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(n) (struct qstr)QSTR_INIT(n, strlen(n)) 61 62 extern const struct qstr empty_name; 63 extern const struct qstr slash_name; 64 extern const struct qstr dotdot_name; 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_WORDS 5 /* 192 bytes */ 73 #else 74 # ifdef CONFIG_SMP 75 # define DNAME_INLINE_WORDS 9 /* 128 bytes */ 76 # else 77 # define DNAME_INLINE_WORDS 11 /* 128 bytes */ 78 # endif 79 #endif 80 81 #define DNAME_INLINE_LEN (DNAME_INLINE_WORDS*sizeof(unsigned long)) 82 83 union shortname_store { 84 unsigned char string[DNAME_INLINE_LEN]; 85 unsigned long words[DNAME_INLINE_WORDS]; 86 }; 87 88 #define d_lock d_lockref.lock 89 #define d_iname d_shortname.string 90 91 struct dentry { 92 /* RCU lookup touched fields */ 93 unsigned int d_flags; /* protected by d_lock */ 94 seqcount_spinlock_t d_seq; /* per dentry seqlock */ 95 struct hlist_bl_node d_hash; /* lookup hash list */ 96 struct dentry *d_parent; /* parent directory */ 97 struct qstr d_name; 98 struct inode *d_inode; /* Where the name belongs to - NULL is 99 * negative */ 100 union shortname_store d_shortname; 101 /* --- cacheline 1 boundary (64 bytes) was 32 bytes ago --- */ 102 103 /* Ref lookup also touches following */ 104 const struct dentry_operations *d_op; 105 struct super_block *d_sb; /* The root of the dentry tree */ 106 unsigned long d_time; /* used by d_revalidate */ 107 void *d_fsdata; /* fs-specific data */ 108 /* --- cacheline 2 boundary (128 bytes) --- */ 109 struct lockref d_lockref; /* per-dentry lock and refcount 110 * keep separate from RCU lookup area if 111 * possible! 112 */ 113 114 union { 115 struct list_head d_lru; /* LRU list */ 116 wait_queue_head_t *d_wait; /* in-lookup ones only */ 117 }; 118 struct hlist_node d_sib; /* child of parent list */ 119 struct hlist_head d_children; /* our children */ 120 /* 121 * d_alias and d_rcu can share memory 122 */ 123 union { 124 struct hlist_node d_alias; /* inode alias list */ 125 struct hlist_bl_node d_in_lookup_hash; /* only for in-lookup ones */ 126 struct rcu_head d_rcu; 127 } d_u; 128 }; 129 130 /* 131 * dentry->d_lock spinlock nesting subclasses: 132 * 133 * 0: normal 134 * 1: nested 135 */ 136 enum dentry_d_lock_class 137 { 138 DENTRY_D_LOCK_NORMAL, /* implicitly used by plain spin_lock() APIs. */ 139 DENTRY_D_LOCK_NESTED 140 }; 141 142 enum d_real_type { 143 D_REAL_DATA, 144 D_REAL_METADATA, 145 }; 146 147 struct dentry_operations { 148 int (*d_revalidate)(struct inode *, const struct qstr *, 149 struct dentry *, unsigned int); 150 int (*d_weak_revalidate)(struct dentry *, unsigned int); 151 int (*d_hash)(const struct dentry *, struct qstr *); 152 int (*d_compare)(const struct dentry *, 153 unsigned int, const char *, const struct qstr *); 154 int (*d_delete)(const struct dentry *); 155 int (*d_init)(struct dentry *); 156 void (*d_release)(struct dentry *); 157 void (*d_prune)(struct dentry *); 158 void (*d_iput)(struct dentry *, struct inode *); 159 char *(*d_dname)(struct dentry *, char *, int); 160 struct vfsmount *(*d_automount)(struct path *); 161 int (*d_manage)(const struct path *, bool); 162 struct dentry *(*d_real)(struct dentry *, enum d_real_type type); 163 bool (*d_unalias_trylock)(const struct dentry *); 164 void (*d_unalias_unlock)(const struct dentry *); 165 } ____cacheline_aligned; 166 167 /* 168 * Locking rules for dentry_operations callbacks are to be found in 169 * Documentation/filesystems/locking.rst. Keep it updated! 170 * 171 * FUrther descriptions are found in Documentation/filesystems/vfs.rst. 172 * Keep it updated too! 173 */ 174 175 /* d_flags entries */ 176 #define DCACHE_OP_HASH BIT(0) 177 #define DCACHE_OP_COMPARE BIT(1) 178 #define DCACHE_OP_REVALIDATE BIT(2) 179 #define DCACHE_OP_DELETE BIT(3) 180 #define DCACHE_OP_PRUNE BIT(4) 181 182 #define DCACHE_DISCONNECTED BIT(5) 183 /* This dentry is possibly not currently connected to the dcache tree, in 184 * which case its parent will either be itself, or will have this flag as 185 * well. nfsd will not use a dentry with this bit set, but will first 186 * endeavour to clear the bit either by discovering that it is connected, 187 * or by performing lookup operations. Any filesystem which supports 188 * nfsd_operations MUST have a lookup function which, if it finds a 189 * directory inode with a DCACHE_DISCONNECTED dentry, will d_move that 190 * dentry into place and return that dentry rather than the passed one, 191 * typically using d_splice_alias. */ 192 193 #define DCACHE_REFERENCED BIT(6) /* Recently used, don't discard. */ 194 195 #define DCACHE_DONTCACHE BIT(7) /* Purge from memory on final dput() */ 196 197 #define DCACHE_CANT_MOUNT BIT(8) 198 #define DCACHE_GENOCIDE BIT(9) 199 #define DCACHE_SHRINK_LIST BIT(10) 200 201 #define DCACHE_OP_WEAK_REVALIDATE BIT(11) 202 203 #define DCACHE_NFSFS_RENAMED BIT(12) 204 /* this dentry has been "silly renamed" and has to be deleted on the last 205 * dput() */ 206 #define DCACHE_FSNOTIFY_PARENT_WATCHED BIT(13) 207 /* Parent inode is watched by some fsnotify listener */ 208 209 #define DCACHE_DENTRY_KILLED BIT(14) 210 211 #define DCACHE_MOUNTED BIT(15) /* is a mountpoint */ 212 #define DCACHE_NEED_AUTOMOUNT BIT(16) /* handle automount on this dir */ 213 #define DCACHE_MANAGE_TRANSIT BIT(17) /* manage transit from this dirent */ 214 #define DCACHE_MANAGED_DENTRY \ 215 (DCACHE_MOUNTED|DCACHE_NEED_AUTOMOUNT|DCACHE_MANAGE_TRANSIT) 216 217 #define DCACHE_LRU_LIST BIT(18) 218 219 #define DCACHE_ENTRY_TYPE (7 << 19) /* bits 19..21 are for storing type: */ 220 #define DCACHE_MISS_TYPE (0 << 19) /* Negative dentry */ 221 #define DCACHE_WHITEOUT_TYPE (1 << 19) /* Whiteout dentry (stop pathwalk) */ 222 #define DCACHE_DIRECTORY_TYPE (2 << 19) /* Normal directory */ 223 #define DCACHE_AUTODIR_TYPE (3 << 19) /* Lookupless directory (presumed automount) */ 224 #define DCACHE_REGULAR_TYPE (4 << 19) /* Regular file type */ 225 #define DCACHE_SPECIAL_TYPE (5 << 19) /* Other file type */ 226 #define DCACHE_SYMLINK_TYPE (6 << 19) /* Symlink */ 227 228 #define DCACHE_NOKEY_NAME BIT(22) /* Encrypted name encoded without key */ 229 #define DCACHE_OP_REAL BIT(23) 230 231 #define DCACHE_PAR_LOOKUP BIT(24) /* being looked up (with parent locked shared) */ 232 #define DCACHE_DENTRY_CURSOR BIT(25) 233 #define DCACHE_NORCU BIT(26) /* No RCU delay for freeing */ 234 235 extern seqlock_t rename_lock; 236 237 /* 238 * These are the low-level FS interfaces to the dcache.. 239 */ 240 extern void d_instantiate(struct dentry *, struct inode *); 241 extern void d_instantiate_new(struct dentry *, struct inode *); 242 extern void __d_drop(struct dentry *dentry); 243 extern void d_drop(struct dentry *dentry); 244 extern void d_delete(struct dentry *); 245 extern void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op); 246 247 /* allocate/de-allocate */ 248 extern struct dentry * d_alloc(struct dentry *, const struct qstr *); 249 extern struct dentry * d_alloc_anon(struct super_block *); 250 extern struct dentry * d_alloc_parallel(struct dentry *, const struct qstr *, 251 wait_queue_head_t *); 252 extern struct dentry * d_splice_alias(struct inode *, struct dentry *); 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 extern void d_tmpfile(struct file *, struct inode *); 268 269 extern struct dentry *d_find_alias(struct inode *); 270 extern void d_prune_aliases(struct inode *); 271 272 extern struct dentry *d_find_alias_rcu(struct inode *); 273 274 /* test whether we have any submounts in a subdir tree */ 275 extern int path_has_submounts(const struct path *); 276 277 /* 278 * This adds the entry to the hash queues. 279 */ 280 extern void d_rehash(struct dentry *); 281 282 extern void d_add(struct dentry *, struct inode *); 283 284 /* used for rename() and baskets */ 285 extern void d_move(struct dentry *, struct dentry *); 286 extern void d_exchange(struct dentry *, struct dentry *); 287 extern struct dentry *d_ancestor(struct dentry *, struct dentry *); 288 289 extern struct dentry *d_lookup(const struct dentry *, const struct qstr *); 290 extern struct dentry *d_hash_and_lookup(struct dentry *, struct qstr *); 291 292 static inline unsigned d_count(const struct dentry *dentry) 293 { 294 return dentry->d_lockref.count; 295 } 296 297 ino_t d_parent_ino(struct dentry *dentry); 298 299 /* 300 * helper function for dentry_operations.d_dname() members 301 */ 302 extern __printf(3, 4) 303 char *dynamic_dname(char *, int, const char *, ...); 304 305 extern char *__d_path(const struct path *, const struct path *, char *, int); 306 extern char *d_absolute_path(const struct path *, char *, int); 307 extern char *d_path(const struct path *, char *, int); 308 extern char *dentry_path_raw(const struct dentry *, char *, int); 309 extern char *dentry_path(const struct dentry *, char *, int); 310 311 /* Allocation counts.. */ 312 313 /** 314 * dget_dlock - get a reference to a dentry 315 * @dentry: dentry to get a reference to 316 * 317 * Given a live dentry, increment the reference count and return the dentry. 318 * Caller must hold @dentry->d_lock. Making sure that dentry is alive is 319 * caller's resonsibility. There are many conditions sufficient to guarantee 320 * that; e.g. anything with non-negative refcount is alive, so's anything 321 * hashed, anything positive, anyone's parent, etc. 322 */ 323 static inline struct dentry *dget_dlock(struct dentry *dentry) 324 { 325 dentry->d_lockref.count++; 326 return dentry; 327 } 328 329 330 /** 331 * dget - get a reference to a dentry 332 * @dentry: dentry to get a reference to 333 * 334 * Given a dentry or %NULL pointer increment the reference count 335 * if appropriate and return the dentry. A dentry will not be 336 * destroyed when it has references. Conversely, a dentry with 337 * no references can disappear for any number of reasons, starting 338 * with memory pressure. In other words, that primitive is 339 * used to clone an existing reference; using it on something with 340 * zero refcount is a bug. 341 * 342 * NOTE: it will spin if @dentry->d_lock is held. From the deadlock 343 * avoidance point of view it is equivalent to spin_lock()/increment 344 * refcount/spin_unlock(), so calling it under @dentry->d_lock is 345 * always a bug; so's calling it under ->d_lock on any of its descendents. 346 * 347 */ 348 static inline struct dentry *dget(struct dentry *dentry) 349 { 350 if (dentry) 351 lockref_get(&dentry->d_lockref); 352 return dentry; 353 } 354 355 extern struct dentry *dget_parent(struct dentry *dentry); 356 357 /** 358 * d_unhashed - is dentry hashed 359 * @dentry: entry to check 360 * 361 * Returns true if the dentry passed is not currently hashed. 362 */ 363 static inline int d_unhashed(const struct dentry *dentry) 364 { 365 return hlist_bl_unhashed(&dentry->d_hash); 366 } 367 368 static inline int d_unlinked(const struct dentry *dentry) 369 { 370 return d_unhashed(dentry) && !IS_ROOT(dentry); 371 } 372 373 static inline int cant_mount(const struct dentry *dentry) 374 { 375 return (dentry->d_flags & DCACHE_CANT_MOUNT); 376 } 377 378 static inline void dont_mount(struct dentry *dentry) 379 { 380 spin_lock(&dentry->d_lock); 381 dentry->d_flags |= DCACHE_CANT_MOUNT; 382 spin_unlock(&dentry->d_lock); 383 } 384 385 extern void __d_lookup_unhash_wake(struct dentry *dentry); 386 387 static inline int d_in_lookup(const struct dentry *dentry) 388 { 389 return dentry->d_flags & DCACHE_PAR_LOOKUP; 390 } 391 392 static inline void d_lookup_done(struct dentry *dentry) 393 { 394 if (unlikely(d_in_lookup(dentry))) 395 __d_lookup_unhash_wake(dentry); 396 } 397 398 extern void dput(struct dentry *); 399 400 static inline bool d_managed(const struct dentry *dentry) 401 { 402 return dentry->d_flags & DCACHE_MANAGED_DENTRY; 403 } 404 405 static inline bool d_mountpoint(const struct dentry *dentry) 406 { 407 return dentry->d_flags & DCACHE_MOUNTED; 408 } 409 410 /* 411 * Directory cache entry type accessor functions. 412 */ 413 static inline unsigned __d_entry_type(const struct dentry *dentry) 414 { 415 return dentry->d_flags & DCACHE_ENTRY_TYPE; 416 } 417 418 static inline bool d_is_miss(const struct dentry *dentry) 419 { 420 return __d_entry_type(dentry) == DCACHE_MISS_TYPE; 421 } 422 423 static inline bool d_is_whiteout(const struct dentry *dentry) 424 { 425 return __d_entry_type(dentry) == DCACHE_WHITEOUT_TYPE; 426 } 427 428 static inline bool d_can_lookup(const struct dentry *dentry) 429 { 430 return __d_entry_type(dentry) == DCACHE_DIRECTORY_TYPE; 431 } 432 433 static inline bool d_is_autodir(const struct dentry *dentry) 434 { 435 return __d_entry_type(dentry) == DCACHE_AUTODIR_TYPE; 436 } 437 438 static inline bool d_is_dir(const struct dentry *dentry) 439 { 440 return d_can_lookup(dentry) || d_is_autodir(dentry); 441 } 442 443 static inline bool d_is_symlink(const struct dentry *dentry) 444 { 445 return __d_entry_type(dentry) == DCACHE_SYMLINK_TYPE; 446 } 447 448 static inline bool d_is_reg(const struct dentry *dentry) 449 { 450 return __d_entry_type(dentry) == DCACHE_REGULAR_TYPE; 451 } 452 453 static inline bool d_is_special(const struct dentry *dentry) 454 { 455 return __d_entry_type(dentry) == DCACHE_SPECIAL_TYPE; 456 } 457 458 static inline bool d_is_file(const struct dentry *dentry) 459 { 460 return d_is_reg(dentry) || d_is_special(dentry); 461 } 462 463 static inline bool d_is_negative(const struct dentry *dentry) 464 { 465 // TODO: check d_is_whiteout(dentry) also. 466 return d_is_miss(dentry); 467 } 468 469 static inline bool d_flags_negative(unsigned flags) 470 { 471 return (flags & DCACHE_ENTRY_TYPE) == DCACHE_MISS_TYPE; 472 } 473 474 static inline bool d_is_positive(const struct dentry *dentry) 475 { 476 return !d_is_negative(dentry); 477 } 478 479 /** 480 * d_really_is_negative - Determine if a dentry is really negative (ignoring fallthroughs) 481 * @dentry: The dentry in question 482 * 483 * Returns true if the dentry represents either an absent name or a name that 484 * doesn't map to an inode (ie. ->d_inode is NULL). The dentry could represent 485 * a true miss, a whiteout that isn't represented by a 0,0 chardev or a 486 * fallthrough marker in an opaque directory. 487 * 488 * Note! (1) This should be used *only* by a filesystem to examine its own 489 * dentries. It should not be used to look at some other filesystem's 490 * dentries. (2) It should also be used in combination with d_inode() to get 491 * the inode. (3) The dentry may have something attached to ->d_lower and the 492 * type field of the flags may be set to something other than miss or whiteout. 493 */ 494 static inline bool d_really_is_negative(const struct dentry *dentry) 495 { 496 return dentry->d_inode == NULL; 497 } 498 499 /** 500 * d_really_is_positive - Determine if a dentry is really positive (ignoring fallthroughs) 501 * @dentry: The dentry in question 502 * 503 * Returns true if the dentry represents a name that maps to an inode 504 * (ie. ->d_inode is not NULL). The dentry might still represent a whiteout if 505 * that is represented on medium as a 0,0 chardev. 506 * 507 * Note! (1) This should be used *only* by a filesystem to examine its own 508 * dentries. It should not be used to look at some other filesystem's 509 * dentries. (2) It should also be used in combination with d_inode() to get 510 * the inode. 511 */ 512 static inline bool d_really_is_positive(const struct dentry *dentry) 513 { 514 return dentry->d_inode != NULL; 515 } 516 517 static inline int simple_positive(const struct dentry *dentry) 518 { 519 return d_really_is_positive(dentry) && !d_unhashed(dentry); 520 } 521 522 unsigned long vfs_pressure_ratio(unsigned long val); 523 524 /** 525 * d_inode - Get the actual inode of this dentry 526 * @dentry: The dentry to query 527 * 528 * This is the helper normal filesystems should use to get at their own inodes 529 * in their own dentries and ignore the layering superimposed upon them. 530 */ 531 static inline struct inode *d_inode(const struct dentry *dentry) 532 { 533 return dentry->d_inode; 534 } 535 536 /** 537 * d_inode_rcu - Get the actual inode of this dentry with READ_ONCE() 538 * @dentry: The dentry to query 539 * 540 * This is the helper normal filesystems should use to get at their own inodes 541 * in their own dentries and ignore the layering superimposed upon them. 542 */ 543 static inline struct inode *d_inode_rcu(const struct dentry *dentry) 544 { 545 return READ_ONCE(dentry->d_inode); 546 } 547 548 /** 549 * d_backing_inode - Get upper or lower inode we should be using 550 * @upper: The upper layer 551 * 552 * This is the helper that should be used to get at the inode that will be used 553 * if this dentry were to be opened as a file. The inode may be on the upper 554 * dentry or it may be on a lower dentry pinned by the upper. 555 * 556 * Normal filesystems should not use this to access their own inodes. 557 */ 558 static inline struct inode *d_backing_inode(const struct dentry *upper) 559 { 560 struct inode *inode = upper->d_inode; 561 562 return inode; 563 } 564 565 /** 566 * d_real - Return the real dentry 567 * @dentry: the dentry to query 568 * @type: the type of real dentry (data or metadata) 569 * 570 * If dentry is on a union/overlay, then return the underlying, real dentry. 571 * Otherwise return the dentry itself. 572 * 573 * See also: Documentation/filesystems/vfs.rst 574 */ 575 static inline struct dentry *d_real(struct dentry *dentry, enum d_real_type type) 576 { 577 if (unlikely(dentry->d_flags & DCACHE_OP_REAL)) 578 return dentry->d_op->d_real(dentry, type); 579 else 580 return dentry; 581 } 582 583 /** 584 * d_real_inode - Return the real inode hosting the data 585 * @dentry: The dentry to query 586 * 587 * If dentry is on a union/overlay, then return the underlying, real inode. 588 * Otherwise return d_inode(). 589 */ 590 static inline struct inode *d_real_inode(const struct dentry *dentry) 591 { 592 /* This usage of d_real() results in const dentry */ 593 return d_inode(d_real((struct dentry *) dentry, D_REAL_DATA)); 594 } 595 596 struct name_snapshot { 597 struct qstr name; 598 union shortname_store inline_name; 599 }; 600 void take_dentry_name_snapshot(struct name_snapshot *, struct dentry *); 601 void release_dentry_name_snapshot(struct name_snapshot *); 602 603 static inline struct dentry *d_first_child(const struct dentry *dentry) 604 { 605 return hlist_entry_safe(dentry->d_children.first, struct dentry, d_sib); 606 } 607 608 static inline struct dentry *d_next_sibling(const struct dentry *dentry) 609 { 610 return hlist_entry_safe(dentry->d_sib.next, struct dentry, d_sib); 611 } 612 613 #endif /* __LINUX_DCACHE_H */ 614