285  */
 286 static inline int __d_rcu_to_refcount(struct dentry *dentry, unsigned seq)
 287 {
 288         int ret = 0;
 289
 290         assert_spin_locked(&dentry->d_lock);
 291         if (!read_seqcount_retry(&dentry->d_seq, seq)) {
 292                 ret = 1;
 293                 dentry->d_count++;
 294         }
 295
 296         return ret;
 297 }
 298
 299 /* validate "insecure" dentry pointer */
 300 extern int d_validate(struct dentry *, struct dentry *);
 301
 302 /*
 303  * helper function for dentry_operations.d_dname() members
 304  */
 305 extern char *dynamic_dname(struct dentry *, char *, int, const char *, ...);
 306
 307 extern char *__d_path(const struct path *path, struct path *root, char *, int);
 308 extern char *d_path(const struct path *, char *, int);
 309 extern char *d_path_with_unreachable(const struct path *, char *, int);
 310 extern char *dentry_path_raw(struct dentry *, char *, int);
 311 extern char *dentry_path(struct dentry *, char *, int);
 312
 313 /* Allocation counts.. */
 314
 315 /**
 316  *      dget, dget_dlock -      get a reference to a dentry
 317  *      @dentry: dentry to get a reference to
 318  *
 319  *      Given a dentry or %NULL pointer increment the reference count
 320  *      if appropriate and return the dentry. A dentry will not be
 321  *      destroyed when it has references.
 322  */
 323 static inline struct dentry *dget_dlock(struct dentry *dentry)
 324 {
 325         if (dentry)
 326                 dentry->d_count++;
 327         return dentry;
 328 }
 329
 330 static inline struct dentry *dget(struct dentry *dentry)
 331 {
 332         if (dentry) {
 333                 spin_lock(&dentry->d_lock);
 334                 dget_dlock(dentry);
 335                 spin_unlock(&dentry->d_lock);
 336         }
 337         return dentry;
 338 }
 339
 340 extern struct dentry *dget_parent(struct dentry *dentry);
 341
 342 /**
 343  *      d_unhashed -    is dentry hashed
 344  *      @dentry: entry to check
 345  *
 346  *      Returns true if the dentry passed is not currently hashed.
 347  */
 348
 349 static inline int d_unhashed(struct dentry *dentry)
 350 {
 351         return (dentry->d_flags & DCACHE_UNHASHED);
 352 }
 353
 354 static inline int d_unlinked(struct dentry *dentry)
 355 {
 356         return d_unhashed(dentry) && !IS_ROOT(dentry);
 357 }
 358
 359 static inline int cant_mount(struct dentry *dentry)
 360 {
 361         return (dentry->d_flags & DCACHE_CANT_MOUNT);
 362 }
 363
 364 static inline void dont_mount(struct dentry *dentry)
 365 {
 366         spin_lock(&dentry->d_lock);
 367         dentry->d_flags |= DCACHE_CANT_MOUNT;
 368         spin_unlock(&dentry->d_lock);
 369 }
 370
 371 extern void dput(struct dentry *);
 372
 373 static inline int d_mountpoint(struct dentry *dentry)
 374 {
 375         return dentry->d_mounted;
 376 }
 377
 378 extern struct vfsmount *lookup_mnt(struct path *);
 379 extern struct dentry *lookup_create(struct nameidata *nd, int is_dir);
 380
 381 extern int sysctl_vfs_cache_pressure;
 382
 383 #endif  /* __LINUX_DCACHE_H */