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 #include <asm/bug.h>
  12
  13 struct nameidata;
  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 struct qstr {
  32         const unsigned char * name;
  33         unsigned int len;
  34         unsigned int hash;
  35         char name_str[0];
  36 };
  37
  38 struct dentry_stat_t {
  39         int nr_dentry;
  40         int nr_unused;
  41         int age_limit;          /* age in seconds */
  42         int want_pages;         /* pages requested by system */
  43         int dummy[2];
  44 };
  45 extern struct dentry_stat_t dentry_stat;
  46
  47 /* Name hashing routines. Initial hash value */
  48 /* Hash courtesy of the R5 hash in reiserfs modulo sign bits */
  49 #define init_name_hash()                0
  50
  51 /* partial hash update function. Assume roughly 4 bits per character */
  52 static inline unsigned long
  53 partial_name_hash(unsigned long c, unsigned long prevhash)
  54 {
  55         return (prevhash + (c << 4) + (c >> 4)) * 11;
  56 }
  57
  58 /*
  59  * Finally: cut down the number of bits to a int value (and try to avoid
  60  * losing bits)
  61  */
  62 static inline unsigned long end_name_hash(unsigned long hash)
  63 {
  64         return (unsigned int) hash;
  65 }
  66
  67 /* Compute the hash for a name string. */
  68 static inline unsigned int
  69 full_name_hash(const unsigned char *name, unsigned int len)
  70 {
  71         unsigned long hash = init_name_hash();
  72         while (len--)
  73                 hash = partial_name_hash(*name++, hash);
  74         return end_name_hash(hash);
  75 }
  76
  77 #define DNAME_INLINE_LEN_MIN 16
  78
  79 struct dcookie_struct;
  80
  81 struct dentry {
  82         atomic_t d_count;
  83         unsigned long d_vfs_flags;      /* moved here to be on same cacheline */
  84         spinlock_t d_lock;              /* per dentry lock */
  85         struct inode  * d_inode;        /* Where the name belongs to - NULL is negative */
  86         struct list_head d_lru;         /* LRU list */
  87         struct list_head d_child;       /* child of parent list */
  88         struct list_head d_subdirs;     /* our children */
  89         struct list_head d_alias;       /* inode alias list */
  90         unsigned long d_time;           /* used by d_revalidate */
  91         struct dentry_operations  *d_op;
  92         struct super_block * d_sb;      /* The root of the dentry tree */
  93         unsigned int d_flags;
  94         int d_mounted;
  95         void * d_fsdata;                /* fs-specific data */
  96         struct rcu_head d_rcu;
  97         struct dcookie_struct * d_cookie; /* cookie, if any */
  98         unsigned long d_move_count;     /* to indicated moved dentry while lockless lookup */
  99         struct qstr * d_qstr;           /* quick str ptr used in lockless lookup and concurrent d_move */
 100         struct dentry * d_parent;       /* parent directory */
 101         struct qstr d_name;
 102         struct hlist_node d_hash;       /* lookup hash list */
 103         struct hlist_head * d_bucket;   /* lookup hash bucket */
 104         unsigned char d_iname[DNAME_INLINE_LEN_MIN]; /* small names */
 105 } ____cacheline_aligned;
 106
 107 #define DNAME_INLINE_LEN        (sizeof(struct dentry)-offsetof(struct dentry,d_iname))
 108
 109 struct dentry_operations {
 110         int (*d_revalidate)(struct dentry *, struct nameidata *);
 111         int (*d_hash) (struct dentry *, struct qstr *);
 112         int (*d_compare) (struct dentry *, struct qstr *, struct qstr *);
 113         int (*d_delete)(struct dentry *);
 114         void (*d_release)(struct dentry *);
 115         void (*d_iput)(struct dentry *, struct inode *);
 116 };
 117
 118 /* the dentry parameter passed to d_hash and d_compare is the parent
 119  * directory of the entries to be compared. It is used in case these
 120  * functions need any directory specific information for determining
 121  * equivalency classes.  Using the dentry itself might not work, as it
 122  * might be a negative dentry which has no information associated with
 123  * it */
 124
 125 /*
 126 locking rules:
 127                 big lock        dcache_lock     may block
 128 d_revalidate:   no              no              yes
 129 d_hash          no              no              yes
 130 d_compare:      no              yes             no
 131 d_delete:       no              yes             no
 132 d_release:      no              no              yes
 133 d_iput:         no              no              yes
 134  */
 135
 136 /* d_flags entries */
 137 #define DCACHE_AUTOFS_PENDING 0x0001    /* autofs: "under construction" */
 138 #define DCACHE_NFSFS_RENAMED  0x0002    /* this dentry has been "silly
 139                                          * renamed" and has to be
 140                                          * deleted on the last dput()
 141                                          */
 142 #define DCACHE_DISCONNECTED 0x0004
 143      /* This dentry is possibly not currently connected to the dcache tree,
 144       * in which case its parent will either be itself, or will have this
 145       * flag as well.  nfsd will not use a dentry with this bit set, but will
 146       * first endeavour to clear the bit either by discovering that it is
 147       * connected, or by performing lookup operations.   Any filesystem which
 148       * supports nfsd_operations MUST have a lookup function which, if it finds
 149       * a directory inode with a DCACHE_DISCONNECTED dentry, will d_move
 150       * that dentry into place and return that dentry rather than the passed one,
 151       * typically using d_splice_alias.
 152       */
 153
 154 #define DCACHE_REFERENCED       0x0008  /* Recently used, don't discard. */
 155 #define DCACHE_UNHASHED         0x0010
 156
 157 extern spinlock_t dcache_lock;
 158
 159 /**
 160  * d_drop - drop a dentry
 161  * @dentry: dentry to drop
 162  *
 163  * d_drop() unhashes the entry from the parent
 164  * dentry hashes, so that it won't be found through
 165  * a VFS lookup any more. Note that this is different
 166  * from deleting the dentry - d_delete will try to
 167  * mark the dentry negative if possible, giving a
 168  * successful _negative_ lookup, while d_drop will
 169  * just make the cache lookup fail.
 170  *
 171  * d_drop() is used mainly for stuff that wants
 172  * to invalidate a dentry for some reason (NFS
 173  * timeouts or autofs deletes).
 174  */
 175
 176 static inline void __d_drop(struct dentry *dentry)
 177 {
 178         if (!(dentry->d_vfs_flags & DCACHE_UNHASHED)) {
 179                 dentry->d_vfs_flags |= DCACHE_UNHASHED;
 180                 hlist_del_rcu(&dentry->d_hash);
 181         }
 182 }
 183
 184 static inline void d_drop(struct dentry *dentry)
 185 {
 186         spin_lock(&dcache_lock);
 187         __d_drop(dentry);
 188         spin_unlock(&dcache_lock);
 189 }
 190
 191 static inline int dname_external(struct dentry *d)
 192 {
 193         return d->d_name.name != d->d_iname;
 194 }
 195
 196 /*
 197  * These are the low-level FS interfaces to the dcache..
 198  */
 199 extern void d_instantiate(struct dentry *, struct inode *);
 200 extern void d_delete(struct dentry *);
 201
 202 /* allocate/de-allocate */
 203 extern struct dentry * d_alloc(struct dentry *, const struct qstr *);
 204 extern struct dentry * d_alloc_anon(struct inode *);
 205 extern struct dentry * d_splice_alias(struct inode *, struct dentry *);
 206 extern void shrink_dcache_sb(struct super_block *);
 207 extern void shrink_dcache_parent(struct dentry *);
 208 extern void shrink_dcache_anon(struct hlist_head *);
 209 extern int d_invalidate(struct dentry *);
 210
 211 /* only used at mount-time */
 212 extern struct dentry * d_alloc_root(struct inode *);
 213
 214 /* <clickety>-<click> the ramfs-type tree */
 215 extern void d_genocide(struct dentry *);
 216
 217 extern struct dentry *d_find_alias(struct inode *);
 218 extern void d_prune_aliases(struct inode *);
 219
 220 /* test whether we have any submounts in a subdir tree */
 221 extern int have_submounts(struct dentry *);
 222
 223 /*
 224  * This adds the entry to the hash queues.
 225  */
 226 extern void d_rehash(struct dentry *);
 227
 228 /**
 229  * d_add - add dentry to hash queues
 230  * @entry: dentry to add
 231  * @inode: The inode to attach to this dentry
 232  *
 233  * This adds the entry to the hash queues and initializes @inode.
 234  * The entry was actually filled in earlier during d_alloc().
 235  */
 236
 237 static inline void d_add(struct dentry *entry, struct inode *inode)
 238 {
 239         d_instantiate(entry, inode);
 240         d_rehash(entry);
 241 }
 242
 243 /* used for rename() and baskets */
 244 extern void d_move(struct dentry *, struct dentry *);
 245
 246 /* appendix may either be NULL or be used for transname suffixes */
 247 extern struct dentry * d_lookup(struct dentry *, struct qstr *);
 248 extern struct dentry * __d_lookup(struct dentry *, struct qstr *);
 249
 250 /* validate "insecure" dentry pointer */
 251 extern int d_validate(struct dentry *, struct dentry *);
 252
 253 extern char * d_path(struct dentry *, struct vfsmount *, char *, int);
 254
 255 /* Allocation counts.. */
 256
 257 /**
 258  *      dget, dget_locked       -       get a reference to a dentry
 259  *      @dentry: dentry to get a reference to
 260  *
 261  *      Given a dentry or %NULL pointer increment the reference count
 262  *      if appropriate and return the dentry. A dentry will not be
 263  *      destroyed when it has references. dget() should never be
 264  *      called for dentries with zero reference counter. For these cases
 265  *      (preferably none, functions in dcache.c are sufficient for normal
 266  *      needs and they take necessary precautions) you should hold dcache_lock
 267  *      and call dget_locked() instead of dget().
 268  */
 269
 270 static inline struct dentry *dget(struct dentry *dentry)
 271 {
 272         if (dentry) {
 273                 if (!atomic_read(&dentry->d_count))
 274                         BUG();
 275                 atomic_inc(&dentry->d_count);
 276         }
 277         return dentry;
 278 }
 279
 280 extern struct dentry * dget_locked(struct dentry *);
 281
 282 /**
 283  *      d_unhashed -    is dentry hashed
 284  *      @dentry: entry to check
 285  *
 286  *      Returns true if the dentry passed is not currently hashed.
 287  */
 288
 289 static inline int d_unhashed(struct dentry *dentry)
 290 {
 291         return (dentry->d_vfs_flags & DCACHE_UNHASHED);
 292 }
 293
 294 static inline struct dentry *dget_parent(struct dentry *dentry)
 295 {
 296         struct dentry *ret;
 297
 298         spin_lock(&dentry->d_lock);
 299         ret = dget(dentry->d_parent);
 300         spin_unlock(&dentry->d_lock);
 301         return ret;
 302 }
 303
 304 extern void dput(struct dentry *);
 305
 306 static inline int d_mountpoint(struct dentry *dentry)
 307 {
 308         return dentry->d_mounted;
 309 }
 310
 311 extern struct vfsmount *lookup_mnt(struct vfsmount *, struct dentry *);
 312 #endif /* __KERNEL__ */
 313
 314 #endif  /* __LINUX_DCACHE_H */