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 extern const char empty_string[]; 59 extern const struct qstr empty_name; 60 extern const char slash_string[]; 61 extern const struct qstr slash_name; 62 63 struct dentry_stat_t { 64 long nr_dentry; 65 long nr_unused; 66 long age_limit; /* age in seconds */ 67 long want_pages; /* pages requested by system */ 68 long dummy[2]; 69 }; 70 extern struct dentry_stat_t dentry_stat; 71 72 /* 73 * Try to keep struct dentry aligned on 64 byte cachelines (this will 74 * give reasonable cacheline footprint with larger lines without the 75 * large memory footprint increase). 76 */ 77 #ifdef CONFIG_64BIT 78 # define DNAME_INLINE_LEN 32 /* 192 bytes */ 79 #else 80 # ifdef CONFIG_SMP 81 # define DNAME_INLINE_LEN 36 /* 128 bytes */ 82 # else 83 # define DNAME_INLINE_LEN 40 /* 128 bytes */ 84 # endif 85 #endif 86 87 #define d_lock d_lockref.lock 88 89 struct dentry { 90 /* RCU lookup touched fields */ 91 unsigned int d_flags; /* protected by d_lock */ 92 seqcount_t d_seq; /* per dentry seqlock */ 93 struct hlist_bl_node d_hash; /* lookup hash list */ 94 struct dentry *d_parent; /* parent directory */ 95 struct qstr d_name; 96 struct inode *d_inode; /* Where the name belongs to - NULL is 97 * negative */ 98 unsigned char d_iname[DNAME_INLINE_LEN]; /* small names */ 99 100 /* Ref lookup also touches following */ 101 struct lockref d_lockref; /* per-dentry lock and refcount */ 102 const struct dentry_operations *d_op; 103 struct super_block *d_sb; /* The root of the dentry tree */ 104 unsigned long d_time; /* used by d_revalidate */ 105 void *d_fsdata; /* fs-specific data */ 106 107 union { 108 struct list_head d_lru; /* LRU list */ 109 wait_queue_head_t *d_wait; /* in-lookup ones only */ 110 }; 111 struct list_head d_child; /* child of parent list */ 112 struct list_head d_subdirs; /* our children */ 113 /* 114 * d_alias and d_rcu can share memory 115 */ 116 union { 117 struct hlist_node d_alias; /* inode alias list */ 118 struct hlist_bl_node d_in_lookup_hash; /* only for in-lookup ones */ 119 struct rcu_head d_rcu; 120 } d_u; 121 } __randomize_layout; 122 123 /* 124 * dentry->d_lock spinlock nesting subclasses: 125 * 126 * 0: normal 127 * 1: nested 128 */ 129 enum dentry_d_lock_class 130 { 131 DENTRY_D_LOCK_NORMAL, /* implicitly used by plain spin_lock() APIs. */ 132 DENTRY_D_LOCK_NESTED 133 }; 134 135 struct dentry_operations { 136 int (*d_revalidate)(struct dentry *, unsigned int); 137 int (*d_weak_revalidate)(struct dentry *, unsigned int); 138 int (*d_hash)(const struct dentry *, struct qstr *); 139 int (*d_compare)(const struct dentry *, 140 unsigned int, const char *, const struct qstr *); 141 int (*d_delete)(const struct dentry *); 142 int (*d_init)(struct dentry *); 143 void (*d_release)(struct dentry *); 144 void (*d_prune)(struct dentry *); 145 void (*d_iput)(struct dentry *, struct inode *); 146 char *(*d_dname)(struct dentry *, char *, int); 147 struct vfsmount *(*d_automount)(struct path *); 148 int (*d_manage)(const struct path *, bool); 149 struct dentry *(*d_real)(struct dentry *, const struct inode *, 150 unsigned int); 151 } ____cacheline_aligned; 152 153 /* 154 * Locking rules for dentry_operations callbacks are to be found in 155 * Documentation/filesystems/Locking. Keep it updated! 156 * 157 * FUrther descriptions are found in Documentation/filesystems/vfs.txt. 158 * Keep it updated too! 159 */ 160 161 /* d_flags entries */ 162 #define DCACHE_OP_HASH 0x00000001 163 #define DCACHE_OP_COMPARE 0x00000002 164 #define DCACHE_OP_REVALIDATE 0x00000004 165 #define DCACHE_OP_DELETE 0x00000008 166 #define DCACHE_OP_PRUNE 0x00000010 167 168 #define DCACHE_DISCONNECTED 0x00000020 169 /* This dentry is possibly not currently connected to the dcache tree, in 170 * which case its parent will either be itself, or will have this flag as 171 * well. nfsd will not use a dentry with this bit set, but will first 172 * endeavour to clear the bit either by discovering that it is connected, 173 * or by performing lookup operations. Any filesystem which supports 174 * nfsd_operations MUST have a lookup function which, if it finds a 175 * directory inode with a DCACHE_DISCONNECTED dentry, will d_move that 176 * dentry into place and return that dentry rather than the passed one, 177 * typically using d_splice_alias. */ 178 179 #define DCACHE_REFERENCED 0x00000040 /* Recently used, don't discard. */ 180 #define DCACHE_RCUACCESS 0x00000080 /* Entry has ever been RCU-visible */ 181 182 #define DCACHE_CANT_MOUNT 0x00000100 183 #define DCACHE_GENOCIDE 0x00000200 184 #define DCACHE_SHRINK_LIST 0x00000400 185 186 #define DCACHE_OP_WEAK_REVALIDATE 0x00000800 187 188 #define DCACHE_NFSFS_RENAMED 0x00001000 189 /* this dentry has been "silly renamed" and has to be deleted on the last 190 * dput() */ 191 #define DCACHE_COOKIE 0x00002000 /* For use by dcookie subsystem */ 192 #define DCACHE_FSNOTIFY_PARENT_WATCHED 0x00004000 193 /* Parent inode is watched by some fsnotify listener */ 194 195 #define DCACHE_DENTRY_KILLED 0x00008000 196 197 #define DCACHE_MOUNTED 0x00010000 /* is a mountpoint */ 198 #define DCACHE_NEED_AUTOMOUNT 0x00020000 /* handle automount on this dir */ 199 #define DCACHE_MANAGE_TRANSIT 0x00040000 /* manage transit from this dirent */ 200 #define DCACHE_MANAGED_DENTRY \ 201 (DCACHE_MOUNTED|DCACHE_NEED_AUTOMOUNT|DCACHE_MANAGE_TRANSIT) 202 203 #define DCACHE_LRU_LIST 0x00080000 204 205 #define DCACHE_ENTRY_TYPE 0x00700000 206 #define DCACHE_MISS_TYPE 0x00000000 /* Negative dentry (maybe fallthru to nowhere) */ 207 #define DCACHE_WHITEOUT_TYPE 0x00100000 /* Whiteout dentry (stop pathwalk) */ 208 #define DCACHE_DIRECTORY_TYPE 0x00200000 /* Normal directory */ 209 #define DCACHE_AUTODIR_TYPE 0x00300000 /* Lookupless directory (presumed automount) */ 210 #define DCACHE_REGULAR_TYPE 0x00400000 /* Regular file type (or fallthru to such) */ 211 #define DCACHE_SPECIAL_TYPE 0x00500000 /* Other file type (or fallthru to such) */ 212 #define DCACHE_SYMLINK_TYPE 0x00600000 /* Symlink (or fallthru to such) */ 213 214 #define DCACHE_MAY_FREE 0x00800000 215 #define DCACHE_FALLTHRU 0x01000000 /* Fall through to lower layer */ 216 #define DCACHE_ENCRYPTED_WITH_KEY 0x02000000 /* dir is encrypted with a valid key */ 217 #define DCACHE_OP_REAL 0x04000000 218 219 #define DCACHE_PAR_LOOKUP 0x10000000 /* being looked up (with parent locked shared) */ 220 #define DCACHE_DENTRY_CURSOR 0x20000000 221 222 extern seqlock_t rename_lock; 223 224 /* 225 * These are the low-level FS interfaces to the dcache.. 226 */ 227 extern void d_instantiate(struct dentry *, struct inode *); 228 extern struct dentry * d_instantiate_unique(struct dentry *, struct inode *); 229 extern int d_instantiate_no_diralias(struct dentry *, struct inode *); 230 extern void __d_drop(struct dentry *dentry); 231 extern void d_drop(struct dentry *dentry); 232 extern void d_delete(struct dentry *); 233 extern void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op); 234 235 /* allocate/de-allocate */ 236 extern struct dentry * d_alloc(struct dentry *, const struct qstr *); 237 extern struct dentry * d_alloc_pseudo(struct super_block *, const struct qstr *); 238 extern struct dentry * d_alloc_parallel(struct dentry *, const struct qstr *, 239 wait_queue_head_t *); 240 extern struct dentry * d_splice_alias(struct inode *, struct dentry *); 241 extern struct dentry * d_add_ci(struct dentry *, struct inode *, struct qstr *); 242 extern struct dentry * d_exact_alias(struct dentry *, struct inode *); 243 extern struct dentry *d_find_any_alias(struct inode *inode); 244 extern struct dentry * d_obtain_alias(struct inode *); 245 extern struct dentry * d_obtain_root(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 void d_invalidate(struct dentry *); 250 251 /* only used at mount-time */ 252 extern struct dentry * d_make_root(struct inode *); 253 254 /* <clickety>-<click> the ramfs-type tree */ 255 extern void d_genocide(struct dentry *); 256 257 extern void d_tmpfile(struct dentry *, struct inode *); 258 259 extern struct dentry *d_find_alias(struct inode *); 260 extern void d_prune_aliases(struct inode *); 261 262 /* test whether we have any submounts in a subdir tree */ 263 extern int path_has_submounts(const struct path *); 264 265 /* 266 * This adds the entry to the hash queues. 267 */ 268 extern void d_rehash(struct dentry *); 269 270 extern void d_add(struct dentry *, struct inode *); 271 272 extern void dentry_update_name_case(struct dentry *, const struct qstr *); 273 274 /* used for rename() and baskets */ 275 extern void d_move(struct dentry *, struct dentry *); 276 extern void d_exchange(struct dentry *, struct dentry *); 277 extern struct dentry *d_ancestor(struct dentry *, struct dentry *); 278 279 /* appendix may either be NULL or be used for transname suffixes */ 280 extern struct dentry *d_lookup(const struct dentry *, const struct qstr *); 281 extern struct dentry *d_hash_and_lookup(struct dentry *, struct qstr *); 282 extern struct dentry *__d_lookup(const struct dentry *, const struct qstr *); 283 extern struct dentry *__d_lookup_rcu(const struct dentry *parent, 284 const struct qstr *name, unsigned *seq); 285 286 static inline unsigned d_count(const struct dentry *dentry) 287 { 288 return dentry->d_lockref.count; 289 } 290 291 /* 292 * helper function for dentry_operations.d_dname() members 293 */ 294 extern __printf(4, 5) 295 char *dynamic_dname(struct dentry *, char *, int, const char *, ...); 296 extern char *simple_dname(struct dentry *, char *, int); 297 298 extern char *__d_path(const struct path *, const struct path *, char *, int); 299 extern char *d_absolute_path(const struct path *, char *, int); 300 extern char *d_path(const struct path *, char *, int); 301 extern char *dentry_path_raw(struct dentry *, char *, int); 302 extern char *dentry_path(struct dentry *, char *, int); 303 304 /* Allocation counts.. */ 305 306 /** 307 * dget, dget_dlock - get a reference to a dentry 308 * @dentry: dentry to get a reference to 309 * 310 * Given a dentry or %NULL pointer increment the reference count 311 * if appropriate and return the dentry. A dentry will not be 312 * destroyed when it has references. 313 */ 314 static inline struct dentry *dget_dlock(struct dentry *dentry) 315 { 316 if (dentry) 317 dentry->d_lockref.count++; 318 return dentry; 319 } 320 321 static inline struct dentry *dget(struct dentry *dentry) 322 { 323 if (dentry) 324 lockref_get(&dentry->d_lockref); 325 return dentry; 326 } 327 328 extern struct dentry *dget_parent(struct dentry *dentry); 329 330 /** 331 * d_unhashed - is dentry hashed 332 * @dentry: entry to check 333 * 334 * Returns true if the dentry passed is not currently hashed. 335 */ 336 337 static inline int d_unhashed(const struct dentry *dentry) 338 { 339 return hlist_bl_unhashed(&dentry->d_hash); 340 } 341 342 static inline int d_unlinked(const struct dentry *dentry) 343 { 344 return d_unhashed(dentry) && !IS_ROOT(dentry); 345 } 346 347 static inline int cant_mount(const struct dentry *dentry) 348 { 349 return (dentry->d_flags & DCACHE_CANT_MOUNT); 350 } 351 352 static inline void dont_mount(struct dentry *dentry) 353 { 354 spin_lock(&dentry->d_lock); 355 dentry->d_flags |= DCACHE_CANT_MOUNT; 356 spin_unlock(&dentry->d_lock); 357 } 358 359 extern void __d_lookup_done(struct dentry *); 360 361 static inline int d_in_lookup(struct dentry *dentry) 362 { 363 return dentry->d_flags & DCACHE_PAR_LOOKUP; 364 } 365 366 static inline void d_lookup_done(struct dentry *dentry) 367 { 368 if (unlikely(d_in_lookup(dentry))) { 369 spin_lock(&dentry->d_lock); 370 __d_lookup_done(dentry); 371 spin_unlock(&dentry->d_lock); 372 } 373 } 374 375 extern void dput(struct dentry *); 376 377 static inline bool d_managed(const struct dentry *dentry) 378 { 379 return dentry->d_flags & DCACHE_MANAGED_DENTRY; 380 } 381 382 static inline bool d_mountpoint(const struct dentry *dentry) 383 { 384 return dentry->d_flags & DCACHE_MOUNTED; 385 } 386 387 /* 388 * Directory cache entry type accessor functions. 389 */ 390 static inline unsigned __d_entry_type(const struct dentry *dentry) 391 { 392 return dentry->d_flags & DCACHE_ENTRY_TYPE; 393 } 394 395 static inline bool d_is_miss(const struct dentry *dentry) 396 { 397 return __d_entry_type(dentry) == DCACHE_MISS_TYPE; 398 } 399 400 static inline bool d_is_whiteout(const struct dentry *dentry) 401 { 402 return __d_entry_type(dentry) == DCACHE_WHITEOUT_TYPE; 403 } 404 405 static inline bool d_can_lookup(const struct dentry *dentry) 406 { 407 return __d_entry_type(dentry) == DCACHE_DIRECTORY_TYPE; 408 } 409 410 static inline bool d_is_autodir(const struct dentry *dentry) 411 { 412 return __d_entry_type(dentry) == DCACHE_AUTODIR_TYPE; 413 } 414 415 static inline bool d_is_dir(const struct dentry *dentry) 416 { 417 return d_can_lookup(dentry) || d_is_autodir(dentry); 418 } 419 420 static inline bool d_is_symlink(const struct dentry *dentry) 421 { 422 return __d_entry_type(dentry) == DCACHE_SYMLINK_TYPE; 423 } 424 425 static inline bool d_is_reg(const struct dentry *dentry) 426 { 427 return __d_entry_type(dentry) == DCACHE_REGULAR_TYPE; 428 } 429 430 static inline bool d_is_special(const struct dentry *dentry) 431 { 432 return __d_entry_type(dentry) == DCACHE_SPECIAL_TYPE; 433 } 434 435 static inline bool d_is_file(const struct dentry *dentry) 436 { 437 return d_is_reg(dentry) || d_is_special(dentry); 438 } 439 440 static inline bool d_is_negative(const struct dentry *dentry) 441 { 442 // TODO: check d_is_whiteout(dentry) also. 443 return d_is_miss(dentry); 444 } 445 446 static inline bool d_is_positive(const struct dentry *dentry) 447 { 448 return !d_is_negative(dentry); 449 } 450 451 /** 452 * d_really_is_negative - Determine if a dentry is really negative (ignoring fallthroughs) 453 * @dentry: The dentry in question 454 * 455 * Returns true if the dentry represents either an absent name or a name that 456 * doesn't map to an inode (ie. ->d_inode is NULL). The dentry could represent 457 * a true miss, a whiteout that isn't represented by a 0,0 chardev or a 458 * fallthrough marker in an opaque directory. 459 * 460 * Note! (1) This should be used *only* by a filesystem to examine its own 461 * dentries. It should not be used to look at some other filesystem's 462 * dentries. (2) It should also be used in combination with d_inode() to get 463 * the inode. (3) The dentry may have something attached to ->d_lower and the 464 * type field of the flags may be set to something other than miss or whiteout. 465 */ 466 static inline bool d_really_is_negative(const struct dentry *dentry) 467 { 468 return dentry->d_inode == NULL; 469 } 470 471 /** 472 * d_really_is_positive - Determine if a dentry is really positive (ignoring fallthroughs) 473 * @dentry: The dentry in question 474 * 475 * Returns true if the dentry represents a name that maps to an inode 476 * (ie. ->d_inode is not NULL). The dentry might still represent a whiteout if 477 * that is represented on medium as a 0,0 chardev. 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. 483 */ 484 static inline bool d_really_is_positive(const struct dentry *dentry) 485 { 486 return dentry->d_inode != NULL; 487 } 488 489 static inline int simple_positive(struct dentry *dentry) 490 { 491 return d_really_is_positive(dentry) && !d_unhashed(dentry); 492 } 493 494 extern void d_set_fallthru(struct dentry *dentry); 495 496 static inline bool d_is_fallthru(const struct dentry *dentry) 497 { 498 return dentry->d_flags & DCACHE_FALLTHRU; 499 } 500 501 502 extern int sysctl_vfs_cache_pressure; 503 504 static inline unsigned long vfs_pressure_ratio(unsigned long val) 505 { 506 return mult_frac(val, sysctl_vfs_cache_pressure, 100); 507 } 508 509 /** 510 * d_inode - Get the actual inode of this dentry 511 * @dentry: The dentry to query 512 * 513 * This is the helper normal filesystems should use to get at their own inodes 514 * in their own dentries and ignore the layering superimposed upon them. 515 */ 516 static inline struct inode *d_inode(const struct dentry *dentry) 517 { 518 return dentry->d_inode; 519 } 520 521 /** 522 * d_inode_rcu - Get the actual inode of this dentry with ACCESS_ONCE() 523 * @dentry: The dentry to query 524 * 525 * This is the helper normal filesystems should use to get at their own inodes 526 * in their own dentries and ignore the layering superimposed upon them. 527 */ 528 static inline struct inode *d_inode_rcu(const struct dentry *dentry) 529 { 530 return ACCESS_ONCE(dentry->d_inode); 531 } 532 533 /** 534 * d_backing_inode - Get upper or lower inode we should be using 535 * @upper: The upper layer 536 * 537 * This is the helper that should be used to get at the inode that will be used 538 * if this dentry were to be opened as a file. The inode may be on the upper 539 * dentry or it may be on a lower dentry pinned by the upper. 540 * 541 * Normal filesystems should not use this to access their own inodes. 542 */ 543 static inline struct inode *d_backing_inode(const struct dentry *upper) 544 { 545 struct inode *inode = upper->d_inode; 546 547 return inode; 548 } 549 550 /** 551 * d_backing_dentry - Get upper or lower dentry we should be using 552 * @upper: The upper layer 553 * 554 * This is the helper that should be used to get the dentry of the inode that 555 * will be used if this dentry were opened as a file. It may be the upper 556 * dentry or it may be a lower dentry pinned by the upper. 557 * 558 * Normal filesystems should not use this to access their own dentries. 559 */ 560 static inline struct dentry *d_backing_dentry(struct dentry *upper) 561 { 562 return upper; 563 } 564 565 /** 566 * d_real - Return the real dentry 567 * @dentry: the dentry to query 568 * @inode: inode to select the dentry from multiple layers (can be NULL) 569 * @flags: open flags to control copy-up behavior 570 * 571 * If dentry is on a union/overlay, then return the underlying, real dentry. 572 * Otherwise return the dentry itself. 573 * 574 * See also: Documentation/filesystems/vfs.txt 575 */ 576 static inline struct dentry *d_real(struct dentry *dentry, 577 const struct inode *inode, 578 unsigned int flags) 579 { 580 if (unlikely(dentry->d_flags & DCACHE_OP_REAL)) 581 return dentry->d_op->d_real(dentry, inode, flags); 582 else 583 return dentry; 584 } 585 586 /** 587 * d_real_inode - Return the real inode 588 * @dentry: The dentry to query 589 * 590 * If dentry is on a union/overlay, then return the underlying, real inode. 591 * Otherwise return d_inode(). 592 */ 593 static inline struct inode *d_real_inode(const struct dentry *dentry) 594 { 595 /* This usage of d_real() results in const dentry */ 596 return d_backing_inode(d_real((struct dentry *) dentry, NULL, 0)); 597 } 598 599 struct name_snapshot { 600 const unsigned char *name; 601 unsigned char inline_name[DNAME_INLINE_LEN]; 602 }; 603 void take_dentry_name_snapshot(struct name_snapshot *, struct dentry *); 604 void release_dentry_name_snapshot(struct name_snapshot *); 605 606 #endif /* __LINUX_DCACHE_H */ 607