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
  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 /*
  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  */
  54 static 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 */
  76 static inline unsigned long
  77 partial_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  */
  86 static 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. */
  92 static inline unsigned int
  93 full_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
 116 struct 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  */
 153 enum dentry_d_lock_class
 154 {
 155         DENTRY_D_LOCK_NORMAL, /* implicitly used by plain spin_lock() APIs. */
 156         DENTRY_D_LOCK_NESTED
 157 };
 158
 159 struct 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
 219 extern seqlock_t rename_lock;
 220
 221 static 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  */
 229 extern void d_instantiate(struct dentry *, struct inode *);
 230 extern struct dentry * d_instantiate_unique(struct dentry *, struct inode *);
 231 extern struct dentry * d_materialise_unique(struct dentry *, struct inode *);
 232 extern void __d_drop(struct dentry *dentry);
 233 extern void d_drop(struct dentry *dentry);
 234 extern void d_delete(struct dentry *);
 235 extern void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op);
 236
 237 /* allocate/de-allocate */
 238 extern struct dentry * d_alloc(struct dentry *, const struct qstr *);
 239 extern struct dentry * d_alloc_pseudo(struct super_block *, const struct qstr *);
 240 extern struct dentry * d_splice_alias(struct inode *, struct dentry *);
 241 extern struct dentry * d_add_ci(struct dentry *, struct inode *, struct qstr *);
 242 extern struct dentry * d_obtain_alias(struct inode *);
 243 extern void shrink_dcache_sb(struct super_block *);
 244 extern void shrink_dcache_parent(struct dentry *);
 245 extern void shrink_dcache_for_umount(struct super_block *);
 246 extern int d_invalidate(struct dentry *);
 247
 248 /* only used at mount-time */
 249 extern struct dentry * d_alloc_root(struct inode *);
 250
 251 /* <clickety>-<click> the ramfs-type tree */
 252 extern void d_genocide(struct dentry *);
 253
 254 extern struct dentry *d_find_alias(struct inode *);
 255 extern void d_prune_aliases(struct inode *);
 256
 257 /* test whether we have any submounts in a subdir tree */
 258 extern int have_submounts(struct dentry *);
 259
 260 /*
 261  * This adds the entry to the hash queues.
 262  */
 263 extern 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
 274 static 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  */
 288 static 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
 297 extern void dentry_update_name_case(struct dentry *, struct qstr *);
 298
 299 /* used for rename() and baskets */
 300 extern void d_move(struct dentry *, struct dentry *);
 301 extern struct dentry *d_ancestor(struct dentry *, struct dentry *);
 302
 303 /* appendix may either be NULL or be used for transname suffixes */
 304 extern struct dentry *d_lookup(struct dentry *, struct qstr *);
 305 extern struct dentry *d_hash_and_lookup(struct dentry *, struct qstr *);
 306 extern struct dentry *__d_lookup(struct dentry *, struct qstr *);
 307 extern 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  */
 319 static 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 */
 333 extern int d_validate(struct dentry *, struct dentry *);
 334
 335 /*
 336  * helper function for dentry_operations.d_dname() members
 337  */
 338 extern char *dynamic_dname(struct dentry *, char *, int, const char *, ...);
 339
 340 extern char *__d_path(const struct path *path, struct path *root, char *, int);
 341 extern char *d_path(const struct path *, char *, int);
 342 extern char *d_path_with_unreachable(const struct path *, char *, int);
 343 extern char *dentry_path_raw(struct dentry *, char *, int);
 344 extern 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  */
 356 static inline struct dentry *dget_dlock(struct dentry *dentry)
 357 {
 358         if (dentry)
 359                 dentry->d_count++;
 360         return dentry;
 361 }
 362
 363 static 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
 373 extern 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
 382 static inline int d_unhashed(struct dentry *dentry)
 383 {
 384         return hlist_bl_unhashed(&dentry->d_hash);
 385 }
 386
 387 static inline int d_unlinked(struct dentry *dentry)
 388 {
 389         return d_unhashed(dentry) && !IS_ROOT(dentry);
 390 }
 391
 392 static inline int cant_mount(struct dentry *dentry)
 393 {
 394         return (dentry->d_flags & DCACHE_CANT_MOUNT);
 395 }
 396
 397 static 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
 404 extern void dput(struct dentry *);
 405
 406 static inline bool d_managed(struct dentry *dentry)
 407 {
 408         return dentry->d_flags & DCACHE_MANAGED_DENTRY;
 409 }
 410
 411 static inline bool d_mountpoint(struct dentry *dentry)
 412 {
 413         return dentry->d_flags & DCACHE_MOUNTED;
 414 }
 415
 416 static inline bool d_need_lookup(struct dentry *dentry)
 417 {
 418         return dentry->d_flags & DCACHE_NEED_LOOKUP;
 419 }
 420
 421 extern void d_clear_need_lookup(struct dentry *dentry);
 422
 423 extern int sysctl_vfs_cache_pressure;
 424
 425 #endif  /* __LINUX_DCACHE_H */