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
  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/* The hash is always the low bits of hash_len */
  29#ifdef __LITTLE_ENDIAN
  30 #define HASH_LEN_DECLARE u32 hash; u32 len;
  31#else
  32 #define HASH_LEN_DECLARE u32 len; u32 hash;
  33#endif
  34
  35/*
  36 * "quick string" -- eases parameter passing, but more importantly
  37 * saves "metadata" about the string (ie length and the hash).
  38 *
  39 * hash comes first so it snuggles against d_parent in the
  40 * dentry.
  41 */
  42struct qstr {
  43        union {
  44                struct {
  45                        HASH_LEN_DECLARE;
  46                };
  47                u64 hash_len;
  48        };
  49        const unsigned char *name;
  50};
  51
  52#define QSTR_INIT(n,l) { { { .len = l } }, .name = n }
  53#define hashlen_hash(hashlen) ((u32) (hashlen))
  54#define hashlen_len(hashlen)  ((u32)((hashlen) >> 32))
  55
  56struct dentry_stat_t {
  57        int nr_dentry;
  58        int nr_unused;
  59        int age_limit;          /* age in seconds */
  60        int want_pages;         /* pages requested by system */
  61        int dummy[2];
  62};
  63extern struct dentry_stat_t dentry_stat;
  64
  65/* Name hashing routines. Initial hash value */
  66/* Hash courtesy of the R5 hash in reiserfs modulo sign bits */
  67#define init_name_hash()                0
  68
  69/* partial hash update function. Assume roughly 4 bits per character */
  70static inline unsigned long
  71partial_name_hash(unsigned long c, unsigned long prevhash)
  72{
  73        return (prevhash + (c << 4) + (c >> 4)) * 11;
  74}
  75
  76/*
  77 * Finally: cut down the number of bits to a int value (and try to avoid
  78 * losing bits)
  79 */
  80static inline unsigned long end_name_hash(unsigned long hash)
  81{
  82        return (unsigned int) hash;
  83}
  84
  85/* Compute the hash for a name string. */
  86extern unsigned int full_name_hash(const unsigned char *, unsigned int);
  87
  88/*
  89 * Try to keep struct dentry aligned on 64 byte cachelines (this will
  90 * give reasonable cacheline footprint with larger lines without the
  91 * large memory footprint increase).
  92 */
  93#ifdef CONFIG_64BIT
  94# define DNAME_INLINE_LEN 32 /* 192 bytes */
  95#else
  96# ifdef CONFIG_SMP
  97#  define DNAME_INLINE_LEN 36 /* 128 bytes */
  98# else
  99#  define DNAME_INLINE_LEN 40 /* 128 bytes */
 100# endif
 101#endif
 102
 103struct dentry {
 104        /* RCU lookup touched fields */
 105        unsigned int d_flags;           /* protected by d_lock */
 106        seqcount_t d_seq;               /* per dentry seqlock */
 107        struct hlist_bl_node d_hash;    /* lookup hash list */
 108        struct dentry *d_parent;        /* parent directory */
 109        struct qstr d_name;
 110        struct inode *d_inode;          /* Where the name belongs to - NULL is
 111                                         * negative */
 112        unsigned char d_iname[DNAME_INLINE_LEN];        /* small names */
 113
 114        /* Ref lookup also touches following */
 115        unsigned int d_count;           /* protected by d_lock */
 116        spinlock_t d_lock;              /* per dentry lock */
 117        const struct dentry_operations *d_op;
 118        struct super_block *d_sb;       /* The root of the dentry tree */
 119        unsigned long d_time;           /* used by d_revalidate */
 120        void *d_fsdata;                 /* fs-specific data */
 121
 122        struct list_head d_lru;         /* LRU list */
 123        /*
 124         * d_child and d_rcu can share memory
 125         */
 126        union {
 127                struct list_head d_child;       /* child of parent list */
 128                struct rcu_head d_rcu;
 129        } d_u;
 130        struct list_head d_subdirs;     /* our children */
 131        struct hlist_node d_alias;      /* inode alias list */
 132};
 133
 134/*
 135 * dentry->d_lock spinlock nesting subclasses:
 136 *
 137 * 0: normal
 138 * 1: nested
 139 */
 140enum dentry_d_lock_class
 141{
 142        DENTRY_D_LOCK_NORMAL, /* implicitly used by plain spin_lock() APIs. */
 143        DENTRY_D_LOCK_NESTED
 144};
 145
 146struct dentry_operations {
 147        int (*d_revalidate)(struct dentry *, unsigned int);
 148        int (*d_hash)(const struct dentry *, const struct inode *,
 149                        struct qstr *);
 150        int (*d_compare)(const struct dentry *, const struct inode *,
 151                        const struct dentry *, const struct inode *,
 152                        unsigned int, const char *, const struct qstr *);
 153        int (*d_delete)(const struct dentry *);
 154        void (*d_release)(struct dentry *);
 155        void (*d_prune)(struct dentry *);
 156        void (*d_iput)(struct dentry *, struct inode *);
 157        char *(*d_dname)(struct dentry *, char *, int);
 158        struct vfsmount *(*d_automount)(struct path *);
 159        int (*d_manage)(struct dentry *, bool);
 160} ____cacheline_aligned;
 161
 162/*
 163 * Locking rules for dentry_operations callbacks are to be found in
 164 * Documentation/filesystems/Locking. Keep it updated!
 165 *
 166 * FUrther descriptions are found in Documentation/filesystems/vfs.txt.
 167 * Keep it updated too!
 168 */
 169
 170/* d_flags entries */
 171#define DCACHE_OP_HASH          0x0001
 172#define DCACHE_OP_COMPARE       0x0002
 173#define DCACHE_OP_REVALIDATE    0x0004
 174#define DCACHE_OP_DELETE        0x0008
 175#define DCACHE_OP_PRUNE         0x0010
 176
 177#define DCACHE_DISCONNECTED     0x0020
 178     /* This dentry is possibly not currently connected to the dcache tree, in
 179      * which case its parent will either be itself, or will have this flag as
 180      * well.  nfsd will not use a dentry with this bit set, but will first
 181      * endeavour to clear the bit either by discovering that it is connected,
 182      * or by performing lookup operations.   Any filesystem which supports
 183      * nfsd_operations MUST have a lookup function which, if it finds a
 184      * directory inode with a DCACHE_DISCONNECTED dentry, will d_move that
 185      * dentry into place and return that dentry rather than the passed one,
 186      * typically using d_splice_alias. */
 187
 188#define DCACHE_REFERENCED       0x0040  /* Recently used, don't discard. */
 189#define DCACHE_RCUACCESS        0x0080  /* Entry has ever been RCU-visible */
 190
 191#define DCACHE_CANT_MOUNT       0x0100
 192#define DCACHE_GENOCIDE         0x0200
 193#define DCACHE_SHRINK_LIST      0x0400
 194
 195#define DCACHE_NFSFS_RENAMED    0x1000
 196     /* this dentry has been "silly renamed" and has to be deleted on the last
 197      * dput() */
 198#define DCACHE_COOKIE           0x2000  /* For use by dcookie subsystem */
 199#define DCACHE_FSNOTIFY_PARENT_WATCHED 0x4000
 200     /* Parent inode is watched by some fsnotify listener */
 201
 202#define DCACHE_MOUNTED          0x10000 /* is a mountpoint */
 203#define DCACHE_NEED_AUTOMOUNT   0x20000 /* handle automount on this dir */
 204#define DCACHE_MANAGE_TRANSIT   0x40000 /* manage transit from this dirent */
 205#define DCACHE_NEED_LOOKUP      0x80000 /* dentry requires i_op->lookup */
 206#define DCACHE_MANAGED_DENTRY \
 207        (DCACHE_MOUNTED|DCACHE_NEED_AUTOMOUNT|DCACHE_MANAGE_TRANSIT)
 208
 209#define DCACHE_DENTRY_KILLED    0x100000
 210
 211extern seqlock_t rename_lock;
 212
 213static inline int dname_external(struct dentry *dentry)
 214{
 215        return dentry->d_name.name != dentry->d_iname;
 216}
 217
 218/*
 219 * These are the low-level FS interfaces to the dcache..
 220 */
 221extern void d_instantiate(struct dentry *, struct inode *);
 222extern struct dentry * d_instantiate_unique(struct dentry *, struct inode *);
 223extern struct dentry * d_materialise_unique(struct dentry *, struct inode *);
 224extern void __d_drop(struct dentry *dentry);
 225extern void d_drop(struct dentry *dentry);
 226extern void d_delete(struct dentry *);
 227extern void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op);
 228
 229/* allocate/de-allocate */
 230extern struct dentry * d_alloc(struct dentry *, const struct qstr *);
 231extern struct dentry * d_alloc_pseudo(struct super_block *, const struct qstr *);
 232extern struct dentry * d_splice_alias(struct inode *, struct dentry *);
 233extern struct dentry * d_add_ci(struct dentry *, struct inode *, struct qstr *);
 234extern struct dentry *d_find_any_alias(struct inode *inode);
 235extern struct dentry * d_obtain_alias(struct inode *);
 236extern void shrink_dcache_sb(struct super_block *);
 237extern void shrink_dcache_parent(struct dentry *);
 238extern void shrink_dcache_for_umount(struct super_block *);
 239extern int d_invalidate(struct dentry *);
 240
 241/* only used at mount-time */
 242extern struct dentry * d_make_root(struct inode *);
 243
 244/* <clickety>-<click> the ramfs-type tree */
 245extern void d_genocide(struct dentry *);
 246
 247extern struct dentry *d_find_alias(struct inode *);
 248extern void d_prune_aliases(struct inode *);
 249
 250/* test whether we have any submounts in a subdir tree */
 251extern int have_submounts(struct dentry *);
 252
 253/*
 254 * This adds the entry to the hash queues.
 255 */
 256extern void d_rehash(struct dentry *);
 257
 258/**
 259 * d_add - add dentry to hash queues
 260 * @entry: dentry to add
 261 * @inode: The inode to attach to this dentry
 262 *
 263 * This adds the entry to the hash queues and initializes @inode.
 264 * The entry was actually filled in earlier during d_alloc().
 265 */
 266 
 267static inline void d_add(struct dentry *entry, struct inode *inode)
 268{
 269        d_instantiate(entry, inode);
 270        d_rehash(entry);
 271}
 272
 273/**
 274 * d_add_unique - add dentry to hash queues without aliasing
 275 * @entry: dentry to add
 276 * @inode: The inode to attach to this dentry
 277 *
 278 * This adds the entry to the hash queues and initializes @inode.
 279 * The entry was actually filled in earlier during d_alloc().
 280 */
 281static inline struct dentry *d_add_unique(struct dentry *entry, struct inode *inode)
 282{
 283        struct dentry *res;
 284
 285        res = d_instantiate_unique(entry, inode);
 286        d_rehash(res != NULL ? res : entry);
 287        return res;
 288}
 289
 290extern void dentry_update_name_case(struct dentry *, struct qstr *);
 291
 292/* used for rename() and baskets */
 293extern void d_move(struct dentry *, struct dentry *);
 294extern struct dentry *d_ancestor(struct dentry *, struct dentry *);
 295
 296/* appendix may either be NULL or be used for transname suffixes */
 297extern struct dentry *d_lookup(struct dentry *, struct qstr *);
 298extern struct dentry *d_hash_and_lookup(struct dentry *, struct qstr *);
 299extern struct dentry *__d_lookup(struct dentry *, struct qstr *);
 300extern struct dentry *__d_lookup_rcu(const struct dentry *parent,
 301                                const struct qstr *name,
 302                                unsigned *seq, struct inode *inode);
 303
 304/**
 305 * __d_rcu_to_refcount - take a refcount on dentry if sequence check is ok
 306 * @dentry: dentry to take a ref on
 307 * @seq: seqcount to verify against
 308 * Returns: 0 on failure, else 1.
 309 *
 310 * __d_rcu_to_refcount operates on a dentry,seq pair that was returned
 311 * by __d_lookup_rcu, to get a reference on an rcu-walk dentry.
 312 */
 313static inline int __d_rcu_to_refcount(struct dentry *dentry, unsigned seq)
 314{
 315        int ret = 0;
 316
 317        assert_spin_locked(&dentry->d_lock);
 318        if (!read_seqcount_retry(&dentry->d_seq, seq)) {
 319                ret = 1;
 320                dentry->d_count++;
 321        }
 322
 323        return ret;
 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 *, ...);
 333
 334extern char *__d_path(const struct path *, const struct path *, char *, int);
 335extern char *d_absolute_path(const struct path *, char *, int);
 336extern char *d_path(const struct path *, char *, int);
 337extern char *d_path_with_unreachable(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_count++;
 355        return dentry;
 356}
 357
 358static inline struct dentry *dget(struct dentry *dentry)
 359{
 360        if (dentry) {
 361                spin_lock(&dentry->d_lock);
 362                dget_dlock(dentry);
 363                spin_unlock(&dentry->d_lock);
 364        }
 365        return dentry;
 366}
 367
 368extern struct dentry *dget_parent(struct dentry *dentry);
 369
 370/**
 371 *      d_unhashed -    is dentry hashed
 372 *      @dentry: entry to check
 373 *
 374 *      Returns true if the dentry passed is not currently hashed.
 375 */
 376 
 377static inline int d_unhashed(struct dentry *dentry)
 378{
 379        return hlist_bl_unhashed(&dentry->d_hash);
 380}
 381
 382static inline int d_unlinked(struct dentry *dentry)
 383{
 384        return d_unhashed(dentry) && !IS_ROOT(dentry);
 385}
 386
 387static inline int cant_mount(struct dentry *dentry)
 388{
 389        return (dentry->d_flags & DCACHE_CANT_MOUNT);
 390}
 391
 392static inline void dont_mount(struct dentry *dentry)
 393{
 394        spin_lock(&dentry->d_lock);
 395        dentry->d_flags |= DCACHE_CANT_MOUNT;
 396        spin_unlock(&dentry->d_lock);
 397}
 398
 399extern void dput(struct dentry *);
 400
 401static inline bool d_managed(struct dentry *dentry)
 402{
 403        return dentry->d_flags & DCACHE_MANAGED_DENTRY;
 404}
 405
 406static inline bool d_mountpoint(struct dentry *dentry)
 407{
 408        return dentry->d_flags & DCACHE_MOUNTED;
 409}
 410
 411static inline bool d_need_lookup(struct dentry *dentry)
 412{
 413        return dentry->d_flags & DCACHE_NEED_LOOKUP;
 414}
 415
 416extern void d_clear_need_lookup(struct dentry *dentry);
 417
 418extern int sysctl_vfs_cache_pressure;
 419
 420#endif  /* __LINUX_DCACHE_H */
 421
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