include/linux/dcache.h

   1 #ifndef __LINUX_DCACHE_H
   2 #define __LINUX_DCACHE_H
   3
   4 #include <asm/atomic.h>
   5 #include <linux/list.h>
   6 #include <linux/rculist.h>
   7 #include <linux/spinlock.h>
   8 #include <linux/cache.h>
   9 #include <linux/rcupdate.h>
  10
  11 struct nameidata;
  12 struct path;
  13 struct vfsmount;
  14
  15 /*
  16  * linux/include/linux/dcache.h
  17  *
  18  * Dirent cache data structures
  19  *
  20  * (C) Copyright 1997 Thomas Schoebel-Theuer,
  21  * with heavy changes by Linus Torvalds
  22  */
  23
  24 #define IS_ROOT(x) ((x) == (x)->d_parent)
  25
  26 /*
  27  * "quick string" -- eases parameter passing, but more importantly
  28  * saves "metadata" about the string (ie length and the hash).
  29  *
  30  * hash comes first so it snuggles against d_parent in the
  31  * dentry.
  32  */
  33 struct qstr {
  34         unsigned int hash;
  35         unsigned int len;
  36         const unsigned char *name;
  37 };
  38
  39 struct dentry_stat_t {
  40         int nr_dentry;
  41         int nr_unused;
  42         int age_limit;          /* age in seconds */
  43         int want_pages;         /* pages requested by system */
  44         int dummy[2];
  45 };
  46 extern struct dentry_stat_t dentry_stat;
  47
  48 /* Name hashing routines. Initial hash value */
  49 /* Hash courtesy of the R5 hash in reiserfs modulo sign bits */
  50 #define init_name_hash()                0
  51
  52 /* partial hash update function. Assume roughly 4 bits per character */
  53 static inline unsigned long
  54 partial_name_hash(unsigned long c, unsigned long prevhash)
  55 {
  56         return (prevhash + (c << 4) + (c >> 4)) * 11;
  57 }
  58
  59 /*
  60  * Finally: cut down the number of bits to a int value (and try to avoid
  61  * losing bits)
  62  */
  63 static inline unsigned long end_name_hash(unsigned long hash)
  64 {
  65         return (unsigned int) hash;
  66 }
  67
  68 /* Compute the hash for a name string. */
  69 static inline unsigned int
  70 full_name_hash(const unsigned char *name, unsigned int len)
  71 {
  72         unsigned long hash = init_name_hash();
  73         while (len--)
  74                 hash = partial_name_hash(*name++, hash);
  75         return end_name_hash(hash);
  76 }
  77
  78 struct dcookie_struct;
  79
  80 #define DNAME_INLINE_LEN_MIN 36
  81
  82 struct dentry {
  83         atomic_t d_count;
  84         unsigned int d_flags;           /* protected by d_lock */
  85         spinlock_t d_lock;              /* per dentry lock */
  86         struct inode *d_inode;          /* Where the name belongs to - NULL is
  87                                          * negative */
  88         /*
  89          * The next three fields are touched by __d_lookup.  Place them here
  90          * so they all fit in a cache line.
  91          */
  92         struct hlist_node d_hash;       /* lookup hash list */
  93         struct dentry *d_parent;        /* parent directory */
  94         struct qstr d_name;
  95
  96         struct list_head d_lru;         /* LRU list */
  97         /*
  98          * d_child and d_rcu can share memory
  99          */
 100         union {
 101                 struct list_head d_child;       /* child of parent list */
 102                 struct rcu_head d_rcu;
 103         } d_u;
 104         struct list_head d_subdirs;     /* our children */
 105         struct list_head d_alias;       /* inode alias list */
 106         unsigned long d_time;           /* used by d_revalidate */
 107         struct dentry_operations *d_op;
 108         struct super_block *d_sb;       /* The root of the dentry tree */
 109         void *d_fsdata;                 /* fs-specific data */
 110 #ifdef CONFIG_PROFILING
 111         struct dcookie_struct *d_cookie; /* cookie, if any */
 112 #endif
 113         int d_mounted;
 114         unsigned char d_iname[DNAME_INLINE_LEN_MIN];    /* small names */
 115 };
 116
 117 /*
 118  * dentry->d_lock spinlock nesting subclasses:
 119  *
 120  * 0: normal
 121  * 1: nested
 122  */
 123 enum dentry_d_lock_class
 124 {
 125         DENTRY_D_LOCK_NORMAL, /* implicitly used by plain spin_lock() APIs. */
 126         DENTRY_D_LOCK_NESTED
 127 };
 128
 129 struct dentry_operations {
 130         int (*d_revalidate)(struct dentry *, struct nameidata *);
 131         int (*d_hash) (struct dentry *, struct qstr *);
 132         int (*d_compare) (struct dentry *, struct qstr *, struct qstr *);
 133         int (*d_delete)(struct dentry *);
 134         void (*d_release)(struct dentry *);
 135         void (*d_iput)(struct dentry *, struct inode *);
 136         char *(*d_dname)(struct dentry *, char *, int);
 137 };
 138
 139 /* the dentry parameter passed to d_hash and d_compare is the parent
 140  * directory of the entries to be compared. It is used in case these
 141  * functions need any directory specific information for determining
 142  * equivalency classes.  Using the dentry itself might not work, as it
 143  * might be a negative dentry which has no information associated with
 144  * it */
 145
 146 /*
 147 locking rules:
 148                 big lock        dcache_lock     d_lock   may block
 149 d_revalidate:   no              no              no       yes
 150 d_hash          no              no              no       yes
 151 d_compare:      no              yes             yes      no
 152 d_delete:       no              yes             no       no
 153 d_release:      no              no              no       yes
 154 d_iput:         no              no              no       yes
 155  */
 156
 157 /* d_flags entries */
 158 #define DCACHE_AUTOFS_PENDING 0x0001    /* autofs: "under construction" */
 159 #define DCACHE_NFSFS_RENAMED  0x0002    /* this dentry has been "silly
 160                                          * renamed" and has to be
 161                                          * deleted on the last dput()
 162                                          */
 163 #define DCACHE_DISCONNECTED 0x0004
 164      /* This dentry is possibly not currently connected to the dcache tree,
 165       * in which case its parent will either be itself, or will have this
 166       * flag as well.  nfsd will not use a dentry with this bit set, but will
 167       * first endeavour to clear the bit either by discovering that it is
 168       * connected, or by performing lookup operations.   Any filesystem which
 169       * supports nfsd_operations MUST have a lookup function which, if it finds
 170       * a directory inode with a DCACHE_DISCONNECTED dentry, will d_move
 171       * that dentry into place and return that dentry rather than the passed one,
 172       * typically using d_splice_alias.
 173       */
 174
 175 #define DCACHE_REFERENCED       0x0008  /* Recently used, don't discard. */
 176 #define DCACHE_UNHASHED         0x0010
 177
 178 #define DCACHE_INOTIFY_PARENT_WATCHED   0x0020 /* Parent inode is watched */
 179
 180 extern spinlock_t dcache_lock;
 181 extern seqlock_t rename_lock;
 182
 183 /**
 184  * d_drop - drop a dentry
 185  * @dentry: dentry to drop
 186  *
 187  * d_drop() unhashes the entry from the parent dentry hashes, so that it won't
 188  * be found through a VFS lookup any more. Note that this is different from
 189  * deleting the dentry - d_delete will try to mark the dentry negative if
 190  * possible, giving a successful _negative_ lookup, while d_drop will
 191  * just make the cache lookup fail.
 192  *
 193  * d_drop() is used mainly for stuff that wants to invalidate a dentry for some
 194  * reason (NFS timeouts or autofs deletes).
 195  *
 196  * __d_drop requires dentry->d_lock.
 197  */
 198
 199 static inline void __d_drop(struct dentry *dentry)
 200 {
 201         if (!(dentry->d_flags & DCACHE_UNHASHED)) {
 202                 dentry->d_flags |= DCACHE_UNHASHED;
 203                 hlist_del_rcu(&dentry->d_hash);
 204         }
 205 }
 206
 207 static inline void d_drop(struct dentry *dentry)
 208 {
 209         spin_lock(&dcache_lock);
 210         spin_lock(&dentry->d_lock);
 211         __d_drop(dentry);
 212         spin_unlock(&dentry->d_lock);
 213         spin_unlock(&dcache_lock);
 214 }
 215
 216 static inline int dname_external(struct dentry *dentry)
 217 {
 218         return dentry->d_name.name != dentry->d_iname;
 219 }
 220
 221 /*
 222  * These are the low-level FS interfaces to the dcache..
 223  */
 224 extern void d_instantiate(struct dentry *, struct inode *);
 225 extern struct dentry * d_instantiate_unique(struct dentry *, struct inode *);
 226 extern struct dentry * d_materialise_unique(struct dentry *, struct inode *);
 227 extern void d_delete(struct dentry *);
 228
 229 /* allocate/de-allocate */
 230 extern struct dentry * d_alloc(struct dentry *, const struct qstr *);
 231 extern struct dentry * d_alloc_anon(struct inode *);
 232 extern struct dentry * d_splice_alias(struct inode *, struct dentry *);
 233 extern void shrink_dcache_sb(struct super_block *);
 234 extern void shrink_dcache_parent(struct dentry *);
 235 extern void shrink_dcache_for_umount(struct super_block *);
 236 extern int d_invalidate(struct dentry *);
 237
 238 /* only used at mount-time */
 239 extern struct dentry * d_alloc_root(struct inode *);
 240
 241 /* <clickety>-<click> the ramfs-type tree */
 242 extern void d_genocide(struct dentry *);
 243
 244 extern struct dentry *d_find_alias(struct inode *);
 245 extern void d_prune_aliases(struct inode *);
 246
 247 /* test whether we have any submounts in a subdir tree */
 248 extern int have_submounts(struct dentry *);
 249
 250 /*
 251  * This adds the entry to the hash queues.
 252  */
 253 extern void d_rehash(struct dentry *);
 254
 255 /**
 256  * d_add - add dentry to hash queues
 257  * @entry: dentry to add
 258  * @inode: The inode to attach to this dentry
 259  *
 260  * This adds the entry to the hash queues and initializes @inode.
 261  * The entry was actually filled in earlier during d_alloc().
 262  */
 263
 264 static inline void d_add(struct dentry *entry, struct inode *inode)
 265 {
 266         d_instantiate(entry, inode);
 267         d_rehash(entry);
 268 }
 269
 270 /**
 271  * d_add_unique - add dentry to hash queues without aliasing
 272  * @entry: dentry to add
 273  * @inode: The inode to attach to this dentry
 274  *
 275  * This adds the entry to the hash queues and initializes @inode.
 276  * The entry was actually filled in earlier during d_alloc().
 277  */
 278 static inline struct dentry *d_add_unique(struct dentry *entry, struct inode *inode)
 279 {
 280         struct dentry *res;
 281
 282         res = d_instantiate_unique(entry, inode);
 283         d_rehash(res != NULL ? res : entry);
 284         return res;
 285 }
 286
 287 /* used for rename() and baskets */
 288 extern void d_move(struct dentry *, struct dentry *);
 289
 290 /* appendix may either be NULL or be used for transname suffixes */
 291 extern struct dentry * d_lookup(struct dentry *, struct qstr *);
 292 extern struct dentry * __d_lookup(struct dentry *, struct qstr *);
 293 extern struct dentry * d_hash_and_lookup(struct dentry *, struct qstr *);
 294
 295 /* validate "insecure" dentry pointer */
 296 extern int d_validate(struct dentry *, struct dentry *);
 297
 298 /*
 299  * helper function for dentry_operations.d_dname() members
 300  */
 301 extern char *dynamic_dname(struct dentry *, char *, int, const char *, ...);
 302
 303 extern char *__d_path(const struct path *path, struct path *root, char *, int);
 304 extern char *d_path(struct path *, char *, int);
 305 extern char *dentry_path(struct dentry *, char *, int);
 306
 307 /* Allocation counts.. */
 308
 309 /**
 310  *      dget, dget_locked       -       get a reference to a dentry
 311  *      @dentry: dentry to get a reference to
 312  *
 313  *      Given a dentry or %NULL pointer increment the reference count
 314  *      if appropriate and return the dentry. A dentry will not be
 315  *      destroyed when it has references. dget() should never be
 316  *      called for dentries with zero reference counter. For these cases
 317  *      (preferably none, functions in dcache.c are sufficient for normal
 318  *      needs and they take necessary precautions) you should hold dcache_lock
 319  *      and call dget_locked() instead of dget().
 320  */
 321
 322 static inline struct dentry *dget(struct dentry *dentry)
 323 {
 324         if (dentry) {
 325                 BUG_ON(!atomic_read(&dentry->d_count));
 326                 atomic_inc(&dentry->d_count);
 327         }
 328         return dentry;
 329 }
 330
 331 extern struct dentry * dget_locked(struct dentry *);
 332
 333 /**
 334  *      d_unhashed -    is dentry hashed
 335  *      @dentry: entry to check
 336  *
 337  *      Returns true if the dentry passed is not currently hashed.
 338  */
 339
 340 static inline int d_unhashed(struct dentry *dentry)
 341 {
 342         return (dentry->d_flags & DCACHE_UNHASHED);
 343 }
 344
 345 static inline struct dentry *dget_parent(struct dentry *dentry)
 346 {
 347         struct dentry *ret;
 348
 349         spin_lock(&dentry->d_lock);
 350         ret = dget(dentry->d_parent);
 351         spin_unlock(&dentry->d_lock);
 352         return ret;
 353 }
 354
 355 extern void dput(struct dentry *);
 356
 357 static inline int d_mountpoint(struct dentry *dentry)
 358 {
 359         return dentry->d_mounted;
 360 }
 361
 362 extern struct vfsmount *lookup_mnt(struct vfsmount *, struct dentry *);
 363 extern struct dentry *lookup_create(struct nameidata *nd, int is_dir);
 364
 365 extern int sysctl_vfs_cache_pressure;
 366
 367 #endif  /* __LINUX_DCACHE_H */