1 /* SPDX-License-Identifier: GPL-2.0 */ 2 #ifndef __LINUX_DCACHE_H 3 #define __LINUX_DCACHE_H 4 5 #include <linux/atomic.h> 6 #include <linux/list.h> 7 #include <linux/math.h> 8 #include <linux/rculist.h> 9 #include <linux/rculist_bl.h> 10 #include <linux/spinlock.h> 11 #include <linux/seqlock.h> 12 #include <linux/cache.h> 13 #include <linux/rcupdate.h> 14 #include <linux/lockref.h> 15 #include <linux/stringhash.h> 16 #include <linux/wait.h> 17 18 struct path; 19 struct file; 20 struct vfsmount; 21 22 /* 23 * linux/include/linux/dcache.h 24 * 25 * Dirent cache data structures 26 * 27 * (C) Copyright 1997 Thomas Schoebel-Theuer, 28 * with heavy changes by Linus Torvalds 29 */ 30 31 #define IS_ROOT(x) ((x) == (x)->d_parent) 32 33 /* The hash is always the low bits of hash_len */ 34 #ifdef __LITTLE_ENDIAN 35 #define HASH_LEN_DECLARE u32 hash; u32 len 36 #define bytemask_from_count(cnt) (~(~0ul << (cnt)*8)) 37 #else 38 #define HASH_LEN_DECLARE u32 len; u32 hash 39 #define bytemask_from_count(cnt) (~(~0ul >> (cnt)*8)) 40 #endif 41 42 /* 43 * "quick string" -- eases parameter passing, but more importantly 44 * saves "metadata" about the string (ie length and the hash). 45 * 46 * hash comes first so it snuggles against d_parent in the 47 * dentry. 48 */ 49 struct qstr { 50 union { 51 struct { 52 HASH_LEN_DECLARE; 53 }; 54 u64 hash_len; 55 }; 56 const unsigned char *name; 57 }; 58 59 #define QSTR_INIT(n,l) { { { .len = l } }, .name = n } 60 61 extern const struct qstr empty_name; 62 extern const struct qstr slash_name; 63 extern const struct qstr dotdot_name; 64 65 /* 66 * Try to keep struct dentry aligned on 64 byte cachelines (this will 67 * give reasonable cacheline footprint with larger lines without the 68 * large memory footprint increase). 69 */ 70 #ifdef CONFIG_64BIT 71 # define DNAME_INLINE_WORDS 5 /* 192 bytes */ 72 #else 73 # ifdef CONFIG_SMP 74 # define DNAME_INLINE_WORDS 9 /* 128 bytes */ 75 # else 76 # define DNAME_INLINE_WORDS 11 /* 128 bytes */ 77 # endif 78 #endif 79 80 #define DNAME_INLINE_LEN (DNAME_INLINE_WORDS*sizeof(unsigned long)) 81 82 union shortname_store { 83 unsigned char string[DNAME_INLINE_LEN]; 84 unsigned long words[DNAME_INLINE_WORDS]; 85 }; 86 87 #define d_lock d_lockref.lock 88 #define d_iname d_shortname.string 89 90 struct dentry { 91 /* RCU lookup touched fields */ 92 unsigned int d_flags; /* protected by d_lock */ 93 seqcount_spinlock_t d_seq; /* per dentry seqlock */ 94 struct hlist_bl_node d_hash; /* lookup hash list */ 95 struct dentry *d_parent; /* parent directory */ 96 struct qstr d_name; 97 struct inode *d_inode; /* Where the name belongs to - NULL is 98 * negative */ 99 union shortname_store d_shortname; 100 /* --- cacheline 1 boundary (64 bytes) was 32 bytes ago --- */ 101 102 /* Ref lookup also touches following */ 103 const struct dentry_operations *d_op; 104 struct super_block *d_sb; /* The root of the dentry tree */ 105 unsigned long d_time; /* used by d_revalidate */ 106 void *d_fsdata; /* fs-specific data */ 107 /* --- cacheline 2 boundary (128 bytes) --- */ 108 struct lockref d_lockref; /* per-dentry lock and refcount 109 * keep separate from RCU lookup area if 110 * possible! 111 */ 112 113 union { 114 struct list_head d_lru; /* LRU list */ 115 wait_queue_head_t *d_wait; /* in-lookup ones only */ 116 }; 117 struct hlist_node d_sib; /* child of parent list */ 118 struct hlist_head d_children; /* our children */ 119 /* 120 * d_alias and d_rcu can share memory 121 */ 122 union { 123 struct hlist_node d_alias; /* inode alias list */ 124 struct hlist_bl_node d_in_lookup_hash; /* only for in-lookup ones */ 125 struct rcu_head d_rcu; 126 } d_u; 127 }; 128 129 /* 130 * dentry->d_lock spinlock nesting subclasses: 131 * 132 * 0: normal 133 * 1: nested 134 */ 135 enum dentry_d_lock_class 136 { 137 DENTRY_D_LOCK_NORMAL, /* implicitly used by plain spin_lock() APIs. */ 138 DENTRY_D_LOCK_NESTED 139 }; 140 141 enum d_real_type { 142 D_REAL_DATA, 143 D_REAL_METADATA, 144 }; 145 146 struct dentry_operations { 147 int (*d_revalidate)(struct inode *, const struct qstr *, 148 struct dentry *, unsigned int); 149 int (*d_weak_revalidate)(struct dentry *, unsigned int); 150 int (*d_hash)(const struct dentry *, struct qstr *); 151 int (*d_compare)(const struct dentry *, 152 unsigned int, const char *, const struct qstr *); 153 int (*d_delete)(const struct dentry *); 154 int (*d_init)(struct dentry *); 155 void (*d_release)(struct dentry *); 156 void (*d_prune)(struct dentry *); 157 void (*d_iput)(struct dentry *, struct inode *); 158 char *(*d_dname)(struct dentry *, char *, int); 159 struct vfsmount *(*d_automount)(struct path *); 160 int (*d_manage)(const struct path *, bool); 161 struct dentry *(*d_real)(struct dentry *, enum d_real_type type); 162 } ____cacheline_aligned; 163 164 /* 165 * Locking rules for dentry_operations callbacks are to be found in 166 * Documentation/filesystems/locking.rst. Keep it updated! 167 * 168 * FUrther descriptions are found in Documentation/filesystems/vfs.rst. 169 * Keep it updated too! 170 */ 171 172 /* d_flags entries */ 173 #define DCACHE_OP_HASH BIT(0) 174 #define DCACHE_OP_COMPARE BIT(1) 175 #define DCACHE_OP_REVALIDATE BIT(2) 176 #define DCACHE_OP_DELETE BIT(3) 177 #define DCACHE_OP_PRUNE BIT(4) 178 179 #define DCACHE_DISCONNECTED BIT(5) 180 /* This dentry is possibly not currently connected to the dcache tree, in 181 * which case its parent will either be itself, or will have this flag as 182 * well. nfsd will not use a dentry with this bit set, but will first 183 * endeavour to clear the bit either by discovering that it is connected, 184 * or by performing lookup operations. Any filesystem which supports 185 * nfsd_operations MUST have a lookup function which, if it finds a 186 * directory inode with a DCACHE_DISCONNECTED dentry, will d_move that 187 * dentry into place and return that dentry rather than the passed one, 188 * typically using d_splice_alias. */ 189 190 #define DCACHE_REFERENCED BIT(6) /* Recently used, don't discard. */ 191 192 #define DCACHE_DONTCACHE BIT(7) /* Purge from memory on final dput() */ 193 194 #define DCACHE_CANT_MOUNT BIT(8) 195 #define DCACHE_GENOCIDE BIT(9) 196 #define DCACHE_SHRINK_LIST BIT(10) 197 198 #define DCACHE_OP_WEAK_REVALIDATE BIT(11) 199 200 #define DCACHE_NFSFS_RENAMED BIT(12) 201 /* this dentry has been "silly renamed" and has to be deleted on the last 202 * dput() */ 203 #define DCACHE_FSNOTIFY_PARENT_WATCHED BIT(14) 204 /* Parent inode is watched by some fsnotify listener */ 205 206 #define DCACHE_DENTRY_KILLED BIT(15) 207 208 #define DCACHE_MOUNTED BIT(16) /* is a mountpoint */ 209 #define DCACHE_NEED_AUTOMOUNT BIT(17) /* handle automount on this dir */ 210 #define DCACHE_MANAGE_TRANSIT BIT(18) /* manage transit from this dirent */ 211 #define DCACHE_MANAGED_DENTRY \ 212 (DCACHE_MOUNTED|DCACHE_NEED_AUTOMOUNT|DCACHE_MANAGE_TRANSIT) 213 214 #define DCACHE_LRU_LIST BIT(19) 215 216 #define DCACHE_ENTRY_TYPE (7 << 20) /* bits 20..22 are for storing type: */ 217 #define DCACHE_MISS_TYPE (0 << 20) /* Negative dentry */ 218 #define DCACHE_WHITEOUT_TYPE (1 << 20) /* Whiteout dentry (stop pathwalk) */ 219 #define DCACHE_DIRECTORY_TYPE (2 << 20) /* Normal directory */ 220 #define DCACHE_AUTODIR_TYPE (3 << 20) /* Lookupless directory (presumed automount) */ 221 #define DCACHE_REGULAR_TYPE (4 << 20) /* Regular file type */ 222 #define DCACHE_SPECIAL_TYPE (5 << 20) /* Other file type */ 223 #define DCACHE_SYMLINK_TYPE (6 << 20) /* Symlink */ 224 225 #define DCACHE_NOKEY_NAME BIT(25) /* Encrypted name encoded without key */ 226 #define DCACHE_OP_REAL BIT(26) 227 228 #define DCACHE_PAR_LOOKUP BIT(28) /* being looked up (with parent locked shared) */ 229 #define DCACHE_DENTRY_CURSOR BIT(29) 230 #define DCACHE_NORCU BIT(30) /* No RCU delay for freeing */ 231 232 extern seqlock_t rename_lock; 233 234 /* 235 * These are the low-level FS interfaces to the dcache.. 236 */ 237 extern void d_instantiate(struct dentry *, struct inode *); 238 extern void d_instantiate_new(struct dentry *, struct inode *); 239 extern void __d_drop(struct dentry *dentry); 240 extern void d_drop(struct dentry *dentry); 241 extern void d_delete(struct dentry *); 242 extern void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op); 243 244 /* allocate/de-allocate */ 245 extern struct dentry * d_alloc(struct dentry *, const struct qstr *); 246 extern struct dentry * d_alloc_anon(struct super_block *); 247 extern struct dentry * d_alloc_parallel(struct dentry *, const struct qstr *, 248 wait_queue_head_t *); 249 extern struct dentry * d_splice_alias(struct inode *, struct dentry *); 250 extern struct dentry * d_add_ci(struct dentry *, struct inode *, struct qstr *); 251 extern bool d_same_name(const struct dentry *dentry, const struct dentry *parent, 252 const struct qstr *name); 253 extern struct dentry * d_exact_alias(struct dentry *, struct inode *); 254 extern struct dentry *d_find_any_alias(struct inode *inode); 255 extern struct dentry * d_obtain_alias(struct inode *); 256 extern struct dentry * d_obtain_root(struct inode *); 257 extern void shrink_dcache_sb(struct super_block *); 258 extern void shrink_dcache_parent(struct dentry *); 259 extern void d_invalidate(struct dentry *); 260 261 /* only used at mount-time */ 262 extern struct dentry * d_make_root(struct inode *); 263 264 extern void d_mark_tmpfile(struct file *, struct inode *); 265 extern void d_tmpfile(struct file *, struct inode *); 266 267 extern struct dentry *d_find_alias(struct inode *); 268 extern void d_prune_aliases(struct inode *); 269 270 extern struct dentry *d_find_alias_rcu(struct inode *); 271 272 /* test whether we have any submounts in a subdir tree */ 273 extern int path_has_submounts(const struct path *); 274 275 /* 276 * This adds the entry to the hash queues. 277 */ 278 extern void d_rehash(struct dentry *); 279 280 extern void d_add(struct dentry *, struct inode *); 281 282 /* used for rename() and baskets */ 283 extern void d_move(struct dentry *, struct dentry *); 284 extern void d_exchange(struct dentry *, struct dentry *); 285 extern struct dentry *d_ancestor(struct dentry *, struct dentry *); 286 287 extern struct dentry *d_lookup(const struct dentry *, const struct qstr *); 288 extern struct dentry *d_hash_and_lookup(struct dentry *, struct qstr *); 289 290 static inline unsigned d_count(const struct dentry *dentry) 291 { 292 return dentry->d_lockref.count; 293 } 294 295 ino_t d_parent_ino(struct dentry *dentry); 296 297 /* 298 * helper function for dentry_operations.d_dname() members 299 */ 300 extern __printf(3, 4) 301 char *dynamic_dname(char *, int, const char *, ...); 302 303 extern char *__d_path(const struct path *, const struct path *, char *, int); 304 extern char *d_absolute_path(const struct path *, char *, int); 305 extern char *d_path(const struct path *, char *, int); 306 extern char *dentry_path_raw(const struct dentry *, char *, int); 307 extern char *dentry_path(const struct dentry *, char *, int); 308 309 /* Allocation counts.. */ 310 311 /** 312 * dget_dlock - get a reference to a dentry 313 * @dentry: dentry to get a reference to 314 * 315 * Given a live dentry, increment the reference count and return the dentry. 316 * Caller must hold @dentry->d_lock. Making sure that dentry is alive is 317 * caller's resonsibility. There are many conditions sufficient to guarantee 318 * that; e.g. anything with non-negative refcount is alive, so's anything 319 * hashed, anything positive, anyone's parent, etc. 320 */ 321 static inline struct dentry *dget_dlock(struct dentry *dentry) 322 { 323 dentry->d_lockref.count++; 324 return dentry; 325 } 326 327 328 /** 329 * dget - get a reference to a dentry 330 * @dentry: dentry to get a reference to 331 * 332 * Given a dentry or %NULL pointer increment the reference count 333 * if appropriate and return the dentry. A dentry will not be 334 * destroyed when it has references. Conversely, a dentry with 335 * no references can disappear for any number of reasons, starting 336 * with memory pressure. In other words, that primitive is 337 * used to clone an existing reference; using it on something with 338 * zero refcount is a bug. 339 * 340 * NOTE: it will spin if @dentry->d_lock is held. From the deadlock 341 * avoidance point of view it is equivalent to spin_lock()/increment 342 * refcount/spin_unlock(), so calling it under @dentry->d_lock is 343 * always a bug; so's calling it under ->d_lock on any of its descendents. 344 * 345 */ 346 static inline struct dentry *dget(struct dentry *dentry) 347 { 348 if (dentry) 349 lockref_get(&dentry->d_lockref); 350 return dentry; 351 } 352 353 extern struct dentry *dget_parent(struct dentry *dentry); 354 355 /** 356 * d_unhashed - is dentry hashed 357 * @dentry: entry to check 358 * 359 * Returns true if the dentry passed is not currently hashed. 360 */ 361 static inline int d_unhashed(const struct dentry *dentry) 362 { 363 return hlist_bl_unhashed(&dentry->d_hash); 364 } 365 366 static inline int d_unlinked(const struct dentry *dentry) 367 { 368 return d_unhashed(dentry) && !IS_ROOT(dentry); 369 } 370 371 static inline int cant_mount(const struct dentry *dentry) 372 { 373 return (dentry->d_flags & DCACHE_CANT_MOUNT); 374 } 375 376 static inline void dont_mount(struct dentry *dentry) 377 { 378 spin_lock(&dentry->d_lock); 379 dentry->d_flags |= DCACHE_CANT_MOUNT; 380 spin_unlock(&dentry->d_lock); 381 } 382 383 extern void __d_lookup_unhash_wake(struct dentry *dentry); 384 385 static inline int d_in_lookup(const struct dentry *dentry) 386 { 387 return dentry->d_flags & DCACHE_PAR_LOOKUP; 388 } 389 390 static inline void d_lookup_done(struct dentry *dentry) 391 { 392 if (unlikely(d_in_lookup(dentry))) 393 __d_lookup_unhash_wake(dentry); 394 } 395 396 extern void dput(struct dentry *); 397 398 static inline bool d_managed(const struct dentry *dentry) 399 { 400 return dentry->d_flags & DCACHE_MANAGED_DENTRY; 401 } 402 403 static inline bool d_mountpoint(const struct dentry *dentry) 404 { 405 return dentry->d_flags & DCACHE_MOUNTED; 406 } 407 408 /* 409 * Directory cache entry type accessor functions. 410 */ 411 static inline unsigned __d_entry_type(const struct dentry *dentry) 412 { 413 return dentry->d_flags & DCACHE_ENTRY_TYPE; 414 } 415 416 static inline bool d_is_miss(const struct dentry *dentry) 417 { 418 return __d_entry_type(dentry) == DCACHE_MISS_TYPE; 419 } 420 421 static inline bool d_is_whiteout(const struct dentry *dentry) 422 { 423 return __d_entry_type(dentry) == DCACHE_WHITEOUT_TYPE; 424 } 425 426 static inline bool d_can_lookup(const struct dentry *dentry) 427 { 428 return __d_entry_type(dentry) == DCACHE_DIRECTORY_TYPE; 429 } 430 431 static inline bool d_is_autodir(const struct dentry *dentry) 432 { 433 return __d_entry_type(dentry) == DCACHE_AUTODIR_TYPE; 434 } 435 436 static inline bool d_is_dir(const struct dentry *dentry) 437 { 438 return d_can_lookup(dentry) || d_is_autodir(dentry); 439 } 440 441 static inline bool d_is_symlink(const struct dentry *dentry) 442 { 443 return __d_entry_type(dentry) == DCACHE_SYMLINK_TYPE; 444 } 445 446 static inline bool d_is_reg(const struct dentry *dentry) 447 { 448 return __d_entry_type(dentry) == DCACHE_REGULAR_TYPE; 449 } 450 451 static inline bool d_is_special(const struct dentry *dentry) 452 { 453 return __d_entry_type(dentry) == DCACHE_SPECIAL_TYPE; 454 } 455 456 static inline bool d_is_file(const struct dentry *dentry) 457 { 458 return d_is_reg(dentry) || d_is_special(dentry); 459 } 460 461 static inline bool d_is_negative(const struct dentry *dentry) 462 { 463 // TODO: check d_is_whiteout(dentry) also. 464 return d_is_miss(dentry); 465 } 466 467 static inline bool d_flags_negative(unsigned flags) 468 { 469 return (flags & DCACHE_ENTRY_TYPE) == DCACHE_MISS_TYPE; 470 } 471 472 static inline bool d_is_positive(const struct dentry *dentry) 473 { 474 return !d_is_negative(dentry); 475 } 476 477 /** 478 * d_really_is_negative - Determine if a dentry is really negative (ignoring fallthroughs) 479 * @dentry: The dentry in question 480 * 481 * Returns true if the dentry represents either an absent name or a name that 482 * doesn't map to an inode (ie. ->d_inode is NULL). The dentry could represent 483 * a true miss, a whiteout that isn't represented by a 0,0 chardev or a 484 * fallthrough marker in an opaque directory. 485 * 486 * Note! (1) This should be used *only* by a filesystem to examine its own 487 * dentries. It should not be used to look at some other filesystem's 488 * dentries. (2) It should also be used in combination with d_inode() to get 489 * the inode. (3) The dentry may have something attached to ->d_lower and the 490 * type field of the flags may be set to something other than miss or whiteout. 491 */ 492 static inline bool d_really_is_negative(const struct dentry *dentry) 493 { 494 return dentry->d_inode == NULL; 495 } 496 497 /** 498 * d_really_is_positive - Determine if a dentry is really positive (ignoring fallthroughs) 499 * @dentry: The dentry in question 500 * 501 * Returns true if the dentry represents a name that maps to an inode 502 * (ie. ->d_inode is not NULL). The dentry might still represent a whiteout if 503 * that is represented on medium as a 0,0 chardev. 504 * 505 * Note! (1) This should be used *only* by a filesystem to examine its own 506 * dentries. It should not be used to look at some other filesystem's 507 * dentries. (2) It should also be used in combination with d_inode() to get 508 * the inode. 509 */ 510 static inline bool d_really_is_positive(const struct dentry *dentry) 511 { 512 return dentry->d_inode != NULL; 513 } 514 515 static inline int simple_positive(const struct dentry *dentry) 516 { 517 return d_really_is_positive(dentry) && !d_unhashed(dentry); 518 } 519 520 extern int sysctl_vfs_cache_pressure; 521 522 static inline unsigned long vfs_pressure_ratio(unsigned long val) 523 { 524 return mult_frac(val, sysctl_vfs_cache_pressure, 100); 525 } 526 527 /** 528 * d_inode - Get the actual inode of this dentry 529 * @dentry: The dentry to query 530 * 531 * This is the helper normal filesystems should use to get at their own inodes 532 * in their own dentries and ignore the layering superimposed upon them. 533 */ 534 static inline struct inode *d_inode(const struct dentry *dentry) 535 { 536 return dentry->d_inode; 537 } 538 539 /** 540 * d_inode_rcu - Get the actual inode of this dentry with READ_ONCE() 541 * @dentry: The dentry to query 542 * 543 * This is the helper normal filesystems should use to get at their own inodes 544 * in their own dentries and ignore the layering superimposed upon them. 545 */ 546 static inline struct inode *d_inode_rcu(const struct dentry *dentry) 547 { 548 return READ_ONCE(dentry->d_inode); 549 } 550 551 /** 552 * d_backing_inode - Get upper or lower inode we should be using 553 * @upper: The upper layer 554 * 555 * This is the helper that should be used to get at the inode that will be used 556 * if this dentry were to be opened as a file. The inode may be on the upper 557 * dentry or it may be on a lower dentry pinned by the upper. 558 * 559 * Normal filesystems should not use this to access their own inodes. 560 */ 561 static inline struct inode *d_backing_inode(const struct dentry *upper) 562 { 563 struct inode *inode = upper->d_inode; 564 565 return inode; 566 } 567 568 /** 569 * d_real - Return the real dentry 570 * @dentry: the dentry to query 571 * @type: the type of real dentry (data or metadata) 572 * 573 * If dentry is on a union/overlay, then return the underlying, real dentry. 574 * Otherwise return the dentry itself. 575 * 576 * See also: Documentation/filesystems/vfs.rst 577 */ 578 static inline struct dentry *d_real(struct dentry *dentry, enum d_real_type type) 579 { 580 if (unlikely(dentry->d_flags & DCACHE_OP_REAL)) 581 return dentry->d_op->d_real(dentry, type); 582 else 583 return dentry; 584 } 585 586 /** 587 * d_real_inode - Return the real inode hosting the data 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_inode(d_real((struct dentry *) dentry, D_REAL_DATA)); 597 } 598 599 struct name_snapshot { 600 struct qstr name; 601 union shortname_store inline_name; 602 }; 603 void take_dentry_name_snapshot(struct name_snapshot *, struct dentry *); 604 void release_dentry_name_snapshot(struct name_snapshot *); 605 606 static inline struct dentry *d_first_child(const struct dentry *dentry) 607 { 608 return hlist_entry_safe(dentry->d_children.first, struct dentry, d_sib); 609 } 610 611 static inline struct dentry *d_next_sibling(const struct dentry *dentry) 612 { 613 return hlist_entry_safe(dentry->d_sib.next, struct dentry, d_sib); 614 } 615 616 #endif /* __LINUX_DCACHE_H */ 617