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 /* 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 extern unsigned int full_name_hash(const unsigned char *, unsigned int);
  72
  73 /*
  74  * Try to keep struct dentry aligned on 64 byte cachelines (this will
  75  * give reasonable cacheline footprint with larger lines without the
  76  * large memory footprint increase).
  77  */
  78 #ifdef CONFIG_64BIT
  79 # define DNAME_INLINE_LEN 32 /* 192 bytes */
  80 #else
  81 # ifdef CONFIG_SMP
  82 #  define DNAME_INLINE_LEN 36 /* 128 bytes */
  83 # else
  84 #  define DNAME_INLINE_LEN 40 /* 128 bytes */
  85 # endif
  86 #endif
  87
  88 struct dentry {
  89         /* RCU lookup touched fields */
  90         unsigned int d_flags;           /* protected by d_lock */
  91         seqcount_t d_seq;               /* per dentry seqlock */
  92         struct hlist_bl_node d_hash;    /* lookup hash list */
  93         struct dentry *d_parent;        /* parent directory */
  94         struct qstr d_name;
  95         struct inode *d_inode;          /* Where the name belongs to - NULL is
  96                                          * negative */
  97         unsigned char d_iname[DNAME_INLINE_LEN];        /* small names */
  98
  99         /* Ref lookup also touches following */
 100         unsigned int d_count;           /* protected by d_lock */
 101         spinlock_t d_lock;              /* per dentry lock */
 102         const struct dentry_operations *d_op;
 103         struct super_block *d_sb;       /* The root of the dentry tree */
 104         unsigned long d_time;           /* used by d_revalidate */
 105         void *d_fsdata;                 /* fs-specific data */
 106
 107         struct list_head d_lru;         /* LRU list */
 108         /*
 109          * d_child and d_rcu can share memory
 110          */
 111         union {
 112                 struct list_head d_child;       /* child of parent list */
 113                 struct rcu_head d_rcu;
 114         } d_u;
 115         struct list_head d_subdirs;     /* our children */
 116         struct list_head d_alias;       /* inode alias list */
 117 };
 118
 119 /*
 120  * dentry->d_lock spinlock nesting subclasses:
 121  *
 122  * 0: normal
 123  * 1: nested
 124  */
 125 enum dentry_d_lock_class
 126 {
 127         DENTRY_D_LOCK_NORMAL, /* implicitly used by plain spin_lock() APIs. */
 128         DENTRY_D_LOCK_NESTED
 129 };
 130
 131 struct dentry_operations {
 132         int (*d_revalidate)(struct dentry *, struct nameidata *);
 133         int (*d_hash)(const struct dentry *, const struct inode *,
 134                         struct qstr *);
 135         int (*d_compare)(const struct dentry *, const struct inode *,
 136                         const struct dentry *, const struct inode *,
 137                         unsigned int, const char *, const struct qstr *);
 138         int (*d_delete)(const struct dentry *);
 139         void (*d_release)(struct dentry *);
 140         void (*d_prune)(struct dentry *);
 141         void (*d_iput)(struct dentry *, struct inode *);
 142         char *(*d_dname)(struct dentry *, char *, int);
 143         struct vfsmount *(*d_automount)(struct path *);
 144         int (*d_manage)(struct dentry *, bool);
 145 } ____cacheline_aligned;
 146
 147 /*
 148  * Locking rules for dentry_operations callbacks are to be found in
 149  * Documentation/filesystems/Locking. Keep it updated!
 150  *
 151  * FUrther descriptions are found in Documentation/filesystems/vfs.txt.
 152  * Keep it updated too!
 153  */
 154
 155 /* d_flags entries */
 156 #define DCACHE_OP_HASH          0x0001
 157 #define DCACHE_OP_COMPARE       0x0002
 158 #define DCACHE_OP_REVALIDATE    0x0004
 159 #define DCACHE_OP_DELETE        0x0008
 160 #define DCACHE_OP_PRUNE         0x0010
 161
 162 #define DCACHE_DISCONNECTED     0x0020
 163      /* This dentry is possibly not currently connected to the dcache tree, in
 164       * which case its parent will either be itself, or will have this flag as
 165       * well.  nfsd will not use a dentry with this bit set, but will first
 166       * endeavour to clear the bit either by discovering that it is connected,
 167       * or by performing lookup operations.   Any filesystem which supports
 168       * nfsd_operations MUST have a lookup function which, if it finds a
 169       * directory inode with a DCACHE_DISCONNECTED dentry, will d_move that
 170       * dentry into place and return that dentry rather than the passed one,
 171       * typically using d_splice_alias. */
 172
 173 #define DCACHE_REFERENCED       0x0040  /* Recently used, don't discard. */
 174 #define DCACHE_RCUACCESS        0x0080  /* Entry has ever been RCU-visible */
 175
 176 #define DCACHE_CANT_MOUNT       0x0100
 177 #define DCACHE_GENOCIDE         0x0200
 178 #define DCACHE_SHRINK_LIST      0x0400
 179
 180 #define DCACHE_NFSFS_RENAMED    0x1000
 181      /* this dentry has been "silly renamed" and has to be deleted on the last
 182       * dput() */
 183 #define DCACHE_COOKIE           0x2000  /* For use by dcookie subsystem */
 184 #define DCACHE_FSNOTIFY_PARENT_WATCHED 0x4000
 185      /* Parent inode is watched by some fsnotify listener */
 186
 187 #define DCACHE_MOUNTED          0x10000 /* is a mountpoint */
 188 #define DCACHE_NEED_AUTOMOUNT   0x20000 /* handle automount on this dir */
 189 #define DCACHE_MANAGE_TRANSIT   0x40000 /* manage transit from this dirent */
 190 #define DCACHE_NEED_LOOKUP      0x80000 /* dentry requires i_op->lookup */
 191 #define DCACHE_MANAGED_DENTRY \
 192         (DCACHE_MOUNTED|DCACHE_NEED_AUTOMOUNT|DCACHE_MANAGE_TRANSIT)
 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_find_any_alias(struct inode *inode);
 218 extern struct dentry * d_obtain_alias(struct inode *);
 219 extern void shrink_dcache_sb(struct super_block *);
 220 extern void shrink_dcache_parent(struct dentry *);
 221 extern void shrink_dcache_for_umount(struct super_block *);
 222 extern int d_invalidate(struct dentry *);
 223
 224 /* only used at mount-time */
 225 extern struct dentry * d_make_root(struct inode *);
 226
 227 /* <clickety>-<click> the ramfs-type tree */
 228 extern void d_genocide(struct dentry *);
 229
 230 extern struct dentry *d_find_alias(struct inode *);
 231 extern void d_prune_aliases(struct inode *);
 232
 233 /* test whether we have any submounts in a subdir tree */
 234 extern int have_submounts(struct dentry *);
 235
 236 /*
 237  * This adds the entry to the hash queues.
 238  */
 239 extern void d_rehash(struct dentry *);
 240
 241 /**
 242  * d_add - add dentry to hash queues
 243  * @entry: dentry to add
 244  * @inode: The inode to attach to this dentry
 245  *
 246  * This adds the entry to the hash queues and initializes @inode.
 247  * The entry was actually filled in earlier during d_alloc().
 248  */
 249
 250 static inline void d_add(struct dentry *entry, struct inode *inode)
 251 {
 252         d_instantiate(entry, inode);
 253         d_rehash(entry);
 254 }
 255
 256 /**
 257  * d_add_unique - add dentry to hash queues without aliasing
 258  * @entry: dentry to add
 259  * @inode: The inode to attach to this dentry
 260  *
 261  * This adds the entry to the hash queues and initializes @inode.
 262  * The entry was actually filled in earlier during d_alloc().
 263  */
 264 static inline struct dentry *d_add_unique(struct dentry *entry, struct inode *inode)
 265 {
 266         struct dentry *res;
 267
 268         res = d_instantiate_unique(entry, inode);
 269         d_rehash(res != NULL ? res : entry);
 270         return res;
 271 }
 272
 273 extern void dentry_update_name_case(struct dentry *, struct qstr *);
 274
 275 /* used for rename() and baskets */
 276 extern void d_move(struct dentry *, struct dentry *);
 277 extern struct dentry *d_ancestor(struct dentry *, struct dentry *);
 278
 279 /* appendix may either be NULL or be used for transname suffixes */
 280 extern struct dentry *d_lookup(struct dentry *, struct qstr *);
 281 extern struct dentry *d_hash_and_lookup(struct dentry *, struct qstr *);
 282 extern struct dentry *__d_lookup(struct dentry *, struct qstr *);
 283 extern struct dentry *__d_lookup_rcu(const struct dentry *parent,
 284                                 const struct qstr *name,
 285                                 unsigned *seq, struct inode **inode);
 286
 287 /**
 288  * __d_rcu_to_refcount - take a refcount on dentry if sequence check is ok
 289  * @dentry: dentry to take a ref on
 290  * @seq: seqcount to verify against
 291  * Returns: 0 on failure, else 1.
 292  *
 293  * __d_rcu_to_refcount operates on a dentry,seq pair that was returned
 294  * by __d_lookup_rcu, to get a reference on an rcu-walk dentry.
 295  */
 296 static inline int __d_rcu_to_refcount(struct dentry *dentry, unsigned seq)
 297 {
 298         int ret = 0;
 299
 300         assert_spin_locked(&dentry->d_lock);
 301         if (!read_seqcount_retry(&dentry->d_seq, seq)) {
 302                 ret = 1;
 303                 dentry->d_count++;
 304         }
 305
 306         return ret;
 307 }
 308
 309 /* validate "insecure" dentry pointer */
 310 extern int d_validate(struct dentry *, struct dentry *);
 311
 312 /*
 313  * helper function for dentry_operations.d_dname() members
 314  */
 315 extern char *dynamic_dname(struct dentry *, char *, int, const char *, ...);
 316
 317 extern char *__d_path(const struct path *, const struct path *, char *, int);
 318 extern char *d_absolute_path(const struct path *, char *, int);
 319 extern char *d_path(const struct path *, char *, int);
 320 extern char *d_path_with_unreachable(const struct path *, char *, int);
 321 extern char *dentry_path_raw(struct dentry *, char *, int);
 322 extern char *dentry_path(struct dentry *, char *, int);
 323
 324 /* Allocation counts.. */
 325
 326 /**
 327  *      dget, dget_dlock -      get a reference to a dentry
 328  *      @dentry: dentry to get a reference to
 329  *
 330  *      Given a dentry or %NULL pointer increment the reference count
 331  *      if appropriate and return the dentry. A dentry will not be
 332  *      destroyed when it has references.
 333  */
 334 static inline struct dentry *dget_dlock(struct dentry *dentry)
 335 {
 336         if (dentry)
 337                 dentry->d_count++;
 338         return dentry;
 339 }
 340
 341 static inline struct dentry *dget(struct dentry *dentry)
 342 {
 343         if (dentry) {
 344                 spin_lock(&dentry->d_lock);
 345                 dget_dlock(dentry);
 346                 spin_unlock(&dentry->d_lock);
 347         }
 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 static inline bool d_need_lookup(struct dentry *dentry)
 395 {
 396         return dentry->d_flags & DCACHE_NEED_LOOKUP;
 397 }
 398
 399 extern void d_clear_need_lookup(struct dentry *dentry);
 400
 401 extern int sysctl_vfs_cache_pressure;
 402
 403 #endif  /* __LINUX_DCACHE_H */