include/linux/dcache.h

   1 #ifndef __LINUX_DCACHE_H
   2 #define __LINUX_DCACHE_H
   3
   4 #include <asm/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
  13 struct nameidata;
  14 struct path;
  15 struct 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  */
  35 struct qstr {
  36         unsigned int hash;
  37         unsigned int len;
  38         const unsigned char *name;
  39 };
  40
  41 struct 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 };
  48 extern 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 */
  55 static inline unsigned long
  56 partial_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  */
  65 static 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. */
  71 static inline unsigned int
  72 full_name_hash(const unsigned char *name, unsigned int len)
  73 {
  74         unsigned long hash = init_name_hash();
  75         while (len--)
  76                 hash = partial_name_hash(*name++, hash);
  77         return end_name_hash(hash);
  78 }
  79
  80 /*
  81  * Try to keep struct dentry aligned on 64 byte cachelines (this will
  82  * give reasonable cacheline footprint with larger lines without the
  83  * large memory footprint increase).
  84  */
  85 #ifdef CONFIG_64BIT
  86 # define DNAME_INLINE_LEN 32 /* 192 bytes */
  87 #else
  88 # ifdef CONFIG_SMP
  89 #  define DNAME_INLINE_LEN 36 /* 128 bytes */
  90 # else
  91 #  define DNAME_INLINE_LEN 40 /* 128 bytes */
  92 # endif
  93 #endif
  94
  95 struct dentry {
  96         /* RCU lookup touched fields */
  97         unsigned int d_flags;           /* protected by d_lock */
  98         seqcount_t d_seq;               /* per dentry seqlock */
  99         struct hlist_bl_node d_hash;    /* lookup hash list */
 100         struct dentry *d_parent;        /* parent directory */
 101         struct qstr d_name;
 102         struct inode *d_inode;          /* Where the name belongs to - NULL is
 103                                          * negative */
 104         unsigned char d_iname[DNAME_INLINE_LEN];        /* small names */
 105
 106         /* Ref lookup also touches following */
 107         unsigned int d_count;           /* protected by d_lock */
 108         spinlock_t d_lock;              /* per dentry lock */
 109         const struct dentry_operations *d_op;
 110         struct super_block *d_sb;       /* The root of the dentry tree */
 111         unsigned long d_time;           /* used by d_revalidate */
 112         void *d_fsdata;                 /* fs-specific data */
 113
 114         struct list_head d_lru;         /* LRU list */
 115         /*
 116          * d_child and d_rcu can share memory
 117          */
 118         union {
 119                 struct list_head d_child;       /* child of parent list */
 120                 struct rcu_head d_rcu;
 121         } d_u;
 122         struct list_head d_subdirs;     /* our children */
 123         struct list_head d_alias;       /* inode alias list */
 124 };
 125
 126 /*
 127  * dentry->d_lock spinlock nesting subclasses:
 128  *
 129  * 0: normal
 130  * 1: nested
 131  */
 132 enum dentry_d_lock_class
 133 {
 134         DENTRY_D_LOCK_NORMAL, /* implicitly used by plain spin_lock() APIs. */
 135         DENTRY_D_LOCK_NESTED
 136 };
 137
 138 struct dentry_operations {
 139         int (*d_revalidate)(struct dentry *, struct nameidata *);
 140         int (*d_hash)(const struct dentry *, const struct inode *,
 141                         struct qstr *);
 142         int (*d_compare)(const struct dentry *, const struct inode *,
 143                         const struct dentry *, const struct inode *,
 144                         unsigned int, const char *, const struct qstr *);
 145         int (*d_delete)(const struct dentry *);
 146         void (*d_release)(struct dentry *);
 147         void (*d_iput)(struct dentry *, struct inode *);
 148         char *(*d_dname)(struct dentry *, char *, int);
 149 } ____cacheline_aligned;
 150
 151 /*
 152  * Locking rules for dentry_operations callbacks are to be found in
 153  * Documentation/filesystems/Locking. Keep it updated!
 154  *
 155  * FUrther descriptions are found in Documentation/filesystems/vfs.txt.
 156  * Keep it updated too!
 157  */
 158
 159 /* d_flags entries */
 160 #define DCACHE_AUTOFS_PENDING 0x0001    /* autofs: "under construction" */
 161 #define DCACHE_NFSFS_RENAMED  0x0002
 162      /* this dentry has been "silly renamed" and has to be deleted on the last
 163       * dput() */
 164
 165 #define DCACHE_DISCONNECTED     0x0004
 166      /* This dentry is possibly not currently connected to the dcache tree, in
 167       * which case its parent will either be itself, or will have this flag as
 168       * well.  nfsd will not use a dentry with this bit set, but will first
 169       * endeavour to clear the bit either by discovering that it is connected,
 170       * or by performing lookup operations.   Any filesystem which supports
 171       * nfsd_operations MUST have a lookup function which, if it finds a
 172       * directory inode with a DCACHE_DISCONNECTED dentry, will d_move that
 173       * dentry into place and return that dentry rather than the passed one,
 174       * typically using d_splice_alias. */
 175
 176 #define DCACHE_REFERENCED       0x0008  /* Recently used, don't discard. */
 177 #define DCACHE_UNHASHED         0x0010
 178 #define DCACHE_INOTIFY_PARENT_WATCHED 0x0020
 179      /* Parent inode is watched by inotify */
 180
 181 #define DCACHE_COOKIE           0x0040  /* For use by dcookie subsystem */
 182 #define DCACHE_FSNOTIFY_PARENT_WATCHED 0x0080
 183      /* Parent inode is watched by some fsnotify listener */
 184
 185 #define DCACHE_CANT_MOUNT       0x0100
 186 #define DCACHE_GENOCIDE         0x0200
 187 #define DCACHE_MOUNTED          0x0400  /* is a mountpoint */
 188
 189 #define DCACHE_OP_HASH          0x1000
 190 #define DCACHE_OP_COMPARE       0x2000
 191 #define DCACHE_OP_REVALIDATE    0x4000
 192 #define DCACHE_OP_DELETE        0x8000
 193
 194 extern seqlock_t rename_lock;
 195
 196 static 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  */
 204 extern void d_instantiate(struct dentry *, struct inode *);
 205 extern struct dentry * d_instantiate_unique(struct dentry *, struct inode *);
 206 extern struct dentry * d_materialise_unique(struct dentry *, struct inode *);
 207 extern void __d_drop(struct dentry *dentry);
 208 extern void d_drop(struct dentry *dentry);
 209 extern void d_delete(struct dentry *);
 210 extern void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op);
 211
 212 /* allocate/de-allocate */
 213 extern struct dentry * d_alloc(struct dentry *, const struct qstr *);
 214 extern struct dentry * d_alloc_pseudo(struct super_block *, const struct qstr *);
 215 extern struct dentry * d_splice_alias(struct inode *, struct dentry *);
 216 extern struct dentry * d_add_ci(struct dentry *, struct inode *, struct qstr *);
 217 extern struct dentry * d_obtain_alias(struct inode *);
 218 extern void shrink_dcache_sb(struct super_block *);
 219 extern void shrink_dcache_parent(struct dentry *);
 220 extern void shrink_dcache_for_umount(struct super_block *);
 221 extern int d_invalidate(struct dentry *);
 222
 223 /* only used at mount-time */
 224 extern struct dentry * d_alloc_root(struct inode *);
 225
 226 /* <clickety>-<click> the ramfs-type tree */
 227 extern void d_genocide(struct dentry *);
 228
 229 extern struct dentry *d_find_alias(struct inode *);
 230 extern void d_prune_aliases(struct inode *);
 231
 232 /* test whether we have any submounts in a subdir tree */
 233 extern int have_submounts(struct dentry *);
 234
 235 /*
 236  * This adds the entry to the hash queues.
 237  */
 238 extern void d_rehash(struct dentry *);
 239
 240 /**
 241  * d_add - add dentry to hash queues
 242  * @entry: dentry to add
 243  * @inode: The inode to attach to this dentry
 244  *
 245  * This adds the entry to the hash queues and initializes @inode.
 246  * The entry was actually filled in earlier during d_alloc().
 247  */
 248
 249 static inline void d_add(struct dentry *entry, struct inode *inode)
 250 {
 251         d_instantiate(entry, inode);
 252         d_rehash(entry);
 253 }
 254
 255 /**
 256  * d_add_unique - add dentry to hash queues without aliasing
 257  * @entry: dentry to add
 258  * @inode: The inode to attach to this dentry
 259  *
 260  * This adds the entry to the hash queues and initializes @inode.
 261  * The entry was actually filled in earlier during d_alloc().
 262  */
 263 static inline struct dentry *d_add_unique(struct dentry *entry, struct inode *inode)
 264 {
 265         struct dentry *res;
 266
 267         res = d_instantiate_unique(entry, inode);
 268         d_rehash(res != NULL ? res : entry);
 269         return res;
 270 }
 271
 272 extern void dentry_update_name_case(struct dentry *, struct qstr *);
 273
 274 /* used for rename() and baskets */
 275 extern void d_move(struct dentry *, struct dentry *);
 276 extern struct dentry *d_ancestor(struct dentry *, struct dentry *);
 277
 278 /* appendix may either be NULL or be used for transname suffixes */
 279 extern struct dentry *d_lookup(struct dentry *, struct qstr *);
 280 extern struct dentry *d_hash_and_lookup(struct dentry *, struct qstr *);
 281 extern struct dentry *__d_lookup(struct dentry *, struct qstr *);
 282 extern struct dentry *__d_lookup_rcu(struct dentry *parent, struct qstr *name,
 283                                 unsigned *seq, struct inode **inode);
 284
 285 /**
 286  * __d_rcu_to_refcount - take a refcount on dentry if sequence check is ok
 287  * @dentry: dentry to take a ref on
 288  * @seq: seqcount to verify against
 289  * @Returns: 0 on failure, else 1.
 290  *
 291  * __d_rcu_to_refcount operates on a dentry,seq pair that was returned
 292  * by __d_lookup_rcu, to get a reference on an rcu-walk dentry.
 293  */
 294 static inline int __d_rcu_to_refcount(struct dentry *dentry, unsigned seq)
 295 {
 296         int ret = 0;
 297
 298         assert_spin_locked(&dentry->d_lock);
 299         if (!read_seqcount_retry(&dentry->d_seq, seq)) {
 300                 ret = 1;
 301                 dentry->d_count++;
 302         }
 303
 304         return ret;
 305 }
 306
 307 /* validate "insecure" dentry pointer */
 308 extern int d_validate(struct dentry *, struct dentry *);
 309
 310 /*
 311  * helper function for dentry_operations.d_dname() members
 312  */
 313 extern char *dynamic_dname(struct dentry *, char *, int, const char *, ...);
 314
 315 extern char *__d_path(const struct path *path, struct path *root, char *, int);
 316 extern char *d_path(const struct path *, char *, int);
 317 extern char *d_path_with_unreachable(const struct path *, char *, int);
 318 extern char *dentry_path_raw(struct dentry *, char *, int);
 319 extern char *dentry_path(struct dentry *, char *, int);
 320
 321 /* Allocation counts.. */
 322
 323 /**
 324  *      dget, dget_dlock -      get a reference to a dentry
 325  *      @dentry: dentry to get a reference to
 326  *
 327  *      Given a dentry or %NULL pointer increment the reference count
 328  *      if appropriate and return the dentry. A dentry will not be
 329  *      destroyed when it has references.
 330  */
 331 static inline struct dentry *dget_dlock(struct dentry *dentry)
 332 {
 333         if (dentry)
 334                 dentry->d_count++;
 335         return dentry;
 336 }
 337
 338 static inline struct dentry *dget(struct dentry *dentry)
 339 {
 340         if (dentry) {
 341                 spin_lock(&dentry->d_lock);
 342                 dget_dlock(dentry);
 343                 spin_unlock(&dentry->d_lock);
 344         }
 345         return dentry;
 346 }
 347
 348 extern struct dentry *dget_parent(struct dentry *dentry);
 349
 350 /**
 351  *      d_unhashed -    is dentry hashed
 352  *      @dentry: entry to check
 353  *
 354  *      Returns true if the dentry passed is not currently hashed.
 355  */
 356
 357 static inline int d_unhashed(struct dentry *dentry)
 358 {
 359         return (dentry->d_flags & DCACHE_UNHASHED);
 360 }
 361
 362 static inline int d_unlinked(struct dentry *dentry)
 363 {
 364         return d_unhashed(dentry) && !IS_ROOT(dentry);
 365 }
 366
 367 static inline int cant_mount(struct dentry *dentry)
 368 {
 369         return (dentry->d_flags & DCACHE_CANT_MOUNT);
 370 }
 371
 372 static inline void dont_mount(struct dentry *dentry)
 373 {
 374         spin_lock(&dentry->d_lock);
 375         dentry->d_flags |= DCACHE_CANT_MOUNT;
 376         spin_unlock(&dentry->d_lock);
 377 }
 378
 379 extern void dput(struct dentry *);
 380
 381 static inline int d_mountpoint(struct dentry *dentry)
 382 {
 383         return dentry->d_flags & DCACHE_MOUNTED;
 384 }
 385
 386 extern struct vfsmount *lookup_mnt(struct path *);
 387 extern struct dentry *lookup_create(struct nameidata *nd, int is_dir);
 388
 389 extern int sysctl_vfs_cache_pressure;
 390
 391 #endif  /* __LINUX_DCACHE_H */