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 #define QSTR_LEN(n,l) (struct qstr)QSTR_INIT(n,l) 61 #define QSTR(n) QSTR_LEN(n, strlen(n)) 62 63 extern const struct qstr empty_name; 64 extern const struct qstr slash_name; 65 extern const struct qstr dotdot_name; 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_WORDS 5 /* 192 bytes */ 74 #else 75 # ifdef CONFIG_SMP 76 # define DNAME_INLINE_WORDS 9 /* 128 bytes */ 77 # else 78 # define DNAME_INLINE_WORDS 11 /* 128 bytes */ 79 # endif 80 #endif 81 82 #define DNAME_INLINE_LEN (DNAME_INLINE_WORDS*sizeof(unsigned long)) 83 84 union shortname_store { 85 unsigned char string[DNAME_INLINE_LEN]; 86 unsigned long words[DNAME_INLINE_WORDS]; 87 }; 88 89 #define d_lock d_lockref.lock 90 #define d_iname d_shortname.string 91 92 struct dentry { 93 /* RCU lookup touched fields */ 94 unsigned int d_flags; /* protected by d_lock */ 95 seqcount_spinlock_t d_seq; /* per dentry seqlock */ 96 struct hlist_bl_node d_hash; /* lookup hash list */ 97 struct dentry *d_parent; /* parent directory */ 98 union { 99 struct qstr __d_name; /* for use ONLY in fs/dcache.c */ 100 const struct qstr d_name; 101 }; 102 struct inode *d_inode; /* Where the name belongs to - NULL is 103 * negative */ 104 union shortname_store d_shortname; 105 /* --- cacheline 1 boundary (64 bytes) was 32 bytes ago --- */ 106 107 /* Ref lookup also touches following */ 108 const struct dentry_operations *d_op; 109 struct super_block *d_sb; /* The root of the dentry tree */ 110 unsigned long d_time; /* used by d_revalidate */ 111 void *d_fsdata; /* fs-specific data */ 112 /* --- cacheline 2 boundary (128 bytes) --- */ 113 struct lockref d_lockref; /* per-dentry lock and refcount 114 * keep separate from RCU lookup area if 115 * possible! 116 */ 117 118 union { 119 struct list_head d_lru; /* LRU list */ 120 wait_queue_head_t *d_wait; /* in-lookup ones only */ 121 }; 122 struct hlist_node d_sib; /* child of parent list */ 123 struct hlist_head d_children; /* our children */ 124 /* 125 * d_alias and d_rcu can share memory 126 */ 127 union { 128 struct hlist_node d_alias; /* inode alias list */ 129 struct hlist_bl_node d_in_lookup_hash; /* only for in-lookup ones */ 130 struct rcu_head d_rcu; 131 } d_u; 132 }; 133 134 /* 135 * dentry->d_lock spinlock nesting subclasses: 136 * 137 * 0: normal 138 * 1: nested 139 */ 140 enum dentry_d_lock_class 141 { 142 DENTRY_D_LOCK_NORMAL, /* implicitly used by plain spin_lock() APIs. */ 143 DENTRY_D_LOCK_NESTED 144 }; 145 146 enum d_real_type { 147 D_REAL_DATA, 148 D_REAL_METADATA, 149 }; 150 151 struct dentry_operations { 152 int (*d_revalidate)(struct inode *, const struct qstr *, 153 struct dentry *, unsigned int); 154 int (*d_weak_revalidate)(struct dentry *, unsigned int); 155 int (*d_hash)(const struct dentry *, struct qstr *); 156 int (*d_compare)(const struct dentry *, 157 unsigned int, const char *, const struct qstr *); 158 int (*d_delete)(const struct dentry *); 159 int (*d_init)(struct dentry *); 160 void (*d_release)(struct dentry *); 161 void (*d_prune)(struct dentry *); 162 void (*d_iput)(struct dentry *, struct inode *); 163 char *(*d_dname)(struct dentry *, char *, int); 164 struct vfsmount *(*d_automount)(struct path *); 165 int (*d_manage)(const struct path *, bool); 166 struct dentry *(*d_real)(struct dentry *, enum d_real_type type); 167 bool (*d_unalias_trylock)(const struct dentry *); 168 void (*d_unalias_unlock)(const struct dentry *); 169 } ____cacheline_aligned; 170 171 /* 172 * Locking rules for dentry_operations callbacks are to be found in 173 * Documentation/filesystems/locking.rst. Keep it updated! 174 * 175 * FUrther descriptions are found in Documentation/filesystems/vfs.rst. 176 * Keep it updated too! 177 */ 178 179 /* d_flags entries */ 180 enum dentry_flags { 181 DCACHE_OP_HASH = BIT(0), 182 DCACHE_OP_COMPARE = BIT(1), 183 DCACHE_OP_REVALIDATE = BIT(2), 184 DCACHE_OP_DELETE = BIT(3), 185 DCACHE_OP_PRUNE = BIT(4), 186 /* 187 * This dentry is possibly not currently connected to the dcache tree, 188 * in which case its parent will either be itself, or will have this 189 * flag as well. nfsd will not use a dentry with this bit set, but will 190 * first endeavour to clear the bit either by discovering that it is 191 * connected, or by performing lookup operations. Any filesystem which 192 * supports nfsd_operations MUST have a lookup function which, if it 193 * finds a directory inode with a DCACHE_DISCONNECTED dentry, will 194 * d_move that dentry into place and return that dentry rather than the 195 * passed one, typically using d_splice_alias. 196 */ 197 DCACHE_DISCONNECTED = BIT(5), 198 DCACHE_REFERENCED = BIT(6), /* Recently used, don't discard. */ 199 DCACHE_DONTCACHE = BIT(7), /* Purge from memory on final dput() */ 200 DCACHE_CANT_MOUNT = BIT(8), 201 DCACHE_SHRINK_LIST = BIT(10), 202 DCACHE_OP_WEAK_REVALIDATE = BIT(11), 203 /* 204 * this dentry has been "silly renamed" and has to be deleted on the 205 * last dput() 206 */ 207 DCACHE_NFSFS_RENAMED = BIT(12), 208 DCACHE_FSNOTIFY_PARENT_WATCHED = BIT(13), /* Parent inode is watched by some fsnotify listener */ 209 DCACHE_DENTRY_KILLED = BIT(14), 210 DCACHE_MOUNTED = BIT(15), /* is a mountpoint */ 211 DCACHE_NEED_AUTOMOUNT = BIT(16), /* handle automount on this dir */ 212 DCACHE_MANAGE_TRANSIT = BIT(17), /* manage transit from this dirent */ 213 DCACHE_LRU_LIST = BIT(18), 214 DCACHE_ENTRY_TYPE = (7 << 19), /* bits 19..21 are for storing type: */ 215 DCACHE_MISS_TYPE = (0 << 19), /* Negative dentry */ 216 DCACHE_WHITEOUT_TYPE = (1 << 19), /* Whiteout dentry (stop pathwalk) */ 217 DCACHE_DIRECTORY_TYPE = (2 << 19), /* Normal directory */ 218 DCACHE_AUTODIR_TYPE = (3 << 19), /* Lookupless directory (presumed automount) */ 219 DCACHE_REGULAR_TYPE = (4 << 19), /* Regular file type */ 220 DCACHE_SPECIAL_TYPE = (5 << 19), /* Other file type */ 221 DCACHE_SYMLINK_TYPE = (6 << 19), /* Symlink */ 222 DCACHE_NOKEY_NAME = BIT(22), /* Encrypted name encoded without key */ 223 DCACHE_OP_REAL = BIT(23), 224 DCACHE_PAR_LOOKUP = BIT(24), /* being looked up (with parent locked shared) */ 225 DCACHE_DENTRY_CURSOR = BIT(25), 226 DCACHE_NORCU = BIT(26), /* No RCU delay for freeing */ 227 DCACHE_PERSISTENT = BIT(27) 228 }; 229 230 #define DCACHE_MANAGED_DENTRY \ 231 (DCACHE_MOUNTED|DCACHE_NEED_AUTOMOUNT|DCACHE_MANAGE_TRANSIT) 232 233 extern seqlock_t rename_lock; 234 235 /* 236 * These are the low-level FS interfaces to the dcache.. 237 */ 238 extern void d_instantiate(struct dentry *, struct inode *); 239 extern void d_instantiate_new(struct dentry *, struct inode *); 240 extern void __d_drop(struct dentry *dentry); 241 extern void d_drop(struct dentry *dentry); 242 extern void d_delete(struct dentry *); 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 /* weird procfs mess; *NOT* exported */ 251 extern struct dentry * d_splice_alias_ops(struct inode *, struct dentry *, 252 const struct dentry_operations *); 253 extern struct dentry * d_add_ci(struct dentry *, struct inode *, struct qstr *); 254 extern bool d_same_name(const struct dentry *dentry, const struct dentry *parent, 255 const struct qstr *name); 256 extern struct dentry *d_find_any_alias(struct inode *inode); 257 extern struct dentry * d_obtain_alias(struct inode *); 258 extern struct dentry * d_obtain_root(struct inode *); 259 extern void shrink_dcache_sb(struct super_block *); 260 extern void shrink_dcache_parent(struct dentry *); 261 extern void d_invalidate(struct dentry *); 262 263 /* only used at mount-time */ 264 extern struct dentry * d_make_root(struct inode *); 265 266 extern void d_mark_tmpfile(struct file *, struct inode *); 267 void d_mark_tmpfile_name(struct file *file, const struct qstr *name); 268 extern void d_tmpfile(struct file *, struct inode *); 269 270 extern struct dentry *d_find_alias(struct inode *); 271 extern void d_prune_aliases(struct inode *); 272 extern void d_dispose_if_unused(struct dentry *, struct list_head *); 273 extern void shrink_dentry_list(struct list_head *); 274 275 extern struct dentry *d_find_alias_rcu(struct inode *); 276 277 /* test whether we have any submounts in a subdir tree */ 278 extern int path_has_submounts(const struct path *); 279 280 /* 281 * This adds the entry to the hash queues. 282 */ 283 extern void d_rehash(struct dentry *); 284 285 extern void d_add(struct dentry *, struct inode *); 286 287 /* used for rename() and baskets */ 288 extern void d_move(struct dentry *, struct dentry *); 289 extern void d_exchange(struct dentry *, struct dentry *); 290 extern struct dentry *d_ancestor(struct dentry *, struct dentry *); 291 292 extern struct dentry *d_lookup(const struct dentry *, const struct qstr *); 293 294 static inline unsigned d_count(const struct dentry *dentry) 295 { 296 return dentry->d_lockref.count; 297 } 298 299 ino_t d_parent_ino(struct dentry *dentry); 300 301 /* 302 * helper function for dentry_operations.d_dname() members 303 */ 304 extern __printf(3, 4) 305 char *dynamic_dname(char *, int, const char *, ...); 306 307 extern char *__d_path(const struct path *, const struct path *, char *, int); 308 extern char *d_absolute_path(const struct path *, char *, int); 309 extern char *d_path(const struct path *, char *, int); 310 extern char *dentry_path_raw(const struct dentry *, char *, int); 311 extern char *dentry_path(const struct dentry *, char *, int); 312 313 /* Allocation counts.. */ 314 315 /** 316 * dget_dlock - get a reference to a dentry 317 * @dentry: dentry to get a reference to 318 * 319 * Given a live dentry, increment the reference count and return the dentry. 320 * Caller must hold @dentry->d_lock. Making sure that dentry is alive is 321 * caller's resonsibility. There are many conditions sufficient to guarantee 322 * that; e.g. anything with non-negative refcount is alive, so's anything 323 * hashed, anything positive, anyone's parent, etc. 324 */ 325 static inline struct dentry *dget_dlock(struct dentry *dentry) 326 { 327 dentry->d_lockref.count++; 328 return dentry; 329 } 330 331 332 /** 333 * dget - get a reference to a dentry 334 * @dentry: dentry to get a reference to 335 * 336 * Given a dentry or %NULL pointer increment the reference count 337 * if appropriate and return the dentry. A dentry will not be 338 * destroyed when it has references. Conversely, a dentry with 339 * no references can disappear for any number of reasons, starting 340 * with memory pressure. In other words, that primitive is 341 * used to clone an existing reference; using it on something with 342 * zero refcount is a bug. 343 * 344 * NOTE: it will spin if @dentry->d_lock is held. From the deadlock 345 * avoidance point of view it is equivalent to spin_lock()/increment 346 * refcount/spin_unlock(), so calling it under @dentry->d_lock is 347 * always a bug; so's calling it under ->d_lock on any of its descendents. 348 * 349 */ 350 static inline struct dentry *dget(struct dentry *dentry) 351 { 352 if (dentry) 353 lockref_get(&dentry->d_lockref); 354 return dentry; 355 } 356 357 extern struct dentry *dget_parent(struct dentry *dentry); 358 359 /** 360 * d_unhashed - is dentry hashed 361 * @dentry: entry to check 362 * 363 * Returns true if the dentry passed is not currently hashed. 364 */ 365 static inline int d_unhashed(const struct dentry *dentry) 366 { 367 return hlist_bl_unhashed(&dentry->d_hash); 368 } 369 370 static inline int d_unlinked(const struct dentry *dentry) 371 { 372 return d_unhashed(dentry) && !IS_ROOT(dentry); 373 } 374 375 static inline int cant_mount(const struct dentry *dentry) 376 { 377 return (dentry->d_flags & DCACHE_CANT_MOUNT); 378 } 379 380 static inline void dont_mount(struct dentry *dentry) 381 { 382 spin_lock(&dentry->d_lock); 383 dentry->d_flags |= DCACHE_CANT_MOUNT; 384 spin_unlock(&dentry->d_lock); 385 } 386 387 extern void __d_lookup_unhash_wake(struct dentry *dentry); 388 389 static inline int d_in_lookup(const struct dentry *dentry) 390 { 391 return dentry->d_flags & DCACHE_PAR_LOOKUP; 392 } 393 394 static inline void d_lookup_done(struct dentry *dentry) 395 { 396 if (unlikely(d_in_lookup(dentry))) 397 __d_lookup_unhash_wake(dentry); 398 } 399 400 extern void dput(struct dentry *); 401 402 static inline bool d_managed(const struct dentry *dentry) 403 { 404 return dentry->d_flags & DCACHE_MANAGED_DENTRY; 405 } 406 407 static inline bool d_mountpoint(const struct dentry *dentry) 408 { 409 return dentry->d_flags & DCACHE_MOUNTED; 410 } 411 412 /* 413 * Directory cache entry type accessor functions. 414 */ 415 static inline unsigned __d_entry_type(const struct dentry *dentry) 416 { 417 return dentry->d_flags & DCACHE_ENTRY_TYPE; 418 } 419 420 static inline bool d_is_miss(const struct dentry *dentry) 421 { 422 return __d_entry_type(dentry) == DCACHE_MISS_TYPE; 423 } 424 425 static inline bool d_is_whiteout(const struct dentry *dentry) 426 { 427 return __d_entry_type(dentry) == DCACHE_WHITEOUT_TYPE; 428 } 429 430 static inline bool d_can_lookup(const struct dentry *dentry) 431 { 432 return __d_entry_type(dentry) == DCACHE_DIRECTORY_TYPE; 433 } 434 435 static inline bool d_is_autodir(const struct dentry *dentry) 436 { 437 return __d_entry_type(dentry) == DCACHE_AUTODIR_TYPE; 438 } 439 440 static inline bool d_is_dir(const struct dentry *dentry) 441 { 442 return d_can_lookup(dentry) || d_is_autodir(dentry); 443 } 444 445 static inline bool d_is_symlink(const struct dentry *dentry) 446 { 447 return __d_entry_type(dentry) == DCACHE_SYMLINK_TYPE; 448 } 449 450 static inline bool d_is_reg(const struct dentry *dentry) 451 { 452 return __d_entry_type(dentry) == DCACHE_REGULAR_TYPE; 453 } 454 455 static inline bool d_is_special(const struct dentry *dentry) 456 { 457 return __d_entry_type(dentry) == DCACHE_SPECIAL_TYPE; 458 } 459 460 static inline bool d_is_file(const struct dentry *dentry) 461 { 462 return d_is_reg(dentry) || d_is_special(dentry); 463 } 464 465 static inline bool d_is_negative(const struct dentry *dentry) 466 { 467 // TODO: check d_is_whiteout(dentry) also. 468 return d_is_miss(dentry); 469 } 470 471 static inline bool d_flags_negative(unsigned flags) 472 { 473 return (flags & DCACHE_ENTRY_TYPE) == DCACHE_MISS_TYPE; 474 } 475 476 static inline bool d_is_positive(const struct dentry *dentry) 477 { 478 return !d_is_negative(dentry); 479 } 480 481 /** 482 * d_really_is_negative - Determine if a dentry is really negative (ignoring fallthroughs) 483 * @dentry: The dentry in question 484 * 485 * Returns true if the dentry represents either an absent name or a name that 486 * doesn't map to an inode (ie. ->d_inode is NULL). The dentry could represent 487 * a true miss, a whiteout that isn't represented by a 0,0 chardev or a 488 * fallthrough marker in an opaque directory. 489 * 490 * Note! (1) This should be used *only* by a filesystem to examine its own 491 * dentries. It should not be used to look at some other filesystem's 492 * dentries. (2) It should also be used in combination with d_inode() to get 493 * the inode. (3) The dentry may have something attached to ->d_lower and the 494 * type field of the flags may be set to something other than miss or whiteout. 495 */ 496 static inline bool d_really_is_negative(const struct dentry *dentry) 497 { 498 return dentry->d_inode == NULL; 499 } 500 501 /** 502 * d_really_is_positive - Determine if a dentry is really positive (ignoring fallthroughs) 503 * @dentry: The dentry in question 504 * 505 * Returns true if the dentry represents a name that maps to an inode 506 * (ie. ->d_inode is not NULL). The dentry might still represent a whiteout if 507 * that is represented on medium as a 0,0 chardev. 508 * 509 * Note! (1) This should be used *only* by a filesystem to examine its own 510 * dentries. It should not be used to look at some other filesystem's 511 * dentries. (2) It should also be used in combination with d_inode() to get 512 * the inode. 513 */ 514 static inline bool d_really_is_positive(const struct dentry *dentry) 515 { 516 return dentry->d_inode != NULL; 517 } 518 519 static inline int simple_positive(const struct dentry *dentry) 520 { 521 return d_really_is_positive(dentry) && !d_unhashed(dentry); 522 } 523 524 unsigned long vfs_pressure_ratio(unsigned long val); 525 526 /** 527 * d_inode - Get the actual inode of this dentry 528 * @dentry: The dentry to query 529 * 530 * This is the helper normal filesystems should use to get at their own inodes 531 * in their own dentries and ignore the layering superimposed upon them. 532 */ 533 static inline struct inode *d_inode(const struct dentry *dentry) 534 { 535 return dentry->d_inode; 536 } 537 538 /** 539 * d_inode_rcu - Get the actual inode of this dentry with READ_ONCE() 540 * @dentry: The dentry to query 541 * 542 * This is the helper normal filesystems should use to get at their own inodes 543 * in their own dentries and ignore the layering superimposed upon them. 544 */ 545 static inline struct inode *d_inode_rcu(const struct dentry *dentry) 546 { 547 return READ_ONCE(dentry->d_inode); 548 } 549 550 /** 551 * d_backing_inode - Get upper or lower inode we should be using 552 * @upper: The upper layer 553 * 554 * This is the helper that should be used to get at the inode that will be used 555 * if this dentry were to be opened as a file. The inode may be on the upper 556 * dentry or it may be on a lower dentry pinned by the upper. 557 * 558 * Normal filesystems should not use this to access their own inodes. 559 */ 560 static inline struct inode *d_backing_inode(const struct dentry *upper) 561 { 562 struct inode *inode = upper->d_inode; 563 564 return inode; 565 } 566 567 /** 568 * d_real - Return the real dentry 569 * @dentry: the dentry to query 570 * @type: the type of real dentry (data or metadata) 571 * 572 * If dentry is on a union/overlay, then return the underlying, real dentry. 573 * Otherwise return the dentry itself. 574 * 575 * See also: Documentation/filesystems/vfs.rst 576 */ 577 static inline struct dentry *d_real(struct dentry *dentry, enum d_real_type type) 578 { 579 if (unlikely(dentry->d_flags & DCACHE_OP_REAL)) 580 return dentry->d_op->d_real(dentry, type); 581 else 582 return dentry; 583 } 584 585 /** 586 * d_real_inode - Return the real inode hosting the data 587 * @dentry: The dentry to query 588 * 589 * If dentry is on a union/overlay, then return the underlying, real inode. 590 * Otherwise return d_inode(). 591 */ 592 static inline struct inode *d_real_inode(const struct dentry *dentry) 593 { 594 /* This usage of d_real() results in const dentry */ 595 return d_inode(d_real((struct dentry *) dentry, D_REAL_DATA)); 596 } 597 598 struct name_snapshot { 599 struct qstr name; 600 union shortname_store inline_name; 601 }; 602 void take_dentry_name_snapshot(struct name_snapshot *, struct dentry *); 603 void release_dentry_name_snapshot(struct name_snapshot *); 604 605 static inline struct dentry *d_first_child(const struct dentry *dentry) 606 { 607 return hlist_entry_safe(dentry->d_children.first, struct dentry, d_sib); 608 } 609 610 static inline struct dentry *d_next_sibling(const struct dentry *dentry) 611 { 612 return hlist_entry_safe(dentry->d_sib.next, struct dentry, d_sib); 613 } 614 615 void set_default_d_op(struct super_block *, const struct dentry_operations *); 616 struct dentry *d_make_persistent(struct dentry *, struct inode *); 617 void d_make_discardable(struct dentry *dentry); 618 619 #endif /* __LINUX_DCACHE_H */ 620