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 }; 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 BIT(0) 155 #define DCACHE_OP_COMPARE BIT(1) 156 #define DCACHE_OP_REVALIDATE BIT(2) 157 #define DCACHE_OP_DELETE BIT(3) 158 #define DCACHE_OP_PRUNE BIT(4) 159 160 #define DCACHE_DISCONNECTED BIT(5) 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 BIT(6) /* Recently used, don't discard. */ 172 173 #define DCACHE_DONTCACHE BIT(7) /* Purge from memory on final dput() */ 174 175 #define DCACHE_CANT_MOUNT BIT(8) 176 #define DCACHE_GENOCIDE BIT(9) 177 #define DCACHE_SHRINK_LIST BIT(10) 178 179 #define DCACHE_OP_WEAK_REVALIDATE BIT(11) 180 181 #define DCACHE_NFSFS_RENAMED BIT(12) 182 /* this dentry has been "silly renamed" and has to be deleted on the last 183 * dput() */ 184 #define DCACHE_FSNOTIFY_PARENT_WATCHED BIT(14) 185 /* Parent inode is watched by some fsnotify listener */ 186 187 #define DCACHE_DENTRY_KILLED BIT(15) 188 189 #define DCACHE_MOUNTED BIT(16) /* is a mountpoint */ 190 #define DCACHE_NEED_AUTOMOUNT BIT(17) /* handle automount on this dir */ 191 #define DCACHE_MANAGE_TRANSIT BIT(18) /* 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 BIT(19) 196 197 #define DCACHE_ENTRY_TYPE (7 << 20) /* bits 20..22 are for storing type: */ 198 #define DCACHE_MISS_TYPE (0 << 20) /* Negative dentry */ 199 #define DCACHE_WHITEOUT_TYPE (1 << 20) /* Whiteout dentry (stop pathwalk) */ 200 #define DCACHE_DIRECTORY_TYPE (2 << 20) /* Normal directory */ 201 #define DCACHE_AUTODIR_TYPE (3 << 20) /* Lookupless directory (presumed automount) */ 202 #define DCACHE_REGULAR_TYPE (4 << 20) /* Regular file type */ 203 #define DCACHE_SPECIAL_TYPE (5 << 20) /* Other file type */ 204 #define DCACHE_SYMLINK_TYPE (6 << 20) /* Symlink */ 205 206 #define DCACHE_MAY_FREE BIT(23) 207 #define DCACHE_NOKEY_NAME BIT(25) /* Encrypted name encoded without key */ 208 #define DCACHE_OP_REAL BIT(26) 209 210 #define DCACHE_PAR_LOOKUP BIT(28) /* being looked up (with parent locked shared) */ 211 #define DCACHE_DENTRY_CURSOR BIT(29) 212 #define DCACHE_NORCU BIT(30) /* No RCU delay for freeing */ 213 214 extern seqlock_t rename_lock; 215 216 /* 217 * These are the low-level FS interfaces to the dcache.. 218 */ 219 extern void d_instantiate(struct dentry *, struct inode *); 220 extern void d_instantiate_new(struct dentry *, struct inode *); 221 extern struct dentry * d_instantiate_unique(struct dentry *, struct inode *); 222 extern struct dentry * d_instantiate_anon(struct dentry *, struct inode *); 223 extern void __d_drop(struct dentry *dentry); 224 extern void d_drop(struct dentry *dentry); 225 extern void d_delete(struct dentry *); 226 extern void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op); 227 228 /* allocate/de-allocate */ 229 extern struct dentry * d_alloc(struct dentry *, const struct qstr *); 230 extern struct dentry * d_alloc_anon(struct super_block *); 231 extern struct dentry * d_alloc_parallel(struct dentry *, const struct qstr *, 232 wait_queue_head_t *); 233 extern struct dentry * d_splice_alias(struct inode *, struct dentry *); 234 extern struct dentry * d_add_ci(struct dentry *, struct inode *, struct qstr *); 235 extern bool d_same_name(const struct dentry *dentry, const struct dentry *parent, 236 const struct qstr *name); 237 extern struct dentry * d_exact_alias(struct dentry *, struct inode *); 238 extern struct dentry *d_find_any_alias(struct inode *inode); 239 extern struct dentry * d_obtain_alias(struct inode *); 240 extern struct dentry * d_obtain_root(struct inode *); 241 extern void shrink_dcache_sb(struct super_block *); 242 extern void shrink_dcache_parent(struct dentry *); 243 extern void shrink_dcache_for_umount(struct super_block *); 244 extern void d_invalidate(struct dentry *); 245 246 /* only used at mount-time */ 247 extern struct dentry * d_make_root(struct inode *); 248 249 /* <clickety>-<click> the ramfs-type tree */ 250 extern void d_genocide(struct dentry *); 251 252 extern void d_mark_tmpfile(struct file *, struct inode *); 253 extern void d_tmpfile(struct file *, 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(3, 4) 291 char *dynamic_dname(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 int sysctl_vfs_cache_pressure; 492 493 static inline unsigned long vfs_pressure_ratio(unsigned long val) 494 { 495 return mult_frac(val, sysctl_vfs_cache_pressure, 100); 496 } 497 498 /** 499 * d_inode - Get the actual inode of this dentry 500 * @dentry: The dentry to query 501 * 502 * This is the helper normal filesystems should use to get at their own inodes 503 * in their own dentries and ignore the layering superimposed upon them. 504 */ 505 static inline struct inode *d_inode(const struct dentry *dentry) 506 { 507 return dentry->d_inode; 508 } 509 510 /** 511 * d_inode_rcu - Get the actual inode of this dentry with READ_ONCE() 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_rcu(const struct dentry *dentry) 518 { 519 return READ_ONCE(dentry->d_inode); 520 } 521 522 /** 523 * d_backing_inode - Get upper or lower inode we should be using 524 * @upper: The upper layer 525 * 526 * This is the helper that should be used to get at the inode that will be used 527 * if this dentry were to be opened as a file. The inode may be on the upper 528 * dentry or it may be on a lower dentry pinned by the upper. 529 * 530 * Normal filesystems should not use this to access their own inodes. 531 */ 532 static inline struct inode *d_backing_inode(const struct dentry *upper) 533 { 534 struct inode *inode = upper->d_inode; 535 536 return inode; 537 } 538 539 /** 540 * d_backing_dentry - Get upper or lower dentry we should be using 541 * @upper: The upper layer 542 * 543 * This is the helper that should be used to get the dentry of the inode that 544 * will be used if this dentry were opened as a file. It may be the upper 545 * dentry or it may be a lower dentry pinned by the upper. 546 * 547 * Normal filesystems should not use this to access their own dentries. 548 */ 549 static inline struct dentry *d_backing_dentry(struct dentry *upper) 550 { 551 return upper; 552 } 553 554 /** 555 * d_real - Return the real dentry 556 * @dentry: the dentry to query 557 * @inode: inode to select the dentry from multiple layers (can be NULL) 558 * 559 * If dentry is on a union/overlay, then return the underlying, real dentry. 560 * Otherwise return the dentry itself. 561 * 562 * See also: Documentation/filesystems/vfs.rst 563 */ 564 static inline struct dentry *d_real(struct dentry *dentry, 565 const struct inode *inode) 566 { 567 if (unlikely(dentry->d_flags & DCACHE_OP_REAL)) 568 return dentry->d_op->d_real(dentry, inode); 569 else 570 return dentry; 571 } 572 573 /** 574 * d_real_inode - Return the real inode 575 * @dentry: The dentry to query 576 * 577 * If dentry is on a union/overlay, then return the underlying, real inode. 578 * Otherwise return d_inode(). 579 */ 580 static inline struct inode *d_real_inode(const struct dentry *dentry) 581 { 582 /* This usage of d_real() results in const dentry */ 583 return d_backing_inode(d_real((struct dentry *) dentry, NULL)); 584 } 585 586 struct name_snapshot { 587 struct qstr name; 588 unsigned char inline_name[DNAME_INLINE_LEN]; 589 }; 590 void take_dentry_name_snapshot(struct name_snapshot *, struct dentry *); 591 void release_dentry_name_snapshot(struct name_snapshot *); 592 593 #endif /* __LINUX_DCACHE_H */ 594