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_anon(struct dentry *, struct inode *); 222 extern void __d_drop(struct dentry *dentry); 223 extern void d_drop(struct dentry *dentry); 224 extern void d_delete(struct dentry *); 225 extern void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op); 226 227 /* allocate/de-allocate */ 228 extern struct dentry * d_alloc(struct dentry *, const struct qstr *); 229 extern struct dentry * d_alloc_anon(struct super_block *); 230 extern struct dentry * d_alloc_parallel(struct dentry *, const struct qstr *, 231 wait_queue_head_t *); 232 extern struct dentry * d_splice_alias(struct inode *, struct dentry *); 233 extern struct dentry * d_add_ci(struct dentry *, struct inode *, struct qstr *); 234 extern bool d_same_name(const struct dentry *dentry, const struct dentry *parent, 235 const struct qstr *name); 236 extern struct dentry * d_exact_alias(struct dentry *, struct inode *); 237 extern struct dentry *d_find_any_alias(struct inode *inode); 238 extern struct dentry * d_obtain_alias(struct inode *); 239 extern struct dentry * d_obtain_root(struct inode *); 240 extern void shrink_dcache_sb(struct super_block *); 241 extern void shrink_dcache_parent(struct dentry *); 242 extern void d_invalidate(struct dentry *); 243 244 /* only used at mount-time */ 245 extern struct dentry * d_make_root(struct inode *); 246 247 /* <clickety>-<click> the ramfs-type tree */ 248 extern void d_genocide(struct dentry *); 249 250 extern void d_mark_tmpfile(struct file *, struct inode *); 251 extern void d_tmpfile(struct file *, struct inode *); 252 253 extern struct dentry *d_find_alias(struct inode *); 254 extern void d_prune_aliases(struct inode *); 255 256 extern struct dentry *d_find_alias_rcu(struct inode *); 257 258 /* test whether we have any submounts in a subdir tree */ 259 extern int path_has_submounts(const struct path *); 260 261 /* 262 * This adds the entry to the hash queues. 263 */ 264 extern void d_rehash(struct dentry *); 265 266 extern void d_add(struct dentry *, struct inode *); 267 268 /* used for rename() and baskets */ 269 extern void d_move(struct dentry *, struct dentry *); 270 extern void d_exchange(struct dentry *, struct dentry *); 271 extern struct dentry *d_ancestor(struct dentry *, struct dentry *); 272 273 extern struct dentry *d_lookup(const struct dentry *, const struct qstr *); 274 extern struct dentry *d_hash_and_lookup(struct dentry *, struct qstr *); 275 276 static inline unsigned d_count(const struct dentry *dentry) 277 { 278 return dentry->d_lockref.count; 279 } 280 281 /* 282 * helper function for dentry_operations.d_dname() members 283 */ 284 extern __printf(3, 4) 285 char *dynamic_dname(char *, int, const char *, ...); 286 287 extern char *__d_path(const struct path *, const struct path *, char *, int); 288 extern char *d_absolute_path(const struct path *, char *, int); 289 extern char *d_path(const struct path *, char *, int); 290 extern char *dentry_path_raw(const struct dentry *, char *, int); 291 extern char *dentry_path(const struct dentry *, char *, int); 292 293 /* Allocation counts.. */ 294 295 /** 296 * dget, dget_dlock - get a reference to a dentry 297 * @dentry: dentry to get a reference to 298 * 299 * Given a dentry or %NULL pointer increment the reference count 300 * if appropriate and return the dentry. A dentry will not be 301 * destroyed when it has references. 302 */ 303 static inline struct dentry *dget_dlock(struct dentry *dentry) 304 { 305 if (dentry) 306 dentry->d_lockref.count++; 307 return dentry; 308 } 309 310 static inline struct dentry *dget(struct dentry *dentry) 311 { 312 if (dentry) 313 lockref_get(&dentry->d_lockref); 314 return dentry; 315 } 316 317 extern struct dentry *dget_parent(struct dentry *dentry); 318 319 /** 320 * d_unhashed - is dentry hashed 321 * @dentry: entry to check 322 * 323 * Returns true if the dentry passed is not currently hashed. 324 */ 325 326 static inline int d_unhashed(const struct dentry *dentry) 327 { 328 return hlist_bl_unhashed(&dentry->d_hash); 329 } 330 331 static inline int d_unlinked(const struct dentry *dentry) 332 { 333 return d_unhashed(dentry) && !IS_ROOT(dentry); 334 } 335 336 static inline int cant_mount(const struct dentry *dentry) 337 { 338 return (dentry->d_flags & DCACHE_CANT_MOUNT); 339 } 340 341 static inline void dont_mount(struct dentry *dentry) 342 { 343 spin_lock(&dentry->d_lock); 344 dentry->d_flags |= DCACHE_CANT_MOUNT; 345 spin_unlock(&dentry->d_lock); 346 } 347 348 extern void __d_lookup_unhash_wake(struct dentry *dentry); 349 350 static inline int d_in_lookup(const struct dentry *dentry) 351 { 352 return dentry->d_flags & DCACHE_PAR_LOOKUP; 353 } 354 355 static inline void d_lookup_done(struct dentry *dentry) 356 { 357 if (unlikely(d_in_lookup(dentry))) 358 __d_lookup_unhash_wake(dentry); 359 } 360 361 extern void dput(struct dentry *); 362 363 static inline bool d_managed(const struct dentry *dentry) 364 { 365 return dentry->d_flags & DCACHE_MANAGED_DENTRY; 366 } 367 368 static inline bool d_mountpoint(const struct dentry *dentry) 369 { 370 return dentry->d_flags & DCACHE_MOUNTED; 371 } 372 373 /* 374 * Directory cache entry type accessor functions. 375 */ 376 static inline unsigned __d_entry_type(const struct dentry *dentry) 377 { 378 return dentry->d_flags & DCACHE_ENTRY_TYPE; 379 } 380 381 static inline bool d_is_miss(const struct dentry *dentry) 382 { 383 return __d_entry_type(dentry) == DCACHE_MISS_TYPE; 384 } 385 386 static inline bool d_is_whiteout(const struct dentry *dentry) 387 { 388 return __d_entry_type(dentry) == DCACHE_WHITEOUT_TYPE; 389 } 390 391 static inline bool d_can_lookup(const struct dentry *dentry) 392 { 393 return __d_entry_type(dentry) == DCACHE_DIRECTORY_TYPE; 394 } 395 396 static inline bool d_is_autodir(const struct dentry *dentry) 397 { 398 return __d_entry_type(dentry) == DCACHE_AUTODIR_TYPE; 399 } 400 401 static inline bool d_is_dir(const struct dentry *dentry) 402 { 403 return d_can_lookup(dentry) || d_is_autodir(dentry); 404 } 405 406 static inline bool d_is_symlink(const struct dentry *dentry) 407 { 408 return __d_entry_type(dentry) == DCACHE_SYMLINK_TYPE; 409 } 410 411 static inline bool d_is_reg(const struct dentry *dentry) 412 { 413 return __d_entry_type(dentry) == DCACHE_REGULAR_TYPE; 414 } 415 416 static inline bool d_is_special(const struct dentry *dentry) 417 { 418 return __d_entry_type(dentry) == DCACHE_SPECIAL_TYPE; 419 } 420 421 static inline bool d_is_file(const struct dentry *dentry) 422 { 423 return d_is_reg(dentry) || d_is_special(dentry); 424 } 425 426 static inline bool d_is_negative(const struct dentry *dentry) 427 { 428 // TODO: check d_is_whiteout(dentry) also. 429 return d_is_miss(dentry); 430 } 431 432 static inline bool d_flags_negative(unsigned flags) 433 { 434 return (flags & DCACHE_ENTRY_TYPE) == DCACHE_MISS_TYPE; 435 } 436 437 static inline bool d_is_positive(const struct dentry *dentry) 438 { 439 return !d_is_negative(dentry); 440 } 441 442 /** 443 * d_really_is_negative - Determine if a dentry is really negative (ignoring fallthroughs) 444 * @dentry: The dentry in question 445 * 446 * Returns true if the dentry represents either an absent name or a name that 447 * doesn't map to an inode (ie. ->d_inode is NULL). The dentry could represent 448 * a true miss, a whiteout that isn't represented by a 0,0 chardev or a 449 * fallthrough marker in an opaque directory. 450 * 451 * Note! (1) This should be used *only* by a filesystem to examine its own 452 * dentries. It should not be used to look at some other filesystem's 453 * dentries. (2) It should also be used in combination with d_inode() to get 454 * the inode. (3) The dentry may have something attached to ->d_lower and the 455 * type field of the flags may be set to something other than miss or whiteout. 456 */ 457 static inline bool d_really_is_negative(const struct dentry *dentry) 458 { 459 return dentry->d_inode == NULL; 460 } 461 462 /** 463 * d_really_is_positive - Determine if a dentry is really positive (ignoring fallthroughs) 464 * @dentry: The dentry in question 465 * 466 * Returns true if the dentry represents a name that maps to an inode 467 * (ie. ->d_inode is not NULL). The dentry might still represent a whiteout if 468 * that is represented on medium as a 0,0 chardev. 469 * 470 * Note! (1) This should be used *only* by a filesystem to examine its own 471 * dentries. It should not be used to look at some other filesystem's 472 * dentries. (2) It should also be used in combination with d_inode() to get 473 * the inode. 474 */ 475 static inline bool d_really_is_positive(const struct dentry *dentry) 476 { 477 return dentry->d_inode != NULL; 478 } 479 480 static inline int simple_positive(const struct dentry *dentry) 481 { 482 return d_really_is_positive(dentry) && !d_unhashed(dentry); 483 } 484 485 extern int sysctl_vfs_cache_pressure; 486 487 static inline unsigned long vfs_pressure_ratio(unsigned long val) 488 { 489 return mult_frac(val, sysctl_vfs_cache_pressure, 100); 490 } 491 492 /** 493 * d_inode - Get the actual inode of this dentry 494 * @dentry: The dentry to query 495 * 496 * This is the helper normal filesystems should use to get at their own inodes 497 * in their own dentries and ignore the layering superimposed upon them. 498 */ 499 static inline struct inode *d_inode(const struct dentry *dentry) 500 { 501 return dentry->d_inode; 502 } 503 504 /** 505 * d_inode_rcu - Get the actual inode of this dentry with READ_ONCE() 506 * @dentry: The dentry to query 507 * 508 * This is the helper normal filesystems should use to get at their own inodes 509 * in their own dentries and ignore the layering superimposed upon them. 510 */ 511 static inline struct inode *d_inode_rcu(const struct dentry *dentry) 512 { 513 return READ_ONCE(dentry->d_inode); 514 } 515 516 /** 517 * d_backing_inode - Get upper or lower inode we should be using 518 * @upper: The upper layer 519 * 520 * This is the helper that should be used to get at the inode that will be used 521 * if this dentry were to be opened as a file. The inode may be on the upper 522 * dentry or it may be on a lower dentry pinned by the upper. 523 * 524 * Normal filesystems should not use this to access their own inodes. 525 */ 526 static inline struct inode *d_backing_inode(const struct dentry *upper) 527 { 528 struct inode *inode = upper->d_inode; 529 530 return inode; 531 } 532 533 /** 534 * d_backing_dentry - Get upper or lower dentry we should be using 535 * @upper: The upper layer 536 * 537 * This is the helper that should be used to get the dentry of the inode that 538 * will be used if this dentry were opened as a file. It may be the upper 539 * dentry or it may be a lower dentry pinned by the upper. 540 * 541 * Normal filesystems should not use this to access their own dentries. 542 */ 543 static inline struct dentry *d_backing_dentry(struct dentry *upper) 544 { 545 return upper; 546 } 547 548 /** 549 * d_real - Return the real dentry 550 * @dentry: the dentry to query 551 * @inode: inode to select the dentry from multiple layers (can be NULL) 552 * 553 * If dentry is on a union/overlay, then return the underlying, real dentry. 554 * Otherwise return the dentry itself. 555 * 556 * See also: Documentation/filesystems/vfs.rst 557 */ 558 static inline struct dentry *d_real(struct dentry *dentry, 559 const struct inode *inode) 560 { 561 if (unlikely(dentry->d_flags & DCACHE_OP_REAL)) 562 return dentry->d_op->d_real(dentry, inode); 563 else 564 return dentry; 565 } 566 567 /** 568 * d_real_inode - Return the real inode 569 * @dentry: The dentry to query 570 * 571 * If dentry is on a union/overlay, then return the underlying, real inode. 572 * Otherwise return d_inode(). 573 */ 574 static inline struct inode *d_real_inode(const struct dentry *dentry) 575 { 576 /* This usage of d_real() results in const dentry */ 577 return d_backing_inode(d_real((struct dentry *) dentry, NULL)); 578 } 579 580 struct name_snapshot { 581 struct qstr name; 582 unsigned char inline_name[DNAME_INLINE_LEN]; 583 }; 584 void take_dentry_name_snapshot(struct name_snapshot *, struct dentry *); 585 void release_dentry_name_snapshot(struct name_snapshot *); 586 587 #endif /* __LINUX_DCACHE_H */ 588