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_weak_revalidate)(struct dentry *, unsigned int);
 149        int (*d_hash)(const struct dentry *, const struct inode *,
 150                        struct qstr *);
 151        int (*d_compare)(const struct dentry *, const struct inode *,
 152                        const struct dentry *, const struct inode *,
 153                        unsigned int, const char *, const struct qstr *);
 154        int (*d_delete)(const struct dentry *);
 155        void (*d_release)(struct dentry *);
 156        void (*d_prune)(struct dentry *);
 157        void (*d_iput)(struct dentry *, struct inode *);
 158        char *(*d_dname)(struct dentry *, char *, int);
 159        struct vfsmount *(*d_automount)(struct path *);
 160        int (*d_manage)(struct dentry *, bool);
 161} ____cacheline_aligned;
 162
 163/*
 164 * Locking rules for dentry_operations callbacks are to be found in
 165 * Documentation/filesystems/Locking. Keep it updated!
 166 *
 167 * FUrther descriptions are found in Documentation/filesystems/vfs.txt.
 168 * Keep it updated too!
 169 */
 170
 171/* d_flags entries */
 172#define DCACHE_OP_HASH          0x0001
 173#define DCACHE_OP_COMPARE       0x0002
 174#define DCACHE_OP_REVALIDATE    0x0004
 175#define DCACHE_OP_DELETE        0x0008
 176#define DCACHE_OP_PRUNE         0x0010
 177
 178#define DCACHE_DISCONNECTED     0x0020
 179     /* This dentry is possibly not currently connected to the dcache tree, in
 180      * which case its parent will either be itself, or will have this flag as
 181      * well.  nfsd will not use a dentry with this bit set, but will first
 182      * endeavour to clear the bit either by discovering that it is connected,
 183      * or by performing lookup operations.   Any filesystem which supports
 184      * nfsd_operations MUST have a lookup function which, if it finds a
 185      * directory inode with a DCACHE_DISCONNECTED dentry, will d_move that
 186      * dentry into place and return that dentry rather than the passed one,
 187      * typically using d_splice_alias. */
 188
 189#define DCACHE_REFERENCED       0x0040  /* Recently used, don't discard. */
 190#define DCACHE_RCUACCESS        0x0080  /* Entry has ever been RCU-visible */
 191
 192#define DCACHE_CANT_MOUNT       0x0100
 193#define DCACHE_GENOCIDE         0x0200
 194#define DCACHE_SHRINK_LIST      0x0400
 195
 196#define DCACHE_OP_WEAK_REVALIDATE       0x0800
 197
 198#define DCACHE_NFSFS_RENAMED    0x1000
 199     /* this dentry has been "silly renamed" and has to be deleted on the last
 200      * dput() */
 201#define DCACHE_COOKIE           0x2000  /* For use by dcookie subsystem */
 202#define DCACHE_FSNOTIFY_PARENT_WATCHED 0x4000
 203     /* Parent inode is watched by some fsnotify listener */
 204
 205#define DCACHE_MOUNTED          0x10000 /* is a mountpoint */
 206#define DCACHE_NEED_AUTOMOUNT   0x20000 /* handle automount on this dir */
 207#define DCACHE_MANAGE_TRANSIT   0x40000 /* manage transit from this dirent */
 208#define DCACHE_MANAGED_DENTRY \
 209        (DCACHE_MOUNTED|DCACHE_NEED_AUTOMOUNT|DCACHE_MANAGE_TRANSIT)
 210
 211#define DCACHE_DENTRY_KILLED    0x100000
 212
 213extern seqlock_t rename_lock;
 214
 215static inline int dname_external(struct dentry *dentry)
 216{
 217        return dentry->d_name.name != dentry->d_iname;
 218}
 219
 220/*
 221 * These are the low-level FS interfaces to the dcache..
 222 */
 223extern void d_instantiate(struct dentry *, struct inode *);
 224extern struct dentry * d_instantiate_unique(struct dentry *, struct inode *);
 225extern struct dentry * d_materialise_unique(struct dentry *, struct inode *);
 226extern void __d_drop(struct dentry *dentry);
 227extern void d_drop(struct dentry *dentry);
 228extern void d_delete(struct dentry *);
 229extern void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op);
 230
 231/* allocate/de-allocate */
 232extern struct dentry * d_alloc(struct dentry *, const struct qstr *);
 233extern struct dentry * d_alloc_pseudo(struct super_block *, const struct qstr *);
 234extern struct dentry * d_splice_alias(struct inode *, struct dentry *);
 235extern struct dentry * d_add_ci(struct dentry *, struct inode *, struct qstr *);
 236extern struct dentry *d_find_any_alias(struct inode *inode);
 237extern struct dentry * d_obtain_alias(struct inode *);
 238extern void shrink_dcache_sb(struct super_block *);
 239extern void shrink_dcache_parent(struct dentry *);
 240extern void shrink_dcache_for_umount(struct super_block *);
 241extern int d_invalidate(struct dentry *);
 242
 243/* only used at mount-time */
 244extern struct dentry * d_make_root(struct inode *);
 245
 246/* <clickety>-<click> the ramfs-type tree */
 247extern void d_genocide(struct dentry *);
 248
 249extern struct dentry *d_find_alias(struct inode *);
 250extern void d_prune_aliases(struct inode *);
 251
 252/* test whether we have any submounts in a subdir tree */
 253extern int have_submounts(struct dentry *);
 254
 255/*
 256 * This adds the entry to the hash queues.
 257 */
 258extern void d_rehash(struct dentry *);
 259
 260/**
 261 * d_add - add dentry to hash queues
 262 * @entry: dentry to add
 263 * @inode: The inode to attach to this dentry
 264 *
 265 * This adds the entry to the hash queues and initializes @inode.
 266 * The entry was actually filled in earlier during d_alloc().
 267 */
 268 
 269static inline void d_add(struct dentry *entry, struct inode *inode)
 270{
 271        d_instantiate(entry, inode);
 272        d_rehash(entry);
 273}
 274
 275/**
 276 * d_add_unique - add dentry to hash queues without aliasing
 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 */
 283static inline struct dentry *d_add_unique(struct dentry *entry, struct inode *inode)
 284{
 285        struct dentry *res;
 286
 287        res = d_instantiate_unique(entry, inode);
 288        d_rehash(res != NULL ? res : entry);
 289        return res;
 290}
 291
 292extern void dentry_update_name_case(struct dentry *, struct qstr *);
 293
 294/* used for rename() and baskets */
 295extern void d_move(struct dentry *, struct dentry *);
 296extern struct dentry *d_ancestor(struct dentry *, struct dentry *);
 297
 298/* appendix may either be NULL or be used for transname suffixes */
 299extern struct dentry *d_lookup(const struct dentry *, const struct qstr *);
 300extern struct dentry *d_hash_and_lookup(struct dentry *, struct qstr *);
 301extern struct dentry *__d_lookup(const struct dentry *, const struct qstr *);
 302extern struct dentry *__d_lookup_rcu(const struct dentry *parent,
 303                                const struct qstr *name,
 304                                unsigned *seq, struct inode *inode);
 305
 306/**
 307 * __d_rcu_to_refcount - take a refcount on dentry if sequence check is ok
 308 * @dentry: dentry to take a ref on
 309 * @seq: seqcount to verify against
 310 * Returns: 0 on failure, else 1.
 311 *
 312 * __d_rcu_to_refcount operates on a dentry,seq pair that was returned
 313 * by __d_lookup_rcu, to get a reference on an rcu-walk dentry.
 314 */
 315static inline int __d_rcu_to_refcount(struct dentry *dentry, unsigned seq)
 316{
 317        int ret = 0;
 318
 319        assert_spin_locked(&dentry->d_lock);
 320        if (!read_seqcount_retry(&dentry->d_seq, seq)) {
 321                ret = 1;
 322                dentry->d_count++;
 323        }
 324
 325        return ret;
 326}
 327
 328/* validate "insecure" dentry pointer */
 329extern int d_validate(struct dentry *, struct dentry *);
 330
 331/*
 332 * helper function for dentry_operations.d_dname() members
 333 */
 334extern char *dynamic_dname(struct dentry *, char *, int, const char *, ...);
 335
 336extern char *__d_path(const struct path *, const struct path *, char *, int);
 337extern char *d_absolute_path(const struct path *, char *, int);
 338extern char *d_path(const struct path *, char *, int);
 339extern char *dentry_path_raw(struct dentry *, char *, int);
 340extern char *dentry_path(struct dentry *, char *, int);
 341
 342/* Allocation counts.. */
 343
 344/**
 345 *      dget, dget_dlock -      get a reference to a dentry
 346 *      @dentry: dentry to get a reference to
 347 *
 348 *      Given a dentry or %NULL pointer increment the reference count
 349 *      if appropriate and return the dentry. A dentry will not be 
 350 *      destroyed when it has references.
 351 */
 352static inline struct dentry *dget_dlock(struct dentry *dentry)
 353{
 354        if (dentry)
 355                dentry->d_count++;
 356        return dentry;
 357}
 358
 359static inline struct dentry *dget(struct dentry *dentry)
 360{
 361        if (dentry) {
 362                spin_lock(&dentry->d_lock);
 363                dget_dlock(dentry);
 364                spin_unlock(&dentry->d_lock);
 365        }
 366        return dentry;
 367}
 368
 369extern struct dentry *dget_parent(struct dentry *dentry);
 370
 371/**
 372 *      d_unhashed -    is dentry hashed
 373 *      @dentry: entry to check
 374 *
 375 *      Returns true if the dentry passed is not currently hashed.
 376 */
 377 
 378static inline int d_unhashed(struct dentry *dentry)
 379{
 380        return hlist_bl_unhashed(&dentry->d_hash);
 381}
 382
 383static inline int d_unlinked(struct dentry *dentry)
 384{
 385        return d_unhashed(dentry) && !IS_ROOT(dentry);
 386}
 387
 388static inline int cant_mount(struct dentry *dentry)
 389{
 390        return (dentry->d_flags & DCACHE_CANT_MOUNT);
 391}
 392
 393static inline void dont_mount(struct dentry *dentry)
 394{
 395        spin_lock(&dentry->d_lock);
 396        dentry->d_flags |= DCACHE_CANT_MOUNT;
 397        spin_unlock(&dentry->d_lock);
 398}
 399
 400extern void dput(struct dentry *);
 401
 402static inline bool d_managed(struct dentry *dentry)
 403{
 404        return dentry->d_flags & DCACHE_MANAGED_DENTRY;
 405}
 406
 407static inline bool d_mountpoint(struct dentry *dentry)
 408{
 409        return dentry->d_flags & DCACHE_MOUNTED;
 410}
 411
 412extern int sysctl_vfs_cache_pressure;
 413
 414#endif  /* __LINUX_DCACHE_H */
 415
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