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 /* 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  */
  42 struct 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
  56 struct 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 };
  63 extern 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 */
  70 static inline unsigned long
  71 partial_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  */
  80 static 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. */
  86 extern 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
 103 struct 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  */
 140 enum dentry_d_lock_class
 141 {
 142         DENTRY_D_LOCK_NORMAL, /* implicitly used by plain spin_lock() APIs. */
 143         DENTRY_D_LOCK_NESTED
 144 };
 145
 146 struct dentry_operations {
 147         int (*d_revalidate)(struct dentry *, unsigned int);
 148         int (*d_hash)(const struct dentry *, const struct inode *,
 149                         struct qstr *);
 150         int (*d_compare)(const struct dentry *, const struct inode *,
 151                         const struct dentry *, const struct inode *,
 152                         unsigned int, const char *, const struct qstr *);
 153         int (*d_delete)(const struct dentry *);
 154         void (*d_release)(struct dentry *);
 155         void (*d_prune)(struct dentry *);
 156         void (*d_iput)(struct dentry *, struct inode *);
 157         char *(*d_dname)(struct dentry *, char *, int);
 158         struct vfsmount *(*d_automount)(struct path *);
 159         int (*d_manage)(struct dentry *, bool);
 160 } ____cacheline_aligned;
 161
 162 /*
 163  * Locking rules for dentry_operations callbacks are to be found in
 164  * Documentation/filesystems/Locking. Keep it updated!
 165  *
 166  * FUrther descriptions are found in Documentation/filesystems/vfs.txt.
 167  * Keep it updated too!
 168  */
 169
 170 /* d_flags entries */
 171 #define DCACHE_OP_HASH          0x0001
 172 #define DCACHE_OP_COMPARE       0x0002
 173 #define DCACHE_OP_REVALIDATE    0x0004
 174 #define DCACHE_OP_DELETE        0x0008
 175 #define DCACHE_OP_PRUNE         0x0010
 176
 177 #define DCACHE_DISCONNECTED     0x0020
 178      /* This dentry is possibly not currently connected to the dcache tree, in
 179       * which case its parent will either be itself, or will have this flag as
 180       * well.  nfsd will not use a dentry with this bit set, but will first
 181       * endeavour to clear the bit either by discovering that it is connected,
 182       * or by performing lookup operations.   Any filesystem which supports
 183       * nfsd_operations MUST have a lookup function which, if it finds a
 184       * directory inode with a DCACHE_DISCONNECTED dentry, will d_move that
 185       * dentry into place and return that dentry rather than the passed one,
 186       * typically using d_splice_alias. */
 187
 188 #define DCACHE_REFERENCED       0x0040  /* Recently used, don't discard. */
 189 #define DCACHE_RCUACCESS        0x0080  /* Entry has ever been RCU-visible */
 190
 191 #define DCACHE_CANT_MOUNT       0x0100
 192 #define DCACHE_GENOCIDE         0x0200
 193 #define DCACHE_SHRINK_LIST      0x0400
 194
 195 #define DCACHE_NFSFS_RENAMED    0x1000
 196      /* this dentry has been "silly renamed" and has to be deleted on the last
 197       * dput() */
 198 #define DCACHE_COOKIE           0x2000  /* For use by dcookie subsystem */
 199 #define DCACHE_FSNOTIFY_PARENT_WATCHED 0x4000
 200      /* Parent inode is watched by some fsnotify listener */
 201
 202 #define DCACHE_MOUNTED          0x10000 /* is a mountpoint */
 203 #define DCACHE_NEED_AUTOMOUNT   0x20000 /* handle automount on this dir */
 204 #define DCACHE_MANAGE_TRANSIT   0x40000 /* manage transit from this dirent */
 205 #define DCACHE_NEED_LOOKUP      0x80000 /* dentry requires i_op->lookup */
 206 #define DCACHE_MANAGED_DENTRY \
 207         (DCACHE_MOUNTED|DCACHE_NEED_AUTOMOUNT|DCACHE_MANAGE_TRANSIT)
 208
 209 extern seqlock_t rename_lock;
 210
 211 static inline int dname_external(struct dentry *dentry)
 212 {
 213         return dentry->d_name.name != dentry->d_iname;
 214 }
 215
 216 /*
 217  * These are the low-level FS interfaces to the dcache..
 218  */
 219 extern void d_instantiate(struct dentry *, struct inode *);
 220 extern struct dentry * d_instantiate_unique(struct dentry *, struct inode *);
 221 extern struct dentry * d_materialise_unique(struct dentry *, struct inode *);
 222 extern void __d_drop(struct dentry *dentry);
 223 extern void d_drop(struct dentry *dentry);
 224 extern void d_delete(struct dentry *);
 225 extern void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op);
 226
 227 /* allocate/de-allocate */
 228 extern struct dentry * d_alloc(struct dentry *, const struct qstr *);
 229 extern struct dentry * d_alloc_pseudo(struct super_block *, const struct qstr *);
 230 extern struct dentry * d_splice_alias(struct inode *, struct dentry *);
 231 extern struct dentry * d_add_ci(struct dentry *, struct inode *, struct qstr *);
 232 extern struct dentry *d_find_any_alias(struct inode *inode);
 233 extern struct dentry * d_obtain_alias(struct inode *);
 234 extern void shrink_dcache_sb(struct super_block *);
 235 extern void shrink_dcache_parent(struct dentry *);
 236 extern void shrink_dcache_for_umount(struct super_block *);
 237 extern int d_invalidate(struct dentry *);
 238
 239 /* only used at mount-time */
 240 extern struct dentry * d_make_root(struct inode *);
 241
 242 /* <clickety>-<click> the ramfs-type tree */
 243 extern void d_genocide(struct dentry *);
 244
 245 extern struct dentry *d_find_alias(struct inode *);
 246 extern void d_prune_aliases(struct inode *);
 247
 248 /* test whether we have any submounts in a subdir tree */
 249 extern int have_submounts(struct dentry *);
 250
 251 /*
 252  * This adds the entry to the hash queues.
 253  */
 254 extern void d_rehash(struct dentry *);
 255
 256 /**
 257  * d_add - add dentry to hash queues
 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
 265 static inline void d_add(struct dentry *entry, struct inode *inode)
 266 {
 267         d_instantiate(entry, inode);
 268         d_rehash(entry);
 269 }
 270
 271 /**
 272  * d_add_unique - add dentry to hash queues without aliasing
 273  * @entry: dentry to add
 274  * @inode: The inode to attach to this dentry
 275  *
 276  * This adds the entry to the hash queues and initializes @inode.
 277  * The entry was actually filled in earlier during d_alloc().
 278  */
 279 static inline struct dentry *d_add_unique(struct dentry *entry, struct inode *inode)
 280 {
 281         struct dentry *res;
 282
 283         res = d_instantiate_unique(entry, inode);
 284         d_rehash(res != NULL ? res : entry);
 285         return res;
 286 }
 287
 288 extern void dentry_update_name_case(struct dentry *, struct qstr *);
 289
 290 /* used for rename() and baskets */
 291 extern void d_move(struct dentry *, struct dentry *);
 292 extern struct dentry *d_ancestor(struct dentry *, struct dentry *);
 293
 294 /* appendix may either be NULL or be used for transname suffixes */
 295 extern struct dentry *d_lookup(struct dentry *, struct qstr *);
 296 extern struct dentry *d_hash_and_lookup(struct dentry *, struct qstr *);
 297 extern struct dentry *__d_lookup(struct dentry *, struct qstr *);
 298 extern struct dentry *__d_lookup_rcu(const struct dentry *parent,
 299                                 const struct qstr *name,
 300                                 unsigned *seq, struct inode *inode);
 301
 302 /**
 303  * __d_rcu_to_refcount - take a refcount on dentry if sequence check is ok
 304  * @dentry: dentry to take a ref on
 305  * @seq: seqcount to verify against
 306  * Returns: 0 on failure, else 1.
 307  *
 308  * __d_rcu_to_refcount operates on a dentry,seq pair that was returned
 309  * by __d_lookup_rcu, to get a reference on an rcu-walk dentry.
 310  */
 311 static inline int __d_rcu_to_refcount(struct dentry *dentry, unsigned seq)
 312 {
 313         int ret = 0;
 314
 315         assert_spin_locked(&dentry->d_lock);
 316         if (!read_seqcount_retry(&dentry->d_seq, seq)) {
 317                 ret = 1;
 318                 dentry->d_count++;
 319         }
 320
 321         return ret;
 322 }
 323
 324 /* validate "insecure" dentry pointer */
 325 extern int d_validate(struct dentry *, struct dentry *);
 326
 327 /*
 328  * helper function for dentry_operations.d_dname() members
 329  */
 330 extern char *dynamic_dname(struct dentry *, char *, int, const char *, ...);
 331
 332 extern char *__d_path(const struct path *, const struct path *, char *, int);
 333 extern char *d_absolute_path(const struct path *, char *, int);
 334 extern char *d_path(const struct path *, char *, int);
 335 extern char *d_path_with_unreachable(const struct path *, char *, int);
 336 extern char *dentry_path_raw(struct dentry *, char *, int);
 337 extern char *dentry_path(struct dentry *, char *, int);
 338
 339 /* Allocation counts.. */
 340
 341 /**
 342  *      dget, dget_dlock -      get a reference to a dentry
 343  *      @dentry: dentry to get a reference to
 344  *
 345  *      Given a dentry or %NULL pointer increment the reference count
 346  *      if appropriate and return the dentry. A dentry will not be
 347  *      destroyed when it has references.
 348  */
 349 static inline struct dentry *dget_dlock(struct dentry *dentry)
 350 {
 351         if (dentry)
 352                 dentry->d_count++;
 353         return dentry;
 354 }
 355
 356 static inline struct dentry *dget(struct dentry *dentry)
 357 {
 358         if (dentry) {
 359                 spin_lock(&dentry->d_lock);
 360                 dget_dlock(dentry);
 361                 spin_unlock(&dentry->d_lock);
 362         }
 363         return dentry;
 364 }
 365
 366 extern struct dentry *dget_parent(struct dentry *dentry);
 367
 368 /**
 369  *      d_unhashed -    is dentry hashed
 370  *      @dentry: entry to check
 371  *
 372  *      Returns true if the dentry passed is not currently hashed.
 373  */
 374
 375 static inline int d_unhashed(struct dentry *dentry)
 376 {
 377         return hlist_bl_unhashed(&dentry->d_hash);
 378 }
 379
 380 static inline int d_unlinked(struct dentry *dentry)
 381 {
 382         return d_unhashed(dentry) && !IS_ROOT(dentry);
 383 }
 384
 385 static inline int cant_mount(struct dentry *dentry)
 386 {
 387         return (dentry->d_flags & DCACHE_CANT_MOUNT);
 388 }
 389
 390 static inline void dont_mount(struct dentry *dentry)
 391 {
 392         spin_lock(&dentry->d_lock);
 393         dentry->d_flags |= DCACHE_CANT_MOUNT;
 394         spin_unlock(&dentry->d_lock);
 395 }
 396
 397 extern void dput(struct dentry *);
 398
 399 static inline bool d_managed(struct dentry *dentry)
 400 {
 401         return dentry->d_flags & DCACHE_MANAGED_DENTRY;
 402 }
 403
 404 static inline bool d_mountpoint(struct dentry *dentry)
 405 {
 406         return dentry->d_flags & DCACHE_MOUNTED;
 407 }
 408
 409 static inline bool d_need_lookup(struct dentry *dentry)
 410 {
 411         return dentry->d_flags & DCACHE_NEED_LOOKUP;
 412 }
 413
 414 extern void d_clear_need_lookup(struct dentry *dentry);
 415
 416 extern int sysctl_vfs_cache_pressure;
 417
 418 #endif  /* __LINUX_DCACHE_H */