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        struct inode *(*d_select_inode)(struct dentry *, unsigned);
 164} ____cacheline_aligned;
 165
 166/*
 167 * Locking rules for dentry_operations callbacks are to be found in
 168 * Documentation/filesystems/Locking. Keep it updated!
 169 *
 170 * FUrther descriptions are found in Documentation/filesystems/vfs.txt.
 171 * Keep it updated too!
 172 */
 173
 174/* d_flags entries */
 175#define DCACHE_OP_HASH                  0x00000001
 176#define DCACHE_OP_COMPARE               0x00000002
 177#define DCACHE_OP_REVALIDATE            0x00000004
 178#define DCACHE_OP_DELETE                0x00000008
 179#define DCACHE_OP_PRUNE                 0x00000010
 180
 181#define DCACHE_DISCONNECTED             0x00000020
 182     /* This dentry is possibly not currently connected to the dcache tree, in
 183      * which case its parent will either be itself, or will have this flag as
 184      * well.  nfsd will not use a dentry with this bit set, but will first
 185      * endeavour to clear the bit either by discovering that it is connected,
 186      * or by performing lookup operations.   Any filesystem which supports
 187      * nfsd_operations MUST have a lookup function which, if it finds a
 188      * directory inode with a DCACHE_DISCONNECTED dentry, will d_move that
 189      * dentry into place and return that dentry rather than the passed one,
 190      * typically using d_splice_alias. */
 191
 192#define DCACHE_REFERENCED               0x00000040 /* Recently used, don't discard. */
 193#define DCACHE_RCUACCESS                0x00000080 /* Entry has ever been RCU-visible */
 194
 195#define DCACHE_CANT_MOUNT               0x00000100
 196#define DCACHE_GENOCIDE                 0x00000200
 197#define DCACHE_SHRINK_LIST              0x00000400
 198
 199#define DCACHE_OP_WEAK_REVALIDATE       0x00000800
 200
 201#define DCACHE_NFSFS_RENAMED            0x00001000
 202     /* this dentry has been "silly renamed" and has to be deleted on the last
 203      * dput() */
 204#define DCACHE_COOKIE                   0x00002000 /* For use by dcookie subsystem */
 205#define DCACHE_FSNOTIFY_PARENT_WATCHED  0x00004000
 206     /* Parent inode is watched by some fsnotify listener */
 207
 208#define DCACHE_DENTRY_KILLED            0x00008000
 209
 210#define DCACHE_MOUNTED                  0x00010000 /* is a mountpoint */
 211#define DCACHE_NEED_AUTOMOUNT           0x00020000 /* handle automount on this dir */
 212#define DCACHE_MANAGE_TRANSIT           0x00040000 /* manage transit from this dirent */
 213#define DCACHE_MANAGED_DENTRY \
 214        (DCACHE_MOUNTED|DCACHE_NEED_AUTOMOUNT|DCACHE_MANAGE_TRANSIT)
 215
 216#define DCACHE_LRU_LIST                 0x00080000
 217
 218#define DCACHE_ENTRY_TYPE               0x00700000
 219#define DCACHE_MISS_TYPE                0x00000000 /* Negative dentry */
 220#define DCACHE_DIRECTORY_TYPE           0x00100000 /* Normal directory */
 221#define DCACHE_AUTODIR_TYPE             0x00200000 /* Lookupless directory (presumed automount) */
 222#define DCACHE_SYMLINK_TYPE             0x00300000 /* Symlink */
 223#define DCACHE_FILE_TYPE                0x00400000 /* Other file type */
 224
 225#define DCACHE_MAY_FREE                 0x00800000
 226#define DCACHE_OP_SELECT_INODE          0x02000000 /* Unioned entry: dcache op selects inode */
 227
 228extern seqlock_t rename_lock;
 229
 230/*
 231 * These are the low-level FS interfaces to the dcache..
 232 */
 233extern void d_instantiate(struct dentry *, struct inode *);
 234extern void d_instantiate_new(struct dentry *, struct inode *);
 235extern struct dentry * d_instantiate_unique(struct dentry *, struct inode *);
 236extern struct dentry * d_materialise_unique(struct dentry *, struct inode *);
 237extern int d_instantiate_no_diralias(struct dentry *, struct inode *);
 238extern void __d_drop(struct dentry *dentry);
 239extern void d_drop(struct dentry *dentry);
 240extern void d_delete(struct dentry *);
 241extern void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op);
 242
 243/* allocate/de-allocate */
 244extern struct dentry * d_alloc(struct dentry *, const struct qstr *);
 245extern struct dentry * d_alloc_pseudo(struct super_block *, const struct qstr *);
 246extern struct dentry * d_splice_alias(struct inode *, struct dentry *);
 247extern struct dentry * d_add_ci(struct dentry *, struct inode *, struct qstr *);
 248extern struct dentry *d_find_any_alias(struct inode *inode);
 249extern struct dentry * d_obtain_alias(struct inode *);
 250extern struct dentry * d_obtain_root(struct inode *);
 251extern void shrink_dcache_sb(struct super_block *);
 252extern void shrink_dcache_parent(struct dentry *);
 253extern void shrink_dcache_for_umount(struct super_block *);
 254extern void d_invalidate(struct dentry *);
 255
 256/* only used at mount-time */
 257extern struct dentry * d_make_root(struct inode *);
 258
 259/* <clickety>-<click> the ramfs-type tree */
 260extern void d_genocide(struct dentry *);
 261
 262extern void d_tmpfile(struct dentry *, struct inode *);
 263
 264extern struct dentry *d_find_alias(struct inode *);
 265extern void d_prune_aliases(struct inode *);
 266
 267/* test whether we have any submounts in a subdir tree */
 268extern int have_submounts(struct dentry *);
 269
 270/*
 271 * This adds the entry to the hash queues.
 272 */
 273extern void d_rehash(struct dentry *);
 274
 275/**
 276 * d_add - add dentry to hash queues
 277 * @entry: dentry to add
 278 * @inode: The inode to attach to this dentry
 279 *
 280 * This adds the entry to the hash queues and initializes @inode.
 281 * The entry was actually filled in earlier during d_alloc().
 282 */
 283 
 284static inline void d_add(struct dentry *entry, struct inode *inode)
 285{
 286        d_instantiate(entry, inode);
 287        d_rehash(entry);
 288}
 289
 290/**
 291 * d_add_unique - add dentry to hash queues without aliasing
 292 * @entry: dentry to add
 293 * @inode: The inode to attach to this dentry
 294 *
 295 * This adds the entry to the hash queues and initializes @inode.
 296 * The entry was actually filled in earlier during d_alloc().
 297 */
 298static inline struct dentry *d_add_unique(struct dentry *entry, struct inode *inode)
 299{
 300        struct dentry *res;
 301
 302        res = d_instantiate_unique(entry, inode);
 303        d_rehash(res != NULL ? res : entry);
 304        return res;
 305}
 306
 307extern void dentry_update_name_case(struct dentry *, struct qstr *);
 308
 309/* used for rename() and baskets */
 310extern void d_move(struct dentry *, struct dentry *);
 311extern void d_exchange(struct dentry *, struct dentry *);
 312extern struct dentry *d_ancestor(struct dentry *, struct dentry *);
 313
 314/* appendix may either be NULL or be used for transname suffixes */
 315extern struct dentry *d_lookup(const struct dentry *, const struct qstr *);
 316extern struct dentry *d_hash_and_lookup(struct dentry *, struct qstr *);
 317extern struct dentry *__d_lookup(const struct dentry *, const struct qstr *);
 318extern struct dentry *__d_lookup_rcu(const struct dentry *parent,
 319                                const struct qstr *name, unsigned *seq);
 320
 321static inline unsigned d_count(const struct dentry *dentry)
 322{
 323        return dentry->d_lockref.count;
 324}
 325
 326/* validate "insecure" dentry pointer */
 327extern int d_validate(struct dentry *, struct dentry *);
 328
 329/*
 330 * helper function for dentry_operations.d_dname() members
 331 */
 332extern char *dynamic_dname(struct dentry *, char *, int, const char *, ...);
 333extern char *simple_dname(struct dentry *, char *, int);
 334
 335extern char *__d_path(const struct path *, const struct path *, char *, int);
 336extern char *d_absolute_path(const struct path *, char *, int);
 337extern char *d_path(const struct path *, char *, int);
 338extern char *dentry_path_raw(struct dentry *, char *, int);
 339extern char *dentry_path(struct dentry *, char *, int);
 340
 341/* Allocation counts.. */
 342
 343/**
 344 *      dget, dget_dlock -      get a reference to a dentry
 345 *      @dentry: dentry to get a reference to
 346 *
 347 *      Given a dentry or %NULL pointer increment the reference count
 348 *      if appropriate and return the dentry. A dentry will not be 
 349 *      destroyed when it has references.
 350 */
 351static inline struct dentry *dget_dlock(struct dentry *dentry)
 352{
 353        if (dentry)
 354                dentry->d_lockref.count++;
 355        return dentry;
 356}
 357
 358static inline struct dentry *dget(struct dentry *dentry)
 359{
 360        if (dentry)
 361                lockref_get(&dentry->d_lockref);
 362        return dentry;
 363}
 364
 365extern struct dentry *dget_parent(struct dentry *dentry);
 366
 367/**
 368 *      d_unhashed -    is dentry hashed
 369 *      @dentry: entry to check
 370 *
 371 *      Returns true if the dentry passed is not currently hashed.
 372 */
 373 
 374static inline int d_unhashed(const struct dentry *dentry)
 375{
 376        return hlist_bl_unhashed(&dentry->d_hash);
 377}
 378
 379static inline int d_unlinked(const struct dentry *dentry)
 380{
 381        return d_unhashed(dentry) && !IS_ROOT(dentry);
 382}
 383
 384static inline int cant_mount(const struct dentry *dentry)
 385{
 386        return (dentry->d_flags & DCACHE_CANT_MOUNT);
 387}
 388
 389static inline void dont_mount(struct dentry *dentry)
 390{
 391        spin_lock(&dentry->d_lock);
 392        dentry->d_flags |= DCACHE_CANT_MOUNT;
 393        spin_unlock(&dentry->d_lock);
 394}
 395
 396extern void dput(struct dentry *);
 397
 398static inline bool d_managed(const struct dentry *dentry)
 399{
 400        return dentry->d_flags & DCACHE_MANAGED_DENTRY;
 401}
 402
 403static inline bool d_mountpoint(const struct dentry *dentry)
 404{
 405        return dentry->d_flags & DCACHE_MOUNTED;
 406}
 407
 408/*
 409 * Directory cache entry type accessor functions.
 410 */
 411static inline void __d_set_type(struct dentry *dentry, unsigned type)
 412{
 413        dentry->d_flags = (dentry->d_flags & ~DCACHE_ENTRY_TYPE) | type;
 414}
 415
 416static inline void __d_clear_type(struct dentry *dentry)
 417{
 418        __d_set_type(dentry, DCACHE_MISS_TYPE);
 419}
 420
 421static inline void d_set_type(struct dentry *dentry, unsigned type)
 422{
 423        spin_lock(&dentry->d_lock);
 424        __d_set_type(dentry, type);
 425        spin_unlock(&dentry->d_lock);
 426}
 427
 428static inline unsigned __d_entry_type(const struct dentry *dentry)
 429{
 430        return dentry->d_flags & DCACHE_ENTRY_TYPE;
 431}
 432
 433static inline bool d_can_lookup(const struct dentry *dentry)
 434{
 435        return __d_entry_type(dentry) == DCACHE_DIRECTORY_TYPE;
 436}
 437
 438static inline bool d_is_autodir(const struct dentry *dentry)
 439{
 440        return __d_entry_type(dentry) == DCACHE_AUTODIR_TYPE;
 441}
 442
 443static inline bool d_is_dir(const struct dentry *dentry)
 444{
 445        return d_can_lookup(dentry) || d_is_autodir(dentry);
 446}
 447
 448static inline bool d_is_symlink(const struct dentry *dentry)
 449{
 450        return __d_entry_type(dentry) == DCACHE_SYMLINK_TYPE;
 451}
 452
 453static inline bool d_is_file(const struct dentry *dentry)
 454{
 455        return __d_entry_type(dentry) == DCACHE_FILE_TYPE;
 456}
 457
 458static inline bool d_is_negative(const struct dentry *dentry)
 459{
 460        return __d_entry_type(dentry) == DCACHE_MISS_TYPE;
 461}
 462
 463static inline bool d_is_positive(const struct dentry *dentry)
 464{
 465        return !d_is_negative(dentry);
 466}
 467
 468extern int sysctl_vfs_cache_pressure;
 469
 470static inline unsigned long vfs_pressure_ratio(unsigned long val)
 471{
 472        return mult_frac(val, sysctl_vfs_cache_pressure, 100);
 473}
 474
 475/**
 476 * d_inode - Get the actual inode of this dentry
 477 * @dentry: The dentry to query
 478 *
 479 * This is the helper normal filesystems should use to get at their own inodes
 480 * in their own dentries and ignore the layering superimposed upon them.
 481 */
 482static inline struct inode *d_inode(const struct dentry *dentry)
 483{
 484        return dentry->d_inode;
 485}
 486
 487/**
 488 * d_inode_rcu - Get the actual inode of this dentry with ACCESS_ONCE()
 489 * @dentry: The dentry to query
 490 *
 491 * This is the helper normal filesystems should use to get at their own inodes
 492 * in their own dentries and ignore the layering superimposed upon them.
 493 */
 494static inline struct inode *d_inode_rcu(const struct dentry *dentry)
 495{
 496        return ACCESS_ONCE(dentry->d_inode);
 497}
 498
 499/**
 500 * d_backing_inode - Get upper or lower inode we should be using
 501 * @upper: The upper layer
 502 *
 503 * This is the helper that should be used to get at the inode that will be used
 504 * if this dentry were to be opened as a file.  The inode may be on the upper
 505 * dentry or it may be on a lower dentry pinned by the upper.
 506 *
 507 * Normal filesystems should not use this to access their own inodes.
 508 */
 509static inline struct inode *d_backing_inode(const struct dentry *upper)
 510{
 511        struct inode *inode = upper->d_inode;
 512
 513        return inode;
 514}
 515
 516/**
 517 * d_backing_dentry - Get upper or lower dentry we should be using
 518 * @upper: The upper layer
 519 *
 520 * This is the helper that should be used to get the dentry of the inode that
 521 * will be used if this dentry were opened as a file.  It may be the upper
 522 * dentry or it may be a lower dentry pinned by the upper.
 523 *
 524 * Normal filesystems should not use this to access their own dentries.
 525 */
 526static inline struct dentry *d_backing_dentry(struct dentry *upper)
 527{
 528        return upper;
 529}
 530
 531struct name_snapshot {
 532        const char *name;
 533        char inline_name[DNAME_INLINE_LEN];
 534};
 535void take_dentry_name_snapshot(struct name_snapshot *, struct dentry *);
 536void release_dentry_name_snapshot(struct name_snapshot *);
 537
 538#endif  /* __LINUX_DCACHE_H */
 539
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