LXR linux/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
  13struct nameidata;
  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/*
  29 * "quick string" -- eases parameter passing, but more importantly
  30 * saves "metadata" about the string (ie length and the hash).
  31 *
  32 * hash comes first so it snuggles against d_parent in the
  33 * dentry.
  34 */
  35struct qstr {
  36        unsigned int hash;
  37        unsigned int len;
  38        const unsigned char *name;
  39};
  40
  41struct dentry_stat_t {
  42        int nr_dentry;
  43        int nr_unused;
  44        int age_limit;          /* age in seconds */
  45        int want_pages;         /* pages requested by system */
  46        int dummy[2];
  47};
  48extern struct dentry_stat_t dentry_stat;
  49
  50/*
  51 * Compare 2 name strings, return 0 if they match, otherwise non-zero.
  52 * The strings are both count bytes long, and count is non-zero.
  53 */
  54static inline int dentry_cmp(const unsigned char *cs, size_t scount,
  55                                const unsigned char *ct, size_t tcount)
  56{
  57        int ret;
  58        if (scount != tcount)
  59                return 1;
  60        do {
  61                ret = (*cs != *ct);
  62                if (ret)
  63                        break;
  64                cs++;
  65                ct++;
  66                tcount--;
  67        } while (tcount);
  68        return ret;
  69}
  70
  71/* Name hashing routines. Initial hash value */
  72/* Hash courtesy of the R5 hash in reiserfs modulo sign bits */
  73#define init_name_hash()                0
  74
  75/* partial hash update function. Assume roughly 4 bits per character */
  76static inline unsigned long
  77partial_name_hash(unsigned long c, unsigned long prevhash)
  78{
  79        return (prevhash + (c << 4) + (c >> 4)) * 11;
  80}
  81
  82/*
  83 * Finally: cut down the number of bits to a int value (and try to avoid
  84 * losing bits)
  85 */
  86static inline unsigned long end_name_hash(unsigned long hash)
  87{
  88        return (unsigned int) hash;
  89}
  90
  91/* Compute the hash for a name string. */
  92static inline unsigned int
  93full_name_hash(const unsigned char *name, unsigned int len)
  94{
  95        unsigned long hash = init_name_hash();
  96        while (len--)
  97                hash = partial_name_hash(*name++, hash);
  98        return end_name_hash(hash);
  99}
 100
 101/*
 102 * Try to keep struct dentry aligned on 64 byte cachelines (this will
 103 * give reasonable cacheline footprint with larger lines without the
 104 * large memory footprint increase).
 105 */
 106#ifdef CONFIG_64BIT
 107# define DNAME_INLINE_LEN 32 /* 192 bytes */
 108#else
 109# ifdef CONFIG_SMP
 110#  define DNAME_INLINE_LEN 36 /* 128 bytes */
 111# else
 112#  define DNAME_INLINE_LEN 40 /* 128 bytes */
 113# endif
 114#endif
 115
 116struct dentry {
 117        /* RCU lookup touched fields */
 118        unsigned int d_flags;           /* protected by d_lock */
 119        seqcount_t d_seq;               /* per dentry seqlock */
 120        struct hlist_bl_node d_hash;    /* lookup hash list */
 121        struct dentry *d_parent;        /* parent directory */
 122        struct qstr d_name;
 123        struct inode *d_inode;          /* Where the name belongs to - NULL is
 124                                         * negative */
 125        unsigned char d_iname[DNAME_INLINE_LEN];        /* small names */
 126
 127        /* Ref lookup also touches following */
 128        unsigned int d_count;           /* protected by d_lock */
 129        spinlock_t d_lock;              /* per dentry lock */
 130        const struct dentry_operations *d_op;
 131        struct super_block *d_sb;       /* The root of the dentry tree */
 132        unsigned long d_time;           /* used by d_revalidate */
 133        void *d_fsdata;                 /* fs-specific data */
 134
 135        struct list_head d_lru;         /* LRU list */
 136        /*
 137         * d_child and d_rcu can share memory
 138         */
 139        union {
 140                struct list_head d_child;       /* child of parent list */
 141                struct rcu_head d_rcu;
 142        } d_u;
 143        struct list_head d_subdirs;     /* our children */
 144        struct list_head d_alias;       /* inode alias list */
 145};
 146
 147/*
 148 * dentry->d_lock spinlock nesting subclasses:
 149 *
 150 * 0: normal
 151 * 1: nested
 152 */
 153enum dentry_d_lock_class
 154{
 155        DENTRY_D_LOCK_NORMAL, /* implicitly used by plain spin_lock() APIs. */
 156        DENTRY_D_LOCK_NESTED
 157};
 158
 159struct dentry_operations {
 160        int (*d_revalidate)(struct dentry *, struct nameidata *);
 161        int (*d_hash)(const struct dentry *, const struct inode *,
 162                        struct qstr *);
 163        int (*d_compare)(const struct dentry *, const struct inode *,
 164                        const struct dentry *, const struct inode *,
 165                        unsigned int, const char *, const struct qstr *);
 166        int (*d_delete)(const struct dentry *);
 167        void (*d_release)(struct dentry *);
 168        void (*d_iput)(struct dentry *, struct inode *);
 169        char *(*d_dname)(struct dentry *, char *, int);
 170        struct vfsmount *(*d_automount)(struct path *);
 171        int (*d_manage)(struct dentry *, bool);
 172} ____cacheline_aligned;
 173
 174/*
 175 * Locking rules for dentry_operations callbacks are to be found in
 176 * Documentation/filesystems/Locking. Keep it updated!
 177 *
 178 * FUrther descriptions are found in Documentation/filesystems/vfs.txt.
 179 * Keep it updated too!
 180 */
 181
 182/* d_flags entries */
 183#define DCACHE_OP_HASH          0x0001
 184#define DCACHE_OP_COMPARE       0x0002
 185#define DCACHE_OP_REVALIDATE    0x0004
 186#define DCACHE_OP_DELETE        0x0008
 187
 188#define DCACHE_DISCONNECTED     0x0010
 189     /* This dentry is possibly not currently connected to the dcache tree, in
 190      * which case its parent will either be itself, or will have this flag as
 191      * well.  nfsd will not use a dentry with this bit set, but will first
 192      * endeavour to clear the bit either by discovering that it is connected,
 193      * or by performing lookup operations.   Any filesystem which supports
 194      * nfsd_operations MUST have a lookup function which, if it finds a
 195      * directory inode with a DCACHE_DISCONNECTED dentry, will d_move that
 196      * dentry into place and return that dentry rather than the passed one,
 197      * typically using d_splice_alias. */
 198
 199#define DCACHE_REFERENCED       0x0020  /* Recently used, don't discard. */
 200#define DCACHE_RCUACCESS        0x0040  /* Entry has ever been RCU-visible */
 201
 202#define DCACHE_CANT_MOUNT       0x0100
 203#define DCACHE_GENOCIDE         0x0200
 204
 205#define DCACHE_NFSFS_RENAMED    0x1000
 206     /* this dentry has been "silly renamed" and has to be deleted on the last
 207      * dput() */
 208#define DCACHE_COOKIE           0x2000  /* For use by dcookie subsystem */
 209#define DCACHE_FSNOTIFY_PARENT_WATCHED 0x4000
 210     /* Parent inode is watched by some fsnotify listener */
 211
 212#define DCACHE_MOUNTED          0x10000 /* is a mountpoint */
 213#define DCACHE_NEED_AUTOMOUNT   0x20000 /* handle automount on this dir */
 214#define DCACHE_MANAGE_TRANSIT   0x40000 /* manage transit from this dirent */
 215#define DCACHE_NEED_LOOKUP      0x80000 /* dentry requires i_op->lookup */
 216#define DCACHE_MANAGED_DENTRY \
 217        (DCACHE_MOUNTED|DCACHE_NEED_AUTOMOUNT|DCACHE_MANAGE_TRANSIT)
 218
 219extern seqlock_t rename_lock;
 220
 221static inline int dname_external(struct dentry *dentry)
 222{
 223        return dentry->d_name.name != dentry->d_iname;
 224}
 225
 226/*
 227 * These are the low-level FS interfaces to the dcache..
 228 */
 229extern void d_instantiate(struct dentry *, struct inode *);
 230extern struct dentry * d_instantiate_unique(struct dentry *, struct inode *);
 231extern struct dentry * d_materialise_unique(struct dentry *, struct inode *);
 232extern void __d_drop(struct dentry *dentry);
 233extern void d_drop(struct dentry *dentry);
 234extern void d_delete(struct dentry *);
 235extern void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op);
 236
 237/* allocate/de-allocate */
 238extern struct dentry * d_alloc(struct dentry *, const struct qstr *);
 239extern struct dentry * d_alloc_pseudo(struct super_block *, const struct qstr *);
 240extern struct dentry * d_splice_alias(struct inode *, struct dentry *);
 241extern struct dentry * d_add_ci(struct dentry *, struct inode *, struct qstr *);
 242extern struct dentry * d_obtain_alias(struct inode *);
 243extern void shrink_dcache_sb(struct super_block *);
 244extern void shrink_dcache_parent(struct dentry *);
 245extern void shrink_dcache_for_umount(struct super_block *);
 246extern int d_invalidate(struct dentry *);
 247
 248/* only used at mount-time */
 249extern struct dentry * d_alloc_root(struct inode *);
 250
 251/* <clickety>-<click> the ramfs-type tree */
 252extern void d_genocide(struct dentry *);
 253
 254extern struct dentry *d_find_alias(struct inode *);
 255extern void d_prune_aliases(struct inode *);
 256
 257/* test whether we have any submounts in a subdir tree */
 258extern int have_submounts(struct dentry *);
 259
 260/*
 261 * This adds the entry to the hash queues.
 262 */
 263extern void d_rehash(struct dentry *);
 264
 265/**
 266 * d_add - add dentry to hash queues
 267 * @entry: dentry to add
 268 * @inode: The inode to attach to this dentry
 269 *
 270 * This adds the entry to the hash queues and initializes @inode.
 271 * The entry was actually filled in earlier during d_alloc().
 272 */
 273 
 274static inline void d_add(struct dentry *entry, struct inode *inode)
 275{
 276        d_instantiate(entry, inode);
 277        d_rehash(entry);
 278}
 279
 280/**
 281 * d_add_unique - add dentry to hash queues without aliasing
 282 * @entry: dentry to add
 283 * @inode: The inode to attach to this dentry
 284 *
 285 * This adds the entry to the hash queues and initializes @inode.
 286 * The entry was actually filled in earlier during d_alloc().
 287 */
 288static inline struct dentry *d_add_unique(struct dentry *entry, struct inode *inode)
 289{
 290        struct dentry *res;
 291
 292        res = d_instantiate_unique(entry, inode);
 293        d_rehash(res != NULL ? res : entry);
 294        return res;
 295}
 296
 297extern void dentry_update_name_case(struct dentry *, struct qstr *);
 298
 299/* used for rename() and baskets */
 300extern void d_move(struct dentry *, struct dentry *);
 301extern struct dentry *d_ancestor(struct dentry *, struct dentry *);
 302
 303/* appendix may either be NULL or be used for transname suffixes */
 304extern struct dentry *d_lookup(struct dentry *, struct qstr *);
 305extern struct dentry *d_hash_and_lookup(struct dentry *, struct qstr *);
 306extern struct dentry *__d_lookup(struct dentry *, struct qstr *);
 307extern struct dentry *__d_lookup_rcu(struct dentry *parent, struct qstr *name,
 308                                unsigned *seq, struct inode **inode);
 309
 310/**
 311 * __d_rcu_to_refcount - take a refcount on dentry if sequence check is ok
 312 * @dentry: dentry to take a ref on
 313 * @seq: seqcount to verify against
 314 * Returns: 0 on failure, else 1.
 315 *
 316 * __d_rcu_to_refcount operates on a dentry,seq pair that was returned
 317 * by __d_lookup_rcu, to get a reference on an rcu-walk dentry.
 318 */
 319static inline int __d_rcu_to_refcount(struct dentry *dentry, unsigned seq)
 320{
 321        int ret = 0;
 322
 323        assert_spin_locked(&dentry->d_lock);
 324        if (!read_seqcount_retry(&dentry->d_seq, seq)) {
 325                ret = 1;
 326                dentry->d_count++;
 327        }
 328
 329        return ret;
 330}
 331
 332/* validate "insecure" dentry pointer */
 333extern int d_validate(struct dentry *, struct dentry *);
 334
 335/*
 336 * helper function for dentry_operations.d_dname() members
 337 */
 338extern char *dynamic_dname(struct dentry *, char *, int, const char *, ...);
 339
 340extern char *__d_path(const struct path *path, struct path *root, char *, int);
 341extern char *d_path(const struct path *, char *, int);
 342extern char *d_path_with_unreachable(const struct path *, char *, int);
 343extern char *dentry_path_raw(struct dentry *, char *, int);
 344extern char *dentry_path(struct dentry *, char *, int);
 345
 346/* Allocation counts.. */
 347
 348/**
 349 *      dget, dget_dlock -      get a reference to a dentry
 350 *      @dentry: dentry to get a reference to
 351 *
 352 *      Given a dentry or %NULL pointer increment the reference count
 353 *      if appropriate and return the dentry. A dentry will not be 
 354 *      destroyed when it has references.
 355 */
 356static inline struct dentry *dget_dlock(struct dentry *dentry)
 357{
 358        if (dentry)
 359                dentry->d_count++;
 360        return dentry;
 361}
 362
 363static inline struct dentry *dget(struct dentry *dentry)
 364{
 365        if (dentry) {
 366                spin_lock(&dentry->d_lock);
 367                dget_dlock(dentry);
 368                spin_unlock(&dentry->d_lock);
 369        }
 370        return dentry;
 371}
 372
 373extern struct dentry *dget_parent(struct dentry *dentry);
 374
 375/**
 376 *      d_unhashed -    is dentry hashed
 377 *      @dentry: entry to check
 378 *
 379 *      Returns true if the dentry passed is not currently hashed.
 380 */
 381 
 382static inline int d_unhashed(struct dentry *dentry)
 383{
 384        return hlist_bl_unhashed(&dentry->d_hash);
 385}
 386
 387static inline int d_unlinked(struct dentry *dentry)
 388{
 389        return d_unhashed(dentry) && !IS_ROOT(dentry);
 390}
 391
 392static inline int cant_mount(struct dentry *dentry)
 393{
 394        return (dentry->d_flags & DCACHE_CANT_MOUNT);
 395}
 396
 397static inline void dont_mount(struct dentry *dentry)
 398{
 399        spin_lock(&dentry->d_lock);
 400        dentry->d_flags |= DCACHE_CANT_MOUNT;
 401        spin_unlock(&dentry->d_lock);
 402}
 403
 404extern void dput(struct dentry *);
 405
 406static inline bool d_managed(struct dentry *dentry)
 407{
 408        return dentry->d_flags & DCACHE_MANAGED_DENTRY;
 409}
 410
 411static inline bool d_mountpoint(struct dentry *dentry)
 412{
 413        return dentry->d_flags & DCACHE_MOUNTED;
 414}
 415
 416static inline bool d_need_lookup(struct dentry *dentry)
 417{
 418        return dentry->d_flags & DCACHE_NEED_LOOKUP;
 419}
 420
 421extern void d_clear_need_lookup(struct dentry *dentry);
 422
 423extern int sysctl_vfs_cache_pressure;
 424
 425#endif  /* __LINUX_DCACHE_H */
 426