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 18struct path; 19struct file; 20struct 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 */ 49struct 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 61extern const struct qstr empty_name; 62extern const struct qstr slash_name; 63extern 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 82struct 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 */ 122enum dentry_d_lock_class 123{ 124 DENTRY_D_LOCK_NORMAL, /* implicitly used by plain spin_lock() APIs. */ 125 DENTRY_D_LOCK_NESTED 126}; 127 128enum d_real_type { 129 D_REAL_DATA, 130 D_REAL_METADATA, 131}; 132 133struct 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 218extern seqlock_t rename_lock; 219 220/* 221 * These are the low-level FS interfaces to the dcache.. 222 */ 223extern void d_instantiate(struct dentry *, struct inode *); 224extern void d_instantiate_new(struct dentry *, struct inode *); 225extern void __d_drop(struct dentry *dentry); 226extern void d_drop(struct dentry *dentry); 227extern void d_delete(struct dentry *); 228extern void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op); 229 230/* allocate/de-allocate */ 231extern struct dentry * d_alloc(struct dentry *, const struct qstr *); 232extern struct dentry * d_alloc_anon(struct super_block *); 233extern struct dentry * d_alloc_parallel(struct dentry *, const struct qstr *, 234 wait_queue_head_t *); 235extern struct dentry * d_splice_alias(struct inode *, struct dentry *); 236extern struct dentry * d_add_ci(struct dentry *, struct inode *, struct qstr *); 237extern bool d_same_name(const struct dentry *dentry, const struct dentry *parent, 238 const struct qstr *name); 239extern struct dentry * d_exact_alias(struct dentry *, struct inode *); 240extern struct dentry *d_find_any_alias(struct inode *inode); 241extern struct dentry * d_obtain_alias(struct inode *); 242extern struct dentry * d_obtain_root(struct inode *); 243extern void shrink_dcache_sb(struct super_block *); 244extern void shrink_dcache_parent(struct dentry *); 245extern void d_invalidate(struct dentry *); 246 247/* only used at mount-time */ 248extern struct dentry * d_make_root(struct inode *); 249 250extern void d_mark_tmpfile(struct file *, struct inode *); 251extern void d_tmpfile(struct file *, struct inode *); 252 253extern struct dentry *d_find_alias(struct inode *); 254extern void d_prune_aliases(struct inode *); 255 256extern struct dentry *d_find_alias_rcu(struct inode *); 257 258/* test whether we have any submounts in a subdir tree */ 259extern int path_has_submounts(const struct path *); 260 261/* 262 * This adds the entry to the hash queues. 263 */ 264extern void d_rehash(struct dentry *); 265 266extern void d_add(struct dentry *, struct inode *); 267 268/* used for rename() and baskets */ 269extern void d_move(struct dentry *, struct dentry *); 270extern void d_exchange(struct dentry *, struct dentry *); 271extern struct dentry *d_ancestor(struct dentry *, struct dentry *); 272 273extern struct dentry *d_lookup(const struct dentry *, const struct qstr *); 274extern struct dentry *d_hash_and_lookup(struct dentry *, struct qstr *); 275 276static inline unsigned d_count(const struct dentry *dentry) 277{ 278 return dentry->d_lockref.count; 279} 280 281/* 282 * helper function for dentry_operations.d_dname() members 283 */ 284extern __printf(3, 4) 285char *dynamic_dname(char *, int, const char *, ...); 286 287extern char *__d_path(const struct path *, const struct path *, char *, int); 288extern char *d_absolute_path(const struct path *, char *, int); 289extern char *d_path(const struct path *, char *, int); 290extern char *dentry_path_raw(const struct dentry *, char *, int); 291extern char *dentry_path(const struct dentry *, char *, int); 292 293/* Allocation counts.. */ 294 295/** 296 * dget_dlock - get a reference to a dentry 297 * @dentry: dentry to get a reference to 298 * 299 * Given a live dentry, increment the reference count and return the dentry. 300 * Caller must hold @dentry->d_lock. Making sure that dentry is alive is 301 * caller's resonsibility. There are many conditions sufficient to guarantee 302 * that; e.g. anything with non-negative refcount is alive, so's anything 303 * hashed, anything positive, anyone's parent, etc. 304 */ 305static inline struct dentry *dget_dlock(struct dentry *dentry) 306{ 307 dentry->d_lockref.count++; 308 return dentry; 309} 310 311 312/** 313 * dget - get a reference to a dentry 314 * @dentry: dentry to get a reference to 315 * 316 * Given a dentry or %NULL pointer increment the reference count 317 * if appropriate and return the dentry. A dentry will not be 318 * destroyed when it has references. Conversely, a dentry with 319 * no references can disappear for any number of reasons, starting 320 * with memory pressure. In other words, that primitive is 321 * used to clone an existing reference; using it on something with 322 * zero refcount is a bug. 323 * 324 * NOTE: it will spin if @dentry->d_lock is held. From the deadlock 325 * avoidance point of view it is equivalent to spin_lock()/increment 326 * refcount/spin_unlock(), so calling it under @dentry->d_lock is 327 * always a bug; so's calling it under ->d_lock on any of its descendents. 328 * 329 */ 330static inline struct dentry *dget(struct dentry *dentry) 331{ 332 if (dentry) 333 lockref_get(&dentry->d_lockref); 334 return dentry; 335} 336 337extern struct dentry *dget_parent(struct dentry *dentry); 338 339/** 340 * d_unhashed - is dentry hashed 341 * @dentry: entry to check 342 * 343 * Returns true if the dentry passed is not currently hashed. 344 */ 345static inline int d_unhashed(const struct dentry *dentry) 346{ 347 return hlist_bl_unhashed(&dentry->d_hash); 348} 349 350static inline int d_unlinked(const struct dentry *dentry) 351{ 352 return d_unhashed(dentry) && !IS_ROOT(dentry); 353} 354 355static inline int cant_mount(const struct dentry *dentry) 356{ 357 return (dentry->d_flags & DCACHE_CANT_MOUNT); 358} 359 360static inline void dont_mount(struct dentry *dentry) 361{ 362 spin_lock(&dentry->d_lock); 363 dentry->d_flags |= DCACHE_CANT_MOUNT; 364 spin_unlock(&dentry->d_lock); 365} 366 367extern void __d_lookup_unhash_wake(struct dentry *dentry); 368 369static inline int d_in_lookup(const struct dentry *dentry) 370{ 371 return dentry->d_flags & DCACHE_PAR_LOOKUP; 372} 373 374static inline void d_lookup_done(struct dentry *dentry) 375{ 376 if (unlikely(d_in_lookup(dentry))) 377 __d_lookup_unhash_wake(dentry); 378} 379 380extern void dput(struct dentry *); 381 382static inline bool d_managed(const struct dentry *dentry) 383{ 384 return dentry->d_flags & DCACHE_MANAGED_DENTRY; 385} 386 387static inline bool d_mountpoint(const struct dentry *dentry) 388{ 389 return dentry->d_flags & DCACHE_MOUNTED; 390} 391 392/* 393 * Directory cache entry type accessor functions. 394 */ 395static inline unsigned __d_entry_type(const struct dentry *dentry) 396{ 397 return dentry->d_flags & DCACHE_ENTRY_TYPE; 398} 399 400static inline bool d_is_miss(const struct dentry *dentry) 401{ 402 return __d_entry_type(dentry) == DCACHE_MISS_TYPE; 403} 404 405static inline bool d_is_whiteout(const struct dentry *dentry) 406{ 407 return __d_entry_type(dentry) == DCACHE_WHITEOUT_TYPE; 408} 409 410static inline bool d_can_lookup(const struct dentry *dentry) 411{ 412 return __d_entry_type(dentry) == DCACHE_DIRECTORY_TYPE; 413} 414 415static inline bool d_is_autodir(const struct dentry *dentry) 416{ 417 return __d_entry_type(dentry) == DCACHE_AUTODIR_TYPE; 418} 419 420static inline bool d_is_dir(const struct dentry *dentry) 421{ 422 return d_can_lookup(dentry) || d_is_autodir(dentry); 423} 424 425static inline bool d_is_symlink(const struct dentry *dentry) 426{ 427 return __d_entry_type(dentry) == DCACHE_SYMLINK_TYPE; 428} 429 430static inline bool d_is_reg(const struct dentry *dentry) 431{ 432 return __d_entry_type(dentry) == DCACHE_REGULAR_TYPE; 433} 434 435static inline bool d_is_special(const struct dentry *dentry) 436{ 437 return __d_entry_type(dentry) == DCACHE_SPECIAL_TYPE; 438} 439 440static inline bool d_is_file(const struct dentry *dentry) 441{ 442 return d_is_reg(dentry) || d_is_special(dentry); 443} 444 445static inline bool d_is_negative(const struct dentry *dentry) 446{ 447 // TODO: check d_is_whiteout(dentry) also. 448 return d_is_miss(dentry); 449} 450 451static inline bool d_flags_negative(unsigned flags) 452{ 453 return (flags & DCACHE_ENTRY_TYPE) == DCACHE_MISS_TYPE; 454} 455 456static inline bool d_is_positive(const struct dentry *dentry) 457{ 458 return !d_is_negative(dentry); 459} 460 461/** 462 * d_really_is_negative - Determine if a dentry is really negative (ignoring fallthroughs) 463 * @dentry: The dentry in question 464 * 465 * Returns true if the dentry represents either an absent name or a name that 466 * doesn't map to an inode (ie. ->d_inode is NULL). The dentry could represent 467 * a true miss, a whiteout that isn't represented by a 0,0 chardev or a 468 * fallthrough marker in an opaque directory. 469 * 470 * Note! (1) This should be used *only* by a filesystem to examine its own 471 * dentries. It should not be used to look at some other filesystem's 472 * dentries. (2) It should also be used in combination with d_inode() to get 473 * the inode. (3) The dentry may have something attached to ->d_lower and the 474 * type field of the flags may be set to something other than miss or whiteout. 475 */ 476static inline bool d_really_is_negative(const struct dentry *dentry) 477{ 478 return dentry->d_inode == NULL; 479} 480 481/** 482 * d_really_is_positive - Determine if a dentry is really positive (ignoring fallthroughs) 483 * @dentry: The dentry in question 484 * 485 * Returns true if the dentry represents a name that maps to an inode 486 * (ie. ->d_inode is not NULL). The dentry might still represent a whiteout if 487 * that is represented on medium as a 0,0 chardev. 488 * 489 * Note! (1) This should be used *only* by a filesystem to examine its own 490 * dentries. It should not be used to look at some other filesystem's 491 * dentries. (2) It should also be used in combination with d_inode() to get 492 * the inode. 493 */ 494static inline bool d_really_is_positive(const struct dentry *dentry) 495{ 496 return dentry->d_inode != NULL; 497} 498 499static inline int simple_positive(const struct dentry *dentry) 500{ 501 return d_really_is_positive(dentry) && !d_unhashed(dentry); 502} 503 504extern int sysctl_vfs_cache_pressure; 505 506static inline unsigned long vfs_pressure_ratio(unsigned long val) 507{ 508 return mult_frac(val, sysctl_vfs_cache_pressure, 100); 509} 510 511/** 512 * d_inode - Get the actual inode of this dentry 513 * @dentry: The dentry to query 514 * 515 * This is the helper normal filesystems should use to get at their own inodes 516 * in their own dentries and ignore the layering superimposed upon them. 517 */ 518static inline struct inode *d_inode(const struct dentry *dentry) 519{ 520 return dentry->d_inode; 521} 522 523/** 524 * d_inode_rcu - Get the actual inode of this dentry with READ_ONCE() 525 * @dentry: The dentry to query 526 * 527 * This is the helper normal filesystems should use to get at their own inodes 528 * in their own dentries and ignore the layering superimposed upon them. 529 */ 530static inline struct inode *d_inode_rcu(const struct dentry *dentry) 531{ 532 return READ_ONCE(dentry->d_inode); 533} 534 535/** 536 * d_backing_inode - Get upper or lower inode we should be using 537 * @upper: The upper layer 538 * 539 * This is the helper that should be used to get at the inode that will be used 540 * if this dentry were to be opened as a file. The inode may be on the upper 541 * dentry or it may be on a lower dentry pinned by the upper. 542 * 543 * Normal filesystems should not use this to access their own inodes. 544 */ 545static inline struct inode *d_backing_inode(const struct dentry *upper) 546{ 547 struct inode *inode = upper->d_inode; 548 549 return inode; 550} 551 552/** 553 * d_real - Return the real dentry 554 * @dentry: the dentry to query 555 * @type: the type of real dentry (data or metadata) 556 * 557 * If dentry is on a union/overlay, then return the underlying, real dentry. 558 * Otherwise return the dentry itself. 559 * 560 * See also: Documentation/filesystems/vfs.rst 561 */ 562static inline struct dentry *d_real(struct dentry *dentry, enum d_real_type type) 563{ 564 if (unlikely(dentry->d_flags & DCACHE_OP_REAL)) 565 return dentry->d_op->d_real(dentry, type); 566 else 567 return dentry; 568} 569 570/** 571 * d_real_inode - Return the real inode hosting the data 572 * @dentry: The dentry to query 573 * 574 * If dentry is on a union/overlay, then return the underlying, real inode. 575 * Otherwise return d_inode(). 576 */ 577static inline struct inode *d_real_inode(const struct dentry *dentry) 578{ 579 /* This usage of d_real() results in const dentry */ 580 return d_inode(d_real((struct dentry *) dentry, D_REAL_DATA)); 581} 582 583struct name_snapshot { 584 struct qstr name; 585 unsigned char inline_name[DNAME_INLINE_LEN]; 586}; 587void take_dentry_name_snapshot(struct name_snapshot *, struct dentry *); 588void release_dentry_name_snapshot(struct name_snapshot *); 589 590static inline struct dentry *d_first_child(const struct dentry *dentry) 591{ 592 return hlist_entry_safe(dentry->d_children.first, struct dentry, d_sib); 593} 594 595static inline struct dentry *d_next_sibling(const struct dentry *dentry) 596{ 597 return hlist_entry_safe(dentry->d_sib.next, struct dentry, d_sib); 598} 599 600#endif /* __LINUX_DCACHE_H */ 601