Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 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 | * 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 16-byte range, with 16-byte alignment. |
| 92 | */ |
| 93 | struct dentry *d_parent; /* parent directory */ |
| 94 | struct qstr d_name; |
| 95 | |
| 96 | struct list_head d_lru; /* LRU list */ |
| 97 | struct list_head d_child; /* child of parent list */ |
| 98 | struct list_head d_subdirs; /* our children */ |
| 99 | struct list_head d_alias; /* inode alias list */ |
| 100 | unsigned long d_time; /* used by d_revalidate */ |
| 101 | struct dentry_operations *d_op; |
| 102 | struct super_block *d_sb; /* The root of the dentry tree */ |
| 103 | void *d_fsdata; /* fs-specific data */ |
| 104 | struct rcu_head d_rcu; |
| 105 | struct dcookie_struct *d_cookie; /* cookie, if any */ |
| 106 | struct hlist_node d_hash; /* lookup hash list */ |
| 107 | int d_mounted; |
| 108 | unsigned char d_iname[DNAME_INLINE_LEN_MIN]; /* small names */ |
| 109 | }; |
| 110 | |
| 111 | struct dentry_operations { |
| 112 | int (*d_revalidate)(struct dentry *, struct nameidata *); |
| 113 | int (*d_hash) (struct dentry *, struct qstr *); |
| 114 | int (*d_compare) (struct dentry *, struct qstr *, struct qstr *); |
| 115 | int (*d_delete)(struct dentry *); |
| 116 | void (*d_release)(struct dentry *); |
| 117 | void (*d_iput)(struct dentry *, struct inode *); |
| 118 | }; |
| 119 | |
| 120 | /* the dentry parameter passed to d_hash and d_compare is the parent |
| 121 | * directory of the entries to be compared. It is used in case these |
| 122 | * functions need any directory specific information for determining |
| 123 | * equivalency classes. Using the dentry itself might not work, as it |
| 124 | * might be a negative dentry which has no information associated with |
| 125 | * it */ |
| 126 | |
| 127 | /* |
| 128 | locking rules: |
| 129 | big lock dcache_lock d_lock may block |
| 130 | d_revalidate: no no no yes |
| 131 | d_hash no no no yes |
| 132 | d_compare: no yes yes no |
| 133 | d_delete: no yes no no |
| 134 | d_release: no no no yes |
| 135 | d_iput: no no no yes |
| 136 | */ |
| 137 | |
| 138 | /* d_flags entries */ |
| 139 | #define DCACHE_AUTOFS_PENDING 0x0001 /* autofs: "under construction" */ |
| 140 | #define DCACHE_NFSFS_RENAMED 0x0002 /* this dentry has been "silly |
| 141 | * renamed" and has to be |
| 142 | * deleted on the last dput() |
| 143 | */ |
| 144 | #define DCACHE_DISCONNECTED 0x0004 |
| 145 | /* This dentry is possibly not currently connected to the dcache tree, |
| 146 | * in which case its parent will either be itself, or will have this |
| 147 | * flag as well. nfsd will not use a dentry with this bit set, but will |
| 148 | * first endeavour to clear the bit either by discovering that it is |
| 149 | * connected, or by performing lookup operations. Any filesystem which |
| 150 | * supports nfsd_operations MUST have a lookup function which, if it finds |
| 151 | * a directory inode with a DCACHE_DISCONNECTED dentry, will d_move |
| 152 | * that dentry into place and return that dentry rather than the passed one, |
| 153 | * typically using d_splice_alias. |
| 154 | */ |
| 155 | |
| 156 | #define DCACHE_REFERENCED 0x0008 /* Recently used, don't discard. */ |
| 157 | #define DCACHE_UNHASHED 0x0010 |
| 158 | |
| 159 | extern spinlock_t dcache_lock; |
| 160 | |
| 161 | /** |
| 162 | * d_drop - drop a dentry |
| 163 | * @dentry: dentry to drop |
| 164 | * |
| 165 | * d_drop() unhashes the entry from the parent dentry hashes, so that it won't |
| 166 | * be found through a VFS lookup any more. Note that this is different from |
| 167 | * deleting the dentry - d_delete will try to mark the dentry negative if |
| 168 | * possible, giving a 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 to invalidate a dentry for some |
| 172 | * reason (NFS timeouts or autofs deletes). |
| 173 | * |
| 174 | * __d_drop requires dentry->d_lock. |
| 175 | */ |
| 176 | |
| 177 | static inline void __d_drop(struct dentry *dentry) |
| 178 | { |
| 179 | if (!(dentry->d_flags & DCACHE_UNHASHED)) { |
| 180 | dentry->d_flags |= DCACHE_UNHASHED; |
| 181 | hlist_del_rcu(&dentry->d_hash); |
| 182 | } |
| 183 | } |
| 184 | |
| 185 | static inline void d_drop(struct dentry *dentry) |
| 186 | { |
| 187 | spin_lock(&dcache_lock); |
| 188 | spin_lock(&dentry->d_lock); |
| 189 | __d_drop(dentry); |
| 190 | spin_unlock(&dentry->d_lock); |
| 191 | spin_unlock(&dcache_lock); |
| 192 | } |
| 193 | |
| 194 | static inline int dname_external(struct dentry *dentry) |
| 195 | { |
| 196 | return dentry->d_name.name != dentry->d_iname; |
| 197 | } |
| 198 | |
| 199 | /* |
| 200 | * These are the low-level FS interfaces to the dcache.. |
| 201 | */ |
| 202 | extern void d_instantiate(struct dentry *, struct inode *); |
| 203 | extern struct dentry * d_instantiate_unique(struct dentry *, struct inode *); |
| 204 | extern void d_delete(struct dentry *); |
| 205 | |
| 206 | /* allocate/de-allocate */ |
| 207 | extern struct dentry * d_alloc(struct dentry *, const struct qstr *); |
| 208 | extern struct dentry * d_alloc_anon(struct inode *); |
| 209 | extern struct dentry * d_splice_alias(struct inode *, struct dentry *); |
| 210 | extern void shrink_dcache_sb(struct super_block *); |
| 211 | extern void shrink_dcache_parent(struct dentry *); |
| 212 | extern void shrink_dcache_anon(struct hlist_head *); |
| 213 | extern int d_invalidate(struct dentry *); |
| 214 | |
| 215 | /* only used at mount-time */ |
| 216 | extern struct dentry * d_alloc_root(struct inode *); |
| 217 | |
| 218 | /* <clickety>-<click> the ramfs-type tree */ |
| 219 | extern void d_genocide(struct dentry *); |
| 220 | |
| 221 | extern struct dentry *d_find_alias(struct inode *); |
| 222 | extern void d_prune_aliases(struct inode *); |
| 223 | |
| 224 | /* test whether we have any submounts in a subdir tree */ |
| 225 | extern int have_submounts(struct dentry *); |
| 226 | |
| 227 | /* |
| 228 | * This adds the entry to the hash queues. |
| 229 | */ |
| 230 | extern void d_rehash(struct dentry *); |
| 231 | |
| 232 | /** |
| 233 | * d_add - add dentry to hash queues |
| 234 | * @entry: dentry to add |
| 235 | * @inode: The inode to attach to this dentry |
| 236 | * |
| 237 | * This adds the entry to the hash queues and initializes @inode. |
| 238 | * The entry was actually filled in earlier during d_alloc(). |
| 239 | */ |
| 240 | |
| 241 | static inline void d_add(struct dentry *entry, struct inode *inode) |
| 242 | { |
| 243 | d_instantiate(entry, inode); |
| 244 | d_rehash(entry); |
| 245 | } |
| 246 | |
| 247 | /** |
| 248 | * d_add_unique - add dentry to hash queues without aliasing |
| 249 | * @entry: dentry to add |
| 250 | * @inode: The inode to attach to this dentry |
| 251 | * |
| 252 | * This adds the entry to the hash queues and initializes @inode. |
| 253 | * The entry was actually filled in earlier during d_alloc(). |
| 254 | */ |
| 255 | static inline struct dentry *d_add_unique(struct dentry *entry, struct inode *inode) |
| 256 | { |
| 257 | struct dentry *res; |
| 258 | |
| 259 | res = d_instantiate_unique(entry, inode); |
| 260 | d_rehash(res != NULL ? res : entry); |
| 261 | return res; |
| 262 | } |
| 263 | |
| 264 | /* used for rename() and baskets */ |
| 265 | extern void d_move(struct dentry *, struct dentry *); |
| 266 | |
| 267 | /* appendix may either be NULL or be used for transname suffixes */ |
| 268 | extern struct dentry * d_lookup(struct dentry *, struct qstr *); |
| 269 | extern struct dentry * __d_lookup(struct dentry *, struct qstr *); |
| 270 | |
| 271 | /* validate "insecure" dentry pointer */ |
| 272 | extern int d_validate(struct dentry *, struct dentry *); |
| 273 | |
| 274 | extern char * d_path(struct dentry *, struct vfsmount *, char *, int); |
| 275 | |
| 276 | /* Allocation counts.. */ |
| 277 | |
| 278 | /** |
| 279 | * dget, dget_locked - get a reference to a dentry |
| 280 | * @dentry: dentry to get a reference to |
| 281 | * |
| 282 | * Given a dentry or %NULL pointer increment the reference count |
| 283 | * if appropriate and return the dentry. A dentry will not be |
| 284 | * destroyed when it has references. dget() should never be |
| 285 | * called for dentries with zero reference counter. For these cases |
| 286 | * (preferably none, functions in dcache.c are sufficient for normal |
| 287 | * needs and they take necessary precautions) you should hold dcache_lock |
| 288 | * and call dget_locked() instead of dget(). |
| 289 | */ |
| 290 | |
| 291 | static inline struct dentry *dget(struct dentry *dentry) |
| 292 | { |
| 293 | if (dentry) { |
| 294 | BUG_ON(!atomic_read(&dentry->d_count)); |
| 295 | atomic_inc(&dentry->d_count); |
| 296 | } |
| 297 | return dentry; |
| 298 | } |
| 299 | |
| 300 | extern struct dentry * dget_locked(struct dentry *); |
| 301 | |
| 302 | /** |
| 303 | * d_unhashed - is dentry hashed |
| 304 | * @dentry: entry to check |
| 305 | * |
| 306 | * Returns true if the dentry passed is not currently hashed. |
| 307 | */ |
| 308 | |
| 309 | static inline int d_unhashed(struct dentry *dentry) |
| 310 | { |
| 311 | return (dentry->d_flags & DCACHE_UNHASHED); |
| 312 | } |
| 313 | |
| 314 | static inline struct dentry *dget_parent(struct dentry *dentry) |
| 315 | { |
| 316 | struct dentry *ret; |
| 317 | |
| 318 | spin_lock(&dentry->d_lock); |
| 319 | ret = dget(dentry->d_parent); |
| 320 | spin_unlock(&dentry->d_lock); |
| 321 | return ret; |
| 322 | } |
| 323 | |
| 324 | extern void dput(struct dentry *); |
| 325 | |
| 326 | static inline int d_mountpoint(struct dentry *dentry) |
| 327 | { |
| 328 | return dentry->d_mounted; |
| 329 | } |
| 330 | |
| 331 | extern struct vfsmount *lookup_mnt(struct vfsmount *, struct dentry *); |
| 332 | extern struct dentry *lookup_create(struct nameidata *nd, int is_dir); |
| 333 | |
| 334 | extern int sysctl_vfs_cache_pressure; |
| 335 | |
| 336 | #endif /* __KERNEL__ */ |
| 337 | |
| 338 | #endif /* __LINUX_DCACHE_H */ |