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 struct vfsmount *(*d_automount)(struct path *); 171 int (*d_manage)(struct dentry *, bool); 172 } ____cacheline_aligned; 173 174 /* 175 * Locking rules for dentry_operations callbacks are to be found in 176 * Documentation/filesystems/Locking. Keep it updated! 177 * 178 * FUrther descriptions are found in Documentation/filesystems/vfs.txt. 179 * Keep it updated too! 180 */ 181 182 /* d_flags entries */ 183 #define DCACHE_AUTOFS_PENDING 0x0001 /* autofs: "under construction" */ 184 #define DCACHE_NFSFS_RENAMED 0x0002 185 /* this dentry has been "silly renamed" and has to be deleted on the last 186 * dput() */ 187 188 #define DCACHE_DISCONNECTED 0x0004 189 /* This dentry is possibly not currently connected to the dcache tree, in 190 * which case its parent will either be itself, or will have this flag as 191 * well. nfsd will not use a dentry with this bit set, but will first 192 * endeavour to clear the bit either by discovering that it is connected, 193 * or by performing lookup operations. Any filesystem which supports 194 * nfsd_operations MUST have a lookup function which, if it finds a 195 * directory inode with a DCACHE_DISCONNECTED dentry, will d_move that 196 * dentry into place and return that dentry rather than the passed one, 197 * typically using d_splice_alias. */ 198 199 #define DCACHE_REFERENCED 0x0008 /* Recently used, don't discard. */ 200 #define DCACHE_UNHASHED 0x0010 201 #define DCACHE_INOTIFY_PARENT_WATCHED 0x0020 202 /* Parent inode is watched by inotify */ 203 204 #define DCACHE_COOKIE 0x0040 /* For use by dcookie subsystem */ 205 #define DCACHE_FSNOTIFY_PARENT_WATCHED 0x0080 206 /* Parent inode is watched by some fsnotify listener */ 207 208 #define DCACHE_CANT_MOUNT 0x0100 209 #define DCACHE_GENOCIDE 0x0200 210 211 #define DCACHE_OP_HASH 0x1000 212 #define DCACHE_OP_COMPARE 0x2000 213 #define DCACHE_OP_REVALIDATE 0x4000 214 #define DCACHE_OP_DELETE 0x8000 215 216 #define DCACHE_MOUNTED 0x10000 /* is a mountpoint */ 217 #define DCACHE_NEED_AUTOMOUNT 0x20000 /* handle automount on this dir */ 218 #define DCACHE_MANAGE_TRANSIT 0x40000 /* manage transit from this dirent */ 219 #define DCACHE_MANAGED_DENTRY \ 220 (DCACHE_MOUNTED|DCACHE_NEED_AUTOMOUNT|DCACHE_MANAGE_TRANSIT) 221 222 extern seqlock_t rename_lock; 223 224 static inline int dname_external(struct dentry *dentry) 225 { 226 return dentry->d_name.name != dentry->d_iname; 227 } 228 229 /* 230 * These are the low-level FS interfaces to the dcache.. 231 */ 232 extern void d_instantiate(struct dentry *, struct inode *); 233 extern struct dentry * d_instantiate_unique(struct dentry *, struct inode *); 234 extern struct dentry * d_materialise_unique(struct dentry *, struct inode *); 235 extern void __d_drop(struct dentry *dentry); 236 extern void d_drop(struct dentry *dentry); 237 extern void d_delete(struct dentry *); 238 extern void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op); 239 240 /* allocate/de-allocate */ 241 extern struct dentry * d_alloc(struct dentry *, const struct qstr *); 242 extern struct dentry * d_alloc_pseudo(struct super_block *, const struct qstr *); 243 extern struct dentry * d_splice_alias(struct inode *, struct dentry *); 244 extern struct dentry * d_add_ci(struct dentry *, struct inode *, struct qstr *); 245 extern struct dentry * d_obtain_alias(struct inode *); 246 extern void shrink_dcache_sb(struct super_block *); 247 extern void shrink_dcache_parent(struct dentry *); 248 extern void shrink_dcache_for_umount(struct super_block *); 249 extern int d_invalidate(struct dentry *); 250 251 /* only used at mount-time */ 252 extern struct dentry * d_alloc_root(struct inode *); 253 254 /* <clickety>-<click> the ramfs-type tree */ 255 extern void d_genocide(struct dentry *); 256 257 extern struct dentry *d_find_alias(struct inode *); 258 extern void d_prune_aliases(struct inode *); 259 260 /* test whether we have any submounts in a subdir tree */ 261 extern int have_submounts(struct dentry *); 262 263 /* 264 * This adds the entry to the hash queues. 265 */ 266 extern void d_rehash(struct dentry *); 267 268 /** 269 * d_add - add dentry to hash queues 270 * @entry: dentry to add 271 * @inode: The inode to attach to this dentry 272 * 273 * This adds the entry to the hash queues and initializes @inode. 274 * The entry was actually filled in earlier during d_alloc(). 275 */ 276 277 static inline void d_add(struct dentry *entry, struct inode *inode) 278 { 279 d_instantiate(entry, inode); 280 d_rehash(entry); 281 } 282 283 /** 284 * d_add_unique - add dentry to hash queues without aliasing 285 * @entry: dentry to add 286 * @inode: The inode to attach to this dentry 287 * 288 * This adds the entry to the hash queues and initializes @inode. 289 * The entry was actually filled in earlier during d_alloc(). 290 */ 291 static inline struct dentry *d_add_unique(struct dentry *entry, struct inode *inode) 292 { 293 struct dentry *res; 294 295 res = d_instantiate_unique(entry, inode); 296 d_rehash(res != NULL ? res : entry); 297 return res; 298 } 299 300 extern void dentry_update_name_case(struct dentry *, struct qstr *); 301 302 /* used for rename() and baskets */ 303 extern void d_move(struct dentry *, struct dentry *); 304 extern struct dentry *d_ancestor(struct dentry *, struct dentry *); 305 306 /* appendix may either be NULL or be used for transname suffixes */ 307 extern struct dentry *d_lookup(struct dentry *, struct qstr *); 308 extern struct dentry *d_hash_and_lookup(struct dentry *, struct qstr *); 309 extern struct dentry *__d_lookup(struct dentry *, struct qstr *); 310 extern struct dentry *__d_lookup_rcu(struct dentry *parent, struct qstr *name, 311 unsigned *seq, struct inode **inode); 312 313 /** 314 * __d_rcu_to_refcount - take a refcount on dentry if sequence check is ok 315 * @dentry: dentry to take a ref on 316 * @seq: seqcount to verify against 317 * Returns: 0 on failure, else 1. 318 * 319 * __d_rcu_to_refcount operates on a dentry,seq pair that was returned 320 * by __d_lookup_rcu, to get a reference on an rcu-walk dentry. 321 */ 322 static inline int __d_rcu_to_refcount(struct dentry *dentry, unsigned seq) 323 { 324 int ret = 0; 325 326 assert_spin_locked(&dentry->d_lock); 327 if (!read_seqcount_retry(&dentry->d_seq, seq)) { 328 ret = 1; 329 dentry->d_count++; 330 } 331 332 return ret; 333 } 334 335 /* validate "insecure" dentry pointer */ 336 extern int d_validate(struct dentry *, struct dentry *); 337 338 /* 339 * helper function for dentry_operations.d_dname() members 340 */ 341 extern char *dynamic_dname(struct dentry *, char *, int, const char *, ...); 342 343 extern char *__d_path(const struct path *path, struct path *root, char *, int); 344 extern char *d_path(const struct path *, char *, int); 345 extern char *d_path_with_unreachable(const struct path *, char *, int); 346 extern char *dentry_path_raw(struct dentry *, char *, int); 347 extern char *dentry_path(struct dentry *, char *, int); 348 349 /* Allocation counts.. */ 350 351 /** 352 * dget, dget_dlock - get a reference to a dentry 353 * @dentry: dentry to get a reference to 354 * 355 * Given a dentry or %NULL pointer increment the reference count 356 * if appropriate and return the dentry. A dentry will not be 357 * destroyed when it has references. 358 */ 359 static inline struct dentry *dget_dlock(struct dentry *dentry) 360 { 361 if (dentry) 362 dentry->d_count++; 363 return dentry; 364 } 365 366 static inline struct dentry *dget(struct dentry *dentry) 367 { 368 if (dentry) { 369 spin_lock(&dentry->d_lock); 370 dget_dlock(dentry); 371 spin_unlock(&dentry->d_lock); 372 } 373 return dentry; 374 } 375 376 extern struct dentry *dget_parent(struct dentry *dentry); 377 378 /** 379 * d_unhashed - is dentry hashed 380 * @dentry: entry to check 381 * 382 * Returns true if the dentry passed is not currently hashed. 383 */ 384 385 static inline int d_unhashed(struct dentry *dentry) 386 { 387 return (dentry->d_flags & DCACHE_UNHASHED); 388 } 389 390 static inline int d_unlinked(struct dentry *dentry) 391 { 392 return d_unhashed(dentry) && !IS_ROOT(dentry); 393 } 394 395 static inline int cant_mount(struct dentry *dentry) 396 { 397 return (dentry->d_flags & DCACHE_CANT_MOUNT); 398 } 399 400 static inline void dont_mount(struct dentry *dentry) 401 { 402 spin_lock(&dentry->d_lock); 403 dentry->d_flags |= DCACHE_CANT_MOUNT; 404 spin_unlock(&dentry->d_lock); 405 } 406 407 extern void dput(struct dentry *); 408 409 static inline bool d_managed(struct dentry *dentry) 410 { 411 return dentry->d_flags & DCACHE_MANAGED_DENTRY; 412 } 413 414 static inline bool d_mountpoint(struct dentry *dentry) 415 { 416 return dentry->d_flags & DCACHE_MOUNTED; 417 } 418 419 extern struct dentry *lookup_create(struct nameidata *nd, int is_dir); 420 421 extern int sysctl_vfs_cache_pressure; 422 423 #endif /* __LINUX_DCACHE_H */ 424