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 #define d_lock d_lockref.lock 83 84 struct dentry { 85 /* RCU lookup touched fields */ 86 unsigned int d_flags; /* protected by d_lock */ 87 seqcount_spinlock_t d_seq; /* per dentry seqlock */ 88 struct hlist_bl_node d_hash; /* lookup hash list */ 89 struct dentry *d_parent; /* parent directory */ 90 struct qstr d_name; 91 struct inode *d_inode; /* Where the name belongs to - NULL is 92 * negative */ 93 unsigned char d_iname[DNAME_INLINE_LEN]; /* small names */ 94 /* --- cacheline 1 boundary (64 bytes) was 32 bytes ago --- */ 95 96 /* Ref lookup also touches following */ 97 const struct dentry_operations *d_op; 98 struct super_block *d_sb; /* The root of the dentry tree */ 99 unsigned long d_time; /* used by d_revalidate */ 100 void *d_fsdata; /* fs-specific data */ 101 /* --- cacheline 2 boundary (128 bytes) --- */ 102 struct lockref d_lockref; /* per-dentry lock and refcount 103 * keep separate from RCU lookup area if 104 * possible! 105 */ 106 107 union { 108 struct list_head d_lru; /* LRU list */ 109 wait_queue_head_t *d_wait; /* in-lookup ones only */ 110 }; 111 struct hlist_node d_sib; /* child of parent list */ 112 struct hlist_head d_children; /* our children */ 113 /* 114 * d_alias and d_rcu can share memory 115 */ 116 union { 117 struct hlist_node d_alias; /* inode alias list */ 118 struct hlist_bl_node d_in_lookup_hash; /* only for in-lookup ones */ 119 struct rcu_head d_rcu; 120 } d_u; 121 }; 122 123 /* 124 * dentry->d_lock spinlock nesting subclasses: 125 * 126 * 0: normal 127 * 1: nested 128 */ 129 enum dentry_d_lock_class 130 { 131 DENTRY_D_LOCK_NORMAL, /* implicitly used by plain spin_lock() APIs. */ 132 DENTRY_D_LOCK_NESTED 133 }; 134 135 enum d_real_type { 136 D_REAL_DATA, 137 D_REAL_METADATA, 138 }; 139 140 struct dentry_operations { 141 int (*d_revalidate)(struct dentry *, unsigned int); 142 int (*d_weak_revalidate)(struct dentry *, unsigned int); 143 int (*d_hash)(const struct dentry *, struct qstr *); 144 int (*d_compare)(const struct dentry *, 145 unsigned int, const char *, const struct qstr *); 146 int (*d_delete)(const struct dentry *); 147 int (*d_init)(struct dentry *); 148 void (*d_release)(struct dentry *); 149 void (*d_prune)(struct dentry *); 150 void (*d_iput)(struct dentry *, struct inode *); 151 char *(*d_dname)(struct dentry *, char *, int); 152 struct vfsmount *(*d_automount)(struct path *); 153 int (*d_manage)(const struct path *, bool); 154 struct dentry *(*d_real)(struct dentry *, enum d_real_type type); 155 } ____cacheline_aligned; 156 157 /* 158 * Locking rules for dentry_operations callbacks are to be found in 159 * Documentation/filesystems/locking.rst. Keep it updated! 160 * 161 * FUrther descriptions are found in Documentation/filesystems/vfs.rst. 162 * Keep it updated too! 163 */ 164 165 /* d_flags entries */ 166 #define DCACHE_OP_HASH BIT(0) 167 #define DCACHE_OP_COMPARE BIT(1) 168 #define DCACHE_OP_REVALIDATE BIT(2) 169 #define DCACHE_OP_DELETE BIT(3) 170 #define DCACHE_OP_PRUNE BIT(4) 171 172 #define DCACHE_DISCONNECTED BIT(5) 173 /* This dentry is possibly not currently connected to the dcache tree, in 174 * which case its parent will either be itself, or will have this flag as 175 * well. nfsd will not use a dentry with this bit set, but will first 176 * endeavour to clear the bit either by discovering that it is connected, 177 * or by performing lookup operations. Any filesystem which supports 178 * nfsd_operations MUST have a lookup function which, if it finds a 179 * directory inode with a DCACHE_DISCONNECTED dentry, will d_move that 180 * dentry into place and return that dentry rather than the passed one, 181 * typically using d_splice_alias. */ 182 183 #define DCACHE_REFERENCED BIT(6) /* Recently used, don't discard. */ 184 185 #define DCACHE_DONTCACHE BIT(7) /* Purge from memory on final dput() */ 186 187 #define DCACHE_CANT_MOUNT BIT(8) 188 #define DCACHE_GENOCIDE BIT(9) 189 #define DCACHE_SHRINK_LIST BIT(10) 190 191 #define DCACHE_OP_WEAK_REVALIDATE BIT(11) 192 193 #define DCACHE_NFSFS_RENAMED BIT(12) 194 /* this dentry has been "silly renamed" and has to be deleted on the last 195 * dput() */ 196 #define DCACHE_FSNOTIFY_PARENT_WATCHED BIT(14) 197 /* Parent inode is watched by some fsnotify listener */ 198 199 #define DCACHE_DENTRY_KILLED BIT(15) 200 201 #define DCACHE_MOUNTED BIT(16) /* is a mountpoint */ 202 #define DCACHE_NEED_AUTOMOUNT BIT(17) /* handle automount on this dir */ 203 #define DCACHE_MANAGE_TRANSIT BIT(18) /* manage transit from this dirent */ 204 #define DCACHE_MANAGED_DENTRY \ 205 (DCACHE_MOUNTED|DCACHE_NEED_AUTOMOUNT|DCACHE_MANAGE_TRANSIT) 206 207 #define DCACHE_LRU_LIST BIT(19) 208 209 #define DCACHE_ENTRY_TYPE (7 << 20) /* bits 20..22 are for storing type: */ 210 #define DCACHE_MISS_TYPE (0 << 20) /* Negative dentry */ 211 #define DCACHE_WHITEOUT_TYPE (1 << 20) /* Whiteout dentry (stop pathwalk) */ 212 #define DCACHE_DIRECTORY_TYPE (2 << 20) /* Normal directory */ 213 #define DCACHE_AUTODIR_TYPE (3 << 20) /* Lookupless directory (presumed automount) */ 214 #define DCACHE_REGULAR_TYPE (4 << 20) /* Regular file type */ 215 #define DCACHE_SPECIAL_TYPE (5 << 20) /* Other file type */ 216 #define DCACHE_SYMLINK_TYPE (6 << 20) /* Symlink */ 217 218 #define DCACHE_NOKEY_NAME BIT(25) /* Encrypted name encoded without key */ 219 #define DCACHE_OP_REAL BIT(26) 220 221 #define DCACHE_PAR_LOOKUP BIT(28) /* being looked up (with parent locked shared) */ 222 #define DCACHE_DENTRY_CURSOR BIT(29) 223 #define DCACHE_NORCU BIT(30) /* No RCU delay for freeing */ 224 225 extern seqlock_t rename_lock; 226 227 /* 228 * These are the low-level FS interfaces to the dcache.. 229 */ 230 extern void d_instantiate(struct dentry *, struct inode *); 231 extern void d_instantiate_new(struct dentry *, struct inode *); 232 extern void __d_drop(struct dentry *dentry); 233 extern void d_drop(struct dentry *dentry); 234 extern void d_delete(struct dentry *); 235 extern void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op); 236 237 /* allocate/de-allocate */ 238 extern struct dentry * d_alloc(struct dentry *, const struct qstr *); 239 extern struct dentry * d_alloc_anon(struct super_block *); 240 extern struct dentry * d_alloc_parallel(struct dentry *, const struct qstr *, 241 wait_queue_head_t *); 242 extern struct dentry * d_splice_alias(struct inode *, struct dentry *); 243 extern struct dentry * d_add_ci(struct dentry *, struct inode *, struct qstr *); 244 extern bool d_same_name(const struct dentry *dentry, const struct dentry *parent, 245 const struct qstr *name); 246 extern struct dentry * d_exact_alias(struct dentry *, struct inode *); 247 extern struct dentry *d_find_any_alias(struct inode *inode); 248 extern struct dentry * d_obtain_alias(struct inode *); 249 extern struct dentry * d_obtain_root(struct inode *); 250 extern void shrink_dcache_sb(struct super_block *); 251 extern void shrink_dcache_parent(struct dentry *); 252 extern void d_invalidate(struct dentry *); 253 254 /* only used at mount-time */ 255 extern struct dentry * d_make_root(struct inode *); 256 257 extern void d_mark_tmpfile(struct file *, struct inode *); 258 extern void d_tmpfile(struct file *, struct inode *); 259 260 extern struct dentry *d_find_alias(struct inode *); 261 extern void d_prune_aliases(struct inode *); 262 263 extern struct dentry *d_find_alias_rcu(struct inode *); 264 265 /* test whether we have any submounts in a subdir tree */ 266 extern int path_has_submounts(const struct path *); 267 268 /* 269 * This adds the entry to the hash queues. 270 */ 271 extern void d_rehash(struct dentry *); 272 273 extern void d_add(struct dentry *, struct inode *); 274 275 /* used for rename() and baskets */ 276 extern void d_move(struct dentry *, struct dentry *); 277 extern void d_exchange(struct dentry *, struct dentry *); 278 extern struct dentry *d_ancestor(struct dentry *, struct dentry *); 279 280 extern struct dentry *d_lookup(const struct dentry *, const struct qstr *); 281 extern struct dentry *d_hash_and_lookup(struct dentry *, struct qstr *); 282 283 static inline unsigned d_count(const struct dentry *dentry) 284 { 285 return dentry->d_lockref.count; 286 } 287 288 ino_t d_parent_ino(struct dentry *dentry); 289 290 /* 291 * helper function for dentry_operations.d_dname() members 292 */ 293 extern __printf(3, 4) 294 char *dynamic_dname(char *, int, const char *, ...); 295 296 extern char *__d_path(const struct path *, const struct path *, char *, int); 297 extern char *d_absolute_path(const struct path *, char *, int); 298 extern char *d_path(const struct path *, char *, int); 299 extern char *dentry_path_raw(const struct dentry *, char *, int); 300 extern char *dentry_path(const struct dentry *, char *, int); 301 302 /* Allocation counts.. */ 303 304 /** 305 * dget_dlock - get a reference to a dentry 306 * @dentry: dentry to get a reference to 307 * 308 * Given a live dentry, increment the reference count and return the dentry. 309 * Caller must hold @dentry->d_lock. Making sure that dentry is alive is 310 * caller's resonsibility. There are many conditions sufficient to guarantee 311 * that; e.g. anything with non-negative refcount is alive, so's anything 312 * hashed, anything positive, anyone's parent, etc. 313 */ 314 static inline struct dentry *dget_dlock(struct dentry *dentry) 315 { 316 dentry->d_lockref.count++; 317 return dentry; 318 } 319 320 321 /** 322 * dget - get a reference to a dentry 323 * @dentry: dentry to get a reference to 324 * 325 * Given a dentry or %NULL pointer increment the reference count 326 * if appropriate and return the dentry. A dentry will not be 327 * destroyed when it has references. Conversely, a dentry with 328 * no references can disappear for any number of reasons, starting 329 * with memory pressure. In other words, that primitive is 330 * used to clone an existing reference; using it on something with 331 * zero refcount is a bug. 332 * 333 * NOTE: it will spin if @dentry->d_lock is held. From the deadlock 334 * avoidance point of view it is equivalent to spin_lock()/increment 335 * refcount/spin_unlock(), so calling it under @dentry->d_lock is 336 * always a bug; so's calling it under ->d_lock on any of its descendents. 337 * 338 */ 339 static inline struct dentry *dget(struct dentry *dentry) 340 { 341 if (dentry) 342 lockref_get(&dentry->d_lockref); 343 return dentry; 344 } 345 346 extern struct dentry *dget_parent(struct dentry *dentry); 347 348 /** 349 * d_unhashed - is dentry hashed 350 * @dentry: entry to check 351 * 352 * Returns true if the dentry passed is not currently hashed. 353 */ 354 static inline int d_unhashed(const struct dentry *dentry) 355 { 356 return hlist_bl_unhashed(&dentry->d_hash); 357 } 358 359 static inline int d_unlinked(const struct dentry *dentry) 360 { 361 return d_unhashed(dentry) && !IS_ROOT(dentry); 362 } 363 364 static inline int cant_mount(const struct dentry *dentry) 365 { 366 return (dentry->d_flags & DCACHE_CANT_MOUNT); 367 } 368 369 static inline void dont_mount(struct dentry *dentry) 370 { 371 spin_lock(&dentry->d_lock); 372 dentry->d_flags |= DCACHE_CANT_MOUNT; 373 spin_unlock(&dentry->d_lock); 374 } 375 376 extern void __d_lookup_unhash_wake(struct dentry *dentry); 377 378 static inline int d_in_lookup(const struct dentry *dentry) 379 { 380 return dentry->d_flags & DCACHE_PAR_LOOKUP; 381 } 382 383 static inline void d_lookup_done(struct dentry *dentry) 384 { 385 if (unlikely(d_in_lookup(dentry))) 386 __d_lookup_unhash_wake(dentry); 387 } 388 389 extern void dput(struct dentry *); 390 391 static inline bool d_managed(const struct dentry *dentry) 392 { 393 return dentry->d_flags & DCACHE_MANAGED_DENTRY; 394 } 395 396 static inline bool d_mountpoint(const struct dentry *dentry) 397 { 398 return dentry->d_flags & DCACHE_MOUNTED; 399 } 400 401 /* 402 * Directory cache entry type accessor functions. 403 */ 404 static inline unsigned __d_entry_type(const struct dentry *dentry) 405 { 406 return dentry->d_flags & DCACHE_ENTRY_TYPE; 407 } 408 409 static inline bool d_is_miss(const struct dentry *dentry) 410 { 411 return __d_entry_type(dentry) == DCACHE_MISS_TYPE; 412 } 413 414 static inline bool d_is_whiteout(const struct dentry *dentry) 415 { 416 return __d_entry_type(dentry) == DCACHE_WHITEOUT_TYPE; 417 } 418 419 static inline bool d_can_lookup(const struct dentry *dentry) 420 { 421 return __d_entry_type(dentry) == DCACHE_DIRECTORY_TYPE; 422 } 423 424 static inline bool d_is_autodir(const struct dentry *dentry) 425 { 426 return __d_entry_type(dentry) == DCACHE_AUTODIR_TYPE; 427 } 428 429 static inline bool d_is_dir(const struct dentry *dentry) 430 { 431 return d_can_lookup(dentry) || d_is_autodir(dentry); 432 } 433 434 static inline bool d_is_symlink(const struct dentry *dentry) 435 { 436 return __d_entry_type(dentry) == DCACHE_SYMLINK_TYPE; 437 } 438 439 static inline bool d_is_reg(const struct dentry *dentry) 440 { 441 return __d_entry_type(dentry) == DCACHE_REGULAR_TYPE; 442 } 443 444 static inline bool d_is_special(const struct dentry *dentry) 445 { 446 return __d_entry_type(dentry) == DCACHE_SPECIAL_TYPE; 447 } 448 449 static inline bool d_is_file(const struct dentry *dentry) 450 { 451 return d_is_reg(dentry) || d_is_special(dentry); 452 } 453 454 static inline bool d_is_negative(const struct dentry *dentry) 455 { 456 // TODO: check d_is_whiteout(dentry) also. 457 return d_is_miss(dentry); 458 } 459 460 static inline bool d_flags_negative(unsigned flags) 461 { 462 return (flags & DCACHE_ENTRY_TYPE) == DCACHE_MISS_TYPE; 463 } 464 465 static inline bool d_is_positive(const struct dentry *dentry) 466 { 467 return !d_is_negative(dentry); 468 } 469 470 /** 471 * d_really_is_negative - Determine if a dentry is really negative (ignoring fallthroughs) 472 * @dentry: The dentry in question 473 * 474 * Returns true if the dentry represents either an absent name or a name that 475 * doesn't map to an inode (ie. ->d_inode is NULL). The dentry could represent 476 * a true miss, a whiteout that isn't represented by a 0,0 chardev or a 477 * fallthrough marker in an opaque directory. 478 * 479 * Note! (1) This should be used *only* by a filesystem to examine its own 480 * dentries. It should not be used to look at some other filesystem's 481 * dentries. (2) It should also be used in combination with d_inode() to get 482 * the inode. (3) The dentry may have something attached to ->d_lower and the 483 * type field of the flags may be set to something other than miss or whiteout. 484 */ 485 static inline bool d_really_is_negative(const struct dentry *dentry) 486 { 487 return dentry->d_inode == NULL; 488 } 489 490 /** 491 * d_really_is_positive - Determine if a dentry is really positive (ignoring fallthroughs) 492 * @dentry: The dentry in question 493 * 494 * Returns true if the dentry represents a name that maps to an inode 495 * (ie. ->d_inode is not NULL). The dentry might still represent a whiteout if 496 * that is represented on medium as a 0,0 chardev. 497 * 498 * Note! (1) This should be used *only* by a filesystem to examine its own 499 * dentries. It should not be used to look at some other filesystem's 500 * dentries. (2) It should also be used in combination with d_inode() to get 501 * the inode. 502 */ 503 static inline bool d_really_is_positive(const struct dentry *dentry) 504 { 505 return dentry->d_inode != NULL; 506 } 507 508 static inline int simple_positive(const struct dentry *dentry) 509 { 510 return d_really_is_positive(dentry) && !d_unhashed(dentry); 511 } 512 513 extern int sysctl_vfs_cache_pressure; 514 515 static inline unsigned long vfs_pressure_ratio(unsigned long val) 516 { 517 return mult_frac(val, sysctl_vfs_cache_pressure, 100); 518 } 519 520 /** 521 * d_inode - Get the actual inode of this dentry 522 * @dentry: The dentry to query 523 * 524 * This is the helper normal filesystems should use to get at their own inodes 525 * in their own dentries and ignore the layering superimposed upon them. 526 */ 527 static inline struct inode *d_inode(const struct dentry *dentry) 528 { 529 return dentry->d_inode; 530 } 531 532 /** 533 * d_inode_rcu - Get the actual inode of this dentry with READ_ONCE() 534 * @dentry: The dentry to query 535 * 536 * This is the helper normal filesystems should use to get at their own inodes 537 * in their own dentries and ignore the layering superimposed upon them. 538 */ 539 static inline struct inode *d_inode_rcu(const struct dentry *dentry) 540 { 541 return READ_ONCE(dentry->d_inode); 542 } 543 544 /** 545 * d_backing_inode - Get upper or lower inode we should be using 546 * @upper: The upper layer 547 * 548 * This is the helper that should be used to get at the inode that will be used 549 * if this dentry were to be opened as a file. The inode may be on the upper 550 * dentry or it may be on a lower dentry pinned by the upper. 551 * 552 * Normal filesystems should not use this to access their own inodes. 553 */ 554 static inline struct inode *d_backing_inode(const struct dentry *upper) 555 { 556 struct inode *inode = upper->d_inode; 557 558 return inode; 559 } 560 561 /** 562 * d_real - Return the real dentry 563 * @dentry: the dentry to query 564 * @type: the type of real dentry (data or metadata) 565 * 566 * If dentry is on a union/overlay, then return the underlying, real dentry. 567 * Otherwise return the dentry itself. 568 * 569 * See also: Documentation/filesystems/vfs.rst 570 */ 571 static inline struct dentry *d_real(struct dentry *dentry, enum d_real_type type) 572 { 573 if (unlikely(dentry->d_flags & DCACHE_OP_REAL)) 574 return dentry->d_op->d_real(dentry, type); 575 else 576 return dentry; 577 } 578 579 /** 580 * d_real_inode - Return the real inode hosting the data 581 * @dentry: The dentry to query 582 * 583 * If dentry is on a union/overlay, then return the underlying, real inode. 584 * Otherwise return d_inode(). 585 */ 586 static inline struct inode *d_real_inode(const struct dentry *dentry) 587 { 588 /* This usage of d_real() results in const dentry */ 589 return d_inode(d_real((struct dentry *) dentry, D_REAL_DATA)); 590 } 591 592 struct name_snapshot { 593 struct qstr name; 594 unsigned char inline_name[DNAME_INLINE_LEN]; 595 }; 596 void take_dentry_name_snapshot(struct name_snapshot *, struct dentry *); 597 void release_dentry_name_snapshot(struct name_snapshot *); 598 599 static inline struct dentry *d_first_child(const struct dentry *dentry) 600 { 601 return hlist_entry_safe(dentry->d_children.first, struct dentry, d_sib); 602 } 603 604 static inline struct dentry *d_next_sibling(const struct dentry *dentry) 605 { 606 return hlist_entry_safe(dentry->d_sib.next, struct dentry, d_sib); 607 } 608 609 #endif /* __LINUX_DCACHE_H */ 610