1 #ifndef __LINUX_DCACHE_H 2 #define __LINUX_DCACHE_H 3 4 #include <linux/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 #include <linux/lockref.h> 13 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 /* The hash is always the low bits of hash_len */ 29 #ifdef __LITTLE_ENDIAN 30 #define HASH_LEN_DECLARE u32 hash; u32 len; 31 #define bytemask_from_count(cnt) (~(~0ul << (cnt)*8)) 32 #else 33 #define HASH_LEN_DECLARE u32 len; u32 hash; 34 #define bytemask_from_count(cnt) (~(~0ul >> (cnt)*8)) 35 #endif 36 37 /* 38 * "quick string" -- eases parameter passing, but more importantly 39 * saves "metadata" about the string (ie length and the hash). 40 * 41 * hash comes first so it snuggles against d_parent in the 42 * dentry. 43 */ 44 struct qstr { 45 union { 46 struct { 47 HASH_LEN_DECLARE; 48 }; 49 u64 hash_len; 50 }; 51 const unsigned char *name; 52 }; 53 54 #define QSTR_INIT(n,l) { { { .len = l } }, .name = n } 55 #define hashlen_hash(hashlen) ((u32) (hashlen)) 56 #define hashlen_len(hashlen) ((u32)((hashlen) >> 32)) 57 #define hashlen_create(hash,len) (((u64)(len)<<32)|(u32)(hash)) 58 59 struct dentry_stat_t { 60 long nr_dentry; 61 long nr_unused; 62 long age_limit; /* age in seconds */ 63 long want_pages; /* pages requested by system */ 64 long dummy[2]; 65 }; 66 extern struct dentry_stat_t dentry_stat; 67 68 /* Name hashing routines. Initial hash value */ 69 /* Hash courtesy of the R5 hash in reiserfs modulo sign bits */ 70 #define init_name_hash() 0 71 72 /* partial hash update function. Assume roughly 4 bits per character */ 73 static inline unsigned long 74 partial_name_hash(unsigned long c, unsigned long prevhash) 75 { 76 return (prevhash + (c << 4) + (c >> 4)) * 11; 77 } 78 79 /* 80 * Finally: cut down the number of bits to a int value (and try to avoid 81 * losing bits) 82 */ 83 static inline unsigned long end_name_hash(unsigned long hash) 84 { 85 return (unsigned int) hash; 86 } 87 88 /* Compute the hash for a name string. */ 89 extern unsigned int full_name_hash(const unsigned char *, unsigned int); 90 91 /* 92 * Try to keep struct dentry aligned on 64 byte cachelines (this will 93 * give reasonable cacheline footprint with larger lines without the 94 * large memory footprint increase). 95 */ 96 #ifdef CONFIG_64BIT 97 # define DNAME_INLINE_LEN 32 /* 192 bytes */ 98 #else 99 # ifdef CONFIG_SMP 100 # define DNAME_INLINE_LEN 36 /* 128 bytes */ 101 # else 102 # define DNAME_INLINE_LEN 40 /* 128 bytes */ 103 # endif 104 #endif 105 106 #define d_lock d_lockref.lock 107 108 struct dentry { 109 /* RCU lookup touched fields */ 110 unsigned int d_flags; /* protected by d_lock */ 111 seqcount_t d_seq; /* per dentry seqlock */ 112 struct hlist_bl_node d_hash; /* lookup hash list */ 113 struct dentry *d_parent; /* parent directory */ 114 struct qstr d_name; 115 struct inode *d_inode; /* Where the name belongs to - NULL is 116 * negative */ 117 unsigned char d_iname[DNAME_INLINE_LEN]; /* small names */ 118 119 /* Ref lookup also touches following */ 120 struct lockref d_lockref; /* per-dentry lock and refcount */ 121 const struct dentry_operations *d_op; 122 struct super_block *d_sb; /* The root of the dentry tree */ 123 unsigned long d_time; /* used by d_revalidate */ 124 void *d_fsdata; /* fs-specific data */ 125 126 struct list_head d_lru; /* LRU list */ 127 struct list_head d_child; /* child of parent list */ 128 struct list_head d_subdirs; /* our children */ 129 /* 130 * d_alias and d_rcu can share memory 131 */ 132 union { 133 struct hlist_node d_alias; /* inode alias list */ 134 struct rcu_head d_rcu; 135 } d_u; 136 }; 137 138 /* 139 * dentry->d_lock spinlock nesting subclasses: 140 * 141 * 0: normal 142 * 1: nested 143 */ 144 enum dentry_d_lock_class 145 { 146 DENTRY_D_LOCK_NORMAL, /* implicitly used by plain spin_lock() APIs. */ 147 DENTRY_D_LOCK_NESTED 148 }; 149 150 struct dentry_operations { 151 int (*d_revalidate)(struct dentry *, unsigned int); 152 int (*d_weak_revalidate)(struct dentry *, unsigned int); 153 int (*d_hash)(const struct dentry *, struct qstr *); 154 int (*d_compare)(const struct dentry *, const struct dentry *, 155 unsigned int, const char *, const struct qstr *); 156 int (*d_delete)(const struct dentry *); 157 void (*d_release)(struct dentry *); 158 void (*d_prune)(struct dentry *); 159 void (*d_iput)(struct dentry *, struct inode *); 160 char *(*d_dname)(struct dentry *, char *, int); 161 struct vfsmount *(*d_automount)(struct path *); 162 int (*d_manage)(struct dentry *, bool); 163 } ____cacheline_aligned; 164 165 /* 166 * Locking rules for dentry_operations callbacks are to be found in 167 * Documentation/filesystems/Locking. Keep it updated! 168 * 169 * FUrther descriptions are found in Documentation/filesystems/vfs.txt. 170 * Keep it updated too! 171 */ 172 173 /* d_flags entries */ 174 #define DCACHE_OP_HASH 0x00000001 175 #define DCACHE_OP_COMPARE 0x00000002 176 #define DCACHE_OP_REVALIDATE 0x00000004 177 #define DCACHE_OP_DELETE 0x00000008 178 #define DCACHE_OP_PRUNE 0x00000010 179 180 #define DCACHE_DISCONNECTED 0x00000020 181 /* This dentry is possibly not currently connected to the dcache tree, in 182 * which case its parent will either be itself, or will have this flag as 183 * well. nfsd will not use a dentry with this bit set, but will first 184 * endeavour to clear the bit either by discovering that it is connected, 185 * or by performing lookup operations. Any filesystem which supports 186 * nfsd_operations MUST have a lookup function which, if it finds a 187 * directory inode with a DCACHE_DISCONNECTED dentry, will d_move that 188 * dentry into place and return that dentry rather than the passed one, 189 * typically using d_splice_alias. */ 190 191 #define DCACHE_REFERENCED 0x00000040 /* Recently used, don't discard. */ 192 #define DCACHE_RCUACCESS 0x00000080 /* Entry has ever been RCU-visible */ 193 194 #define DCACHE_CANT_MOUNT 0x00000100 195 #define DCACHE_GENOCIDE 0x00000200 196 #define DCACHE_SHRINK_LIST 0x00000400 197 198 #define DCACHE_OP_WEAK_REVALIDATE 0x00000800 199 200 #define DCACHE_NFSFS_RENAMED 0x00001000 201 /* this dentry has been "silly renamed" and has to be deleted on the last 202 * dput() */ 203 #define DCACHE_COOKIE 0x00002000 /* For use by dcookie subsystem */ 204 #define DCACHE_FSNOTIFY_PARENT_WATCHED 0x00004000 205 /* Parent inode is watched by some fsnotify listener */ 206 207 #define DCACHE_DENTRY_KILLED 0x00008000 208 209 #define DCACHE_MOUNTED 0x00010000 /* is a mountpoint */ 210 #define DCACHE_NEED_AUTOMOUNT 0x00020000 /* handle automount on this dir */ 211 #define DCACHE_MANAGE_TRANSIT 0x00040000 /* manage transit from this dirent */ 212 #define DCACHE_MANAGED_DENTRY \ 213 (DCACHE_MOUNTED|DCACHE_NEED_AUTOMOUNT|DCACHE_MANAGE_TRANSIT) 214 215 #define DCACHE_LRU_LIST 0x00080000 216 217 #define DCACHE_ENTRY_TYPE 0x00700000 218 #define DCACHE_MISS_TYPE 0x00000000 /* Negative dentry (maybe fallthru to nowhere) */ 219 #define DCACHE_WHITEOUT_TYPE 0x00100000 /* Whiteout dentry (stop pathwalk) */ 220 #define DCACHE_DIRECTORY_TYPE 0x00200000 /* Normal directory */ 221 #define DCACHE_AUTODIR_TYPE 0x00300000 /* Lookupless directory (presumed automount) */ 222 #define DCACHE_REGULAR_TYPE 0x00400000 /* Regular file type (or fallthru to such) */ 223 #define DCACHE_SPECIAL_TYPE 0x00500000 /* Other file type (or fallthru to such) */ 224 #define DCACHE_SYMLINK_TYPE 0x00600000 /* Symlink (or fallthru to such) */ 225 226 #define DCACHE_MAY_FREE 0x00800000 227 #define DCACHE_FALLTHRU 0x01000000 /* Fall through to lower layer */ 228 229 extern seqlock_t rename_lock; 230 231 /* 232 * These are the low-level FS interfaces to the dcache.. 233 */ 234 extern void d_instantiate(struct dentry *, struct inode *); 235 extern struct dentry * d_instantiate_unique(struct dentry *, struct inode *); 236 extern int d_instantiate_no_diralias(struct dentry *, struct inode *); 237 extern void __d_drop(struct dentry *dentry); 238 extern void d_drop(struct dentry *dentry); 239 extern void d_delete(struct dentry *); 240 extern void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op); 241 242 /* allocate/de-allocate */ 243 extern struct dentry * d_alloc(struct dentry *, const struct qstr *); 244 extern struct dentry * d_alloc_pseudo(struct super_block *, const struct qstr *); 245 extern struct dentry * d_splice_alias(struct inode *, struct dentry *); 246 extern struct dentry * d_add_ci(struct dentry *, struct inode *, struct qstr *); 247 extern struct dentry *d_find_any_alias(struct inode *inode); 248 extern struct dentry * d_obtain_alias(struct inode *); 249 extern struct dentry * d_obtain_root(struct inode *); 250 extern void shrink_dcache_sb(struct super_block *); 251 extern void shrink_dcache_parent(struct dentry *); 252 extern void shrink_dcache_for_umount(struct super_block *); 253 extern void d_invalidate(struct dentry *); 254 255 /* only used at mount-time */ 256 extern struct dentry * d_make_root(struct inode *); 257 258 /* <clickety>-<click> the ramfs-type tree */ 259 extern void d_genocide(struct dentry *); 260 261 extern void d_tmpfile(struct dentry *, struct inode *); 262 263 extern struct dentry *d_find_alias(struct inode *); 264 extern void d_prune_aliases(struct inode *); 265 266 /* test whether we have any submounts in a subdir tree */ 267 extern int have_submounts(struct dentry *); 268 269 /* 270 * This adds the entry to the hash queues. 271 */ 272 extern void d_rehash(struct dentry *); 273 274 /** 275 * d_add - add dentry to hash queues 276 * @entry: dentry to add 277 * @inode: The inode to attach to this dentry 278 * 279 * This adds the entry to the hash queues and initializes @inode. 280 * The entry was actually filled in earlier during d_alloc(). 281 */ 282 283 static inline void d_add(struct dentry *entry, struct inode *inode) 284 { 285 d_instantiate(entry, inode); 286 d_rehash(entry); 287 } 288 289 /** 290 * d_add_unique - add dentry to hash queues without aliasing 291 * @entry: dentry to add 292 * @inode: The inode to attach to this dentry 293 * 294 * This adds the entry to the hash queues and initializes @inode. 295 * The entry was actually filled in earlier during d_alloc(). 296 */ 297 static inline struct dentry *d_add_unique(struct dentry *entry, struct inode *inode) 298 { 299 struct dentry *res; 300 301 res = d_instantiate_unique(entry, inode); 302 d_rehash(res != NULL ? res : entry); 303 return res; 304 } 305 306 extern void dentry_update_name_case(struct dentry *, struct qstr *); 307 308 /* used for rename() and baskets */ 309 extern void d_move(struct dentry *, struct dentry *); 310 extern void d_exchange(struct dentry *, struct dentry *); 311 extern struct dentry *d_ancestor(struct dentry *, struct dentry *); 312 313 /* appendix may either be NULL or be used for transname suffixes */ 314 extern struct dentry *d_lookup(const struct dentry *, const struct qstr *); 315 extern struct dentry *d_hash_and_lookup(struct dentry *, struct qstr *); 316 extern struct dentry *__d_lookup(const struct dentry *, const struct qstr *); 317 extern struct dentry *__d_lookup_rcu(const struct dentry *parent, 318 const struct qstr *name, unsigned *seq); 319 320 static inline unsigned d_count(const struct dentry *dentry) 321 { 322 return dentry->d_lockref.count; 323 } 324 325 /* 326 * helper function for dentry_operations.d_dname() members 327 */ 328 extern char *dynamic_dname(struct dentry *, char *, int, const char *, ...); 329 extern char *simple_dname(struct dentry *, char *, int); 330 331 extern char *__d_path(const struct path *, const struct path *, char *, int); 332 extern char *d_absolute_path(const struct path *, char *, int); 333 extern char *d_path(const struct path *, char *, int); 334 extern char *dentry_path_raw(struct dentry *, char *, int); 335 extern char *dentry_path(struct dentry *, char *, int); 336 337 /* Allocation counts.. */ 338 339 /** 340 * dget, dget_dlock - get a reference to a dentry 341 * @dentry: dentry to get a reference to 342 * 343 * Given a dentry or %NULL pointer increment the reference count 344 * if appropriate and return the dentry. A dentry will not be 345 * destroyed when it has references. 346 */ 347 static inline struct dentry *dget_dlock(struct dentry *dentry) 348 { 349 if (dentry) 350 dentry->d_lockref.count++; 351 return dentry; 352 } 353 354 static inline struct dentry *dget(struct dentry *dentry) 355 { 356 if (dentry) 357 lockref_get(&dentry->d_lockref); 358 return dentry; 359 } 360 361 extern struct dentry *dget_parent(struct dentry *dentry); 362 363 /** 364 * d_unhashed - is dentry hashed 365 * @dentry: entry to check 366 * 367 * Returns true if the dentry passed is not currently hashed. 368 */ 369 370 static inline int d_unhashed(const struct dentry *dentry) 371 { 372 return hlist_bl_unhashed(&dentry->d_hash); 373 } 374 375 static inline int d_unlinked(const struct dentry *dentry) 376 { 377 return d_unhashed(dentry) && !IS_ROOT(dentry); 378 } 379 380 static inline int cant_mount(const struct dentry *dentry) 381 { 382 return (dentry->d_flags & DCACHE_CANT_MOUNT); 383 } 384 385 static inline void dont_mount(struct dentry *dentry) 386 { 387 spin_lock(&dentry->d_lock); 388 dentry->d_flags |= DCACHE_CANT_MOUNT; 389 spin_unlock(&dentry->d_lock); 390 } 391 392 extern void dput(struct dentry *); 393 394 static inline bool d_managed(const struct dentry *dentry) 395 { 396 return dentry->d_flags & DCACHE_MANAGED_DENTRY; 397 } 398 399 static inline bool d_mountpoint(const struct dentry *dentry) 400 { 401 return dentry->d_flags & DCACHE_MOUNTED; 402 } 403 404 /* 405 * Directory cache entry type accessor functions. 406 */ 407 static inline void __d_set_type(struct dentry *dentry, unsigned type) 408 { 409 dentry->d_flags = (dentry->d_flags & ~DCACHE_ENTRY_TYPE) | type; 410 } 411 412 static inline void __d_clear_type(struct dentry *dentry) 413 { 414 __d_set_type(dentry, DCACHE_MISS_TYPE); 415 } 416 417 static inline void d_set_type(struct dentry *dentry, unsigned type) 418 { 419 spin_lock(&dentry->d_lock); 420 __d_set_type(dentry, type); 421 spin_unlock(&dentry->d_lock); 422 } 423 424 static inline unsigned __d_entry_type(const struct dentry *dentry) 425 { 426 return dentry->d_flags & DCACHE_ENTRY_TYPE; 427 } 428 429 static inline bool d_is_miss(const struct dentry *dentry) 430 { 431 return __d_entry_type(dentry) == DCACHE_MISS_TYPE; 432 } 433 434 static inline bool d_is_whiteout(const struct dentry *dentry) 435 { 436 return __d_entry_type(dentry) == DCACHE_WHITEOUT_TYPE; 437 } 438 439 static inline bool d_can_lookup(const struct dentry *dentry) 440 { 441 return __d_entry_type(dentry) == DCACHE_DIRECTORY_TYPE; 442 } 443 444 static inline bool d_is_autodir(const struct dentry *dentry) 445 { 446 return __d_entry_type(dentry) == DCACHE_AUTODIR_TYPE; 447 } 448 449 static inline bool d_is_dir(const struct dentry *dentry) 450 { 451 return d_can_lookup(dentry) || d_is_autodir(dentry); 452 } 453 454 static inline bool d_is_symlink(const struct dentry *dentry) 455 { 456 return __d_entry_type(dentry) == DCACHE_SYMLINK_TYPE; 457 } 458 459 static inline bool d_is_reg(const struct dentry *dentry) 460 { 461 return __d_entry_type(dentry) == DCACHE_REGULAR_TYPE; 462 } 463 464 static inline bool d_is_special(const struct dentry *dentry) 465 { 466 return __d_entry_type(dentry) == DCACHE_SPECIAL_TYPE; 467 } 468 469 static inline bool d_is_file(const struct dentry *dentry) 470 { 471 return d_is_reg(dentry) || d_is_special(dentry); 472 } 473 474 static inline bool d_is_negative(const struct dentry *dentry) 475 { 476 // TODO: check d_is_whiteout(dentry) also. 477 return d_is_miss(dentry); 478 } 479 480 static inline bool d_is_positive(const struct dentry *dentry) 481 { 482 return !d_is_negative(dentry); 483 } 484 485 extern void d_set_fallthru(struct dentry *dentry); 486 487 static inline bool d_is_fallthru(const struct dentry *dentry) 488 { 489 return dentry->d_flags & DCACHE_FALLTHRU; 490 } 491 492 493 extern int sysctl_vfs_cache_pressure; 494 495 static inline unsigned long vfs_pressure_ratio(unsigned long val) 496 { 497 return mult_frac(val, sysctl_vfs_cache_pressure, 100); 498 } 499 500 /** 501 * d_inode - Get the actual inode of this dentry 502 * @dentry: The dentry to query 503 * 504 * This is the helper normal filesystems should use to get at their own inodes 505 * in their own dentries and ignore the layering superimposed upon them. 506 */ 507 static inline struct inode *d_inode(const struct dentry *dentry) 508 { 509 return dentry->d_inode; 510 } 511 512 /** 513 * d_inode_rcu - Get the actual inode of this dentry with ACCESS_ONCE() 514 * @dentry: The dentry to query 515 * 516 * This is the helper normal filesystems should use to get at their own inodes 517 * in their own dentries and ignore the layering superimposed upon them. 518 */ 519 static inline struct inode *d_inode_rcu(const struct dentry *dentry) 520 { 521 return ACCESS_ONCE(dentry->d_inode); 522 } 523 524 /** 525 * d_backing_inode - Get upper or lower inode we should be using 526 * @upper: The upper layer 527 * 528 * This is the helper that should be used to get at the inode that will be used 529 * if this dentry were to be opened as a file. The inode may be on the upper 530 * dentry or it may be on a lower dentry pinned by the upper. 531 * 532 * Normal filesystems should not use this to access their own inodes. 533 */ 534 static inline struct inode *d_backing_inode(const struct dentry *upper) 535 { 536 struct inode *inode = upper->d_inode; 537 538 return inode; 539 } 540 541 /** 542 * d_backing_dentry - Get upper or lower dentry we should be using 543 * @upper: The upper layer 544 * 545 * This is the helper that should be used to get the dentry of the inode that 546 * will be used if this dentry were opened as a file. It may be the upper 547 * dentry or it may be a lower dentry pinned by the upper. 548 * 549 * Normal filesystems should not use this to access their own dentries. 550 */ 551 static inline struct dentry *d_backing_dentry(struct dentry *upper) 552 { 553 return upper; 554 } 555 556 #endif /* __LINUX_DCACHE_H */ 557