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 path; 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 cache line. 92 */ 93 struct hlist_node d_hash; /* lookup hash list */ 94 struct dentry *d_parent; /* parent directory */ 95 struct qstr d_name; 96 97 struct list_head d_lru; /* LRU list */ 98 /* 99 * d_child and d_rcu can share memory 100 */ 101 union { 102 struct list_head d_child; /* child of parent list */ 103 struct rcu_head d_rcu; 104 } d_u; 105 struct list_head d_subdirs; /* our children */ 106 struct list_head d_alias; /* inode alias list */ 107 unsigned long d_time; /* used by d_revalidate */ 108 struct dentry_operations *d_op; 109 struct super_block *d_sb; /* The root of the dentry tree */ 110 void *d_fsdata; /* fs-specific data */ 111 #ifdef CONFIG_PROFILING 112 struct dcookie_struct *d_cookie; /* cookie, if any */ 113 #endif 114 int d_mounted; 115 unsigned char d_iname[DNAME_INLINE_LEN_MIN]; /* small names */ 116 }; 117 118 /* 119 * dentry->d_lock spinlock nesting subclasses: 120 * 121 * 0: normal 122 * 1: nested 123 */ 124 enum dentry_d_lock_class 125 { 126 DENTRY_D_LOCK_NORMAL, /* implicitly used by plain spin_lock() APIs. */ 127 DENTRY_D_LOCK_NESTED 128 }; 129 130 struct dentry_operations { 131 int (*d_revalidate)(struct dentry *, struct nameidata *); 132 int (*d_hash) (struct dentry *, struct qstr *); 133 int (*d_compare) (struct dentry *, struct qstr *, struct qstr *); 134 int (*d_delete)(struct dentry *); 135 void (*d_release)(struct dentry *); 136 void (*d_iput)(struct dentry *, struct inode *); 137 char *(*d_dname)(struct dentry *, char *, int); 138 }; 139 140 /* the dentry parameter passed to d_hash and d_compare is the parent 141 * directory of the entries to be compared. It is used in case these 142 * functions need any directory specific information for determining 143 * equivalency classes. Using the dentry itself might not work, as it 144 * might be a negative dentry which has no information associated with 145 * it */ 146 147 /* 148 locking rules: 149 big lock dcache_lock d_lock may block 150 d_revalidate: no no no yes 151 d_hash no no no yes 152 d_compare: no yes yes no 153 d_delete: no yes no no 154 d_release: no no no yes 155 d_iput: no no no yes 156 */ 157 158 /* d_flags entries */ 159 #define DCACHE_AUTOFS_PENDING 0x0001 /* autofs: "under construction" */ 160 #define DCACHE_NFSFS_RENAMED 0x0002 /* this dentry has been "silly 161 * renamed" and has to be 162 * deleted on the last dput() 163 */ 164 #define DCACHE_DISCONNECTED 0x0004 165 /* This dentry is possibly not currently connected to the dcache tree, 166 * in which case its parent will either be itself, or will have this 167 * flag as well. nfsd will not use a dentry with this bit set, but will 168 * first endeavour to clear the bit either by discovering that it is 169 * connected, or by performing lookup operations. Any filesystem which 170 * supports nfsd_operations MUST have a lookup function which, if it finds 171 * a directory inode with a DCACHE_DISCONNECTED dentry, will d_move 172 * that dentry into place and return that dentry rather than the passed one, 173 * typically using d_splice_alias. 174 */ 175 176 #define DCACHE_REFERENCED 0x0008 /* Recently used, don't discard. */ 177 #define DCACHE_UNHASHED 0x0010 178 179 #define DCACHE_INOTIFY_PARENT_WATCHED 0x0020 /* Parent inode is watched */ 180 181 extern spinlock_t dcache_lock; 182 extern seqlock_t rename_lock; 183 184 /** 185 * d_drop - drop a dentry 186 * @dentry: dentry to drop 187 * 188 * d_drop() unhashes the entry from the parent dentry hashes, so that it won't 189 * be found through a VFS lookup any more. Note that this is different from 190 * deleting the dentry - d_delete will try to mark the dentry negative if 191 * possible, giving a successful _negative_ lookup, while d_drop will 192 * just make the cache lookup fail. 193 * 194 * d_drop() is used mainly for stuff that wants to invalidate a dentry for some 195 * reason (NFS timeouts or autofs deletes). 196 * 197 * __d_drop requires dentry->d_lock. 198 */ 199 200 static inline void __d_drop(struct dentry *dentry) 201 { 202 if (!(dentry->d_flags & DCACHE_UNHASHED)) { 203 dentry->d_flags |= DCACHE_UNHASHED; 204 hlist_del_rcu(&dentry->d_hash); 205 } 206 } 207 208 static inline void d_drop(struct dentry *dentry) 209 { 210 spin_lock(&dcache_lock); 211 spin_lock(&dentry->d_lock); 212 __d_drop(dentry); 213 spin_unlock(&dentry->d_lock); 214 spin_unlock(&dcache_lock); 215 } 216 217 static inline int dname_external(struct dentry *dentry) 218 { 219 return dentry->d_name.name != dentry->d_iname; 220 } 221 222 /* 223 * These are the low-level FS interfaces to the dcache.. 224 */ 225 extern void d_instantiate(struct dentry *, struct inode *); 226 extern struct dentry * d_instantiate_unique(struct dentry *, struct inode *); 227 extern struct dentry * d_materialise_unique(struct dentry *, struct inode *); 228 extern void d_delete(struct dentry *); 229 230 /* allocate/de-allocate */ 231 extern struct dentry * d_alloc(struct dentry *, const struct qstr *); 232 extern struct dentry * d_alloc_anon(struct inode *); 233 extern struct dentry * d_splice_alias(struct inode *, struct dentry *); 234 extern void shrink_dcache_sb(struct super_block *); 235 extern void shrink_dcache_parent(struct dentry *); 236 extern void shrink_dcache_for_umount(struct super_block *); 237 extern int d_invalidate(struct dentry *); 238 239 /* only used at mount-time */ 240 extern struct dentry * d_alloc_root(struct inode *); 241 242 /* <clickety>-<click> the ramfs-type tree */ 243 extern void d_genocide(struct dentry *); 244 245 extern struct dentry *d_find_alias(struct inode *); 246 extern void d_prune_aliases(struct inode *); 247 248 /* test whether we have any submounts in a subdir tree */ 249 extern int have_submounts(struct dentry *); 250 251 /* 252 * This adds the entry to the hash queues. 253 */ 254 extern void d_rehash(struct dentry *); 255 256 /** 257 * d_add - add dentry to hash queues 258 * @entry: dentry to add 259 * @inode: The inode to attach to this dentry 260 * 261 * This adds the entry to the hash queues and initializes @inode. 262 * The entry was actually filled in earlier during d_alloc(). 263 */ 264 265 static inline void d_add(struct dentry *entry, struct inode *inode) 266 { 267 d_instantiate(entry, inode); 268 d_rehash(entry); 269 } 270 271 /** 272 * d_add_unique - add dentry to hash queues without aliasing 273 * @entry: dentry to add 274 * @inode: The inode to attach to this dentry 275 * 276 * This adds the entry to the hash queues and initializes @inode. 277 * The entry was actually filled in earlier during d_alloc(). 278 */ 279 static inline struct dentry *d_add_unique(struct dentry *entry, struct inode *inode) 280 { 281 struct dentry *res; 282 283 res = d_instantiate_unique(entry, inode); 284 d_rehash(res != NULL ? res : entry); 285 return res; 286 } 287 288 /* used for rename() and baskets */ 289 extern void d_move(struct dentry *, struct dentry *); 290 291 /* appendix may either be NULL or be used for transname suffixes */ 292 extern struct dentry * d_lookup(struct dentry *, struct qstr *); 293 extern struct dentry * __d_lookup(struct dentry *, struct qstr *); 294 extern struct dentry * d_hash_and_lookup(struct dentry *, struct qstr *); 295 296 /* validate "insecure" dentry pointer */ 297 extern int d_validate(struct dentry *, struct dentry *); 298 299 /* 300 * helper function for dentry_operations.d_dname() members 301 */ 302 extern char *dynamic_dname(struct dentry *, char *, int, const char *, ...); 303 304 extern char *d_path(struct path *, 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 vfsmount *__lookup_mnt(struct vfsmount *, struct dentry *, int); 363 extern struct dentry *lookup_create(struct nameidata *nd, int is_dir); 364 365 extern int sysctl_vfs_cache_pressure; 366 367 #endif /* __KERNEL__ */ 368 369 #endif /* __LINUX_DCACHE_H */ 370