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 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 struct dentry_operations {
 118         int (*d_revalidate)(struct dentry *, struct nameidata *);
 119         int (*d_hash) (struct dentry *, struct qstr *);
 120         int (*d_compare) (struct dentry *, struct qstr *, struct qstr *);
 121         int (*d_delete)(struct dentry *);
 122         void (*d_release)(struct dentry *);
 123         void (*d_iput)(struct dentry *, struct inode *);
 124 };
 125
 126 /* the dentry parameter passed to d_hash and d_compare is the parent
 127  * directory of the entries to be compared. It is used in case these
 128  * functions need any directory specific information for determining
 129  * equivalency classes.  Using the dentry itself might not work, as it
 130  * might be a negative dentry which has no information associated with
 131  * it */
 132
 133 /*
 134 locking rules:
 135                 big lock        dcache_lock     d_lock   may block
 136 d_revalidate:   no              no              no       yes
 137 d_hash          no              no              no       yes
 138 d_compare:      no              yes             yes      no
 139 d_delete:       no              yes             no       no
 140 d_release:      no              no              no       yes
 141 d_iput:         no              no              no       yes
 142  */
 143
 144 /* d_flags entries */
 145 #define DCACHE_AUTOFS_PENDING 0x0001    /* autofs: "under construction" */
 146 #define DCACHE_NFSFS_RENAMED  0x0002    /* this dentry has been "silly
 147                                          * renamed" and has to be
 148                                          * deleted on the last dput()
 149                                          */
 150 #define DCACHE_DISCONNECTED 0x0004
 151      /* This dentry is possibly not currently connected to the dcache tree,
 152       * in which case its parent will either be itself, or will have this
 153       * flag as well.  nfsd will not use a dentry with this bit set, but will
 154       * first endeavour to clear the bit either by discovering that it is
 155       * connected, or by performing lookup operations.   Any filesystem which
 156       * supports nfsd_operations MUST have a lookup function which, if it finds
 157       * a directory inode with a DCACHE_DISCONNECTED dentry, will d_move
 158       * that dentry into place and return that dentry rather than the passed one,
 159       * typically using d_splice_alias.
 160       */
 161
 162 #define DCACHE_REFERENCED       0x0008  /* Recently used, don't discard. */
 163 #define DCACHE_UNHASHED         0x0010
 164
 165 #define DCACHE_INOTIFY_PARENT_WATCHED   0x0020 /* Parent inode is watched */
 166
 167 extern spinlock_t dcache_lock;
 168
 169 /**
 170  * d_drop - drop a dentry
 171  * @dentry: dentry to drop
 172  *
 173  * d_drop() unhashes the entry from the parent dentry hashes, so that it won't
 174  * be found through a VFS lookup any more. Note that this is different from
 175  * deleting the dentry - d_delete will try to mark the dentry negative if
 176  * possible, giving a successful _negative_ lookup, while d_drop will
 177  * just make the cache lookup fail.
 178  *
 179  * d_drop() is used mainly for stuff that wants to invalidate a dentry for some
 180  * reason (NFS timeouts or autofs deletes).
 181  *
 182  * __d_drop requires dentry->d_lock.
 183  */
 184
 185 static inline void __d_drop(struct dentry *dentry)
 186 {
 187         if (!(dentry->d_flags & DCACHE_UNHASHED)) {
 188                 dentry->d_flags |= DCACHE_UNHASHED;
 189                 hlist_del_rcu(&dentry->d_hash);
 190         }
 191 }
 192
 193 static inline void d_drop(struct dentry *dentry)
 194 {
 195         spin_lock(&dcache_lock);
 196         spin_lock(&dentry->d_lock);
 197         __d_drop(dentry);
 198         spin_unlock(&dentry->d_lock);
 199         spin_unlock(&dcache_lock);
 200 }
 201
 202 static inline int dname_external(struct dentry *dentry)
 203 {
 204         return dentry->d_name.name != dentry->d_iname;
 205 }
 206
 207 /*
 208  * These are the low-level FS interfaces to the dcache..
 209  */
 210 extern void d_instantiate(struct dentry *, struct inode *);
 211 extern struct dentry * d_instantiate_unique(struct dentry *, struct inode *);
 212 extern void d_delete(struct dentry *);
 213
 214 /* allocate/de-allocate */
 215 extern struct dentry * d_alloc(struct dentry *, const struct qstr *);
 216 extern struct dentry * d_alloc_anon(struct inode *);
 217 extern struct dentry * d_splice_alias(struct inode *, struct dentry *);
 218 extern void shrink_dcache_sb(struct super_block *);
 219 extern void shrink_dcache_parent(struct dentry *);
 220 extern void shrink_dcache_anon(struct hlist_head *);
 221 extern int d_invalidate(struct dentry *);
 222
 223 /* only used at mount-time */
 224 extern struct dentry * d_alloc_root(struct inode *);
 225
 226 /* <clickety>-<click> the ramfs-type tree */
 227 extern void d_genocide(struct dentry *);
 228
 229 extern struct dentry *d_find_alias(struct inode *);
 230 extern void d_prune_aliases(struct inode *);
 231
 232 /* test whether we have any submounts in a subdir tree */
 233 extern int have_submounts(struct dentry *);
 234
 235 /*
 236  * This adds the entry to the hash queues.
 237  */
 238 extern void d_rehash(struct dentry *);
 239
 240 /**
 241  * d_add - add dentry to hash queues
 242  * @entry: dentry to add
 243  * @inode: The inode to attach to this dentry
 244  *
 245  * This adds the entry to the hash queues and initializes @inode.
 246  * The entry was actually filled in earlier during d_alloc().
 247  */
 248
 249 static inline void d_add(struct dentry *entry, struct inode *inode)
 250 {
 251         d_instantiate(entry, inode);
 252         d_rehash(entry);
 253 }
 254
 255 /**
 256  * d_add_unique - add dentry to hash queues without aliasing
 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 static inline struct dentry *d_add_unique(struct dentry *entry, struct inode *inode)
 264 {
 265         struct dentry *res;
 266
 267         res = d_instantiate_unique(entry, inode);
 268         d_rehash(res != NULL ? res : entry);
 269         return res;
 270 }
 271
 272 /* used for rename() and baskets */
 273 extern void d_move(struct dentry *, struct dentry *);
 274
 275 /* appendix may either be NULL or be used for transname suffixes */
 276 extern struct dentry * d_lookup(struct dentry *, struct qstr *);
 277 extern struct dentry * __d_lookup(struct dentry *, struct qstr *);
 278 extern struct dentry * d_hash_and_lookup(struct dentry *, struct qstr *);
 279
 280 /* validate "insecure" dentry pointer */
 281 extern int d_validate(struct dentry *, struct dentry *);
 282
 283 extern char * d_path(struct dentry *, struct vfsmount *, char *, int);
 284
 285 /* Allocation counts.. */
 286
 287 /**
 288  *      dget, dget_locked       -       get a reference to a dentry
 289  *      @dentry: dentry to get a reference to
 290  *
 291  *      Given a dentry or %NULL pointer increment the reference count
 292  *      if appropriate and return the dentry. A dentry will not be
 293  *      destroyed when it has references. dget() should never be
 294  *      called for dentries with zero reference counter. For these cases
 295  *      (preferably none, functions in dcache.c are sufficient for normal
 296  *      needs and they take necessary precautions) you should hold dcache_lock
 297  *      and call dget_locked() instead of dget().
 298  */
 299
 300 static inline struct dentry *dget(struct dentry *dentry)
 301 {
 302         if (dentry) {
 303                 BUG_ON(!atomic_read(&dentry->d_count));
 304                 atomic_inc(&dentry->d_count);
 305         }
 306         return dentry;
 307 }
 308
 309 extern struct dentry * dget_locked(struct dentry *);
 310
 311 /**
 312  *      d_unhashed -    is dentry hashed
 313  *      @dentry: entry to check
 314  *
 315  *      Returns true if the dentry passed is not currently hashed.
 316  */
 317
 318 static inline int d_unhashed(struct dentry *dentry)
 319 {
 320         return (dentry->d_flags & DCACHE_UNHASHED);
 321 }
 322
 323 static inline struct dentry *dget_parent(struct dentry *dentry)
 324 {
 325         struct dentry *ret;
 326
 327         spin_lock(&dentry->d_lock);
 328         ret = dget(dentry->d_parent);
 329         spin_unlock(&dentry->d_lock);
 330         return ret;
 331 }
 332
 333 extern void dput(struct dentry *);
 334
 335 static inline int d_mountpoint(struct dentry *dentry)
 336 {
 337         return dentry->d_mounted;
 338 }
 339
 340 extern struct vfsmount *lookup_mnt(struct vfsmount *, struct dentry *);
 341 extern struct vfsmount *__lookup_mnt(struct vfsmount *, struct dentry *, int);
 342 extern struct dentry *lookup_create(struct nameidata *nd, int is_dir);
 343
 344 extern int sysctl_vfs_cache_pressure;
 345
 346 #endif /* __KERNEL__ */
 347
 348 #endif  /* __LINUX_DCACHE_H */