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 61 extern const struct qstr empty_name; 62 extern const struct qstr slash_name; 63 extern 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 32 /* 192 bytes */ 72 #else 73 # ifdef CONFIG_SMP 74 # define DNAME_INLINE_LEN 36 /* 128 bytes */ 75 # else 76 # define DNAME_INLINE_LEN 40 /* 128 bytes */ 77 # endif 78 #endif 79 80 #define d_lock d_lockref.lock 81 82 struct 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 list_head d_child; /* child of parent list */ 105 struct list_head d_subdirs; /* 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 } __randomize_layout; 115 116 /* 117 * dentry->d_lock spinlock nesting subclasses: 118 * 119 * 0: normal 120 * 1: nested 121 */ 122 enum dentry_d_lock_class 123 { 124 DENTRY_D_LOCK_NORMAL, /* implicitly used by plain spin_lock() APIs. */ 125 DENTRY_D_LOCK_NESTED 126 }; 127 128 struct dentry_operations { 129 int (*d_revalidate)(struct dentry *, unsigned int); 130 int (*d_weak_revalidate)(struct dentry *, unsigned int); 131 int (*d_hash)(const struct dentry *, struct qstr *); 132 int (*d_compare)(const struct dentry *, 133 unsigned int, const char *, const struct qstr *); 134 int (*d_delete)(const struct dentry *); 135 int (*d_init)(struct dentry *); 136 void (*d_release)(struct dentry *); 137 void (*d_prune)(struct dentry *); 138 void (*d_iput)(struct dentry *, struct inode *); 139 char *(*d_dname)(struct dentry *, char *, int); 140 struct vfsmount *(*d_automount)(struct path *); 141 int (*d_manage)(const struct path *, bool); 142 struct dentry *(*d_real)(struct dentry *, const struct inode *); 143 } ____cacheline_aligned; 144 145 /* 146 * Locking rules for dentry_operations callbacks are to be found in 147 * Documentation/filesystems/locking.rst. Keep it updated! 148 * 149 * FUrther descriptions are found in Documentation/filesystems/vfs.rst. 150 * Keep it updated too! 151 */ 152 153 /* d_flags entries */ 154 #define DCACHE_OP_HASH 0x00000001 155 #define DCACHE_OP_COMPARE 0x00000002 156 #define DCACHE_OP_REVALIDATE 0x00000004 157 #define DCACHE_OP_DELETE 0x00000008 158 #define DCACHE_OP_PRUNE 0x00000010 159 160 #define DCACHE_DISCONNECTED 0x00000020 161 /* This dentry is possibly not currently connected to the dcache tree, in 162 * which case its parent will either be itself, or will have this flag as 163 * well. nfsd will not use a dentry with this bit set, but will first 164 * endeavour to clear the bit either by discovering that it is connected, 165 * or by performing lookup operations. Any filesystem which supports 166 * nfsd_operations MUST have a lookup function which, if it finds a 167 * directory inode with a DCACHE_DISCONNECTED dentry, will d_move that 168 * dentry into place and return that dentry rather than the passed one, 169 * typically using d_splice_alias. */ 170 171 #define DCACHE_REFERENCED 0x00000040 /* Recently used, don't discard. */ 172 173 #define DCACHE_DONTCACHE 0x00000080 /* Purge from memory on final dput() */ 174 175 #define DCACHE_CANT_MOUNT 0x00000100 176 #define DCACHE_GENOCIDE 0x00000200 177 #define DCACHE_SHRINK_LIST 0x00000400 178 179 #define DCACHE_OP_WEAK_REVALIDATE 0x00000800 180 181 #define DCACHE_NFSFS_RENAMED 0x00001000 182 /* this dentry has been "silly renamed" and has to be deleted on the last 183 * dput() */ 184 #define DCACHE_COOKIE 0x00002000 /* For use by dcookie subsystem */ 185 #define DCACHE_FSNOTIFY_PARENT_WATCHED 0x00004000 186 /* Parent inode is watched by some fsnotify listener */ 187 188 #define DCACHE_DENTRY_KILLED 0x00008000 189 190 #define DCACHE_MOUNTED 0x00010000 /* is a mountpoint */ 191 #define DCACHE_NEED_AUTOMOUNT 0x00020000 /* handle automount on this dir */ 192 #define DCACHE_MANAGE_TRANSIT 0x00040000 /* manage transit from this dirent */ 193 #define DCACHE_MANAGED_DENTRY \ 194 (DCACHE_MOUNTED|DCACHE_NEED_AUTOMOUNT|DCACHE_MANAGE_TRANSIT) 195 196 #define DCACHE_LRU_LIST 0x00080000 197 198 #define DCACHE_ENTRY_TYPE 0x00700000 199 #define DCACHE_MISS_TYPE 0x00000000 /* Negative dentry (maybe fallthru to nowhere) */ 200 #define DCACHE_WHITEOUT_TYPE 0x00100000 /* Whiteout dentry (stop pathwalk) */ 201 #define DCACHE_DIRECTORY_TYPE 0x00200000 /* Normal directory */ 202 #define DCACHE_AUTODIR_TYPE 0x00300000 /* Lookupless directory (presumed automount) */ 203 #define DCACHE_REGULAR_TYPE 0x00400000 /* Regular file type (or fallthru to such) */ 204 #define DCACHE_SPECIAL_TYPE 0x00500000 /* Other file type (or fallthru to such) */ 205 #define DCACHE_SYMLINK_TYPE 0x00600000 /* Symlink (or fallthru to such) */ 206 207 #define DCACHE_MAY_FREE 0x00800000 208 #define DCACHE_FALLTHRU 0x01000000 /* Fall through to lower layer */ 209 #define DCACHE_NOKEY_NAME 0x02000000 /* Encrypted name encoded without key */ 210 #define DCACHE_OP_REAL 0x04000000 211 212 #define DCACHE_PAR_LOOKUP 0x10000000 /* being looked up (with parent locked shared) */ 213 #define DCACHE_DENTRY_CURSOR 0x20000000 214 #define DCACHE_NORCU 0x40000000 /* No RCU delay for freeing */ 215 216 extern seqlock_t rename_lock; 217 218 /* 219 * These are the low-level FS interfaces to the dcache.. 220 */ 221 extern void d_instantiate(struct dentry *, struct inode *); 222 extern void d_instantiate_new(struct dentry *, struct inode *); 223 extern struct dentry * d_instantiate_unique(struct dentry *, struct inode *); 224 extern struct dentry * d_instantiate_anon(struct dentry *, struct inode *); 225 extern void __d_drop(struct dentry *dentry); 226 extern void d_drop(struct dentry *dentry); 227 extern void d_delete(struct dentry *); 228 extern void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op); 229 230 /* allocate/de-allocate */ 231 extern struct dentry * d_alloc(struct dentry *, const struct qstr *); 232 extern struct dentry * d_alloc_anon(struct super_block *); 233 extern struct dentry * d_alloc_parallel(struct dentry *, const struct qstr *, 234 wait_queue_head_t *); 235 extern struct dentry * d_splice_alias(struct inode *, struct dentry *); 236 extern struct dentry * d_add_ci(struct dentry *, struct inode *, struct qstr *); 237 extern bool d_same_name(const struct dentry *dentry, const struct dentry *parent, 238 const struct qstr *name); 239 extern struct dentry * d_exact_alias(struct dentry *, struct inode *); 240 extern struct dentry *d_find_any_alias(struct inode *inode); 241 extern struct dentry * d_obtain_alias(struct inode *); 242 extern struct dentry * d_obtain_root(struct inode *); 243 extern void shrink_dcache_sb(struct super_block *); 244 extern void shrink_dcache_parent(struct dentry *); 245 extern void shrink_dcache_for_umount(struct super_block *); 246 extern void d_invalidate(struct dentry *); 247 248 /* only used at mount-time */ 249 extern struct dentry * d_make_root(struct inode *); 250 251 /* <clickety>-<click> the ramfs-type tree */ 252 extern void d_genocide(struct dentry *); 253 254 extern void d_tmpfile(struct file *, struct inode *); 255 256 extern struct dentry *d_find_alias(struct inode *); 257 extern void d_prune_aliases(struct inode *); 258 259 extern struct dentry *d_find_alias_rcu(struct inode *); 260 261 /* test whether we have any submounts in a subdir tree */ 262 extern int path_has_submounts(const struct path *); 263 264 /* 265 * This adds the entry to the hash queues. 266 */ 267 extern void d_rehash(struct dentry *); 268 269 extern void d_add(struct dentry *, struct inode *); 270 271 /* used for rename() and baskets */ 272 extern void d_move(struct dentry *, struct dentry *); 273 extern void d_exchange(struct dentry *, struct dentry *); 274 extern struct dentry *d_ancestor(struct dentry *, struct dentry *); 275 276 /* appendix may either be NULL or be used for transname suffixes */ 277 extern struct dentry *d_lookup(const struct dentry *, const struct qstr *); 278 extern struct dentry *d_hash_and_lookup(struct dentry *, struct qstr *); 279 extern struct dentry *__d_lookup(const struct dentry *, const struct qstr *); 280 extern struct dentry *__d_lookup_rcu(const struct dentry *parent, 281 const struct qstr *name, unsigned *seq); 282 283 static inline unsigned d_count(const struct dentry *dentry) 284 { 285 return dentry->d_lockref.count; 286 } 287 288 /* 289 * helper function for dentry_operations.d_dname() members 290 */ 291 extern __printf(3, 4) 292 char *dynamic_dname(char *, int, const char *, ...); 293 294 extern char *__d_path(const struct path *, const struct path *, char *, int); 295 extern char *d_absolute_path(const struct path *, char *, int); 296 extern char *d_path(const struct path *, char *, int); 297 extern char *dentry_path_raw(const struct dentry *, char *, int); 298 extern char *dentry_path(const struct dentry *, char *, int); 299 300 /* Allocation counts.. */ 301 302 /** 303 * dget, dget_dlock - get a reference to a dentry 304 * @dentry: dentry to get a reference to 305 * 306 * Given a dentry or %NULL pointer increment the reference count 307 * if appropriate and return the dentry. A dentry will not be 308 * destroyed when it has references. 309 */ 310 static inline struct dentry *dget_dlock(struct dentry *dentry) 311 { 312 if (dentry) 313 dentry->d_lockref.count++; 314 return dentry; 315 } 316 317 static inline struct dentry *dget(struct dentry *dentry) 318 { 319 if (dentry) 320 lockref_get(&dentry->d_lockref); 321 return dentry; 322 } 323 324 extern struct dentry *dget_parent(struct dentry *dentry); 325 326 /** 327 * d_unhashed - is dentry hashed 328 * @dentry: entry to check 329 * 330 * Returns true if the dentry passed is not currently hashed. 331 */ 332 333 static inline int d_unhashed(const struct dentry *dentry) 334 { 335 return hlist_bl_unhashed(&dentry->d_hash); 336 } 337 338 static inline int d_unlinked(const struct dentry *dentry) 339 { 340 return d_unhashed(dentry) && !IS_ROOT(dentry); 341 } 342 343 static inline int cant_mount(const struct dentry *dentry) 344 { 345 return (dentry->d_flags & DCACHE_CANT_MOUNT); 346 } 347 348 static inline void dont_mount(struct dentry *dentry) 349 { 350 spin_lock(&dentry->d_lock); 351 dentry->d_flags |= DCACHE_CANT_MOUNT; 352 spin_unlock(&dentry->d_lock); 353 } 354 355 extern void __d_lookup_unhash_wake(struct dentry *dentry); 356 357 static inline int d_in_lookup(const struct dentry *dentry) 358 { 359 return dentry->d_flags & DCACHE_PAR_LOOKUP; 360 } 361 362 static inline void d_lookup_done(struct dentry *dentry) 363 { 364 if (unlikely(d_in_lookup(dentry))) 365 __d_lookup_unhash_wake(dentry); 366 } 367 368 extern void dput(struct dentry *); 369 370 static inline bool d_managed(const struct dentry *dentry) 371 { 372 return dentry->d_flags & DCACHE_MANAGED_DENTRY; 373 } 374 375 static inline bool d_mountpoint(const struct dentry *dentry) 376 { 377 return dentry->d_flags & DCACHE_MOUNTED; 378 } 379 380 /* 381 * Directory cache entry type accessor functions. 382 */ 383 static inline unsigned __d_entry_type(const struct dentry *dentry) 384 { 385 return dentry->d_flags & DCACHE_ENTRY_TYPE; 386 } 387 388 static inline bool d_is_miss(const struct dentry *dentry) 389 { 390 return __d_entry_type(dentry) == DCACHE_MISS_TYPE; 391 } 392 393 static inline bool d_is_whiteout(const struct dentry *dentry) 394 { 395 return __d_entry_type(dentry) == DCACHE_WHITEOUT_TYPE; 396 } 397 398 static inline bool d_can_lookup(const struct dentry *dentry) 399 { 400 return __d_entry_type(dentry) == DCACHE_DIRECTORY_TYPE; 401 } 402 403 static inline bool d_is_autodir(const struct dentry *dentry) 404 { 405 return __d_entry_type(dentry) == DCACHE_AUTODIR_TYPE; 406 } 407 408 static inline bool d_is_dir(const struct dentry *dentry) 409 { 410 return d_can_lookup(dentry) || d_is_autodir(dentry); 411 } 412 413 static inline bool d_is_symlink(const struct dentry *dentry) 414 { 415 return __d_entry_type(dentry) == DCACHE_SYMLINK_TYPE; 416 } 417 418 static inline bool d_is_reg(const struct dentry *dentry) 419 { 420 return __d_entry_type(dentry) == DCACHE_REGULAR_TYPE; 421 } 422 423 static inline bool d_is_special(const struct dentry *dentry) 424 { 425 return __d_entry_type(dentry) == DCACHE_SPECIAL_TYPE; 426 } 427 428 static inline bool d_is_file(const struct dentry *dentry) 429 { 430 return d_is_reg(dentry) || d_is_special(dentry); 431 } 432 433 static inline bool d_is_negative(const struct dentry *dentry) 434 { 435 // TODO: check d_is_whiteout(dentry) also. 436 return d_is_miss(dentry); 437 } 438 439 static inline bool d_flags_negative(unsigned flags) 440 { 441 return (flags & DCACHE_ENTRY_TYPE) == DCACHE_MISS_TYPE; 442 } 443 444 static inline bool d_is_positive(const struct dentry *dentry) 445 { 446 return !d_is_negative(dentry); 447 } 448 449 /** 450 * d_really_is_negative - Determine if a dentry is really negative (ignoring fallthroughs) 451 * @dentry: The dentry in question 452 * 453 * Returns true if the dentry represents either an absent name or a name that 454 * doesn't map to an inode (ie. ->d_inode is NULL). The dentry could represent 455 * a true miss, a whiteout that isn't represented by a 0,0 chardev or a 456 * fallthrough marker in an opaque directory. 457 * 458 * Note! (1) This should be used *only* by a filesystem to examine its own 459 * dentries. It should not be used to look at some other filesystem's 460 * dentries. (2) It should also be used in combination with d_inode() to get 461 * the inode. (3) The dentry may have something attached to ->d_lower and the 462 * type field of the flags may be set to something other than miss or whiteout. 463 */ 464 static inline bool d_really_is_negative(const struct dentry *dentry) 465 { 466 return dentry->d_inode == NULL; 467 } 468 469 /** 470 * d_really_is_positive - Determine if a dentry is really positive (ignoring fallthroughs) 471 * @dentry: The dentry in question 472 * 473 * Returns true if the dentry represents a name that maps to an inode 474 * (ie. ->d_inode is not NULL). The dentry might still represent a whiteout if 475 * that is represented on medium as a 0,0 chardev. 476 * 477 * Note! (1) This should be used *only* by a filesystem to examine its own 478 * dentries. It should not be used to look at some other filesystem's 479 * dentries. (2) It should also be used in combination with d_inode() to get 480 * the inode. 481 */ 482 static inline bool d_really_is_positive(const struct dentry *dentry) 483 { 484 return dentry->d_inode != NULL; 485 } 486 487 static inline int simple_positive(const struct dentry *dentry) 488 { 489 return d_really_is_positive(dentry) && !d_unhashed(dentry); 490 } 491 492 extern void d_set_fallthru(struct dentry *dentry); 493 494 static inline bool d_is_fallthru(const struct dentry *dentry) 495 { 496 return dentry->d_flags & DCACHE_FALLTHRU; 497 } 498 499 500 extern int sysctl_vfs_cache_pressure; 501 502 static inline unsigned long vfs_pressure_ratio(unsigned long val) 503 { 504 return mult_frac(val, sysctl_vfs_cache_pressure, 100); 505 } 506 507 /** 508 * d_inode - Get the actual inode of this dentry 509 * @dentry: The dentry to query 510 * 511 * This is the helper normal filesystems should use to get at their own inodes 512 * in their own dentries and ignore the layering superimposed upon them. 513 */ 514 static inline struct inode *d_inode(const struct dentry *dentry) 515 { 516 return dentry->d_inode; 517 } 518 519 /** 520 * d_inode_rcu - Get the actual inode of this dentry with READ_ONCE() 521 * @dentry: The dentry to query 522 * 523 * This is the helper normal filesystems should use to get at their own inodes 524 * in their own dentries and ignore the layering superimposed upon them. 525 */ 526 static inline struct inode *d_inode_rcu(const struct dentry *dentry) 527 { 528 return READ_ONCE(dentry->d_inode); 529 } 530 531 /** 532 * d_backing_inode - Get upper or lower inode we should be using 533 * @upper: The upper layer 534 * 535 * This is the helper that should be used to get at the inode that will be used 536 * if this dentry were to be opened as a file. The inode may be on the upper 537 * dentry or it may be on a lower dentry pinned by the upper. 538 * 539 * Normal filesystems should not use this to access their own inodes. 540 */ 541 static inline struct inode *d_backing_inode(const struct dentry *upper) 542 { 543 struct inode *inode = upper->d_inode; 544 545 return inode; 546 } 547 548 /** 549 * d_backing_dentry - Get upper or lower dentry we should be using 550 * @upper: The upper layer 551 * 552 * This is the helper that should be used to get the dentry of the inode that 553 * will be used if this dentry were opened as a file. It may be the upper 554 * dentry or it may be a lower dentry pinned by the upper. 555 * 556 * Normal filesystems should not use this to access their own dentries. 557 */ 558 static inline struct dentry *d_backing_dentry(struct dentry *upper) 559 { 560 return upper; 561 } 562 563 /** 564 * d_real - Return the real dentry 565 * @dentry: the dentry to query 566 * @inode: inode to select the dentry from multiple layers (can be NULL) 567 * 568 * If dentry is on a union/overlay, then return the underlying, real dentry. 569 * Otherwise return the dentry itself. 570 * 571 * See also: Documentation/filesystems/vfs.rst 572 */ 573 static inline struct dentry *d_real(struct dentry *dentry, 574 const struct inode *inode) 575 { 576 if (unlikely(dentry->d_flags & DCACHE_OP_REAL)) 577 return dentry->d_op->d_real(dentry, inode); 578 else 579 return dentry; 580 } 581 582 /** 583 * d_real_inode - Return the real inode 584 * @dentry: The dentry to query 585 * 586 * If dentry is on a union/overlay, then return the underlying, real inode. 587 * Otherwise return d_inode(). 588 */ 589 static inline struct inode *d_real_inode(const struct dentry *dentry) 590 { 591 /* This usage of d_real() results in const dentry */ 592 return d_backing_inode(d_real((struct dentry *) dentry, NULL)); 593 } 594 595 struct name_snapshot { 596 struct qstr name; 597 unsigned char inline_name[DNAME_INLINE_LEN]; 598 }; 599 void take_dentry_name_snapshot(struct name_snapshot *, struct dentry *); 600 void release_dentry_name_snapshot(struct name_snapshot *); 601 602 #endif /* __LINUX_DCACHE_H */ 603