linux/include/linux/dcache.h
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   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
  14struct path;
  15struct 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 */
  44struct 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
  59struct 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};
  66extern 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 */
  73static inline unsigned long
  74partial_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 */
  83static 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. */
  89extern 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
 108struct 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        struct list_head d_child;       /* child of parent list */
 128        struct list_head d_subdirs;     /* our children */
 129        /*
 130         * d_alias and d_rcu can share memory
 131         */
 132        union {
 133                struct hlist_node d_alias;      /* inode alias list */
 134                struct rcu_head d_rcu;
 135        } d_u;
 136};
 137
 138/*
 139 * dentry->d_lock spinlock nesting subclasses:
 140 *
 141 * 0: normal
 142 * 1: nested
 143 */
 144enum dentry_d_lock_class
 145{
 146        DENTRY_D_LOCK_NORMAL, /* implicitly used by plain spin_lock() APIs. */
 147        DENTRY_D_LOCK_NESTED
 148};
 149
 150struct 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
 226extern seqlock_t rename_lock;
 227
 228/*
 229 * These are the low-level FS interfaces to the dcache..
 230 */
 231extern void d_instantiate(struct dentry *, struct inode *);
 232extern struct dentry * d_instantiate_unique(struct dentry *, struct inode *);
 233extern int d_instantiate_no_diralias(struct dentry *, struct inode *);
 234extern void __d_drop(struct dentry *dentry);
 235extern void d_drop(struct dentry *dentry);
 236extern void d_delete(struct dentry *);
 237extern void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op);
 238
 239/* allocate/de-allocate */
 240extern struct dentry * d_alloc(struct dentry *, const struct qstr *);
 241extern struct dentry * d_alloc_pseudo(struct super_block *, const struct qstr *);
 242extern struct dentry * d_splice_alias(struct inode *, struct dentry *);
 243extern struct dentry * d_add_ci(struct dentry *, struct inode *, struct qstr *);
 244extern struct dentry *d_find_any_alias(struct inode *inode);
 245extern struct dentry * d_obtain_alias(struct inode *);
 246extern struct dentry * d_obtain_root(struct inode *);
 247extern void shrink_dcache_sb(struct super_block *);
 248extern void shrink_dcache_parent(struct dentry *);
 249extern void shrink_dcache_for_umount(struct super_block *);
 250extern void d_invalidate(struct dentry *);
 251
 252/* only used at mount-time */
 253extern struct dentry * d_make_root(struct inode *);
 254
 255/* <clickety>-<click> the ramfs-type tree */
 256extern void d_genocide(struct dentry *);
 257
 258extern void d_tmpfile(struct dentry *, struct inode *);
 259
 260extern struct dentry *d_find_alias(struct inode *);
 261extern void d_prune_aliases(struct inode *);
 262
 263/* test whether we have any submounts in a subdir tree */
 264extern int have_submounts(struct dentry *);
 265
 266/*
 267 * This adds the entry to the hash queues.
 268 */
 269extern void d_rehash(struct dentry *);
 270
 271/**
 272 * d_add - add dentry to hash queues
 273 * @entry: dentry to add
 274 * @inode: The inode to attach to this dentry
 275 *
 276 * This adds the entry to the hash queues and initializes @inode.
 277 * The entry was actually filled in earlier during d_alloc().
 278 */
 279 
 280static inline void d_add(struct dentry *entry, struct inode *inode)
 281{
 282        d_instantiate(entry, inode);
 283        d_rehash(entry);
 284}
 285
 286/**
 287 * d_add_unique - add dentry to hash queues without aliasing
 288 * @entry: dentry to add
 289 * @inode: The inode to attach to this dentry
 290 *
 291 * This adds the entry to the hash queues and initializes @inode.
 292 * The entry was actually filled in earlier during d_alloc().
 293 */
 294static inline struct dentry *d_add_unique(struct dentry *entry, struct inode *inode)
 295{
 296        struct dentry *res;
 297
 298        res = d_instantiate_unique(entry, inode);
 299        d_rehash(res != NULL ? res : entry);
 300        return res;
 301}
 302
 303extern void dentry_update_name_case(struct dentry *, struct qstr *);
 304
 305/* used for rename() and baskets */
 306extern void d_move(struct dentry *, struct dentry *);
 307extern void d_exchange(struct dentry *, struct dentry *);
 308extern struct dentry *d_ancestor(struct dentry *, struct dentry *);
 309
 310/* appendix may either be NULL or be used for transname suffixes */
 311extern struct dentry *d_lookup(const struct dentry *, const struct qstr *);
 312extern struct dentry *d_hash_and_lookup(struct dentry *, struct qstr *);
 313extern struct dentry *__d_lookup(const struct dentry *, const struct qstr *);
 314extern struct dentry *__d_lookup_rcu(const struct dentry *parent,
 315                                const struct qstr *name, unsigned *seq);
 316
 317static inline unsigned d_count(const struct dentry *dentry)
 318{
 319        return dentry->d_lockref.count;
 320}
 321
 322/* validate "insecure" dentry pointer */
 323extern int d_validate(struct dentry *, struct dentry *);
 324
 325/*
 326 * helper function for dentry_operations.d_dname() members
 327 */
 328extern char *dynamic_dname(struct dentry *, char *, int, const char *, ...);
 329extern char *simple_dname(struct dentry *, char *, int);
 330
 331extern char *__d_path(const struct path *, const struct path *, char *, int);
 332extern char *d_absolute_path(const struct path *, char *, int);
 333extern char *d_path(const struct path *, char *, int);
 334extern char *dentry_path_raw(struct dentry *, char *, int);
 335extern char *dentry_path(struct dentry *, char *, int);
 336
 337/* Allocation counts.. */
 338
 339/**
 340 *      dget, dget_dlock -      get a reference to a dentry
 341 *      @dentry: dentry to get a reference to
 342 *
 343 *      Given a dentry or %NULL pointer increment the reference count
 344 *      if appropriate and return the dentry. A dentry will not be 
 345 *      destroyed when it has references.
 346 */
 347static inline struct dentry *dget_dlock(struct dentry *dentry)
 348{
 349        if (dentry)
 350                dentry->d_lockref.count++;
 351        return dentry;
 352}
 353
 354static inline struct dentry *dget(struct dentry *dentry)
 355{
 356        if (dentry)
 357                lockref_get(&dentry->d_lockref);
 358        return dentry;
 359}
 360
 361extern struct dentry *dget_parent(struct dentry *dentry);
 362
 363/**
 364 *      d_unhashed -    is dentry hashed
 365 *      @dentry: entry to check
 366 *
 367 *      Returns true if the dentry passed is not currently hashed.
 368 */
 369 
 370static inline int d_unhashed(const struct dentry *dentry)
 371{
 372        return hlist_bl_unhashed(&dentry->d_hash);
 373}
 374
 375static inline int d_unlinked(const struct dentry *dentry)
 376{
 377        return d_unhashed(dentry) && !IS_ROOT(dentry);
 378}
 379
 380static inline int cant_mount(const struct dentry *dentry)
 381{
 382        return (dentry->d_flags & DCACHE_CANT_MOUNT);
 383}
 384
 385static inline void dont_mount(struct dentry *dentry)
 386{
 387        spin_lock(&dentry->d_lock);
 388        dentry->d_flags |= DCACHE_CANT_MOUNT;
 389        spin_unlock(&dentry->d_lock);
 390}
 391
 392extern void dput(struct dentry *);
 393
 394static inline bool d_managed(const struct dentry *dentry)
 395{
 396        return dentry->d_flags & DCACHE_MANAGED_DENTRY;
 397}
 398
 399static inline bool d_mountpoint(const struct dentry *dentry)
 400{
 401        return dentry->d_flags & DCACHE_MOUNTED;
 402}
 403
 404/*
 405 * Directory cache entry type accessor functions.
 406 */
 407static inline void __d_set_type(struct dentry *dentry, unsigned type)
 408{
 409        dentry->d_flags = (dentry->d_flags & ~DCACHE_ENTRY_TYPE) | type;
 410}
 411
 412static inline void __d_clear_type(struct dentry *dentry)
 413{
 414        __d_set_type(dentry, DCACHE_MISS_TYPE);
 415}
 416
 417static inline void d_set_type(struct dentry *dentry, unsigned type)
 418{
 419        spin_lock(&dentry->d_lock);
 420        __d_set_type(dentry, type);
 421        spin_unlock(&dentry->d_lock);
 422}
 423
 424static inline unsigned __d_entry_type(const struct dentry *dentry)
 425{
 426        return dentry->d_flags & DCACHE_ENTRY_TYPE;
 427}
 428
 429static inline bool d_can_lookup(const struct dentry *dentry)
 430{
 431        return __d_entry_type(dentry) == DCACHE_DIRECTORY_TYPE;
 432}
 433
 434static inline bool d_is_autodir(const struct dentry *dentry)
 435{
 436        return __d_entry_type(dentry) == DCACHE_AUTODIR_TYPE;
 437}
 438
 439static inline bool d_is_dir(const struct dentry *dentry)
 440{
 441        return d_can_lookup(dentry) || d_is_autodir(dentry);
 442}
 443
 444static inline bool d_is_symlink(const struct dentry *dentry)
 445{
 446        return __d_entry_type(dentry) == DCACHE_SYMLINK_TYPE;
 447}
 448
 449static inline bool d_is_file(const struct dentry *dentry)
 450{
 451        return __d_entry_type(dentry) == DCACHE_FILE_TYPE;
 452}
 453
 454static inline bool d_is_negative(const struct dentry *dentry)
 455{
 456        return __d_entry_type(dentry) == DCACHE_MISS_TYPE;
 457}
 458
 459static inline bool d_is_positive(const struct dentry *dentry)
 460{
 461        return !d_is_negative(dentry);
 462}
 463
 464extern int sysctl_vfs_cache_pressure;
 465
 466static inline unsigned long vfs_pressure_ratio(unsigned long val)
 467{
 468        return mult_frac(val, sysctl_vfs_cache_pressure, 100);
 469}
 470#endif  /* __LINUX_DCACHE_H */
 471
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