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 /* 65 * Try to keep struct dentry aligned on 64 byte cachelines (this will 66 * give reasonable cacheline footprint with larger lines without the 67 * large memory footprint increase). 68 */ 69 #ifdef CONFIG_64BIT 70 # define DNAME_INLINE_LEN 32 /* 192 bytes */ 71 #else 72 # ifdef CONFIG_SMP 73 # define DNAME_INLINE_LEN 36 /* 128 bytes */ 74 # else 75 # define DNAME_INLINE_LEN 40 /* 128 bytes */ 76 # endif 77 #endif 78 79 #define d_lock d_lockref.lock 80 81 struct dentry { 82 /* RCU lookup touched fields */ 83 unsigned int d_flags; /* protected by d_lock */ 84 seqcount_spinlock_t d_seq; /* per dentry seqlock */ 85 struct hlist_bl_node d_hash; /* lookup hash list */ 86 struct dentry *d_parent; /* parent directory */ 87 struct qstr d_name; 88 struct inode *d_inode; /* Where the name belongs to - NULL is 89 * negative */ 90 unsigned char d_iname[DNAME_INLINE_LEN]; /* small names */ 91 92 /* Ref lookup also touches following */ 93 struct lockref d_lockref; /* per-dentry lock and refcount */ 94 const struct dentry_operations *d_op; 95 struct super_block *d_sb; /* The root of the dentry tree */ 96 unsigned long d_time; /* used by d_revalidate */ 97 void *d_fsdata; /* fs-specific data */ 98 99 union { 100 struct list_head d_lru; /* LRU list */ 101 wait_queue_head_t *d_wait; /* in-lookup ones only */ 102 }; 103 struct list_head d_child; /* child of parent list */ 104 struct list_head d_subdirs; /* our children */ 105 /* 106 * d_alias and d_rcu can share memory 107 */ 108 union { 109 struct hlist_node d_alias; /* inode alias list */ 110 struct hlist_bl_node d_in_lookup_hash; /* only for in-lookup ones */ 111 struct rcu_head d_rcu; 112 } d_u; 113 } __randomize_layout; 114 115 /* 116 * dentry->d_lock spinlock nesting subclasses: 117 * 118 * 0: normal 119 * 1: nested 120 */ 121 enum dentry_d_lock_class 122 { 123 DENTRY_D_LOCK_NORMAL, /* implicitly used by plain spin_lock() APIs. */ 124 DENTRY_D_LOCK_NESTED 125 }; 126 127 struct dentry_operations { 128 int (*d_revalidate)(struct dentry *, unsigned int); 129 int (*d_weak_revalidate)(struct dentry *, unsigned int); 130 int (*d_hash)(const struct dentry *, struct qstr *); 131 int (*d_compare)(const struct dentry *, 132 unsigned int, const char *, const struct qstr *); 133 int (*d_delete)(const struct dentry *); 134 int (*d_init)(struct dentry *); 135 void (*d_release)(struct dentry *); 136 void (*d_prune)(struct dentry *); 137 void (*d_iput)(struct dentry *, struct inode *); 138 char *(*d_dname)(struct dentry *, char *, int); 139 struct vfsmount *(*d_automount)(struct path *); 140 int (*d_manage)(const struct path *, bool); 141 struct dentry *(*d_real)(struct dentry *, const struct inode *); 142 } ____cacheline_aligned; 143 144 /* 145 * Locking rules for dentry_operations callbacks are to be found in 146 * Documentation/filesystems/locking.rst. Keep it updated! 147 * 148 * FUrther descriptions are found in Documentation/filesystems/vfs.rst. 149 * Keep it updated too! 150 */ 151 152 /* d_flags entries */ 153 #define DCACHE_OP_HASH 0x00000001 154 #define DCACHE_OP_COMPARE 0x00000002 155 #define DCACHE_OP_REVALIDATE 0x00000004 156 #define DCACHE_OP_DELETE 0x00000008 157 #define DCACHE_OP_PRUNE 0x00000010 158 159 #define DCACHE_DISCONNECTED 0x00000020 160 /* This dentry is possibly not currently connected to the dcache tree, in 161 * which case its parent will either be itself, or will have this flag as 162 * well. nfsd will not use a dentry with this bit set, but will first 163 * endeavour to clear the bit either by discovering that it is connected, 164 * or by performing lookup operations. Any filesystem which supports 165 * nfsd_operations MUST have a lookup function which, if it finds a 166 * directory inode with a DCACHE_DISCONNECTED dentry, will d_move that 167 * dentry into place and return that dentry rather than the passed one, 168 * typically using d_splice_alias. */ 169 170 #define DCACHE_REFERENCED 0x00000040 /* Recently used, don't discard. */ 171 172 #define DCACHE_DONTCACHE 0x00000080 /* Purge from memory on final dput() */ 173 174 #define DCACHE_CANT_MOUNT 0x00000100 175 #define DCACHE_GENOCIDE 0x00000200 176 #define DCACHE_SHRINK_LIST 0x00000400 177 178 #define DCACHE_OP_WEAK_REVALIDATE 0x00000800 179 180 #define DCACHE_NFSFS_RENAMED 0x00001000 181 /* this dentry has been "silly renamed" and has to be deleted on the last 182 * dput() */ 183 #define DCACHE_COOKIE 0x00002000 /* For use by dcookie subsystem */ 184 #define DCACHE_FSNOTIFY_PARENT_WATCHED 0x00004000 185 /* Parent inode is watched by some fsnotify listener */ 186 187 #define DCACHE_DENTRY_KILLED 0x00008000 188 189 #define DCACHE_MOUNTED 0x00010000 /* is a mountpoint */ 190 #define DCACHE_NEED_AUTOMOUNT 0x00020000 /* handle automount on this dir */ 191 #define DCACHE_MANAGE_TRANSIT 0x00040000 /* manage transit from this dirent */ 192 #define DCACHE_MANAGED_DENTRY \ 193 (DCACHE_MOUNTED|DCACHE_NEED_AUTOMOUNT|DCACHE_MANAGE_TRANSIT) 194 195 #define DCACHE_LRU_LIST 0x00080000 196 197 #define DCACHE_ENTRY_TYPE 0x00700000 198 #define DCACHE_MISS_TYPE 0x00000000 /* Negative dentry (maybe fallthru to nowhere) */ 199 #define DCACHE_WHITEOUT_TYPE 0x00100000 /* Whiteout dentry (stop pathwalk) */ 200 #define DCACHE_DIRECTORY_TYPE 0x00200000 /* Normal directory */ 201 #define DCACHE_AUTODIR_TYPE 0x00300000 /* Lookupless directory (presumed automount) */ 202 #define DCACHE_REGULAR_TYPE 0x00400000 /* Regular file type (or fallthru to such) */ 203 #define DCACHE_SPECIAL_TYPE 0x00500000 /* Other file type (or fallthru to such) */ 204 #define DCACHE_SYMLINK_TYPE 0x00600000 /* Symlink (or fallthru to such) */ 205 206 #define DCACHE_MAY_FREE 0x00800000 207 #define DCACHE_FALLTHRU 0x01000000 /* Fall through to lower layer */ 208 #define DCACHE_NOKEY_NAME 0x02000000 /* Encrypted name encoded without key */ 209 #define DCACHE_OP_REAL 0x04000000 210 211 #define DCACHE_PAR_LOOKUP 0x10000000 /* being looked up (with parent locked shared) */ 212 #define DCACHE_DENTRY_CURSOR 0x20000000 213 #define DCACHE_NORCU 0x40000000 /* No RCU delay for freeing */ 214 215 extern seqlock_t rename_lock; 216 217 /* 218 * These are the low-level FS interfaces to the dcache.. 219 */ 220 extern void d_instantiate(struct dentry *, struct inode *); 221 extern void d_instantiate_new(struct dentry *, struct inode *); 222 extern struct dentry * d_instantiate_unique(struct dentry *, struct inode *); 223 extern struct dentry * d_instantiate_anon(struct dentry *, struct inode *); 224 extern void __d_drop(struct dentry *dentry); 225 extern void d_drop(struct dentry *dentry); 226 extern void d_delete(struct dentry *); 227 extern void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op); 228 229 /* allocate/de-allocate */ 230 extern struct dentry * d_alloc(struct dentry *, const struct qstr *); 231 extern struct dentry * d_alloc_anon(struct super_block *); 232 extern struct dentry * d_alloc_parallel(struct dentry *, const struct qstr *, 233 wait_queue_head_t *); 234 extern struct dentry * d_splice_alias(struct inode *, struct dentry *); 235 extern struct dentry * d_add_ci(struct dentry *, struct inode *, struct qstr *); 236 extern bool d_same_name(const struct dentry *dentry, const struct dentry *parent, 237 const struct qstr *name); 238 extern struct dentry * d_exact_alias(struct dentry *, struct inode *); 239 extern struct dentry *d_find_any_alias(struct inode *inode); 240 extern struct dentry * d_obtain_alias(struct inode *); 241 extern struct dentry * d_obtain_root(struct inode *); 242 extern void shrink_dcache_sb(struct super_block *); 243 extern void shrink_dcache_parent(struct dentry *); 244 extern void shrink_dcache_for_umount(struct super_block *); 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 /* <clickety>-<click> the ramfs-type tree */ 251 extern void d_genocide(struct dentry *); 252 253 extern void d_tmpfile(struct dentry *, struct inode *); 254 255 extern struct dentry *d_find_alias(struct inode *); 256 extern void d_prune_aliases(struct inode *); 257 258 extern struct dentry *d_find_alias_rcu(struct inode *); 259 260 /* test whether we have any submounts in a subdir tree */ 261 extern int path_has_submounts(const struct path *); 262 263 /* 264 * This adds the entry to the hash queues. 265 */ 266 extern void d_rehash(struct dentry *); 267 268 extern void d_add(struct dentry *, struct inode *); 269 270 /* used for rename() and baskets */ 271 extern void d_move(struct dentry *, struct dentry *); 272 extern void d_exchange(struct dentry *, struct dentry *); 273 extern struct dentry *d_ancestor(struct dentry *, struct dentry *); 274 275 /* appendix may either be NULL or be used for transname suffixes */ 276 extern struct dentry *d_lookup(const struct dentry *, const struct qstr *); 277 extern struct dentry *d_hash_and_lookup(struct dentry *, struct qstr *); 278 extern struct dentry *__d_lookup(const struct dentry *, const struct qstr *); 279 extern struct dentry *__d_lookup_rcu(const struct dentry *parent, 280 const struct qstr *name, unsigned *seq); 281 282 static inline unsigned d_count(const struct dentry *dentry) 283 { 284 return dentry->d_lockref.count; 285 } 286 287 /* 288 * helper function for dentry_operations.d_dname() members 289 */ 290 extern __printf(4, 5) 291 char *dynamic_dname(struct dentry *, char *, int, const char *, ...); 292 293 extern char *__d_path(const struct path *, const struct path *, char *, int); 294 extern char *d_absolute_path(const struct path *, char *, int); 295 extern char *d_path(const struct path *, char *, int); 296 extern char *dentry_path_raw(const struct dentry *, char *, int); 297 extern char *dentry_path(const struct dentry *, char *, int); 298 299 /* Allocation counts.. */ 300 301 /** 302 * dget, dget_dlock - get a reference to a dentry 303 * @dentry: dentry to get a reference to 304 * 305 * Given a dentry or %NULL pointer increment the reference count 306 * if appropriate and return the dentry. A dentry will not be 307 * destroyed when it has references. 308 */ 309 static inline struct dentry *dget_dlock(struct dentry *dentry) 310 { 311 if (dentry) 312 dentry->d_lockref.count++; 313 return dentry; 314 } 315 316 static inline struct dentry *dget(struct dentry *dentry) 317 { 318 if (dentry) 319 lockref_get(&dentry->d_lockref); 320 return dentry; 321 } 322 323 extern struct dentry *dget_parent(struct dentry *dentry); 324 325 /** 326 * d_unhashed - is dentry hashed 327 * @dentry: entry to check 328 * 329 * Returns true if the dentry passed is not currently hashed. 330 */ 331 332 static inline int d_unhashed(const struct dentry *dentry) 333 { 334 return hlist_bl_unhashed(&dentry->d_hash); 335 } 336 337 static inline int d_unlinked(const struct dentry *dentry) 338 { 339 return d_unhashed(dentry) && !IS_ROOT(dentry); 340 } 341 342 static inline int cant_mount(const struct dentry *dentry) 343 { 344 return (dentry->d_flags & DCACHE_CANT_MOUNT); 345 } 346 347 static inline void dont_mount(struct dentry *dentry) 348 { 349 spin_lock(&dentry->d_lock); 350 dentry->d_flags |= DCACHE_CANT_MOUNT; 351 spin_unlock(&dentry->d_lock); 352 } 353 354 extern void __d_lookup_unhash_wake(struct dentry *dentry); 355 356 static inline int d_in_lookup(const struct dentry *dentry) 357 { 358 return dentry->d_flags & DCACHE_PAR_LOOKUP; 359 } 360 361 static inline void d_lookup_done(struct dentry *dentry) 362 { 363 if (unlikely(d_in_lookup(dentry))) 364 __d_lookup_unhash_wake(dentry); 365 } 366 367 extern void dput(struct dentry *); 368 369 static inline bool d_managed(const struct dentry *dentry) 370 { 371 return dentry->d_flags & DCACHE_MANAGED_DENTRY; 372 } 373 374 static inline bool d_mountpoint(const struct dentry *dentry) 375 { 376 return dentry->d_flags & DCACHE_MOUNTED; 377 } 378 379 /* 380 * Directory cache entry type accessor functions. 381 */ 382 static inline unsigned __d_entry_type(const struct dentry *dentry) 383 { 384 return dentry->d_flags & DCACHE_ENTRY_TYPE; 385 } 386 387 static inline bool d_is_miss(const struct dentry *dentry) 388 { 389 return __d_entry_type(dentry) == DCACHE_MISS_TYPE; 390 } 391 392 static inline bool d_is_whiteout(const struct dentry *dentry) 393 { 394 return __d_entry_type(dentry) == DCACHE_WHITEOUT_TYPE; 395 } 396 397 static inline bool d_can_lookup(const struct dentry *dentry) 398 { 399 return __d_entry_type(dentry) == DCACHE_DIRECTORY_TYPE; 400 } 401 402 static inline bool d_is_autodir(const struct dentry *dentry) 403 { 404 return __d_entry_type(dentry) == DCACHE_AUTODIR_TYPE; 405 } 406 407 static inline bool d_is_dir(const struct dentry *dentry) 408 { 409 return d_can_lookup(dentry) || d_is_autodir(dentry); 410 } 411 412 static inline bool d_is_symlink(const struct dentry *dentry) 413 { 414 return __d_entry_type(dentry) == DCACHE_SYMLINK_TYPE; 415 } 416 417 static inline bool d_is_reg(const struct dentry *dentry) 418 { 419 return __d_entry_type(dentry) == DCACHE_REGULAR_TYPE; 420 } 421 422 static inline bool d_is_special(const struct dentry *dentry) 423 { 424 return __d_entry_type(dentry) == DCACHE_SPECIAL_TYPE; 425 } 426 427 static inline bool d_is_file(const struct dentry *dentry) 428 { 429 return d_is_reg(dentry) || d_is_special(dentry); 430 } 431 432 static inline bool d_is_negative(const struct dentry *dentry) 433 { 434 // TODO: check d_is_whiteout(dentry) also. 435 return d_is_miss(dentry); 436 } 437 438 static inline bool d_flags_negative(unsigned flags) 439 { 440 return (flags & DCACHE_ENTRY_TYPE) == DCACHE_MISS_TYPE; 441 } 442 443 static inline bool d_is_positive(const struct dentry *dentry) 444 { 445 return !d_is_negative(dentry); 446 } 447 448 /** 449 * d_really_is_negative - Determine if a dentry is really negative (ignoring fallthroughs) 450 * @dentry: The dentry in question 451 * 452 * Returns true if the dentry represents either an absent name or a name that 453 * doesn't map to an inode (ie. ->d_inode is NULL). The dentry could represent 454 * a true miss, a whiteout that isn't represented by a 0,0 chardev or a 455 * fallthrough marker in an opaque directory. 456 * 457 * Note! (1) This should be used *only* by a filesystem to examine its own 458 * dentries. It should not be used to look at some other filesystem's 459 * dentries. (2) It should also be used in combination with d_inode() to get 460 * the inode. (3) The dentry may have something attached to ->d_lower and the 461 * type field of the flags may be set to something other than miss or whiteout. 462 */ 463 static inline bool d_really_is_negative(const struct dentry *dentry) 464 { 465 return dentry->d_inode == NULL; 466 } 467 468 /** 469 * d_really_is_positive - Determine if a dentry is really positive (ignoring fallthroughs) 470 * @dentry: The dentry in question 471 * 472 * Returns true if the dentry represents a name that maps to an inode 473 * (ie. ->d_inode is not NULL). The dentry might still represent a whiteout if 474 * that is represented on medium as a 0,0 chardev. 475 * 476 * Note! (1) This should be used *only* by a filesystem to examine its own 477 * dentries. It should not be used to look at some other filesystem's 478 * dentries. (2) It should also be used in combination with d_inode() to get 479 * the inode. 480 */ 481 static inline bool d_really_is_positive(const struct dentry *dentry) 482 { 483 return dentry->d_inode != NULL; 484 } 485 486 static inline int simple_positive(const struct dentry *dentry) 487 { 488 return d_really_is_positive(dentry) && !d_unhashed(dentry); 489 } 490 491 extern void d_set_fallthru(struct dentry *dentry); 492 493 static inline bool d_is_fallthru(const struct dentry *dentry) 494 { 495 return dentry->d_flags & DCACHE_FALLTHRU; 496 } 497 498 499 extern int sysctl_vfs_cache_pressure; 500 501 static inline unsigned long vfs_pressure_ratio(unsigned long val) 502 { 503 return mult_frac(val, sysctl_vfs_cache_pressure, 100); 504 } 505 506 /** 507 * d_inode - Get the actual inode of this dentry 508 * @dentry: The dentry to query 509 * 510 * This is the helper normal filesystems should use to get at their own inodes 511 * in their own dentries and ignore the layering superimposed upon them. 512 */ 513 static inline struct inode *d_inode(const struct dentry *dentry) 514 { 515 return dentry->d_inode; 516 } 517 518 /** 519 * d_inode_rcu - Get the actual inode of this dentry with READ_ONCE() 520 * @dentry: The dentry to query 521 * 522 * This is the helper normal filesystems should use to get at their own inodes 523 * in their own dentries and ignore the layering superimposed upon them. 524 */ 525 static inline struct inode *d_inode_rcu(const struct dentry *dentry) 526 { 527 return READ_ONCE(dentry->d_inode); 528 } 529 530 /** 531 * d_backing_inode - Get upper or lower inode we should be using 532 * @upper: The upper layer 533 * 534 * This is the helper that should be used to get at the inode that will be used 535 * if this dentry were to be opened as a file. The inode may be on the upper 536 * dentry or it may be on a lower dentry pinned by the upper. 537 * 538 * Normal filesystems should not use this to access their own inodes. 539 */ 540 static inline struct inode *d_backing_inode(const struct dentry *upper) 541 { 542 struct inode *inode = upper->d_inode; 543 544 return inode; 545 } 546 547 /** 548 * d_backing_dentry - Get upper or lower dentry we should be using 549 * @upper: The upper layer 550 * 551 * This is the helper that should be used to get the dentry of the inode that 552 * will be used if this dentry were opened as a file. It may be the upper 553 * dentry or it may be a lower dentry pinned by the upper. 554 * 555 * Normal filesystems should not use this to access their own dentries. 556 */ 557 static inline struct dentry *d_backing_dentry(struct dentry *upper) 558 { 559 return upper; 560 } 561 562 /** 563 * d_real - Return the real dentry 564 * @dentry: the dentry to query 565 * @inode: inode to select the dentry from multiple layers (can be NULL) 566 * 567 * If dentry is on a union/overlay, then return the underlying, real dentry. 568 * Otherwise return the dentry itself. 569 * 570 * See also: Documentation/filesystems/vfs.rst 571 */ 572 static inline struct dentry *d_real(struct dentry *dentry, 573 const struct inode *inode) 574 { 575 if (unlikely(dentry->d_flags & DCACHE_OP_REAL)) 576 return dentry->d_op->d_real(dentry, inode); 577 else 578 return dentry; 579 } 580 581 /** 582 * d_real_inode - Return the real inode 583 * @dentry: The dentry to query 584 * 585 * If dentry is on a union/overlay, then return the underlying, real inode. 586 * Otherwise return d_inode(). 587 */ 588 static inline struct inode *d_real_inode(const struct dentry *dentry) 589 { 590 /* This usage of d_real() results in const dentry */ 591 return d_backing_inode(d_real((struct dentry *) dentry, NULL)); 592 } 593 594 struct name_snapshot { 595 struct qstr name; 596 unsigned char inline_name[DNAME_INLINE_LEN]; 597 }; 598 void take_dentry_name_snapshot(struct name_snapshot *, struct dentry *); 599 void release_dentry_name_snapshot(struct name_snapshot *); 600 601 #endif /* __LINUX_DCACHE_H */ 602