include/linux/dcache.h

   1 #ifndef __LINUX_DCACHE_H
   2 #define __LINUX_DCACHE_H
   3
   4 #ifdef __KERNEL__
   5
   6 #include <asm/atomic.h>
   7 #include <linux/list.h>
   8 #include <linux/spinlock.h>
   9 #include <linux/cache.h>
  10 #include <linux/rcupdate.h>
  11
  12 struct nameidata;
  13 struct path;
  14 struct vfsmount;
  15
  16 /*
  17  * linux/include/linux/dcache.h
  18  *
  19  * Dirent cache data structures
  20  *
  21  * (C) Copyright 1997 Thomas Schoebel-Theuer,
  22  * with heavy changes by Linus Torvalds
  23  */
  24
  25 #define IS_ROOT(x) ((x) == (x)->d_parent)
  26
  27 /*
  28  * "quick string" -- eases parameter passing, but more importantly
  29  * saves "metadata" about the string (ie length and the hash).
  30  *
  31  * hash comes first so it snuggles against d_parent in the
  32  * dentry.
  33  */
  34 struct qstr {
  35         unsigned int hash;
  36         unsigned int len;
  37         const unsigned char *name;
  38 };
  39
  40 struct dentry_stat_t {
  41         int nr_dentry;
  42         int nr_unused;
  43         int age_limit;          /* age in seconds */
  44         int want_pages;         /* pages requested by system */
  45         int dummy[2];
  46 };
  47 extern struct dentry_stat_t dentry_stat;
  48
  49 /* Name hashing routines. Initial hash value */
  50 /* Hash courtesy of the R5 hash in reiserfs modulo sign bits */
  51 #define init_name_hash()                0
  52
  53 /* partial hash update function. Assume roughly 4 bits per character */
  54 static inline unsigned long
  55 partial_name_hash(unsigned long c, unsigned long prevhash)
  56 {
  57         return (prevhash + (c << 4) + (c >> 4)) * 11;
  58 }
  59
  60 /*
  61  * Finally: cut down the number of bits to a int value (and try to avoid
  62  * losing bits)
  63  */
  64 static inline unsigned long end_name_hash(unsigned long hash)
  65 {
  66         return (unsigned int) hash;
  67 }
  68
  69 /* Compute the hash for a name string. */
  70 static inline unsigned int
  71 full_name_hash(const unsigned char *name, unsigned int len)
  72 {
  73         unsigned long hash = init_name_hash();
  74         while (len--)
  75                 hash = partial_name_hash(*name++, hash);
  76         return end_name_hash(hash);
  77 }
  78
  79 struct dcookie_struct;
  80
  81 #define DNAME_INLINE_LEN_MIN 36
  82
  83 struct dentry {
  84         atomic_t d_count;
  85         unsigned int d_flags;           /* protected by d_lock */
  86         spinlock_t d_lock;              /* per dentry lock */
  87         struct inode *d_inode;          /* Where the name belongs to - NULL is
  88                                          * negative */
  89         /*
  90          * The next three fields are touched by __d_lookup.  Place them here
  91          * so they all fit in a cache line.
  92          */
  93         struct hlist_node d_hash;       /* lookup hash list */
  94         struct dentry *d_parent;        /* parent directory */
  95         struct qstr d_name;
  96
  97         struct list_head d_lru;         /* LRU list */
  98         /*
  99          * d_child and d_rcu can share memory
 100          */
 101         union {
 102                 struct list_head d_child;       /* child of parent list */
 103                 struct rcu_head d_rcu;
 104         } d_u;
 105         struct list_head d_subdirs;     /* our children */
 106         struct list_head d_alias;       /* inode alias list */
 107         unsigned long d_time;           /* used by d_revalidate */
 108         struct dentry_operations *d_op;
 109         struct super_block *d_sb;       /* The root of the dentry tree */
 110         void *d_fsdata;                 /* fs-specific data */
 111 #ifdef CONFIG_PROFILING
 112         struct dcookie_struct *d_cookie; /* cookie, if any */
 113 #endif
 114         int d_mounted;
 115         unsigned char d_iname[DNAME_INLINE_LEN_MIN];    /* small names */
 116 };
 117
 118 /*
 119  * dentry->d_lock spinlock nesting subclasses:
 120  *
 121  * 0: normal
 122  * 1: nested
 123  */
 124 enum dentry_d_lock_class
 125 {
 126         DENTRY_D_LOCK_NORMAL, /* implicitly used by plain spin_lock() APIs. */
 127         DENTRY_D_LOCK_NESTED
 128 };
 129
 130 struct dentry_operations {
 131         int (*d_revalidate)(struct dentry *, struct nameidata *);
 132         int (*d_hash) (struct dentry *, struct qstr *);
 133         int (*d_compare) (struct dentry *, struct qstr *, struct qstr *);
 134         int (*d_delete)(struct dentry *);
 135         void (*d_release)(struct dentry *);
 136         void (*d_iput)(struct dentry *, struct inode *);
 137         char *(*d_dname)(struct dentry *, char *, int);
 138 };
 139
 140 /* the dentry parameter passed to d_hash and d_compare is the parent
 141  * directory of the entries to be compared. It is used in case these
 142  * functions need any directory specific information for determining
 143  * equivalency classes.  Using the dentry itself might not work, as it
 144  * might be a negative dentry which has no information associated with
 145  * it */
 146
 147 /*
 148 locking rules:
 149                 big lock        dcache_lock     d_lock   may block
 150 d_revalidate:   no              no              no       yes
 151 d_hash          no              no              no       yes
 152 d_compare:      no              yes             yes      no
 153 d_delete:       no              yes             no       no
 154 d_release:      no              no              no       yes
 155 d_iput:         no              no              no       yes
 156  */
 157
 158 /* d_flags entries */
 159 #define DCACHE_AUTOFS_PENDING 0x0001    /* autofs: "under construction" */
 160 #define DCACHE_NFSFS_RENAMED  0x0002    /* this dentry has been "silly
 161                                          * renamed" and has to be
 162                                          * deleted on the last dput()
 163                                          */
 164 #define DCACHE_DISCONNECTED 0x0004
 165      /* This dentry is possibly not currently connected to the dcache tree,
 166       * in which case its parent will either be itself, or will have this
 167       * flag as well.  nfsd will not use a dentry with this bit set, but will
 168       * first endeavour to clear the bit either by discovering that it is
 169       * connected, or by performing lookup operations.   Any filesystem which
 170       * supports nfsd_operations MUST have a lookup function which, if it finds
 171       * a directory inode with a DCACHE_DISCONNECTED dentry, will d_move
 172       * that dentry into place and return that dentry rather than the passed one,
 173       * typically using d_splice_alias.
 174       */
 175
 176 #define DCACHE_REFERENCED       0x0008  /* Recently used, don't discard. */
 177 #define DCACHE_UNHASHED         0x0010
 178
 179 #define DCACHE_INOTIFY_PARENT_WATCHED   0x0020 /* Parent inode is watched */
 180
 181 extern spinlock_t dcache_lock;
 182 extern seqlock_t rename_lock;
 183
 184 /**
 185  * d_drop - drop a dentry
 186  * @dentry: dentry to drop
 187  *
 188  * d_drop() unhashes the entry from the parent dentry hashes, so that it won't
 189  * be found through a VFS lookup any more. Note that this is different from
 190  * deleting the dentry - d_delete will try to mark the dentry negative if
 191  * possible, giving a successful _negative_ lookup, while d_drop will
 192  * just make the cache lookup fail.
 193  *
 194  * d_drop() is used mainly for stuff that wants to invalidate a dentry for some
 195  * reason (NFS timeouts or autofs deletes).
 196  *
 197  * __d_drop requires dentry->d_lock.
 198  */
 199
 200 static inline void __d_drop(struct dentry *dentry)
 201 {
 202         if (!(dentry->d_flags & DCACHE_UNHASHED)) {
 203                 dentry->d_flags |= DCACHE_UNHASHED;
 204                 hlist_del_rcu(&dentry->d_hash);
 205         }
 206 }
 207
 208 static inline void d_drop(struct dentry *dentry)
 209 {
 210         spin_lock(&dcache_lock);
 211         spin_lock(&dentry->d_lock);
 212         __d_drop(dentry);
 213         spin_unlock(&dentry->d_lock);
 214         spin_unlock(&dcache_lock);
 215 }
 216
 217 static inline int dname_external(struct dentry *dentry)
 218 {
 219         return dentry->d_name.name != dentry->d_iname;
 220 }
 221
 222 /*
 223  * These are the low-level FS interfaces to the dcache..
 224  */
 225 extern void d_instantiate(struct dentry *, struct inode *);
 226 extern struct dentry * d_instantiate_unique(struct dentry *, struct inode *);
 227 extern struct dentry * d_materialise_unique(struct dentry *, struct inode *);
 228 extern void d_delete(struct dentry *);
 229
 230 /* allocate/de-allocate */
 231 extern struct dentry * d_alloc(struct dentry *, const struct qstr *);
 232 extern struct dentry * d_alloc_anon(struct inode *);
 233 extern struct dentry * d_splice_alias(struct inode *, struct dentry *);
 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_alloc_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 /* used for rename() and baskets */
 289 extern void d_move(struct dentry *, struct dentry *);
 290
 291 /* appendix may either be NULL or be used for transname suffixes */
 292 extern struct dentry * d_lookup(struct dentry *, struct qstr *);
 293 extern struct dentry * __d_lookup(struct dentry *, struct qstr *);
 294 extern struct dentry * d_hash_and_lookup(struct dentry *, struct qstr *);
 295
 296 /* validate "insecure" dentry pointer */
 297 extern int d_validate(struct dentry *, struct dentry *);
 298
 299 /*
 300  * helper function for dentry_operations.d_dname() members
 301  */
 302 extern char *dynamic_dname(struct dentry *, char *, int, const char *, ...);
 303
 304 extern char *d_path(struct path *, char *, int);
 305
 306 /* Allocation counts.. */
 307
 308 /**
 309  *      dget, dget_locked       -       get a reference to a dentry
 310  *      @dentry: dentry to get a reference to
 311  *
 312  *      Given a dentry or %NULL pointer increment the reference count
 313  *      if appropriate and return the dentry. A dentry will not be
 314  *      destroyed when it has references. dget() should never be
 315  *      called for dentries with zero reference counter. For these cases
 316  *      (preferably none, functions in dcache.c are sufficient for normal
 317  *      needs and they take necessary precautions) you should hold dcache_lock
 318  *      and call dget_locked() instead of dget().
 319  */
 320
 321 static inline struct dentry *dget(struct dentry *dentry)
 322 {
 323         if (dentry) {
 324                 BUG_ON(!atomic_read(&dentry->d_count));
 325                 atomic_inc(&dentry->d_count);
 326         }
 327         return dentry;
 328 }
 329
 330 extern struct dentry * dget_locked(struct dentry *);
 331
 332 /**
 333  *      d_unhashed -    is dentry hashed
 334  *      @dentry: entry to check
 335  *
 336  *      Returns true if the dentry passed is not currently hashed.
 337  */
 338
 339 static inline int d_unhashed(struct dentry *dentry)
 340 {
 341         return (dentry->d_flags & DCACHE_UNHASHED);
 342 }
 343
 344 static inline struct dentry *dget_parent(struct dentry *dentry)
 345 {
 346         struct dentry *ret;
 347
 348         spin_lock(&dentry->d_lock);
 349         ret = dget(dentry->d_parent);
 350         spin_unlock(&dentry->d_lock);
 351         return ret;
 352 }
 353
 354 extern void dput(struct dentry *);
 355
 356 static inline int d_mountpoint(struct dentry *dentry)
 357 {
 358         return dentry->d_mounted;
 359 }
 360
 361 extern struct vfsmount *lookup_mnt(struct vfsmount *, struct dentry *);
 362 extern struct vfsmount *__lookup_mnt(struct vfsmount *, struct dentry *, int);
 363 extern struct dentry *lookup_create(struct nameidata *nd, int is_dir);
 364
 365 extern int sysctl_vfs_cache_pressure;
 366
 367 #endif /* __KERNEL__ */
 368
 369 #endif  /* __LINUX_DCACHE_H */