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 struct dentry_operations { 118 int (*d_revalidate)(struct dentry *, struct nameidata *); 119 int (*d_hash) (struct dentry *, struct qstr *); 120 int (*d_compare) (struct dentry *, struct qstr *, struct qstr *); 121 int (*d_delete)(struct dentry *); 122 void (*d_release)(struct dentry *); 123 void (*d_iput)(struct dentry *, struct inode *); 124 }; 125 126 /* the dentry parameter passed to d_hash and d_compare is the parent 127 * directory of the entries to be compared. It is used in case these 128 * functions need any directory specific information for determining 129 * equivalency classes. Using the dentry itself might not work, as it 130 * might be a negative dentry which has no information associated with 131 * it */ 132 133 /* 134 locking rules: 135 big lock dcache_lock d_lock may block 136 d_revalidate: no no no yes 137 d_hash no no no yes 138 d_compare: no yes yes no 139 d_delete: no yes no no 140 d_release: no no no yes 141 d_iput: no no no yes 142 */ 143 144 /* d_flags entries */ 145 #define DCACHE_AUTOFS_PENDING 0x0001 /* autofs: "under construction" */ 146 #define DCACHE_NFSFS_RENAMED 0x0002 /* this dentry has been "silly 147 * renamed" and has to be 148 * deleted on the last dput() 149 */ 150 #define DCACHE_DISCONNECTED 0x0004 151 /* This dentry is possibly not currently connected to the dcache tree, 152 * in which case its parent will either be itself, or will have this 153 * flag as well. nfsd will not use a dentry with this bit set, but will 154 * first endeavour to clear the bit either by discovering that it is 155 * connected, or by performing lookup operations. Any filesystem which 156 * supports nfsd_operations MUST have a lookup function which, if it finds 157 * a directory inode with a DCACHE_DISCONNECTED dentry, will d_move 158 * that dentry into place and return that dentry rather than the passed one, 159 * typically using d_splice_alias. 160 */ 161 162 #define DCACHE_REFERENCED 0x0008 /* Recently used, don't discard. */ 163 #define DCACHE_UNHASHED 0x0010 164 165 #define DCACHE_INOTIFY_PARENT_WATCHED 0x0020 /* Parent inode is watched */ 166 167 extern spinlock_t dcache_lock; 168 169 /** 170 * d_drop - drop a dentry 171 * @dentry: dentry to drop 172 * 173 * d_drop() unhashes the entry from the parent dentry hashes, so that it won't 174 * be found through a VFS lookup any more. Note that this is different from 175 * deleting the dentry - d_delete will try to mark the dentry negative if 176 * possible, giving a successful _negative_ lookup, while d_drop will 177 * just make the cache lookup fail. 178 * 179 * d_drop() is used mainly for stuff that wants to invalidate a dentry for some 180 * reason (NFS timeouts or autofs deletes). 181 * 182 * __d_drop requires dentry->d_lock. 183 */ 184 185 static inline void __d_drop(struct dentry *dentry) 186 { 187 if (!(dentry->d_flags & DCACHE_UNHASHED)) { 188 dentry->d_flags |= DCACHE_UNHASHED; 189 hlist_del_rcu(&dentry->d_hash); 190 } 191 } 192 193 static inline void d_drop(struct dentry *dentry) 194 { 195 spin_lock(&dcache_lock); 196 spin_lock(&dentry->d_lock); 197 __d_drop(dentry); 198 spin_unlock(&dentry->d_lock); 199 spin_unlock(&dcache_lock); 200 } 201 202 static inline int dname_external(struct dentry *dentry) 203 { 204 return dentry->d_name.name != dentry->d_iname; 205 } 206 207 /* 208 * These are the low-level FS interfaces to the dcache.. 209 */ 210 extern void d_instantiate(struct dentry *, struct inode *); 211 extern struct dentry * d_instantiate_unique(struct dentry *, struct inode *); 212 extern void d_delete(struct dentry *); 213 214 /* allocate/de-allocate */ 215 extern struct dentry * d_alloc(struct dentry *, const struct qstr *); 216 extern struct dentry * d_alloc_anon(struct inode *); 217 extern struct dentry * d_splice_alias(struct inode *, struct dentry *); 218 extern void shrink_dcache_sb(struct super_block *); 219 extern void shrink_dcache_parent(struct dentry *); 220 extern void shrink_dcache_anon(struct hlist_head *); 221 extern int d_invalidate(struct dentry *); 222 223 /* only used at mount-time */ 224 extern struct dentry * d_alloc_root(struct inode *); 225 226 /* <clickety>-<click> the ramfs-type tree */ 227 extern void d_genocide(struct dentry *); 228 229 extern struct dentry *d_find_alias(struct inode *); 230 extern void d_prune_aliases(struct inode *); 231 232 /* test whether we have any submounts in a subdir tree */ 233 extern int have_submounts(struct dentry *); 234 235 /* 236 * This adds the entry to the hash queues. 237 */ 238 extern void d_rehash(struct dentry *); 239 240 /** 241 * d_add - add dentry to hash queues 242 * @entry: dentry to add 243 * @inode: The inode to attach to this dentry 244 * 245 * This adds the entry to the hash queues and initializes @inode. 246 * The entry was actually filled in earlier during d_alloc(). 247 */ 248 249 static inline void d_add(struct dentry *entry, struct inode *inode) 250 { 251 d_instantiate(entry, inode); 252 d_rehash(entry); 253 } 254 255 /** 256 * d_add_unique - add dentry to hash queues without aliasing 257 * @entry: dentry to add 258 * @inode: The inode to attach to this dentry 259 * 260 * This adds the entry to the hash queues and initializes @inode. 261 * The entry was actually filled in earlier during d_alloc(). 262 */ 263 static inline struct dentry *d_add_unique(struct dentry *entry, struct inode *inode) 264 { 265 struct dentry *res; 266 267 res = d_instantiate_unique(entry, inode); 268 d_rehash(res != NULL ? res : entry); 269 return res; 270 } 271 272 /* used for rename() and baskets */ 273 extern void d_move(struct dentry *, struct dentry *); 274 275 /* appendix may either be NULL or be used for transname suffixes */ 276 extern struct dentry * d_lookup(struct dentry *, struct qstr *); 277 extern struct dentry * __d_lookup(struct dentry *, struct qstr *); 278 279 /* validate "insecure" dentry pointer */ 280 extern int d_validate(struct dentry *, struct dentry *); 281 282 extern char * d_path(struct dentry *, struct vfsmount *, char *, int); 283 284 /* Allocation counts.. */ 285 286 /** 287 * dget, dget_locked - get a reference to a dentry 288 * @dentry: dentry to get a reference to 289 * 290 * Given a dentry or %NULL pointer increment the reference count 291 * if appropriate and return the dentry. A dentry will not be 292 * destroyed when it has references. dget() should never be 293 * called for dentries with zero reference counter. For these cases 294 * (preferably none, functions in dcache.c are sufficient for normal 295 * needs and they take necessary precautions) you should hold dcache_lock 296 * and call dget_locked() instead of dget(). 297 */ 298 299 static inline struct dentry *dget(struct dentry *dentry) 300 { 301 if (dentry) { 302 BUG_ON(!atomic_read(&dentry->d_count)); 303 atomic_inc(&dentry->d_count); 304 } 305 return dentry; 306 } 307 308 extern struct dentry * dget_locked(struct dentry *); 309 310 /** 311 * d_unhashed - is dentry hashed 312 * @dentry: entry to check 313 * 314 * Returns true if the dentry passed is not currently hashed. 315 */ 316 317 static inline int d_unhashed(struct dentry *dentry) 318 { 319 return (dentry->d_flags & DCACHE_UNHASHED); 320 } 321 322 static inline struct dentry *dget_parent(struct dentry *dentry) 323 { 324 struct dentry *ret; 325 326 spin_lock(&dentry->d_lock); 327 ret = dget(dentry->d_parent); 328 spin_unlock(&dentry->d_lock); 329 return ret; 330 } 331 332 extern void dput(struct dentry *); 333 334 static inline int d_mountpoint(struct dentry *dentry) 335 { 336 return dentry->d_mounted; 337 } 338 339 extern struct vfsmount *lookup_mnt(struct vfsmount *, struct dentry *); 340 extern struct vfsmount *__lookup_mnt(struct vfsmount *, struct dentry *, int); 341 extern struct dentry *lookup_create(struct nameidata *nd, int is_dir); 342 343 extern int sysctl_vfs_cache_pressure; 344 345 #endif /* __KERNEL__ */ 346 347 #endif /* __LINUX_DCACHE_H */ 348