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 nr_negative; /* # of unused negative dentries */ 68 long dummy; /* Reserved for future use */ 69 }; 70 extern struct dentry_stat_t dentry_stat; 71 72 /* 73 * Try to keep struct dentry aligned on 64 byte cachelines (this will 74 * give reasonable cacheline footprint with larger lines without the 75 * large memory footprint increase). 76 */ 77 #ifdef CONFIG_64BIT 78 # define DNAME_INLINE_LEN 32 /* 192 bytes */ 79 #else 80 # ifdef CONFIG_SMP 81 # define DNAME_INLINE_LEN 36 /* 128 bytes */ 82 # else 83 # define DNAME_INLINE_LEN 40 /* 128 bytes */ 84 # endif 85 #endif 86 87 #define d_lock d_lockref.lock 88 89 struct dentry { 90 /* RCU lookup touched fields */ 91 unsigned int d_flags; /* protected by d_lock */ 92 seqcount_t d_seq; /* per dentry seqlock */ 93 struct hlist_bl_node d_hash; /* lookup hash list */ 94 struct dentry *d_parent; /* parent directory */ 95 struct qstr d_name; 96 struct inode *d_inode; /* Where the name belongs to - NULL is 97 * negative */ 98 unsigned char d_iname[DNAME_INLINE_LEN]; /* small names */ 99 100 /* Ref lookup also touches following */ 101 struct lockref d_lockref; /* per-dentry lock and refcount */ 102 const struct dentry_operations *d_op; 103 struct super_block *d_sb; /* The root of the dentry tree */ 104 unsigned long d_time; /* used by d_revalidate */ 105 void *d_fsdata; /* fs-specific data */ 106 107 union { 108 struct list_head d_lru; /* LRU list */ 109 wait_queue_head_t *d_wait; /* in-lookup ones only */ 110 }; 111 struct list_head d_child; /* child of parent list */ 112 struct list_head d_subdirs; /* our children */ 113 /* 114 * d_alias and d_rcu can share memory 115 */ 116 union { 117 struct hlist_node d_alias; /* inode alias list */ 118 struct hlist_bl_node d_in_lookup_hash; /* only for in-lookup ones */ 119 struct rcu_head d_rcu; 120 } d_u; 121 } __randomize_layout; 122 123 /* 124 * dentry->d_lock spinlock nesting subclasses: 125 * 126 * 0: normal 127 * 1: nested 128 */ 129 enum dentry_d_lock_class 130 { 131 DENTRY_D_LOCK_NORMAL, /* implicitly used by plain spin_lock() APIs. */ 132 DENTRY_D_LOCK_NESTED 133 }; 134 135 struct dentry_operations { 136 int (*d_revalidate)(struct dentry *, unsigned int); 137 int (*d_weak_revalidate)(struct dentry *, unsigned int); 138 int (*d_hash)(const struct dentry *, struct qstr *); 139 int (*d_compare)(const struct dentry *, 140 unsigned int, const char *, const struct qstr *); 141 int (*d_delete)(const struct dentry *); 142 int (*d_init)(struct dentry *); 143 void (*d_release)(struct dentry *); 144 void (*d_prune)(struct dentry *); 145 void (*d_iput)(struct dentry *, struct inode *); 146 char *(*d_dname)(struct dentry *, char *, int); 147 struct vfsmount *(*d_automount)(struct path *); 148 int (*d_manage)(const struct path *, bool); 149 struct dentry *(*d_real)(struct dentry *, const struct inode *); 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.rst. 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. */ 179 180 #define DCACHE_CANT_MOUNT 0x00000100 181 #define DCACHE_GENOCIDE 0x00000200 182 #define DCACHE_SHRINK_LIST 0x00000400 183 184 #define DCACHE_OP_WEAK_REVALIDATE 0x00000800 185 186 #define DCACHE_NFSFS_RENAMED 0x00001000 187 /* this dentry has been "silly renamed" and has to be deleted on the last 188 * dput() */ 189 #define DCACHE_COOKIE 0x00002000 /* For use by dcookie subsystem */ 190 #define DCACHE_FSNOTIFY_PARENT_WATCHED 0x00004000 191 /* Parent inode is watched by some fsnotify listener */ 192 193 #define DCACHE_DENTRY_KILLED 0x00008000 194 195 #define DCACHE_MOUNTED 0x00010000 /* is a mountpoint */ 196 #define DCACHE_NEED_AUTOMOUNT 0x00020000 /* handle automount on this dir */ 197 #define DCACHE_MANAGE_TRANSIT 0x00040000 /* manage transit from this dirent */ 198 #define DCACHE_MANAGED_DENTRY \ 199 (DCACHE_MOUNTED|DCACHE_NEED_AUTOMOUNT|DCACHE_MANAGE_TRANSIT) 200 201 #define DCACHE_LRU_LIST 0x00080000 202 203 #define DCACHE_ENTRY_TYPE 0x00700000 204 #define DCACHE_MISS_TYPE 0x00000000 /* Negative dentry (maybe fallthru to nowhere) */ 205 #define DCACHE_WHITEOUT_TYPE 0x00100000 /* Whiteout dentry (stop pathwalk) */ 206 #define DCACHE_DIRECTORY_TYPE 0x00200000 /* Normal directory */ 207 #define DCACHE_AUTODIR_TYPE 0x00300000 /* Lookupless directory (presumed automount) */ 208 #define DCACHE_REGULAR_TYPE 0x00400000 /* Regular file type (or fallthru to such) */ 209 #define DCACHE_SPECIAL_TYPE 0x00500000 /* Other file type (or fallthru to such) */ 210 #define DCACHE_SYMLINK_TYPE 0x00600000 /* Symlink (or fallthru to such) */ 211 212 #define DCACHE_MAY_FREE 0x00800000 213 #define DCACHE_FALLTHRU 0x01000000 /* Fall through to lower layer */ 214 #define DCACHE_ENCRYPTED_NAME 0x02000000 /* Encrypted name (dir key was unavailable) */ 215 #define DCACHE_OP_REAL 0x04000000 216 217 #define DCACHE_PAR_LOOKUP 0x10000000 /* being looked up (with parent locked shared) */ 218 #define DCACHE_DENTRY_CURSOR 0x20000000 219 #define DCACHE_NORCU 0x40000000 /* No RCU delay for freeing */ 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 void d_instantiate_new(struct dentry *, struct inode *); 228 extern struct dentry * d_instantiate_unique(struct dentry *, struct inode *); 229 extern struct dentry * d_instantiate_anon(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_parallel(struct dentry *, const struct qstr *, 239 wait_queue_head_t *); 240 extern struct dentry * d_splice_alias(struct inode *, struct dentry *); 241 extern struct dentry * d_add_ci(struct dentry *, struct inode *, struct qstr *); 242 extern struct dentry * d_exact_alias(struct dentry *, struct inode *); 243 extern struct dentry *d_find_any_alias(struct inode *inode); 244 extern struct dentry * d_obtain_alias(struct inode *); 245 extern struct dentry * d_obtain_root(struct inode *); 246 extern void shrink_dcache_sb(struct super_block *); 247 extern void shrink_dcache_parent(struct dentry *); 248 extern void shrink_dcache_for_umount(struct super_block *); 249 extern void d_invalidate(struct dentry *); 250 251 /* only used at mount-time */ 252 extern struct dentry * d_make_root(struct inode *); 253 254 /* <clickety>-<click> the ramfs-type tree */ 255 extern void d_genocide(struct dentry *); 256 257 extern void d_tmpfile(struct dentry *, struct inode *); 258 259 extern struct dentry *d_find_alias(struct inode *); 260 extern void d_prune_aliases(struct inode *); 261 262 /* test whether we have any submounts in a subdir tree */ 263 extern int path_has_submounts(const struct path *); 264 265 /* 266 * This adds the entry to the hash queues. 267 */ 268 extern void d_rehash(struct dentry *); 269 270 extern void d_add(struct dentry *, struct inode *); 271 272 /* used for rename() and baskets */ 273 extern void d_move(struct dentry *, struct dentry *); 274 extern void d_exchange(struct dentry *, struct dentry *); 275 extern struct dentry *d_ancestor(struct dentry *, struct dentry *); 276 277 /* appendix may either be NULL or be used for transname suffixes */ 278 extern struct dentry *d_lookup(const struct dentry *, const struct qstr *); 279 extern struct dentry *d_hash_and_lookup(struct dentry *, struct qstr *); 280 extern struct dentry *__d_lookup(const struct dentry *, const struct qstr *); 281 extern struct dentry *__d_lookup_rcu(const struct dentry *parent, 282 const struct qstr *name, unsigned *seq); 283 284 static inline unsigned d_count(const struct dentry *dentry) 285 { 286 return dentry->d_lockref.count; 287 } 288 289 /* 290 * helper function for dentry_operations.d_dname() members 291 */ 292 extern __printf(4, 5) 293 char *dynamic_dname(struct dentry *, char *, int, const char *, ...); 294 extern char *simple_dname(struct dentry *, char *, int); 295 296 extern char *__d_path(const struct path *, const struct path *, char *, int); 297 extern char *d_absolute_path(const struct path *, char *, int); 298 extern char *d_path(const struct path *, char *, int); 299 extern char *dentry_path_raw(struct dentry *, char *, int); 300 extern char *dentry_path(struct dentry *, char *, int); 301 302 /* Allocation counts.. */ 303 304 /** 305 * dget, dget_dlock - get a reference to a dentry 306 * @dentry: dentry to get a reference to 307 * 308 * Given a dentry or %NULL pointer increment the reference count 309 * if appropriate and return the dentry. A dentry will not be 310 * destroyed when it has references. 311 */ 312 static inline struct dentry *dget_dlock(struct dentry *dentry) 313 { 314 if (dentry) 315 dentry->d_lockref.count++; 316 return dentry; 317 } 318 319 static inline struct dentry *dget(struct dentry *dentry) 320 { 321 if (dentry) 322 lockref_get(&dentry->d_lockref); 323 return dentry; 324 } 325 326 extern struct dentry *dget_parent(struct dentry *dentry); 327 328 /** 329 * d_unhashed - is dentry hashed 330 * @dentry: entry to check 331 * 332 * Returns true if the dentry passed is not currently hashed. 333 */ 334 335 static inline int d_unhashed(const struct dentry *dentry) 336 { 337 return hlist_bl_unhashed(&dentry->d_hash); 338 } 339 340 static inline int d_unlinked(const struct dentry *dentry) 341 { 342 return d_unhashed(dentry) && !IS_ROOT(dentry); 343 } 344 345 static inline int cant_mount(const struct dentry *dentry) 346 { 347 return (dentry->d_flags & DCACHE_CANT_MOUNT); 348 } 349 350 static inline void dont_mount(struct dentry *dentry) 351 { 352 spin_lock(&dentry->d_lock); 353 dentry->d_flags |= DCACHE_CANT_MOUNT; 354 spin_unlock(&dentry->d_lock); 355 } 356 357 extern void __d_lookup_done(struct dentry *); 358 359 static inline int d_in_lookup(const struct dentry *dentry) 360 { 361 return dentry->d_flags & DCACHE_PAR_LOOKUP; 362 } 363 364 static inline void d_lookup_done(struct dentry *dentry) 365 { 366 if (unlikely(d_in_lookup(dentry))) { 367 spin_lock(&dentry->d_lock); 368 __d_lookup_done(dentry); 369 spin_unlock(&dentry->d_lock); 370 } 371 } 372 373 extern void dput(struct dentry *); 374 375 static inline bool d_managed(const struct dentry *dentry) 376 { 377 return dentry->d_flags & DCACHE_MANAGED_DENTRY; 378 } 379 380 static inline bool d_mountpoint(const struct dentry *dentry) 381 { 382 return dentry->d_flags & DCACHE_MOUNTED; 383 } 384 385 /* 386 * Directory cache entry type accessor functions. 387 */ 388 static inline unsigned __d_entry_type(const struct dentry *dentry) 389 { 390 return dentry->d_flags & DCACHE_ENTRY_TYPE; 391 } 392 393 static inline bool d_is_miss(const struct dentry *dentry) 394 { 395 return __d_entry_type(dentry) == DCACHE_MISS_TYPE; 396 } 397 398 static inline bool d_is_whiteout(const struct dentry *dentry) 399 { 400 return __d_entry_type(dentry) == DCACHE_WHITEOUT_TYPE; 401 } 402 403 static inline bool d_can_lookup(const struct dentry *dentry) 404 { 405 return __d_entry_type(dentry) == DCACHE_DIRECTORY_TYPE; 406 } 407 408 static inline bool d_is_autodir(const struct dentry *dentry) 409 { 410 return __d_entry_type(dentry) == DCACHE_AUTODIR_TYPE; 411 } 412 413 static inline bool d_is_dir(const struct dentry *dentry) 414 { 415 return d_can_lookup(dentry) || d_is_autodir(dentry); 416 } 417 418 static inline bool d_is_symlink(const struct dentry *dentry) 419 { 420 return __d_entry_type(dentry) == DCACHE_SYMLINK_TYPE; 421 } 422 423 static inline bool d_is_reg(const struct dentry *dentry) 424 { 425 return __d_entry_type(dentry) == DCACHE_REGULAR_TYPE; 426 } 427 428 static inline bool d_is_special(const struct dentry *dentry) 429 { 430 return __d_entry_type(dentry) == DCACHE_SPECIAL_TYPE; 431 } 432 433 static inline bool d_is_file(const struct dentry *dentry) 434 { 435 return d_is_reg(dentry) || d_is_special(dentry); 436 } 437 438 static inline bool d_is_negative(const struct dentry *dentry) 439 { 440 // TODO: check d_is_whiteout(dentry) also. 441 return d_is_miss(dentry); 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