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/rculist.h> 8 #include <linux/rculist_bl.h> 9 #include <linux/spinlock.h> 10 #include <linux/seqlock.h> 11 #include <linux/cache.h> 12 #include <linux/rcupdate.h> 13 #include <linux/lockref.h> 14 #include <linux/stringhash.h> 15 #include <linux/wait.h> 16 17 struct path; 18 struct vfsmount; 19 20 /* 21 * linux/include/linux/dcache.h 22 * 23 * Dirent cache data structures 24 * 25 * (C) Copyright 1997 Thomas Schoebel-Theuer, 26 * with heavy changes by Linus Torvalds 27 */ 28 29 #define IS_ROOT(x) ((x) == (x)->d_parent) 30 31 /* The hash is always the low bits of hash_len */ 32 #ifdef __LITTLE_ENDIAN 33 #define HASH_LEN_DECLARE u32 hash; u32 len 34 #define bytemask_from_count(cnt) (~(~0ul << (cnt)*8)) 35 #else 36 #define HASH_LEN_DECLARE u32 len; u32 hash 37 #define bytemask_from_count(cnt) (~(~0ul >> (cnt)*8)) 38 #endif 39 40 /* 41 * "quick string" -- eases parameter passing, but more importantly 42 * saves "metadata" about the string (ie length and the hash). 43 * 44 * hash comes first so it snuggles against d_parent in the 45 * dentry. 46 */ 47 struct qstr { 48 union { 49 struct { 50 HASH_LEN_DECLARE; 51 }; 52 u64 hash_len; 53 }; 54 const unsigned char *name; 55 }; 56 57 #define QSTR_INIT(n,l) { { { .len = l } }, .name = n } 58 59 extern const struct qstr empty_name; 60 extern const struct qstr slash_name; 61 62 struct dentry_stat_t { 63 long nr_dentry; 64 long nr_unused; 65 long age_limit; /* age in seconds */ 66 long want_pages; /* pages requested by system */ 67 long dummy[2]; 68 }; 69 extern struct dentry_stat_t dentry_stat; 70 71 /* 72 * Try to keep struct dentry aligned on 64 byte cachelines (this will 73 * give reasonable cacheline footprint with larger lines without the 74 * large memory footprint increase). 75 */ 76 #ifdef CONFIG_64BIT 77 # define DNAME_INLINE_LEN 32 /* 192 bytes */ 78 #else 79 # ifdef CONFIG_SMP 80 # define DNAME_INLINE_LEN 36 /* 128 bytes */ 81 # else 82 # define DNAME_INLINE_LEN 40 /* 128 bytes */ 83 # endif 84 #endif 85 86 #define d_lock d_lockref.lock 87 88 struct dentry { 89 /* RCU lookup touched fields */ 90 unsigned int d_flags; /* protected by d_lock */ 91 seqcount_t d_seq; /* per dentry seqlock */ 92 struct hlist_bl_node d_hash; /* lookup hash list */ 93 struct dentry *d_parent; /* parent directory */ 94 struct qstr d_name; 95 struct inode *d_inode; /* Where the name belongs to - NULL is 96 * negative */ 97 unsigned char d_iname[DNAME_INLINE_LEN]; /* small names */ 98 99 /* Ref lookup also touches following */ 100 struct lockref d_lockref; /* per-dentry lock and refcount */ 101 const struct dentry_operations *d_op; 102 struct super_block *d_sb; /* The root of the dentry tree */ 103 unsigned long d_time; /* used by d_revalidate */ 104 void *d_fsdata; /* fs-specific data */ 105 106 union { 107 struct list_head d_lru; /* LRU list */ 108 wait_queue_head_t *d_wait; /* in-lookup ones only */ 109 }; 110 struct list_head d_child; /* child of parent list */ 111 struct list_head d_subdirs; /* our children */ 112 /* 113 * d_alias and d_rcu can share memory 114 */ 115 union { 116 struct hlist_node d_alias; /* inode alias list */ 117 struct hlist_bl_node d_in_lookup_hash; /* only for in-lookup ones */ 118 struct rcu_head d_rcu; 119 } d_u; 120 } __randomize_layout; 121 122 /* 123 * dentry->d_lock spinlock nesting subclasses: 124 * 125 * 0: normal 126 * 1: nested 127 */ 128 enum dentry_d_lock_class 129 { 130 DENTRY_D_LOCK_NORMAL, /* implicitly used by plain spin_lock() APIs. */ 131 DENTRY_D_LOCK_NESTED 132 }; 133 134 struct dentry_operations { 135 int (*d_revalidate)(struct dentry *, unsigned int); 136 int (*d_weak_revalidate)(struct dentry *, unsigned int); 137 int (*d_hash)(const struct dentry *, struct qstr *); 138 int (*d_compare)(const struct dentry *, 139 unsigned int, const char *, const struct qstr *); 140 int (*d_delete)(const struct dentry *); 141 int (*d_init)(struct dentry *); 142 void (*d_release)(struct dentry *); 143 void (*d_prune)(struct dentry *); 144 void (*d_iput)(struct dentry *, struct inode *); 145 char *(*d_dname)(struct dentry *, char *, int); 146 struct vfsmount *(*d_automount)(struct path *); 147 int (*d_manage)(const struct path *, bool); 148 struct dentry *(*d_real)(struct dentry *, const struct inode *, 149 unsigned int, unsigned int); 150 } ____cacheline_aligned; 151 152 /* 153 * Locking rules for dentry_operations callbacks are to be found in 154 * Documentation/filesystems/Locking. Keep it updated! 155 * 156 * FUrther descriptions are found in Documentation/filesystems/vfs.txt. 157 * Keep it updated too! 158 */ 159 160 /* d_flags entries */ 161 #define DCACHE_OP_HASH 0x00000001 162 #define DCACHE_OP_COMPARE 0x00000002 163 #define DCACHE_OP_REVALIDATE 0x00000004 164 #define DCACHE_OP_DELETE 0x00000008 165 #define DCACHE_OP_PRUNE 0x00000010 166 167 #define DCACHE_DISCONNECTED 0x00000020 168 /* This dentry is possibly not currently connected to the dcache tree, in 169 * which case its parent will either be itself, or will have this flag as 170 * well. nfsd will not use a dentry with this bit set, but will first 171 * endeavour to clear the bit either by discovering that it is connected, 172 * or by performing lookup operations. Any filesystem which supports 173 * nfsd_operations MUST have a lookup function which, if it finds a 174 * directory inode with a DCACHE_DISCONNECTED dentry, will d_move that 175 * dentry into place and return that dentry rather than the passed one, 176 * typically using d_splice_alias. */ 177 178 #define DCACHE_REFERENCED 0x00000040 /* Recently used, don't discard. */ 179 #define DCACHE_RCUACCESS 0x00000080 /* Entry has ever been RCU-visible */ 180 181 #define DCACHE_CANT_MOUNT 0x00000100 182 #define DCACHE_GENOCIDE 0x00000200 183 #define DCACHE_SHRINK_LIST 0x00000400 184 185 #define DCACHE_OP_WEAK_REVALIDATE 0x00000800 186 187 #define DCACHE_NFSFS_RENAMED 0x00001000 188 /* this dentry has been "silly renamed" and has to be deleted on the last 189 * dput() */ 190 #define DCACHE_COOKIE 0x00002000 /* For use by dcookie subsystem */ 191 #define DCACHE_FSNOTIFY_PARENT_WATCHED 0x00004000 192 /* Parent inode is watched by some fsnotify listener */ 193 194 #define DCACHE_DENTRY_KILLED 0x00008000 195 196 #define DCACHE_MOUNTED 0x00010000 /* is a mountpoint */ 197 #define DCACHE_NEED_AUTOMOUNT 0x00020000 /* handle automount on this dir */ 198 #define DCACHE_MANAGE_TRANSIT 0x00040000 /* manage transit from this dirent */ 199 #define DCACHE_MANAGED_DENTRY \ 200 (DCACHE_MOUNTED|DCACHE_NEED_AUTOMOUNT|DCACHE_MANAGE_TRANSIT) 201 202 #define DCACHE_LRU_LIST 0x00080000 203 204 #define DCACHE_ENTRY_TYPE 0x00700000 205 #define DCACHE_MISS_TYPE 0x00000000 /* Negative dentry (maybe fallthru to nowhere) */ 206 #define DCACHE_WHITEOUT_TYPE 0x00100000 /* Whiteout dentry (stop pathwalk) */ 207 #define DCACHE_DIRECTORY_TYPE 0x00200000 /* Normal directory */ 208 #define DCACHE_AUTODIR_TYPE 0x00300000 /* Lookupless directory (presumed automount) */ 209 #define DCACHE_REGULAR_TYPE 0x00400000 /* Regular file type (or fallthru to such) */ 210 #define DCACHE_SPECIAL_TYPE 0x00500000 /* Other file type (or fallthru to such) */ 211 #define DCACHE_SYMLINK_TYPE 0x00600000 /* Symlink (or fallthru to such) */ 212 213 #define DCACHE_MAY_FREE 0x00800000 214 #define DCACHE_FALLTHRU 0x01000000 /* Fall through to lower layer */ 215 #define DCACHE_ENCRYPTED_WITH_KEY 0x02000000 /* dir is encrypted with a valid key */ 216 #define DCACHE_OP_REAL 0x04000000 217 218 #define DCACHE_PAR_LOOKUP 0x10000000 /* being looked up (with parent locked shared) */ 219 #define DCACHE_DENTRY_CURSOR 0x20000000 220 221 extern seqlock_t rename_lock; 222 223 /* 224 * These are the low-level FS interfaces to the dcache.. 225 */ 226 extern void d_instantiate(struct dentry *, struct inode *); 227 extern struct dentry * d_instantiate_unique(struct dentry *, struct inode *); 228 extern struct dentry * d_instantiate_anon(struct dentry *, struct inode *); 229 extern int d_instantiate_no_diralias(struct dentry *, struct inode *); 230 extern void __d_drop(struct dentry *dentry); 231 extern void d_drop(struct dentry *dentry); 232 extern void d_delete(struct dentry *); 233 extern void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op); 234 235 /* allocate/de-allocate */ 236 extern struct dentry * d_alloc(struct dentry *, const struct qstr *); 237 extern struct dentry * d_alloc_anon(struct super_block *); 238 extern struct dentry * d_alloc_pseudo(struct super_block *, const struct qstr *); 239 extern struct dentry * d_alloc_parallel(struct dentry *, const struct qstr *, 240 wait_queue_head_t *); 241 extern struct dentry * d_splice_alias(struct inode *, struct dentry *); 242 extern struct dentry * d_add_ci(struct dentry *, struct inode *, struct qstr *); 243 extern struct dentry * d_exact_alias(struct dentry *, struct inode *); 244 extern struct dentry *d_find_any_alias(struct inode *inode); 245 extern struct dentry * d_obtain_alias(struct inode *); 246 extern struct dentry * d_obtain_root(struct inode *); 247 extern void shrink_dcache_sb(struct super_block *); 248 extern void shrink_dcache_parent(struct dentry *); 249 extern void shrink_dcache_for_umount(struct super_block *); 250 extern void d_invalidate(struct dentry *); 251 252 /* only used at mount-time */ 253 extern struct dentry * d_make_root(struct inode *); 254 255 /* <clickety>-<click> the ramfs-type tree */ 256 extern void d_genocide(struct dentry *); 257 258 extern void d_tmpfile(struct dentry *, struct inode *); 259 260 extern struct dentry *d_find_alias(struct inode *); 261 extern void d_prune_aliases(struct inode *); 262 263 /* test whether we have any submounts in a subdir tree */ 264 extern int path_has_submounts(const struct path *); 265 266 /* 267 * This adds the entry to the hash queues. 268 */ 269 extern void d_rehash(struct dentry *); 270 271 extern void d_add(struct dentry *, struct inode *); 272 273 extern void dentry_update_name_case(struct dentry *, const struct qstr *); 274 275 /* used for rename() and baskets */ 276 extern void d_move(struct dentry *, struct dentry *); 277 extern void d_exchange(struct dentry *, struct dentry *); 278 extern struct dentry *d_ancestor(struct dentry *, struct dentry *); 279 280 /* appendix may either be NULL or be used for transname suffixes */ 281 extern struct dentry *d_lookup(const struct dentry *, const struct qstr *); 282 extern struct dentry *d_hash_and_lookup(struct dentry *, struct qstr *); 283 extern struct dentry *__d_lookup(const struct dentry *, const struct qstr *); 284 extern struct dentry *__d_lookup_rcu(const struct dentry *parent, 285 const struct qstr *name, unsigned *seq); 286 287 static inline unsigned d_count(const struct dentry *dentry) 288 { 289 return dentry->d_lockref.count; 290 } 291 292 /* 293 * helper function for dentry_operations.d_dname() members 294 */ 295 extern __printf(4, 5) 296 char *dynamic_dname(struct dentry *, char *, int, const char *, ...); 297 extern char *simple_dname(struct dentry *, char *, int); 298 299 extern char *__d_path(const struct path *, const struct path *, char *, int); 300 extern char *d_absolute_path(const struct path *, char *, int); 301 extern char *d_path(const struct path *, char *, int); 302 extern char *dentry_path_raw(struct dentry *, char *, int); 303 extern char *dentry_path(struct dentry *, char *, int); 304 305 /* Allocation counts.. */ 306 307 /** 308 * dget, dget_dlock - get a reference to a dentry 309 * @dentry: dentry to get a reference to 310 * 311 * Given a dentry or %NULL pointer increment the reference count 312 * if appropriate and return the dentry. A dentry will not be 313 * destroyed when it has references. 314 */ 315 static inline struct dentry *dget_dlock(struct dentry *dentry) 316 { 317 if (dentry) 318 dentry->d_lockref.count++; 319 return dentry; 320 } 321 322 static inline struct dentry *dget(struct dentry *dentry) 323 { 324 if (dentry) 325 lockref_get(&dentry->d_lockref); 326 return dentry; 327 } 328 329 extern struct dentry *dget_parent(struct dentry *dentry); 330 331 /** 332 * d_unhashed - is dentry hashed 333 * @dentry: entry to check 334 * 335 * Returns true if the dentry passed is not currently hashed. 336 */ 337 338 static inline int d_unhashed(const struct dentry *dentry) 339 { 340 return hlist_bl_unhashed(&dentry->d_hash); 341 } 342 343 static inline int d_unlinked(const struct dentry *dentry) 344 { 345 return d_unhashed(dentry) && !IS_ROOT(dentry); 346 } 347 348 static inline int cant_mount(const struct dentry *dentry) 349 { 350 return (dentry->d_flags & DCACHE_CANT_MOUNT); 351 } 352 353 static inline void dont_mount(struct dentry *dentry) 354 { 355 spin_lock(&dentry->d_lock); 356 dentry->d_flags |= DCACHE_CANT_MOUNT; 357 spin_unlock(&dentry->d_lock); 358 } 359 360 extern void __d_lookup_done(struct dentry *); 361 362 static inline int d_in_lookup(const struct dentry *dentry) 363 { 364 return dentry->d_flags & DCACHE_PAR_LOOKUP; 365 } 366 367 static inline void d_lookup_done(struct dentry *dentry) 368 { 369 if (unlikely(d_in_lookup(dentry))) { 370 spin_lock(&dentry->d_lock); 371 __d_lookup_done(dentry); 372 spin_unlock(&dentry->d_lock); 373 } 374 } 375 376 extern void dput(struct dentry *); 377 378 static inline bool d_managed(const struct dentry *dentry) 379 { 380 return dentry->d_flags & DCACHE_MANAGED_DENTRY; 381 } 382 383 static inline bool d_mountpoint(const struct dentry *dentry) 384 { 385 return dentry->d_flags & DCACHE_MOUNTED; 386 } 387 388 /* 389 * Directory cache entry type accessor functions. 390 */ 391 static inline unsigned __d_entry_type(const struct dentry *dentry) 392 { 393 return dentry->d_flags & DCACHE_ENTRY_TYPE; 394 } 395 396 static inline bool d_is_miss(const struct dentry *dentry) 397 { 398 return __d_entry_type(dentry) == DCACHE_MISS_TYPE; 399 } 400 401 static inline bool d_is_whiteout(const struct dentry *dentry) 402 { 403 return __d_entry_type(dentry) == DCACHE_WHITEOUT_TYPE; 404 } 405 406 static inline bool d_can_lookup(const struct dentry *dentry) 407 { 408 return __d_entry_type(dentry) == DCACHE_DIRECTORY_TYPE; 409 } 410 411 static inline bool d_is_autodir(const struct dentry *dentry) 412 { 413 return __d_entry_type(dentry) == DCACHE_AUTODIR_TYPE; 414 } 415 416 static inline bool d_is_dir(const struct dentry *dentry) 417 { 418 return d_can_lookup(dentry) || d_is_autodir(dentry); 419 } 420 421 static inline bool d_is_symlink(const struct dentry *dentry) 422 { 423 return __d_entry_type(dentry) == DCACHE_SYMLINK_TYPE; 424 } 425 426 static inline bool d_is_reg(const struct dentry *dentry) 427 { 428 return __d_entry_type(dentry) == DCACHE_REGULAR_TYPE; 429 } 430 431 static inline bool d_is_special(const struct dentry *dentry) 432 { 433 return __d_entry_type(dentry) == DCACHE_SPECIAL_TYPE; 434 } 435 436 static inline bool d_is_file(const struct dentry *dentry) 437 { 438 return d_is_reg(dentry) || d_is_special(dentry); 439 } 440 441 static inline bool d_is_negative(const struct dentry *dentry) 442 { 443 // TODO: check d_is_whiteout(dentry) also. 444 return d_is_miss(dentry); 445 } 446 447 static inline bool d_is_positive(const struct dentry *dentry) 448 { 449 return !d_is_negative(dentry); 450 } 451 452 /** 453 * d_really_is_negative - Determine if a dentry is really negative (ignoring fallthroughs) 454 * @dentry: The dentry in question 455 * 456 * Returns true if the dentry represents either an absent name or a name that 457 * doesn't map to an inode (ie. ->d_inode is NULL). The dentry could represent 458 * a true miss, a whiteout that isn't represented by a 0,0 chardev or a 459 * fallthrough marker in an opaque directory. 460 * 461 * Note! (1) This should be used *only* by a filesystem to examine its own 462 * dentries. It should not be used to look at some other filesystem's 463 * dentries. (2) It should also be used in combination with d_inode() to get 464 * the inode. (3) The dentry may have something attached to ->d_lower and the 465 * type field of the flags may be set to something other than miss or whiteout. 466 */ 467 static inline bool d_really_is_negative(const struct dentry *dentry) 468 { 469 return dentry->d_inode == NULL; 470 } 471 472 /** 473 * d_really_is_positive - Determine if a dentry is really positive (ignoring fallthroughs) 474 * @dentry: The dentry in question 475 * 476 * Returns true if the dentry represents a name that maps to an inode 477 * (ie. ->d_inode is not NULL). The dentry might still represent a whiteout if 478 * that is represented on medium as a 0,0 chardev. 479 * 480 * Note! (1) This should be used *only* by a filesystem to examine its own 481 * dentries. It should not be used to look at some other filesystem's 482 * dentries. (2) It should also be used in combination with d_inode() to get 483 * the inode. 484 */ 485 static inline bool d_really_is_positive(const struct dentry *dentry) 486 { 487 return dentry->d_inode != NULL; 488 } 489 490 static inline int simple_positive(const struct dentry *dentry) 491 { 492 return d_really_is_positive(dentry) && !d_unhashed(dentry); 493 } 494 495 extern void d_set_fallthru(struct dentry *dentry); 496 497 static inline bool d_is_fallthru(const struct dentry *dentry) 498 { 499 return dentry->d_flags & DCACHE_FALLTHRU; 500 } 501 502 503 extern int sysctl_vfs_cache_pressure; 504 505 static inline unsigned long vfs_pressure_ratio(unsigned long val) 506 { 507 return mult_frac(val, sysctl_vfs_cache_pressure, 100); 508 } 509 510 /** 511 * d_inode - Get the actual inode of this dentry 512 * @dentry: The dentry to query 513 * 514 * This is the helper normal filesystems should use to get at their own inodes 515 * in their own dentries and ignore the layering superimposed upon them. 516 */ 517 static inline struct inode *d_inode(const struct dentry *dentry) 518 { 519 return dentry->d_inode; 520 } 521 522 /** 523 * d_inode_rcu - Get the actual inode of this dentry with READ_ONCE() 524 * @dentry: The dentry to query 525 * 526 * This is the helper normal filesystems should use to get at their own inodes 527 * in their own dentries and ignore the layering superimposed upon them. 528 */ 529 static inline struct inode *d_inode_rcu(const struct dentry *dentry) 530 { 531 return READ_ONCE(dentry->d_inode); 532 } 533 534 /** 535 * d_backing_inode - Get upper or lower inode we should be using 536 * @upper: The upper layer 537 * 538 * This is the helper that should be used to get at the inode that will be used 539 * if this dentry were to be opened as a file. The inode may be on the upper 540 * dentry or it may be on a lower dentry pinned by the upper. 541 * 542 * Normal filesystems should not use this to access their own inodes. 543 */ 544 static inline struct inode *d_backing_inode(const struct dentry *upper) 545 { 546 struct inode *inode = upper->d_inode; 547 548 return inode; 549 } 550 551 /** 552 * d_backing_dentry - Get upper or lower dentry we should be using 553 * @upper: The upper layer 554 * 555 * This is the helper that should be used to get the dentry of the inode that 556 * will be used if this dentry were opened as a file. It may be the upper 557 * dentry or it may be a lower dentry pinned by the upper. 558 * 559 * Normal filesystems should not use this to access their own dentries. 560 */ 561 static inline struct dentry *d_backing_dentry(struct dentry *upper) 562 { 563 return upper; 564 } 565 566 /* d_real() flags */ 567 #define D_REAL_UPPER 0x2 /* return upper dentry or NULL if non-upper */ 568 569 /** 570 * d_real - Return the real dentry 571 * @dentry: the dentry to query 572 * @inode: inode to select the dentry from multiple layers (can be NULL) 573 * @open_flags: open flags to control copy-up behavior 574 * @flags: flags to control what is returned by this function 575 * 576 * If dentry is on a union/overlay, then return the underlying, real dentry. 577 * Otherwise return the dentry itself. 578 * 579 * See also: Documentation/filesystems/vfs.txt 580 */ 581 static inline struct dentry *d_real(struct dentry *dentry, 582 const struct inode *inode, 583 unsigned int open_flags, unsigned int flags) 584 { 585 if (unlikely(dentry->d_flags & DCACHE_OP_REAL)) 586 return dentry->d_op->d_real(dentry, inode, open_flags, flags); 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, 0, 0)); 602 } 603 604 struct name_snapshot { 605 const unsigned char *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