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