1 #ifndef __LINUX_DCACHE_H 2 #define __LINUX_DCACHE_H 3 4 #include <asm/atomic.h> 5 #include <linux/list.h> 6 #include <linux/spinlock.h> 7 #include <linux/cache.h> 8 #include <linux/rcupdate.h> 9 10 struct nameidata; 11 struct path; 12 struct vfsmount; 13 14 /* 15 * linux/include/linux/dcache.h 16 * 17 * Dirent cache data structures 18 * 19 * (C) Copyright 1997 Thomas Schoebel-Theuer, 20 * with heavy changes by Linus Torvalds 21 */ 22 23 #define IS_ROOT(x) ((x) == (x)->d_parent) 24 25 /* 26 * "quick string" -- eases parameter passing, but more importantly 27 * saves "metadata" about the string (ie length and the hash). 28 * 29 * hash comes first so it snuggles against d_parent in the 30 * dentry. 31 */ 32 struct qstr { 33 unsigned int hash; 34 unsigned int len; 35 const unsigned char *name; 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 struct dcookie_struct; 78 79 #define DNAME_INLINE_LEN_MIN 36 80 81 struct dentry { 82 atomic_t d_count; 83 unsigned int d_flags; /* protected by d_lock */ 84 spinlock_t d_lock; /* per dentry lock */ 85 struct inode *d_inode; /* Where the name belongs to - NULL is 86 * negative */ 87 /* 88 * The next three fields are touched by __d_lookup. Place them here 89 * so they all fit in a cache line. 90 */ 91 struct hlist_node d_hash; /* lookup hash list */ 92 struct dentry *d_parent; /* parent directory */ 93 struct qstr d_name; 94 95 struct list_head d_lru; /* LRU list */ 96 /* 97 * d_child and d_rcu can share memory 98 */ 99 union { 100 struct list_head d_child; /* child of parent list */ 101 struct rcu_head d_rcu; 102 } d_u; 103 struct list_head d_subdirs; /* our children */ 104 struct list_head d_alias; /* inode alias list */ 105 unsigned long d_time; /* used by d_revalidate */ 106 struct dentry_operations *d_op; 107 struct super_block *d_sb; /* The root of the dentry tree */ 108 void *d_fsdata; /* fs-specific data */ 109 #ifdef CONFIG_PROFILING 110 struct dcookie_struct *d_cookie; /* cookie, if any */ 111 #endif 112 int d_mounted; 113 unsigned char d_iname[DNAME_INLINE_LEN_MIN]; /* small names */ 114 }; 115 116 /* 117 * dentry->d_lock spinlock nesting subclasses: 118 * 119 * 0: normal 120 * 1: nested 121 */ 122 enum dentry_d_lock_class 123 { 124 DENTRY_D_LOCK_NORMAL, /* implicitly used by plain spin_lock() APIs. */ 125 DENTRY_D_LOCK_NESTED 126 }; 127 128 struct dentry_operations { 129 int (*d_revalidate)(struct dentry *, struct nameidata *); 130 int (*d_hash) (struct dentry *, struct qstr *); 131 int (*d_compare) (struct dentry *, struct qstr *, struct qstr *); 132 int (*d_delete)(struct dentry *); 133 void (*d_release)(struct dentry *); 134 void (*d_iput)(struct dentry *, struct inode *); 135 char *(*d_dname)(struct dentry *, char *, int); 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 extern seqlock_t rename_lock; 181 182 /** 183 * d_drop - drop a dentry 184 * @dentry: dentry to drop 185 * 186 * d_drop() unhashes the entry from the parent dentry hashes, so that it won't 187 * be found through a VFS lookup any more. Note that this is different from 188 * deleting the dentry - d_delete will try to mark the dentry negative if 189 * possible, giving a successful _negative_ lookup, while d_drop will 190 * just make the cache lookup fail. 191 * 192 * d_drop() is used mainly for stuff that wants to invalidate a dentry for some 193 * reason (NFS timeouts or autofs deletes). 194 * 195 * __d_drop requires dentry->d_lock. 196 */ 197 198 static inline void __d_drop(struct dentry *dentry) 199 { 200 if (!(dentry->d_flags & DCACHE_UNHASHED)) { 201 dentry->d_flags |= DCACHE_UNHASHED; 202 hlist_del_rcu(&dentry->d_hash); 203 } 204 } 205 206 static inline void d_drop(struct dentry *dentry) 207 { 208 spin_lock(&dcache_lock); 209 spin_lock(&dentry->d_lock); 210 __d_drop(dentry); 211 spin_unlock(&dentry->d_lock); 212 spin_unlock(&dcache_lock); 213 } 214 215 static inline int dname_external(struct dentry *dentry) 216 { 217 return dentry->d_name.name != dentry->d_iname; 218 } 219 220 /* 221 * These are the low-level FS interfaces to the dcache.. 222 */ 223 extern void d_instantiate(struct dentry *, struct inode *); 224 extern struct dentry * d_instantiate_unique(struct dentry *, struct inode *); 225 extern struct dentry * d_materialise_unique(struct dentry *, struct inode *); 226 extern void d_delete(struct dentry *); 227 228 /* allocate/de-allocate */ 229 extern struct dentry * d_alloc(struct dentry *, const struct qstr *); 230 extern struct dentry * d_alloc_anon(struct inode *); 231 extern struct dentry * d_splice_alias(struct inode *, struct dentry *); 232 extern void shrink_dcache_sb(struct super_block *); 233 extern void shrink_dcache_parent(struct dentry *); 234 extern void shrink_dcache_for_umount(struct super_block *); 235 extern int d_invalidate(struct dentry *); 236 237 /* only used at mount-time */ 238 extern struct dentry * d_alloc_root(struct inode *); 239 240 /* <clickety>-<click> the ramfs-type tree */ 241 extern void d_genocide(struct dentry *); 242 243 extern struct dentry *d_find_alias(struct inode *); 244 extern void d_prune_aliases(struct inode *); 245 246 /* test whether we have any submounts in a subdir tree */ 247 extern int have_submounts(struct dentry *); 248 249 /* 250 * This adds the entry to the hash queues. 251 */ 252 extern void d_rehash(struct dentry *); 253 254 /** 255 * d_add - add dentry to hash queues 256 * @entry: dentry to add 257 * @inode: The inode to attach to this dentry 258 * 259 * This adds the entry to the hash queues and initializes @inode. 260 * The entry was actually filled in earlier during d_alloc(). 261 */ 262 263 static inline void d_add(struct dentry *entry, struct inode *inode) 264 { 265 d_instantiate(entry, inode); 266 d_rehash(entry); 267 } 268 269 /** 270 * d_add_unique - add dentry to hash queues without aliasing 271 * @entry: dentry to add 272 * @inode: The inode to attach to this dentry 273 * 274 * This adds the entry to the hash queues and initializes @inode. 275 * The entry was actually filled in earlier during d_alloc(). 276 */ 277 static inline struct dentry *d_add_unique(struct dentry *entry, struct inode *inode) 278 { 279 struct dentry *res; 280 281 res = d_instantiate_unique(entry, inode); 282 d_rehash(res != NULL ? res : entry); 283 return res; 284 } 285 286 /* used for rename() and baskets */ 287 extern void d_move(struct dentry *, struct dentry *); 288 289 /* appendix may either be NULL or be used for transname suffixes */ 290 extern struct dentry * d_lookup(struct dentry *, struct qstr *); 291 extern struct dentry * __d_lookup(struct dentry *, struct qstr *); 292 extern struct dentry * d_hash_and_lookup(struct dentry *, struct qstr *); 293 294 /* validate "insecure" dentry pointer */ 295 extern int d_validate(struct dentry *, struct dentry *); 296 297 /* 298 * helper function for dentry_operations.d_dname() members 299 */ 300 extern char *dynamic_dname(struct dentry *, char *, int, const char *, ...); 301 302 extern char *__d_path(const struct path *path, struct path *root, char *, int); 303 extern char *d_path(struct path *, char *, int); 304 extern char *dentry_path(struct dentry *, char *, int); 305 306 /* Allocation counts.. */ 307 308 /** 309 * dget, dget_locked - get a reference to a dentry 310 * @dentry: dentry to get a reference to 311 * 312 * Given a dentry or %NULL pointer increment the reference count 313 * if appropriate and return the dentry. A dentry will not be 314 * destroyed when it has references. dget() should never be 315 * called for dentries with zero reference counter. For these cases 316 * (preferably none, functions in dcache.c are sufficient for normal 317 * needs and they take necessary precautions) you should hold dcache_lock 318 * and call dget_locked() instead of dget(). 319 */ 320 321 static inline struct dentry *dget(struct dentry *dentry) 322 { 323 if (dentry) { 324 BUG_ON(!atomic_read(&dentry->d_count)); 325 atomic_inc(&dentry->d_count); 326 } 327 return dentry; 328 } 329 330 extern struct dentry * dget_locked(struct dentry *); 331 332 /** 333 * d_unhashed - is dentry hashed 334 * @dentry: entry to check 335 * 336 * Returns true if the dentry passed is not currently hashed. 337 */ 338 339 static inline int d_unhashed(struct dentry *dentry) 340 { 341 return (dentry->d_flags & DCACHE_UNHASHED); 342 } 343 344 static inline struct dentry *dget_parent(struct dentry *dentry) 345 { 346 struct dentry *ret; 347 348 spin_lock(&dentry->d_lock); 349 ret = dget(dentry->d_parent); 350 spin_unlock(&dentry->d_lock); 351 return ret; 352 } 353 354 extern void dput(struct dentry *); 355 356 static inline int d_mountpoint(struct dentry *dentry) 357 { 358 return dentry->d_mounted; 359 } 360 361 extern struct vfsmount *lookup_mnt(struct vfsmount *, struct dentry *); 362 extern struct dentry *lookup_create(struct nameidata *nd, int is_dir); 363 364 extern int sysctl_vfs_cache_pressure; 365 366 #endif /* __LINUX_DCACHE_H */ 367