1 #ifndef __LINUX_DCACHE_H 2 #define __LINUX_DCACHE_H 3 4 #include <linux/atomic.h> 5 #include <linux/list.h> 6 #include <linux/rculist.h> 7 #include <linux/rculist_bl.h> 8 #include <linux/spinlock.h> 9 #include <linux/seqlock.h> 10 #include <linux/cache.h> 11 #include <linux/rcupdate.h> 12 #include <linux/lockref.h> 13 14 struct path; 15 struct vfsmount; 16 17 /* 18 * linux/include/linux/dcache.h 19 * 20 * Dirent cache data structures 21 * 22 * (C) Copyright 1997 Thomas Schoebel-Theuer, 23 * with heavy changes by Linus Torvalds 24 */ 25 26 #define IS_ROOT(x) ((x) == (x)->d_parent) 27 28 /* The hash is always the low bits of hash_len */ 29 #ifdef __LITTLE_ENDIAN 30 #define HASH_LEN_DECLARE u32 hash; u32 len 31 #define bytemask_from_count(cnt) (~(~0ul << (cnt)*8)) 32 #else 33 #define HASH_LEN_DECLARE u32 len; u32 hash 34 #define bytemask_from_count(cnt) (~(~0ul >> (cnt)*8)) 35 #endif 36 37 /* 38 * "quick string" -- eases parameter passing, but more importantly 39 * saves "metadata" about the string (ie length and the hash). 40 * 41 * hash comes first so it snuggles against d_parent in the 42 * dentry. 43 */ 44 struct qstr { 45 union { 46 struct { 47 HASH_LEN_DECLARE; 48 }; 49 u64 hash_len; 50 }; 51 const unsigned char *name; 52 }; 53 54 #define QSTR_INIT(n,l) { { { .len = l } }, .name = n } 55 #define hashlen_hash(hashlen) ((u32) (hashlen)) 56 #define hashlen_len(hashlen) ((u32)((hashlen) >> 32)) 57 #define hashlen_create(hash,len) (((u64)(len)<<32)|(u32)(hash)) 58 59 struct dentry_stat_t { 60 long nr_dentry; 61 long nr_unused; 62 long age_limit; /* age in seconds */ 63 long want_pages; /* pages requested by system */ 64 long dummy[2]; 65 }; 66 extern struct dentry_stat_t dentry_stat; 67 68 /* Name hashing routines. Initial hash value */ 69 /* Hash courtesy of the R5 hash in reiserfs modulo sign bits */ 70 #define init_name_hash() 0 71 72 /* partial hash update function. Assume roughly 4 bits per character */ 73 static inline unsigned long 74 partial_name_hash(unsigned long c, unsigned long prevhash) 75 { 76 return (prevhash + (c << 4) + (c >> 4)) * 11; 77 } 78 79 /* 80 * Finally: cut down the number of bits to a int value (and try to avoid 81 * losing bits) 82 */ 83 static inline unsigned long end_name_hash(unsigned long hash) 84 { 85 return (unsigned int) hash; 86 } 87 88 /* Compute the hash for a name string. */ 89 extern unsigned int full_name_hash(const unsigned char *, unsigned int); 90 91 /* 92 * Try to keep struct dentry aligned on 64 byte cachelines (this will 93 * give reasonable cacheline footprint with larger lines without the 94 * large memory footprint increase). 95 */ 96 #ifdef CONFIG_64BIT 97 # define DNAME_INLINE_LEN 32 /* 192 bytes */ 98 #else 99 # ifdef CONFIG_SMP 100 # define DNAME_INLINE_LEN 36 /* 128 bytes */ 101 # else 102 # define DNAME_INLINE_LEN 40 /* 128 bytes */ 103 # endif 104 #endif 105 106 #define d_lock d_lockref.lock 107 108 struct dentry { 109 /* RCU lookup touched fields */ 110 unsigned int d_flags; /* protected by d_lock */ 111 seqcount_t d_seq; /* per dentry seqlock */ 112 struct hlist_bl_node d_hash; /* lookup hash list */ 113 struct dentry *d_parent; /* parent directory */ 114 struct qstr d_name; 115 struct inode *d_inode; /* Where the name belongs to - NULL is 116 * negative */ 117 unsigned char d_iname[DNAME_INLINE_LEN]; /* small names */ 118 119 /* Ref lookup also touches following */ 120 struct lockref d_lockref; /* per-dentry lock and refcount */ 121 const struct dentry_operations *d_op; 122 struct super_block *d_sb; /* The root of the dentry tree */ 123 unsigned long d_time; /* used by d_revalidate */ 124 void *d_fsdata; /* fs-specific data */ 125 126 struct list_head d_lru; /* LRU list */ 127 struct list_head d_child; /* child of parent list */ 128 struct list_head d_subdirs; /* our children */ 129 /* 130 * d_alias and d_rcu can share memory 131 */ 132 union { 133 struct hlist_node d_alias; /* inode alias list */ 134 struct rcu_head d_rcu; 135 } d_u; 136 }; 137 138 /* 139 * dentry->d_lock spinlock nesting subclasses: 140 * 141 * 0: normal 142 * 1: nested 143 */ 144 enum dentry_d_lock_class 145 { 146 DENTRY_D_LOCK_NORMAL, /* implicitly used by plain spin_lock() APIs. */ 147 DENTRY_D_LOCK_NESTED 148 }; 149 150 struct dentry_operations { 151 int (*d_revalidate)(struct dentry *, unsigned int); 152 int (*d_weak_revalidate)(struct dentry *, unsigned int); 153 int (*d_hash)(const struct dentry *, struct qstr *); 154 int (*d_compare)(const struct dentry *, const struct dentry *, 155 unsigned int, const char *, const struct qstr *); 156 int (*d_delete)(const struct dentry *); 157 void (*d_release)(struct dentry *); 158 void (*d_prune)(struct dentry *); 159 void (*d_iput)(struct dentry *, struct inode *); 160 char *(*d_dname)(struct dentry *, char *, int); 161 struct vfsmount *(*d_automount)(struct path *); 162 int (*d_manage)(struct dentry *, bool); 163 struct inode *(*d_select_inode)(struct dentry *, unsigned); 164 } ____cacheline_aligned; 165 166 /* 167 * Locking rules for dentry_operations callbacks are to be found in 168 * Documentation/filesystems/Locking. Keep it updated! 169 * 170 * FUrther descriptions are found in Documentation/filesystems/vfs.txt. 171 * Keep it updated too! 172 */ 173 174 /* d_flags entries */ 175 #define DCACHE_OP_HASH 0x00000001 176 #define DCACHE_OP_COMPARE 0x00000002 177 #define DCACHE_OP_REVALIDATE 0x00000004 178 #define DCACHE_OP_DELETE 0x00000008 179 #define DCACHE_OP_PRUNE 0x00000010 180 181 #define DCACHE_DISCONNECTED 0x00000020 182 /* This dentry is possibly not currently connected to the dcache tree, in 183 * which case its parent will either be itself, or will have this flag as 184 * well. nfsd will not use a dentry with this bit set, but will first 185 * endeavour to clear the bit either by discovering that it is connected, 186 * or by performing lookup operations. Any filesystem which supports 187 * nfsd_operations MUST have a lookup function which, if it finds a 188 * directory inode with a DCACHE_DISCONNECTED dentry, will d_move that 189 * dentry into place and return that dentry rather than the passed one, 190 * typically using d_splice_alias. */ 191 192 #define DCACHE_REFERENCED 0x00000040 /* Recently used, don't discard. */ 193 #define DCACHE_RCUACCESS 0x00000080 /* Entry has ever been RCU-visible */ 194 195 #define DCACHE_CANT_MOUNT 0x00000100 196 #define DCACHE_GENOCIDE 0x00000200 197 #define DCACHE_SHRINK_LIST 0x00000400 198 199 #define DCACHE_OP_WEAK_REVALIDATE 0x00000800 200 201 #define DCACHE_NFSFS_RENAMED 0x00001000 202 /* this dentry has been "silly renamed" and has to be deleted on the last 203 * dput() */ 204 #define DCACHE_COOKIE 0x00002000 /* For use by dcookie subsystem */ 205 #define DCACHE_FSNOTIFY_PARENT_WATCHED 0x00004000 206 /* Parent inode is watched by some fsnotify listener */ 207 208 #define DCACHE_DENTRY_KILLED 0x00008000 209 210 #define DCACHE_MOUNTED 0x00010000 /* is a mountpoint */ 211 #define DCACHE_NEED_AUTOMOUNT 0x00020000 /* handle automount on this dir */ 212 #define DCACHE_MANAGE_TRANSIT 0x00040000 /* manage transit from this dirent */ 213 #define DCACHE_MANAGED_DENTRY \ 214 (DCACHE_MOUNTED|DCACHE_NEED_AUTOMOUNT|DCACHE_MANAGE_TRANSIT) 215 216 #define DCACHE_LRU_LIST 0x00080000 217 218 #define DCACHE_ENTRY_TYPE 0x00700000 219 #define DCACHE_MISS_TYPE 0x00000000 /* Negative dentry (maybe fallthru to nowhere) */ 220 #define DCACHE_WHITEOUT_TYPE 0x00100000 /* Whiteout dentry (stop pathwalk) */ 221 #define DCACHE_DIRECTORY_TYPE 0x00200000 /* Normal directory */ 222 #define DCACHE_AUTODIR_TYPE 0x00300000 /* Lookupless directory (presumed automount) */ 223 #define DCACHE_REGULAR_TYPE 0x00400000 /* Regular file type (or fallthru to such) */ 224 #define DCACHE_SPECIAL_TYPE 0x00500000 /* Other file type (or fallthru to such) */ 225 #define DCACHE_SYMLINK_TYPE 0x00600000 /* Symlink (or fallthru to such) */ 226 227 #define DCACHE_MAY_FREE 0x00800000 228 #define DCACHE_FALLTHRU 0x01000000 /* Fall through to lower layer */ 229 #define DCACHE_OP_SELECT_INODE 0x02000000 /* Unioned entry: dcache op selects inode */ 230 231 extern seqlock_t rename_lock; 232 233 /* 234 * These are the low-level FS interfaces to the dcache.. 235 */ 236 extern void d_instantiate(struct dentry *, struct inode *); 237 extern struct dentry * d_instantiate_unique(struct dentry *, struct inode *); 238 extern int d_instantiate_no_diralias(struct dentry *, struct inode *); 239 extern void __d_drop(struct dentry *dentry); 240 extern void d_drop(struct dentry *dentry); 241 extern void d_delete(struct dentry *); 242 extern void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op); 243 244 /* allocate/de-allocate */ 245 extern struct dentry * d_alloc(struct dentry *, const struct qstr *); 246 extern struct dentry * d_alloc_pseudo(struct super_block *, const struct qstr *); 247 extern struct dentry * d_splice_alias(struct inode *, struct dentry *); 248 extern struct dentry * d_add_ci(struct dentry *, struct inode *, struct qstr *); 249 extern struct dentry *d_find_any_alias(struct inode *inode); 250 extern struct dentry * d_obtain_alias(struct inode *); 251 extern struct dentry * d_obtain_root(struct inode *); 252 extern void shrink_dcache_sb(struct super_block *); 253 extern void shrink_dcache_parent(struct dentry *); 254 extern void shrink_dcache_for_umount(struct super_block *); 255 extern void d_invalidate(struct dentry *); 256 257 /* only used at mount-time */ 258 extern struct dentry * d_make_root(struct inode *); 259 260 /* <clickety>-<click> the ramfs-type tree */ 261 extern void d_genocide(struct dentry *); 262 263 extern void d_tmpfile(struct dentry *, struct inode *); 264 265 extern struct dentry *d_find_alias(struct inode *); 266 extern void d_prune_aliases(struct inode *); 267 268 /* test whether we have any submounts in a subdir tree */ 269 extern int have_submounts(struct dentry *); 270 271 /* 272 * This adds the entry to the hash queues. 273 */ 274 extern void d_rehash(struct dentry *); 275 276 /** 277 * d_add - add dentry to hash queues 278 * @entry: dentry to add 279 * @inode: The inode to attach to this dentry 280 * 281 * This adds the entry to the hash queues and initializes @inode. 282 * The entry was actually filled in earlier during d_alloc(). 283 */ 284 285 static inline void d_add(struct dentry *entry, struct inode *inode) 286 { 287 d_instantiate(entry, inode); 288 d_rehash(entry); 289 } 290 291 /** 292 * d_add_unique - add dentry to hash queues without aliasing 293 * @entry: dentry to add 294 * @inode: The inode to attach to this dentry 295 * 296 * This adds the entry to the hash queues and initializes @inode. 297 * The entry was actually filled in earlier during d_alloc(). 298 */ 299 static inline struct dentry *d_add_unique(struct dentry *entry, struct inode *inode) 300 { 301 struct dentry *res; 302 303 res = d_instantiate_unique(entry, inode); 304 d_rehash(res != NULL ? res : entry); 305 return res; 306 } 307 308 extern void dentry_update_name_case(struct dentry *, struct qstr *); 309 310 /* used for rename() and baskets */ 311 extern void d_move(struct dentry *, struct dentry *); 312 extern void d_exchange(struct dentry *, struct dentry *); 313 extern struct dentry *d_ancestor(struct dentry *, struct dentry *); 314 315 /* appendix may either be NULL or be used for transname suffixes */ 316 extern struct dentry *d_lookup(const struct dentry *, const struct qstr *); 317 extern struct dentry *d_hash_and_lookup(struct dentry *, struct qstr *); 318 extern struct dentry *__d_lookup(const struct dentry *, const struct qstr *); 319 extern struct dentry *__d_lookup_rcu(const struct dentry *parent, 320 const struct qstr *name, unsigned *seq); 321 322 static inline unsigned d_count(const struct dentry *dentry) 323 { 324 return dentry->d_lockref.count; 325 } 326 327 /* 328 * helper function for dentry_operations.d_dname() members 329 */ 330 extern __printf(4, 5) 331 char *dynamic_dname(struct dentry *, char *, int, const char *, ...); 332 extern char *simple_dname(struct dentry *, char *, int); 333 334 extern char *__d_path(const struct path *, const struct path *, char *, int); 335 extern char *d_absolute_path(const struct path *, char *, int); 336 extern char *d_path(const struct path *, char *, int); 337 extern char *dentry_path_raw(struct dentry *, char *, int); 338 extern char *dentry_path(struct dentry *, char *, int); 339 340 /* Allocation counts.. */ 341 342 /** 343 * dget, dget_dlock - get a reference to a dentry 344 * @dentry: dentry to get a reference to 345 * 346 * Given a dentry or %NULL pointer increment the reference count 347 * if appropriate and return the dentry. A dentry will not be 348 * destroyed when it has references. 349 */ 350 static inline struct dentry *dget_dlock(struct dentry *dentry) 351 { 352 if (dentry) 353 dentry->d_lockref.count++; 354 return dentry; 355 } 356 357 static inline struct dentry *dget(struct dentry *dentry) 358 { 359 if (dentry) 360 lockref_get(&dentry->d_lockref); 361 return dentry; 362 } 363 364 extern struct dentry *dget_parent(struct dentry *dentry); 365 366 /** 367 * d_unhashed - is dentry hashed 368 * @dentry: entry to check 369 * 370 * Returns true if the dentry passed is not currently hashed. 371 */ 372 373 static inline int d_unhashed(const struct dentry *dentry) 374 { 375 return hlist_bl_unhashed(&dentry->d_hash); 376 } 377 378 static inline int d_unlinked(const struct dentry *dentry) 379 { 380 return d_unhashed(dentry) && !IS_ROOT(dentry); 381 } 382 383 static inline int cant_mount(const struct dentry *dentry) 384 { 385 return (dentry->d_flags & DCACHE_CANT_MOUNT); 386 } 387 388 static inline void dont_mount(struct dentry *dentry) 389 { 390 spin_lock(&dentry->d_lock); 391 dentry->d_flags |= DCACHE_CANT_MOUNT; 392 spin_unlock(&dentry->d_lock); 393 } 394 395 extern void dput(struct dentry *); 396 397 static inline bool d_managed(const struct dentry *dentry) 398 { 399 return dentry->d_flags & DCACHE_MANAGED_DENTRY; 400 } 401 402 static inline bool d_mountpoint(const struct dentry *dentry) 403 { 404 return dentry->d_flags & DCACHE_MOUNTED; 405 } 406 407 /* 408 * Directory cache entry type accessor functions. 409 */ 410 static inline unsigned __d_entry_type(const struct dentry *dentry) 411 { 412 unsigned type = READ_ONCE(dentry->d_flags); 413 smp_rmb(); 414 return type & DCACHE_ENTRY_TYPE; 415 } 416 417 static inline bool d_is_miss(const struct dentry *dentry) 418 { 419 return __d_entry_type(dentry) == DCACHE_MISS_TYPE; 420 } 421 422 static inline bool d_is_whiteout(const struct dentry *dentry) 423 { 424 return __d_entry_type(dentry) == DCACHE_WHITEOUT_TYPE; 425 } 426 427 static inline bool d_can_lookup(const struct dentry *dentry) 428 { 429 return __d_entry_type(dentry) == DCACHE_DIRECTORY_TYPE; 430 } 431 432 static inline bool d_is_autodir(const struct dentry *dentry) 433 { 434 return __d_entry_type(dentry) == DCACHE_AUTODIR_TYPE; 435 } 436 437 static inline bool d_is_dir(const struct dentry *dentry) 438 { 439 return d_can_lookup(dentry) || d_is_autodir(dentry); 440 } 441 442 static inline bool d_is_symlink(const struct dentry *dentry) 443 { 444 return __d_entry_type(dentry) == DCACHE_SYMLINK_TYPE; 445 } 446 447 static inline bool d_is_reg(const struct dentry *dentry) 448 { 449 return __d_entry_type(dentry) == DCACHE_REGULAR_TYPE; 450 } 451 452 static inline bool d_is_special(const struct dentry *dentry) 453 { 454 return __d_entry_type(dentry) == DCACHE_SPECIAL_TYPE; 455 } 456 457 static inline bool d_is_file(const struct dentry *dentry) 458 { 459 return d_is_reg(dentry) || d_is_special(dentry); 460 } 461 462 static inline bool d_is_negative(const struct dentry *dentry) 463 { 464 // TODO: check d_is_whiteout(dentry) also. 465 return d_is_miss(dentry); 466 } 467 468 static inline bool d_is_positive(const struct dentry *dentry) 469 { 470 return !d_is_negative(dentry); 471 } 472 473 /** 474 * d_really_is_negative - Determine if a dentry is really negative (ignoring fallthroughs) 475 * @dentry: The dentry in question 476 * 477 * Returns true if the dentry represents either an absent name or a name that 478 * doesn't map to an inode (ie. ->d_inode is NULL). The dentry could represent 479 * a true miss, a whiteout that isn't represented by a 0,0 chardev or a 480 * fallthrough marker in an opaque directory. 481 * 482 * Note! (1) This should be used *only* by a filesystem to examine its own 483 * dentries. It should not be used to look at some other filesystem's 484 * dentries. (2) It should also be used in combination with d_inode() to get 485 * the inode. (3) The dentry may have something attached to ->d_lower and the 486 * type field of the flags may be set to something other than miss or whiteout. 487 */ 488 static inline bool d_really_is_negative(const struct dentry *dentry) 489 { 490 return dentry->d_inode == NULL; 491 } 492 493 /** 494 * d_really_is_positive - Determine if a dentry is really positive (ignoring fallthroughs) 495 * @dentry: The dentry in question 496 * 497 * Returns true if the dentry represents a name that maps to an inode 498 * (ie. ->d_inode is not NULL). The dentry might still represent a whiteout if 499 * that is represented on medium as a 0,0 chardev. 500 * 501 * Note! (1) This should be used *only* by a filesystem to examine its own 502 * dentries. It should not be used to look at some other filesystem's 503 * dentries. (2) It should also be used in combination with d_inode() to get 504 * the inode. 505 */ 506 static inline bool d_really_is_positive(const struct dentry *dentry) 507 { 508 return dentry->d_inode != NULL; 509 } 510 511 static inline int simple_positive(struct dentry *dentry) 512 { 513 return d_really_is_positive(dentry) && !d_unhashed(dentry); 514 } 515 516 extern void d_set_fallthru(struct dentry *dentry); 517 518 static inline bool d_is_fallthru(const struct dentry *dentry) 519 { 520 return dentry->d_flags & DCACHE_FALLTHRU; 521 } 522 523 524 extern int sysctl_vfs_cache_pressure; 525 526 static inline unsigned long vfs_pressure_ratio(unsigned long val) 527 { 528 return mult_frac(val, sysctl_vfs_cache_pressure, 100); 529 } 530 531 /** 532 * d_inode - Get the actual inode of this dentry 533 * @dentry: The dentry to query 534 * 535 * This is the helper normal filesystems should use to get at their own inodes 536 * in their own dentries and ignore the layering superimposed upon them. 537 */ 538 static inline struct inode *d_inode(const struct dentry *dentry) 539 { 540 return dentry->d_inode; 541 } 542 543 /** 544 * d_inode_rcu - Get the actual inode of this dentry with ACCESS_ONCE() 545 * @dentry: The dentry to query 546 * 547 * This is the helper normal filesystems should use to get at their own inodes 548 * in their own dentries and ignore the layering superimposed upon them. 549 */ 550 static inline struct inode *d_inode_rcu(const struct dentry *dentry) 551 { 552 return ACCESS_ONCE(dentry->d_inode); 553 } 554 555 /** 556 * d_backing_inode - Get upper or lower inode we should be using 557 * @upper: The upper layer 558 * 559 * This is the helper that should be used to get at the inode that will be used 560 * if this dentry were to be opened as a file. The inode may be on the upper 561 * dentry or it may be on a lower dentry pinned by the upper. 562 * 563 * Normal filesystems should not use this to access their own inodes. 564 */ 565 static inline struct inode *d_backing_inode(const struct dentry *upper) 566 { 567 struct inode *inode = upper->d_inode; 568 569 return inode; 570 } 571 572 /** 573 * d_backing_dentry - Get upper or lower dentry we should be using 574 * @upper: The upper layer 575 * 576 * This is the helper that should be used to get the dentry of the inode that 577 * will be used if this dentry were opened as a file. It may be the upper 578 * dentry or it may be a lower dentry pinned by the upper. 579 * 580 * Normal filesystems should not use this to access their own dentries. 581 */ 582 static inline struct dentry *d_backing_dentry(struct dentry *upper) 583 { 584 return upper; 585 } 586 587 #endif /* __LINUX_DCACHE_H */ 588