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 struct dentry *(*d_real)(struct dentry *, struct inode *); 165 } ____cacheline_aligned; 166 167 /* 168 * Locking rules for dentry_operations callbacks are to be found in 169 * Documentation/filesystems/Locking. Keep it updated! 170 * 171 * FUrther descriptions are found in Documentation/filesystems/vfs.txt. 172 * Keep it updated too! 173 */ 174 175 /* d_flags entries */ 176 #define DCACHE_OP_HASH 0x00000001 177 #define DCACHE_OP_COMPARE 0x00000002 178 #define DCACHE_OP_REVALIDATE 0x00000004 179 #define DCACHE_OP_DELETE 0x00000008 180 #define DCACHE_OP_PRUNE 0x00000010 181 182 #define DCACHE_DISCONNECTED 0x00000020 183 /* This dentry is possibly not currently connected to the dcache tree, in 184 * which case its parent will either be itself, or will have this flag as 185 * well. nfsd will not use a dentry with this bit set, but will first 186 * endeavour to clear the bit either by discovering that it is connected, 187 * or by performing lookup operations. Any filesystem which supports 188 * nfsd_operations MUST have a lookup function which, if it finds a 189 * directory inode with a DCACHE_DISCONNECTED dentry, will d_move that 190 * dentry into place and return that dentry rather than the passed one, 191 * typically using d_splice_alias. */ 192 193 #define DCACHE_REFERENCED 0x00000040 /* Recently used, don't discard. */ 194 #define DCACHE_RCUACCESS 0x00000080 /* Entry has ever been RCU-visible */ 195 196 #define DCACHE_CANT_MOUNT 0x00000100 197 #define DCACHE_GENOCIDE 0x00000200 198 #define DCACHE_SHRINK_LIST 0x00000400 199 200 #define DCACHE_OP_WEAK_REVALIDATE 0x00000800 201 202 #define DCACHE_NFSFS_RENAMED 0x00001000 203 /* this dentry has been "silly renamed" and has to be deleted on the last 204 * dput() */ 205 #define DCACHE_COOKIE 0x00002000 /* For use by dcookie subsystem */ 206 #define DCACHE_FSNOTIFY_PARENT_WATCHED 0x00004000 207 /* Parent inode is watched by some fsnotify listener */ 208 209 #define DCACHE_DENTRY_KILLED 0x00008000 210 211 #define DCACHE_MOUNTED 0x00010000 /* is a mountpoint */ 212 #define DCACHE_NEED_AUTOMOUNT 0x00020000 /* handle automount on this dir */ 213 #define DCACHE_MANAGE_TRANSIT 0x00040000 /* manage transit from this dirent */ 214 #define DCACHE_MANAGED_DENTRY \ 215 (DCACHE_MOUNTED|DCACHE_NEED_AUTOMOUNT|DCACHE_MANAGE_TRANSIT) 216 217 #define DCACHE_LRU_LIST 0x00080000 218 219 #define DCACHE_ENTRY_TYPE 0x00700000 220 #define DCACHE_MISS_TYPE 0x00000000 /* Negative dentry (maybe fallthru to nowhere) */ 221 #define DCACHE_WHITEOUT_TYPE 0x00100000 /* Whiteout dentry (stop pathwalk) */ 222 #define DCACHE_DIRECTORY_TYPE 0x00200000 /* Normal directory */ 223 #define DCACHE_AUTODIR_TYPE 0x00300000 /* Lookupless directory (presumed automount) */ 224 #define DCACHE_REGULAR_TYPE 0x00400000 /* Regular file type (or fallthru to such) */ 225 #define DCACHE_SPECIAL_TYPE 0x00500000 /* Other file type (or fallthru to such) */ 226 #define DCACHE_SYMLINK_TYPE 0x00600000 /* Symlink (or fallthru to such) */ 227 228 #define DCACHE_MAY_FREE 0x00800000 229 #define DCACHE_FALLTHRU 0x01000000 /* Fall through to lower layer */ 230 #define DCACHE_OP_SELECT_INODE 0x02000000 /* Unioned entry: dcache op selects inode */ 231 232 #define DCACHE_ENCRYPTED_WITH_KEY 0x04000000 /* dir is encrypted with a valid key */ 233 #define DCACHE_OP_REAL 0x08000000 234 235 extern seqlock_t rename_lock; 236 237 /* 238 * These are the low-level FS interfaces to the dcache.. 239 */ 240 extern void d_instantiate(struct dentry *, struct inode *); 241 extern struct dentry * d_instantiate_unique(struct dentry *, struct inode *); 242 extern int d_instantiate_no_diralias(struct dentry *, struct inode *); 243 extern void __d_drop(struct dentry *dentry); 244 extern void d_drop(struct dentry *dentry); 245 extern void d_delete(struct dentry *); 246 extern void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op); 247 248 /* allocate/de-allocate */ 249 extern struct dentry * d_alloc(struct dentry *, const struct qstr *); 250 extern struct dentry * d_alloc_pseudo(struct super_block *, const struct qstr *); 251 extern struct dentry * d_splice_alias(struct inode *, struct dentry *); 252 extern struct dentry * d_add_ci(struct dentry *, struct inode *, struct qstr *); 253 extern struct dentry * d_exact_alias(struct dentry *, struct inode *); 254 extern struct dentry *d_find_any_alias(struct inode *inode); 255 extern struct dentry * d_obtain_alias(struct inode *); 256 extern struct dentry * d_obtain_root(struct inode *); 257 extern void shrink_dcache_sb(struct super_block *); 258 extern void shrink_dcache_parent(struct dentry *); 259 extern void shrink_dcache_for_umount(struct super_block *); 260 extern void d_invalidate(struct dentry *); 261 262 /* only used at mount-time */ 263 extern struct dentry * d_make_root(struct inode *); 264 265 /* <clickety>-<click> the ramfs-type tree */ 266 extern void d_genocide(struct dentry *); 267 268 extern void d_tmpfile(struct dentry *, struct inode *); 269 270 extern struct dentry *d_find_alias(struct inode *); 271 extern void d_prune_aliases(struct inode *); 272 273 /* test whether we have any submounts in a subdir tree */ 274 extern int have_submounts(struct dentry *); 275 276 /* 277 * This adds the entry to the hash queues. 278 */ 279 extern void d_rehash(struct dentry *); 280 281 extern void d_add(struct dentry *, struct inode *); 282 283 extern void dentry_update_name_case(struct dentry *, struct qstr *); 284 285 /* used for rename() and baskets */ 286 extern void d_move(struct dentry *, struct dentry *); 287 extern void d_exchange(struct dentry *, struct dentry *); 288 extern struct dentry *d_ancestor(struct dentry *, struct dentry *); 289 290 /* appendix may either be NULL or be used for transname suffixes */ 291 extern struct dentry *d_lookup(const struct dentry *, const struct qstr *); 292 extern struct dentry *d_hash_and_lookup(struct dentry *, struct qstr *); 293 extern struct dentry *__d_lookup(const struct dentry *, const struct qstr *); 294 extern struct dentry *__d_lookup_rcu(const struct dentry *parent, 295 const struct qstr *name, unsigned *seq); 296 297 static inline unsigned d_count(const struct dentry *dentry) 298 { 299 return dentry->d_lockref.count; 300 } 301 302 /* 303 * helper function for dentry_operations.d_dname() members 304 */ 305 extern __printf(4, 5) 306 char *dynamic_dname(struct dentry *, char *, int, const char *, ...); 307 extern char *simple_dname(struct dentry *, char *, int); 308 309 extern char *__d_path(const struct path *, const struct path *, char *, int); 310 extern char *d_absolute_path(const struct path *, char *, int); 311 extern char *d_path(const struct path *, char *, int); 312 extern char *dentry_path_raw(struct dentry *, char *, int); 313 extern char *dentry_path(struct dentry *, char *, int); 314 315 /* Allocation counts.. */ 316 317 /** 318 * dget, dget_dlock - get a reference to a dentry 319 * @dentry: dentry to get a reference to 320 * 321 * Given a dentry or %NULL pointer increment the reference count 322 * if appropriate and return the dentry. A dentry will not be 323 * destroyed when it has references. 324 */ 325 static inline struct dentry *dget_dlock(struct dentry *dentry) 326 { 327 if (dentry) 328 dentry->d_lockref.count++; 329 return dentry; 330 } 331 332 static inline struct dentry *dget(struct dentry *dentry) 333 { 334 if (dentry) 335 lockref_get(&dentry->d_lockref); 336 return dentry; 337 } 338 339 extern struct dentry *dget_parent(struct dentry *dentry); 340 341 /** 342 * d_unhashed - is dentry hashed 343 * @dentry: entry to check 344 * 345 * Returns true if the dentry passed is not currently hashed. 346 */ 347 348 static inline int d_unhashed(const struct dentry *dentry) 349 { 350 return hlist_bl_unhashed(&dentry->d_hash); 351 } 352 353 static inline int d_unlinked(const struct dentry *dentry) 354 { 355 return d_unhashed(dentry) && !IS_ROOT(dentry); 356 } 357 358 static inline int cant_mount(const struct dentry *dentry) 359 { 360 return (dentry->d_flags & DCACHE_CANT_MOUNT); 361 } 362 363 static inline void dont_mount(struct dentry *dentry) 364 { 365 spin_lock(&dentry->d_lock); 366 dentry->d_flags |= DCACHE_CANT_MOUNT; 367 spin_unlock(&dentry->d_lock); 368 } 369 370 extern void dput(struct dentry *); 371 372 static inline bool d_managed(const struct dentry *dentry) 373 { 374 return dentry->d_flags & DCACHE_MANAGED_DENTRY; 375 } 376 377 static inline bool d_mountpoint(const struct dentry *dentry) 378 { 379 return dentry->d_flags & DCACHE_MOUNTED; 380 } 381 382 /* 383 * Directory cache entry type accessor functions. 384 */ 385 static inline unsigned __d_entry_type(const struct dentry *dentry) 386 { 387 return dentry->d_flags & DCACHE_ENTRY_TYPE; 388 } 389 390 static inline bool d_is_miss(const struct dentry *dentry) 391 { 392 return __d_entry_type(dentry) == DCACHE_MISS_TYPE; 393 } 394 395 static inline bool d_is_whiteout(const struct dentry *dentry) 396 { 397 return __d_entry_type(dentry) == DCACHE_WHITEOUT_TYPE; 398 } 399 400 static inline bool d_can_lookup(const struct dentry *dentry) 401 { 402 return __d_entry_type(dentry) == DCACHE_DIRECTORY_TYPE; 403 } 404 405 static inline bool d_is_autodir(const struct dentry *dentry) 406 { 407 return __d_entry_type(dentry) == DCACHE_AUTODIR_TYPE; 408 } 409 410 static inline bool d_is_dir(const struct dentry *dentry) 411 { 412 return d_can_lookup(dentry) || d_is_autodir(dentry); 413 } 414 415 static inline bool d_is_symlink(const struct dentry *dentry) 416 { 417 return __d_entry_type(dentry) == DCACHE_SYMLINK_TYPE; 418 } 419 420 static inline bool d_is_reg(const struct dentry *dentry) 421 { 422 return __d_entry_type(dentry) == DCACHE_REGULAR_TYPE; 423 } 424 425 static inline bool d_is_special(const struct dentry *dentry) 426 { 427 return __d_entry_type(dentry) == DCACHE_SPECIAL_TYPE; 428 } 429 430 static inline bool d_is_file(const struct dentry *dentry) 431 { 432 return d_is_reg(dentry) || d_is_special(dentry); 433 } 434 435 static inline bool d_is_negative(const struct dentry *dentry) 436 { 437 // TODO: check d_is_whiteout(dentry) also. 438 return d_is_miss(dentry); 439 } 440 441 static inline bool d_is_positive(const struct dentry *dentry) 442 { 443 return !d_is_negative(dentry); 444 } 445 446 /** 447 * d_really_is_negative - Determine if a dentry is really negative (ignoring fallthroughs) 448 * @dentry: The dentry in question 449 * 450 * Returns true if the dentry represents either an absent name or a name that 451 * doesn't map to an inode (ie. ->d_inode is NULL). The dentry could represent 452 * a true miss, a whiteout that isn't represented by a 0,0 chardev or a 453 * fallthrough marker in an opaque directory. 454 * 455 * Note! (1) This should be used *only* by a filesystem to examine its own 456 * dentries. It should not be used to look at some other filesystem's 457 * dentries. (2) It should also be used in combination with d_inode() to get 458 * the inode. (3) The dentry may have something attached to ->d_lower and the 459 * type field of the flags may be set to something other than miss or whiteout. 460 */ 461 static inline bool d_really_is_negative(const struct dentry *dentry) 462 { 463 return dentry->d_inode == NULL; 464 } 465 466 /** 467 * d_really_is_positive - Determine if a dentry is really positive (ignoring fallthroughs) 468 * @dentry: The dentry in question 469 * 470 * Returns true if the dentry represents a name that maps to an inode 471 * (ie. ->d_inode is not NULL). The dentry might still represent a whiteout if 472 * that is represented on medium as a 0,0 chardev. 473 * 474 * Note! (1) This should be used *only* by a filesystem to examine its own 475 * dentries. It should not be used to look at some other filesystem's 476 * dentries. (2) It should also be used in combination with d_inode() to get 477 * the inode. 478 */ 479 static inline bool d_really_is_positive(const struct dentry *dentry) 480 { 481 return dentry->d_inode != NULL; 482 } 483 484 static inline int simple_positive(struct dentry *dentry) 485 { 486 return d_really_is_positive(dentry) && !d_unhashed(dentry); 487 } 488 489 extern void d_set_fallthru(struct dentry *dentry); 490 491 static inline bool d_is_fallthru(const struct dentry *dentry) 492 { 493 return dentry->d_flags & DCACHE_FALLTHRU; 494 } 495 496 497 extern int sysctl_vfs_cache_pressure; 498 499 static inline unsigned long vfs_pressure_ratio(unsigned long val) 500 { 501 return mult_frac(val, sysctl_vfs_cache_pressure, 100); 502 } 503 504 /** 505 * d_inode - Get the actual inode of this dentry 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(const struct dentry *dentry) 512 { 513 return dentry->d_inode; 514 } 515 516 /** 517 * d_inode_rcu - Get the actual inode of this dentry with ACCESS_ONCE() 518 * @dentry: The dentry to query 519 * 520 * This is the helper normal filesystems should use to get at their own inodes 521 * in their own dentries and ignore the layering superimposed upon them. 522 */ 523 static inline struct inode *d_inode_rcu(const struct dentry *dentry) 524 { 525 return ACCESS_ONCE(dentry->d_inode); 526 } 527 528 /** 529 * d_backing_inode - Get upper or lower inode we should be using 530 * @upper: The upper layer 531 * 532 * This is the helper that should be used to get at the inode that will be used 533 * if this dentry were to be opened as a file. The inode may be on the upper 534 * dentry or it may be on a lower dentry pinned by the upper. 535 * 536 * Normal filesystems should not use this to access their own inodes. 537 */ 538 static inline struct inode *d_backing_inode(const struct dentry *upper) 539 { 540 struct inode *inode = upper->d_inode; 541 542 return inode; 543 } 544 545 /** 546 * d_backing_dentry - Get upper or lower dentry we should be using 547 * @upper: The upper layer 548 * 549 * This is the helper that should be used to get the dentry of the inode that 550 * will be used if this dentry were opened as a file. It may be the upper 551 * dentry or it may be a lower dentry pinned by the upper. 552 * 553 * Normal filesystems should not use this to access their own dentries. 554 */ 555 static inline struct dentry *d_backing_dentry(struct dentry *upper) 556 { 557 return upper; 558 } 559 560 static inline struct dentry *d_real(struct dentry *dentry) 561 { 562 if (unlikely(dentry->d_flags & DCACHE_OP_REAL)) 563 return dentry->d_op->d_real(dentry, NULL); 564 else 565 return dentry; 566 } 567 568 #endif /* __LINUX_DCACHE_H */ 569