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_LEN 40 /* 192 bytes */ 73 #else 74 # ifdef CONFIG_SMP 75 # define DNAME_INLINE_LEN 36 /* 128 bytes */ 76 # else 77 # define DNAME_INLINE_LEN 44 /* 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_spinlock_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 /* --- cacheline 1 boundary (64 bytes) was 32 bytes ago --- */ 94 95 /* Ref lookup also touches following */ 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 /* --- cacheline 2 boundary (128 bytes) --- */ 101 struct lockref d_lockref; /* per-dentry lock and refcount 102 * keep separate from RCU lookup area if 103 * possible! 104 */ 105 106 union { 107 struct list_head d_lru; /* LRU list */ 108 wait_queue_head_t *d_wait; /* in-lookup ones only */ 109 }; 110 struct hlist_node d_sib; /* child of parent list */ 111 struct hlist_head d_children; /* our children */ 112 /* 113 * d_alias and d_rcu can share memory 114 */ 115 union { 116 struct hlist_node d_alias; /* inode alias list */ 117 struct hlist_bl_node d_in_lookup_hash; /* only for in-lookup ones */ 118 struct rcu_head d_rcu; 119 } d_u; 120 }; 121 122 /* 123 * dentry->d_lock spinlock nesting subclasses: 124 * 125 * 0: normal 126 * 1: nested 127 */ 128 enum dentry_d_lock_class 129 { 130 DENTRY_D_LOCK_NORMAL, /* implicitly used by plain spin_lock() APIs. */ 131 DENTRY_D_LOCK_NESTED 132 }; 133 134 enum d_real_type { 135 D_REAL_DATA, 136 D_REAL_METADATA, 137 }; 138 139 struct dentry_operations { 140 int (*d_revalidate)(struct dentry *, unsigned int); 141 int (*d_weak_revalidate)(struct dentry *, unsigned int); 142 int (*d_hash)(const struct dentry *, struct qstr *); 143 int (*d_compare)(const struct dentry *, 144 unsigned int, const char *, const struct qstr *); 145 int (*d_delete)(const struct dentry *); 146 int (*d_init)(struct dentry *); 147 void (*d_release)(struct dentry *); 148 void (*d_prune)(struct dentry *); 149 void (*d_iput)(struct dentry *, struct inode *); 150 char *(*d_dname)(struct dentry *, char *, int); 151 struct vfsmount *(*d_automount)(struct path *); 152 int (*d_manage)(const struct path *, bool); 153 struct dentry *(*d_real)(struct dentry *, enum d_real_type type); 154 } ____cacheline_aligned; 155 156 /* 157 * Locking rules for dentry_operations callbacks are to be found in 158 * Documentation/filesystems/locking.rst. Keep it updated! 159 * 160 * FUrther descriptions are found in Documentation/filesystems/vfs.rst. 161 * Keep it updated too! 162 */ 163 164 /* d_flags entries */ 165 #define DCACHE_OP_HASH BIT(0) 166 #define DCACHE_OP_COMPARE BIT(1) 167 #define DCACHE_OP_REVALIDATE BIT(2) 168 #define DCACHE_OP_DELETE BIT(3) 169 #define DCACHE_OP_PRUNE BIT(4) 170 171 #define DCACHE_DISCONNECTED BIT(5) 172 /* This dentry is possibly not currently connected to the dcache tree, in 173 * which case its parent will either be itself, or will have this flag as 174 * well. nfsd will not use a dentry with this bit set, but will first 175 * endeavour to clear the bit either by discovering that it is connected, 176 * or by performing lookup operations. Any filesystem which supports 177 * nfsd_operations MUST have a lookup function which, if it finds a 178 * directory inode with a DCACHE_DISCONNECTED dentry, will d_move that 179 * dentry into place and return that dentry rather than the passed one, 180 * typically using d_splice_alias. */ 181 182 #define DCACHE_REFERENCED BIT(6) /* Recently used, don't discard. */ 183 184 #define DCACHE_DONTCACHE BIT(7) /* Purge from memory on final dput() */ 185 186 #define DCACHE_CANT_MOUNT BIT(8) 187 #define DCACHE_GENOCIDE BIT(9) 188 #define DCACHE_SHRINK_LIST BIT(10) 189 190 #define DCACHE_OP_WEAK_REVALIDATE BIT(11) 191 192 #define DCACHE_NFSFS_RENAMED BIT(12) 193 /* this dentry has been "silly renamed" and has to be deleted on the last 194 * dput() */ 195 #define DCACHE_FSNOTIFY_PARENT_WATCHED BIT(14) 196 /* Parent inode is watched by some fsnotify listener */ 197 198 #define DCACHE_DENTRY_KILLED BIT(15) 199 200 #define DCACHE_MOUNTED BIT(16) /* is a mountpoint */ 201 #define DCACHE_NEED_AUTOMOUNT BIT(17) /* handle automount on this dir */ 202 #define DCACHE_MANAGE_TRANSIT BIT(18) /* manage transit from this dirent */ 203 #define DCACHE_MANAGED_DENTRY \ 204 (DCACHE_MOUNTED|DCACHE_NEED_AUTOMOUNT|DCACHE_MANAGE_TRANSIT) 205 206 #define DCACHE_LRU_LIST BIT(19) 207 208 #define DCACHE_ENTRY_TYPE (7 << 20) /* bits 20..22 are for storing type: */ 209 #define DCACHE_MISS_TYPE (0 << 20) /* Negative dentry */ 210 #define DCACHE_WHITEOUT_TYPE (1 << 20) /* Whiteout dentry (stop pathwalk) */ 211 #define DCACHE_DIRECTORY_TYPE (2 << 20) /* Normal directory */ 212 #define DCACHE_AUTODIR_TYPE (3 << 20) /* Lookupless directory (presumed automount) */ 213 #define DCACHE_REGULAR_TYPE (4 << 20) /* Regular file type */ 214 #define DCACHE_SPECIAL_TYPE (5 << 20) /* Other file type */ 215 #define DCACHE_SYMLINK_TYPE (6 << 20) /* Symlink */ 216 217 #define DCACHE_NOKEY_NAME BIT(25) /* Encrypted name encoded without key */ 218 #define DCACHE_OP_REAL BIT(26) 219 220 #define DCACHE_PAR_LOOKUP BIT(28) /* being looked up (with parent locked shared) */ 221 #define DCACHE_DENTRY_CURSOR BIT(29) 222 #define DCACHE_NORCU BIT(30) /* No RCU delay for freeing */ 223 224 extern seqlock_t rename_lock; 225 226 /* 227 * These are the low-level FS interfaces to the dcache.. 228 */ 229 extern void d_instantiate(struct dentry *, struct inode *); 230 extern void d_instantiate_new(struct dentry *, struct inode *); 231 extern void __d_drop(struct dentry *dentry); 232 extern void d_drop(struct dentry *dentry); 233 extern void d_delete(struct dentry *); 234 extern void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op); 235 236 /* allocate/de-allocate */ 237 extern struct dentry * d_alloc(struct dentry *, const struct qstr *); 238 extern struct dentry * d_alloc_anon(struct super_block *); 239 extern struct dentry * d_alloc_parallel(struct dentry *, const struct qstr *, 240 wait_queue_head_t *); 241 extern struct dentry * d_splice_alias(struct inode *, struct dentry *); 242 extern struct dentry * d_add_ci(struct dentry *, struct inode *, struct qstr *); 243 extern bool d_same_name(const struct dentry *dentry, const struct dentry *parent, 244 const struct qstr *name); 245 extern struct dentry * d_exact_alias(struct dentry *, struct inode *); 246 extern struct dentry *d_find_any_alias(struct inode *inode); 247 extern struct dentry * d_obtain_alias(struct inode *); 248 extern struct dentry * d_obtain_root(struct inode *); 249 extern void shrink_dcache_sb(struct super_block *); 250 extern void shrink_dcache_parent(struct dentry *); 251 extern void d_invalidate(struct dentry *); 252 253 /* only used at mount-time */ 254 extern struct dentry * d_make_root(struct inode *); 255 256 extern void d_mark_tmpfile(struct file *, struct inode *); 257 extern void d_tmpfile(struct file *, struct inode *); 258 259 extern struct dentry *d_find_alias(struct inode *); 260 extern void d_prune_aliases(struct inode *); 261 262 extern struct dentry *d_find_alias_rcu(struct inode *); 263 264 /* test whether we have any submounts in a subdir tree */ 265 extern int path_has_submounts(const struct path *); 266 267 /* 268 * This adds the entry to the hash queues. 269 */ 270 extern void d_rehash(struct dentry *); 271 272 extern void d_add(struct dentry *, struct inode *); 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 extern struct dentry *d_lookup(const struct dentry *, const struct qstr *); 280 extern struct dentry *d_hash_and_lookup(struct dentry *, struct qstr *); 281 282 static inline unsigned d_count(const struct dentry *dentry) 283 { 284 return dentry->d_lockref.count; 285 } 286 287 ino_t d_parent_ino(struct dentry *dentry); 288 289 /* 290 * helper function for dentry_operations.d_dname() members 291 */ 292 extern __printf(3, 4) 293 char *dynamic_dname(char *, int, const char *, ...); 294 295 extern char *__d_path(const struct path *, const struct path *, char *, int); 296 extern char *d_absolute_path(const struct path *, char *, int); 297 extern char *d_path(const struct path *, char *, int); 298 extern char *dentry_path_raw(const struct dentry *, char *, int); 299 extern char *dentry_path(const struct dentry *, char *, int); 300 301 /* Allocation counts.. */ 302 303 /** 304 * dget_dlock - get a reference to a dentry 305 * @dentry: dentry to get a reference to 306 * 307 * Given a live dentry, increment the reference count and return the dentry. 308 * Caller must hold @dentry->d_lock. Making sure that dentry is alive is 309 * caller's resonsibility. There are many conditions sufficient to guarantee 310 * that; e.g. anything with non-negative refcount is alive, so's anything 311 * hashed, anything positive, anyone's parent, etc. 312 */ 313 static inline struct dentry *dget_dlock(struct dentry *dentry) 314 { 315 dentry->d_lockref.count++; 316 return dentry; 317 } 318 319 320 /** 321 * dget - get a reference to a dentry 322 * @dentry: dentry to get a reference to 323 * 324 * Given a dentry or %NULL pointer increment the reference count 325 * if appropriate and return the dentry. A dentry will not be 326 * destroyed when it has references. Conversely, a dentry with 327 * no references can disappear for any number of reasons, starting 328 * with memory pressure. In other words, that primitive is 329 * used to clone an existing reference; using it on something with 330 * zero refcount is a bug. 331 * 332 * NOTE: it will spin if @dentry->d_lock is held. From the deadlock 333 * avoidance point of view it is equivalent to spin_lock()/increment 334 * refcount/spin_unlock(), so calling it under @dentry->d_lock is 335 * always a bug; so's calling it under ->d_lock on any of its descendents. 336 * 337 */ 338 static inline struct dentry *dget(struct dentry *dentry) 339 { 340 if (dentry) 341 lockref_get(&dentry->d_lockref); 342 return dentry; 343 } 344 345 extern struct dentry *dget_parent(struct dentry *dentry); 346 347 /** 348 * d_unhashed - is dentry hashed 349 * @dentry: entry to check 350 * 351 * Returns true if the dentry passed is not currently hashed. 352 */ 353 static inline int d_unhashed(const struct dentry *dentry) 354 { 355 return hlist_bl_unhashed(&dentry->d_hash); 356 } 357 358 static inline int d_unlinked(const struct dentry *dentry) 359 { 360 return d_unhashed(dentry) && !IS_ROOT(dentry); 361 } 362 363 static inline int cant_mount(const struct dentry *dentry) 364 { 365 return (dentry->d_flags & DCACHE_CANT_MOUNT); 366 } 367 368 static inline void dont_mount(struct dentry *dentry) 369 { 370 spin_lock(&dentry->d_lock); 371 dentry->d_flags |= DCACHE_CANT_MOUNT; 372 spin_unlock(&dentry->d_lock); 373 } 374 375 extern void __d_lookup_unhash_wake(struct dentry *dentry); 376 377 static inline int d_in_lookup(const struct dentry *dentry) 378 { 379 return dentry->d_flags & DCACHE_PAR_LOOKUP; 380 } 381 382 static inline void d_lookup_done(struct dentry *dentry) 383 { 384 if (unlikely(d_in_lookup(dentry))) 385 __d_lookup_unhash_wake(dentry); 386 } 387 388 extern void dput(struct dentry *); 389 390 static inline bool d_managed(const struct dentry *dentry) 391 { 392 return dentry->d_flags & DCACHE_MANAGED_DENTRY; 393 } 394 395 static inline bool d_mountpoint(const struct dentry *dentry) 396 { 397 return dentry->d_flags & DCACHE_MOUNTED; 398 } 399 400 /* 401 * Directory cache entry type accessor functions. 402 */ 403 static inline unsigned __d_entry_type(const struct dentry *dentry) 404 { 405 return dentry->d_flags & DCACHE_ENTRY_TYPE; 406 } 407 408 static inline bool d_is_miss(const struct dentry *dentry) 409 { 410 return __d_entry_type(dentry) == DCACHE_MISS_TYPE; 411 } 412 413 static inline bool d_is_whiteout(const struct dentry *dentry) 414 { 415 return __d_entry_type(dentry) == DCACHE_WHITEOUT_TYPE; 416 } 417 418 static inline bool d_can_lookup(const struct dentry *dentry) 419 { 420 return __d_entry_type(dentry) == DCACHE_DIRECTORY_TYPE; 421 } 422 423 static inline bool d_is_autodir(const struct dentry *dentry) 424 { 425 return __d_entry_type(dentry) == DCACHE_AUTODIR_TYPE; 426 } 427 428 static inline bool d_is_dir(const struct dentry *dentry) 429 { 430 return d_can_lookup(dentry) || d_is_autodir(dentry); 431 } 432 433 static inline bool d_is_symlink(const struct dentry *dentry) 434 { 435 return __d_entry_type(dentry) == DCACHE_SYMLINK_TYPE; 436 } 437 438 static inline bool d_is_reg(const struct dentry *dentry) 439 { 440 return __d_entry_type(dentry) == DCACHE_REGULAR_TYPE; 441 } 442 443 static inline bool d_is_special(const struct dentry *dentry) 444 { 445 return __d_entry_type(dentry) == DCACHE_SPECIAL_TYPE; 446 } 447 448 static inline bool d_is_file(const struct dentry *dentry) 449 { 450 return d_is_reg(dentry) || d_is_special(dentry); 451 } 452 453 static inline bool d_is_negative(const struct dentry *dentry) 454 { 455 // TODO: check d_is_whiteout(dentry) also. 456 return d_is_miss(dentry); 457 } 458 459 static inline bool d_flags_negative(unsigned flags) 460 { 461 return (flags & DCACHE_ENTRY_TYPE) == DCACHE_MISS_TYPE; 462 } 463 464 static inline bool d_is_positive(const struct dentry *dentry) 465 { 466 return !d_is_negative(dentry); 467 } 468 469 /** 470 * d_really_is_negative - Determine if a dentry is really negative (ignoring fallthroughs) 471 * @dentry: The dentry in question 472 * 473 * Returns true if the dentry represents either an absent name or a name that 474 * doesn't map to an inode (ie. ->d_inode is NULL). The dentry could represent 475 * a true miss, a whiteout that isn't represented by a 0,0 chardev or a 476 * fallthrough marker in an opaque directory. 477 * 478 * Note! (1) This should be used *only* by a filesystem to examine its own 479 * dentries. It should not be used to look at some other filesystem's 480 * dentries. (2) It should also be used in combination with d_inode() to get 481 * the inode. (3) The dentry may have something attached to ->d_lower and the 482 * type field of the flags may be set to something other than miss or whiteout. 483 */ 484 static inline bool d_really_is_negative(const struct dentry *dentry) 485 { 486 return dentry->d_inode == NULL; 487 } 488 489 /** 490 * d_really_is_positive - Determine if a dentry is really positive (ignoring fallthroughs) 491 * @dentry: The dentry in question 492 * 493 * Returns true if the dentry represents a name that maps to an inode 494 * (ie. ->d_inode is not NULL). The dentry might still represent a whiteout if 495 * that is represented on medium as a 0,0 chardev. 496 * 497 * Note! (1) This should be used *only* by a filesystem to examine its own 498 * dentries. It should not be used to look at some other filesystem's 499 * dentries. (2) It should also be used in combination with d_inode() to get 500 * the inode. 501 */ 502 static inline bool d_really_is_positive(const struct dentry *dentry) 503 { 504 return dentry->d_inode != NULL; 505 } 506 507 static inline int simple_positive(const struct dentry *dentry) 508 { 509 return d_really_is_positive(dentry) && !d_unhashed(dentry); 510 } 511 512 extern int sysctl_vfs_cache_pressure; 513 514 static inline unsigned long vfs_pressure_ratio(unsigned long val) 515 { 516 return mult_frac(val, sysctl_vfs_cache_pressure, 100); 517 } 518 519 /** 520 * d_inode - Get the actual inode of this dentry 521 * @dentry: The dentry to query 522 * 523 * This is the helper normal filesystems should use to get at their own inodes 524 * in their own dentries and ignore the layering superimposed upon them. 525 */ 526 static inline struct inode *d_inode(const struct dentry *dentry) 527 { 528 return dentry->d_inode; 529 } 530 531 /** 532 * d_inode_rcu - Get the actual inode of this dentry with READ_ONCE() 533 * @dentry: The dentry to query 534 * 535 * This is the helper normal filesystems should use to get at their own inodes 536 * in their own dentries and ignore the layering superimposed upon them. 537 */ 538 static inline struct inode *d_inode_rcu(const struct dentry *dentry) 539 { 540 return READ_ONCE(dentry->d_inode); 541 } 542 543 /** 544 * d_backing_inode - Get upper or lower inode we should be using 545 * @upper: The upper layer 546 * 547 * This is the helper that should be used to get at the inode that will be used 548 * if this dentry were to be opened as a file. The inode may be on the upper 549 * dentry or it may be on a lower dentry pinned by the upper. 550 * 551 * Normal filesystems should not use this to access their own inodes. 552 */ 553 static inline struct inode *d_backing_inode(const struct dentry *upper) 554 { 555 struct inode *inode = upper->d_inode; 556 557 return inode; 558 } 559 560 /** 561 * d_real - Return the real dentry 562 * @dentry: the dentry to query 563 * @type: the type of real dentry (data or metadata) 564 * 565 * If dentry is on a union/overlay, then return the underlying, real dentry. 566 * Otherwise return the dentry itself. 567 * 568 * See also: Documentation/filesystems/vfs.rst 569 */ 570 static inline struct dentry *d_real(struct dentry *dentry, enum d_real_type type) 571 { 572 if (unlikely(dentry->d_flags & DCACHE_OP_REAL)) 573 return dentry->d_op->d_real(dentry, type); 574 else 575 return dentry; 576 } 577 578 /** 579 * d_real_inode - Return the real inode hosting the data 580 * @dentry: The dentry to query 581 * 582 * If dentry is on a union/overlay, then return the underlying, real inode. 583 * Otherwise return d_inode(). 584 */ 585 static inline struct inode *d_real_inode(const struct dentry *dentry) 586 { 587 /* This usage of d_real() results in const dentry */ 588 return d_inode(d_real((struct dentry *) dentry, D_REAL_DATA)); 589 } 590 591 struct name_snapshot { 592 struct qstr name; 593 unsigned char inline_name[DNAME_INLINE_LEN]; 594 }; 595 void take_dentry_name_snapshot(struct name_snapshot *, struct dentry *); 596 void release_dentry_name_snapshot(struct name_snapshot *); 597 598 static inline struct dentry *d_first_child(const struct dentry *dentry) 599 { 600 return hlist_entry_safe(dentry->d_children.first, struct dentry, d_sib); 601 } 602 603 static inline struct dentry *d_next_sibling(const struct dentry *dentry) 604 { 605 return hlist_entry_safe(dentry->d_sib.next, struct dentry, d_sib); 606 } 607 608 #endif /* __LINUX_DCACHE_H */ 609