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 #include <linux/stringhash.h> 14 #include <linux/wait.h> 15 16 struct path; 17 struct vfsmount; 18 19 /* 20 * linux/include/linux/dcache.h 21 * 22 * Dirent cache data structures 23 * 24 * (C) Copyright 1997 Thomas Schoebel-Theuer, 25 * with heavy changes by Linus Torvalds 26 */ 27 28 #define IS_ROOT(x) ((x) == (x)->d_parent) 29 30 /* The hash is always the low bits of hash_len */ 31 #ifdef __LITTLE_ENDIAN 32 #define HASH_LEN_DECLARE u32 hash; u32 len 33 #define bytemask_from_count(cnt) (~(~0ul << (cnt)*8)) 34 #else 35 #define HASH_LEN_DECLARE u32 len; u32 hash 36 #define bytemask_from_count(cnt) (~(~0ul >> (cnt)*8)) 37 #endif 38 39 /* 40 * "quick string" -- eases parameter passing, but more importantly 41 * saves "metadata" about the string (ie length and the hash). 42 * 43 * hash comes first so it snuggles against d_parent in the 44 * dentry. 45 */ 46 struct qstr { 47 union { 48 struct { 49 HASH_LEN_DECLARE; 50 }; 51 u64 hash_len; 52 }; 53 const unsigned char *name; 54 }; 55 56 #define QSTR_INIT(n,l) { { { .len = l } }, .name = n } 57 58 struct dentry_stat_t { 59 long nr_dentry; 60 long nr_unused; 61 long age_limit; /* age in seconds */ 62 long want_pages; /* pages requested by system */ 63 long dummy[2]; 64 }; 65 extern struct dentry_stat_t dentry_stat; 66 67 /* 68 * Try to keep struct dentry aligned on 64 byte cachelines (this will 69 * give reasonable cacheline footprint with larger lines without the 70 * large memory footprint increase). 71 */ 72 #ifdef CONFIG_64BIT 73 # define DNAME_INLINE_LEN 32 /* 192 bytes */ 74 #else 75 # ifdef CONFIG_SMP 76 # define DNAME_INLINE_LEN 36 /* 128 bytes */ 77 # else 78 # define DNAME_INLINE_LEN 40 /* 128 bytes */ 79 # endif 80 #endif 81 82 #define d_lock d_lockref.lock 83 84 struct dentry { 85 /* RCU lookup touched fields */ 86 unsigned int d_flags; /* protected by d_lock */ 87 seqcount_t d_seq; /* per dentry seqlock */ 88 struct hlist_bl_node d_hash; /* lookup hash list */ 89 struct dentry *d_parent; /* parent directory */ 90 struct qstr d_name; 91 struct inode *d_inode; /* Where the name belongs to - NULL is 92 * negative */ 93 unsigned char d_iname[DNAME_INLINE_LEN]; /* small names */ 94 95 /* Ref lookup also touches following */ 96 struct lockref d_lockref; /* per-dentry lock and refcount */ 97 const struct dentry_operations *d_op; 98 struct super_block *d_sb; /* The root of the dentry tree */ 99 unsigned long d_time; /* used by d_revalidate */ 100 void *d_fsdata; /* fs-specific data */ 101 102 union { 103 struct list_head d_lru; /* LRU list */ 104 wait_queue_head_t *d_wait; /* in-lookup ones only */ 105 }; 106 struct list_head d_child; /* child of parent list */ 107 struct list_head d_subdirs; /* our children */ 108 /* 109 * d_alias and d_rcu can share memory 110 */ 111 union { 112 struct hlist_node d_alias; /* inode alias list */ 113 struct hlist_bl_node d_in_lookup_hash; /* only for in-lookup ones */ 114 struct rcu_head d_rcu; 115 } d_u; 116 }; 117 118 /* 119 * dentry->d_lock spinlock nesting subclasses: 120 * 121 * 0: normal 122 * 1: nested 123 */ 124 enum dentry_d_lock_class 125 { 126 DENTRY_D_LOCK_NORMAL, /* implicitly used by plain spin_lock() APIs. */ 127 DENTRY_D_LOCK_NESTED 128 }; 129 130 struct dentry_operations { 131 int (*d_revalidate)(struct dentry *, unsigned int); 132 int (*d_weak_revalidate)(struct dentry *, unsigned int); 133 int (*d_hash)(const struct dentry *, struct qstr *); 134 int (*d_compare)(const struct dentry *, 135 unsigned int, const char *, const struct qstr *); 136 int (*d_delete)(const struct dentry *); 137 int (*d_init)(struct dentry *); 138 void (*d_release)(struct dentry *); 139 void (*d_prune)(struct dentry *); 140 void (*d_iput)(struct dentry *, struct inode *); 141 char *(*d_dname)(struct dentry *, char *, int); 142 struct vfsmount *(*d_automount)(struct path *); 143 int (*d_manage)(const struct path *, bool); 144 struct dentry *(*d_real)(struct dentry *, const struct inode *, 145 unsigned int); 146 } ____cacheline_aligned; 147 148 /* 149 * Locking rules for dentry_operations callbacks are to be found in 150 * Documentation/filesystems/Locking. Keep it updated! 151 * 152 * FUrther descriptions are found in Documentation/filesystems/vfs.txt. 153 * Keep it updated too! 154 */ 155 156 /* d_flags entries */ 157 #define DCACHE_OP_HASH 0x00000001 158 #define DCACHE_OP_COMPARE 0x00000002 159 #define DCACHE_OP_REVALIDATE 0x00000004 160 #define DCACHE_OP_DELETE 0x00000008 161 #define DCACHE_OP_PRUNE 0x00000010 162 163 #define DCACHE_DISCONNECTED 0x00000020 164 /* This dentry is possibly not currently connected to the dcache tree, in 165 * which case its parent will either be itself, or will have this flag as 166 * well. nfsd will not use a dentry with this bit set, but will first 167 * endeavour to clear the bit either by discovering that it is connected, 168 * or by performing lookup operations. Any filesystem which supports 169 * nfsd_operations MUST have a lookup function which, if it finds a 170 * directory inode with a DCACHE_DISCONNECTED dentry, will d_move that 171 * dentry into place and return that dentry rather than the passed one, 172 * typically using d_splice_alias. */ 173 174 #define DCACHE_REFERENCED 0x00000040 /* Recently used, don't discard. */ 175 #define DCACHE_RCUACCESS 0x00000080 /* Entry has ever been RCU-visible */ 176 177 #define DCACHE_CANT_MOUNT 0x00000100 178 #define DCACHE_GENOCIDE 0x00000200 179 #define DCACHE_SHRINK_LIST 0x00000400 180 181 #define DCACHE_OP_WEAK_REVALIDATE 0x00000800 182 183 #define DCACHE_NFSFS_RENAMED 0x00001000 184 /* this dentry has been "silly renamed" and has to be deleted on the last 185 * dput() */ 186 #define DCACHE_COOKIE 0x00002000 /* For use by dcookie subsystem */ 187 #define DCACHE_FSNOTIFY_PARENT_WATCHED 0x00004000 188 /* Parent inode is watched by some fsnotify listener */ 189 190 #define DCACHE_DENTRY_KILLED 0x00008000 191 192 #define DCACHE_MOUNTED 0x00010000 /* is a mountpoint */ 193 #define DCACHE_NEED_AUTOMOUNT 0x00020000 /* handle automount on this dir */ 194 #define DCACHE_MANAGE_TRANSIT 0x00040000 /* manage transit from this dirent */ 195 #define DCACHE_MANAGED_DENTRY \ 196 (DCACHE_MOUNTED|DCACHE_NEED_AUTOMOUNT|DCACHE_MANAGE_TRANSIT) 197 198 #define DCACHE_LRU_LIST 0x00080000 199 200 #define DCACHE_ENTRY_TYPE 0x00700000 201 #define DCACHE_MISS_TYPE 0x00000000 /* Negative dentry (maybe fallthru to nowhere) */ 202 #define DCACHE_WHITEOUT_TYPE 0x00100000 /* Whiteout dentry (stop pathwalk) */ 203 #define DCACHE_DIRECTORY_TYPE 0x00200000 /* Normal directory */ 204 #define DCACHE_AUTODIR_TYPE 0x00300000 /* Lookupless directory (presumed automount) */ 205 #define DCACHE_REGULAR_TYPE 0x00400000 /* Regular file type (or fallthru to such) */ 206 #define DCACHE_SPECIAL_TYPE 0x00500000 /* Other file type (or fallthru to such) */ 207 #define DCACHE_SYMLINK_TYPE 0x00600000 /* Symlink (or fallthru to such) */ 208 209 #define DCACHE_MAY_FREE 0x00800000 210 #define DCACHE_FALLTHRU 0x01000000 /* Fall through to lower layer */ 211 #define DCACHE_ENCRYPTED_WITH_KEY 0x02000000 /* dir is encrypted with a valid key */ 212 #define DCACHE_OP_REAL 0x04000000 213 214 #define DCACHE_PAR_LOOKUP 0x10000000 /* being looked up (with parent locked shared) */ 215 #define DCACHE_DENTRY_CURSOR 0x20000000 216 217 extern seqlock_t rename_lock; 218 219 /* 220 * These are the low-level FS interfaces to the dcache.. 221 */ 222 extern void d_instantiate(struct dentry *, struct inode *); 223 extern struct dentry * d_instantiate_unique(struct dentry *, struct inode *); 224 extern int d_instantiate_no_diralias(struct dentry *, struct inode *); 225 extern void __d_drop(struct dentry *dentry); 226 extern void d_drop(struct dentry *dentry); 227 extern void d_delete(struct dentry *); 228 extern void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op); 229 230 /* allocate/de-allocate */ 231 extern struct dentry * d_alloc(struct dentry *, const struct qstr *); 232 extern struct dentry * d_alloc_pseudo(struct super_block *, const struct qstr *); 233 extern struct dentry * d_alloc_parallel(struct dentry *, const struct qstr *, 234 wait_queue_head_t *); 235 extern struct dentry * d_splice_alias(struct inode *, struct dentry *); 236 extern struct dentry * d_add_ci(struct dentry *, struct inode *, struct qstr *); 237 extern struct dentry * d_exact_alias(struct dentry *, struct inode *); 238 extern struct dentry *d_find_any_alias(struct inode *inode); 239 extern struct dentry * d_obtain_alias(struct inode *); 240 extern struct dentry * d_obtain_root(struct inode *); 241 extern void shrink_dcache_sb(struct super_block *); 242 extern void shrink_dcache_parent(struct dentry *); 243 extern void shrink_dcache_for_umount(struct super_block *); 244 extern void d_invalidate(struct dentry *); 245 246 /* only used at mount-time */ 247 extern struct dentry * d_make_root(struct inode *); 248 249 /* <clickety>-<click> the ramfs-type tree */ 250 extern void d_genocide(struct dentry *); 251 252 extern void d_tmpfile(struct dentry *, struct inode *); 253 254 extern struct dentry *d_find_alias(struct inode *); 255 extern void d_prune_aliases(struct inode *); 256 257 /* test whether we have any submounts in a subdir tree */ 258 extern int path_has_submounts(const struct path *); 259 260 /* 261 * This adds the entry to the hash queues. 262 */ 263 extern void d_rehash(struct dentry *); 264 265 extern void d_add(struct dentry *, struct inode *); 266 267 extern void dentry_update_name_case(struct dentry *, const struct qstr *); 268 269 /* used for rename() and baskets */ 270 extern void d_move(struct dentry *, struct dentry *); 271 extern void d_exchange(struct dentry *, struct dentry *); 272 extern struct dentry *d_ancestor(struct dentry *, struct dentry *); 273 274 /* appendix may either be NULL or be used for transname suffixes */ 275 extern struct dentry *d_lookup(const struct dentry *, const struct qstr *); 276 extern struct dentry *d_hash_and_lookup(struct dentry *, struct qstr *); 277 extern struct dentry *__d_lookup(const struct dentry *, const struct qstr *); 278 extern struct dentry *__d_lookup_rcu(const struct dentry *parent, 279 const struct qstr *name, unsigned *seq); 280 281 static inline unsigned d_count(const struct dentry *dentry) 282 { 283 return dentry->d_lockref.count; 284 } 285 286 /* 287 * helper function for dentry_operations.d_dname() members 288 */ 289 extern __printf(4, 5) 290 char *dynamic_dname(struct dentry *, char *, int, const char *, ...); 291 extern char *simple_dname(struct dentry *, char *, int); 292 293 extern char *__d_path(const struct path *, const struct path *, char *, int); 294 extern char *d_absolute_path(const struct path *, char *, int); 295 extern char *d_path(const struct path *, char *, int); 296 extern char *dentry_path_raw(struct dentry *, char *, int); 297 extern char *dentry_path(struct dentry *, char *, int); 298 299 /* Allocation counts.. */ 300 301 /** 302 * dget, dget_dlock - get a reference to a dentry 303 * @dentry: dentry to get a reference to 304 * 305 * Given a dentry or %NULL pointer increment the reference count 306 * if appropriate and return the dentry. A dentry will not be 307 * destroyed when it has references. 308 */ 309 static inline struct dentry *dget_dlock(struct dentry *dentry) 310 { 311 if (dentry) 312 dentry->d_lockref.count++; 313 return dentry; 314 } 315 316 static inline struct dentry *dget(struct dentry *dentry) 317 { 318 if (dentry) 319 lockref_get(&dentry->d_lockref); 320 return dentry; 321 } 322 323 extern struct dentry *dget_parent(struct dentry *dentry); 324 325 /** 326 * d_unhashed - is dentry hashed 327 * @dentry: entry to check 328 * 329 * Returns true if the dentry passed is not currently hashed. 330 */ 331 332 static inline int d_unhashed(const struct dentry *dentry) 333 { 334 return hlist_bl_unhashed(&dentry->d_hash); 335 } 336 337 static inline int d_unlinked(const struct dentry *dentry) 338 { 339 return d_unhashed(dentry) && !IS_ROOT(dentry); 340 } 341 342 static inline int cant_mount(const struct dentry *dentry) 343 { 344 return (dentry->d_flags & DCACHE_CANT_MOUNT); 345 } 346 347 static inline void dont_mount(struct dentry *dentry) 348 { 349 spin_lock(&dentry->d_lock); 350 dentry->d_flags |= DCACHE_CANT_MOUNT; 351 spin_unlock(&dentry->d_lock); 352 } 353 354 extern void __d_lookup_done(struct dentry *); 355 356 static inline int d_in_lookup(struct dentry *dentry) 357 { 358 return dentry->d_flags & DCACHE_PAR_LOOKUP; 359 } 360 361 static inline void d_lookup_done(struct dentry *dentry) 362 { 363 if (unlikely(d_in_lookup(dentry))) { 364 spin_lock(&dentry->d_lock); 365 __d_lookup_done(dentry); 366 spin_unlock(&dentry->d_lock); 367 } 368 } 369 370 extern void dput(struct dentry *); 371 372 static inline bool d_managed(const struct dentry *dentry) 373 { 374 return dentry->d_flags & DCACHE_MANAGED_DENTRY; 375 } 376 377 static inline bool d_mountpoint(const struct dentry *dentry) 378 { 379 return dentry->d_flags & DCACHE_MOUNTED; 380 } 381 382 /* 383 * Directory cache entry type accessor functions. 384 */ 385 static inline unsigned __d_entry_type(const struct dentry *dentry) 386 { 387 return dentry->d_flags & DCACHE_ENTRY_TYPE; 388 } 389 390 static inline bool d_is_miss(const struct dentry *dentry) 391 { 392 return __d_entry_type(dentry) == DCACHE_MISS_TYPE; 393 } 394 395 static inline bool d_is_whiteout(const struct dentry *dentry) 396 { 397 return __d_entry_type(dentry) == DCACHE_WHITEOUT_TYPE; 398 } 399 400 static inline bool d_can_lookup(const struct dentry *dentry) 401 { 402 return __d_entry_type(dentry) == DCACHE_DIRECTORY_TYPE; 403 } 404 405 static inline bool d_is_autodir(const struct dentry *dentry) 406 { 407 return __d_entry_type(dentry) == DCACHE_AUTODIR_TYPE; 408 } 409 410 static inline bool d_is_dir(const struct dentry *dentry) 411 { 412 return d_can_lookup(dentry) || d_is_autodir(dentry); 413 } 414 415 static inline bool d_is_symlink(const struct dentry *dentry) 416 { 417 return __d_entry_type(dentry) == DCACHE_SYMLINK_TYPE; 418 } 419 420 static inline bool d_is_reg(const struct dentry *dentry) 421 { 422 return __d_entry_type(dentry) == DCACHE_REGULAR_TYPE; 423 } 424 425 static inline bool d_is_special(const struct dentry *dentry) 426 { 427 return __d_entry_type(dentry) == DCACHE_SPECIAL_TYPE; 428 } 429 430 static inline bool d_is_file(const struct dentry *dentry) 431 { 432 return d_is_reg(dentry) || d_is_special(dentry); 433 } 434 435 static inline bool d_is_negative(const struct dentry *dentry) 436 { 437 // TODO: check d_is_whiteout(dentry) also. 438 return d_is_miss(dentry); 439 } 440 441 static inline bool d_is_positive(const struct dentry *dentry) 442 { 443 return !d_is_negative(dentry); 444 } 445 446 /** 447 * d_really_is_negative - Determine if a dentry is really negative (ignoring fallthroughs) 448 * @dentry: The dentry in question 449 * 450 * Returns true if the dentry represents either an absent name or a name that 451 * doesn't map to an inode (ie. ->d_inode is NULL). The dentry could represent 452 * a true miss, a whiteout that isn't represented by a 0,0 chardev or a 453 * fallthrough marker in an opaque directory. 454 * 455 * Note! (1) This should be used *only* by a filesystem to examine its own 456 * dentries. It should not be used to look at some other filesystem's 457 * dentries. (2) It should also be used in combination with d_inode() to get 458 * the inode. (3) The dentry may have something attached to ->d_lower and the 459 * type field of the flags may be set to something other than miss or whiteout. 460 */ 461 static inline bool d_really_is_negative(const struct dentry *dentry) 462 { 463 return dentry->d_inode == NULL; 464 } 465 466 /** 467 * d_really_is_positive - Determine if a dentry is really positive (ignoring fallthroughs) 468 * @dentry: The dentry in question 469 * 470 * Returns true if the dentry represents a name that maps to an inode 471 * (ie. ->d_inode is not NULL). The dentry might still represent a whiteout if 472 * that is represented on medium as a 0,0 chardev. 473 * 474 * Note! (1) This should be used *only* by a filesystem to examine its own 475 * dentries. It should not be used to look at some other filesystem's 476 * dentries. (2) It should also be used in combination with d_inode() to get 477 * the inode. 478 */ 479 static inline bool d_really_is_positive(const struct dentry *dentry) 480 { 481 return dentry->d_inode != NULL; 482 } 483 484 static inline int simple_positive(struct dentry *dentry) 485 { 486 return d_really_is_positive(dentry) && !d_unhashed(dentry); 487 } 488 489 extern void d_set_fallthru(struct dentry *dentry); 490 491 static inline bool d_is_fallthru(const struct dentry *dentry) 492 { 493 return dentry->d_flags & DCACHE_FALLTHRU; 494 } 495 496 497 extern int sysctl_vfs_cache_pressure; 498 499 static inline unsigned long vfs_pressure_ratio(unsigned long val) 500 { 501 return mult_frac(val, sysctl_vfs_cache_pressure, 100); 502 } 503 504 /** 505 * d_inode - Get the actual inode of this dentry 506 * @dentry: The dentry to query 507 * 508 * This is the helper normal filesystems should use to get at their own inodes 509 * in their own dentries and ignore the layering superimposed upon them. 510 */ 511 static inline struct inode *d_inode(const struct dentry *dentry) 512 { 513 return dentry->d_inode; 514 } 515 516 /** 517 * d_inode_rcu - Get the actual inode of this dentry with ACCESS_ONCE() 518 * @dentry: The dentry to query 519 * 520 * This is the helper normal filesystems should use to get at their own inodes 521 * in their own dentries and ignore the layering superimposed upon them. 522 */ 523 static inline struct inode *d_inode_rcu(const struct dentry *dentry) 524 { 525 return ACCESS_ONCE(dentry->d_inode); 526 } 527 528 /** 529 * d_backing_inode - Get upper or lower inode we should be using 530 * @upper: The upper layer 531 * 532 * This is the helper that should be used to get at the inode that will be used 533 * if this dentry were to be opened as a file. The inode may be on the upper 534 * dentry or it may be on a lower dentry pinned by the upper. 535 * 536 * Normal filesystems should not use this to access their own inodes. 537 */ 538 static inline struct inode *d_backing_inode(const struct dentry *upper) 539 { 540 struct inode *inode = upper->d_inode; 541 542 return inode; 543 } 544 545 /** 546 * d_backing_dentry - Get upper or lower dentry we should be using 547 * @upper: The upper layer 548 * 549 * This is the helper that should be used to get the dentry of the inode that 550 * will be used if this dentry were opened as a file. It may be the upper 551 * dentry or it may be a lower dentry pinned by the upper. 552 * 553 * Normal filesystems should not use this to access their own dentries. 554 */ 555 static inline struct dentry *d_backing_dentry(struct dentry *upper) 556 { 557 return upper; 558 } 559 560 /** 561 * d_real - Return the real dentry 562 * @dentry: the dentry to query 563 * @inode: inode to select the dentry from multiple layers (can be NULL) 564 * @flags: open flags to control copy-up behavior 565 * 566 * If dentry is on a union/overlay, then return the underlying, real dentry. 567 * Otherwise return the dentry itself. 568 * 569 * See also: Documentation/filesystems/vfs.txt 570 */ 571 static inline struct dentry *d_real(struct dentry *dentry, 572 const struct inode *inode, 573 unsigned int flags) 574 { 575 if (unlikely(dentry->d_flags & DCACHE_OP_REAL)) 576 return dentry->d_op->d_real(dentry, inode, flags); 577 else 578 return dentry; 579 } 580 581 /** 582 * d_real_inode - Return the real inode 583 * @dentry: The dentry to query 584 * 585 * If dentry is on a union/overlay, then return the underlying, real inode. 586 * Otherwise return d_inode(). 587 */ 588 static inline struct inode *d_real_inode(const struct dentry *dentry) 589 { 590 /* This usage of d_real() results in const dentry */ 591 return d_backing_inode(d_real((struct dentry *) dentry, NULL, 0)); 592 } 593 594 595 #endif /* __LINUX_DCACHE_H */ 596