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/* Name hashing routines. Initial hash value */
  51/* Hash courtesy of the R5 hash in reiserfs modulo sign bits */
  52#define init_name_hash()                0
  53
  54/* partial hash update function. Assume roughly 4 bits per character */
  55static inline unsigned long
  56partial_name_hash(unsigned long c, unsigned long prevhash)
  57{
  58        return (prevhash + (c << 4) + (c >> 4)) * 11;
  59}
  60
  61/*
  62 * Finally: cut down the number of bits to a int value (and try to avoid
  63 * losing bits)
  64 */
  65static inline unsigned long end_name_hash(unsigned long hash)
  66{
  67        return (unsigned int) hash;
  68}
  69
  70/* Compute the hash for a name string. */
  71extern unsigned int full_name_hash(const unsigned char *, unsigned int);
  72
  73/*
  74 * Try to keep struct dentry aligned on 64 byte cachelines (this will
  75 * give reasonable cacheline footprint with larger lines without the
  76 * large memory footprint increase).
  77 */
  78#ifdef CONFIG_64BIT
  79# define DNAME_INLINE_LEN 32 /* 192 bytes */
  80#else
  81# ifdef CONFIG_SMP
  82#  define DNAME_INLINE_LEN 36 /* 128 bytes */
  83# else
  84#  define DNAME_INLINE_LEN 40 /* 128 bytes */
  85# endif
  86#endif
  87
  88struct dentry {
  89        /* RCU lookup touched fields */
  90        unsigned int d_flags;           /* protected by d_lock */
  91        seqcount_t d_seq;               /* per dentry seqlock */
  92        struct hlist_bl_node d_hash;    /* lookup hash list */
  93        struct dentry *d_parent;        /* parent directory */
  94        struct qstr d_name;
  95        struct inode *d_inode;          /* Where the name belongs to - NULL is
  96                                         * negative */
  97        unsigned char d_iname[DNAME_INLINE_LEN];        /* small names */
  98
  99        /* Ref lookup also touches following */
 100        unsigned int d_count;           /* protected by d_lock */
 101        spinlock_t d_lock;              /* per dentry lock */
 102        const struct dentry_operations *d_op;
 103        struct super_block *d_sb;       /* The root of the dentry tree */
 104        unsigned long d_time;           /* used by d_revalidate */
 105        void *d_fsdata;                 /* fs-specific data */
 106
 107        struct list_head d_lru;         /* LRU list */
 108        /*
 109         * d_child and d_rcu can share memory
 110         */
 111        union {
 112                struct list_head d_child;       /* child of parent list */
 113                struct rcu_head d_rcu;
 114        } d_u;
 115        struct list_head d_subdirs;     /* our children */
 116        struct list_head d_alias;       /* inode alias list */
 117};
 118
 119/*
 120 * dentry->d_lock spinlock nesting subclasses:
 121 *
 122 * 0: normal
 123 * 1: nested
 124 */
 125enum dentry_d_lock_class
 126{
 127        DENTRY_D_LOCK_NORMAL, /* implicitly used by plain spin_lock() APIs. */
 128        DENTRY_D_LOCK_NESTED
 129};
 130
 131struct dentry_operations {
 132        int (*d_revalidate)(struct dentry *, struct nameidata *);
 133        int (*d_hash)(const struct dentry *, const struct inode *,
 134                        struct qstr *);
 135        int (*d_compare)(const struct dentry *, const struct inode *,
 136                        const struct dentry *, const struct inode *,
 137                        unsigned int, const char *, const struct qstr *);
 138        int (*d_delete)(const struct dentry *);
 139        void (*d_release)(struct dentry *);
 140        void (*d_prune)(struct dentry *);
 141        void (*d_iput)(struct dentry *, struct inode *);
 142        char *(*d_dname)(struct dentry *, char *, int);
 143        struct vfsmount *(*d_automount)(struct path *);
 144        int (*d_manage)(struct dentry *, bool);
 145} ____cacheline_aligned;
 146
 147/*
 148 * Locking rules for dentry_operations callbacks are to be found in
 149 * Documentation/filesystems/Locking. Keep it updated!
 150 *
 151 * FUrther descriptions are found in Documentation/filesystems/vfs.txt.
 152 * Keep it updated too!
 153 */
 154
 155/* d_flags entries */
 156#define DCACHE_OP_HASH          0x0001
 157#define DCACHE_OP_COMPARE       0x0002
 158#define DCACHE_OP_REVALIDATE    0x0004
 159#define DCACHE_OP_DELETE        0x0008
 160#define DCACHE_OP_PRUNE         0x0010
 161
 162#define DCACHE_DISCONNECTED     0x0020
 163     /* This dentry is possibly not currently connected to the dcache tree, in
 164      * which case its parent will either be itself, or will have this flag as
 165      * well.  nfsd will not use a dentry with this bit set, but will first
 166      * endeavour to clear the bit either by discovering that it is connected,
 167      * or by performing lookup operations.   Any filesystem which supports
 168      * nfsd_operations MUST have a lookup function which, if it finds a
 169      * directory inode with a DCACHE_DISCONNECTED dentry, will d_move that
 170      * dentry into place and return that dentry rather than the passed one,
 171      * typically using d_splice_alias. */
 172
 173#define DCACHE_REFERENCED       0x0040  /* Recently used, don't discard. */
 174#define DCACHE_RCUACCESS        0x0080  /* Entry has ever been RCU-visible */
 175
 176#define DCACHE_CANT_MOUNT       0x0100
 177#define DCACHE_GENOCIDE         0x0200
 178#define DCACHE_SHRINK_LIST      0x0400
 179
 180#define DCACHE_NFSFS_RENAMED    0x1000
 181     /* this dentry has been "silly renamed" and has to be deleted on the last
 182      * dput() */
 183#define DCACHE_COOKIE           0x2000  /* For use by dcookie subsystem */
 184#define DCACHE_FSNOTIFY_PARENT_WATCHED 0x4000
 185     /* Parent inode is watched by some fsnotify listener */
 186
 187#define DCACHE_MOUNTED          0x10000 /* is a mountpoint */
 188#define DCACHE_NEED_AUTOMOUNT   0x20000 /* handle automount on this dir */
 189#define DCACHE_MANAGE_TRANSIT   0x40000 /* manage transit from this dirent */
 190#define DCACHE_NEED_LOOKUP      0x80000 /* dentry requires i_op->lookup */
 191#define DCACHE_MANAGED_DENTRY \
 192        (DCACHE_MOUNTED|DCACHE_NEED_AUTOMOUNT|DCACHE_MANAGE_TRANSIT)
 193
 194extern seqlock_t rename_lock;
 195
 196static inline int dname_external(struct dentry *dentry)
 197{
 198        return dentry->d_name.name != dentry->d_iname;
 199}
 200
 201/*
 202 * These are the low-level FS interfaces to the dcache..
 203 */
 204extern void d_instantiate(struct dentry *, struct inode *);
 205extern struct dentry * d_instantiate_unique(struct dentry *, struct inode *);
 206extern struct dentry * d_materialise_unique(struct dentry *, struct inode *);
 207extern void __d_drop(struct dentry *dentry);
 208extern void d_drop(struct dentry *dentry);
 209extern void d_delete(struct dentry *);
 210extern void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op);
 211
 212/* allocate/de-allocate */
 213extern struct dentry * d_alloc(struct dentry *, const struct qstr *);
 214extern struct dentry * d_alloc_pseudo(struct super_block *, const struct qstr *);
 215extern struct dentry * d_splice_alias(struct inode *, struct dentry *);
 216extern struct dentry * d_add_ci(struct dentry *, struct inode *, struct qstr *);
 217extern struct dentry *d_find_any_alias(struct inode *inode);
 218extern struct dentry * d_obtain_alias(struct inode *);
 219extern void shrink_dcache_sb(struct super_block *);
 220extern void shrink_dcache_parent(struct dentry *);
 221extern void shrink_dcache_for_umount(struct super_block *);
 222extern int d_invalidate(struct dentry *);
 223
 224/* only used at mount-time */
 225extern struct dentry * d_alloc_root(struct inode *);
 226extern struct dentry * d_make_root(struct inode *);
 227
 228/* <clickety>-<click> the ramfs-type tree */
 229extern void d_genocide(struct dentry *);
 230
 231extern struct dentry *d_find_alias(struct inode *);
 232extern void d_prune_aliases(struct inode *);
 233
 234/* test whether we have any submounts in a subdir tree */
 235extern int have_submounts(struct dentry *);
 236
 237/*
 238 * This adds the entry to the hash queues.
 239 */
 240extern void d_rehash(struct dentry *);
 241
 242/**
 243 * d_add - add dentry to hash queues
 244 * @entry: dentry to add
 245 * @inode: The inode to attach to this dentry
 246 *
 247 * This adds the entry to the hash queues and initializes @inode.
 248 * The entry was actually filled in earlier during d_alloc().
 249 */
 250 
 251static inline void d_add(struct dentry *entry, struct inode *inode)
 252{
 253        d_instantiate(entry, inode);
 254        d_rehash(entry);
 255}
 256
 257/**
 258 * d_add_unique - add dentry to hash queues without aliasing
 259 * @entry: dentry to add
 260 * @inode: The inode to attach to this dentry
 261 *
 262 * This adds the entry to the hash queues and initializes @inode.
 263 * The entry was actually filled in earlier during d_alloc().
 264 */
 265static inline struct dentry *d_add_unique(struct dentry *entry, struct inode *inode)
 266{
 267        struct dentry *res;
 268
 269        res = d_instantiate_unique(entry, inode);
 270        d_rehash(res != NULL ? res : entry);
 271        return res;
 272}
 273
 274extern void dentry_update_name_case(struct dentry *, struct qstr *);
 275
 276/* used for rename() and baskets */
 277extern void d_move(struct dentry *, struct dentry *);
 278extern struct dentry *d_ancestor(struct dentry *, struct dentry *);
 279
 280/* appendix may either be NULL or be used for transname suffixes */
 281extern struct dentry *d_lookup(struct dentry *, struct qstr *);
 282extern struct dentry *d_hash_and_lookup(struct dentry *, struct qstr *);
 283extern struct dentry *__d_lookup(struct dentry *, struct qstr *);
 284extern struct dentry *__d_lookup_rcu(const struct dentry *parent,
 285                                const struct qstr *name,
 286                                unsigned *seq, struct inode **inode);
 287
 288/**
 289 * __d_rcu_to_refcount - take a refcount on dentry if sequence check is ok
 290 * @dentry: dentry to take a ref on
 291 * @seq: seqcount to verify against
 292 * Returns: 0 on failure, else 1.
 293 *
 294 * __d_rcu_to_refcount operates on a dentry,seq pair that was returned
 295 * by __d_lookup_rcu, to get a reference on an rcu-walk dentry.
 296 */
 297static inline int __d_rcu_to_refcount(struct dentry *dentry, unsigned seq)
 298{
 299        int ret = 0;
 300
 301        assert_spin_locked(&dentry->d_lock);
 302        if (!read_seqcount_retry(&dentry->d_seq, seq)) {
 303                ret = 1;
 304                dentry->d_count++;
 305        }
 306
 307        return ret;
 308}
 309
 310/* validate "insecure" dentry pointer */
 311extern int d_validate(struct dentry *, struct dentry *);
 312
 313/*
 314 * helper function for dentry_operations.d_dname() members
 315 */
 316extern char *dynamic_dname(struct dentry *, char *, int, const char *, ...);
 317
 318extern char *__d_path(const struct path *, const struct path *, char *, int);
 319extern char *d_absolute_path(const struct path *, char *, int);
 320extern char *d_path(const struct path *, char *, int);
 321extern char *d_path_with_unreachable(const struct path *, char *, int);
 322extern char *dentry_path_raw(struct dentry *, char *, int);
 323extern char *dentry_path(struct dentry *, char *, int);
 324
 325/* Allocation counts.. */
 326
 327/**
 328 *      dget, dget_dlock -      get a reference to a dentry
 329 *      @dentry: dentry to get a reference to
 330 *
 331 *      Given a dentry or %NULL pointer increment the reference count
 332 *      if appropriate and return the dentry. A dentry will not be 
 333 *      destroyed when it has references.
 334 */
 335static inline struct dentry *dget_dlock(struct dentry *dentry)
 336{
 337        if (dentry)
 338                dentry->d_count++;
 339        return dentry;
 340}
 341
 342static inline struct dentry *dget(struct dentry *dentry)
 343{
 344        if (dentry) {
 345                spin_lock(&dentry->d_lock);
 346                dget_dlock(dentry);
 347                spin_unlock(&dentry->d_lock);
 348        }
 349        return dentry;
 350}
 351
 352extern struct dentry *dget_parent(struct dentry *dentry);
 353
 354/**
 355 *      d_unhashed -    is dentry hashed
 356 *      @dentry: entry to check
 357 *
 358 *      Returns true if the dentry passed is not currently hashed.
 359 */
 360 
 361static inline int d_unhashed(struct dentry *dentry)
 362{
 363        return hlist_bl_unhashed(&dentry->d_hash);
 364}
 365
 366static inline int d_unlinked(struct dentry *dentry)
 367{
 368        return d_unhashed(dentry) && !IS_ROOT(dentry);
 369}
 370
 371static inline int cant_mount(struct dentry *dentry)
 372{
 373        return (dentry->d_flags & DCACHE_CANT_MOUNT);
 374}
 375
 376static inline void dont_mount(struct dentry *dentry)
 377{
 378        spin_lock(&dentry->d_lock);
 379        dentry->d_flags |= DCACHE_CANT_MOUNT;
 380        spin_unlock(&dentry->d_lock);
 381}
 382
 383extern void dput(struct dentry *);
 384
 385static inline bool d_managed(struct dentry *dentry)
 386{
 387        return dentry->d_flags & DCACHE_MANAGED_DENTRY;
 388}
 389
 390static inline bool d_mountpoint(struct dentry *dentry)
 391{
 392        return dentry->d_flags & DCACHE_MOUNTED;
 393}
 394
 395static inline bool d_need_lookup(struct dentry *dentry)
 396{
 397        return dentry->d_flags & DCACHE_NEED_LOOKUP;
 398}
 399
 400extern void d_clear_need_lookup(struct dentry *dentry);
 401
 402extern int sysctl_vfs_cache_pressure;
 403
 404#endif  /* __LINUX_DCACHE_H */
 405