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_LEN(n,l) (struct qstr)QSTR_INIT(n,l) 61 #define QSTR(n) QSTR_LEN(n, strlen(n)) 62 63 extern const struct qstr empty_name; 64 extern const struct qstr slash_name; 65 extern const struct qstr dotdot_name; 66 67 /* 68 * Try to keep struct dentry aligned on 64 byte cachelines (this will 69 * give reasonable cacheline footprint with larger lines without the 70 * large memory footprint increase). 71 */ 72 #ifdef CONFIG_64BIT 73 # define DNAME_INLINE_WORDS 5 /* 192 bytes */ 74 #else 75 # ifdef CONFIG_SMP 76 # define DNAME_INLINE_WORDS 9 /* 128 bytes */ 77 # else 78 # define DNAME_INLINE_WORDS 11 /* 128 bytes */ 79 # endif 80 #endif 81 82 #define DNAME_INLINE_LEN (DNAME_INLINE_WORDS*sizeof(unsigned long)) 83 84 union shortname_store { 85 unsigned char string[DNAME_INLINE_LEN]; 86 unsigned long words[DNAME_INLINE_WORDS]; 87 }; 88 89 #define d_lock d_lockref.lock 90 #define d_iname d_shortname.string 91 struct completion_list; 92 93 struct dentry { 94 /* RCU lookup touched fields */ 95 unsigned int d_flags; /* protected by d_lock */ 96 seqcount_spinlock_t d_seq; /* per dentry seqlock */ 97 struct hlist_bl_node d_hash; /* lookup hash list */ 98 struct dentry *d_parent; /* parent directory */ 99 union { 100 struct qstr __d_name; /* for use ONLY in fs/dcache.c */ 101 const struct qstr d_name; 102 }; 103 struct inode *d_inode; /* Where the name belongs to - NULL is 104 * negative */ 105 union shortname_store d_shortname; 106 /* --- cacheline 1 boundary (64 bytes) was 32 bytes ago --- */ 107 108 /* Ref lookup also touches following */ 109 const struct dentry_operations *d_op; 110 struct super_block *d_sb; /* The root of the dentry tree */ 111 unsigned long d_time; /* used by d_revalidate */ 112 void *d_fsdata; /* fs-specific data */ 113 /* --- cacheline 2 boundary (128 bytes) --- */ 114 struct lockref d_lockref; /* per-dentry lock and refcount 115 * keep separate from RCU lookup area if 116 * possible! 117 */ 118 119 /* lockdep tracking of DCACHE_PAR_LOOKUP locks */ 120 struct lockdep_map dep_map; 121 struct list_head d_lru; /* LRU list */ 122 struct hlist_node d_sib; /* child of parent list */ 123 struct hlist_head d_children; /* our children */ 124 /* 125 * the following members can share memory - their uses are 126 * mutually exclusive. 127 */ 128 union { 129 /* positives: inode alias list */ 130 struct hlist_node d_alias; 131 /* in-lookup ones (all negative, live): hash chain */ 132 struct hlist_bl_node d_in_lookup_hash; 133 /* killed ones: (already negative) used to schedule freeing */ 134 struct rcu_head d_rcu; 135 /* 136 * live non-in-lookup negatives: used if shrink_dcache_tree() 137 * races with eviction by another thread and needs to wait for 138 * this dentry to get killed . Remains NULL for almost all 139 * negative dentries. 140 */ 141 struct completion_list *waiters; 142 }; 143 }; 144 145 /* 146 * dentry->d_lock spinlock nesting subclasses: 147 * 148 * 0: normal 149 * 1: nested 150 */ 151 enum dentry_d_lock_class 152 { 153 DENTRY_D_LOCK_NORMAL, /* implicitly used by plain spin_lock() APIs. */ 154 DENTRY_D_LOCK_NESTED 155 }; 156 157 enum d_real_type { 158 D_REAL_DATA, 159 D_REAL_METADATA, 160 }; 161 162 struct dentry_operations { 163 int (*d_revalidate)(struct inode *, const struct qstr *, 164 struct dentry *, unsigned int); 165 int (*d_weak_revalidate)(struct dentry *, unsigned int); 166 int (*d_hash)(const struct dentry *, struct qstr *); 167 int (*d_compare)(const struct dentry *, 168 unsigned int, const char *, const struct qstr *); 169 int (*d_delete)(const struct dentry *); 170 int (*d_init)(struct dentry *); 171 void (*d_release)(struct dentry *); 172 void (*d_prune)(struct dentry *); 173 void (*d_iput)(struct dentry *, struct inode *); 174 char *(*d_dname)(struct dentry *, char *, int); 175 struct vfsmount *(*d_automount)(struct path *); 176 int (*d_manage)(const struct path *, bool); 177 struct dentry *(*d_real)(struct dentry *, enum d_real_type type); 178 bool (*d_unalias_trylock)(const struct dentry *); 179 void (*d_unalias_unlock)(const struct dentry *); 180 } ____cacheline_aligned; 181 182 /* 183 * Locking rules for dentry_operations callbacks are to be found in 184 * Documentation/filesystems/locking.rst. Keep it updated! 185 * 186 * FUrther descriptions are found in Documentation/filesystems/vfs.rst. 187 * Keep it updated too! 188 */ 189 190 /* d_flags entries */ 191 enum dentry_flags { 192 DCACHE_OP_HASH = BIT(0), 193 DCACHE_OP_COMPARE = BIT(1), 194 DCACHE_OP_REVALIDATE = BIT(2), 195 DCACHE_OP_DELETE = BIT(3), 196 DCACHE_OP_PRUNE = BIT(4), 197 /* 198 * This dentry is possibly not currently connected to the dcache tree, 199 * in which case its parent will either be itself, or will have this 200 * flag as well. nfsd will not use a dentry with this bit set, but will 201 * first endeavour to clear the bit either by discovering that it is 202 * connected, or by performing lookup operations. Any filesystem which 203 * supports nfsd_operations MUST have a lookup function which, if it 204 * finds a directory inode with a DCACHE_DISCONNECTED dentry, will 205 * d_move that dentry into place and return that dentry rather than the 206 * passed one, typically using d_splice_alias. 207 */ 208 DCACHE_DISCONNECTED = BIT(5), 209 DCACHE_REFERENCED = BIT(6), /* Recently used, don't discard. */ 210 DCACHE_DONTCACHE = BIT(7), /* Purge from memory on final dput() */ 211 DCACHE_CANT_MOUNT = BIT(8), 212 DCACHE_LOOKUP_WAITERS = BIT(9), /* A thread is waiting for 213 * PAR_LOOKUP to clear 214 */ 215 DCACHE_SHRINK_LIST = BIT(10), 216 DCACHE_OP_WEAK_REVALIDATE = BIT(11), 217 /* 218 * this dentry has been "silly renamed" and has to be deleted on the 219 * last dput() 220 */ 221 DCACHE_NFSFS_RENAMED = BIT(12), 222 DCACHE_FSNOTIFY_PARENT_WATCHED = BIT(13), /* Parent inode is watched by some fsnotify listener */ 223 DCACHE_DENTRY_KILLED = BIT(14), 224 DCACHE_MOUNTED = BIT(15), /* is a mountpoint */ 225 DCACHE_NEED_AUTOMOUNT = BIT(16), /* handle automount on this dir */ 226 DCACHE_MANAGE_TRANSIT = BIT(17), /* manage transit from this dirent */ 227 DCACHE_LRU_LIST = BIT(18), 228 DCACHE_ENTRY_TYPE = (7 << 19), /* bits 19..21 are for storing type: */ 229 DCACHE_MISS_TYPE = (0 << 19), /* Negative dentry */ 230 DCACHE_WHITEOUT_TYPE = (1 << 19), /* Whiteout dentry (stop pathwalk) */ 231 DCACHE_DIRECTORY_TYPE = (2 << 19), /* Normal directory */ 232 DCACHE_AUTODIR_TYPE = (3 << 19), /* Lookupless directory (presumed automount) */ 233 DCACHE_REGULAR_TYPE = (4 << 19), /* Regular file type */ 234 DCACHE_SPECIAL_TYPE = (5 << 19), /* Other file type */ 235 DCACHE_SYMLINK_TYPE = (6 << 19), /* Symlink */ 236 DCACHE_NOKEY_NAME = BIT(22), /* Encrypted name encoded without key */ 237 DCACHE_OP_REAL = BIT(23), 238 DCACHE_PAR_LOOKUP = BIT(24), /* being looked up (with parent locked shared) */ 239 DCACHE_DENTRY_CURSOR = BIT(25), 240 DCACHE_NORCU = BIT(26), /* No RCU delay for freeing */ 241 DCACHE_PERSISTENT = BIT(27), 242 /* 28, 29, 30 free */ 243 DCACHE_PRIVATE = BIT(31) /* fs-specific flag */ 244 }; 245 246 #define DCACHE_MANAGED_DENTRY \ 247 (DCACHE_MOUNTED|DCACHE_NEED_AUTOMOUNT|DCACHE_MANAGE_TRANSIT) 248 249 extern seqlock_t rename_lock; 250 251 /* 252 * These are the low-level FS interfaces to the dcache.. 253 */ 254 extern void d_instantiate(struct dentry *, struct inode *); 255 extern void d_instantiate_new(struct dentry *, struct inode *); 256 extern void __d_drop(struct dentry *dentry); 257 extern void d_drop(struct dentry *dentry); 258 extern void d_delete(struct dentry *); 259 260 /* allocate/de-allocate */ 261 extern struct dentry * d_alloc(struct dentry *, const struct qstr *); 262 extern struct dentry * d_alloc_anon(struct super_block *); 263 extern struct dentry * d_alloc_parallel(struct dentry *, const struct qstr *); 264 extern struct dentry * d_alloc_trylock(struct dentry *, struct qstr *); 265 extern struct dentry * d_splice_alias(struct inode *, struct dentry *); 266 struct dentry *d_duplicate(struct dentry *dentry); 267 /* weird procfs mess; *NOT* exported */ 268 extern struct dentry * d_splice_alias_ops(struct inode *, struct dentry *, 269 const struct dentry_operations *); 270 extern struct dentry * d_add_ci(struct dentry *, struct inode *, struct qstr *); 271 extern bool d_same_name(const struct dentry *dentry, const struct dentry *parent, 272 const struct qstr *name); 273 extern struct dentry *d_find_any_alias(struct inode *inode); 274 extern struct dentry * d_obtain_alias(struct inode *); 275 extern struct dentry * d_obtain_root(struct inode *); 276 extern void shrink_dcache_sb(struct super_block *); 277 extern void shrink_dcache_parent(struct dentry *); 278 extern void d_invalidate(struct dentry *); 279 280 /* only used at mount-time */ 281 extern struct dentry * d_make_root(struct inode *); 282 283 extern void d_mark_tmpfile(struct file *, struct inode *); 284 int d_mark_tmpfile_name(struct file *file, const struct qstr *name); 285 extern void d_tmpfile(struct file *, struct inode *); 286 287 extern struct dentry *d_find_alias(struct inode *); 288 extern void d_prune_aliases(struct inode *); 289 extern bool __move_to_shrink_list(struct dentry *, struct list_head *); 290 extern void shrink_dentry_list(struct list_head *); 291 292 extern struct dentry *d_find_alias_rcu(struct inode *); 293 294 /* test whether we have any submounts in a subdir tree */ 295 extern int path_has_submounts(const struct path *); 296 297 /* 298 * This adds the entry to the hash queues. 299 */ 300 extern void d_rehash(struct dentry *); 301 302 extern void d_add(struct dentry *, struct inode *); 303 304 /* used for rename() and baskets */ 305 extern void d_move(struct dentry *, struct dentry *); 306 extern void d_exchange(struct dentry *, struct dentry *); 307 extern struct dentry *d_ancestor(struct dentry *, struct dentry *); 308 309 extern struct dentry *d_lookup(const struct dentry *, const struct qstr *); 310 311 static inline unsigned d_count(const struct dentry *dentry) 312 { 313 return dentry->d_lockref.count; 314 } 315 316 ino_t d_parent_ino(struct dentry *dentry); 317 318 /* 319 * helper function for dentry_operations.d_dname() members 320 */ 321 extern __printf(3, 4) 322 char *dynamic_dname(char *, int, const char *, ...); 323 324 extern char *__d_path(const struct path *, const struct path *, char *, int); 325 extern char *d_absolute_path(const struct path *, char *, int); 326 extern char *d_path(const struct path *, char *, int); 327 extern char *dentry_path_raw(const struct dentry *, char *, int); 328 extern char *dentry_path(const struct dentry *, char *, int); 329 330 /* Allocation counts.. */ 331 332 /** 333 * dget_dlock - get a reference to a dentry 334 * @dentry: dentry to get a reference to 335 * 336 * Given a live dentry, increment the reference count and return the dentry. 337 * Caller must hold @dentry->d_lock. Making sure that dentry is alive is 338 * caller's resonsibility. There are many conditions sufficient to guarantee 339 * that; e.g. anything with non-negative refcount is alive, so's anything 340 * hashed, anything positive, anyone's parent, etc. 341 */ 342 static inline struct dentry *dget_dlock(struct dentry *dentry) 343 { 344 dentry->d_lockref.count++; 345 return dentry; 346 } 347 348 349 /** 350 * dget - get a reference to a dentry 351 * @dentry: dentry to get a reference to 352 * 353 * Given a dentry or %NULL pointer increment the reference count 354 * if appropriate and return the dentry. A dentry will not be 355 * destroyed when it has references. Conversely, a dentry with 356 * no references can disappear for any number of reasons, starting 357 * with memory pressure. In other words, that primitive is 358 * used to clone an existing reference; using it on something with 359 * zero refcount is a bug. 360 * 361 * NOTE: it will spin if @dentry->d_lock is held. From the deadlock 362 * avoidance point of view it is equivalent to spin_lock()/increment 363 * refcount/spin_unlock(), so calling it under @dentry->d_lock is 364 * always a bug; so's calling it under ->d_lock on any of its descendents. 365 * 366 */ 367 static inline struct dentry *dget(struct dentry *dentry) 368 { 369 if (dentry) 370 lockref_get(&dentry->d_lockref); 371 return dentry; 372 } 373 374 /* dentry->d_inode->i_lock must be held by caller */ 375 static inline bool dget_alias_ilocked(struct dentry *dentry) 376 { 377 if (likely(!(READ_ONCE(dentry->d_flags) & DCACHE_NORCU))) { 378 lockref_get(&dentry->d_lockref); 379 return true; 380 } 381 // NORCU dentries with zero refcount MUST NOT be grabbed 382 spin_lock(&dentry->d_lock); 383 if (dentry->d_lockref.count > 0) { 384 dget_dlock(dentry); 385 spin_unlock(&dentry->d_lock); 386 return true; 387 } 388 spin_unlock(&dentry->d_lock); 389 return false; 390 } 391 392 extern struct dentry *dget_parent(struct dentry *dentry); 393 394 /** 395 * d_unhashed - is dentry hashed 396 * @dentry: entry to check 397 * 398 * Returns true if the dentry passed is not currently hashed. 399 */ 400 static inline int d_unhashed(const struct dentry *dentry) 401 { 402 return hlist_bl_unhashed(&dentry->d_hash); 403 } 404 405 static inline int d_unlinked(const struct dentry *dentry) 406 { 407 return d_unhashed(dentry) && !IS_ROOT(dentry); 408 } 409 410 static inline int cant_mount(const struct dentry *dentry) 411 { 412 return (dentry->d_flags & DCACHE_CANT_MOUNT); 413 } 414 415 static inline void dont_mount(struct dentry *dentry) 416 { 417 spin_lock(&dentry->d_lock); 418 dentry->d_flags |= DCACHE_CANT_MOUNT; 419 spin_unlock(&dentry->d_lock); 420 } 421 422 extern void __d_lookup_unhash_wake(struct dentry *dentry); 423 424 static inline int d_in_lookup(const struct dentry *dentry) 425 { 426 return dentry->d_flags & DCACHE_PAR_LOOKUP; 427 } 428 429 static inline void d_lookup_done(struct dentry *dentry) 430 { 431 if (unlikely(d_in_lookup(dentry))) 432 __d_lookup_unhash_wake(dentry); 433 } 434 435 extern void dput(struct dentry *); 436 437 static inline bool d_managed(const struct dentry *dentry) 438 { 439 return dentry->d_flags & DCACHE_MANAGED_DENTRY; 440 } 441 442 static inline bool d_mountpoint(const struct dentry *dentry) 443 { 444 return dentry->d_flags & DCACHE_MOUNTED; 445 } 446 447 /* 448 * Directory cache entry type accessor functions. 449 */ 450 static inline unsigned __d_entry_type(const struct dentry *dentry) 451 { 452 return dentry->d_flags & DCACHE_ENTRY_TYPE; 453 } 454 455 static inline bool d_is_miss(const struct dentry *dentry) 456 { 457 return __d_entry_type(dentry) == DCACHE_MISS_TYPE; 458 } 459 460 static inline bool d_is_whiteout(const struct dentry *dentry) 461 { 462 return __d_entry_type(dentry) == DCACHE_WHITEOUT_TYPE; 463 } 464 465 static inline bool d_can_lookup(const struct dentry *dentry) 466 { 467 return __d_entry_type(dentry) == DCACHE_DIRECTORY_TYPE; 468 } 469 470 static inline bool d_is_autodir(const struct dentry *dentry) 471 { 472 return __d_entry_type(dentry) == DCACHE_AUTODIR_TYPE; 473 } 474 475 static inline bool d_is_dir(const struct dentry *dentry) 476 { 477 return d_can_lookup(dentry) || d_is_autodir(dentry); 478 } 479 480 static inline bool d_is_symlink(const struct dentry *dentry) 481 { 482 return __d_entry_type(dentry) == DCACHE_SYMLINK_TYPE; 483 } 484 485 static inline bool d_is_reg(const struct dentry *dentry) 486 { 487 return __d_entry_type(dentry) == DCACHE_REGULAR_TYPE; 488 } 489 490 static inline bool d_is_special(const struct dentry *dentry) 491 { 492 return __d_entry_type(dentry) == DCACHE_SPECIAL_TYPE; 493 } 494 495 static inline bool d_is_file(const struct dentry *dentry) 496 { 497 return d_is_reg(dentry) || d_is_special(dentry); 498 } 499 500 static inline bool d_is_negative(const struct dentry *dentry) 501 { 502 // TODO: check d_is_whiteout(dentry) also. 503 return d_is_miss(dentry); 504 } 505 506 static inline bool d_flags_negative(unsigned flags) 507 { 508 return (flags & DCACHE_ENTRY_TYPE) == DCACHE_MISS_TYPE; 509 } 510 511 static inline bool d_is_positive(const struct dentry *dentry) 512 { 513 return !d_is_negative(dentry); 514 } 515 516 /** 517 * d_really_is_negative - Determine if a dentry is really negative (ignoring fallthroughs) 518 * @dentry: The dentry in question 519 * 520 * Returns true if the dentry represents either an absent name or a name that 521 * doesn't map to an inode (ie. ->d_inode is NULL). The dentry could represent 522 * a true miss, a whiteout that isn't represented by a 0,0 chardev or a 523 * fallthrough marker in an opaque directory. 524 * 525 * Note! (1) This should be used *only* by a filesystem to examine its own 526 * dentries. It should not be used to look at some other filesystem's 527 * dentries. (2) It should also be used in combination with d_inode() to get 528 * the inode. (3) The dentry may have something attached to ->d_lower and the 529 * type field of the flags may be set to something other than miss or whiteout. 530 */ 531 static inline bool d_really_is_negative(const struct dentry *dentry) 532 { 533 return dentry->d_inode == NULL; 534 } 535 536 /** 537 * d_really_is_positive - Determine if a dentry is really positive (ignoring fallthroughs) 538 * @dentry: The dentry in question 539 * 540 * Returns true if the dentry represents a name that maps to an inode 541 * (ie. ->d_inode is not NULL). The dentry might still represent a whiteout if 542 * that is represented on medium as a 0,0 chardev. 543 * 544 * Note! (1) This should be used *only* by a filesystem to examine its own 545 * dentries. It should not be used to look at some other filesystem's 546 * dentries. (2) It should also be used in combination with d_inode() to get 547 * the inode. 548 */ 549 static inline bool d_really_is_positive(const struct dentry *dentry) 550 { 551 return dentry->d_inode != NULL; 552 } 553 554 static inline int simple_positive(const struct dentry *dentry) 555 { 556 return d_really_is_positive(dentry) && !d_unhashed(dentry); 557 } 558 559 unsigned long vfs_pressure_ratio(unsigned long val); 560 561 /** 562 * d_lookup_release - release ownership of DCACHE_PAR_LOOKUP lock 563 * @dentry: dentry that is locked 564 * 565 * If an in-lookup dentry is to be passed to another thread which 566 * will drop the in-lookup lock, then d_lookup_release() must be called 567 * to tell lockdep that this thread no lock holds the lock. The 568 * thread that receives the lock must call d_lookup_acquire() to 569 * acquire the lock. 570 */ 571 static inline void d_lookup_release(struct dentry *dentry) 572 { 573 if (d_in_lookup(dentry)) 574 lock_map_release(&dentry->dep_map); 575 } 576 577 /** 578 * d_lookup_acquire - acquire ownership of DCACHE_PAR_LOOKUP lock 579 * @dentry: dentry that is locked 580 * 581 * If an in-lookup dentry was passed to this thread, the 582 * d_lookup_acquire() must be called to tell lockdep that this 583 * thread now owns the DCACHE_PAR_LOOKUP lock. 584 */ 585 static inline void d_lookup_acquire(struct dentry *dentry) 586 { 587 if (d_in_lookup(dentry)) 588 lock_map_acquire_try(&dentry->dep_map); 589 } 590 591 /** 592 * d_inode - Get the actual inode of this dentry 593 * @dentry: The dentry to query 594 * 595 * This is the helper normal filesystems should use to get at their own inodes 596 * in their own dentries and ignore the layering superimposed upon them. 597 */ 598 static inline struct inode *d_inode(const struct dentry *dentry) 599 { 600 return dentry->d_inode; 601 } 602 603 /** 604 * d_inode_rcu - Get the actual inode of this dentry with READ_ONCE() 605 * @dentry: The dentry to query 606 * 607 * This is the helper normal filesystems should use to get at their own inodes 608 * in their own dentries and ignore the layering superimposed upon them. 609 */ 610 static inline struct inode *d_inode_rcu(const struct dentry *dentry) 611 { 612 return READ_ONCE(dentry->d_inode); 613 } 614 615 /** 616 * d_backing_inode - Get upper or lower inode we should be using 617 * @upper: The upper layer 618 * 619 * This is the helper that should be used to get at the inode that will be used 620 * if this dentry were to be opened as a file. The inode may be on the upper 621 * dentry or it may be on a lower dentry pinned by the upper. 622 * 623 * Normal filesystems should not use this to access their own inodes. 624 */ 625 static inline struct inode *d_backing_inode(const struct dentry *upper) 626 { 627 struct inode *inode = upper->d_inode; 628 629 return inode; 630 } 631 632 /** 633 * d_real - Return the real dentry 634 * @dentry: the dentry to query 635 * @type: the type of real dentry (data or metadata) 636 * 637 * If dentry is on a union/overlay, then return the underlying, real dentry. 638 * Otherwise return the dentry itself. 639 * 640 * See also: Documentation/filesystems/vfs.rst 641 */ 642 static inline struct dentry *d_real(struct dentry *dentry, enum d_real_type type) 643 { 644 if (unlikely(dentry->d_flags & DCACHE_OP_REAL)) 645 return dentry->d_op->d_real(dentry, type); 646 else 647 return dentry; 648 } 649 650 /** 651 * d_real_inode - Return the real inode hosting the data 652 * @dentry: The dentry to query 653 * 654 * If dentry is on a union/overlay, then return the underlying, real inode. 655 * Otherwise return d_inode(). 656 */ 657 static inline struct inode *d_real_inode(const struct dentry *dentry) 658 { 659 /* This usage of d_real() results in const dentry */ 660 return d_inode(d_real((struct dentry *) dentry, D_REAL_DATA)); 661 } 662 663 struct name_snapshot { 664 struct qstr name; 665 union shortname_store inline_name; 666 }; 667 bool take_dentry_name_snapshot(struct name_snapshot *, struct dentry *); 668 void release_dentry_name_snapshot(struct name_snapshot *); 669 670 static inline struct dentry *d_first_child(const struct dentry *dentry) 671 { 672 return hlist_entry_safe(dentry->d_children.first, struct dentry, d_sib); 673 } 674 675 static inline struct dentry *d_next_sibling(const struct dentry *dentry) 676 { 677 return hlist_entry_safe(dentry->d_sib.next, struct dentry, d_sib); 678 } 679 680 void set_default_d_op(struct super_block *, const struct dentry_operations *); 681 struct dentry *d_make_persistent(struct dentry *, struct inode *); 682 void d_make_discardable(struct dentry *dentry); 683 684 /* inode->i_lock must be held over that */ 685 #define for_each_alias(dentry, inode) \ 686 hlist_for_each_entry(dentry, &(inode)->i_dentry, d_alias) 687 688 #endif /* __LINUX_DCACHE_H */ 689