1 #ifndef _LINUX_PAGEMAP_H 2 #define _LINUX_PAGEMAP_H 3 4 /* 5 * Copyright 1995 Linus Torvalds 6 */ 7 #include <linux/mm.h> 8 #include <linux/fs.h> 9 #include <linux/list.h> 10 #include <linux/highmem.h> 11 #include <linux/compiler.h> 12 #include <asm/uaccess.h> 13 #include <linux/gfp.h> 14 #include <linux/bitops.h> 15 #include <linux/hardirq.h> /* for in_interrupt() */ 16 #include <linux/hugetlb_inline.h> 17 18 /* 19 * Bits in mapping->flags. The lower __GFP_BITS_SHIFT bits are the page 20 * allocation mode flags. 21 */ 22 enum mapping_flags { 23 AS_EIO = __GFP_BITS_SHIFT + 0, /* IO error on async write */ 24 AS_ENOSPC = __GFP_BITS_SHIFT + 1, /* ENOSPC on async write */ 25 AS_MM_ALL_LOCKS = __GFP_BITS_SHIFT + 2, /* under mm_take_all_locks() */ 26 AS_UNEVICTABLE = __GFP_BITS_SHIFT + 3, /* e.g., ramdisk, SHM_LOCK */ 27 AS_BALLOON_MAP = __GFP_BITS_SHIFT + 4, /* balloon page special map */ 28 }; 29 30 static inline void mapping_set_error(struct address_space *mapping, int error) 31 { 32 if (unlikely(error)) { 33 if (error == -ENOSPC) 34 set_bit(AS_ENOSPC, &mapping->flags); 35 else 36 set_bit(AS_EIO, &mapping->flags); 37 } 38 } 39 40 static inline void mapping_set_unevictable(struct address_space *mapping) 41 { 42 set_bit(AS_UNEVICTABLE, &mapping->flags); 43 } 44 45 static inline void mapping_clear_unevictable(struct address_space *mapping) 46 { 47 clear_bit(AS_UNEVICTABLE, &mapping->flags); 48 } 49 50 static inline int mapping_unevictable(struct address_space *mapping) 51 { 52 if (mapping) 53 return test_bit(AS_UNEVICTABLE, &mapping->flags); 54 return !!mapping; 55 } 56 57 static inline void mapping_set_balloon(struct address_space *mapping) 58 { 59 set_bit(AS_BALLOON_MAP, &mapping->flags); 60 } 61 62 static inline void mapping_clear_balloon(struct address_space *mapping) 63 { 64 clear_bit(AS_BALLOON_MAP, &mapping->flags); 65 } 66 67 static inline int mapping_balloon(struct address_space *mapping) 68 { 69 return mapping && test_bit(AS_BALLOON_MAP, &mapping->flags); 70 } 71 72 static inline gfp_t mapping_gfp_mask(struct address_space * mapping) 73 { 74 return (__force gfp_t)mapping->flags & __GFP_BITS_MASK; 75 } 76 77 /* 78 * This is non-atomic. Only to be used before the mapping is activated. 79 * Probably needs a barrier... 80 */ 81 static inline void mapping_set_gfp_mask(struct address_space *m, gfp_t mask) 82 { 83 m->flags = (m->flags & ~(__force unsigned long)__GFP_BITS_MASK) | 84 (__force unsigned long)mask; 85 } 86 87 /* 88 * The page cache can done in larger chunks than 89 * one page, because it allows for more efficient 90 * throughput (it can then be mapped into user 91 * space in smaller chunks for same flexibility). 92 * 93 * Or rather, it _will_ be done in larger chunks. 94 */ 95 #define PAGE_CACHE_SHIFT PAGE_SHIFT 96 #define PAGE_CACHE_SIZE PAGE_SIZE 97 #define PAGE_CACHE_MASK PAGE_MASK 98 #define PAGE_CACHE_ALIGN(addr) (((addr)+PAGE_CACHE_SIZE-1)&PAGE_CACHE_MASK) 99 100 #define page_cache_get(page) get_page(page) 101 #define page_cache_release(page) put_page(page) 102 void release_pages(struct page **pages, int nr, int cold); 103 104 /* 105 * speculatively take a reference to a page. 106 * If the page is free (_count == 0), then _count is untouched, and 0 107 * is returned. Otherwise, _count is incremented by 1 and 1 is returned. 108 * 109 * This function must be called inside the same rcu_read_lock() section as has 110 * been used to lookup the page in the pagecache radix-tree (or page table): 111 * this allows allocators to use a synchronize_rcu() to stabilize _count. 112 * 113 * Unless an RCU grace period has passed, the count of all pages coming out 114 * of the allocator must be considered unstable. page_count may return higher 115 * than expected, and put_page must be able to do the right thing when the 116 * page has been finished with, no matter what it is subsequently allocated 117 * for (because put_page is what is used here to drop an invalid speculative 118 * reference). 119 * 120 * This is the interesting part of the lockless pagecache (and lockless 121 * get_user_pages) locking protocol, where the lookup-side (eg. find_get_page) 122 * has the following pattern: 123 * 1. find page in radix tree 124 * 2. conditionally increment refcount 125 * 3. check the page is still in pagecache (if no, goto 1) 126 * 127 * Remove-side that cares about stability of _count (eg. reclaim) has the 128 * following (with tree_lock held for write): 129 * A. atomically check refcount is correct and set it to 0 (atomic_cmpxchg) 130 * B. remove page from pagecache 131 * C. free the page 132 * 133 * There are 2 critical interleavings that matter: 134 * - 2 runs before A: in this case, A sees elevated refcount and bails out 135 * - A runs before 2: in this case, 2 sees zero refcount and retries; 136 * subsequently, B will complete and 1 will find no page, causing the 137 * lookup to return NULL. 138 * 139 * It is possible that between 1 and 2, the page is removed then the exact same 140 * page is inserted into the same position in pagecache. That's OK: the 141 * old find_get_page using tree_lock could equally have run before or after 142 * such a re-insertion, depending on order that locks are granted. 143 * 144 * Lookups racing against pagecache insertion isn't a big problem: either 1 145 * will find the page or it will not. Likewise, the old find_get_page could run 146 * either before the insertion or afterwards, depending on timing. 147 */ 148 static inline int page_cache_get_speculative(struct page *page) 149 { 150 VM_BUG_ON(in_interrupt()); 151 152 #ifdef CONFIG_TINY_RCU 153 # ifdef CONFIG_PREEMPT_COUNT 154 VM_BUG_ON(!in_atomic()); 155 # endif 156 /* 157 * Preempt must be disabled here - we rely on rcu_read_lock doing 158 * this for us. 159 * 160 * Pagecache won't be truncated from interrupt context, so if we have 161 * found a page in the radix tree here, we have pinned its refcount by 162 * disabling preempt, and hence no need for the "speculative get" that 163 * SMP requires. 164 */ 165 VM_BUG_ON(page_count(page) == 0); 166 atomic_inc(&page->_count); 167 168 #else 169 if (unlikely(!get_page_unless_zero(page))) { 170 /* 171 * Either the page has been freed, or will be freed. 172 * In either case, retry here and the caller should 173 * do the right thing (see comments above). 174 */ 175 return 0; 176 } 177 #endif 178 VM_BUG_ON(PageTail(page)); 179 180 return 1; 181 } 182 183 /* 184 * Same as above, but add instead of inc (could just be merged) 185 */ 186 static inline int page_cache_add_speculative(struct page *page, int count) 187 { 188 VM_BUG_ON(in_interrupt()); 189 190 #if !defined(CONFIG_SMP) && defined(CONFIG_TREE_RCU) 191 # ifdef CONFIG_PREEMPT_COUNT 192 VM_BUG_ON(!in_atomic()); 193 # endif 194 VM_BUG_ON(page_count(page) == 0); 195 atomic_add(count, &page->_count); 196 197 #else 198 if (unlikely(!atomic_add_unless(&page->_count, count, 0))) 199 return 0; 200 #endif 201 VM_BUG_ON(PageCompound(page) && page != compound_head(page)); 202 203 return 1; 204 } 205 206 static inline int page_freeze_refs(struct page *page, int count) 207 { 208 return likely(atomic_cmpxchg(&page->_count, count, 0) == count); 209 } 210 211 static inline void page_unfreeze_refs(struct page *page, int count) 212 { 213 VM_BUG_ON(page_count(page) != 0); 214 VM_BUG_ON(count == 0); 215 216 atomic_set(&page->_count, count); 217 } 218 219 #ifdef CONFIG_NUMA 220 extern struct page *__page_cache_alloc(gfp_t gfp); 221 #else 222 static inline struct page *__page_cache_alloc(gfp_t gfp) 223 { 224 return alloc_pages(gfp, 0); 225 } 226 #endif 227 228 static inline struct page *page_cache_alloc(struct address_space *x) 229 { 230 return __page_cache_alloc(mapping_gfp_mask(x)); 231 } 232 233 static inline struct page *page_cache_alloc_cold(struct address_space *x) 234 { 235 return __page_cache_alloc(mapping_gfp_mask(x)|__GFP_COLD); 236 } 237 238 static inline struct page *page_cache_alloc_readahead(struct address_space *x) 239 { 240 return __page_cache_alloc(mapping_gfp_mask(x) | 241 __GFP_COLD | __GFP_NORETRY | __GFP_NOWARN); 242 } 243 244 typedef int filler_t(void *, struct page *); 245 246 extern struct page * find_get_page(struct address_space *mapping, 247 pgoff_t index); 248 extern struct page * find_lock_page(struct address_space *mapping, 249 pgoff_t index); 250 extern struct page * find_or_create_page(struct address_space *mapping, 251 pgoff_t index, gfp_t gfp_mask); 252 unsigned find_get_pages(struct address_space *mapping, pgoff_t start, 253 unsigned int nr_pages, struct page **pages); 254 unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t start, 255 unsigned int nr_pages, struct page **pages); 256 unsigned find_get_pages_tag(struct address_space *mapping, pgoff_t *index, 257 int tag, unsigned int nr_pages, struct page **pages); 258 259 struct page *grab_cache_page_write_begin(struct address_space *mapping, 260 pgoff_t index, unsigned flags); 261 262 /* 263 * Returns locked page at given index in given cache, creating it if needed. 264 */ 265 static inline struct page *grab_cache_page(struct address_space *mapping, 266 pgoff_t index) 267 { 268 return find_or_create_page(mapping, index, mapping_gfp_mask(mapping)); 269 } 270 271 extern struct page * grab_cache_page_nowait(struct address_space *mapping, 272 pgoff_t index); 273 extern struct page * read_cache_page_async(struct address_space *mapping, 274 pgoff_t index, filler_t *filler, void *data); 275 extern struct page * read_cache_page(struct address_space *mapping, 276 pgoff_t index, filler_t *filler, void *data); 277 extern struct page * read_cache_page_gfp(struct address_space *mapping, 278 pgoff_t index, gfp_t gfp_mask); 279 extern int read_cache_pages(struct address_space *mapping, 280 struct list_head *pages, filler_t *filler, void *data); 281 282 static inline struct page *read_mapping_page_async( 283 struct address_space *mapping, 284 pgoff_t index, void *data) 285 { 286 filler_t *filler = (filler_t *)mapping->a_ops->readpage; 287 return read_cache_page_async(mapping, index, filler, data); 288 } 289 290 static inline struct page *read_mapping_page(struct address_space *mapping, 291 pgoff_t index, void *data) 292 { 293 filler_t *filler = (filler_t *)mapping->a_ops->readpage; 294 return read_cache_page(mapping, index, filler, data); 295 } 296 297 /* 298 * Return byte-offset into filesystem object for page. 299 */ 300 static inline loff_t page_offset(struct page *page) 301 { 302 return ((loff_t)page->index) << PAGE_CACHE_SHIFT; 303 } 304 305 static inline loff_t page_file_offset(struct page *page) 306 { 307 return ((loff_t)page_file_index(page)) << PAGE_CACHE_SHIFT; 308 } 309 310 extern pgoff_t linear_hugepage_index(struct vm_area_struct *vma, 311 unsigned long address); 312 313 static inline pgoff_t linear_page_index(struct vm_area_struct *vma, 314 unsigned long address) 315 { 316 pgoff_t pgoff; 317 if (unlikely(is_vm_hugetlb_page(vma))) 318 return linear_hugepage_index(vma, address); 319 pgoff = (address - vma->vm_start) >> PAGE_SHIFT; 320 pgoff += vma->vm_pgoff; 321 return pgoff >> (PAGE_CACHE_SHIFT - PAGE_SHIFT); 322 } 323 324 extern void __lock_page(struct page *page); 325 extern int __lock_page_killable(struct page *page); 326 extern int __lock_page_or_retry(struct page *page, struct mm_struct *mm, 327 unsigned int flags); 328 extern void unlock_page(struct page *page); 329 330 static inline void __set_page_locked(struct page *page) 331 { 332 __set_bit(PG_locked, &page->flags); 333 } 334 335 static inline void __clear_page_locked(struct page *page) 336 { 337 __clear_bit(PG_locked, &page->flags); 338 } 339 340 static inline int trylock_page(struct page *page) 341 { 342 return (likely(!test_and_set_bit_lock(PG_locked, &page->flags))); 343 } 344 345 /* 346 * lock_page may only be called if we have the page's inode pinned. 347 */ 348 static inline void lock_page(struct page *page) 349 { 350 might_sleep(); 351 if (!trylock_page(page)) 352 __lock_page(page); 353 } 354 355 /* 356 * lock_page_killable is like lock_page but can be interrupted by fatal 357 * signals. It returns 0 if it locked the page and -EINTR if it was 358 * killed while waiting. 359 */ 360 static inline int lock_page_killable(struct page *page) 361 { 362 might_sleep(); 363 if (!trylock_page(page)) 364 return __lock_page_killable(page); 365 return 0; 366 } 367 368 /* 369 * lock_page_or_retry - Lock the page, unless this would block and the 370 * caller indicated that it can handle a retry. 371 */ 372 static inline int lock_page_or_retry(struct page *page, struct mm_struct *mm, 373 unsigned int flags) 374 { 375 might_sleep(); 376 return trylock_page(page) || __lock_page_or_retry(page, mm, flags); 377 } 378 379 /* 380 * This is exported only for wait_on_page_locked/wait_on_page_writeback. 381 * Never use this directly! 382 */ 383 extern void wait_on_page_bit(struct page *page, int bit_nr); 384 385 extern int wait_on_page_bit_killable(struct page *page, int bit_nr); 386 387 static inline int wait_on_page_locked_killable(struct page *page) 388 { 389 if (PageLocked(page)) 390 return wait_on_page_bit_killable(page, PG_locked); 391 return 0; 392 } 393 394 /* 395 * Wait for a page to be unlocked. 396 * 397 * This must be called with the caller "holding" the page, 398 * ie with increased "page->count" so that the page won't 399 * go away during the wait.. 400 */ 401 static inline void wait_on_page_locked(struct page *page) 402 { 403 if (PageLocked(page)) 404 wait_on_page_bit(page, PG_locked); 405 } 406 407 /* 408 * Wait for a page to complete writeback 409 */ 410 static inline void wait_on_page_writeback(struct page *page) 411 { 412 if (PageWriteback(page)) 413 wait_on_page_bit(page, PG_writeback); 414 } 415 416 extern void end_page_writeback(struct page *page); 417 void wait_for_stable_page(struct page *page); 418 419 /* 420 * Add an arbitrary waiter to a page's wait queue 421 */ 422 extern void add_page_wait_queue(struct page *page, wait_queue_t *waiter); 423 424 /* 425 * Fault a userspace page into pagetables. Return non-zero on a fault. 426 * 427 * This assumes that two userspace pages are always sufficient. That's 428 * not true if PAGE_CACHE_SIZE > PAGE_SIZE. 429 */ 430 static inline int fault_in_pages_writeable(char __user *uaddr, int size) 431 { 432 int ret; 433 434 if (unlikely(size == 0)) 435 return 0; 436 437 /* 438 * Writing zeroes into userspace here is OK, because we know that if 439 * the zero gets there, we'll be overwriting it. 440 */ 441 ret = __put_user(0, uaddr); 442 if (ret == 0) { 443 char __user *end = uaddr + size - 1; 444 445 /* 446 * If the page was already mapped, this will get a cache miss 447 * for sure, so try to avoid doing it. 448 */ 449 if (((unsigned long)uaddr & PAGE_MASK) != 450 ((unsigned long)end & PAGE_MASK)) 451 ret = __put_user(0, end); 452 } 453 return ret; 454 } 455 456 static inline int fault_in_pages_readable(const char __user *uaddr, int size) 457 { 458 volatile char c; 459 int ret; 460 461 if (unlikely(size == 0)) 462 return 0; 463 464 ret = __get_user(c, uaddr); 465 if (ret == 0) { 466 const char __user *end = uaddr + size - 1; 467 468 if (((unsigned long)uaddr & PAGE_MASK) != 469 ((unsigned long)end & PAGE_MASK)) { 470 ret = __get_user(c, end); 471 (void)c; 472 } 473 } 474 return ret; 475 } 476 477 /* 478 * Multipage variants of the above prefault helpers, useful if more than 479 * PAGE_SIZE of data needs to be prefaulted. These are separate from the above 480 * functions (which only handle up to PAGE_SIZE) to avoid clobbering the 481 * filemap.c hotpaths. 482 */ 483 static inline int fault_in_multipages_writeable(char __user *uaddr, int size) 484 { 485 int ret = 0; 486 char __user *end = uaddr + size - 1; 487 488 if (unlikely(size == 0)) 489 return ret; 490 491 /* 492 * Writing zeroes into userspace here is OK, because we know that if 493 * the zero gets there, we'll be overwriting it. 494 */ 495 while (uaddr <= end) { 496 ret = __put_user(0, uaddr); 497 if (ret != 0) 498 return ret; 499 uaddr += PAGE_SIZE; 500 } 501 502 /* Check whether the range spilled into the next page. */ 503 if (((unsigned long)uaddr & PAGE_MASK) == 504 ((unsigned long)end & PAGE_MASK)) 505 ret = __put_user(0, end); 506 507 return ret; 508 } 509 510 static inline int fault_in_multipages_readable(const char __user *uaddr, 511 int size) 512 { 513 volatile char c; 514 int ret = 0; 515 const char __user *end = uaddr + size - 1; 516 517 if (unlikely(size == 0)) 518 return ret; 519 520 while (uaddr <= end) { 521 ret = __get_user(c, uaddr); 522 if (ret != 0) 523 return ret; 524 uaddr += PAGE_SIZE; 525 } 526 527 /* Check whether the range spilled into the next page. */ 528 if (((unsigned long)uaddr & PAGE_MASK) == 529 ((unsigned long)end & PAGE_MASK)) { 530 ret = __get_user(c, end); 531 (void)c; 532 } 533 534 return ret; 535 } 536 537 int add_to_page_cache_locked(struct page *page, struct address_space *mapping, 538 pgoff_t index, gfp_t gfp_mask); 539 int add_to_page_cache_lru(struct page *page, struct address_space *mapping, 540 pgoff_t index, gfp_t gfp_mask); 541 extern void delete_from_page_cache(struct page *page); 542 extern void __delete_from_page_cache(struct page *page); 543 int replace_page_cache_page(struct page *old, struct page *new, gfp_t gfp_mask); 544 545 /* 546 * Like add_to_page_cache_locked, but used to add newly allocated pages: 547 * the page is new, so we can just run __set_page_locked() against it. 548 */ 549 static inline int add_to_page_cache(struct page *page, 550 struct address_space *mapping, pgoff_t offset, gfp_t gfp_mask) 551 { 552 int error; 553 554 __set_page_locked(page); 555 error = add_to_page_cache_locked(page, mapping, offset, gfp_mask); 556 if (unlikely(error)) 557 __clear_page_locked(page); 558 return error; 559 } 560 561 #endif /* _LINUX_PAGEMAP_H */ 562
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