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 path;
  15 struct vfsmount;
  16
  17 /*
  18  * linux/include/linux/dcache.h
  19  *
  20  * Dirent cache data structures
  21  *
  22  * (C) Copyright 1997 Thomas Schoebel-Theuer,
  23  * with heavy changes by Linus Torvalds
  24  */
  25
  26 #define IS_ROOT(x) ((x) == (x)->d_parent)
  27
  28 /* The hash is always the low bits of hash_len */
  29 #ifdef __LITTLE_ENDIAN
  30  #define HASH_LEN_DECLARE u32 hash; u32 len;
  31  #define bytemask_from_count(cnt)       (~(~0ul << (cnt)*8))
  32 #else
  33  #define HASH_LEN_DECLARE u32 len; u32 hash;
  34  #define bytemask_from_count(cnt)       (~(~0ul >> (cnt)*8))
  35 #endif
  36
  37 /*
  38  * "quick string" -- eases parameter passing, but more importantly
  39  * saves "metadata" about the string (ie length and the hash).
  40  *
  41  * hash comes first so it snuggles against d_parent in the
  42  * dentry.
  43  */
  44 struct qstr {
  45         union {
  46                 struct {
  47                         HASH_LEN_DECLARE;
  48                 };
  49                 u64 hash_len;
  50         };
  51         const unsigned char *name;
  52 };
  53
  54 #define QSTR_INIT(n,l) { { { .len = l } }, .name = n }
  55 #define hashlen_hash(hashlen) ((u32) (hashlen))
  56 #define hashlen_len(hashlen)  ((u32)((hashlen) >> 32))
  57 #define hashlen_create(hash,len) (((u64)(len)<<32)|(u32)(hash))
  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 /*
 229  * These are the low-level FS interfaces to the dcache..
 230  */
 231 extern void d_instantiate(struct dentry *, struct inode *);
 232 extern struct dentry * d_instantiate_unique(struct dentry *, struct inode *);
 233 extern struct dentry * d_materialise_unique(struct dentry *, struct inode *);
 234 extern int d_instantiate_no_diralias(struct dentry *, struct inode *);
 235 extern void __d_drop(struct dentry *dentry);
 236 extern void d_drop(struct dentry *dentry);
 237 extern void d_delete(struct dentry *);
 238 extern void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op);
 239
 240 /* allocate/de-allocate */
 241 extern struct dentry * d_alloc(struct dentry *, const struct qstr *);
 242 extern struct dentry * d_alloc_pseudo(struct super_block *, const struct qstr *);
 243 extern struct dentry * d_splice_alias(struct inode *, struct dentry *);
 244 extern struct dentry * d_add_ci(struct dentry *, struct inode *, struct qstr *);
 245 extern struct dentry *d_find_any_alias(struct inode *inode);
 246 extern struct dentry * d_obtain_alias(struct inode *);
 247 extern struct dentry * d_obtain_root(struct inode *);
 248 extern void shrink_dcache_sb(struct super_block *);
 249 extern void shrink_dcache_parent(struct dentry *);
 250 extern void shrink_dcache_for_umount(struct super_block *);
 251 extern void d_invalidate(struct dentry *);
 252
 253 /* only used at mount-time */
 254 extern struct dentry * d_make_root(struct inode *);
 255
 256 /* <clickety>-<click> the ramfs-type tree */
 257 extern void d_genocide(struct dentry *);
 258
 259 extern void d_tmpfile(struct dentry *, struct inode *);
 260
 261 extern struct dentry *d_find_alias(struct inode *);
 262 extern void d_prune_aliases(struct inode *);
 263
 264 /* test whether we have any submounts in a subdir tree */
 265 extern int have_submounts(struct dentry *);
 266
 267 /*
 268  * This adds the entry to the hash queues.
 269  */
 270 extern void d_rehash(struct dentry *);
 271
 272 /**
 273  * d_add - add dentry to hash queues
 274  * @entry: dentry to add
 275  * @inode: The inode to attach to this dentry
 276  *
 277  * This adds the entry to the hash queues and initializes @inode.
 278  * The entry was actually filled in earlier during d_alloc().
 279  */
 280
 281 static inline void d_add(struct dentry *entry, struct inode *inode)
 282 {
 283         d_instantiate(entry, inode);
 284         d_rehash(entry);
 285 }
 286
 287 /**
 288  * d_add_unique - add dentry to hash queues without aliasing
 289  * @entry: dentry to add
 290  * @inode: The inode to attach to this dentry
 291  *
 292  * This adds the entry to the hash queues and initializes @inode.
 293  * The entry was actually filled in earlier during d_alloc().
 294  */
 295 static inline struct dentry *d_add_unique(struct dentry *entry, struct inode *inode)
 296 {
 297         struct dentry *res;
 298
 299         res = d_instantiate_unique(entry, inode);
 300         d_rehash(res != NULL ? res : entry);
 301         return res;
 302 }
 303
 304 extern void dentry_update_name_case(struct dentry *, struct qstr *);
 305
 306 /* used for rename() and baskets */
 307 extern void d_move(struct dentry *, struct dentry *);
 308 extern void d_exchange(struct dentry *, struct dentry *);
 309 extern struct dentry *d_ancestor(struct dentry *, struct dentry *);
 310
 311 /* appendix may either be NULL or be used for transname suffixes */
 312 extern struct dentry *d_lookup(const struct dentry *, const struct qstr *);
 313 extern struct dentry *d_hash_and_lookup(struct dentry *, struct qstr *);
 314 extern struct dentry *__d_lookup(const struct dentry *, const struct qstr *);
 315 extern struct dentry *__d_lookup_rcu(const struct dentry *parent,
 316                                 const struct qstr *name, unsigned *seq);
 317
 318 static inline unsigned d_count(const struct dentry *dentry)
 319 {
 320         return dentry->d_lockref.count;
 321 }
 322
 323 /* validate "insecure" dentry pointer */
 324 extern int d_validate(struct dentry *, struct dentry *);
 325
 326 /*
 327  * helper function for dentry_operations.d_dname() members
 328  */
 329 extern char *dynamic_dname(struct dentry *, char *, int, const char *, ...);
 330 extern char *simple_dname(struct dentry *, char *, int);
 331
 332 extern char *__d_path(const struct path *, const struct path *, char *, int);
 333 extern char *d_absolute_path(const struct path *, char *, int);
 334 extern char *d_path(const struct path *, char *, int);
 335 extern char *dentry_path_raw(struct dentry *, char *, int);
 336 extern char *dentry_path(struct dentry *, char *, int);
 337
 338 /* Allocation counts.. */
 339
 340 /**
 341  *      dget, dget_dlock -      get a reference to a dentry
 342  *      @dentry: dentry to get a reference to
 343  *
 344  *      Given a dentry or %NULL pointer increment the reference count
 345  *      if appropriate and return the dentry. A dentry will not be
 346  *      destroyed when it has references.
 347  */
 348 static inline struct dentry *dget_dlock(struct dentry *dentry)
 349 {
 350         if (dentry)
 351                 dentry->d_lockref.count++;
 352         return dentry;
 353 }
 354
 355 static inline struct dentry *dget(struct dentry *dentry)
 356 {
 357         if (dentry)
 358                 lockref_get(&dentry->d_lockref);
 359         return dentry;
 360 }
 361
 362 extern struct dentry *dget_parent(struct dentry *dentry);
 363
 364 /**
 365  *      d_unhashed -    is dentry hashed
 366  *      @dentry: entry to check
 367  *
 368  *      Returns true if the dentry passed is not currently hashed.
 369  */
 370
 371 static inline int d_unhashed(const struct dentry *dentry)
 372 {
 373         return hlist_bl_unhashed(&dentry->d_hash);
 374 }
 375
 376 static inline int d_unlinked(const struct dentry *dentry)
 377 {
 378         return d_unhashed(dentry) && !IS_ROOT(dentry);
 379 }
 380
 381 static inline int cant_mount(const struct dentry *dentry)
 382 {
 383         return (dentry->d_flags & DCACHE_CANT_MOUNT);
 384 }
 385
 386 static inline void dont_mount(struct dentry *dentry)
 387 {
 388         spin_lock(&dentry->d_lock);
 389         dentry->d_flags |= DCACHE_CANT_MOUNT;
 390         spin_unlock(&dentry->d_lock);
 391 }
 392
 393 extern void dput(struct dentry *);
 394
 395 static inline bool d_managed(const struct dentry *dentry)
 396 {
 397         return dentry->d_flags & DCACHE_MANAGED_DENTRY;
 398 }
 399
 400 static inline bool d_mountpoint(const struct dentry *dentry)
 401 {
 402         return dentry->d_flags & DCACHE_MOUNTED;
 403 }
 404
 405 /*
 406  * Directory cache entry type accessor functions.
 407  */
 408 static inline void __d_set_type(struct dentry *dentry, unsigned type)
 409 {
 410         dentry->d_flags = (dentry->d_flags & ~DCACHE_ENTRY_TYPE) | type;
 411 }
 412
 413 static inline void __d_clear_type(struct dentry *dentry)
 414 {
 415         __d_set_type(dentry, DCACHE_MISS_TYPE);
 416 }
 417
 418 static inline void d_set_type(struct dentry *dentry, unsigned type)
 419 {
 420         spin_lock(&dentry->d_lock);
 421         __d_set_type(dentry, type);
 422         spin_unlock(&dentry->d_lock);
 423 }
 424
 425 static inline unsigned __d_entry_type(const struct dentry *dentry)
 426 {
 427         return dentry->d_flags & DCACHE_ENTRY_TYPE;
 428 }
 429
 430 static inline bool d_can_lookup(const struct dentry *dentry)
 431 {
 432         return __d_entry_type(dentry) == DCACHE_DIRECTORY_TYPE;
 433 }
 434
 435 static inline bool d_is_autodir(const struct dentry *dentry)
 436 {
 437         return __d_entry_type(dentry) == DCACHE_AUTODIR_TYPE;
 438 }
 439
 440 static inline bool d_is_dir(const struct dentry *dentry)
 441 {
 442         return d_can_lookup(dentry) || d_is_autodir(dentry);
 443 }
 444
 445 static inline bool d_is_symlink(const struct dentry *dentry)
 446 {
 447         return __d_entry_type(dentry) == DCACHE_SYMLINK_TYPE;
 448 }
 449
 450 static inline bool d_is_file(const struct dentry *dentry)
 451 {
 452         return __d_entry_type(dentry) == DCACHE_FILE_TYPE;
 453 }
 454
 455 static inline bool d_is_negative(const struct dentry *dentry)
 456 {
 457         return __d_entry_type(dentry) == DCACHE_MISS_TYPE;
 458 }
 459
 460 static inline bool d_is_positive(const struct dentry *dentry)
 461 {
 462         return !d_is_negative(dentry);
 463 }
 464
 465 extern int sysctl_vfs_cache_pressure;
 466
 467 static inline unsigned long vfs_pressure_ratio(unsigned long val)
 468 {
 469         return mult_frac(val, sysctl_vfs_cache_pressure, 100);
 470 }
 471 #endif  /* __LINUX_DCACHE_H */