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 extern const struct qstr dotdot_name; 63 64 struct dentry_stat_t { 65 long nr_dentry; 66 long nr_unused; 67 long age_limit; /* age in seconds */ 68 long want_pages; /* pages requested by system */ 69 long nr_negative; /* # of unused negative dentries */ 70 long dummy; /* Reserved for future use */ 71 }; 72 extern struct dentry_stat_t dentry_stat; 73 74 /* 75 * Try to keep struct dentry aligned on 64 byte cachelines (this will 76 * give reasonable cacheline footprint with larger lines without the 77 * large memory footprint increase). 78 */ 79 #ifdef CONFIG_64BIT 80 # define DNAME_INLINE_LEN 32 /* 192 bytes */ 81 #else 82 # ifdef CONFIG_SMP 83 # define DNAME_INLINE_LEN 36 /* 128 bytes */ 84 # else 85 # define DNAME_INLINE_LEN 40 /* 128 bytes */ 86 # endif 87 #endif 88 89 #define d_lock d_lockref.lock 90 91 struct dentry { 92 /* RCU lookup touched fields */ 93 unsigned int d_flags; /* protected by d_lock */ 94 seqcount_spinlock_t d_seq; /* per dentry seqlock */ 95 struct hlist_bl_node d_hash; /* lookup hash list */ 96 struct dentry *d_parent; /* parent directory */ 97 struct qstr d_name; 98 struct inode *d_inode; /* Where the name belongs to - NULL is 99 * negative */ 100 unsigned char d_iname[DNAME_INLINE_LEN]; /* small names */ 101 102 /* Ref lookup also touches following */ 103 struct lockref d_lockref; /* per-dentry lock and refcount */ 104 const struct dentry_operations *d_op; 105 struct super_block *d_sb; /* The root of the dentry tree */ 106 unsigned long d_time; /* used by d_revalidate */ 107 void *d_fsdata; /* fs-specific data */ 108 109 union { 110 struct list_head d_lru; /* LRU list */ 111 wait_queue_head_t *d_wait; /* in-lookup ones only */ 112 }; 113 struct list_head d_child; /* child of parent list */ 114 struct list_head d_subdirs; /* our children */ 115 /* 116 * d_alias and d_rcu can share memory 117 */ 118 union { 119 struct hlist_node d_alias; /* inode alias list */ 120 struct hlist_bl_node d_in_lookup_hash; /* only for in-lookup ones */ 121 struct rcu_head d_rcu; 122 } d_u; 123 } __randomize_layout; 124 125 /* 126 * dentry->d_lock spinlock nesting subclasses: 127 * 128 * 0: normal 129 * 1: nested 130 */ 131 enum dentry_d_lock_class 132 { 133 DENTRY_D_LOCK_NORMAL, /* implicitly used by plain spin_lock() APIs. */ 134 DENTRY_D_LOCK_NESTED 135 }; 136 137 struct dentry_operations { 138 int (*d_revalidate)(struct dentry *, unsigned int); 139 int (*d_weak_revalidate)(struct dentry *, unsigned int); 140 int (*d_hash)(const struct dentry *, struct qstr *); 141 int (*d_compare)(const struct dentry *, 142 unsigned int, const char *, const struct qstr *); 143 int (*d_delete)(const struct dentry *); 144 int (*d_init)(struct dentry *); 145 void (*d_release)(struct dentry *); 146 void (*d_prune)(struct dentry *); 147 void (*d_iput)(struct dentry *, struct inode *); 148 char *(*d_dname)(struct dentry *, char *, int); 149 struct vfsmount *(*d_automount)(struct path *); 150 int (*d_manage)(const struct path *, bool); 151 struct dentry *(*d_real)(struct dentry *, const struct inode *); 152 } ____cacheline_aligned; 153 154 /* 155 * Locking rules for dentry_operations callbacks are to be found in 156 * Documentation/filesystems/locking.rst. Keep it updated! 157 * 158 * FUrther descriptions are found in Documentation/filesystems/vfs.rst. 159 * Keep it updated too! 160 */ 161 162 /* d_flags entries */ 163 #define DCACHE_OP_HASH 0x00000001 164 #define DCACHE_OP_COMPARE 0x00000002 165 #define DCACHE_OP_REVALIDATE 0x00000004 166 #define DCACHE_OP_DELETE 0x00000008 167 #define DCACHE_OP_PRUNE 0x00000010 168 169 #define DCACHE_DISCONNECTED 0x00000020 170 /* This dentry is possibly not currently connected to the dcache tree, in 171 * which case its parent will either be itself, or will have this flag as 172 * well. nfsd will not use a dentry with this bit set, but will first 173 * endeavour to clear the bit either by discovering that it is connected, 174 * or by performing lookup operations. Any filesystem which supports 175 * nfsd_operations MUST have a lookup function which, if it finds a 176 * directory inode with a DCACHE_DISCONNECTED dentry, will d_move that 177 * dentry into place and return that dentry rather than the passed one, 178 * typically using d_splice_alias. */ 179 180 #define DCACHE_REFERENCED 0x00000040 /* Recently used, don't discard. */ 181 182 #define DCACHE_DONTCACHE 0x00000080 /* Purge from memory on final dput() */ 183 184 #define DCACHE_CANT_MOUNT 0x00000100 185 #define DCACHE_GENOCIDE 0x00000200 186 #define DCACHE_SHRINK_LIST 0x00000400 187 188 #define DCACHE_OP_WEAK_REVALIDATE 0x00000800 189 190 #define DCACHE_NFSFS_RENAMED 0x00001000 191 /* this dentry has been "silly renamed" and has to be deleted on the last 192 * dput() */ 193 #define DCACHE_COOKIE 0x00002000 /* For use by dcookie subsystem */ 194 #define DCACHE_FSNOTIFY_PARENT_WATCHED 0x00004000 195 /* Parent inode is watched by some fsnotify listener */ 196 197 #define DCACHE_DENTRY_KILLED 0x00008000 198 199 #define DCACHE_MOUNTED 0x00010000 /* is a mountpoint */ 200 #define DCACHE_NEED_AUTOMOUNT 0x00020000 /* handle automount on this dir */ 201 #define DCACHE_MANAGE_TRANSIT 0x00040000 /* manage transit from this dirent */ 202 #define DCACHE_MANAGED_DENTRY \ 203 (DCACHE_MOUNTED|DCACHE_NEED_AUTOMOUNT|DCACHE_MANAGE_TRANSIT) 204 205 #define DCACHE_LRU_LIST 0x00080000 206 207 #define DCACHE_ENTRY_TYPE 0x00700000 208 #define DCACHE_MISS_TYPE 0x00000000 /* Negative dentry (maybe fallthru to nowhere) */ 209 #define DCACHE_WHITEOUT_TYPE 0x00100000 /* Whiteout dentry (stop pathwalk) */ 210 #define DCACHE_DIRECTORY_TYPE 0x00200000 /* Normal directory */ 211 #define DCACHE_AUTODIR_TYPE 0x00300000 /* Lookupless directory (presumed automount) */ 212 #define DCACHE_REGULAR_TYPE 0x00400000 /* Regular file type (or fallthru to such) */ 213 #define DCACHE_SPECIAL_TYPE 0x00500000 /* Other file type (or fallthru to such) */ 214 #define DCACHE_SYMLINK_TYPE 0x00600000 /* Symlink (or fallthru to such) */ 215 216 #define DCACHE_MAY_FREE 0x00800000 217 #define DCACHE_FALLTHRU 0x01000000 /* Fall through to lower layer */ 218 #define DCACHE_NOKEY_NAME 0x02000000 /* Encrypted name encoded without key */ 219 #define DCACHE_OP_REAL 0x04000000 220 221 #define DCACHE_PAR_LOOKUP 0x10000000 /* being looked up (with parent locked shared) */ 222 #define DCACHE_DENTRY_CURSOR 0x20000000 223 #define DCACHE_NORCU 0x40000000 /* No RCU delay for freeing */ 224 225 extern seqlock_t rename_lock; 226 227 /* 228 * These are the low-level FS interfaces to the dcache.. 229 */ 230 extern void d_instantiate(struct dentry *, struct inode *); 231 extern void d_instantiate_new(struct dentry *, struct inode *); 232 extern struct dentry * d_instantiate_unique(struct dentry *, struct inode *); 233 extern struct dentry * d_instantiate_anon(struct dentry *, struct inode *); 234 extern void __d_drop(struct dentry *dentry); 235 extern void d_drop(struct dentry *dentry); 236 extern void d_delete(struct dentry *); 237 extern void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op); 238 239 /* allocate/de-allocate */ 240 extern struct dentry * d_alloc(struct dentry *, const struct qstr *); 241 extern struct dentry * d_alloc_anon(struct super_block *); 242 extern struct dentry * d_alloc_parallel(struct dentry *, const struct qstr *, 243 wait_queue_head_t *); 244 extern struct dentry * d_splice_alias(struct inode *, struct dentry *); 245 extern struct dentry * d_add_ci(struct dentry *, struct inode *, struct qstr *); 246 extern struct dentry * d_exact_alias(struct dentry *, struct inode *); 247 extern struct dentry *d_find_any_alias(struct inode *inode); 248 extern struct dentry * d_obtain_alias(struct inode *); 249 extern struct dentry * d_obtain_root(struct inode *); 250 extern void shrink_dcache_sb(struct super_block *); 251 extern void shrink_dcache_parent(struct dentry *); 252 extern void shrink_dcache_for_umount(struct super_block *); 253 extern void d_invalidate(struct dentry *); 254 255 /* only used at mount-time */ 256 extern struct dentry * d_make_root(struct inode *); 257 258 /* <clickety>-<click> the ramfs-type tree */ 259 extern void d_genocide(struct dentry *); 260 261 extern void d_tmpfile(struct dentry *, struct inode *); 262 263 extern struct dentry *d_find_alias(struct inode *); 264 extern void d_prune_aliases(struct inode *); 265 266 extern struct dentry *d_find_alias_rcu(struct inode *); 267 268 /* test whether we have any submounts in a subdir tree */ 269 extern int path_has_submounts(const struct path *); 270 271 /* 272 * This adds the entry to the hash queues. 273 */ 274 extern void d_rehash(struct dentry *); 275 276 extern void d_add(struct dentry *, struct inode *); 277 278 /* used for rename() and baskets */ 279 extern void d_move(struct dentry *, struct dentry *); 280 extern void d_exchange(struct dentry *, struct dentry *); 281 extern struct dentry *d_ancestor(struct dentry *, struct dentry *); 282 283 /* appendix may either be NULL or be used for transname suffixes */ 284 extern struct dentry *d_lookup(const struct dentry *, const struct qstr *); 285 extern struct dentry *d_hash_and_lookup(struct dentry *, struct qstr *); 286 extern struct dentry *__d_lookup(const struct dentry *, const struct qstr *); 287 extern struct dentry *__d_lookup_rcu(const struct dentry *parent, 288 const struct qstr *name, unsigned *seq); 289 290 static inline unsigned d_count(const struct dentry *dentry) 291 { 292 return dentry->d_lockref.count; 293 } 294 295 /* 296 * helper function for dentry_operations.d_dname() members 297 */ 298 extern __printf(4, 5) 299 char *dynamic_dname(struct dentry *, char *, int, const char *, ...); 300 301 extern char *__d_path(const struct path *, const struct path *, char *, int); 302 extern char *d_absolute_path(const struct path *, char *, int); 303 extern char *d_path(const struct path *, char *, int); 304 extern char *dentry_path_raw(const struct dentry *, char *, int); 305 extern char *dentry_path(const struct dentry *, char *, int); 306 307 /* Allocation counts.. */ 308 309 /** 310 * dget, dget_dlock - get a reference to a dentry 311 * @dentry: dentry to get a reference to 312 * 313 * Given a dentry or %NULL pointer increment the reference count 314 * if appropriate and return the dentry. A dentry will not be 315 * destroyed when it has references. 316 */ 317 static inline struct dentry *dget_dlock(struct dentry *dentry) 318 { 319 if (dentry) 320 dentry->d_lockref.count++; 321 return dentry; 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 */ 339 340 static inline int d_unhashed(const struct dentry *dentry) 341 { 342 return hlist_bl_unhashed(&dentry->d_hash); 343 } 344 345 static inline int d_unlinked(const struct dentry *dentry) 346 { 347 return d_unhashed(dentry) && !IS_ROOT(dentry); 348 } 349 350 static inline int cant_mount(const struct dentry *dentry) 351 { 352 return (dentry->d_flags & DCACHE_CANT_MOUNT); 353 } 354 355 static inline void dont_mount(struct dentry *dentry) 356 { 357 spin_lock(&dentry->d_lock); 358 dentry->d_flags |= DCACHE_CANT_MOUNT; 359 spin_unlock(&dentry->d_lock); 360 } 361 362 extern void __d_lookup_done(struct dentry *); 363 364 static inline int d_in_lookup(const struct dentry *dentry) 365 { 366 return dentry->d_flags & DCACHE_PAR_LOOKUP; 367 } 368 369 static inline void d_lookup_done(struct dentry *dentry) 370 { 371 if (unlikely(d_in_lookup(dentry))) { 372 spin_lock(&dentry->d_lock); 373 __d_lookup_done(dentry); 374 spin_unlock(&dentry->d_lock); 375 } 376 } 377 378 extern void dput(struct dentry *); 379 380 static inline bool d_managed(const struct dentry *dentry) 381 { 382 return dentry->d_flags & DCACHE_MANAGED_DENTRY; 383 } 384 385 static inline bool d_mountpoint(const struct dentry *dentry) 386 { 387 return dentry->d_flags & DCACHE_MOUNTED; 388 } 389 390 /* 391 * Directory cache entry type accessor functions. 392 */ 393 static inline unsigned __d_entry_type(const struct dentry *dentry) 394 { 395 return dentry->d_flags & DCACHE_ENTRY_TYPE; 396 } 397 398 static inline bool d_is_miss(const struct dentry *dentry) 399 { 400 return __d_entry_type(dentry) == DCACHE_MISS_TYPE; 401 } 402 403 static inline bool d_is_whiteout(const struct dentry *dentry) 404 { 405 return __d_entry_type(dentry) == DCACHE_WHITEOUT_TYPE; 406 } 407 408 static inline bool d_can_lookup(const struct dentry *dentry) 409 { 410 return __d_entry_type(dentry) == DCACHE_DIRECTORY_TYPE; 411 } 412 413 static inline bool d_is_autodir(const struct dentry *dentry) 414 { 415 return __d_entry_type(dentry) == DCACHE_AUTODIR_TYPE; 416 } 417 418 static inline bool d_is_dir(const struct dentry *dentry) 419 { 420 return d_can_lookup(dentry) || d_is_autodir(dentry); 421 } 422 423 static inline bool d_is_symlink(const struct dentry *dentry) 424 { 425 return __d_entry_type(dentry) == DCACHE_SYMLINK_TYPE; 426 } 427 428 static inline bool d_is_reg(const struct dentry *dentry) 429 { 430 return __d_entry_type(dentry) == DCACHE_REGULAR_TYPE; 431 } 432 433 static inline bool d_is_special(const struct dentry *dentry) 434 { 435 return __d_entry_type(dentry) == DCACHE_SPECIAL_TYPE; 436 } 437 438 static inline bool d_is_file(const struct dentry *dentry) 439 { 440 return d_is_reg(dentry) || d_is_special(dentry); 441 } 442 443 static inline bool d_is_negative(const struct dentry *dentry) 444 { 445 // TODO: check d_is_whiteout(dentry) also. 446 return d_is_miss(dentry); 447 } 448 449 static inline bool d_flags_negative(unsigned flags) 450 { 451 return (flags & DCACHE_ENTRY_TYPE) == DCACHE_MISS_TYPE; 452 } 453 454 static inline bool d_is_positive(const struct dentry *dentry) 455 { 456 return !d_is_negative(dentry); 457 } 458 459 /** 460 * d_really_is_negative - Determine if a dentry is really negative (ignoring fallthroughs) 461 * @dentry: The dentry in question 462 * 463 * Returns true if the dentry represents either an absent name or a name that 464 * doesn't map to an inode (ie. ->d_inode is NULL). The dentry could represent 465 * a true miss, a whiteout that isn't represented by a 0,0 chardev or a 466 * fallthrough marker in an opaque directory. 467 * 468 * Note! (1) This should be used *only* by a filesystem to examine its own 469 * dentries. It should not be used to look at some other filesystem's 470 * dentries. (2) It should also be used in combination with d_inode() to get 471 * the inode. (3) The dentry may have something attached to ->d_lower and the 472 * type field of the flags may be set to something other than miss or whiteout. 473 */ 474 static inline bool d_really_is_negative(const struct dentry *dentry) 475 { 476 return dentry->d_inode == NULL; 477 } 478 479 /** 480 * d_really_is_positive - Determine if a dentry is really positive (ignoring fallthroughs) 481 * @dentry: The dentry in question 482 * 483 * Returns true if the dentry represents a name that maps to an inode 484 * (ie. ->d_inode is not NULL). The dentry might still represent a whiteout if 485 * that is represented on medium as a 0,0 chardev. 486 * 487 * Note! (1) This should be used *only* by a filesystem to examine its own 488 * dentries. It should not be used to look at some other filesystem's 489 * dentries. (2) It should also be used in combination with d_inode() to get 490 * the inode. 491 */ 492 static inline bool d_really_is_positive(const struct dentry *dentry) 493 { 494 return dentry->d_inode != NULL; 495 } 496 497 static inline int simple_positive(const struct dentry *dentry) 498 { 499 return d_really_is_positive(dentry) && !d_unhashed(dentry); 500 } 501 502 extern void d_set_fallthru(struct dentry *dentry); 503 504 static inline bool d_is_fallthru(const struct dentry *dentry) 505 { 506 return dentry->d_flags & DCACHE_FALLTHRU; 507 } 508 509 510 extern int sysctl_vfs_cache_pressure; 511 512 static inline unsigned long vfs_pressure_ratio(unsigned long val) 513 { 514 return mult_frac(val, sysctl_vfs_cache_pressure, 100); 515 } 516 517 /** 518 * d_inode - Get the actual inode of this dentry 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(const struct dentry *dentry) 525 { 526 return dentry->d_inode; 527 } 528 529 /** 530 * d_inode_rcu - Get the actual inode of this dentry with READ_ONCE() 531 * @dentry: The dentry to query 532 * 533 * This is the helper normal filesystems should use to get at their own inodes 534 * in their own dentries and ignore the layering superimposed upon them. 535 */ 536 static inline struct inode *d_inode_rcu(const struct dentry *dentry) 537 { 538 return READ_ONCE(dentry->d_inode); 539 } 540 541 /** 542 * d_backing_inode - Get upper or lower inode we should be using 543 * @upper: The upper layer 544 * 545 * This is the helper that should be used to get at the inode that will be used 546 * if this dentry were to be opened as a file. The inode may be on the upper 547 * dentry or it may be on a lower dentry pinned by the upper. 548 * 549 * Normal filesystems should not use this to access their own inodes. 550 */ 551 static inline struct inode *d_backing_inode(const struct dentry *upper) 552 { 553 struct inode *inode = upper->d_inode; 554 555 return inode; 556 } 557 558 /** 559 * d_backing_dentry - Get upper or lower dentry we should be using 560 * @upper: The upper layer 561 * 562 * This is the helper that should be used to get the dentry of the inode that 563 * will be used if this dentry were opened as a file. It may be the upper 564 * dentry or it may be a lower dentry pinned by the upper. 565 * 566 * Normal filesystems should not use this to access their own dentries. 567 */ 568 static inline struct dentry *d_backing_dentry(struct dentry *upper) 569 { 570 return upper; 571 } 572 573 /** 574 * d_real - Return the real dentry 575 * @dentry: the dentry to query 576 * @inode: inode to select the dentry from multiple layers (can be NULL) 577 * 578 * If dentry is on a union/overlay, then return the underlying, real dentry. 579 * Otherwise return the dentry itself. 580 * 581 * See also: Documentation/filesystems/vfs.rst 582 */ 583 static inline struct dentry *d_real(struct dentry *dentry, 584 const struct inode *inode) 585 { 586 if (unlikely(dentry->d_flags & DCACHE_OP_REAL)) 587 return dentry->d_op->d_real(dentry, inode); 588 else 589 return dentry; 590 } 591 592 /** 593 * d_real_inode - Return the real inode 594 * @dentry: The dentry to query 595 * 596 * If dentry is on a union/overlay, then return the underlying, real inode. 597 * Otherwise return d_inode(). 598 */ 599 static inline struct inode *d_real_inode(const struct dentry *dentry) 600 { 601 /* This usage of d_real() results in const dentry */ 602 return d_backing_inode(d_real((struct dentry *) dentry, NULL)); 603 } 604 605 struct name_snapshot { 606 struct qstr name; 607 unsigned char inline_name[DNAME_INLINE_LEN]; 608 }; 609 void take_dentry_name_snapshot(struct name_snapshot *, struct dentry *); 610 void release_dentry_name_snapshot(struct name_snapshot *); 611 612 #endif /* __LINUX_DCACHE_H */ 613