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 /* 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 }; 137 138 /* the dentry parameter passed to d_hash and d_compare is the parent 139 * directory of the entries to be compared. It is used in case these 140 * functions need any directory specific information for determining 141 * equivalency classes. Using the dentry itself might not work, as it 142 * might be a negative dentry which has no information associated with 143 * it */ 144 145 /* 146 locking rules: 147 big lock dcache_lock d_lock may block 148 d_revalidate: no no no yes 149 d_hash no no no yes 150 d_compare: no yes yes no 151 d_delete: no yes no no 152 d_release: no no no yes 153 d_iput: no no no yes 154 */ 155 156 /* d_flags entries */ 157 #define DCACHE_AUTOFS_PENDING 0x0001 /* autofs: "under construction" */ 158 #define DCACHE_NFSFS_RENAMED 0x0002 /* this dentry has been "silly 159 * renamed" and has to be 160 * deleted on the last dput() 161 */ 162 #define DCACHE_DISCONNECTED 0x0004 163 /* This dentry is possibly not currently connected to the dcache tree, 164 * in which case its parent will either be itself, or will have this 165 * flag as well. nfsd will not use a dentry with this bit set, but will 166 * first endeavour to clear the bit either by discovering that it is 167 * connected, or by performing lookup operations. Any filesystem which 168 * supports nfsd_operations MUST have a lookup function which, if it finds 169 * a directory inode with a DCACHE_DISCONNECTED dentry, will d_move 170 * that dentry into place and return that dentry rather than the passed one, 171 * typically using d_splice_alias. 172 */ 173 174 #define DCACHE_REFERENCED 0x0008 /* Recently used, don't discard. */ 175 #define DCACHE_UNHASHED 0x0010 176 177 #define DCACHE_INOTIFY_PARENT_WATCHED 0x0020 /* Parent inode is watched */ 178 179 extern spinlock_t dcache_lock; 180 181 /** 182 * d_drop - drop a dentry 183 * @dentry: dentry to drop 184 * 185 * d_drop() unhashes the entry from the parent dentry hashes, so that it won't 186 * be found through a VFS lookup any more. Note that this is different from 187 * deleting the dentry - d_delete will try to mark the dentry negative if 188 * possible, giving a successful _negative_ lookup, while d_drop will 189 * just make the cache lookup fail. 190 * 191 * d_drop() is used mainly for stuff that wants to invalidate a dentry for some 192 * reason (NFS timeouts or autofs deletes). 193 * 194 * __d_drop requires dentry->d_lock. 195 */ 196 197 static inline void __d_drop(struct dentry *dentry) 198 { 199 if (!(dentry->d_flags & DCACHE_UNHASHED)) { 200 dentry->d_flags |= DCACHE_UNHASHED; 201 hlist_del_rcu(&dentry->d_hash); 202 } 203 } 204 205 static inline void d_drop(struct dentry *dentry) 206 { 207 spin_lock(&dcache_lock); 208 spin_lock(&dentry->d_lock); 209 __d_drop(dentry); 210 spin_unlock(&dentry->d_lock); 211 spin_unlock(&dcache_lock); 212 } 213 214 static inline int dname_external(struct dentry *dentry) 215 { 216 return dentry->d_name.name != dentry->d_iname; 217 } 218 219 /* 220 * These are the low-level FS interfaces to the dcache.. 221 */ 222 extern void d_instantiate(struct dentry *, struct inode *); 223 extern struct dentry * d_instantiate_unique(struct dentry *, struct inode *); 224 extern struct dentry * d_materialise_unique(struct dentry *, struct inode *); 225 extern void d_delete(struct dentry *); 226 227 /* allocate/de-allocate */ 228 extern struct dentry * d_alloc(struct dentry *, const struct qstr *); 229 extern struct dentry * d_alloc_anon(struct inode *); 230 extern struct dentry * d_splice_alias(struct inode *, struct dentry *); 231 extern void shrink_dcache_sb(struct super_block *); 232 extern void shrink_dcache_parent(struct dentry *); 233 extern void shrink_dcache_for_umount(struct super_block *); 234 extern int d_invalidate(struct dentry *); 235 236 /* only used at mount-time */ 237 extern struct dentry * d_alloc_root(struct inode *); 238 239 /* <clickety>-<click> the ramfs-type tree */ 240 extern void d_genocide(struct dentry *); 241 242 extern struct dentry *d_find_alias(struct inode *); 243 extern void d_prune_aliases(struct inode *); 244 245 /* test whether we have any submounts in a subdir tree */ 246 extern int have_submounts(struct dentry *); 247 248 /* 249 * This adds the entry to the hash queues. 250 */ 251 extern void d_rehash(struct dentry *); 252 253 /** 254 * d_add - add dentry to hash queues 255 * @entry: dentry to add 256 * @inode: The inode to attach to this dentry 257 * 258 * This adds the entry to the hash queues and initializes @inode. 259 * The entry was actually filled in earlier during d_alloc(). 260 */ 261 262 static inline void d_add(struct dentry *entry, struct inode *inode) 263 { 264 d_instantiate(entry, inode); 265 d_rehash(entry); 266 } 267 268 /** 269 * d_add_unique - add dentry to hash queues without aliasing 270 * @entry: dentry to add 271 * @inode: The inode to attach to this dentry 272 * 273 * This adds the entry to the hash queues and initializes @inode. 274 * The entry was actually filled in earlier during d_alloc(). 275 */ 276 static inline struct dentry *d_add_unique(struct dentry *entry, struct inode *inode) 277 { 278 struct dentry *res; 279 280 res = d_instantiate_unique(entry, inode); 281 d_rehash(res != NULL ? res : entry); 282 return res; 283 } 284 285 /* used for rename() and baskets */ 286 extern void d_move(struct dentry *, struct dentry *); 287 288 /* appendix may either be NULL or be used for transname suffixes */ 289 extern struct dentry * d_lookup(struct dentry *, struct qstr *); 290 extern struct dentry * __d_lookup(struct dentry *, struct qstr *); 291 extern struct dentry * d_hash_and_lookup(struct dentry *, struct qstr *); 292 293 /* validate "insecure" dentry pointer */ 294 extern int d_validate(struct dentry *, struct dentry *); 295 296 extern char * d_path(struct dentry *, struct vfsmount *, char *, int); 297 298 /* Allocation counts.. */ 299 300 /** 301 * dget, dget_locked - get a reference to a dentry 302 * @dentry: dentry to get a reference to 303 * 304 * Given a dentry or %NULL pointer increment the reference count 305 * if appropriate and return the dentry. A dentry will not be 306 * destroyed when it has references. dget() should never be 307 * called for dentries with zero reference counter. For these cases 308 * (preferably none, functions in dcache.c are sufficient for normal 309 * needs and they take necessary precautions) you should hold dcache_lock 310 * and call dget_locked() instead of dget(). 311 */ 312 313 static inline struct dentry *dget(struct dentry *dentry) 314 { 315 if (dentry) { 316 BUG_ON(!atomic_read(&dentry->d_count)); 317 atomic_inc(&dentry->d_count); 318 } 319 return dentry; 320 } 321 322 extern struct dentry * dget_locked(struct dentry *); 323 324 /** 325 * d_unhashed - is dentry hashed 326 * @dentry: entry to check 327 * 328 * Returns true if the dentry passed is not currently hashed. 329 */ 330 331 static inline int d_unhashed(struct dentry *dentry) 332 { 333 return (dentry->d_flags & DCACHE_UNHASHED); 334 } 335 336 static inline struct dentry *dget_parent(struct dentry *dentry) 337 { 338 struct dentry *ret; 339 340 spin_lock(&dentry->d_lock); 341 ret = dget(dentry->d_parent); 342 spin_unlock(&dentry->d_lock); 343 return ret; 344 } 345 346 extern void dput(struct dentry *); 347 348 static inline int d_mountpoint(struct dentry *dentry) 349 { 350 return dentry->d_mounted; 351 } 352 353 extern struct vfsmount *lookup_mnt(struct vfsmount *, struct dentry *); 354 extern struct vfsmount *__lookup_mnt(struct vfsmount *, struct dentry *, int); 355 extern struct dentry *lookup_create(struct nameidata *nd, int is_dir); 356 357 extern int sysctl_vfs_cache_pressure; 358 359 #endif /* __KERNEL__ */ 360 361 #endif /* __LINUX_DCACHE_H */ 362