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 union { 127 struct list_head d_lru; /* LRU list */ 128 wait_queue_head_t *d_wait; /* in-lookup ones only */ 129 }; 130 struct list_head d_child; /* child of parent list */ 131 struct list_head d_subdirs; /* our children */ 132 /* 133 * d_alias and d_rcu can share memory 134 */ 135 union { 136 struct hlist_node d_alias; /* inode alias list */ 137 struct hlist_bl_node d_in_lookup_hash; /* only for in-lookup ones */ 138 struct rcu_head d_rcu; 139 } d_u; 140 }; 141 142 /* 143 * dentry->d_lock spinlock nesting subclasses: 144 * 145 * 0: normal 146 * 1: nested 147 */ 148 enum dentry_d_lock_class 149 { 150 DENTRY_D_LOCK_NORMAL, /* implicitly used by plain spin_lock() APIs. */ 151 DENTRY_D_LOCK_NESTED 152 }; 153 154 struct dentry_operations { 155 int (*d_revalidate)(struct dentry *, unsigned int); 156 int (*d_weak_revalidate)(struct dentry *, unsigned int); 157 int (*d_hash)(const struct dentry *, struct qstr *); 158 int (*d_compare)(const struct dentry *, const struct dentry *, 159 unsigned int, const char *, const struct qstr *); 160 int (*d_delete)(const struct dentry *); 161 void (*d_release)(struct dentry *); 162 void (*d_prune)(struct dentry *); 163 void (*d_iput)(struct dentry *, struct inode *); 164 char *(*d_dname)(struct dentry *, char *, int); 165 struct vfsmount *(*d_automount)(struct path *); 166 int (*d_manage)(struct dentry *, bool); 167 struct inode *(*d_select_inode)(struct dentry *, unsigned); 168 struct dentry *(*d_real)(struct dentry *, struct inode *); 169 } ____cacheline_aligned; 170 171 /* 172 * Locking rules for dentry_operations callbacks are to be found in 173 * Documentation/filesystems/Locking. Keep it updated! 174 * 175 * FUrther descriptions are found in Documentation/filesystems/vfs.txt. 176 * Keep it updated too! 177 */ 178 179 /* d_flags entries */ 180 #define DCACHE_OP_HASH 0x00000001 181 #define DCACHE_OP_COMPARE 0x00000002 182 #define DCACHE_OP_REVALIDATE 0x00000004 183 #define DCACHE_OP_DELETE 0x00000008 184 #define DCACHE_OP_PRUNE 0x00000010 185 186 #define DCACHE_DISCONNECTED 0x00000020 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 0x00000040 /* Recently used, don't discard. */ 198 #define DCACHE_RCUACCESS 0x00000080 /* Entry has ever been RCU-visible */ 199 200 #define DCACHE_CANT_MOUNT 0x00000100 201 #define DCACHE_GENOCIDE 0x00000200 202 #define DCACHE_SHRINK_LIST 0x00000400 203 204 #define DCACHE_OP_WEAK_REVALIDATE 0x00000800 205 206 #define DCACHE_NFSFS_RENAMED 0x00001000 207 /* this dentry has been "silly renamed" and has to be deleted on the last 208 * dput() */ 209 #define DCACHE_COOKIE 0x00002000 /* For use by dcookie subsystem */ 210 #define DCACHE_FSNOTIFY_PARENT_WATCHED 0x00004000 211 /* Parent inode is watched by some fsnotify listener */ 212 213 #define DCACHE_DENTRY_KILLED 0x00008000 214 215 #define DCACHE_MOUNTED 0x00010000 /* is a mountpoint */ 216 #define DCACHE_NEED_AUTOMOUNT 0x00020000 /* handle automount on this dir */ 217 #define DCACHE_MANAGE_TRANSIT 0x00040000 /* manage transit from this dirent */ 218 #define DCACHE_MANAGED_DENTRY \ 219 (DCACHE_MOUNTED|DCACHE_NEED_AUTOMOUNT|DCACHE_MANAGE_TRANSIT) 220 221 #define DCACHE_LRU_LIST 0x00080000 222 223 #define DCACHE_ENTRY_TYPE 0x00700000 224 #define DCACHE_MISS_TYPE 0x00000000 /* Negative dentry (maybe fallthru to nowhere) */ 225 #define DCACHE_WHITEOUT_TYPE 0x00100000 /* Whiteout dentry (stop pathwalk) */ 226 #define DCACHE_DIRECTORY_TYPE 0x00200000 /* Normal directory */ 227 #define DCACHE_AUTODIR_TYPE 0x00300000 /* Lookupless directory (presumed automount) */ 228 #define DCACHE_REGULAR_TYPE 0x00400000 /* Regular file type (or fallthru to such) */ 229 #define DCACHE_SPECIAL_TYPE 0x00500000 /* Other file type (or fallthru to such) */ 230 #define DCACHE_SYMLINK_TYPE 0x00600000 /* Symlink (or fallthru to such) */ 231 232 #define DCACHE_MAY_FREE 0x00800000 233 #define DCACHE_FALLTHRU 0x01000000 /* Fall through to lower layer */ 234 #define DCACHE_OP_SELECT_INODE 0x02000000 /* Unioned entry: dcache op selects inode */ 235 236 #define DCACHE_ENCRYPTED_WITH_KEY 0x04000000 /* dir is encrypted with a valid key */ 237 #define DCACHE_OP_REAL 0x08000000 238 239 #define DCACHE_PAR_LOOKUP 0x10000000 /* being looked up (with parent locked shared) */ 240 241 extern seqlock_t rename_lock; 242 243 /* 244 * These are the low-level FS interfaces to the dcache.. 245 */ 246 extern void d_instantiate(struct dentry *, struct inode *); 247 extern struct dentry * d_instantiate_unique(struct dentry *, struct inode *); 248 extern int d_instantiate_no_diralias(struct dentry *, struct inode *); 249 extern void __d_drop(struct dentry *dentry); 250 extern void d_drop(struct dentry *dentry); 251 extern void d_delete(struct dentry *); 252 extern void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op); 253 254 /* allocate/de-allocate */ 255 extern struct dentry * d_alloc(struct dentry *, const struct qstr *); 256 extern struct dentry * d_alloc_pseudo(struct super_block *, const struct qstr *); 257 extern struct dentry * d_alloc_parallel(struct dentry *, const struct qstr *, 258 wait_queue_head_t *); 259 extern struct dentry * d_splice_alias(struct inode *, struct dentry *); 260 extern struct dentry * d_add_ci(struct dentry *, struct inode *, struct qstr *); 261 extern struct dentry * d_exact_alias(struct dentry *, struct inode *); 262 extern struct dentry *d_find_any_alias(struct inode *inode); 263 extern struct dentry * d_obtain_alias(struct inode *); 264 extern struct dentry * d_obtain_root(struct inode *); 265 extern void shrink_dcache_sb(struct super_block *); 266 extern void shrink_dcache_parent(struct dentry *); 267 extern void shrink_dcache_for_umount(struct super_block *); 268 extern void d_invalidate(struct dentry *); 269 270 /* only used at mount-time */ 271 extern struct dentry * d_make_root(struct inode *); 272 273 /* <clickety>-<click> the ramfs-type tree */ 274 extern void d_genocide(struct dentry *); 275 276 extern void d_tmpfile(struct dentry *, struct inode *); 277 278 extern struct dentry *d_find_alias(struct inode *); 279 extern void d_prune_aliases(struct inode *); 280 281 /* test whether we have any submounts in a subdir tree */ 282 extern int have_submounts(struct dentry *); 283 284 /* 285 * This adds the entry to the hash queues. 286 */ 287 extern void d_rehash(struct dentry *); 288 289 extern void d_add(struct dentry *, struct inode *); 290 291 extern void dentry_update_name_case(struct dentry *, struct qstr *); 292 293 /* used for rename() and baskets */ 294 extern void d_move(struct dentry *, struct dentry *); 295 extern void d_exchange(struct dentry *, struct dentry *); 296 extern struct dentry *d_ancestor(struct dentry *, struct dentry *); 297 298 /* appendix may either be NULL or be used for transname suffixes */ 299 extern struct dentry *d_lookup(const struct dentry *, const struct qstr *); 300 extern struct dentry *d_hash_and_lookup(struct dentry *, struct qstr *); 301 extern struct dentry *__d_lookup(const struct dentry *, const struct qstr *); 302 extern struct dentry *__d_lookup_rcu(const struct dentry *parent, 303 const struct qstr *name, unsigned *seq); 304 305 static inline unsigned d_count(const struct dentry *dentry) 306 { 307 return dentry->d_lockref.count; 308 } 309 310 /* 311 * helper function for dentry_operations.d_dname() members 312 */ 313 extern __printf(4, 5) 314 char *dynamic_dname(struct dentry *, char *, int, const char *, ...); 315 extern char *simple_dname(struct dentry *, char *, int); 316 317 extern char *__d_path(const struct path *, const struct path *, char *, int); 318 extern char *d_absolute_path(const struct path *, char *, int); 319 extern char *d_path(const struct path *, char *, int); 320 extern char *dentry_path_raw(struct dentry *, char *, int); 321 extern char *dentry_path(struct dentry *, char *, int); 322 323 /* Allocation counts.. */ 324 325 /** 326 * dget, dget_dlock - get a reference to a dentry 327 * @dentry: dentry to get a reference to 328 * 329 * Given a dentry or %NULL pointer increment the reference count 330 * if appropriate and return the dentry. A dentry will not be 331 * destroyed when it has references. 332 */ 333 static inline struct dentry *dget_dlock(struct dentry *dentry) 334 { 335 if (dentry) 336 dentry->d_lockref.count++; 337 return dentry; 338 } 339 340 static inline struct dentry *dget(struct dentry *dentry) 341 { 342 if (dentry) 343 lockref_get(&dentry->d_lockref); 344 return dentry; 345 } 346 347 extern struct dentry *dget_parent(struct dentry *dentry); 348 349 /** 350 * d_unhashed - is dentry hashed 351 * @dentry: entry to check 352 * 353 * Returns true if the dentry passed is not currently hashed. 354 */ 355 356 static inline int d_unhashed(const struct dentry *dentry) 357 { 358 return hlist_bl_unhashed(&dentry->d_hash); 359 } 360 361 static inline int d_unlinked(const struct dentry *dentry) 362 { 363 return d_unhashed(dentry) && !IS_ROOT(dentry); 364 } 365 366 static inline int cant_mount(const struct dentry *dentry) 367 { 368 return (dentry->d_flags & DCACHE_CANT_MOUNT); 369 } 370 371 static inline void dont_mount(struct dentry *dentry) 372 { 373 spin_lock(&dentry->d_lock); 374 dentry->d_flags |= DCACHE_CANT_MOUNT; 375 spin_unlock(&dentry->d_lock); 376 } 377 378 extern void __d_lookup_done(struct dentry *); 379 380 static inline int d_in_lookup(struct dentry *dentry) 381 { 382 return dentry->d_flags & DCACHE_PAR_LOOKUP; 383 } 384 385 static inline void d_lookup_done(struct dentry *dentry) 386 { 387 if (unlikely(d_in_lookup(dentry))) { 388 spin_lock(&dentry->d_lock); 389 __d_lookup_done(dentry); 390 spin_unlock(&dentry->d_lock); 391 } 392 } 393 394 extern void dput(struct dentry *); 395 396 static inline bool d_managed(const struct dentry *dentry) 397 { 398 return dentry->d_flags & DCACHE_MANAGED_DENTRY; 399 } 400 401 static inline bool d_mountpoint(const struct dentry *dentry) 402 { 403 return dentry->d_flags & DCACHE_MOUNTED; 404 } 405 406 /* 407 * Directory cache entry type accessor functions. 408 */ 409 static inline unsigned __d_entry_type(const struct dentry *dentry) 410 { 411 return dentry->d_flags & DCACHE_ENTRY_TYPE; 412 } 413 414 static inline bool d_is_miss(const struct dentry *dentry) 415 { 416 return __d_entry_type(dentry) == DCACHE_MISS_TYPE; 417 } 418 419 static inline bool d_is_whiteout(const struct dentry *dentry) 420 { 421 return __d_entry_type(dentry) == DCACHE_WHITEOUT_TYPE; 422 } 423 424 static inline bool d_can_lookup(const struct dentry *dentry) 425 { 426 return __d_entry_type(dentry) == DCACHE_DIRECTORY_TYPE; 427 } 428 429 static inline bool d_is_autodir(const struct dentry *dentry) 430 { 431 return __d_entry_type(dentry) == DCACHE_AUTODIR_TYPE; 432 } 433 434 static inline bool d_is_dir(const struct dentry *dentry) 435 { 436 return d_can_lookup(dentry) || d_is_autodir(dentry); 437 } 438 439 static inline bool d_is_symlink(const struct dentry *dentry) 440 { 441 return __d_entry_type(dentry) == DCACHE_SYMLINK_TYPE; 442 } 443 444 static inline bool d_is_reg(const struct dentry *dentry) 445 { 446 return __d_entry_type(dentry) == DCACHE_REGULAR_TYPE; 447 } 448 449 static inline bool d_is_special(const struct dentry *dentry) 450 { 451 return __d_entry_type(dentry) == DCACHE_SPECIAL_TYPE; 452 } 453 454 static inline bool d_is_file(const struct dentry *dentry) 455 { 456 return d_is_reg(dentry) || d_is_special(dentry); 457 } 458 459 static inline bool d_is_negative(const struct dentry *dentry) 460 { 461 // TODO: check d_is_whiteout(dentry) also. 462 return d_is_miss(dentry); 463 } 464 465 static inline bool d_is_positive(const struct dentry *dentry) 466 { 467 return !d_is_negative(dentry); 468 } 469 470 /** 471 * d_really_is_negative - Determine if a dentry is really negative (ignoring fallthroughs) 472 * @dentry: The dentry in question 473 * 474 * Returns true if the dentry represents either an absent name or a name that 475 * doesn't map to an inode (ie. ->d_inode is NULL). The dentry could represent 476 * a true miss, a whiteout that isn't represented by a 0,0 chardev or a 477 * fallthrough marker in an opaque directory. 478 * 479 * Note! (1) This should be used *only* by a filesystem to examine its own 480 * dentries. It should not be used to look at some other filesystem's 481 * dentries. (2) It should also be used in combination with d_inode() to get 482 * the inode. (3) The dentry may have something attached to ->d_lower and the 483 * type field of the flags may be set to something other than miss or whiteout. 484 */ 485 static inline bool d_really_is_negative(const struct dentry *dentry) 486 { 487 return dentry->d_inode == NULL; 488 } 489 490 /** 491 * d_really_is_positive - Determine if a dentry is really positive (ignoring fallthroughs) 492 * @dentry: The dentry in question 493 * 494 * Returns true if the dentry represents a name that maps to an inode 495 * (ie. ->d_inode is not NULL). The dentry might still represent a whiteout if 496 * that is represented on medium as a 0,0 chardev. 497 * 498 * Note! (1) This should be used *only* by a filesystem to examine its own 499 * dentries. It should not be used to look at some other filesystem's 500 * dentries. (2) It should also be used in combination with d_inode() to get 501 * the inode. 502 */ 503 static inline bool d_really_is_positive(const struct dentry *dentry) 504 { 505 return dentry->d_inode != NULL; 506 } 507 508 static inline int simple_positive(struct dentry *dentry) 509 { 510 return d_really_is_positive(dentry) && !d_unhashed(dentry); 511 } 512 513 extern void d_set_fallthru(struct dentry *dentry); 514 515 static inline bool d_is_fallthru(const struct dentry *dentry) 516 { 517 return dentry->d_flags & DCACHE_FALLTHRU; 518 } 519 520 521 extern int sysctl_vfs_cache_pressure; 522 523 static inline unsigned long vfs_pressure_ratio(unsigned long val) 524 { 525 return mult_frac(val, sysctl_vfs_cache_pressure, 100); 526 } 527 528 /** 529 * d_inode - Get the actual inode of this dentry 530 * @dentry: The dentry to query 531 * 532 * This is the helper normal filesystems should use to get at their own inodes 533 * in their own dentries and ignore the layering superimposed upon them. 534 */ 535 static inline struct inode *d_inode(const struct dentry *dentry) 536 { 537 return dentry->d_inode; 538 } 539 540 /** 541 * d_inode_rcu - Get the actual inode of this dentry with ACCESS_ONCE() 542 * @dentry: The dentry to query 543 * 544 * This is the helper normal filesystems should use to get at their own inodes 545 * in their own dentries and ignore the layering superimposed upon them. 546 */ 547 static inline struct inode *d_inode_rcu(const struct dentry *dentry) 548 { 549 return ACCESS_ONCE(dentry->d_inode); 550 } 551 552 /** 553 * d_backing_inode - Get upper or lower inode we should be using 554 * @upper: The upper layer 555 * 556 * This is the helper that should be used to get at the inode that will be used 557 * if this dentry were to be opened as a file. The inode may be on the upper 558 * dentry or it may be on a lower dentry pinned by the upper. 559 * 560 * Normal filesystems should not use this to access their own inodes. 561 */ 562 static inline struct inode *d_backing_inode(const struct dentry *upper) 563 { 564 struct inode *inode = upper->d_inode; 565 566 return inode; 567 } 568 569 /** 570 * d_backing_dentry - Get upper or lower dentry we should be using 571 * @upper: The upper layer 572 * 573 * This is the helper that should be used to get the dentry of the inode that 574 * will be used if this dentry were opened as a file. It may be the upper 575 * dentry or it may be a lower dentry pinned by the upper. 576 * 577 * Normal filesystems should not use this to access their own dentries. 578 */ 579 static inline struct dentry *d_backing_dentry(struct dentry *upper) 580 { 581 return upper; 582 } 583 584 static inline struct dentry *d_real(struct dentry *dentry) 585 { 586 if (unlikely(dentry->d_flags & DCACHE_OP_REAL)) 587 return dentry->d_op->d_real(dentry, NULL); 588 else 589 return dentry; 590 } 591 592 static inline struct inode *vfs_select_inode(struct dentry *dentry, 593 unsigned open_flags) 594 { 595 struct inode *inode = d_inode(dentry); 596 597 if (inode && unlikely(dentry->d_flags & DCACHE_OP_SELECT_INODE)) 598 inode = dentry->d_op->d_select_inode(dentry, open_flags); 599 600 return inode; 601 } 602 603 604 #endif /* __LINUX_DCACHE_H */ 605