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 */ 22enum 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_EXITING = __GFP_BITS_SHIFT + 4, /* final truncate in progress */ 28}; 29 30static 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 40static inline void mapping_set_unevictable(struct address_space *mapping) 41{ 42 set_bit(AS_UNEVICTABLE, &mapping->flags); 43} 44 45static inline void mapping_clear_unevictable(struct address_space *mapping) 46{ 47 clear_bit(AS_UNEVICTABLE, &mapping->flags); 48} 49 50static 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 57static inline void mapping_set_exiting(struct address_space *mapping) 58{ 59 set_bit(AS_EXITING, &mapping->flags); 60} 61 62static inline int mapping_exiting(struct address_space *mapping) 63{ 64 return test_bit(AS_EXITING, &mapping->flags); 65} 66 67static inline gfp_t mapping_gfp_mask(struct address_space * mapping) 68{ 69 return (__force gfp_t)mapping->flags & __GFP_BITS_MASK; 70} 71 72/* 73 * This is non-atomic. Only to be used before the mapping is activated. 74 * Probably needs a barrier... 75 */ 76static inline void mapping_set_gfp_mask(struct address_space *m, gfp_t mask) 77{ 78 m->flags = (m->flags & ~(__force unsigned long)__GFP_BITS_MASK) | 79 (__force unsigned long)mask; 80} 81 82/* 83 * The page cache can be done in larger chunks than 84 * one page, because it allows for more efficient 85 * throughput (it can then be mapped into user 86 * space in smaller chunks for same flexibility). 87 * 88 * Or rather, it _will_ be done in larger chunks. 89 */ 90#define PAGE_CACHE_SHIFT PAGE_SHIFT 91#define PAGE_CACHE_SIZE PAGE_SIZE 92#define PAGE_CACHE_MASK PAGE_MASK 93#define PAGE_CACHE_ALIGN(addr) (((addr)+PAGE_CACHE_SIZE-1)&PAGE_CACHE_MASK) 94 95#define page_cache_get(page) get_page(page) 96#define page_cache_release(page) put_page(page) 97void release_pages(struct page **pages, int nr, bool cold); 98 99/* 100 * speculatively take a reference to a page. 101 * If the page is free (_count == 0), then _count is untouched, and 0 102 * is returned. Otherwise, _count is incremented by 1 and 1 is returned. 103 * 104 * This function must be called inside the same rcu_read_lock() section as has 105 * been used to lookup the page in the pagecache radix-tree (or page table): 106 * this allows allocators to use a synchronize_rcu() to stabilize _count. 107 * 108 * Unless an RCU grace period has passed, the count of all pages coming out 109 * of the allocator must be considered unstable. page_count may return higher 110 * than expected, and put_page must be able to do the right thing when the 111 * page has been finished with, no matter what it is subsequently allocated 112 * for (because put_page is what is used here to drop an invalid speculative 113 * reference). 114 * 115 * This is the interesting part of the lockless pagecache (and lockless 116 * get_user_pages) locking protocol, where the lookup-side (eg. find_get_page) 117 * has the following pattern: 118 * 1. find page in radix tree 119 * 2. conditionally increment refcount 120 * 3. check the page is still in pagecache (if no, goto 1) 121 * 122 * Remove-side that cares about stability of _count (eg. reclaim) has the 123 * following (with tree_lock held for write): 124 * A. atomically check refcount is correct and set it to 0 (atomic_cmpxchg) 125 * B. remove page from pagecache 126 * C. free the page 127 * 128 * There are 2 critical interleavings that matter: 129 * - 2 runs before A: in this case, A sees elevated refcount and bails out 130 * - A runs before 2: in this case, 2 sees zero refcount and retries; 131 * subsequently, B will complete and 1 will find no page, causing the 132 * lookup to return NULL. 133 * 134 * It is possible that between 1 and 2, the page is removed then the exact same 135 * page is inserted into the same position in pagecache. That's OK: the 136 * old find_get_page using tree_lock could equally have run before or after 137 * such a re-insertion, depending on order that locks are granted. 138 * 139 * Lookups racing against pagecache insertion isn't a big problem: either 1 140 * will find the page or it will not. Likewise, the old find_get_page could run 141 * either before the insertion or afterwards, depending on timing. 142 */ 143static inline int page_cache_get_speculative(struct page *page) 144{ 145 VM_BUG_ON(in_interrupt()); 146 147#ifdef CONFIG_TINY_RCU 148# ifdef CONFIG_PREEMPT_COUNT 149 VM_BUG_ON(!in_atomic()); 150# endif 151 /* 152 * Preempt must be disabled here - we rely on rcu_read_lock doing 153 * this for us. 154 * 155 * Pagecache won't be truncated from interrupt context, so if we have 156 * found a page in the radix tree here, we have pinned its refcount by 157 * disabling preempt, and hence no need for the "speculative get" that 158 * SMP requires. 159 */ 160 VM_BUG_ON_PAGE(page_count(page) == 0, page); 161 atomic_inc(&page->_count); 162 163#else 164 if (unlikely(!get_page_unless_zero(page))) { 165 /* 166 * Either the page has been freed, or will be freed. 167 * In either case, retry here and the caller should 168 * do the right thing (see comments above). 169 */ 170 return 0; 171 } 172#endif 173 VM_BUG_ON_PAGE(PageTail(page), page); 174 175 return 1; 176} 177 178/* 179 * Same as above, but add instead of inc (could just be merged) 180 */ 181static inline int page_cache_add_speculative(struct page *page, int count) 182{ 183 VM_BUG_ON(in_interrupt()); 184 185#if !defined(CONFIG_SMP) && defined(CONFIG_TREE_RCU) 186# ifdef CONFIG_PREEMPT_COUNT 187 VM_BUG_ON(!in_atomic()); 188# endif 189 VM_BUG_ON_PAGE(page_count(page) == 0, page); 190 atomic_add(count, &page->_count); 191 192#else 193 if (unlikely(!atomic_add_unless(&page->_count, count, 0))) 194 return 0; 195#endif 196 VM_BUG_ON_PAGE(PageCompound(page) && page != compound_head(page), page); 197 198 return 1; 199} 200 201static inline int page_freeze_refs(struct page *page, int count) 202{ 203 return likely(atomic_cmpxchg(&page->_count, count, 0) == count); 204} 205 206static inline void page_unfreeze_refs(struct page *page, int count) 207{ 208 VM_BUG_ON_PAGE(page_count(page) != 0, page); 209 VM_BUG_ON(count == 0); 210 211 atomic_set(&page->_count, count); 212} 213 214#ifdef CONFIG_NUMA 215extern struct page *__page_cache_alloc(gfp_t gfp); 216#else 217static inline struct page *__page_cache_alloc(gfp_t gfp) 218{ 219 return alloc_pages(gfp, 0); 220} 221#endif 222 223static inline struct page *page_cache_alloc(struct address_space *x) 224{ 225 return __page_cache_alloc(mapping_gfp_mask(x)); 226} 227 228static inline struct page *page_cache_alloc_cold(struct address_space *x) 229{ 230 return __page_cache_alloc(mapping_gfp_mask(x)|__GFP_COLD); 231} 232 233static inline struct page *page_cache_alloc_readahead(struct address_space *x) 234{ 235 return __page_cache_alloc(mapping_gfp_mask(x) | 236 __GFP_COLD | __GFP_NORETRY | __GFP_NOWARN); 237} 238 239typedef int filler_t(void *, struct page *); 240 241pgoff_t page_cache_next_hole(struct address_space *mapping, 242 pgoff_t index, unsigned long max_scan); 243pgoff_t page_cache_prev_hole(struct address_space *mapping, 244 pgoff_t index, unsigned long max_scan); 245 246#define FGP_ACCESSED 0x00000001 247#define FGP_LOCK 0x00000002 248#define FGP_CREAT 0x00000004 249#define FGP_WRITE 0x00000008 250#define FGP_NOFS 0x00000010 251#define FGP_NOWAIT 0x00000020 252 253struct page *pagecache_get_page(struct address_space *mapping, pgoff_t offset, 254 int fgp_flags, gfp_t cache_gfp_mask); 255 256/** 257 * find_get_page - find and get a page reference 258 * @mapping: the address_space to search 259 * @offset: the page index 260 * 261 * Looks up the page cache slot at @mapping & @offset. If there is a 262 * page cache page, it is returned with an increased refcount. 263 * 264 * Otherwise, %NULL is returned. 265 */ 266static inline struct page *find_get_page(struct address_space *mapping, 267 pgoff_t offset) 268{ 269 return pagecache_get_page(mapping, offset, 0, 0); 270} 271 272static inline struct page *find_get_page_flags(struct address_space *mapping, 273 pgoff_t offset, int fgp_flags) 274{ 275 return pagecache_get_page(mapping, offset, fgp_flags, 0); 276} 277 278/** 279 * find_lock_page - locate, pin and lock a pagecache page 280 * pagecache_get_page - find and get a page reference 281 * @mapping: the address_space to search 282 * @offset: the page index 283 * 284 * Looks up the page cache slot at @mapping & @offset. If there is a 285 * page cache page, it is returned locked and with an increased 286 * refcount. 287 * 288 * Otherwise, %NULL is returned. 289 * 290 * find_lock_page() may sleep. 291 */ 292static inline struct page *find_lock_page(struct address_space *mapping, 293 pgoff_t offset) 294{ 295 return pagecache_get_page(mapping, offset, FGP_LOCK, 0); 296} 297 298/** 299 * find_or_create_page - locate or add a pagecache page 300 * @mapping: the page's address_space 301 * @index: the page's index into the mapping 302 * @gfp_mask: page allocation mode 303 * 304 * Looks up the page cache slot at @mapping & @offset. If there is a 305 * page cache page, it is returned locked and with an increased 306 * refcount. 307 * 308 * If the page is not present, a new page is allocated using @gfp_mask 309 * and added to the page cache and the VM's LRU list. The page is 310 * returned locked and with an increased refcount. 311 * 312 * On memory exhaustion, %NULL is returned. 313 * 314 * find_or_create_page() may sleep, even if @gfp_flags specifies an 315 * atomic allocation! 316 */ 317static inline struct page *find_or_create_page(struct address_space *mapping, 318 pgoff_t offset, gfp_t gfp_mask) 319{ 320 return pagecache_get_page(mapping, offset, 321 FGP_LOCK|FGP_ACCESSED|FGP_CREAT, 322 gfp_mask); 323} 324 325/** 326 * grab_cache_page_nowait - returns locked page at given index in given cache 327 * @mapping: target address_space 328 * @index: the page index 329 * 330 * Same as grab_cache_page(), but do not wait if the page is unavailable. 331 * This is intended for speculative data generators, where the data can 332 * be regenerated if the page couldn't be grabbed. This routine should 333 * be safe to call while holding the lock for another page. 334 * 335 * Clear __GFP_FS when allocating the page to avoid recursion into the fs 336 * and deadlock against the caller's locked page. 337 */ 338static inline struct page *grab_cache_page_nowait(struct address_space *mapping, 339 pgoff_t index) 340{ 341 return pagecache_get_page(mapping, index, 342 FGP_LOCK|FGP_CREAT|FGP_NOFS|FGP_NOWAIT, 343 mapping_gfp_mask(mapping)); 344} 345 346struct page *find_get_entry(struct address_space *mapping, pgoff_t offset); 347struct page *find_lock_entry(struct address_space *mapping, pgoff_t offset); 348unsigned find_get_entries(struct address_space *mapping, pgoff_t start, 349 unsigned int nr_entries, struct page **entries, 350 pgoff_t *indices); 351unsigned find_get_pages(struct address_space *mapping, pgoff_t start, 352 unsigned int nr_pages, struct page **pages); 353unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t start, 354 unsigned int nr_pages, struct page **pages); 355unsigned find_get_pages_tag(struct address_space *mapping, pgoff_t *index, 356 int tag, unsigned int nr_pages, struct page **pages); 357 358struct page *grab_cache_page_write_begin(struct address_space *mapping, 359 pgoff_t index, unsigned flags); 360 361/* 362 * Returns locked page at given index in given cache, creating it if needed. 363 */ 364static inline struct page *grab_cache_page(struct address_space *mapping, 365 pgoff_t index) 366{ 367 return find_or_create_page(mapping, index, mapping_gfp_mask(mapping)); 368} 369 370extern struct page * read_cache_page(struct address_space *mapping, 371 pgoff_t index, filler_t *filler, void *data); 372extern struct page * read_cache_page_gfp(struct address_space *mapping, 373 pgoff_t index, gfp_t gfp_mask); 374extern int read_cache_pages(struct address_space *mapping, 375 struct list_head *pages, filler_t *filler, void *data); 376 377static inline struct page *read_mapping_page(struct address_space *mapping, 378 pgoff_t index, void *data) 379{ 380 filler_t *filler = (filler_t *)mapping->a_ops->readpage; 381 return read_cache_page(mapping, index, filler, data); 382} 383 384/* 385 * Get the offset in PAGE_SIZE. 386 * (TODO: hugepage should have ->index in PAGE_SIZE) 387 */ 388static inline pgoff_t page_to_pgoff(struct page *page) 389{ 390 if (unlikely(PageHeadHuge(page))) 391 return page->index << compound_order(page); 392 else 393 return page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT); 394} 395 396/* 397 * Return byte-offset into filesystem object for page. 398 */ 399static inline loff_t page_offset(struct page *page) 400{ 401 return ((loff_t)page->index) << PAGE_CACHE_SHIFT; 402} 403 404static inline loff_t page_file_offset(struct page *page) 405{ 406 return ((loff_t)page_file_index(page)) << PAGE_CACHE_SHIFT; 407} 408 409extern pgoff_t linear_hugepage_index(struct vm_area_struct *vma, 410 unsigned long address); 411 412static inline pgoff_t linear_page_index(struct vm_area_struct *vma, 413 unsigned long address) 414{ 415 pgoff_t pgoff; 416 if (unlikely(is_vm_hugetlb_page(vma))) 417 return linear_hugepage_index(vma, address); 418 pgoff = (address - vma->vm_start) >> PAGE_SHIFT; 419 pgoff += vma->vm_pgoff; 420 return pgoff >> (PAGE_CACHE_SHIFT - PAGE_SHIFT); 421} 422 423extern void __lock_page(struct page *page); 424extern int __lock_page_killable(struct page *page); 425extern int __lock_page_or_retry(struct page *page, struct mm_struct *mm, 426 unsigned int flags); 427extern void unlock_page(struct page *page); 428 429static inline void __set_page_locked(struct page *page) 430{ 431 __set_bit(PG_locked, &page->flags); 432} 433 434static inline void __clear_page_locked(struct page *page) 435{ 436 __clear_bit(PG_locked, &page->flags); 437} 438 439static inline int trylock_page(struct page *page) 440{ 441 return (likely(!test_and_set_bit_lock(PG_locked, &page->flags))); 442} 443 444/* 445 * lock_page may only be called if we have the page's inode pinned. 446 */ 447static inline void lock_page(struct page *page) 448{ 449 might_sleep(); 450 if (!trylock_page(page)) 451 __lock_page(page); 452} 453 454/* 455 * lock_page_killable is like lock_page but can be interrupted by fatal 456 * signals. It returns 0 if it locked the page and -EINTR if it was 457 * killed while waiting. 458 */ 459static inline int lock_page_killable(struct page *page) 460{ 461 might_sleep(); 462 if (!trylock_page(page)) 463 return __lock_page_killable(page); 464 return 0; 465} 466 467/* 468 * lock_page_or_retry - Lock the page, unless this would block and the 469 * caller indicated that it can handle a retry. 470 * 471 * Return value and mmap_sem implications depend on flags; see 472 * __lock_page_or_retry(). 473 */ 474static inline int lock_page_or_retry(struct page *page, struct mm_struct *mm, 475 unsigned int flags) 476{ 477 might_sleep(); 478 return trylock_page(page) || __lock_page_or_retry(page, mm, flags); 479} 480 481/* 482 * This is exported only for wait_on_page_locked/wait_on_page_writeback, 483 * and for filesystems which need to wait on PG_private. 484 */ 485extern void wait_on_page_bit(struct page *page, int bit_nr); 486 487extern int wait_on_page_bit_killable(struct page *page, int bit_nr); 488extern int wait_on_page_bit_killable_timeout(struct page *page, 489 int bit_nr, unsigned long timeout); 490 491static inline int wait_on_page_locked_killable(struct page *page) 492{ 493 if (PageLocked(page)) 494 return wait_on_page_bit_killable(page, PG_locked); 495 return 0; 496} 497 498extern wait_queue_head_t *page_waitqueue(struct page *page); 499static inline void wake_up_page(struct page *page, int bit) 500{ 501 __wake_up_bit(page_waitqueue(page), &page->flags, bit); 502} 503 504/* 505 * Wait for a page to be unlocked. 506 * 507 * This must be called with the caller "holding" the page, 508 * ie with increased "page->count" so that the page won't 509 * go away during the wait.. 510 */ 511static inline void wait_on_page_locked(struct page *page) 512{ 513 if (PageLocked(page)) 514 wait_on_page_bit(page, PG_locked); 515} 516 517/* 518 * Wait for a page to complete writeback 519 */ 520static inline void wait_on_page_writeback(struct page *page) 521{ 522 if (PageWriteback(page)) 523 wait_on_page_bit(page, PG_writeback); 524} 525 526extern void end_page_writeback(struct page *page); 527void wait_for_stable_page(struct page *page); 528 529void page_endio(struct page *page, int rw, int err); 530 531/* 532 * Add an arbitrary waiter to a page's wait queue 533 */ 534extern void add_page_wait_queue(struct page *page, wait_queue_t *waiter); 535 536/* 537 * Fault a userspace page into pagetables. Return non-zero on a fault. 538 * 539 * This assumes that two userspace pages are always sufficient. That's 540 * not true if PAGE_CACHE_SIZE > PAGE_SIZE. 541 */ 542static inline int fault_in_pages_writeable(char __user *uaddr, int size) 543{ 544 int ret; 545 546 if (unlikely(size == 0)) 547 return 0; 548 549 /* 550 * Writing zeroes into userspace here is OK, because we know that if 551 * the zero gets there, we'll be overwriting it. 552 */ 553 ret = __put_user(0, uaddr); 554 if (ret == 0) { 555 char __user *end = uaddr + size - 1; 556 557 /* 558 * If the page was already mapped, this will get a cache miss 559 * for sure, so try to avoid doing it. 560 */ 561 if (((unsigned long)uaddr & PAGE_MASK) != 562 ((unsigned long)end & PAGE_MASK)) 563 ret = __put_user(0, end); 564 } 565 return ret; 566} 567 568static inline int fault_in_pages_readable(const char __user *uaddr, int size) 569{ 570 volatile char c; 571 int ret; 572 573 if (unlikely(size == 0)) 574 return 0; 575 576 ret = __get_user(c, uaddr); 577 if (ret == 0) { 578 const char __user *end = uaddr + size - 1; 579 580 if (((unsigned long)uaddr & PAGE_MASK) != 581 ((unsigned long)end & PAGE_MASK)) { 582 ret = __get_user(c, end); 583 (void)c; 584 } 585 } 586 return ret; 587} 588 589/* 590 * Multipage variants of the above prefault helpers, useful if more than 591 * PAGE_SIZE of data needs to be prefaulted. These are separate from the above 592 * functions (which only handle up to PAGE_SIZE) to avoid clobbering the 593 * filemap.c hotpaths. 594 */ 595static inline int fault_in_multipages_writeable(char __user *uaddr, int size) 596{ 597 int ret = 0; 598 char __user *end = uaddr + size - 1; 599 600 if (unlikely(size == 0)) 601 return ret; 602 603 /* 604 * Writing zeroes into userspace here is OK, because we know that if 605 * the zero gets there, we'll be overwriting it. 606 */ 607 while (uaddr <= end) { 608 ret = __put_user(0, uaddr); 609 if (ret != 0) 610 return ret; 611 uaddr += PAGE_SIZE; 612 } 613 614 /* Check whether the range spilled into the next page. */ 615 if (((unsigned long)uaddr & PAGE_MASK) == 616 ((unsigned long)end & PAGE_MASK)) 617 ret = __put_user(0, end); 618 619 return ret; 620} 621 622static inline int fault_in_multipages_readable(const char __user *uaddr, 623 int size) 624{ 625 volatile char c; 626 int ret = 0; 627 const char __user *end = uaddr + size - 1; 628 629 if (unlikely(size == 0)) 630 return ret; 631 632 while (uaddr <= end) { 633 ret = __get_user(c, uaddr); 634 if (ret != 0) 635 return ret; 636 uaddr += PAGE_SIZE; 637 } 638 639 /* Check whether the range spilled into the next page. */ 640 if (((unsigned long)uaddr & PAGE_MASK) == 641 ((unsigned long)end & PAGE_MASK)) { 642 ret = __get_user(c, end); 643 (void)c; 644 } 645 646 return ret; 647} 648 649int add_to_page_cache_locked(struct page *page, struct address_space *mapping, 650 pgoff_t index, gfp_t gfp_mask); 651int add_to_page_cache_lru(struct page *page, struct address_space *mapping, 652 pgoff_t index, gfp_t gfp_mask); 653extern void delete_from_page_cache(struct page *page); 654extern void __delete_from_page_cache(struct page *page, void *shadow); 655int replace_page_cache_page(struct page *old, struct page *new, gfp_t gfp_mask); 656 657/* 658 * Like add_to_page_cache_locked, but used to add newly allocated pages: 659 * the page is new, so we can just run __set_page_locked() against it. 660 */ 661static inline int add_to_page_cache(struct page *page, 662 struct address_space *mapping, pgoff_t offset, gfp_t gfp_mask) 663{ 664 int error; 665 666 __set_page_locked(page); 667 error = add_to_page_cache_locked(page, mapping, offset, gfp_mask); 668 if (unlikely(error)) 669 __clear_page_locked(page); 670 return error; 671} 672 673#endif /* _LINUX_PAGEMAP_H */ 674