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 #include <linux/lockref.h>
  13
  14 struct nameidata;
  15 struct path;
  16 struct vfsmount;
  17
  18 /*
  19  * linux/include/linux/dcache.h
  20  *
  21  * Dirent cache data structures
  22  *
  23  * (C) Copyright 1997 Thomas Schoebel-Theuer,
  24  * with heavy changes by Linus Torvalds
  25  */
  26
  27 #define IS_ROOT(x) ((x) == (x)->d_parent)
  28
  29 /* The hash is always the low bits of hash_len */
  30 #ifdef __LITTLE_ENDIAN
  31  #define HASH_LEN_DECLARE u32 hash; u32 len;
  32 #else
  33  #define HASH_LEN_DECLARE u32 len; u32 hash;
  34 #endif
  35
  36 /*
  37  * "quick string" -- eases parameter passing, but more importantly
  38  * saves "metadata" about the string (ie length and the hash).
  39  *
  40  * hash comes first so it snuggles against d_parent in the
  41  * dentry.
  42  */
  43 struct qstr {
  44         union {
  45                 struct {
  46                         HASH_LEN_DECLARE;
  47                 };
  48                 u64 hash_len;
  49         };
  50         const unsigned char *name;
  51 };
  52
  53 #define QSTR_INIT(n,l) { { { .len = l } }, .name = n }
  54 #define hashlen_hash(hashlen) ((u32) (hashlen))
  55 #define hashlen_len(hashlen)  ((u32)((hashlen) >> 32))
  56
  57 struct dentry_stat_t {
  58         int nr_dentry;
  59         int nr_unused;
  60         int age_limit;          /* age in seconds */
  61         int want_pages;         /* pages requested by system */
  62         int dummy[2];
  63 };
  64 extern struct dentry_stat_t dentry_stat;
  65
  66 /* Name hashing routines. Initial hash value */
  67 /* Hash courtesy of the R5 hash in reiserfs modulo sign bits */
  68 #define init_name_hash()                0
  69
  70 /* partial hash update function. Assume roughly 4 bits per character */
  71 static inline unsigned long
  72 partial_name_hash(unsigned long c, unsigned long prevhash)
  73 {
  74         return (prevhash + (c << 4) + (c >> 4)) * 11;
  75 }
  76
  77 /*
  78  * Finally: cut down the number of bits to a int value (and try to avoid
  79  * losing bits)
  80  */
  81 static inline unsigned long end_name_hash(unsigned long hash)
  82 {
  83         return (unsigned int) hash;
  84 }
  85
  86 /* Compute the hash for a name string. */
  87 extern unsigned int full_name_hash(const unsigned char *, unsigned int);
  88
  89 /*
  90  * Try to keep struct dentry aligned on 64 byte cachelines (this will
  91  * give reasonable cacheline footprint with larger lines without the
  92  * large memory footprint increase).
  93  */
  94 #ifdef CONFIG_64BIT
  95 # define DNAME_INLINE_LEN 32 /* 192 bytes */
  96 #else
  97 # ifdef CONFIG_SMP
  98 #  define DNAME_INLINE_LEN 36 /* 128 bytes */
  99 # else
 100 #  define DNAME_INLINE_LEN 40 /* 128 bytes */
 101 # endif
 102 #endif
 103
 104 #define d_lock  d_lockref.lock
 105
 106 struct dentry {
 107         /* RCU lookup touched fields */
 108         unsigned int d_flags;           /* protected by d_lock */
 109         seqcount_t d_seq;               /* per dentry seqlock */
 110         struct hlist_bl_node d_hash;    /* lookup hash list */
 111         struct dentry *d_parent;        /* parent directory */
 112         struct qstr d_name;
 113         struct inode *d_inode;          /* Where the name belongs to - NULL is
 114                                          * negative */
 115         unsigned char d_iname[DNAME_INLINE_LEN];        /* small names */
 116
 117         /* Ref lookup also touches following */
 118         struct lockref d_lockref;       /* per-dentry lock and refcount */
 119         const struct dentry_operations *d_op;
 120         struct super_block *d_sb;       /* The root of the dentry tree */
 121         unsigned long d_time;           /* used by d_revalidate */
 122         void *d_fsdata;                 /* fs-specific data */
 123
 124         struct list_head d_lru;         /* LRU list */
 125         /*
 126          * d_child and d_rcu can share memory
 127          */
 128         union {
 129                 struct list_head d_child;       /* child of parent list */
 130                 struct rcu_head d_rcu;
 131         } d_u;
 132         struct list_head d_subdirs;     /* our children */
 133         struct hlist_node d_alias;      /* inode alias list */
 134 };
 135
 136 /*
 137  * dentry->d_lock spinlock nesting subclasses:
 138  *
 139  * 0: normal
 140  * 1: nested
 141  */
 142 enum dentry_d_lock_class
 143 {
 144         DENTRY_D_LOCK_NORMAL, /* implicitly used by plain spin_lock() APIs. */
 145         DENTRY_D_LOCK_NESTED
 146 };
 147
 148 struct dentry_operations {
 149         int (*d_revalidate)(struct dentry *, unsigned int);
 150         int (*d_weak_revalidate)(struct dentry *, unsigned int);
 151         int (*d_hash)(const struct dentry *, struct qstr *);
 152         int (*d_compare)(const struct dentry *, const struct dentry *,
 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
 213 extern seqlock_t rename_lock;
 214
 215 static 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  */
 223 extern void d_instantiate(struct dentry *, struct inode *);
 224 extern struct dentry * d_instantiate_unique(struct dentry *, struct inode *);
 225 extern struct dentry * d_materialise_unique(struct dentry *, struct inode *);
 226 extern void __d_drop(struct dentry *dentry);
 227 extern void d_drop(struct dentry *dentry);
 228 extern void d_delete(struct dentry *);
 229 extern void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op);
 230
 231 /* allocate/de-allocate */
 232 extern struct dentry * d_alloc(struct dentry *, const struct qstr *);
 233 extern struct dentry * d_alloc_pseudo(struct super_block *, const struct qstr *);
 234 extern struct dentry * d_splice_alias(struct inode *, struct dentry *);
 235 extern struct dentry * d_add_ci(struct dentry *, struct inode *, struct qstr *);
 236 extern struct dentry *d_find_any_alias(struct inode *inode);
 237 extern struct dentry * d_obtain_alias(struct inode *);
 238 extern void shrink_dcache_sb(struct super_block *);
 239 extern void shrink_dcache_parent(struct dentry *);
 240 extern void shrink_dcache_for_umount(struct super_block *);
 241 extern int d_invalidate(struct dentry *);
 242
 243 /* only used at mount-time */
 244 extern struct dentry * d_make_root(struct inode *);
 245
 246 /* <clickety>-<click> the ramfs-type tree */
 247 extern void d_genocide(struct dentry *);
 248
 249 extern void d_tmpfile(struct dentry *, struct inode *);
 250
 251 extern struct dentry *d_find_alias(struct inode *);
 252 extern void d_prune_aliases(struct inode *);
 253
 254 /* test whether we have any submounts in a subdir tree */
 255 extern int have_submounts(struct dentry *);
 256
 257 /*
 258  * This adds the entry to the hash queues.
 259  */
 260 extern void d_rehash(struct dentry *);
 261
 262 /**
 263  * d_add - add dentry to hash queues
 264  * @entry: dentry to add
 265  * @inode: The inode to attach to this dentry
 266  *
 267  * This adds the entry to the hash queues and initializes @inode.
 268  * The entry was actually filled in earlier during d_alloc().
 269  */
 270
 271 static inline void d_add(struct dentry *entry, struct inode *inode)
 272 {
 273         d_instantiate(entry, inode);
 274         d_rehash(entry);
 275 }
 276
 277 /**
 278  * d_add_unique - add dentry to hash queues without aliasing
 279  * @entry: dentry to add
 280  * @inode: The inode to attach to this dentry
 281  *
 282  * This adds the entry to the hash queues and initializes @inode.
 283  * The entry was actually filled in earlier during d_alloc().
 284  */
 285 static inline struct dentry *d_add_unique(struct dentry *entry, struct inode *inode)
 286 {
 287         struct dentry *res;
 288
 289         res = d_instantiate_unique(entry, inode);
 290         d_rehash(res != NULL ? res : entry);
 291         return res;
 292 }
 293
 294 extern void dentry_update_name_case(struct dentry *, struct qstr *);
 295
 296 /* used for rename() and baskets */
 297 extern void d_move(struct dentry *, struct dentry *);
 298 extern struct dentry *d_ancestor(struct dentry *, struct dentry *);
 299
 300 /* appendix may either be NULL or be used for transname suffixes */
 301 extern struct dentry *d_lookup(const struct dentry *, const struct qstr *);
 302 extern struct dentry *d_hash_and_lookup(struct dentry *, struct qstr *);
 303 extern struct dentry *__d_lookup(const struct dentry *, const struct qstr *);
 304 extern struct dentry *__d_lookup_rcu(const struct dentry *parent,
 305                                 const struct qstr *name, unsigned *seq);
 306
 307 static inline unsigned d_count(const struct dentry *dentry)
 308 {
 309         return dentry->d_lockref.count;
 310 }
 311
 312 /* validate "insecure" dentry pointer */
 313 extern int d_validate(struct dentry *, struct dentry *);
 314
 315 /*
 316  * helper function for dentry_operations.d_dname() members
 317  */
 318 extern char *dynamic_dname(struct dentry *, char *, int, const char *, ...);
 319 extern char *simple_dname(struct dentry *, char *, int);
 320
 321 extern char *__d_path(const struct path *, const struct path *, char *, int);
 322 extern char *d_absolute_path(const struct path *, char *, int);
 323 extern char *d_path(const struct path *, char *, int);
 324 extern char *dentry_path_raw(struct dentry *, char *, int);
 325 extern char *dentry_path(struct dentry *, char *, int);
 326
 327 /* Allocation counts.. */
 328
 329 /**
 330  *      dget, dget_dlock -      get a reference to a dentry
 331  *      @dentry: dentry to get a reference to
 332  *
 333  *      Given a dentry or %NULL pointer increment the reference count
 334  *      if appropriate and return the dentry. A dentry will not be
 335  *      destroyed when it has references.
 336  */
 337 static inline struct dentry *dget_dlock(struct dentry *dentry)
 338 {
 339         if (dentry)
 340                 dentry->d_lockref.count++;
 341         return dentry;
 342 }
 343
 344 static inline struct dentry *dget(struct dentry *dentry)
 345 {
 346         if (dentry)
 347                 lockref_get(&dentry->d_lockref);
 348         return dentry;
 349 }
 350
 351 extern struct dentry *dget_parent(struct dentry *dentry);
 352
 353 /**
 354  *      d_unhashed -    is dentry hashed
 355  *      @dentry: entry to check
 356  *
 357  *      Returns true if the dentry passed is not currently hashed.
 358  */
 359
 360 static inline int d_unhashed(struct dentry *dentry)
 361 {
 362         return hlist_bl_unhashed(&dentry->d_hash);
 363 }
 364
 365 static inline int d_unlinked(struct dentry *dentry)
 366 {
 367         return d_unhashed(dentry) && !IS_ROOT(dentry);
 368 }
 369
 370 static inline int cant_mount(struct dentry *dentry)
 371 {
 372         return (dentry->d_flags & DCACHE_CANT_MOUNT);
 373 }
 374
 375 static inline void dont_mount(struct dentry *dentry)
 376 {
 377         spin_lock(&dentry->d_lock);
 378         dentry->d_flags |= DCACHE_CANT_MOUNT;
 379         spin_unlock(&dentry->d_lock);
 380 }
 381
 382 extern void dput(struct dentry *);
 383
 384 static inline bool d_managed(struct dentry *dentry)
 385 {
 386         return dentry->d_flags & DCACHE_MANAGED_DENTRY;
 387 }
 388
 389 static inline bool d_mountpoint(struct dentry *dentry)
 390 {
 391         return dentry->d_flags & DCACHE_MOUNTED;
 392 }
 393
 394 extern int sysctl_vfs_cache_pressure;
 395
 396 #endif  /* __LINUX_DCACHE_H */