include/linux/dcache.h

   1 #ifndef __LINUX_DCACHE_H
   2 #define __LINUX_DCACHE_H
   3
   4 #include <linux/atomic.h>
   5 #include <linux/list.h>
   6 #include <linux/rculist.h>
   7 #include <linux/rculist_bl.h>
   8 #include <linux/spinlock.h>
   9 #include <linux/seqlock.h>
  10 #include <linux/cache.h>
  11 #include <linux/rcupdate.h>
  12 #include <linux/lockref.h>
  13
  14 struct nameidata;
  15 struct path;
  16 struct vfsmount;
  17
  18 /*
  19  * linux/include/linux/dcache.h
  20  *
  21  * Dirent cache data structures
  22  *
  23  * (C) Copyright 1997 Thomas Schoebel-Theuer,
  24  * with heavy changes by Linus Torvalds
  25  */
  26
  27 #define IS_ROOT(x) ((x) == (x)->d_parent)
  28
  29 /* The hash is always the low bits of hash_len */
  30 #ifdef __LITTLE_ENDIAN
  31  #define HASH_LEN_DECLARE u32 hash; u32 len;
  32  #define bytemask_from_count(cnt)       (~(~0ul << (cnt)*8))
  33 #else
  34  #define HASH_LEN_DECLARE u32 len; u32 hash;
  35  #define bytemask_from_count(cnt)       (~(~0ul >> (cnt)*8))
  36 #endif
  37
  38 /*
  39  * "quick string" -- eases parameter passing, but more importantly
  40  * saves "metadata" about the string (ie length and the hash).
  41  *
  42  * hash comes first so it snuggles against d_parent in the
  43  * dentry.
  44  */
  45 struct qstr {
  46         union {
  47                 struct {
  48                         HASH_LEN_DECLARE;
  49                 };
  50                 u64 hash_len;
  51         };
  52         const unsigned char *name;
  53 };
  54
  55 #define QSTR_INIT(n,l) { { { .len = l } }, .name = n }
  56 #define hashlen_hash(hashlen) ((u32) (hashlen))
  57 #define hashlen_len(hashlen)  ((u32)((hashlen) >> 32))
  58
  59 struct dentry_stat_t {
  60         long nr_dentry;
  61         long nr_unused;
  62         long age_limit;          /* age in seconds */
  63         long want_pages;         /* pages requested by system */
  64         long dummy[2];
  65 };
  66 extern struct dentry_stat_t dentry_stat;
  67
  68 /* Name hashing routines. Initial hash value */
  69 /* Hash courtesy of the R5 hash in reiserfs modulo sign bits */
  70 #define init_name_hash()                0
  71
  72 /* partial hash update function. Assume roughly 4 bits per character */
  73 static inline unsigned long
  74 partial_name_hash(unsigned long c, unsigned long prevhash)
  75 {
  76         return (prevhash + (c << 4) + (c >> 4)) * 11;
  77 }
  78
  79 /*
  80  * Finally: cut down the number of bits to a int value (and try to avoid
  81  * losing bits)
  82  */
  83 static inline unsigned long end_name_hash(unsigned long hash)
  84 {
  85         return (unsigned int) hash;
  86 }
  87
  88 /* Compute the hash for a name string. */
  89 extern unsigned int full_name_hash(const unsigned char *, unsigned int);
  90
  91 /*
  92  * Try to keep struct dentry aligned on 64 byte cachelines (this will
  93  * give reasonable cacheline footprint with larger lines without the
  94  * large memory footprint increase).
  95  */
  96 #ifdef CONFIG_64BIT
  97 # define DNAME_INLINE_LEN 32 /* 192 bytes */
  98 #else
  99 # ifdef CONFIG_SMP
 100 #  define DNAME_INLINE_LEN 36 /* 128 bytes */
 101 # else
 102 #  define DNAME_INLINE_LEN 40 /* 128 bytes */
 103 # endif
 104 #endif
 105
 106 #define d_lock  d_lockref.lock
 107
 108 struct dentry {
 109         /* RCU lookup touched fields */
 110         unsigned int d_flags;           /* protected by d_lock */
 111         seqcount_t d_seq;               /* per dentry seqlock */
 112         struct hlist_bl_node d_hash;    /* lookup hash list */
 113         struct dentry *d_parent;        /* parent directory */
 114         struct qstr d_name;
 115         struct inode *d_inode;          /* Where the name belongs to - NULL is
 116                                          * negative */
 117         unsigned char d_iname[DNAME_INLINE_LEN];        /* small names */
 118
 119         /* Ref lookup also touches following */
 120         struct lockref d_lockref;       /* per-dentry lock and refcount */
 121         const struct dentry_operations *d_op;
 122         struct super_block *d_sb;       /* The root of the dentry tree */
 123         unsigned long d_time;           /* used by d_revalidate */
 124         void *d_fsdata;                 /* fs-specific data */
 125
 126         struct list_head d_lru;         /* LRU list */
 127         /*
 128          * d_child and d_rcu can share memory
 129          */
 130         union {
 131                 struct list_head d_child;       /* child of parent list */
 132                 struct rcu_head d_rcu;
 133         } d_u;
 134         struct list_head d_subdirs;     /* our children */
 135         struct hlist_node d_alias;      /* inode alias list */
 136 };
 137
 138 /*
 139  * dentry->d_lock spinlock nesting subclasses:
 140  *
 141  * 0: normal
 142  * 1: nested
 143  */
 144 enum dentry_d_lock_class
 145 {
 146         DENTRY_D_LOCK_NORMAL, /* implicitly used by plain spin_lock() APIs. */
 147         DENTRY_D_LOCK_NESTED
 148 };
 149
 150 struct dentry_operations {
 151         int (*d_revalidate)(struct dentry *, unsigned int);
 152         int (*d_weak_revalidate)(struct dentry *, unsigned int);
 153         int (*d_hash)(const struct dentry *, struct qstr *);
 154         int (*d_compare)(const struct dentry *, const struct dentry *,
 155                         unsigned int, const char *, const struct qstr *);
 156         int (*d_delete)(const struct dentry *);
 157         void (*d_release)(struct dentry *);
 158         void (*d_prune)(struct dentry *);
 159         void (*d_iput)(struct dentry *, struct inode *);
 160         char *(*d_dname)(struct dentry *, char *, int);
 161         struct vfsmount *(*d_automount)(struct path *);
 162         int (*d_manage)(struct dentry *, bool);
 163 } ____cacheline_aligned;
 164
 165 /*
 166  * Locking rules for dentry_operations callbacks are to be found in
 167  * Documentation/filesystems/Locking. Keep it updated!
 168  *
 169  * FUrther descriptions are found in Documentation/filesystems/vfs.txt.
 170  * Keep it updated too!
 171  */
 172
 173 /* d_flags entries */
 174 #define DCACHE_OP_HASH                  0x00000001
 175 #define DCACHE_OP_COMPARE               0x00000002
 176 #define DCACHE_OP_REVALIDATE            0x00000004
 177 #define DCACHE_OP_DELETE                0x00000008
 178 #define DCACHE_OP_PRUNE                 0x00000010
 179
 180 #define DCACHE_DISCONNECTED             0x00000020
 181      /* This dentry is possibly not currently connected to the dcache tree, in
 182       * which case its parent will either be itself, or will have this flag as
 183       * well.  nfsd will not use a dentry with this bit set, but will first
 184       * endeavour to clear the bit either by discovering that it is connected,
 185       * or by performing lookup operations.   Any filesystem which supports
 186       * nfsd_operations MUST have a lookup function which, if it finds a
 187       * directory inode with a DCACHE_DISCONNECTED dentry, will d_move that
 188       * dentry into place and return that dentry rather than the passed one,
 189       * typically using d_splice_alias. */
 190
 191 #define DCACHE_REFERENCED               0x00000040 /* Recently used, don't discard. */
 192 #define DCACHE_RCUACCESS                0x00000080 /* Entry has ever been RCU-visible */
 193
 194 #define DCACHE_CANT_MOUNT               0x00000100
 195 #define DCACHE_GENOCIDE                 0x00000200
 196 #define DCACHE_SHRINK_LIST              0x00000400
 197
 198 #define DCACHE_OP_WEAK_REVALIDATE       0x00000800
 199
 200 #define DCACHE_NFSFS_RENAMED            0x00001000
 201      /* this dentry has been "silly renamed" and has to be deleted on the last
 202       * dput() */
 203 #define DCACHE_COOKIE                   0x00002000 /* For use by dcookie subsystem */
 204 #define DCACHE_FSNOTIFY_PARENT_WATCHED  0x00004000
 205      /* Parent inode is watched by some fsnotify listener */
 206
 207 #define DCACHE_DENTRY_KILLED            0x00008000
 208
 209 #define DCACHE_MOUNTED                  0x00010000 /* is a mountpoint */
 210 #define DCACHE_NEED_AUTOMOUNT           0x00020000 /* handle automount on this dir */
 211 #define DCACHE_MANAGE_TRANSIT           0x00040000 /* manage transit from this dirent */
 212 #define DCACHE_MANAGED_DENTRY \
 213         (DCACHE_MOUNTED|DCACHE_NEED_AUTOMOUNT|DCACHE_MANAGE_TRANSIT)
 214
 215 #define DCACHE_LRU_LIST                 0x00080000
 216
 217 #define DCACHE_ENTRY_TYPE               0x00700000
 218 #define DCACHE_MISS_TYPE                0x00000000 /* Negative dentry */
 219 #define DCACHE_DIRECTORY_TYPE           0x00100000 /* Normal directory */
 220 #define DCACHE_AUTODIR_TYPE             0x00200000 /* Lookupless directory (presumed automount) */
 221 #define DCACHE_SYMLINK_TYPE             0x00300000 /* Symlink */
 222 #define DCACHE_FILE_TYPE                0x00400000 /* Other file type */
 223
 224 #define DCACHE_MAY_FREE                 0x00800000
 225
 226 extern seqlock_t rename_lock;
 227
 228 static inline int dname_external(const struct dentry *dentry)
 229 {
 230         return dentry->d_name.name != dentry->d_iname;
 231 }
 232
 233 /*
 234  * These are the low-level FS interfaces to the dcache..
 235  */
 236 extern void d_instantiate(struct dentry *, struct inode *);
 237 extern struct dentry * d_instantiate_unique(struct dentry *, struct inode *);
 238 extern struct dentry * d_materialise_unique(struct dentry *, struct inode *);
 239 extern int d_instantiate_no_diralias(struct dentry *, struct inode *);
 240 extern void __d_drop(struct dentry *dentry);
 241 extern void d_drop(struct dentry *dentry);
 242 extern void d_delete(struct dentry *);
 243 extern void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op);
 244
 245 /* allocate/de-allocate */
 246 extern struct dentry * d_alloc(struct dentry *, const struct qstr *);
 247 extern struct dentry * d_alloc_pseudo(struct super_block *, const struct qstr *);
 248 extern struct dentry * d_splice_alias(struct inode *, struct dentry *);
 249 extern struct dentry * d_add_ci(struct dentry *, struct inode *, struct qstr *);
 250 extern struct dentry *d_find_any_alias(struct inode *inode);
 251 extern struct dentry * d_obtain_alias(struct inode *);
 252 extern void shrink_dcache_sb(struct super_block *);
 253 extern void shrink_dcache_parent(struct dentry *);
 254 extern void shrink_dcache_for_umount(struct super_block *);
 255 extern int d_invalidate(struct dentry *);
 256
 257 /* only used at mount-time */
 258 extern struct dentry * d_make_root(struct inode *);
 259
 260 /* <clickety>-<click> the ramfs-type tree */
 261 extern void d_genocide(struct dentry *);
 262
 263 extern void d_tmpfile(struct dentry *, struct inode *);
 264
 265 extern struct dentry *d_find_alias(struct inode *);
 266 extern void d_prune_aliases(struct inode *);
 267
 268 /* test whether we have any submounts in a subdir tree */
 269 extern int have_submounts(struct dentry *);
 270 extern int check_submounts_and_drop(struct dentry *);
 271
 272 /*
 273  * This adds the entry to the hash queues.
 274  */
 275 extern void d_rehash(struct dentry *);
 276
 277 /**
 278  * d_add - add dentry to hash queues
 279  * @entry: dentry to add
 280  * @inode: The inode to attach to this dentry
 281  *
 282  * This adds the entry to the hash queues and initializes @inode.
 283  * The entry was actually filled in earlier during d_alloc().
 284  */
 285
 286 static inline void d_add(struct dentry *entry, struct inode *inode)
 287 {
 288         d_instantiate(entry, inode);
 289         d_rehash(entry);
 290 }
 291
 292 /**
 293  * d_add_unique - add dentry to hash queues without aliasing
 294  * @entry: dentry to add
 295  * @inode: The inode to attach to this dentry
 296  *
 297  * This adds the entry to the hash queues and initializes @inode.
 298  * The entry was actually filled in earlier during d_alloc().
 299  */
 300 static inline struct dentry *d_add_unique(struct dentry *entry, struct inode *inode)
 301 {
 302         struct dentry *res;
 303
 304         res = d_instantiate_unique(entry, inode);
 305         d_rehash(res != NULL ? res : entry);
 306         return res;
 307 }
 308
 309 extern void dentry_update_name_case(struct dentry *, struct qstr *);
 310
 311 /* used for rename() and baskets */
 312 extern void d_move(struct dentry *, struct dentry *);
 313 extern void d_exchange(struct dentry *, struct dentry *);
 314 extern struct dentry *d_ancestor(struct dentry *, struct dentry *);
 315
 316 /* appendix may either be NULL or be used for transname suffixes */
 317 extern struct dentry *d_lookup(const struct dentry *, const struct qstr *);
 318 extern struct dentry *d_hash_and_lookup(struct dentry *, struct qstr *);
 319 extern struct dentry *__d_lookup(const struct dentry *, const struct qstr *);
 320 extern struct dentry *__d_lookup_rcu(const struct dentry *parent,
 321                                 const struct qstr *name, unsigned *seq);
 322
 323 static inline unsigned d_count(const struct dentry *dentry)
 324 {
 325         return dentry->d_lockref.count;
 326 }
 327
 328 /* validate "insecure" dentry pointer */
 329 extern int d_validate(struct dentry *, struct dentry *);
 330
 331 /*
 332  * helper function for dentry_operations.d_dname() members
 333  */
 334 extern char *dynamic_dname(struct dentry *, char *, int, const char *, ...);
 335 extern char *simple_dname(struct dentry *, char *, int);
 336
 337 extern char *__d_path(const struct path *, const struct path *, char *, int);
 338 extern char *d_absolute_path(const struct path *, char *, int);
 339 extern char *d_path(const struct path *, char *, int);
 340 extern char *dentry_path_raw(struct dentry *, char *, int);
 341 extern char *dentry_path(struct dentry *, char *, int);
 342
 343 /* Allocation counts.. */
 344
 345 /**
 346  *      dget, dget_dlock -      get a reference to a dentry
 347  *      @dentry: dentry to get a reference to
 348  *
 349  *      Given a dentry or %NULL pointer increment the reference count
 350  *      if appropriate and return the dentry. A dentry will not be
 351  *      destroyed when it has references.
 352  */
 353 static inline struct dentry *dget_dlock(struct dentry *dentry)
 354 {
 355         if (dentry)
 356                 dentry->d_lockref.count++;
 357         return dentry;
 358 }
 359
 360 static inline struct dentry *dget(struct dentry *dentry)
 361 {
 362         if (dentry)
 363                 lockref_get(&dentry->d_lockref);
 364         return dentry;
 365 }
 366
 367 extern struct dentry *dget_parent(struct dentry *dentry);
 368
 369 /**
 370  *      d_unhashed -    is dentry hashed
 371  *      @dentry: entry to check
 372  *
 373  *      Returns true if the dentry passed is not currently hashed.
 374  */
 375
 376 static inline int d_unhashed(const struct dentry *dentry)
 377 {
 378         return hlist_bl_unhashed(&dentry->d_hash);
 379 }
 380
 381 static inline int d_unlinked(const struct dentry *dentry)
 382 {
 383         return d_unhashed(dentry) && !IS_ROOT(dentry);
 384 }
 385
 386 static inline int cant_mount(const struct dentry *dentry)
 387 {
 388         return (dentry->d_flags & DCACHE_CANT_MOUNT);
 389 }
 390
 391 static inline void dont_mount(struct dentry *dentry)
 392 {
 393         spin_lock(&dentry->d_lock);
 394         dentry->d_flags |= DCACHE_CANT_MOUNT;
 395         spin_unlock(&dentry->d_lock);
 396 }
 397
 398 extern void dput(struct dentry *);
 399
 400 static inline bool d_managed(const struct dentry *dentry)
 401 {
 402         return dentry->d_flags & DCACHE_MANAGED_DENTRY;
 403 }
 404
 405 static inline bool d_mountpoint(const struct dentry *dentry)
 406 {
 407         return dentry->d_flags & DCACHE_MOUNTED;
 408 }
 409
 410 /*
 411  * Directory cache entry type accessor functions.
 412  */
 413 static inline void __d_set_type(struct dentry *dentry, unsigned type)
 414 {
 415         dentry->d_flags = (dentry->d_flags & ~DCACHE_ENTRY_TYPE) | type;
 416 }
 417
 418 static inline void __d_clear_type(struct dentry *dentry)
 419 {
 420         __d_set_type(dentry, DCACHE_MISS_TYPE);
 421 }
 422
 423 static inline void d_set_type(struct dentry *dentry, unsigned type)
 424 {
 425         spin_lock(&dentry->d_lock);
 426         __d_set_type(dentry, type);
 427         spin_unlock(&dentry->d_lock);
 428 }
 429
 430 static inline unsigned __d_entry_type(const struct dentry *dentry)
 431 {
 432         return dentry->d_flags & DCACHE_ENTRY_TYPE;
 433 }
 434
 435 static inline bool d_can_lookup(const struct dentry *dentry)
 436 {
 437         return __d_entry_type(dentry) == DCACHE_DIRECTORY_TYPE;
 438 }
 439
 440 static inline bool d_is_autodir(const struct dentry *dentry)
 441 {
 442         return __d_entry_type(dentry) == DCACHE_AUTODIR_TYPE;
 443 }
 444
 445 static inline bool d_is_dir(const struct dentry *dentry)
 446 {
 447         return d_can_lookup(dentry) || d_is_autodir(dentry);
 448 }
 449
 450 static inline bool d_is_symlink(const struct dentry *dentry)
 451 {
 452         return __d_entry_type(dentry) == DCACHE_SYMLINK_TYPE;
 453 }
 454
 455 static inline bool d_is_file(const struct dentry *dentry)
 456 {
 457         return __d_entry_type(dentry) == DCACHE_FILE_TYPE;
 458 }
 459
 460 static inline bool d_is_negative(const struct dentry *dentry)
 461 {
 462         return __d_entry_type(dentry) == DCACHE_MISS_TYPE;
 463 }
 464
 465 static inline bool d_is_positive(const struct dentry *dentry)
 466 {
 467         return !d_is_negative(dentry);
 468 }
 469
 470 extern int sysctl_vfs_cache_pressure;
 471
 472 static inline unsigned long vfs_pressure_ratio(unsigned long val)
 473 {
 474         return mult_frac(val, sysctl_vfs_cache_pressure, 100);
 475 }
 476 #endif  /* __LINUX_DCACHE_H */