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_LEN 40 /* 192 bytes */ 72 #else 73 # ifdef CONFIG_SMP 74 # define DNAME_INLINE_LEN 40 /* 128 bytes */ 75 # else 76 # define DNAME_INLINE_LEN 44 /* 128 bytes */ 77 # endif 78 #endif 79 80 #define d_lock d_lockref.lock 81 82 struct dentry { 83 /* RCU lookup touched fields */ 84 unsigned int d_flags; /* protected by d_lock */ 85 seqcount_spinlock_t d_seq; /* per dentry seqlock */ 86 struct hlist_bl_node d_hash; /* lookup hash list */ 87 struct dentry *d_parent; /* parent directory */ 88 struct qstr d_name; 89 struct inode *d_inode; /* Where the name belongs to - NULL is 90 * negative */ 91 unsigned char d_iname[DNAME_INLINE_LEN]; /* small names */ 92 93 /* Ref lookup also touches following */ 94 struct lockref d_lockref; /* per-dentry lock and refcount */ 95 const struct dentry_operations *d_op; 96 struct super_block *d_sb; /* The root of the dentry tree */ 97 unsigned long d_time; /* used by d_revalidate */ 98 void *d_fsdata; /* fs-specific data */ 99 100 union { 101 struct list_head d_lru; /* LRU list */ 102 wait_queue_head_t *d_wait; /* in-lookup ones only */ 103 }; 104 struct hlist_node d_sib; /* child of parent list */ 105 struct hlist_head d_children; /* our children */ 106 /* 107 * d_alias and d_rcu can share memory 108 */ 109 union { 110 struct hlist_node d_alias; /* inode alias list */ 111 struct hlist_bl_node d_in_lookup_hash; /* only for in-lookup ones */ 112 struct rcu_head d_rcu; 113 } d_u; 114 }; 115 116 /* 117 * dentry->d_lock spinlock nesting subclasses: 118 * 119 * 0: normal 120 * 1: nested 121 */ 122 enum dentry_d_lock_class 123 { 124 DENTRY_D_LOCK_NORMAL, /* implicitly used by plain spin_lock() APIs. */ 125 DENTRY_D_LOCK_NESTED 126 }; 127 128 struct dentry_operations { 129 int (*d_revalidate)(struct dentry *, unsigned int); 130 int (*d_weak_revalidate)(struct dentry *, unsigned int); 131 int (*d_hash)(const struct dentry *, struct qstr *); 132 int (*d_compare)(const struct dentry *, 133 unsigned int, const char *, const struct qstr *); 134 int (*d_delete)(const struct dentry *); 135 int (*d_init)(struct dentry *); 136 void (*d_release)(struct dentry *); 137 void (*d_prune)(struct dentry *); 138 void (*d_iput)(struct dentry *, struct inode *); 139 char *(*d_dname)(struct dentry *, char *, int); 140 struct vfsmount *(*d_automount)(struct path *); 141 int (*d_manage)(const struct path *, bool); 142 struct dentry *(*d_real)(struct dentry *, const struct inode *); 143 } ____cacheline_aligned; 144 145 /* 146 * Locking rules for dentry_operations callbacks are to be found in 147 * Documentation/filesystems/locking.rst. Keep it updated! 148 * 149 * FUrther descriptions are found in Documentation/filesystems/vfs.rst. 150 * Keep it updated too! 151 */ 152 153 /* d_flags entries */ 154 #define DCACHE_OP_HASH BIT(0) 155 #define DCACHE_OP_COMPARE BIT(1) 156 #define DCACHE_OP_REVALIDATE BIT(2) 157 #define DCACHE_OP_DELETE BIT(3) 158 #define DCACHE_OP_PRUNE BIT(4) 159 160 #define DCACHE_DISCONNECTED BIT(5) 161 /* This dentry is possibly not currently connected to the dcache tree, in 162 * which case its parent will either be itself, or will have this flag as 163 * well. nfsd will not use a dentry with this bit set, but will first 164 * endeavour to clear the bit either by discovering that it is connected, 165 * or by performing lookup operations. Any filesystem which supports 166 * nfsd_operations MUST have a lookup function which, if it finds a 167 * directory inode with a DCACHE_DISCONNECTED dentry, will d_move that 168 * dentry into place and return that dentry rather than the passed one, 169 * typically using d_splice_alias. */ 170 171 #define DCACHE_REFERENCED BIT(6) /* Recently used, don't discard. */ 172 173 #define DCACHE_DONTCACHE BIT(7) /* Purge from memory on final dput() */ 174 175 #define DCACHE_CANT_MOUNT BIT(8) 176 #define DCACHE_SHRINK_LIST BIT(10) 177 178 #define DCACHE_OP_WEAK_REVALIDATE BIT(11) 179 180 #define DCACHE_NFSFS_RENAMED BIT(12) 181 /* this dentry has been "silly renamed" and has to be deleted on the last 182 * dput() */ 183 #define DCACHE_FSNOTIFY_PARENT_WATCHED BIT(14) 184 /* Parent inode is watched by some fsnotify listener */ 185 186 #define DCACHE_DENTRY_KILLED BIT(15) 187 188 #define DCACHE_MOUNTED BIT(16) /* is a mountpoint */ 189 #define DCACHE_NEED_AUTOMOUNT BIT(17) /* handle automount on this dir */ 190 #define DCACHE_MANAGE_TRANSIT BIT(18) /* manage transit from this dirent */ 191 #define DCACHE_MANAGED_DENTRY \ 192 (DCACHE_MOUNTED|DCACHE_NEED_AUTOMOUNT|DCACHE_MANAGE_TRANSIT) 193 194 #define DCACHE_LRU_LIST BIT(19) 195 196 #define DCACHE_ENTRY_TYPE (7 << 20) /* bits 20..22 are for storing type: */ 197 #define DCACHE_MISS_TYPE (0 << 20) /* Negative dentry */ 198 #define DCACHE_WHITEOUT_TYPE (1 << 20) /* Whiteout dentry (stop pathwalk) */ 199 #define DCACHE_DIRECTORY_TYPE (2 << 20) /* Normal directory */ 200 #define DCACHE_AUTODIR_TYPE (3 << 20) /* Lookupless directory (presumed automount) */ 201 #define DCACHE_REGULAR_TYPE (4 << 20) /* Regular file type */ 202 #define DCACHE_SPECIAL_TYPE (5 << 20) /* Other file type */ 203 #define DCACHE_SYMLINK_TYPE (6 << 20) /* Symlink */ 204 205 #define DCACHE_NOKEY_NAME BIT(25) /* Encrypted name encoded without key */ 206 #define DCACHE_OP_REAL BIT(26) 207 208 #define DCACHE_PAR_LOOKUP BIT(28) /* being looked up (with parent locked shared) */ 209 #define DCACHE_DENTRY_CURSOR BIT(29) 210 #define DCACHE_NORCU BIT(30) /* No RCU delay for freeing */ 211 212 extern seqlock_t rename_lock; 213 214 /* 215 * These are the low-level FS interfaces to the dcache.. 216 */ 217 extern void d_instantiate(struct dentry *, struct inode *); 218 extern void d_instantiate_new(struct dentry *, struct inode *); 219 extern void __d_drop(struct dentry *dentry); 220 extern void d_drop(struct dentry *dentry); 221 extern void d_delete(struct dentry *); 222 extern void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op); 223 224 /* allocate/de-allocate */ 225 extern struct dentry * d_alloc(struct dentry *, const struct qstr *); 226 extern struct dentry * d_alloc_anon(struct super_block *); 227 extern struct dentry * d_alloc_parallel(struct dentry *, const struct qstr *, 228 wait_queue_head_t *); 229 extern struct dentry * d_splice_alias(struct inode *, struct dentry *); 230 extern struct dentry * d_add_ci(struct dentry *, struct inode *, struct qstr *); 231 extern bool d_same_name(const struct dentry *dentry, const struct dentry *parent, 232 const struct qstr *name); 233 extern struct dentry * d_exact_alias(struct dentry *, struct inode *); 234 extern struct dentry *d_find_any_alias(struct inode *inode); 235 extern struct dentry * d_obtain_alias(struct inode *); 236 extern struct dentry * d_obtain_root(struct inode *); 237 extern void shrink_dcache_sb(struct super_block *); 238 extern void shrink_dcache_parent(struct dentry *); 239 extern void d_invalidate(struct dentry *); 240 241 /* only used at mount-time */ 242 extern struct dentry * d_make_root(struct inode *); 243 244 extern void d_mark_tmpfile(struct file *, struct inode *); 245 extern void d_tmpfile(struct file *, struct inode *); 246 247 extern struct dentry *d_find_alias(struct inode *); 248 extern void d_prune_aliases(struct inode *); 249 250 extern struct dentry *d_find_alias_rcu(struct inode *); 251 252 /* test whether we have any submounts in a subdir tree */ 253 extern int path_has_submounts(const struct path *); 254 255 /* 256 * This adds the entry to the hash queues. 257 */ 258 extern void d_rehash(struct dentry *); 259 260 extern void d_add(struct dentry *, struct inode *); 261 262 /* used for rename() and baskets */ 263 extern void d_move(struct dentry *, struct dentry *); 264 extern void d_exchange(struct dentry *, struct dentry *); 265 extern struct dentry *d_ancestor(struct dentry *, struct dentry *); 266 267 extern struct dentry *d_lookup(const struct dentry *, const struct qstr *); 268 extern struct dentry *d_hash_and_lookup(struct dentry *, struct qstr *); 269 270 static inline unsigned d_count(const struct dentry *dentry) 271 { 272 return dentry->d_lockref.count; 273 } 274 275 /* 276 * helper function for dentry_operations.d_dname() members 277 */ 278 extern __printf(3, 4) 279 char *dynamic_dname(char *, int, const char *, ...); 280 281 extern char *__d_path(const struct path *, const struct path *, char *, int); 282 extern char *d_absolute_path(const struct path *, char *, int); 283 extern char *d_path(const struct path *, char *, int); 284 extern char *dentry_path_raw(const struct dentry *, char *, int); 285 extern char *dentry_path(const struct dentry *, char *, int); 286 287 /* Allocation counts.. */ 288 289 /** 290 * dget_dlock - get a reference to a dentry 291 * @dentry: dentry to get a reference to 292 * 293 * Given a live dentry, increment the reference count and return the dentry. 294 * Caller must hold @dentry->d_lock. Making sure that dentry is alive is 295 * caller's resonsibility. There are many conditions sufficient to guarantee 296 * that; e.g. anything with non-negative refcount is alive, so's anything 297 * hashed, anything positive, anyone's parent, etc. 298 */ 299 static inline struct dentry *dget_dlock(struct dentry *dentry) 300 { 301 dentry->d_lockref.count++; 302 return dentry; 303 } 304 305 306 /** 307 * dget - get a reference to a dentry 308 * @dentry: dentry to get a reference to 309 * 310 * Given a dentry or %NULL pointer increment the reference count 311 * if appropriate and return the dentry. A dentry will not be 312 * destroyed when it has references. Conversely, a dentry with 313 * no references can disappear for any number of reasons, starting 314 * with memory pressure. In other words, that primitive is 315 * used to clone an existing reference; using it on something with 316 * zero refcount is a bug. 317 * 318 * NOTE: it will spin if @dentry->d_lock is held. From the deadlock 319 * avoidance point of view it is equivalent to spin_lock()/increment 320 * refcount/spin_unlock(), so calling it under @dentry->d_lock is 321 * always a bug; so's calling it under ->d_lock on any of its descendents. 322 * 323 */ 324 static inline struct dentry *dget(struct dentry *dentry) 325 { 326 if (dentry) 327 lockref_get(&dentry->d_lockref); 328 return dentry; 329 } 330 331 extern struct dentry *dget_parent(struct dentry *dentry); 332 333 /** 334 * d_unhashed - is dentry hashed 335 * @dentry: entry to check 336 * 337 * Returns true if the dentry passed is not currently hashed. 338 */ 339 static inline int d_unhashed(const struct dentry *dentry) 340 { 341 return hlist_bl_unhashed(&dentry->d_hash); 342 } 343 344 static inline int d_unlinked(const struct dentry *dentry) 345 { 346 return d_unhashed(dentry) && !IS_ROOT(dentry); 347 } 348 349 static inline int cant_mount(const struct dentry *dentry) 350 { 351 return (dentry->d_flags & DCACHE_CANT_MOUNT); 352 } 353 354 static inline void dont_mount(struct dentry *dentry) 355 { 356 spin_lock(&dentry->d_lock); 357 dentry->d_flags |= DCACHE_CANT_MOUNT; 358 spin_unlock(&dentry->d_lock); 359 } 360 361 extern void __d_lookup_unhash_wake(struct dentry *dentry); 362 363 static inline int d_in_lookup(const struct dentry *dentry) 364 { 365 return dentry->d_flags & DCACHE_PAR_LOOKUP; 366 } 367 368 static inline void d_lookup_done(struct dentry *dentry) 369 { 370 if (unlikely(d_in_lookup(dentry))) 371 __d_lookup_unhash_wake(dentry); 372 } 373 374 extern void dput(struct dentry *); 375 376 static inline bool d_managed(const struct dentry *dentry) 377 { 378 return dentry->d_flags & DCACHE_MANAGED_DENTRY; 379 } 380 381 static inline bool d_mountpoint(const struct dentry *dentry) 382 { 383 return dentry->d_flags & DCACHE_MOUNTED; 384 } 385 386 /* 387 * Directory cache entry type accessor functions. 388 */ 389 static inline unsigned __d_entry_type(const struct dentry *dentry) 390 { 391 return dentry->d_flags & DCACHE_ENTRY_TYPE; 392 } 393 394 static inline bool d_is_miss(const struct dentry *dentry) 395 { 396 return __d_entry_type(dentry) == DCACHE_MISS_TYPE; 397 } 398 399 static inline bool d_is_whiteout(const struct dentry *dentry) 400 { 401 return __d_entry_type(dentry) == DCACHE_WHITEOUT_TYPE; 402 } 403 404 static inline bool d_can_lookup(const struct dentry *dentry) 405 { 406 return __d_entry_type(dentry) == DCACHE_DIRECTORY_TYPE; 407 } 408 409 static inline bool d_is_autodir(const struct dentry *dentry) 410 { 411 return __d_entry_type(dentry) == DCACHE_AUTODIR_TYPE; 412 } 413 414 static inline bool d_is_dir(const struct dentry *dentry) 415 { 416 return d_can_lookup(dentry) || d_is_autodir(dentry); 417 } 418 419 static inline bool d_is_symlink(const struct dentry *dentry) 420 { 421 return __d_entry_type(dentry) == DCACHE_SYMLINK_TYPE; 422 } 423 424 static inline bool d_is_reg(const struct dentry *dentry) 425 { 426 return __d_entry_type(dentry) == DCACHE_REGULAR_TYPE; 427 } 428 429 static inline bool d_is_special(const struct dentry *dentry) 430 { 431 return __d_entry_type(dentry) == DCACHE_SPECIAL_TYPE; 432 } 433 434 static inline bool d_is_file(const struct dentry *dentry) 435 { 436 return d_is_reg(dentry) || d_is_special(dentry); 437 } 438 439 static inline bool d_is_negative(const struct dentry *dentry) 440 { 441 // TODO: check d_is_whiteout(dentry) also. 442 return d_is_miss(dentry); 443 } 444 445 static inline bool d_flags_negative(unsigned flags) 446 { 447 return (flags & DCACHE_ENTRY_TYPE) == DCACHE_MISS_TYPE; 448 } 449 450 static inline bool d_is_positive(const struct dentry *dentry) 451 { 452 return !d_is_negative(dentry); 453 } 454 455 /** 456 * d_really_is_negative - Determine if a dentry is really negative (ignoring fallthroughs) 457 * @dentry: The dentry in question 458 * 459 * Returns true if the dentry represents either an absent name or a name that 460 * doesn't map to an inode (ie. ->d_inode is NULL). The dentry could represent 461 * a true miss, a whiteout that isn't represented by a 0,0 chardev or a 462 * fallthrough marker in an opaque directory. 463 * 464 * Note! (1) This should be used *only* by a filesystem to examine its own 465 * dentries. It should not be used to look at some other filesystem's 466 * dentries. (2) It should also be used in combination with d_inode() to get 467 * the inode. (3) The dentry may have something attached to ->d_lower and the 468 * type field of the flags may be set to something other than miss or whiteout. 469 */ 470 static inline bool d_really_is_negative(const struct dentry *dentry) 471 { 472 return dentry->d_inode == NULL; 473 } 474 475 /** 476 * d_really_is_positive - Determine if a dentry is really positive (ignoring fallthroughs) 477 * @dentry: The dentry in question 478 * 479 * Returns true if the dentry represents a name that maps to an inode 480 * (ie. ->d_inode is not NULL). The dentry might still represent a whiteout if 481 * that is represented on medium as a 0,0 chardev. 482 * 483 * Note! (1) This should be used *only* by a filesystem to examine its own 484 * dentries. It should not be used to look at some other filesystem's 485 * dentries. (2) It should also be used in combination with d_inode() to get 486 * the inode. 487 */ 488 static inline bool d_really_is_positive(const struct dentry *dentry) 489 { 490 return dentry->d_inode != NULL; 491 } 492 493 static inline int simple_positive(const struct dentry *dentry) 494 { 495 return d_really_is_positive(dentry) && !d_unhashed(dentry); 496 } 497 498 extern int sysctl_vfs_cache_pressure; 499 500 static inline unsigned long vfs_pressure_ratio(unsigned long val) 501 { 502 return mult_frac(val, sysctl_vfs_cache_pressure, 100); 503 } 504 505 /** 506 * d_inode - Get the actual inode of this dentry 507 * @dentry: The dentry to query 508 * 509 * This is the helper normal filesystems should use to get at their own inodes 510 * in their own dentries and ignore the layering superimposed upon them. 511 */ 512 static inline struct inode *d_inode(const struct dentry *dentry) 513 { 514 return dentry->d_inode; 515 } 516 517 /** 518 * d_inode_rcu - Get the actual inode of this dentry with READ_ONCE() 519 * @dentry: The dentry to query 520 * 521 * This is the helper normal filesystems should use to get at their own inodes 522 * in their own dentries and ignore the layering superimposed upon them. 523 */ 524 static inline struct inode *d_inode_rcu(const struct dentry *dentry) 525 { 526 return READ_ONCE(dentry->d_inode); 527 } 528 529 /** 530 * d_backing_inode - Get upper or lower inode we should be using 531 * @upper: The upper layer 532 * 533 * This is the helper that should be used to get at the inode that will be used 534 * if this dentry were to be opened as a file. The inode may be on the upper 535 * dentry or it may be on a lower dentry pinned by the upper. 536 * 537 * Normal filesystems should not use this to access their own inodes. 538 */ 539 static inline struct inode *d_backing_inode(const struct dentry *upper) 540 { 541 struct inode *inode = upper->d_inode; 542 543 return inode; 544 } 545 546 /** 547 * d_real - Return the real dentry 548 * @dentry: the dentry to query 549 * @inode: inode to select the dentry from multiple layers (can be NULL) 550 * 551 * If dentry is on a union/overlay, then return the underlying, real dentry. 552 * Otherwise return the dentry itself. 553 * 554 * See also: Documentation/filesystems/vfs.rst 555 */ 556 static inline struct dentry *d_real(struct dentry *dentry, 557 const struct inode *inode) 558 { 559 if (unlikely(dentry->d_flags & DCACHE_OP_REAL)) 560 return dentry->d_op->d_real(dentry, inode); 561 else 562 return dentry; 563 } 564 565 /** 566 * d_real_inode - Return the real inode 567 * @dentry: The dentry to query 568 * 569 * If dentry is on a union/overlay, then return the underlying, real inode. 570 * Otherwise return d_inode(). 571 */ 572 static inline struct inode *d_real_inode(const struct dentry *dentry) 573 { 574 /* This usage of d_real() results in const dentry */ 575 return d_backing_inode(d_real((struct dentry *) dentry, NULL)); 576 } 577 578 struct name_snapshot { 579 struct qstr name; 580 unsigned char inline_name[DNAME_INLINE_LEN]; 581 }; 582 void take_dentry_name_snapshot(struct name_snapshot *, struct dentry *); 583 void release_dentry_name_snapshot(struct name_snapshot *); 584 585 static inline struct dentry *d_first_child(const struct dentry *dentry) 586 { 587 return hlist_entry_safe(dentry->d_children.first, struct dentry, d_sib); 588 } 589 590 static inline struct dentry *d_next_sibling(const struct dentry *dentry) 591 { 592 return hlist_entry_safe(dentry->d_sib.next, struct dentry, d_sib); 593 } 594 595 #endif /* __LINUX_DCACHE_H */ 596