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