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 extern spinlock_t dcache_lock; 166 167 /** 168 * d_drop - drop a dentry 169 * @dentry: dentry to drop 170 * 171 * d_drop() unhashes the entry from the parent dentry hashes, so that it won't 172 * be found through a VFS lookup any more. Note that this is different from 173 * deleting the dentry - d_delete will try to mark the dentry negative if 174 * possible, giving a successful _negative_ lookup, while d_drop will 175 * just make the cache lookup fail. 176 * 177 * d_drop() is used mainly for stuff that wants to invalidate a dentry for some 178 * reason (NFS timeouts or autofs deletes). 179 * 180 * __d_drop requires dentry->d_lock. 181 */ 182 183 static inline void __d_drop(struct dentry *dentry) 184 { 185 if (!(dentry->d_flags & DCACHE_UNHASHED)) { 186 dentry->d_flags |= DCACHE_UNHASHED; 187 hlist_del_rcu(&dentry->d_hash); 188 } 189 } 190 191 static inline void d_drop(struct dentry *dentry) 192 { 193 spin_lock(&dcache_lock); 194 spin_lock(&dentry->d_lock); 195 __d_drop(dentry); 196 spin_unlock(&dentry->d_lock); 197 spin_unlock(&dcache_lock); 198 } 199 200 static inline int dname_external(struct dentry *dentry) 201 { 202 return dentry->d_name.name != dentry->d_iname; 203 } 204 205 /* 206 * These are the low-level FS interfaces to the dcache.. 207 */ 208 extern void d_instantiate(struct dentry *, struct inode *); 209 extern struct dentry * d_instantiate_unique(struct dentry *, struct inode *); 210 extern void d_delete(struct dentry *); 211 212 /* allocate/de-allocate */ 213 extern struct dentry * d_alloc(struct dentry *, const struct qstr *); 214 extern struct dentry * d_alloc_anon(struct inode *); 215 extern struct dentry * d_splice_alias(struct inode *, struct dentry *); 216 extern void shrink_dcache_sb(struct super_block *); 217 extern void shrink_dcache_parent(struct dentry *); 218 extern void shrink_dcache_anon(struct hlist_head *); 219 extern int d_invalidate(struct dentry *); 220 221 /* only used at mount-time */ 222 extern struct dentry * d_alloc_root(struct inode *); 223 224 /* <clickety>-<click> the ramfs-type tree */ 225 extern void d_genocide(struct dentry *); 226 227 extern struct dentry *d_find_alias(struct inode *); 228 extern void d_prune_aliases(struct inode *); 229 230 /* test whether we have any submounts in a subdir tree */ 231 extern int have_submounts(struct dentry *); 232 233 /* 234 * This adds the entry to the hash queues. 235 */ 236 extern void d_rehash(struct dentry *); 237 238 /** 239 * d_add - add dentry to hash queues 240 * @entry: dentry to add 241 * @inode: The inode to attach to this dentry 242 * 243 * This adds the entry to the hash queues and initializes @inode. 244 * The entry was actually filled in earlier during d_alloc(). 245 */ 246 247 static inline void d_add(struct dentry *entry, struct inode *inode) 248 { 249 d_instantiate(entry, inode); 250 d_rehash(entry); 251 } 252 253 /** 254 * d_add_unique - add dentry to hash queues without aliasing 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 static inline struct dentry *d_add_unique(struct dentry *entry, struct inode *inode) 262 { 263 struct dentry *res; 264 265 res = d_instantiate_unique(entry, inode); 266 d_rehash(res != NULL ? res : entry); 267 return res; 268 } 269 270 /* used for rename() and baskets */ 271 extern void d_move(struct dentry *, struct dentry *); 272 273 /* appendix may either be NULL or be used for transname suffixes */ 274 extern struct dentry * d_lookup(struct dentry *, struct qstr *); 275 extern struct dentry * __d_lookup(struct dentry *, struct qstr *); 276 277 /* validate "insecure" dentry pointer */ 278 extern int d_validate(struct dentry *, struct dentry *); 279 280 extern char * d_path(struct dentry *, struct vfsmount *, char *, int); 281 282 /* Allocation counts.. */ 283 284 /** 285 * dget, dget_locked - get a reference to a dentry 286 * @dentry: dentry to get a reference to 287 * 288 * Given a dentry or %NULL pointer increment the reference count 289 * if appropriate and return the dentry. A dentry will not be 290 * destroyed when it has references. dget() should never be 291 * called for dentries with zero reference counter. For these cases 292 * (preferably none, functions in dcache.c are sufficient for normal 293 * needs and they take necessary precautions) you should hold dcache_lock 294 * and call dget_locked() instead of dget(). 295 */ 296 297 static inline struct dentry *dget(struct dentry *dentry) 298 { 299 if (dentry) { 300 BUG_ON(!atomic_read(&dentry->d_count)); 301 atomic_inc(&dentry->d_count); 302 } 303 return dentry; 304 } 305 306 extern struct dentry * dget_locked(struct dentry *); 307 308 /** 309 * d_unhashed - is dentry hashed 310 * @dentry: entry to check 311 * 312 * Returns true if the dentry passed is not currently hashed. 313 */ 314 315 static inline int d_unhashed(struct dentry *dentry) 316 { 317 return (dentry->d_flags & DCACHE_UNHASHED); 318 } 319 320 static inline struct dentry *dget_parent(struct dentry *dentry) 321 { 322 struct dentry *ret; 323 324 spin_lock(&dentry->d_lock); 325 ret = dget(dentry->d_parent); 326 spin_unlock(&dentry->d_lock); 327 return ret; 328 } 329 330 extern void dput(struct dentry *); 331 332 static inline int d_mountpoint(struct dentry *dentry) 333 { 334 return dentry->d_mounted; 335 } 336 337 extern struct vfsmount *lookup_mnt(struct vfsmount *, struct dentry *); 338 extern struct vfsmount *__lookup_mnt(struct vfsmount *, struct dentry *, int); 339 extern struct dentry *lookup_create(struct nameidata *nd, int is_dir); 340 341 extern int sysctl_vfs_cache_pressure; 342 343 #endif /* __KERNEL__ */ 344 345 #endif /* __LINUX_DCACHE_H */ 346