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 vfsmount; 20 21 /* 22 * linux/include/linux/dcache.h 23 * 24 * Dirent cache data structures 25 * 26 * (C) Copyright 1997 Thomas Schoebel-Theuer, 27 * with heavy changes by Linus Torvalds 28 */ 29 30 #define IS_ROOT(x) ((x) == (x)->d_parent) 31 32 /* The hash is always the low bits of hash_len */ 33 #ifdef __LITTLE_ENDIAN 34 #define HASH_LEN_DECLARE u32 hash; u32 len 35 #define bytemask_from_count(cnt) (~(~0ul << (cnt)*8)) 36 #else 37 #define HASH_LEN_DECLARE u32 len; u32 hash 38 #define bytemask_from_count(cnt) (~(~0ul >> (cnt)*8)) 39 #endif 40 41 /* 42 * "quick string" -- eases parameter passing, but more importantly 43 * saves "metadata" about the string (ie length and the hash). 44 * 45 * hash comes first so it snuggles against d_parent in the 46 * dentry. 47 */ 48 struct qstr { 49 union { 50 struct { 51 HASH_LEN_DECLARE; 52 }; 53 u64 hash_len; 54 }; 55 const unsigned char *name; 56 }; 57 58 #define QSTR_INIT(n,l) { { { .len = l } }, .name = n } 59 60 extern const struct qstr empty_name; 61 extern const struct qstr slash_name; 62 63 struct dentry_stat_t { 64 long nr_dentry; 65 long nr_unused; 66 long age_limit; /* age in seconds */ 67 long want_pages; /* pages requested by system */ 68 long nr_negative; /* # of unused negative dentries */ 69 long dummy; /* Reserved for future use */ 70 }; 71 extern struct dentry_stat_t dentry_stat; 72 73 /* 74 * Try to keep struct dentry aligned on 64 byte cachelines (this will 75 * give reasonable cacheline footprint with larger lines without the 76 * large memory footprint increase). 77 */ 78 #ifdef CONFIG_64BIT 79 # define DNAME_INLINE_LEN 32 /* 192 bytes */ 80 #else 81 # ifdef CONFIG_SMP 82 # define DNAME_INLINE_LEN 36 /* 128 bytes */ 83 # else 84 # define DNAME_INLINE_LEN 40 /* 128 bytes */ 85 # endif 86 #endif 87 88 #define d_lock d_lockref.lock 89 90 struct dentry { 91 /* RCU lookup touched fields */ 92 unsigned int d_flags; /* protected by d_lock */ 93 seqcount_spinlock_t d_seq; /* per dentry seqlock */ 94 struct hlist_bl_node d_hash; /* lookup hash list */ 95 struct dentry *d_parent; /* parent directory */ 96 struct qstr d_name; 97 struct inode *d_inode; /* Where the name belongs to - NULL is 98 * negative */ 99 unsigned char d_iname[DNAME_INLINE_LEN]; /* small names */ 100 101 /* Ref lookup also touches following */ 102 struct lockref d_lockref; /* per-dentry lock and refcount */ 103 const struct dentry_operations *d_op; 104 struct super_block *d_sb; /* The root of the dentry tree */ 105 unsigned long d_time; /* used by d_revalidate */ 106 void *d_fsdata; /* fs-specific data */ 107 108 union { 109 struct list_head d_lru; /* LRU list */ 110 wait_queue_head_t *d_wait; /* in-lookup ones only */ 111 }; 112 struct list_head d_child; /* child of parent list */ 113 struct list_head d_subdirs; /* our children */ 114 /* 115 * d_alias and d_rcu can share memory 116 */ 117 union { 118 struct hlist_node d_alias; /* inode alias list */ 119 struct hlist_bl_node d_in_lookup_hash; /* only for in-lookup ones */ 120 struct rcu_head d_rcu; 121 } d_u; 122 } __randomize_layout; 123 124 /* 125 * dentry->d_lock spinlock nesting subclasses: 126 * 127 * 0: normal 128 * 1: nested 129 */ 130 enum dentry_d_lock_class 131 { 132 DENTRY_D_LOCK_NORMAL, /* implicitly used by plain spin_lock() APIs. */ 133 DENTRY_D_LOCK_NESTED 134 }; 135 136 struct dentry_operations { 137 int (*d_revalidate)(struct dentry *, unsigned int); 138 int (*d_weak_revalidate)(struct dentry *, unsigned int); 139 int (*d_hash)(const struct dentry *, struct qstr *); 140 int (*d_compare)(const struct dentry *, 141 unsigned int, const char *, const struct qstr *); 142 int (*d_delete)(const struct dentry *); 143 int (*d_init)(struct dentry *); 144 void (*d_release)(struct dentry *); 145 void (*d_prune)(struct dentry *); 146 void (*d_iput)(struct dentry *, struct inode *); 147 char *(*d_dname)(struct dentry *, char *, int); 148 struct vfsmount *(*d_automount)(struct path *); 149 int (*d_manage)(const struct path *, bool); 150 struct dentry *(*d_real)(struct dentry *, const struct inode *); 151 } ____cacheline_aligned; 152 153 /* 154 * Locking rules for dentry_operations callbacks are to be found in 155 * Documentation/filesystems/locking.rst. Keep it updated! 156 * 157 * FUrther descriptions are found in Documentation/filesystems/vfs.rst. 158 * Keep it updated too! 159 */ 160 161 /* d_flags entries */ 162 #define DCACHE_OP_HASH 0x00000001 163 #define DCACHE_OP_COMPARE 0x00000002 164 #define DCACHE_OP_REVALIDATE 0x00000004 165 #define DCACHE_OP_DELETE 0x00000008 166 #define DCACHE_OP_PRUNE 0x00000010 167 168 #define DCACHE_DISCONNECTED 0x00000020 169 /* This dentry is possibly not currently connected to the dcache tree, in 170 * which case its parent will either be itself, or will have this flag as 171 * well. nfsd will not use a dentry with this bit set, but will first 172 * endeavour to clear the bit either by discovering that it is connected, 173 * or by performing lookup operations. Any filesystem which supports 174 * nfsd_operations MUST have a lookup function which, if it finds a 175 * directory inode with a DCACHE_DISCONNECTED dentry, will d_move that 176 * dentry into place and return that dentry rather than the passed one, 177 * typically using d_splice_alias. */ 178 179 #define DCACHE_REFERENCED 0x00000040 /* Recently used, don't discard. */ 180 181 #define DCACHE_DONTCACHE 0x00000080 /* Purge from memory on final dput() */ 182 183 #define DCACHE_CANT_MOUNT 0x00000100 184 #define DCACHE_GENOCIDE 0x00000200 185 #define DCACHE_SHRINK_LIST 0x00000400 186 187 #define DCACHE_OP_WEAK_REVALIDATE 0x00000800 188 189 #define DCACHE_NFSFS_RENAMED 0x00001000 190 /* this dentry has been "silly renamed" and has to be deleted on the last 191 * dput() */ 192 #define DCACHE_COOKIE 0x00002000 /* For use by dcookie subsystem */ 193 #define DCACHE_FSNOTIFY_PARENT_WATCHED 0x00004000 194 /* Parent inode is watched by some fsnotify listener */ 195 196 #define DCACHE_DENTRY_KILLED 0x00008000 197 198 #define DCACHE_MOUNTED 0x00010000 /* is a mountpoint */ 199 #define DCACHE_NEED_AUTOMOUNT 0x00020000 /* handle automount on this dir */ 200 #define DCACHE_MANAGE_TRANSIT 0x00040000 /* manage transit from this dirent */ 201 #define DCACHE_MANAGED_DENTRY \ 202 (DCACHE_MOUNTED|DCACHE_NEED_AUTOMOUNT|DCACHE_MANAGE_TRANSIT) 203 204 #define DCACHE_LRU_LIST 0x00080000 205 206 #define DCACHE_ENTRY_TYPE 0x00700000 207 #define DCACHE_MISS_TYPE 0x00000000 /* Negative dentry (maybe fallthru to nowhere) */ 208 #define DCACHE_WHITEOUT_TYPE 0x00100000 /* Whiteout dentry (stop pathwalk) */ 209 #define DCACHE_DIRECTORY_TYPE 0x00200000 /* Normal directory */ 210 #define DCACHE_AUTODIR_TYPE 0x00300000 /* Lookupless directory (presumed automount) */ 211 #define DCACHE_REGULAR_TYPE 0x00400000 /* Regular file type (or fallthru to such) */ 212 #define DCACHE_SPECIAL_TYPE 0x00500000 /* Other file type (or fallthru to such) */ 213 #define DCACHE_SYMLINK_TYPE 0x00600000 /* Symlink (or fallthru to such) */ 214 215 #define DCACHE_MAY_FREE 0x00800000 216 #define DCACHE_FALLTHRU 0x01000000 /* Fall through to lower layer */ 217 #define DCACHE_NOKEY_NAME 0x02000000 /* Encrypted name encoded without key */ 218 #define DCACHE_OP_REAL 0x04000000 219 220 #define DCACHE_PAR_LOOKUP 0x10000000 /* being looked up (with parent locked shared) */ 221 #define DCACHE_DENTRY_CURSOR 0x20000000 222 #define DCACHE_NORCU 0x40000000 /* No RCU delay for freeing */ 223 224 extern seqlock_t rename_lock; 225 226 /* 227 * These are the low-level FS interfaces to the dcache.. 228 */ 229 extern void d_instantiate(struct dentry *, struct inode *); 230 extern void d_instantiate_new(struct dentry *, struct inode *); 231 extern struct dentry * d_instantiate_unique(struct dentry *, struct inode *); 232 extern struct dentry * d_instantiate_anon(struct dentry *, struct inode *); 233 extern void __d_drop(struct dentry *dentry); 234 extern void d_drop(struct dentry *dentry); 235 extern void d_delete(struct dentry *); 236 extern void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op); 237 238 /* allocate/de-allocate */ 239 extern struct dentry * d_alloc(struct dentry *, const struct qstr *); 240 extern struct dentry * d_alloc_anon(struct super_block *); 241 extern struct dentry * d_alloc_parallel(struct dentry *, const struct qstr *, 242 wait_queue_head_t *); 243 extern struct dentry * d_splice_alias(struct inode *, struct dentry *); 244 extern struct dentry * d_add_ci(struct dentry *, struct inode *, struct qstr *); 245 extern struct dentry * d_exact_alias(struct dentry *, struct inode *); 246 extern struct dentry *d_find_any_alias(struct inode *inode); 247 extern struct dentry * d_obtain_alias(struct inode *); 248 extern struct dentry * d_obtain_root(struct inode *); 249 extern void shrink_dcache_sb(struct super_block *); 250 extern void shrink_dcache_parent(struct dentry *); 251 extern void shrink_dcache_for_umount(struct super_block *); 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 /* <clickety>-<click> the ramfs-type tree */ 258 extern void d_genocide(struct dentry *); 259 260 extern void d_tmpfile(struct dentry *, struct inode *); 261 262 extern struct dentry *d_find_alias(struct inode *); 263 extern void d_prune_aliases(struct inode *); 264 265 extern struct dentry *d_find_alias_rcu(struct inode *); 266 267 /* test whether we have any submounts in a subdir tree */ 268 extern int path_has_submounts(const struct path *); 269 270 /* 271 * This adds the entry to the hash queues. 272 */ 273 extern void d_rehash(struct dentry *); 274 275 extern void d_add(struct dentry *, struct inode *); 276 277 /* used for rename() and baskets */ 278 extern void d_move(struct dentry *, struct dentry *); 279 extern void d_exchange(struct dentry *, struct dentry *); 280 extern struct dentry *d_ancestor(struct dentry *, struct dentry *); 281 282 /* appendix may either be NULL or be used for transname suffixes */ 283 extern struct dentry *d_lookup(const struct dentry *, const struct qstr *); 284 extern struct dentry *d_hash_and_lookup(struct dentry *, struct qstr *); 285 extern struct dentry *__d_lookup(const struct dentry *, const struct qstr *); 286 extern struct dentry *__d_lookup_rcu(const struct dentry *parent, 287 const struct qstr *name, unsigned *seq); 288 289 static inline unsigned d_count(const struct dentry *dentry) 290 { 291 return dentry->d_lockref.count; 292 } 293 294 /* 295 * helper function for dentry_operations.d_dname() members 296 */ 297 extern __printf(4, 5) 298 char *dynamic_dname(struct dentry *, char *, int, const char *, ...); 299 300 extern char *__d_path(const struct path *, const struct path *, char *, int); 301 extern char *d_absolute_path(const struct path *, char *, int); 302 extern char *d_path(const struct path *, char *, int); 303 extern char *dentry_path_raw(struct dentry *, char *, int); 304 extern char *dentry_path(struct dentry *, char *, int); 305 306 /* Allocation counts.. */ 307 308 /** 309 * dget, dget_dlock - get a reference to a dentry 310 * @dentry: dentry to get a reference to 311 * 312 * Given a dentry or %NULL pointer increment the reference count 313 * if appropriate and return the dentry. A dentry will not be 314 * destroyed when it has references. 315 */ 316 static inline struct dentry *dget_dlock(struct dentry *dentry) 317 { 318 if (dentry) 319 dentry->d_lockref.count++; 320 return dentry; 321 } 322 323 static inline struct dentry *dget(struct dentry *dentry) 324 { 325 if (dentry) 326 lockref_get(&dentry->d_lockref); 327 return dentry; 328 } 329 330 extern struct dentry *dget_parent(struct dentry *dentry); 331 332 /** 333 * d_unhashed - is dentry hashed 334 * @dentry: entry to check 335 * 336 * Returns true if the dentry passed is not currently hashed. 337 */ 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_done(struct 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 spin_lock(&dentry->d_lock); 372 __d_lookup_done(dentry); 373 spin_unlock(&dentry->d_lock); 374 } 375 } 376 377 extern void dput(struct dentry *); 378 379 static inline bool d_managed(const struct dentry *dentry) 380 { 381 return dentry->d_flags & DCACHE_MANAGED_DENTRY; 382 } 383 384 static inline bool d_mountpoint(const struct dentry *dentry) 385 { 386 return dentry->d_flags & DCACHE_MOUNTED; 387 } 388 389 /* 390 * Directory cache entry type accessor functions. 391 */ 392 static inline unsigned __d_entry_type(const struct dentry *dentry) 393 { 394 return dentry->d_flags & DCACHE_ENTRY_TYPE; 395 } 396 397 static inline bool d_is_miss(const struct dentry *dentry) 398 { 399 return __d_entry_type(dentry) == DCACHE_MISS_TYPE; 400 } 401 402 static inline bool d_is_whiteout(const struct dentry *dentry) 403 { 404 return __d_entry_type(dentry) == DCACHE_WHITEOUT_TYPE; 405 } 406 407 static inline bool d_can_lookup(const struct dentry *dentry) 408 { 409 return __d_entry_type(dentry) == DCACHE_DIRECTORY_TYPE; 410 } 411 412 static inline bool d_is_autodir(const struct dentry *dentry) 413 { 414 return __d_entry_type(dentry) == DCACHE_AUTODIR_TYPE; 415 } 416 417 static inline bool d_is_dir(const struct dentry *dentry) 418 { 419 return d_can_lookup(dentry) || d_is_autodir(dentry); 420 } 421 422 static inline bool d_is_symlink(const struct dentry *dentry) 423 { 424 return __d_entry_type(dentry) == DCACHE_SYMLINK_TYPE; 425 } 426 427 static inline bool d_is_reg(const struct dentry *dentry) 428 { 429 return __d_entry_type(dentry) == DCACHE_REGULAR_TYPE; 430 } 431 432 static inline bool d_is_special(const struct dentry *dentry) 433 { 434 return __d_entry_type(dentry) == DCACHE_SPECIAL_TYPE; 435 } 436 437 static inline bool d_is_file(const struct dentry *dentry) 438 { 439 return d_is_reg(dentry) || d_is_special(dentry); 440 } 441 442 static inline bool d_is_negative(const struct dentry *dentry) 443 { 444 // TODO: check d_is_whiteout(dentry) also. 445 return d_is_miss(dentry); 446 } 447 448 static inline bool d_flags_negative(unsigned flags) 449 { 450 return (flags & DCACHE_ENTRY_TYPE) == DCACHE_MISS_TYPE; 451 } 452 453 static inline bool d_is_positive(const struct dentry *dentry) 454 { 455 return !d_is_negative(dentry); 456 } 457 458 /** 459 * d_really_is_negative - Determine if a dentry is really negative (ignoring fallthroughs) 460 * @dentry: The dentry in question 461 * 462 * Returns true if the dentry represents either an absent name or a name that 463 * doesn't map to an inode (ie. ->d_inode is NULL). The dentry could represent 464 * a true miss, a whiteout that isn't represented by a 0,0 chardev or a 465 * fallthrough marker in an opaque directory. 466 * 467 * Note! (1) This should be used *only* by a filesystem to examine its own 468 * dentries. It should not be used to look at some other filesystem's 469 * dentries. (2) It should also be used in combination with d_inode() to get 470 * the inode. (3) The dentry may have something attached to ->d_lower and the 471 * type field of the flags may be set to something other than miss or whiteout. 472 */ 473 static inline bool d_really_is_negative(const struct dentry *dentry) 474 { 475 return dentry->d_inode == NULL; 476 } 477 478 /** 479 * d_really_is_positive - Determine if a dentry is really positive (ignoring fallthroughs) 480 * @dentry: The dentry in question 481 * 482 * Returns true if the dentry represents a name that maps to an inode 483 * (ie. ->d_inode is not NULL). The dentry might still represent a whiteout if 484 * that is represented on medium as a 0,0 chardev. 485 * 486 * Note! (1) This should be used *only* by a filesystem to examine its own 487 * dentries. It should not be used to look at some other filesystem's 488 * dentries. (2) It should also be used in combination with d_inode() to get 489 * the inode. 490 */ 491 static inline bool d_really_is_positive(const struct dentry *dentry) 492 { 493 return dentry->d_inode != NULL; 494 } 495 496 static inline int simple_positive(const struct dentry *dentry) 497 { 498 return d_really_is_positive(dentry) && !d_unhashed(dentry); 499 } 500 501 extern void d_set_fallthru(struct dentry *dentry); 502 503 static inline bool d_is_fallthru(const struct dentry *dentry) 504 { 505 return dentry->d_flags & DCACHE_FALLTHRU; 506 } 507 508 509 extern int sysctl_vfs_cache_pressure; 510 511 static inline unsigned long vfs_pressure_ratio(unsigned long val) 512 { 513 return mult_frac(val, sysctl_vfs_cache_pressure, 100); 514 } 515 516 /** 517 * d_inode - Get the actual inode of this dentry 518 * @dentry: The dentry to query 519 * 520 * This is the helper normal filesystems should use to get at their own inodes 521 * in their own dentries and ignore the layering superimposed upon them. 522 */ 523 static inline struct inode *d_inode(const struct dentry *dentry) 524 { 525 return dentry->d_inode; 526 } 527 528 /** 529 * d_inode_rcu - Get the actual inode of this dentry with READ_ONCE() 530 * @dentry: The dentry to query 531 * 532 * This is the helper normal filesystems should use to get at their own inodes 533 * in their own dentries and ignore the layering superimposed upon them. 534 */ 535 static inline struct inode *d_inode_rcu(const struct dentry *dentry) 536 { 537 return READ_ONCE(dentry->d_inode); 538 } 539 540 /** 541 * d_backing_inode - Get upper or lower inode we should be using 542 * @upper: The upper layer 543 * 544 * This is the helper that should be used to get at the inode that will be used 545 * if this dentry were to be opened as a file. The inode may be on the upper 546 * dentry or it may be on a lower dentry pinned by the upper. 547 * 548 * Normal filesystems should not use this to access their own inodes. 549 */ 550 static inline struct inode *d_backing_inode(const struct dentry *upper) 551 { 552 struct inode *inode = upper->d_inode; 553 554 return inode; 555 } 556 557 /** 558 * d_backing_dentry - Get upper or lower dentry we should be using 559 * @upper: The upper layer 560 * 561 * This is the helper that should be used to get the dentry of the inode that 562 * will be used if this dentry were opened as a file. It may be the upper 563 * dentry or it may be a lower dentry pinned by the upper. 564 * 565 * Normal filesystems should not use this to access their own dentries. 566 */ 567 static inline struct dentry *d_backing_dentry(struct dentry *upper) 568 { 569 return upper; 570 } 571 572 /** 573 * d_real - Return the real dentry 574 * @dentry: the dentry to query 575 * @inode: inode to select the dentry from multiple layers (can be NULL) 576 * 577 * If dentry is on a union/overlay, then return the underlying, real dentry. 578 * Otherwise return the dentry itself. 579 * 580 * See also: Documentation/filesystems/vfs.rst 581 */ 582 static inline struct dentry *d_real(struct dentry *dentry, 583 const struct inode *inode) 584 { 585 if (unlikely(dentry->d_flags & DCACHE_OP_REAL)) 586 return dentry->d_op->d_real(dentry, inode); 587 else 588 return dentry; 589 } 590 591 /** 592 * d_real_inode - Return the real inode 593 * @dentry: The dentry to query 594 * 595 * If dentry is on a union/overlay, then return the underlying, real inode. 596 * Otherwise return d_inode(). 597 */ 598 static inline struct inode *d_real_inode(const struct dentry *dentry) 599 { 600 /* This usage of d_real() results in const dentry */ 601 return d_backing_inode(d_real((struct dentry *) dentry, NULL)); 602 } 603 604 struct name_snapshot { 605 struct qstr name; 606 unsigned char inline_name[DNAME_INLINE_LEN]; 607 }; 608 void take_dentry_name_snapshot(struct name_snapshot *, struct dentry *); 609 void release_dentry_name_snapshot(struct name_snapshot *); 610 611 #endif /* __LINUX_DCACHE_H */ 612