1 #ifndef __LINUX_DCACHE_H 2 #define __LINUX_DCACHE_H 3 4 #include <asm/atomic.h> 5 #include <linux/list.h> 6 #include <linux/rculist.h> 7 #include <linux/rculist_bl.h> 8 #include <linux/spinlock.h> 9 #include <linux/seqlock.h> 10 #include <linux/cache.h> 11 #include <linux/rcupdate.h> 12 13 struct nameidata; 14 struct path; 15 struct vfsmount; 16 17 /* 18 * linux/include/linux/dcache.h 19 * 20 * Dirent cache data structures 21 * 22 * (C) Copyright 1997 Thomas Schoebel-Theuer, 23 * with heavy changes by Linus Torvalds 24 */ 25 26 #define IS_ROOT(x) ((x) == (x)->d_parent) 27 28 /* 29 * "quick string" -- eases parameter passing, but more importantly 30 * saves "metadata" about the string (ie length and the hash). 31 * 32 * hash comes first so it snuggles against d_parent in the 33 * dentry. 34 */ 35 struct qstr { 36 unsigned int hash; 37 unsigned int len; 38 const unsigned char *name; 39 }; 40 41 struct dentry_stat_t { 42 int nr_dentry; 43 int nr_unused; 44 int age_limit; /* age in seconds */ 45 int want_pages; /* pages requested by system */ 46 int dummy[2]; 47 }; 48 extern struct dentry_stat_t dentry_stat; 49 50 /* 51 * Compare 2 name strings, return 0 if they match, otherwise non-zero. 52 * The strings are both count bytes long, and count is non-zero. 53 */ 54 static inline int dentry_cmp(const unsigned char *cs, size_t scount, 55 const unsigned char *ct, size_t tcount) 56 { 57 int ret; 58 if (scount != tcount) 59 return 1; 60 do { 61 ret = (*cs != *ct); 62 if (ret) 63 break; 64 cs++; 65 ct++; 66 tcount--; 67 } while (tcount); 68 return ret; 69 } 70 71 /* Name hashing routines. Initial hash value */ 72 /* Hash courtesy of the R5 hash in reiserfs modulo sign bits */ 73 #define init_name_hash() 0 74 75 /* partial hash update function. Assume roughly 4 bits per character */ 76 static inline unsigned long 77 partial_name_hash(unsigned long c, unsigned long prevhash) 78 { 79 return (prevhash + (c << 4) + (c >> 4)) * 11; 80 } 81 82 /* 83 * Finally: cut down the number of bits to a int value (and try to avoid 84 * losing bits) 85 */ 86 static inline unsigned long end_name_hash(unsigned long hash) 87 { 88 return (unsigned int) hash; 89 } 90 91 /* Compute the hash for a name string. */ 92 static inline unsigned int 93 full_name_hash(const unsigned char *name, unsigned int len) 94 { 95 unsigned long hash = init_name_hash(); 96 while (len--) 97 hash = partial_name_hash(*name++, hash); 98 return end_name_hash(hash); 99 } 100 101 /* 102 * Try to keep struct dentry aligned on 64 byte cachelines (this will 103 * give reasonable cacheline footprint with larger lines without the 104 * large memory footprint increase). 105 */ 106 #ifdef CONFIG_64BIT 107 # define DNAME_INLINE_LEN 32 /* 192 bytes */ 108 #else 109 # ifdef CONFIG_SMP 110 # define DNAME_INLINE_LEN 36 /* 128 bytes */ 111 # else 112 # define DNAME_INLINE_LEN 40 /* 128 bytes */ 113 # endif 114 #endif 115 116 struct dentry { 117 /* RCU lookup touched fields */ 118 unsigned int d_flags; /* protected by d_lock */ 119 seqcount_t d_seq; /* per dentry seqlock */ 120 struct hlist_bl_node d_hash; /* lookup hash list */ 121 struct dentry *d_parent; /* parent directory */ 122 struct qstr d_name; 123 struct inode *d_inode; /* Where the name belongs to - NULL is 124 * negative */ 125 unsigned char d_iname[DNAME_INLINE_LEN]; /* small names */ 126 127 /* Ref lookup also touches following */ 128 unsigned int d_count; /* protected by d_lock */ 129 spinlock_t d_lock; /* per dentry lock */ 130 const struct dentry_operations *d_op; 131 struct super_block *d_sb; /* The root of the dentry tree */ 132 unsigned long d_time; /* used by d_revalidate */ 133 void *d_fsdata; /* fs-specific data */ 134 135 struct list_head d_lru; /* LRU list */ 136 /* 137 * d_child and d_rcu can share memory 138 */ 139 union { 140 struct list_head d_child; /* child of parent list */ 141 struct rcu_head d_rcu; 142 } d_u; 143 struct list_head d_subdirs; /* our children */ 144 struct list_head d_alias; /* inode alias list */ 145 }; 146 147 /* 148 * dentry->d_lock spinlock nesting subclasses: 149 * 150 * 0: normal 151 * 1: nested 152 */ 153 enum dentry_d_lock_class 154 { 155 DENTRY_D_LOCK_NORMAL, /* implicitly used by plain spin_lock() APIs. */ 156 DENTRY_D_LOCK_NESTED 157 }; 158 159 struct dentry_operations { 160 int (*d_revalidate)(struct dentry *, struct nameidata *); 161 int (*d_hash)(const struct dentry *, const struct inode *, 162 struct qstr *); 163 int (*d_compare)(const struct dentry *, const struct inode *, 164 const struct dentry *, const struct inode *, 165 unsigned int, const char *, const struct qstr *); 166 int (*d_delete)(const struct dentry *); 167 void (*d_release)(struct dentry *); 168 void (*d_iput)(struct dentry *, struct inode *); 169 char *(*d_dname)(struct dentry *, char *, int); 170 } ____cacheline_aligned; 171 172 /* 173 * Locking rules for dentry_operations callbacks are to be found in 174 * Documentation/filesystems/Locking. Keep it updated! 175 * 176 * FUrther descriptions are found in Documentation/filesystems/vfs.txt. 177 * Keep it updated too! 178 */ 179 180 /* d_flags entries */ 181 #define DCACHE_AUTOFS_PENDING 0x0001 /* autofs: "under construction" */ 182 #define DCACHE_NFSFS_RENAMED 0x0002 183 /* this dentry has been "silly renamed" and has to be deleted on the last 184 * dput() */ 185 186 #define DCACHE_DISCONNECTED 0x0004 187 /* This dentry is possibly not currently connected to the dcache tree, in 188 * which case its parent will either be itself, or will have this flag as 189 * well. nfsd will not use a dentry with this bit set, but will first 190 * endeavour to clear the bit either by discovering that it is connected, 191 * or by performing lookup operations. Any filesystem which supports 192 * nfsd_operations MUST have a lookup function which, if it finds a 193 * directory inode with a DCACHE_DISCONNECTED dentry, will d_move that 194 * dentry into place and return that dentry rather than the passed one, 195 * typically using d_splice_alias. */ 196 197 #define DCACHE_REFERENCED 0x0008 /* Recently used, don't discard. */ 198 #define DCACHE_UNHASHED 0x0010 199 #define DCACHE_INOTIFY_PARENT_WATCHED 0x0020 200 /* Parent inode is watched by inotify */ 201 202 #define DCACHE_COOKIE 0x0040 /* For use by dcookie subsystem */ 203 #define DCACHE_FSNOTIFY_PARENT_WATCHED 0x0080 204 /* Parent inode is watched by some fsnotify listener */ 205 206 #define DCACHE_CANT_MOUNT 0x0100 207 #define DCACHE_GENOCIDE 0x0200 208 #define DCACHE_MOUNTED 0x0400 /* is a mountpoint */ 209 210 #define DCACHE_OP_HASH 0x1000 211 #define DCACHE_OP_COMPARE 0x2000 212 #define DCACHE_OP_REVALIDATE 0x4000 213 #define DCACHE_OP_DELETE 0x8000 214 215 extern seqlock_t rename_lock; 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_drop(struct dentry *dentry); 229 extern void d_drop(struct dentry *dentry); 230 extern void d_delete(struct dentry *); 231 extern void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op); 232 233 /* allocate/de-allocate */ 234 extern struct dentry * d_alloc(struct dentry *, const struct qstr *); 235 extern struct dentry * d_alloc_pseudo(struct super_block *, const struct qstr *); 236 extern struct dentry * d_splice_alias(struct inode *, struct dentry *); 237 extern struct dentry * d_add_ci(struct dentry *, struct inode *, struct qstr *); 238 extern struct dentry * d_obtain_alias(struct inode *); 239 extern void shrink_dcache_sb(struct super_block *); 240 extern void shrink_dcache_parent(struct dentry *); 241 extern void shrink_dcache_for_umount(struct super_block *); 242 extern int d_invalidate(struct dentry *); 243 244 /* only used at mount-time */ 245 extern struct dentry * d_alloc_root(struct inode *); 246 247 /* <clickety>-<click> the ramfs-type tree */ 248 extern void d_genocide(struct dentry *); 249 250 extern struct dentry *d_find_alias(struct inode *); 251 extern void d_prune_aliases(struct inode *); 252 253 /* test whether we have any submounts in a subdir tree */ 254 extern int have_submounts(struct dentry *); 255 256 /* 257 * This adds the entry to the hash queues. 258 */ 259 extern void d_rehash(struct dentry *); 260 261 /** 262 * d_add - add dentry to hash queues 263 * @entry: dentry to add 264 * @inode: The inode to attach to this dentry 265 * 266 * This adds the entry to the hash queues and initializes @inode. 267 * The entry was actually filled in earlier during d_alloc(). 268 */ 269 270 static inline void d_add(struct dentry *entry, struct inode *inode) 271 { 272 d_instantiate(entry, inode); 273 d_rehash(entry); 274 } 275 276 /** 277 * d_add_unique - add dentry to hash queues without aliasing 278 * @entry: dentry to add 279 * @inode: The inode to attach to this dentry 280 * 281 * This adds the entry to the hash queues and initializes @inode. 282 * The entry was actually filled in earlier during d_alloc(). 283 */ 284 static inline struct dentry *d_add_unique(struct dentry *entry, struct inode *inode) 285 { 286 struct dentry *res; 287 288 res = d_instantiate_unique(entry, inode); 289 d_rehash(res != NULL ? res : entry); 290 return res; 291 } 292 293 extern void dentry_update_name_case(struct dentry *, struct qstr *); 294 295 /* used for rename() and baskets */ 296 extern void d_move(struct dentry *, struct dentry *); 297 extern struct dentry *d_ancestor(struct dentry *, struct dentry *); 298 299 /* appendix may either be NULL or be used for transname suffixes */ 300 extern struct dentry *d_lookup(struct dentry *, struct qstr *); 301 extern struct dentry *d_hash_and_lookup(struct dentry *, struct qstr *); 302 extern struct dentry *__d_lookup(struct dentry *, struct qstr *); 303 extern struct dentry *__d_lookup_rcu(struct dentry *parent, struct qstr *name, 304 unsigned *seq, struct inode **inode); 305 306 /** 307 * __d_rcu_to_refcount - take a refcount on dentry if sequence check is ok 308 * @dentry: dentry to take a ref on 309 * @seq: seqcount to verify against 310 * @Returns: 0 on failure, else 1. 311 * 312 * __d_rcu_to_refcount operates on a dentry,seq pair that was returned 313 * by __d_lookup_rcu, to get a reference on an rcu-walk dentry. 314 */ 315 static inline int __d_rcu_to_refcount(struct dentry *dentry, unsigned seq) 316 { 317 int ret = 0; 318 319 assert_spin_locked(&dentry->d_lock); 320 if (!read_seqcount_retry(&dentry->d_seq, seq)) { 321 ret = 1; 322 dentry->d_count++; 323 } 324 325 return ret; 326 } 327 328 /* validate "insecure" dentry pointer */ 329 extern int d_validate(struct dentry *, struct dentry *); 330 331 /* 332 * helper function for dentry_operations.d_dname() members 333 */ 334 extern char *dynamic_dname(struct dentry *, char *, int, const char *, ...); 335 336 extern char *__d_path(const struct path *path, struct path *root, char *, int); 337 extern char *d_path(const struct path *, char *, int); 338 extern char *d_path_with_unreachable(const struct path *, char *, int); 339 extern char *dentry_path_raw(struct dentry *, char *, int); 340 extern char *dentry_path(struct dentry *, char *, int); 341 342 /* Allocation counts.. */ 343 344 /** 345 * dget, dget_dlock - get a reference to a dentry 346 * @dentry: dentry to get a reference to 347 * 348 * Given a dentry or %NULL pointer increment the reference count 349 * if appropriate and return the dentry. A dentry will not be 350 * destroyed when it has references. 351 */ 352 static inline struct dentry *dget_dlock(struct dentry *dentry) 353 { 354 if (dentry) 355 dentry->d_count++; 356 return dentry; 357 } 358 359 static inline struct dentry *dget(struct dentry *dentry) 360 { 361 if (dentry) { 362 spin_lock(&dentry->d_lock); 363 dget_dlock(dentry); 364 spin_unlock(&dentry->d_lock); 365 } 366 return dentry; 367 } 368 369 extern struct dentry *dget_parent(struct dentry *dentry); 370 371 /** 372 * d_unhashed - is dentry hashed 373 * @dentry: entry to check 374 * 375 * Returns true if the dentry passed is not currently hashed. 376 */ 377 378 static inline int d_unhashed(struct dentry *dentry) 379 { 380 return (dentry->d_flags & DCACHE_UNHASHED); 381 } 382 383 static inline int d_unlinked(struct dentry *dentry) 384 { 385 return d_unhashed(dentry) && !IS_ROOT(dentry); 386 } 387 388 static inline int cant_mount(struct dentry *dentry) 389 { 390 return (dentry->d_flags & DCACHE_CANT_MOUNT); 391 } 392 393 static inline void dont_mount(struct dentry *dentry) 394 { 395 spin_lock(&dentry->d_lock); 396 dentry->d_flags |= DCACHE_CANT_MOUNT; 397 spin_unlock(&dentry->d_lock); 398 } 399 400 extern void dput(struct dentry *); 401 402 static inline int d_mountpoint(struct dentry *dentry) 403 { 404 return dentry->d_flags & DCACHE_MOUNTED; 405 } 406 407 extern struct vfsmount *lookup_mnt(struct path *); 408 extern struct dentry *lookup_create(struct nameidata *nd, int is_dir); 409 410 extern int sysctl_vfs_cache_pressure; 411 412 #endif /* __LINUX_DCACHE_H */ 413