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 #include <asm/bug.h> 12 13 struct nameidata; 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 16-byte range, with 16-byte alignment. 92 */ 93 struct dentry *d_parent; /* parent directory */ 94 struct qstr d_name; 95 96 struct list_head d_lru; /* LRU list */ 97 struct list_head d_child; /* child of parent list */ 98 struct list_head d_subdirs; /* our children */ 99 struct list_head d_alias; /* inode alias list */ 100 unsigned long d_time; /* used by d_revalidate */ 101 struct dentry_operations *d_op; 102 struct super_block *d_sb; /* The root of the dentry tree */ 103 void *d_fsdata; /* fs-specific data */ 104 struct rcu_head d_rcu; 105 struct dcookie_struct *d_cookie; /* cookie, if any */ 106 struct hlist_node d_hash; /* lookup hash list */ 107 int d_mounted; 108 unsigned char d_iname[DNAME_INLINE_LEN_MIN]; /* small names */ 109 }; 110 111 struct dentry_operations { 112 int (*d_revalidate)(struct dentry *, struct nameidata *); 113 int (*d_hash) (struct dentry *, struct qstr *); 114 int (*d_compare) (struct dentry *, struct qstr *, struct qstr *); 115 int (*d_delete)(struct dentry *); 116 void (*d_release)(struct dentry *); 117 void (*d_iput)(struct dentry *, struct inode *); 118 }; 119 120 /* the dentry parameter passed to d_hash and d_compare is the parent 121 * directory of the entries to be compared. It is used in case these 122 * functions need any directory specific information for determining 123 * equivalency classes. Using the dentry itself might not work, as it 124 * might be a negative dentry which has no information associated with 125 * it */ 126 127 /* 128 locking rules: 129 big lock dcache_lock d_lock may block 130 d_revalidate: no no no yes 131 d_hash no no no yes 132 d_compare: no yes yes no 133 d_delete: no yes no no 134 d_release: no no no yes 135 d_iput: no no no yes 136 */ 137 138 /* d_flags entries */ 139 #define DCACHE_AUTOFS_PENDING 0x0001 /* autofs: "under construction" */ 140 #define DCACHE_NFSFS_RENAMED 0x0002 /* this dentry has been "silly 141 * renamed" and has to be 142 * deleted on the last dput() 143 */ 144 #define DCACHE_DISCONNECTED 0x0004 145 /* This dentry is possibly not currently connected to the dcache tree, 146 * in which case its parent will either be itself, or will have this 147 * flag as well. nfsd will not use a dentry with this bit set, but will 148 * first endeavour to clear the bit either by discovering that it is 149 * connected, or by performing lookup operations. Any filesystem which 150 * supports nfsd_operations MUST have a lookup function which, if it finds 151 * a directory inode with a DCACHE_DISCONNECTED dentry, will d_move 152 * that dentry into place and return that dentry rather than the passed one, 153 * typically using d_splice_alias. 154 */ 155 156 #define DCACHE_REFERENCED 0x0008 /* Recently used, don't discard. */ 157 #define DCACHE_UNHASHED 0x0010 158 159 extern spinlock_t dcache_lock; 160 161 /** 162 * d_drop - drop a dentry 163 * @dentry: dentry to drop 164 * 165 * d_drop() unhashes the entry from the parent dentry hashes, so that it won't 166 * be found through a VFS lookup any more. Note that this is different from 167 * deleting the dentry - d_delete will try to mark the dentry negative if 168 * possible, giving a successful _negative_ lookup, while d_drop will 169 * just make the cache lookup fail. 170 * 171 * d_drop() is used mainly for stuff that wants to invalidate a dentry for some 172 * reason (NFS timeouts or autofs deletes). 173 * 174 * __d_drop requires dentry->d_lock. 175 */ 176 177 static inline void __d_drop(struct dentry *dentry) 178 { 179 if (!(dentry->d_flags & DCACHE_UNHASHED)) { 180 dentry->d_flags |= DCACHE_UNHASHED; 181 hlist_del_rcu(&dentry->d_hash); 182 } 183 } 184 185 static inline void d_drop(struct dentry *dentry) 186 { 187 spin_lock(&dcache_lock); 188 spin_lock(&dentry->d_lock); 189 __d_drop(dentry); 190 spin_unlock(&dentry->d_lock); 191 spin_unlock(&dcache_lock); 192 } 193 194 static inline int dname_external(struct dentry *dentry) 195 { 196 return dentry->d_name.name != dentry->d_iname; 197 } 198 199 /* 200 * These are the low-level FS interfaces to the dcache.. 201 */ 202 extern void d_instantiate(struct dentry *, struct inode *); 203 extern struct dentry * d_instantiate_unique(struct dentry *, struct inode *); 204 extern void d_delete(struct dentry *); 205 206 /* allocate/de-allocate */ 207 extern struct dentry * d_alloc(struct dentry *, const struct qstr *); 208 extern struct dentry * d_alloc_anon(struct inode *); 209 extern struct dentry * d_splice_alias(struct inode *, struct dentry *); 210 extern void shrink_dcache_sb(struct super_block *); 211 extern void shrink_dcache_parent(struct dentry *); 212 extern void shrink_dcache_anon(struct hlist_head *); 213 extern int d_invalidate(struct dentry *); 214 215 /* only used at mount-time */ 216 extern struct dentry * d_alloc_root(struct inode *); 217 218 /* <clickety>-<click> the ramfs-type tree */ 219 extern void d_genocide(struct dentry *); 220 221 extern struct dentry *d_find_alias(struct inode *); 222 extern void d_prune_aliases(struct inode *); 223 224 /* test whether we have any submounts in a subdir tree */ 225 extern int have_submounts(struct dentry *); 226 227 /* 228 * This adds the entry to the hash queues. 229 */ 230 extern void d_rehash(struct dentry *); 231 232 /** 233 * d_add - add dentry to hash queues 234 * @entry: dentry to add 235 * @inode: The inode to attach to this dentry 236 * 237 * This adds the entry to the hash queues and initializes @inode. 238 * The entry was actually filled in earlier during d_alloc(). 239 */ 240 241 static inline void d_add(struct dentry *entry, struct inode *inode) 242 { 243 d_instantiate(entry, inode); 244 d_rehash(entry); 245 } 246 247 /** 248 * d_add_unique - add dentry to hash queues without aliasing 249 * @entry: dentry to add 250 * @inode: The inode to attach to this dentry 251 * 252 * This adds the entry to the hash queues and initializes @inode. 253 * The entry was actually filled in earlier during d_alloc(). 254 */ 255 static inline struct dentry *d_add_unique(struct dentry *entry, struct inode *inode) 256 { 257 struct dentry *res; 258 259 res = d_instantiate_unique(entry, inode); 260 d_rehash(res != NULL ? res : entry); 261 return res; 262 } 263 264 /* used for rename() and baskets */ 265 extern void d_move(struct dentry *, struct dentry *); 266 267 /* appendix may either be NULL or be used for transname suffixes */ 268 extern struct dentry * d_lookup(struct dentry *, struct qstr *); 269 extern struct dentry * __d_lookup(struct dentry *, struct qstr *); 270 271 /* validate "insecure" dentry pointer */ 272 extern int d_validate(struct dentry *, struct dentry *); 273 274 extern char * d_path(struct dentry *, struct vfsmount *, char *, int); 275 276 /* Allocation counts.. */ 277 278 /** 279 * dget, dget_locked - get a reference to a dentry 280 * @dentry: dentry to get a reference to 281 * 282 * Given a dentry or %NULL pointer increment the reference count 283 * if appropriate and return the dentry. A dentry will not be 284 * destroyed when it has references. dget() should never be 285 * called for dentries with zero reference counter. For these cases 286 * (preferably none, functions in dcache.c are sufficient for normal 287 * needs and they take necessary precautions) you should hold dcache_lock 288 * and call dget_locked() instead of dget(). 289 */ 290 291 static inline struct dentry *dget(struct dentry *dentry) 292 { 293 if (dentry) { 294 BUG_ON(!atomic_read(&dentry->d_count)); 295 atomic_inc(&dentry->d_count); 296 } 297 return dentry; 298 } 299 300 extern struct dentry * dget_locked(struct dentry *); 301 302 /** 303 * d_unhashed - is dentry hashed 304 * @dentry: entry to check 305 * 306 * Returns true if the dentry passed is not currently hashed. 307 */ 308 309 static inline int d_unhashed(struct dentry *dentry) 310 { 311 return (dentry->d_flags & DCACHE_UNHASHED); 312 } 313 314 static inline struct dentry *dget_parent(struct dentry *dentry) 315 { 316 struct dentry *ret; 317 318 spin_lock(&dentry->d_lock); 319 ret = dget(dentry->d_parent); 320 spin_unlock(&dentry->d_lock); 321 return ret; 322 } 323 324 extern void dput(struct dentry *); 325 326 static inline int d_mountpoint(struct dentry *dentry) 327 { 328 return dentry->d_mounted; 329 } 330 331 extern struct vfsmount *lookup_mnt(struct vfsmount *, struct dentry *); 332 extern struct dentry *lookup_create(struct nameidata *nd, int is_dir); 333 334 extern int sysctl_vfs_cache_pressure; 335 336 #endif /* __KERNEL__ */ 337 338 #endif /* __LINUX_DCACHE_H */ 339