filemap.c revision f4c0a0fdfae708f7aa438c27a380ed4071294e11
1/* 2 * linux/mm/filemap.c 3 * 4 * Copyright (C) 1994-1999 Linus Torvalds 5 */ 6 7/* 8 * This file handles the generic file mmap semantics used by 9 * most "normal" filesystems (but you don't /have/ to use this: 10 * the NFS filesystem used to do this differently, for example) 11 */ 12#include <linux/module.h> 13#include <linux/slab.h> 14#include <linux/compiler.h> 15#include <linux/fs.h> 16#include <linux/uaccess.h> 17#include <linux/aio.h> 18#include <linux/capability.h> 19#include <linux/kernel_stat.h> 20#include <linux/mm.h> 21#include <linux/swap.h> 22#include <linux/mman.h> 23#include <linux/pagemap.h> 24#include <linux/file.h> 25#include <linux/uio.h> 26#include <linux/hash.h> 27#include <linux/writeback.h> 28#include <linux/backing-dev.h> 29#include <linux/pagevec.h> 30#include <linux/blkdev.h> 31#include <linux/security.h> 32#include <linux/syscalls.h> 33#include <linux/cpuset.h> 34#include <linux/hardirq.h> /* for BUG_ON(!in_atomic()) only */ 35#include <linux/memcontrol.h> 36#include "internal.h" 37 38/* 39 * FIXME: remove all knowledge of the buffer layer from the core VM 40 */ 41#include <linux/buffer_head.h> /* for generic_osync_inode */ 42 43#include <asm/mman.h> 44 45static ssize_t 46generic_file_direct_IO(int rw, struct kiocb *iocb, const struct iovec *iov, 47 loff_t offset, unsigned long nr_segs); 48 49/* 50 * Shared mappings implemented 30.11.1994. It's not fully working yet, 51 * though. 52 * 53 * Shared mappings now work. 15.8.1995 Bruno. 54 * 55 * finished 'unifying' the page and buffer cache and SMP-threaded the 56 * page-cache, 21.05.1999, Ingo Molnar <mingo@redhat.com> 57 * 58 * SMP-threaded pagemap-LRU 1999, Andrea Arcangeli <andrea@suse.de> 59 */ 60 61/* 62 * Lock ordering: 63 * 64 * ->i_mmap_lock (vmtruncate) 65 * ->private_lock (__free_pte->__set_page_dirty_buffers) 66 * ->swap_lock (exclusive_swap_page, others) 67 * ->mapping->tree_lock 68 * 69 * ->i_mutex 70 * ->i_mmap_lock (truncate->unmap_mapping_range) 71 * 72 * ->mmap_sem 73 * ->i_mmap_lock 74 * ->page_table_lock or pte_lock (various, mainly in memory.c) 75 * ->mapping->tree_lock (arch-dependent flush_dcache_mmap_lock) 76 * 77 * ->mmap_sem 78 * ->lock_page (access_process_vm) 79 * 80 * ->i_mutex (generic_file_buffered_write) 81 * ->mmap_sem (fault_in_pages_readable->do_page_fault) 82 * 83 * ->i_mutex 84 * ->i_alloc_sem (various) 85 * 86 * ->inode_lock 87 * ->sb_lock (fs/fs-writeback.c) 88 * ->mapping->tree_lock (__sync_single_inode) 89 * 90 * ->i_mmap_lock 91 * ->anon_vma.lock (vma_adjust) 92 * 93 * ->anon_vma.lock 94 * ->page_table_lock or pte_lock (anon_vma_prepare and various) 95 * 96 * ->page_table_lock or pte_lock 97 * ->swap_lock (try_to_unmap_one) 98 * ->private_lock (try_to_unmap_one) 99 * ->tree_lock (try_to_unmap_one) 100 * ->zone.lru_lock (follow_page->mark_page_accessed) 101 * ->zone.lru_lock (check_pte_range->isolate_lru_page) 102 * ->private_lock (page_remove_rmap->set_page_dirty) 103 * ->tree_lock (page_remove_rmap->set_page_dirty) 104 * ->inode_lock (page_remove_rmap->set_page_dirty) 105 * ->inode_lock (zap_pte_range->set_page_dirty) 106 * ->private_lock (zap_pte_range->__set_page_dirty_buffers) 107 * 108 * ->task->proc_lock 109 * ->dcache_lock (proc_pid_lookup) 110 */ 111 112/* 113 * Remove a page from the page cache and free it. Caller has to make 114 * sure the page is locked and that nobody else uses it - or that usage 115 * is safe. The caller must hold a write_lock on the mapping's tree_lock. 116 */ 117void __remove_from_page_cache(struct page *page) 118{ 119 struct address_space *mapping = page->mapping; 120 121 mem_cgroup_uncharge_page(page); 122 radix_tree_delete(&mapping->page_tree, page->index); 123 page->mapping = NULL; 124 mapping->nrpages--; 125 __dec_zone_page_state(page, NR_FILE_PAGES); 126 BUG_ON(page_mapped(page)); 127 128 /* 129 * Some filesystems seem to re-dirty the page even after 130 * the VM has canceled the dirty bit (eg ext3 journaling). 131 * 132 * Fix it up by doing a final dirty accounting check after 133 * having removed the page entirely. 134 */ 135 if (PageDirty(page) && mapping_cap_account_dirty(mapping)) { 136 dec_zone_page_state(page, NR_FILE_DIRTY); 137 dec_bdi_stat(mapping->backing_dev_info, BDI_RECLAIMABLE); 138 } 139} 140 141void remove_from_page_cache(struct page *page) 142{ 143 struct address_space *mapping = page->mapping; 144 145 BUG_ON(!PageLocked(page)); 146 147 write_lock_irq(&mapping->tree_lock); 148 __remove_from_page_cache(page); 149 write_unlock_irq(&mapping->tree_lock); 150} 151 152static int sync_page(void *word) 153{ 154 struct address_space *mapping; 155 struct page *page; 156 157 page = container_of((unsigned long *)word, struct page, flags); 158 159 /* 160 * page_mapping() is being called without PG_locked held. 161 * Some knowledge of the state and use of the page is used to 162 * reduce the requirements down to a memory barrier. 163 * The danger here is of a stale page_mapping() return value 164 * indicating a struct address_space different from the one it's 165 * associated with when it is associated with one. 166 * After smp_mb(), it's either the correct page_mapping() for 167 * the page, or an old page_mapping() and the page's own 168 * page_mapping() has gone NULL. 169 * The ->sync_page() address_space operation must tolerate 170 * page_mapping() going NULL. By an amazing coincidence, 171 * this comes about because none of the users of the page 172 * in the ->sync_page() methods make essential use of the 173 * page_mapping(), merely passing the page down to the backing 174 * device's unplug functions when it's non-NULL, which in turn 175 * ignore it for all cases but swap, where only page_private(page) is 176 * of interest. When page_mapping() does go NULL, the entire 177 * call stack gracefully ignores the page and returns. 178 * -- wli 179 */ 180 smp_mb(); 181 mapping = page_mapping(page); 182 if (mapping && mapping->a_ops && mapping->a_ops->sync_page) 183 mapping->a_ops->sync_page(page); 184 io_schedule(); 185 return 0; 186} 187 188static int sync_page_killable(void *word) 189{ 190 sync_page(word); 191 return fatal_signal_pending(current) ? -EINTR : 0; 192} 193 194/** 195 * __filemap_fdatawrite_range - start writeback on mapping dirty pages in range 196 * @mapping: address space structure to write 197 * @start: offset in bytes where the range starts 198 * @end: offset in bytes where the range ends (inclusive) 199 * @sync_mode: enable synchronous operation 200 * 201 * Start writeback against all of a mapping's dirty pages that lie 202 * within the byte offsets <start, end> inclusive. 203 * 204 * If sync_mode is WB_SYNC_ALL then this is a "data integrity" operation, as 205 * opposed to a regular memory cleansing writeback. The difference between 206 * these two operations is that if a dirty page/buffer is encountered, it must 207 * be waited upon, and not just skipped over. 208 */ 209int __filemap_fdatawrite_range(struct address_space *mapping, loff_t start, 210 loff_t end, int sync_mode) 211{ 212 int ret; 213 struct writeback_control wbc = { 214 .sync_mode = sync_mode, 215 .nr_to_write = mapping->nrpages * 2, 216 .range_start = start, 217 .range_end = end, 218 }; 219 220 if (!mapping_cap_writeback_dirty(mapping)) 221 return 0; 222 223 ret = do_writepages(mapping, &wbc); 224 return ret; 225} 226 227static inline int __filemap_fdatawrite(struct address_space *mapping, 228 int sync_mode) 229{ 230 return __filemap_fdatawrite_range(mapping, 0, LLONG_MAX, sync_mode); 231} 232 233int filemap_fdatawrite(struct address_space *mapping) 234{ 235 return __filemap_fdatawrite(mapping, WB_SYNC_ALL); 236} 237EXPORT_SYMBOL(filemap_fdatawrite); 238 239int filemap_fdatawrite_range(struct address_space *mapping, loff_t start, 240 loff_t end) 241{ 242 return __filemap_fdatawrite_range(mapping, start, end, WB_SYNC_ALL); 243} 244EXPORT_SYMBOL(filemap_fdatawrite_range); 245 246/** 247 * filemap_flush - mostly a non-blocking flush 248 * @mapping: target address_space 249 * 250 * This is a mostly non-blocking flush. Not suitable for data-integrity 251 * purposes - I/O may not be started against all dirty pages. 252 */ 253int filemap_flush(struct address_space *mapping) 254{ 255 return __filemap_fdatawrite(mapping, WB_SYNC_NONE); 256} 257EXPORT_SYMBOL(filemap_flush); 258 259/** 260 * wait_on_page_writeback_range - wait for writeback to complete 261 * @mapping: target address_space 262 * @start: beginning page index 263 * @end: ending page index 264 * 265 * Wait for writeback to complete against pages indexed by start->end 266 * inclusive 267 */ 268int wait_on_page_writeback_range(struct address_space *mapping, 269 pgoff_t start, pgoff_t end) 270{ 271 struct pagevec pvec; 272 int nr_pages; 273 int ret = 0; 274 pgoff_t index; 275 276 if (end < start) 277 return 0; 278 279 pagevec_init(&pvec, 0); 280 index = start; 281 while ((index <= end) && 282 (nr_pages = pagevec_lookup_tag(&pvec, mapping, &index, 283 PAGECACHE_TAG_WRITEBACK, 284 min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1)) != 0) { 285 unsigned i; 286 287 for (i = 0; i < nr_pages; i++) { 288 struct page *page = pvec.pages[i]; 289 290 /* until radix tree lookup accepts end_index */ 291 if (page->index > end) 292 continue; 293 294 wait_on_page_writeback(page); 295 if (PageError(page)) 296 ret = -EIO; 297 } 298 pagevec_release(&pvec); 299 cond_resched(); 300 } 301 302 /* Check for outstanding write errors */ 303 if (test_and_clear_bit(AS_ENOSPC, &mapping->flags)) 304 ret = -ENOSPC; 305 if (test_and_clear_bit(AS_EIO, &mapping->flags)) 306 ret = -EIO; 307 308 return ret; 309} 310 311/** 312 * sync_page_range - write and wait on all pages in the passed range 313 * @inode: target inode 314 * @mapping: target address_space 315 * @pos: beginning offset in pages to write 316 * @count: number of bytes to write 317 * 318 * Write and wait upon all the pages in the passed range. This is a "data 319 * integrity" operation. It waits upon in-flight writeout before starting and 320 * waiting upon new writeout. If there was an IO error, return it. 321 * 322 * We need to re-take i_mutex during the generic_osync_inode list walk because 323 * it is otherwise livelockable. 324 */ 325int sync_page_range(struct inode *inode, struct address_space *mapping, 326 loff_t pos, loff_t count) 327{ 328 pgoff_t start = pos >> PAGE_CACHE_SHIFT; 329 pgoff_t end = (pos + count - 1) >> PAGE_CACHE_SHIFT; 330 int ret; 331 332 if (!mapping_cap_writeback_dirty(mapping) || !count) 333 return 0; 334 ret = filemap_fdatawrite_range(mapping, pos, pos + count - 1); 335 if (ret == 0) { 336 mutex_lock(&inode->i_mutex); 337 ret = generic_osync_inode(inode, mapping, OSYNC_METADATA); 338 mutex_unlock(&inode->i_mutex); 339 } 340 if (ret == 0) 341 ret = wait_on_page_writeback_range(mapping, start, end); 342 return ret; 343} 344EXPORT_SYMBOL(sync_page_range); 345 346/** 347 * sync_page_range_nolock - write & wait on all pages in the passed range without locking 348 * @inode: target inode 349 * @mapping: target address_space 350 * @pos: beginning offset in pages to write 351 * @count: number of bytes to write 352 * 353 * Note: Holding i_mutex across sync_page_range_nolock() is not a good idea 354 * as it forces O_SYNC writers to different parts of the same file 355 * to be serialised right until io completion. 356 */ 357int sync_page_range_nolock(struct inode *inode, struct address_space *mapping, 358 loff_t pos, loff_t count) 359{ 360 pgoff_t start = pos >> PAGE_CACHE_SHIFT; 361 pgoff_t end = (pos + count - 1) >> PAGE_CACHE_SHIFT; 362 int ret; 363 364 if (!mapping_cap_writeback_dirty(mapping) || !count) 365 return 0; 366 ret = filemap_fdatawrite_range(mapping, pos, pos + count - 1); 367 if (ret == 0) 368 ret = generic_osync_inode(inode, mapping, OSYNC_METADATA); 369 if (ret == 0) 370 ret = wait_on_page_writeback_range(mapping, start, end); 371 return ret; 372} 373EXPORT_SYMBOL(sync_page_range_nolock); 374 375/** 376 * filemap_fdatawait - wait for all under-writeback pages to complete 377 * @mapping: address space structure to wait for 378 * 379 * Walk the list of under-writeback pages of the given address space 380 * and wait for all of them. 381 */ 382int filemap_fdatawait(struct address_space *mapping) 383{ 384 loff_t i_size = i_size_read(mapping->host); 385 386 if (i_size == 0) 387 return 0; 388 389 return wait_on_page_writeback_range(mapping, 0, 390 (i_size - 1) >> PAGE_CACHE_SHIFT); 391} 392EXPORT_SYMBOL(filemap_fdatawait); 393 394int filemap_write_and_wait(struct address_space *mapping) 395{ 396 int err = 0; 397 398 if (mapping->nrpages) { 399 err = filemap_fdatawrite(mapping); 400 /* 401 * Even if the above returned error, the pages may be 402 * written partially (e.g. -ENOSPC), so we wait for it. 403 * But the -EIO is special case, it may indicate the worst 404 * thing (e.g. bug) happened, so we avoid waiting for it. 405 */ 406 if (err != -EIO) { 407 int err2 = filemap_fdatawait(mapping); 408 if (!err) 409 err = err2; 410 } 411 } 412 return err; 413} 414EXPORT_SYMBOL(filemap_write_and_wait); 415 416/** 417 * filemap_write_and_wait_range - write out & wait on a file range 418 * @mapping: the address_space for the pages 419 * @lstart: offset in bytes where the range starts 420 * @lend: offset in bytes where the range ends (inclusive) 421 * 422 * Write out and wait upon file offsets lstart->lend, inclusive. 423 * 424 * Note that `lend' is inclusive (describes the last byte to be written) so 425 * that this function can be used to write to the very end-of-file (end = -1). 426 */ 427int filemap_write_and_wait_range(struct address_space *mapping, 428 loff_t lstart, loff_t lend) 429{ 430 int err = 0; 431 432 if (mapping->nrpages) { 433 err = __filemap_fdatawrite_range(mapping, lstart, lend, 434 WB_SYNC_ALL); 435 /* See comment of filemap_write_and_wait() */ 436 if (err != -EIO) { 437 int err2 = wait_on_page_writeback_range(mapping, 438 lstart >> PAGE_CACHE_SHIFT, 439 lend >> PAGE_CACHE_SHIFT); 440 if (!err) 441 err = err2; 442 } 443 } 444 return err; 445} 446 447/** 448 * add_to_page_cache - add newly allocated pagecache pages 449 * @page: page to add 450 * @mapping: the page's address_space 451 * @offset: page index 452 * @gfp_mask: page allocation mode 453 * 454 * This function is used to add newly allocated pagecache pages; 455 * the page is new, so we can just run SetPageLocked() against it. 456 * The other page state flags were set by rmqueue(). 457 * 458 * This function does not add the page to the LRU. The caller must do that. 459 */ 460int add_to_page_cache(struct page *page, struct address_space *mapping, 461 pgoff_t offset, gfp_t gfp_mask) 462{ 463 int error = mem_cgroup_cache_charge(page, current->mm, 464 gfp_mask & ~__GFP_HIGHMEM); 465 if (error) 466 goto out; 467 468 error = radix_tree_preload(gfp_mask & ~__GFP_HIGHMEM); 469 if (error == 0) { 470 write_lock_irq(&mapping->tree_lock); 471 error = radix_tree_insert(&mapping->page_tree, offset, page); 472 if (!error) { 473 page_cache_get(page); 474 SetPageLocked(page); 475 page->mapping = mapping; 476 page->index = offset; 477 mapping->nrpages++; 478 __inc_zone_page_state(page, NR_FILE_PAGES); 479 } else 480 mem_cgroup_uncharge_page(page); 481 482 write_unlock_irq(&mapping->tree_lock); 483 radix_tree_preload_end(); 484 } else 485 mem_cgroup_uncharge_page(page); 486out: 487 return error; 488} 489EXPORT_SYMBOL(add_to_page_cache); 490 491int add_to_page_cache_lru(struct page *page, struct address_space *mapping, 492 pgoff_t offset, gfp_t gfp_mask) 493{ 494 int ret = add_to_page_cache(page, mapping, offset, gfp_mask); 495 if (ret == 0) 496 lru_cache_add(page); 497 return ret; 498} 499 500#ifdef CONFIG_NUMA 501struct page *__page_cache_alloc(gfp_t gfp) 502{ 503 if (cpuset_do_page_mem_spread()) { 504 int n = cpuset_mem_spread_node(); 505 return alloc_pages_node(n, gfp, 0); 506 } 507 return alloc_pages(gfp, 0); 508} 509EXPORT_SYMBOL(__page_cache_alloc); 510#endif 511 512static int __sleep_on_page_lock(void *word) 513{ 514 io_schedule(); 515 return 0; 516} 517 518/* 519 * In order to wait for pages to become available there must be 520 * waitqueues associated with pages. By using a hash table of 521 * waitqueues where the bucket discipline is to maintain all 522 * waiters on the same queue and wake all when any of the pages 523 * become available, and for the woken contexts to check to be 524 * sure the appropriate page became available, this saves space 525 * at a cost of "thundering herd" phenomena during rare hash 526 * collisions. 527 */ 528static wait_queue_head_t *page_waitqueue(struct page *page) 529{ 530 const struct zone *zone = page_zone(page); 531 532 return &zone->wait_table[hash_ptr(page, zone->wait_table_bits)]; 533} 534 535static inline void wake_up_page(struct page *page, int bit) 536{ 537 __wake_up_bit(page_waitqueue(page), &page->flags, bit); 538} 539 540void wait_on_page_bit(struct page *page, int bit_nr) 541{ 542 DEFINE_WAIT_BIT(wait, &page->flags, bit_nr); 543 544 if (test_bit(bit_nr, &page->flags)) 545 __wait_on_bit(page_waitqueue(page), &wait, sync_page, 546 TASK_UNINTERRUPTIBLE); 547} 548EXPORT_SYMBOL(wait_on_page_bit); 549 550/** 551 * unlock_page - unlock a locked page 552 * @page: the page 553 * 554 * Unlocks the page and wakes up sleepers in ___wait_on_page_locked(). 555 * Also wakes sleepers in wait_on_page_writeback() because the wakeup 556 * mechananism between PageLocked pages and PageWriteback pages is shared. 557 * But that's OK - sleepers in wait_on_page_writeback() just go back to sleep. 558 * 559 * The first mb is necessary to safely close the critical section opened by the 560 * TestSetPageLocked(), the second mb is necessary to enforce ordering between 561 * the clear_bit and the read of the waitqueue (to avoid SMP races with a 562 * parallel wait_on_page_locked()). 563 */ 564void unlock_page(struct page *page) 565{ 566 smp_mb__before_clear_bit(); 567 if (!TestClearPageLocked(page)) 568 BUG(); 569 smp_mb__after_clear_bit(); 570 wake_up_page(page, PG_locked); 571} 572EXPORT_SYMBOL(unlock_page); 573 574/** 575 * end_page_writeback - end writeback against a page 576 * @page: the page 577 */ 578void end_page_writeback(struct page *page) 579{ 580 if (TestClearPageReclaim(page)) 581 rotate_reclaimable_page(page); 582 583 if (!test_clear_page_writeback(page)) 584 BUG(); 585 586 smp_mb__after_clear_bit(); 587 wake_up_page(page, PG_writeback); 588} 589EXPORT_SYMBOL(end_page_writeback); 590 591/** 592 * __lock_page - get a lock on the page, assuming we need to sleep to get it 593 * @page: the page to lock 594 * 595 * Ugly. Running sync_page() in state TASK_UNINTERRUPTIBLE is scary. If some 596 * random driver's requestfn sets TASK_RUNNING, we could busywait. However 597 * chances are that on the second loop, the block layer's plug list is empty, 598 * so sync_page() will then return in state TASK_UNINTERRUPTIBLE. 599 */ 600void __lock_page(struct page *page) 601{ 602 DEFINE_WAIT_BIT(wait, &page->flags, PG_locked); 603 604 __wait_on_bit_lock(page_waitqueue(page), &wait, sync_page, 605 TASK_UNINTERRUPTIBLE); 606} 607EXPORT_SYMBOL(__lock_page); 608 609int __lock_page_killable(struct page *page) 610{ 611 DEFINE_WAIT_BIT(wait, &page->flags, PG_locked); 612 613 return __wait_on_bit_lock(page_waitqueue(page), &wait, 614 sync_page_killable, TASK_KILLABLE); 615} 616 617/** 618 * __lock_page_nosync - get a lock on the page, without calling sync_page() 619 * @page: the page to lock 620 * 621 * Variant of lock_page that does not require the caller to hold a reference 622 * on the page's mapping. 623 */ 624void __lock_page_nosync(struct page *page) 625{ 626 DEFINE_WAIT_BIT(wait, &page->flags, PG_locked); 627 __wait_on_bit_lock(page_waitqueue(page), &wait, __sleep_on_page_lock, 628 TASK_UNINTERRUPTIBLE); 629} 630 631/** 632 * find_get_page - find and get a page reference 633 * @mapping: the address_space to search 634 * @offset: the page index 635 * 636 * Is there a pagecache struct page at the given (mapping, offset) tuple? 637 * If yes, increment its refcount and return it; if no, return NULL. 638 */ 639struct page * find_get_page(struct address_space *mapping, pgoff_t offset) 640{ 641 struct page *page; 642 643 read_lock_irq(&mapping->tree_lock); 644 page = radix_tree_lookup(&mapping->page_tree, offset); 645 if (page) 646 page_cache_get(page); 647 read_unlock_irq(&mapping->tree_lock); 648 return page; 649} 650EXPORT_SYMBOL(find_get_page); 651 652/** 653 * find_lock_page - locate, pin and lock a pagecache page 654 * @mapping: the address_space to search 655 * @offset: the page index 656 * 657 * Locates the desired pagecache page, locks it, increments its reference 658 * count and returns its address. 659 * 660 * Returns zero if the page was not present. find_lock_page() may sleep. 661 */ 662struct page *find_lock_page(struct address_space *mapping, 663 pgoff_t offset) 664{ 665 struct page *page; 666 667repeat: 668 read_lock_irq(&mapping->tree_lock); 669 page = radix_tree_lookup(&mapping->page_tree, offset); 670 if (page) { 671 page_cache_get(page); 672 if (TestSetPageLocked(page)) { 673 read_unlock_irq(&mapping->tree_lock); 674 __lock_page(page); 675 676 /* Has the page been truncated while we slept? */ 677 if (unlikely(page->mapping != mapping)) { 678 unlock_page(page); 679 page_cache_release(page); 680 goto repeat; 681 } 682 VM_BUG_ON(page->index != offset); 683 goto out; 684 } 685 } 686 read_unlock_irq(&mapping->tree_lock); 687out: 688 return page; 689} 690EXPORT_SYMBOL(find_lock_page); 691 692/** 693 * find_or_create_page - locate or add a pagecache page 694 * @mapping: the page's address_space 695 * @index: the page's index into the mapping 696 * @gfp_mask: page allocation mode 697 * 698 * Locates a page in the pagecache. If the page is not present, a new page 699 * is allocated using @gfp_mask and is added to the pagecache and to the VM's 700 * LRU list. The returned page is locked and has its reference count 701 * incremented. 702 * 703 * find_or_create_page() may sleep, even if @gfp_flags specifies an atomic 704 * allocation! 705 * 706 * find_or_create_page() returns the desired page's address, or zero on 707 * memory exhaustion. 708 */ 709struct page *find_or_create_page(struct address_space *mapping, 710 pgoff_t index, gfp_t gfp_mask) 711{ 712 struct page *page; 713 int err; 714repeat: 715 page = find_lock_page(mapping, index); 716 if (!page) { 717 page = __page_cache_alloc(gfp_mask); 718 if (!page) 719 return NULL; 720 err = add_to_page_cache_lru(page, mapping, index, gfp_mask); 721 if (unlikely(err)) { 722 page_cache_release(page); 723 page = NULL; 724 if (err == -EEXIST) 725 goto repeat; 726 } 727 } 728 return page; 729} 730EXPORT_SYMBOL(find_or_create_page); 731 732/** 733 * find_get_pages - gang pagecache lookup 734 * @mapping: The address_space to search 735 * @start: The starting page index 736 * @nr_pages: The maximum number of pages 737 * @pages: Where the resulting pages are placed 738 * 739 * find_get_pages() will search for and return a group of up to 740 * @nr_pages pages in the mapping. The pages are placed at @pages. 741 * find_get_pages() takes a reference against the returned pages. 742 * 743 * The search returns a group of mapping-contiguous pages with ascending 744 * indexes. There may be holes in the indices due to not-present pages. 745 * 746 * find_get_pages() returns the number of pages which were found. 747 */ 748unsigned find_get_pages(struct address_space *mapping, pgoff_t start, 749 unsigned int nr_pages, struct page **pages) 750{ 751 unsigned int i; 752 unsigned int ret; 753 754 read_lock_irq(&mapping->tree_lock); 755 ret = radix_tree_gang_lookup(&mapping->page_tree, 756 (void **)pages, start, nr_pages); 757 for (i = 0; i < ret; i++) 758 page_cache_get(pages[i]); 759 read_unlock_irq(&mapping->tree_lock); 760 return ret; 761} 762 763/** 764 * find_get_pages_contig - gang contiguous pagecache lookup 765 * @mapping: The address_space to search 766 * @index: The starting page index 767 * @nr_pages: The maximum number of pages 768 * @pages: Where the resulting pages are placed 769 * 770 * find_get_pages_contig() works exactly like find_get_pages(), except 771 * that the returned number of pages are guaranteed to be contiguous. 772 * 773 * find_get_pages_contig() returns the number of pages which were found. 774 */ 775unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t index, 776 unsigned int nr_pages, struct page **pages) 777{ 778 unsigned int i; 779 unsigned int ret; 780 781 read_lock_irq(&mapping->tree_lock); 782 ret = radix_tree_gang_lookup(&mapping->page_tree, 783 (void **)pages, index, nr_pages); 784 for (i = 0; i < ret; i++) { 785 if (pages[i]->mapping == NULL || pages[i]->index != index) 786 break; 787 788 page_cache_get(pages[i]); 789 index++; 790 } 791 read_unlock_irq(&mapping->tree_lock); 792 return i; 793} 794EXPORT_SYMBOL(find_get_pages_contig); 795 796/** 797 * find_get_pages_tag - find and return pages that match @tag 798 * @mapping: the address_space to search 799 * @index: the starting page index 800 * @tag: the tag index 801 * @nr_pages: the maximum number of pages 802 * @pages: where the resulting pages are placed 803 * 804 * Like find_get_pages, except we only return pages which are tagged with 805 * @tag. We update @index to index the next page for the traversal. 806 */ 807unsigned find_get_pages_tag(struct address_space *mapping, pgoff_t *index, 808 int tag, unsigned int nr_pages, struct page **pages) 809{ 810 unsigned int i; 811 unsigned int ret; 812 813 read_lock_irq(&mapping->tree_lock); 814 ret = radix_tree_gang_lookup_tag(&mapping->page_tree, 815 (void **)pages, *index, nr_pages, tag); 816 for (i = 0; i < ret; i++) 817 page_cache_get(pages[i]); 818 if (ret) 819 *index = pages[ret - 1]->index + 1; 820 read_unlock_irq(&mapping->tree_lock); 821 return ret; 822} 823EXPORT_SYMBOL(find_get_pages_tag); 824 825/** 826 * grab_cache_page_nowait - returns locked page at given index in given cache 827 * @mapping: target address_space 828 * @index: the page index 829 * 830 * Same as grab_cache_page(), but do not wait if the page is unavailable. 831 * This is intended for speculative data generators, where the data can 832 * be regenerated if the page couldn't be grabbed. This routine should 833 * be safe to call while holding the lock for another page. 834 * 835 * Clear __GFP_FS when allocating the page to avoid recursion into the fs 836 * and deadlock against the caller's locked page. 837 */ 838struct page * 839grab_cache_page_nowait(struct address_space *mapping, pgoff_t index) 840{ 841 struct page *page = find_get_page(mapping, index); 842 843 if (page) { 844 if (!TestSetPageLocked(page)) 845 return page; 846 page_cache_release(page); 847 return NULL; 848 } 849 page = __page_cache_alloc(mapping_gfp_mask(mapping) & ~__GFP_FS); 850 if (page && add_to_page_cache_lru(page, mapping, index, GFP_KERNEL)) { 851 page_cache_release(page); 852 page = NULL; 853 } 854 return page; 855} 856EXPORT_SYMBOL(grab_cache_page_nowait); 857 858/* 859 * CD/DVDs are error prone. When a medium error occurs, the driver may fail 860 * a _large_ part of the i/o request. Imagine the worst scenario: 861 * 862 * ---R__________________________________________B__________ 863 * ^ reading here ^ bad block(assume 4k) 864 * 865 * read(R) => miss => readahead(R...B) => media error => frustrating retries 866 * => failing the whole request => read(R) => read(R+1) => 867 * readahead(R+1...B+1) => bang => read(R+2) => read(R+3) => 868 * readahead(R+3...B+2) => bang => read(R+3) => read(R+4) => 869 * readahead(R+4...B+3) => bang => read(R+4) => read(R+5) => ...... 870 * 871 * It is going insane. Fix it by quickly scaling down the readahead size. 872 */ 873static void shrink_readahead_size_eio(struct file *filp, 874 struct file_ra_state *ra) 875{ 876 if (!ra->ra_pages) 877 return; 878 879 ra->ra_pages /= 4; 880} 881 882/** 883 * do_generic_file_read - generic file read routine 884 * @filp: the file to read 885 * @ppos: current file position 886 * @desc: read_descriptor 887 * @actor: read method 888 * 889 * This is a generic file read routine, and uses the 890 * mapping->a_ops->readpage() function for the actual low-level stuff. 891 * 892 * This is really ugly. But the goto's actually try to clarify some 893 * of the logic when it comes to error handling etc. 894 */ 895static void do_generic_file_read(struct file *filp, loff_t *ppos, 896 read_descriptor_t *desc, read_actor_t actor) 897{ 898 struct address_space *mapping = filp->f_mapping; 899 struct inode *inode = mapping->host; 900 struct file_ra_state *ra = &filp->f_ra; 901 pgoff_t index; 902 pgoff_t last_index; 903 pgoff_t prev_index; 904 unsigned long offset; /* offset into pagecache page */ 905 unsigned int prev_offset; 906 int error; 907 908 index = *ppos >> PAGE_CACHE_SHIFT; 909 prev_index = ra->prev_pos >> PAGE_CACHE_SHIFT; 910 prev_offset = ra->prev_pos & (PAGE_CACHE_SIZE-1); 911 last_index = (*ppos + desc->count + PAGE_CACHE_SIZE-1) >> PAGE_CACHE_SHIFT; 912 offset = *ppos & ~PAGE_CACHE_MASK; 913 914 for (;;) { 915 struct page *page; 916 pgoff_t end_index; 917 loff_t isize; 918 unsigned long nr, ret; 919 920 cond_resched(); 921find_page: 922 page = find_get_page(mapping, index); 923 if (!page) { 924 page_cache_sync_readahead(mapping, 925 ra, filp, 926 index, last_index - index); 927 page = find_get_page(mapping, index); 928 if (unlikely(page == NULL)) 929 goto no_cached_page; 930 } 931 if (PageReadahead(page)) { 932 page_cache_async_readahead(mapping, 933 ra, filp, page, 934 index, last_index - index); 935 } 936 if (!PageUptodate(page)) 937 goto page_not_up_to_date; 938page_ok: 939 /* 940 * i_size must be checked after we know the page is Uptodate. 941 * 942 * Checking i_size after the check allows us to calculate 943 * the correct value for "nr", which means the zero-filled 944 * part of the page is not copied back to userspace (unless 945 * another truncate extends the file - this is desired though). 946 */ 947 948 isize = i_size_read(inode); 949 end_index = (isize - 1) >> PAGE_CACHE_SHIFT; 950 if (unlikely(!isize || index > end_index)) { 951 page_cache_release(page); 952 goto out; 953 } 954 955 /* nr is the maximum number of bytes to copy from this page */ 956 nr = PAGE_CACHE_SIZE; 957 if (index == end_index) { 958 nr = ((isize - 1) & ~PAGE_CACHE_MASK) + 1; 959 if (nr <= offset) { 960 page_cache_release(page); 961 goto out; 962 } 963 } 964 nr = nr - offset; 965 966 /* If users can be writing to this page using arbitrary 967 * virtual addresses, take care about potential aliasing 968 * before reading the page on the kernel side. 969 */ 970 if (mapping_writably_mapped(mapping)) 971 flush_dcache_page(page); 972 973 /* 974 * When a sequential read accesses a page several times, 975 * only mark it as accessed the first time. 976 */ 977 if (prev_index != index || offset != prev_offset) 978 mark_page_accessed(page); 979 prev_index = index; 980 981 /* 982 * Ok, we have the page, and it's up-to-date, so 983 * now we can copy it to user space... 984 * 985 * The actor routine returns how many bytes were actually used.. 986 * NOTE! This may not be the same as how much of a user buffer 987 * we filled up (we may be padding etc), so we can only update 988 * "pos" here (the actor routine has to update the user buffer 989 * pointers and the remaining count). 990 */ 991 ret = actor(desc, page, offset, nr); 992 offset += ret; 993 index += offset >> PAGE_CACHE_SHIFT; 994 offset &= ~PAGE_CACHE_MASK; 995 prev_offset = offset; 996 997 page_cache_release(page); 998 if (ret == nr && desc->count) 999 continue; 1000 goto out; 1001 1002page_not_up_to_date: 1003 /* Get exclusive access to the page ... */ 1004 if (lock_page_killable(page)) 1005 goto readpage_eio; 1006 1007 /* Did it get truncated before we got the lock? */ 1008 if (!page->mapping) { 1009 unlock_page(page); 1010 page_cache_release(page); 1011 continue; 1012 } 1013 1014 /* Did somebody else fill it already? */ 1015 if (PageUptodate(page)) { 1016 unlock_page(page); 1017 goto page_ok; 1018 } 1019 1020readpage: 1021 /* Start the actual read. The read will unlock the page. */ 1022 error = mapping->a_ops->readpage(filp, page); 1023 1024 if (unlikely(error)) { 1025 if (error == AOP_TRUNCATED_PAGE) { 1026 page_cache_release(page); 1027 goto find_page; 1028 } 1029 goto readpage_error; 1030 } 1031 1032 if (!PageUptodate(page)) { 1033 if (lock_page_killable(page)) 1034 goto readpage_eio; 1035 if (!PageUptodate(page)) { 1036 if (page->mapping == NULL) { 1037 /* 1038 * invalidate_inode_pages got it 1039 */ 1040 unlock_page(page); 1041 page_cache_release(page); 1042 goto find_page; 1043 } 1044 unlock_page(page); 1045 shrink_readahead_size_eio(filp, ra); 1046 goto readpage_eio; 1047 } 1048 unlock_page(page); 1049 } 1050 1051 goto page_ok; 1052 1053readpage_eio: 1054 error = -EIO; 1055readpage_error: 1056 /* UHHUH! A synchronous read error occurred. Report it */ 1057 desc->error = error; 1058 page_cache_release(page); 1059 goto out; 1060 1061no_cached_page: 1062 /* 1063 * Ok, it wasn't cached, so we need to create a new 1064 * page.. 1065 */ 1066 page = page_cache_alloc_cold(mapping); 1067 if (!page) { 1068 desc->error = -ENOMEM; 1069 goto out; 1070 } 1071 error = add_to_page_cache_lru(page, mapping, 1072 index, GFP_KERNEL); 1073 if (error) { 1074 page_cache_release(page); 1075 if (error == -EEXIST) 1076 goto find_page; 1077 desc->error = error; 1078 goto out; 1079 } 1080 goto readpage; 1081 } 1082 1083out: 1084 ra->prev_pos = prev_index; 1085 ra->prev_pos <<= PAGE_CACHE_SHIFT; 1086 ra->prev_pos |= prev_offset; 1087 1088 *ppos = ((loff_t)index << PAGE_CACHE_SHIFT) + offset; 1089 if (filp) 1090 file_accessed(filp); 1091} 1092 1093int file_read_actor(read_descriptor_t *desc, struct page *page, 1094 unsigned long offset, unsigned long size) 1095{ 1096 char *kaddr; 1097 unsigned long left, count = desc->count; 1098 1099 if (size > count) 1100 size = count; 1101 1102 /* 1103 * Faults on the destination of a read are common, so do it before 1104 * taking the kmap. 1105 */ 1106 if (!fault_in_pages_writeable(desc->arg.buf, size)) { 1107 kaddr = kmap_atomic(page, KM_USER0); 1108 left = __copy_to_user_inatomic(desc->arg.buf, 1109 kaddr + offset, size); 1110 kunmap_atomic(kaddr, KM_USER0); 1111 if (left == 0) 1112 goto success; 1113 } 1114 1115 /* Do it the slow way */ 1116 kaddr = kmap(page); 1117 left = __copy_to_user(desc->arg.buf, kaddr + offset, size); 1118 kunmap(page); 1119 1120 if (left) { 1121 size -= left; 1122 desc->error = -EFAULT; 1123 } 1124success: 1125 desc->count = count - size; 1126 desc->written += size; 1127 desc->arg.buf += size; 1128 return size; 1129} 1130 1131/* 1132 * Performs necessary checks before doing a write 1133 * @iov: io vector request 1134 * @nr_segs: number of segments in the iovec 1135 * @count: number of bytes to write 1136 * @access_flags: type of access: %VERIFY_READ or %VERIFY_WRITE 1137 * 1138 * Adjust number of segments and amount of bytes to write (nr_segs should be 1139 * properly initialized first). Returns appropriate error code that caller 1140 * should return or zero in case that write should be allowed. 1141 */ 1142int generic_segment_checks(const struct iovec *iov, 1143 unsigned long *nr_segs, size_t *count, int access_flags) 1144{ 1145 unsigned long seg; 1146 size_t cnt = 0; 1147 for (seg = 0; seg < *nr_segs; seg++) { 1148 const struct iovec *iv = &iov[seg]; 1149 1150 /* 1151 * If any segment has a negative length, or the cumulative 1152 * length ever wraps negative then return -EINVAL. 1153 */ 1154 cnt += iv->iov_len; 1155 if (unlikely((ssize_t)(cnt|iv->iov_len) < 0)) 1156 return -EINVAL; 1157 if (access_ok(access_flags, iv->iov_base, iv->iov_len)) 1158 continue; 1159 if (seg == 0) 1160 return -EFAULT; 1161 *nr_segs = seg; 1162 cnt -= iv->iov_len; /* This segment is no good */ 1163 break; 1164 } 1165 *count = cnt; 1166 return 0; 1167} 1168EXPORT_SYMBOL(generic_segment_checks); 1169 1170/** 1171 * generic_file_aio_read - generic filesystem read routine 1172 * @iocb: kernel I/O control block 1173 * @iov: io vector request 1174 * @nr_segs: number of segments in the iovec 1175 * @pos: current file position 1176 * 1177 * This is the "read()" routine for all filesystems 1178 * that can use the page cache directly. 1179 */ 1180ssize_t 1181generic_file_aio_read(struct kiocb *iocb, const struct iovec *iov, 1182 unsigned long nr_segs, loff_t pos) 1183{ 1184 struct file *filp = iocb->ki_filp; 1185 ssize_t retval; 1186 unsigned long seg; 1187 size_t count; 1188 loff_t *ppos = &iocb->ki_pos; 1189 1190 count = 0; 1191 retval = generic_segment_checks(iov, &nr_segs, &count, VERIFY_WRITE); 1192 if (retval) 1193 return retval; 1194 1195 /* coalesce the iovecs and go direct-to-BIO for O_DIRECT */ 1196 if (filp->f_flags & O_DIRECT) { 1197 loff_t size; 1198 struct address_space *mapping; 1199 struct inode *inode; 1200 1201 mapping = filp->f_mapping; 1202 inode = mapping->host; 1203 retval = 0; 1204 if (!count) 1205 goto out; /* skip atime */ 1206 size = i_size_read(inode); 1207 if (pos < size) { 1208 retval = generic_file_direct_IO(READ, iocb, 1209 iov, pos, nr_segs); 1210 if (retval > 0) 1211 *ppos = pos + retval; 1212 } 1213 if (likely(retval != 0)) { 1214 file_accessed(filp); 1215 goto out; 1216 } 1217 } 1218 1219 retval = 0; 1220 if (count) { 1221 for (seg = 0; seg < nr_segs; seg++) { 1222 read_descriptor_t desc; 1223 1224 desc.written = 0; 1225 desc.arg.buf = iov[seg].iov_base; 1226 desc.count = iov[seg].iov_len; 1227 if (desc.count == 0) 1228 continue; 1229 desc.error = 0; 1230 do_generic_file_read(filp,ppos,&desc,file_read_actor); 1231 retval += desc.written; 1232 if (desc.error) { 1233 retval = retval ?: desc.error; 1234 break; 1235 } 1236 if (desc.count > 0) 1237 break; 1238 } 1239 } 1240out: 1241 return retval; 1242} 1243EXPORT_SYMBOL(generic_file_aio_read); 1244 1245static ssize_t 1246do_readahead(struct address_space *mapping, struct file *filp, 1247 pgoff_t index, unsigned long nr) 1248{ 1249 if (!mapping || !mapping->a_ops || !mapping->a_ops->readpage) 1250 return -EINVAL; 1251 1252 force_page_cache_readahead(mapping, filp, index, 1253 max_sane_readahead(nr)); 1254 return 0; 1255} 1256 1257asmlinkage ssize_t sys_readahead(int fd, loff_t offset, size_t count) 1258{ 1259 ssize_t ret; 1260 struct file *file; 1261 1262 ret = -EBADF; 1263 file = fget(fd); 1264 if (file) { 1265 if (file->f_mode & FMODE_READ) { 1266 struct address_space *mapping = file->f_mapping; 1267 pgoff_t start = offset >> PAGE_CACHE_SHIFT; 1268 pgoff_t end = (offset + count - 1) >> PAGE_CACHE_SHIFT; 1269 unsigned long len = end - start + 1; 1270 ret = do_readahead(mapping, file, start, len); 1271 } 1272 fput(file); 1273 } 1274 return ret; 1275} 1276 1277#ifdef CONFIG_MMU 1278/** 1279 * page_cache_read - adds requested page to the page cache if not already there 1280 * @file: file to read 1281 * @offset: page index 1282 * 1283 * This adds the requested page to the page cache if it isn't already there, 1284 * and schedules an I/O to read in its contents from disk. 1285 */ 1286static int page_cache_read(struct file *file, pgoff_t offset) 1287{ 1288 struct address_space *mapping = file->f_mapping; 1289 struct page *page; 1290 int ret; 1291 1292 do { 1293 page = page_cache_alloc_cold(mapping); 1294 if (!page) 1295 return -ENOMEM; 1296 1297 ret = add_to_page_cache_lru(page, mapping, offset, GFP_KERNEL); 1298 if (ret == 0) 1299 ret = mapping->a_ops->readpage(file, page); 1300 else if (ret == -EEXIST) 1301 ret = 0; /* losing race to add is OK */ 1302 1303 page_cache_release(page); 1304 1305 } while (ret == AOP_TRUNCATED_PAGE); 1306 1307 return ret; 1308} 1309 1310#define MMAP_LOTSAMISS (100) 1311 1312/** 1313 * filemap_fault - read in file data for page fault handling 1314 * @vma: vma in which the fault was taken 1315 * @vmf: struct vm_fault containing details of the fault 1316 * 1317 * filemap_fault() is invoked via the vma operations vector for a 1318 * mapped memory region to read in file data during a page fault. 1319 * 1320 * The goto's are kind of ugly, but this streamlines the normal case of having 1321 * it in the page cache, and handles the special cases reasonably without 1322 * having a lot of duplicated code. 1323 */ 1324int filemap_fault(struct vm_area_struct *vma, struct vm_fault *vmf) 1325{ 1326 int error; 1327 struct file *file = vma->vm_file; 1328 struct address_space *mapping = file->f_mapping; 1329 struct file_ra_state *ra = &file->f_ra; 1330 struct inode *inode = mapping->host; 1331 struct page *page; 1332 pgoff_t size; 1333 int did_readaround = 0; 1334 int ret = 0; 1335 1336 size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT; 1337 if (vmf->pgoff >= size) 1338 return VM_FAULT_SIGBUS; 1339 1340 /* If we don't want any read-ahead, don't bother */ 1341 if (VM_RandomReadHint(vma)) 1342 goto no_cached_page; 1343 1344 /* 1345 * Do we have something in the page cache already? 1346 */ 1347retry_find: 1348 page = find_lock_page(mapping, vmf->pgoff); 1349 /* 1350 * For sequential accesses, we use the generic readahead logic. 1351 */ 1352 if (VM_SequentialReadHint(vma)) { 1353 if (!page) { 1354 page_cache_sync_readahead(mapping, ra, file, 1355 vmf->pgoff, 1); 1356 page = find_lock_page(mapping, vmf->pgoff); 1357 if (!page) 1358 goto no_cached_page; 1359 } 1360 if (PageReadahead(page)) { 1361 page_cache_async_readahead(mapping, ra, file, page, 1362 vmf->pgoff, 1); 1363 } 1364 } 1365 1366 if (!page) { 1367 unsigned long ra_pages; 1368 1369 ra->mmap_miss++; 1370 1371 /* 1372 * Do we miss much more than hit in this file? If so, 1373 * stop bothering with read-ahead. It will only hurt. 1374 */ 1375 if (ra->mmap_miss > MMAP_LOTSAMISS) 1376 goto no_cached_page; 1377 1378 /* 1379 * To keep the pgmajfault counter straight, we need to 1380 * check did_readaround, as this is an inner loop. 1381 */ 1382 if (!did_readaround) { 1383 ret = VM_FAULT_MAJOR; 1384 count_vm_event(PGMAJFAULT); 1385 } 1386 did_readaround = 1; 1387 ra_pages = max_sane_readahead(file->f_ra.ra_pages); 1388 if (ra_pages) { 1389 pgoff_t start = 0; 1390 1391 if (vmf->pgoff > ra_pages / 2) 1392 start = vmf->pgoff - ra_pages / 2; 1393 do_page_cache_readahead(mapping, file, start, ra_pages); 1394 } 1395 page = find_lock_page(mapping, vmf->pgoff); 1396 if (!page) 1397 goto no_cached_page; 1398 } 1399 1400 if (!did_readaround) 1401 ra->mmap_miss--; 1402 1403 /* 1404 * We have a locked page in the page cache, now we need to check 1405 * that it's up-to-date. If not, it is going to be due to an error. 1406 */ 1407 if (unlikely(!PageUptodate(page))) 1408 goto page_not_uptodate; 1409 1410 /* Must recheck i_size under page lock */ 1411 size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT; 1412 if (unlikely(vmf->pgoff >= size)) { 1413 unlock_page(page); 1414 page_cache_release(page); 1415 return VM_FAULT_SIGBUS; 1416 } 1417 1418 /* 1419 * Found the page and have a reference on it. 1420 */ 1421 mark_page_accessed(page); 1422 ra->prev_pos = (loff_t)page->index << PAGE_CACHE_SHIFT; 1423 vmf->page = page; 1424 return ret | VM_FAULT_LOCKED; 1425 1426no_cached_page: 1427 /* 1428 * We're only likely to ever get here if MADV_RANDOM is in 1429 * effect. 1430 */ 1431 error = page_cache_read(file, vmf->pgoff); 1432 1433 /* 1434 * The page we want has now been added to the page cache. 1435 * In the unlikely event that someone removed it in the 1436 * meantime, we'll just come back here and read it again. 1437 */ 1438 if (error >= 0) 1439 goto retry_find; 1440 1441 /* 1442 * An error return from page_cache_read can result if the 1443 * system is low on memory, or a problem occurs while trying 1444 * to schedule I/O. 1445 */ 1446 if (error == -ENOMEM) 1447 return VM_FAULT_OOM; 1448 return VM_FAULT_SIGBUS; 1449 1450page_not_uptodate: 1451 /* IO error path */ 1452 if (!did_readaround) { 1453 ret = VM_FAULT_MAJOR; 1454 count_vm_event(PGMAJFAULT); 1455 } 1456 1457 /* 1458 * Umm, take care of errors if the page isn't up-to-date. 1459 * Try to re-read it _once_. We do this synchronously, 1460 * because there really aren't any performance issues here 1461 * and we need to check for errors. 1462 */ 1463 ClearPageError(page); 1464 error = mapping->a_ops->readpage(file, page); 1465 if (!error) { 1466 wait_on_page_locked(page); 1467 if (!PageUptodate(page)) 1468 error = -EIO; 1469 } 1470 page_cache_release(page); 1471 1472 if (!error || error == AOP_TRUNCATED_PAGE) 1473 goto retry_find; 1474 1475 /* Things didn't work out. Return zero to tell the mm layer so. */ 1476 shrink_readahead_size_eio(file, ra); 1477 return VM_FAULT_SIGBUS; 1478} 1479EXPORT_SYMBOL(filemap_fault); 1480 1481struct vm_operations_struct generic_file_vm_ops = { 1482 .fault = filemap_fault, 1483}; 1484 1485/* This is used for a general mmap of a disk file */ 1486 1487int generic_file_mmap(struct file * file, struct vm_area_struct * vma) 1488{ 1489 struct address_space *mapping = file->f_mapping; 1490 1491 if (!mapping->a_ops->readpage) 1492 return -ENOEXEC; 1493 file_accessed(file); 1494 vma->vm_ops = &generic_file_vm_ops; 1495 vma->vm_flags |= VM_CAN_NONLINEAR; 1496 return 0; 1497} 1498 1499/* 1500 * This is for filesystems which do not implement ->writepage. 1501 */ 1502int generic_file_readonly_mmap(struct file *file, struct vm_area_struct *vma) 1503{ 1504 if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_MAYWRITE)) 1505 return -EINVAL; 1506 return generic_file_mmap(file, vma); 1507} 1508#else 1509int generic_file_mmap(struct file * file, struct vm_area_struct * vma) 1510{ 1511 return -ENOSYS; 1512} 1513int generic_file_readonly_mmap(struct file * file, struct vm_area_struct * vma) 1514{ 1515 return -ENOSYS; 1516} 1517#endif /* CONFIG_MMU */ 1518 1519EXPORT_SYMBOL(generic_file_mmap); 1520EXPORT_SYMBOL(generic_file_readonly_mmap); 1521 1522static struct page *__read_cache_page(struct address_space *mapping, 1523 pgoff_t index, 1524 int (*filler)(void *,struct page*), 1525 void *data) 1526{ 1527 struct page *page; 1528 int err; 1529repeat: 1530 page = find_get_page(mapping, index); 1531 if (!page) { 1532 page = page_cache_alloc_cold(mapping); 1533 if (!page) 1534 return ERR_PTR(-ENOMEM); 1535 err = add_to_page_cache_lru(page, mapping, index, GFP_KERNEL); 1536 if (unlikely(err)) { 1537 page_cache_release(page); 1538 if (err == -EEXIST) 1539 goto repeat; 1540 /* Presumably ENOMEM for radix tree node */ 1541 return ERR_PTR(err); 1542 } 1543 err = filler(data, page); 1544 if (err < 0) { 1545 page_cache_release(page); 1546 page = ERR_PTR(err); 1547 } 1548 } 1549 return page; 1550} 1551 1552/** 1553 * read_cache_page_async - read into page cache, fill it if needed 1554 * @mapping: the page's address_space 1555 * @index: the page index 1556 * @filler: function to perform the read 1557 * @data: destination for read data 1558 * 1559 * Same as read_cache_page, but don't wait for page to become unlocked 1560 * after submitting it to the filler. 1561 * 1562 * Read into the page cache. If a page already exists, and PageUptodate() is 1563 * not set, try to fill the page but don't wait for it to become unlocked. 1564 * 1565 * If the page does not get brought uptodate, return -EIO. 1566 */ 1567struct page *read_cache_page_async(struct address_space *mapping, 1568 pgoff_t index, 1569 int (*filler)(void *,struct page*), 1570 void *data) 1571{ 1572 struct page *page; 1573 int err; 1574 1575retry: 1576 page = __read_cache_page(mapping, index, filler, data); 1577 if (IS_ERR(page)) 1578 return page; 1579 if (PageUptodate(page)) 1580 goto out; 1581 1582 lock_page(page); 1583 if (!page->mapping) { 1584 unlock_page(page); 1585 page_cache_release(page); 1586 goto retry; 1587 } 1588 if (PageUptodate(page)) { 1589 unlock_page(page); 1590 goto out; 1591 } 1592 err = filler(data, page); 1593 if (err < 0) { 1594 page_cache_release(page); 1595 return ERR_PTR(err); 1596 } 1597out: 1598 mark_page_accessed(page); 1599 return page; 1600} 1601EXPORT_SYMBOL(read_cache_page_async); 1602 1603/** 1604 * read_cache_page - read into page cache, fill it if needed 1605 * @mapping: the page's address_space 1606 * @index: the page index 1607 * @filler: function to perform the read 1608 * @data: destination for read data 1609 * 1610 * Read into the page cache. If a page already exists, and PageUptodate() is 1611 * not set, try to fill the page then wait for it to become unlocked. 1612 * 1613 * If the page does not get brought uptodate, return -EIO. 1614 */ 1615struct page *read_cache_page(struct address_space *mapping, 1616 pgoff_t index, 1617 int (*filler)(void *,struct page*), 1618 void *data) 1619{ 1620 struct page *page; 1621 1622 page = read_cache_page_async(mapping, index, filler, data); 1623 if (IS_ERR(page)) 1624 goto out; 1625 wait_on_page_locked(page); 1626 if (!PageUptodate(page)) { 1627 page_cache_release(page); 1628 page = ERR_PTR(-EIO); 1629 } 1630 out: 1631 return page; 1632} 1633EXPORT_SYMBOL(read_cache_page); 1634 1635/* 1636 * The logic we want is 1637 * 1638 * if suid or (sgid and xgrp) 1639 * remove privs 1640 */ 1641int should_remove_suid(struct dentry *dentry) 1642{ 1643 mode_t mode = dentry->d_inode->i_mode; 1644 int kill = 0; 1645 1646 /* suid always must be killed */ 1647 if (unlikely(mode & S_ISUID)) 1648 kill = ATTR_KILL_SUID; 1649 1650 /* 1651 * sgid without any exec bits is just a mandatory locking mark; leave 1652 * it alone. If some exec bits are set, it's a real sgid; kill it. 1653 */ 1654 if (unlikely((mode & S_ISGID) && (mode & S_IXGRP))) 1655 kill |= ATTR_KILL_SGID; 1656 1657 if (unlikely(kill && !capable(CAP_FSETID))) 1658 return kill; 1659 1660 return 0; 1661} 1662EXPORT_SYMBOL(should_remove_suid); 1663 1664static int __remove_suid(struct dentry *dentry, int kill) 1665{ 1666 struct iattr newattrs; 1667 1668 newattrs.ia_valid = ATTR_FORCE | kill; 1669 return notify_change(dentry, &newattrs); 1670} 1671 1672int remove_suid(struct dentry *dentry) 1673{ 1674 int killsuid = should_remove_suid(dentry); 1675 int killpriv = security_inode_need_killpriv(dentry); 1676 int error = 0; 1677 1678 if (killpriv < 0) 1679 return killpriv; 1680 if (killpriv) 1681 error = security_inode_killpriv(dentry); 1682 if (!error && killsuid) 1683 error = __remove_suid(dentry, killsuid); 1684 1685 return error; 1686} 1687EXPORT_SYMBOL(remove_suid); 1688 1689static size_t __iovec_copy_from_user_inatomic(char *vaddr, 1690 const struct iovec *iov, size_t base, size_t bytes) 1691{ 1692 size_t copied = 0, left = 0; 1693 1694 while (bytes) { 1695 char __user *buf = iov->iov_base + base; 1696 int copy = min(bytes, iov->iov_len - base); 1697 1698 base = 0; 1699 left = __copy_from_user_inatomic_nocache(vaddr, buf, copy); 1700 copied += copy; 1701 bytes -= copy; 1702 vaddr += copy; 1703 iov++; 1704 1705 if (unlikely(left)) 1706 break; 1707 } 1708 return copied - left; 1709} 1710 1711/* 1712 * Copy as much as we can into the page and return the number of bytes which 1713 * were sucessfully copied. If a fault is encountered then return the number of 1714 * bytes which were copied. 1715 */ 1716size_t iov_iter_copy_from_user_atomic(struct page *page, 1717 struct iov_iter *i, unsigned long offset, size_t bytes) 1718{ 1719 char *kaddr; 1720 size_t copied; 1721 1722 BUG_ON(!in_atomic()); 1723 kaddr = kmap_atomic(page, KM_USER0); 1724 if (likely(i->nr_segs == 1)) { 1725 int left; 1726 char __user *buf = i->iov->iov_base + i->iov_offset; 1727 left = __copy_from_user_inatomic_nocache(kaddr + offset, 1728 buf, bytes); 1729 copied = bytes - left; 1730 } else { 1731 copied = __iovec_copy_from_user_inatomic(kaddr + offset, 1732 i->iov, i->iov_offset, bytes); 1733 } 1734 kunmap_atomic(kaddr, KM_USER0); 1735 1736 return copied; 1737} 1738EXPORT_SYMBOL(iov_iter_copy_from_user_atomic); 1739 1740/* 1741 * This has the same sideeffects and return value as 1742 * iov_iter_copy_from_user_atomic(). 1743 * The difference is that it attempts to resolve faults. 1744 * Page must not be locked. 1745 */ 1746size_t iov_iter_copy_from_user(struct page *page, 1747 struct iov_iter *i, unsigned long offset, size_t bytes) 1748{ 1749 char *kaddr; 1750 size_t copied; 1751 1752 kaddr = kmap(page); 1753 if (likely(i->nr_segs == 1)) { 1754 int left; 1755 char __user *buf = i->iov->iov_base + i->iov_offset; 1756 left = __copy_from_user_nocache(kaddr + offset, buf, bytes); 1757 copied = bytes - left; 1758 } else { 1759 copied = __iovec_copy_from_user_inatomic(kaddr + offset, 1760 i->iov, i->iov_offset, bytes); 1761 } 1762 kunmap(page); 1763 return copied; 1764} 1765EXPORT_SYMBOL(iov_iter_copy_from_user); 1766 1767void iov_iter_advance(struct iov_iter *i, size_t bytes) 1768{ 1769 BUG_ON(i->count < bytes); 1770 1771 if (likely(i->nr_segs == 1)) { 1772 i->iov_offset += bytes; 1773 i->count -= bytes; 1774 } else { 1775 const struct iovec *iov = i->iov; 1776 size_t base = i->iov_offset; 1777 1778 /* 1779 * The !iov->iov_len check ensures we skip over unlikely 1780 * zero-length segments (without overruning the iovec). 1781 */ 1782 while (bytes || unlikely(!iov->iov_len && i->count)) { 1783 int copy; 1784 1785 copy = min(bytes, iov->iov_len - base); 1786 BUG_ON(!i->count || i->count < copy); 1787 i->count -= copy; 1788 bytes -= copy; 1789 base += copy; 1790 if (iov->iov_len == base) { 1791 iov++; 1792 base = 0; 1793 } 1794 } 1795 i->iov = iov; 1796 i->iov_offset = base; 1797 } 1798} 1799EXPORT_SYMBOL(iov_iter_advance); 1800 1801/* 1802 * Fault in the first iovec of the given iov_iter, to a maximum length 1803 * of bytes. Returns 0 on success, or non-zero if the memory could not be 1804 * accessed (ie. because it is an invalid address). 1805 * 1806 * writev-intensive code may want this to prefault several iovecs -- that 1807 * would be possible (callers must not rely on the fact that _only_ the 1808 * first iovec will be faulted with the current implementation). 1809 */ 1810int iov_iter_fault_in_readable(struct iov_iter *i, size_t bytes) 1811{ 1812 char __user *buf = i->iov->iov_base + i->iov_offset; 1813 bytes = min(bytes, i->iov->iov_len - i->iov_offset); 1814 return fault_in_pages_readable(buf, bytes); 1815} 1816EXPORT_SYMBOL(iov_iter_fault_in_readable); 1817 1818/* 1819 * Return the count of just the current iov_iter segment. 1820 */ 1821size_t iov_iter_single_seg_count(struct iov_iter *i) 1822{ 1823 const struct iovec *iov = i->iov; 1824 if (i->nr_segs == 1) 1825 return i->count; 1826 else 1827 return min(i->count, iov->iov_len - i->iov_offset); 1828} 1829EXPORT_SYMBOL(iov_iter_single_seg_count); 1830 1831/* 1832 * Performs necessary checks before doing a write 1833 * 1834 * Can adjust writing position or amount of bytes to write. 1835 * Returns appropriate error code that caller should return or 1836 * zero in case that write should be allowed. 1837 */ 1838inline int generic_write_checks(struct file *file, loff_t *pos, size_t *count, int isblk) 1839{ 1840 struct inode *inode = file->f_mapping->host; 1841 unsigned long limit = current->signal->rlim[RLIMIT_FSIZE].rlim_cur; 1842 1843 if (unlikely(*pos < 0)) 1844 return -EINVAL; 1845 1846 if (!isblk) { 1847 /* FIXME: this is for backwards compatibility with 2.4 */ 1848 if (file->f_flags & O_APPEND) 1849 *pos = i_size_read(inode); 1850 1851 if (limit != RLIM_INFINITY) { 1852 if (*pos >= limit) { 1853 send_sig(SIGXFSZ, current, 0); 1854 return -EFBIG; 1855 } 1856 if (*count > limit - (typeof(limit))*pos) { 1857 *count = limit - (typeof(limit))*pos; 1858 } 1859 } 1860 } 1861 1862 /* 1863 * LFS rule 1864 */ 1865 if (unlikely(*pos + *count > MAX_NON_LFS && 1866 !(file->f_flags & O_LARGEFILE))) { 1867 if (*pos >= MAX_NON_LFS) { 1868 return -EFBIG; 1869 } 1870 if (*count > MAX_NON_LFS - (unsigned long)*pos) { 1871 *count = MAX_NON_LFS - (unsigned long)*pos; 1872 } 1873 } 1874 1875 /* 1876 * Are we about to exceed the fs block limit ? 1877 * 1878 * If we have written data it becomes a short write. If we have 1879 * exceeded without writing data we send a signal and return EFBIG. 1880 * Linus frestrict idea will clean these up nicely.. 1881 */ 1882 if (likely(!isblk)) { 1883 if (unlikely(*pos >= inode->i_sb->s_maxbytes)) { 1884 if (*count || *pos > inode->i_sb->s_maxbytes) { 1885 return -EFBIG; 1886 } 1887 /* zero-length writes at ->s_maxbytes are OK */ 1888 } 1889 1890 if (unlikely(*pos + *count > inode->i_sb->s_maxbytes)) 1891 *count = inode->i_sb->s_maxbytes - *pos; 1892 } else { 1893#ifdef CONFIG_BLOCK 1894 loff_t isize; 1895 if (bdev_read_only(I_BDEV(inode))) 1896 return -EPERM; 1897 isize = i_size_read(inode); 1898 if (*pos >= isize) { 1899 if (*count || *pos > isize) 1900 return -ENOSPC; 1901 } 1902 1903 if (*pos + *count > isize) 1904 *count = isize - *pos; 1905#else 1906 return -EPERM; 1907#endif 1908 } 1909 return 0; 1910} 1911EXPORT_SYMBOL(generic_write_checks); 1912 1913int pagecache_write_begin(struct file *file, struct address_space *mapping, 1914 loff_t pos, unsigned len, unsigned flags, 1915 struct page **pagep, void **fsdata) 1916{ 1917 const struct address_space_operations *aops = mapping->a_ops; 1918 1919 if (aops->write_begin) { 1920 return aops->write_begin(file, mapping, pos, len, flags, 1921 pagep, fsdata); 1922 } else { 1923 int ret; 1924 pgoff_t index = pos >> PAGE_CACHE_SHIFT; 1925 unsigned offset = pos & (PAGE_CACHE_SIZE - 1); 1926 struct inode *inode = mapping->host; 1927 struct page *page; 1928again: 1929 page = __grab_cache_page(mapping, index); 1930 *pagep = page; 1931 if (!page) 1932 return -ENOMEM; 1933 1934 if (flags & AOP_FLAG_UNINTERRUPTIBLE && !PageUptodate(page)) { 1935 /* 1936 * There is no way to resolve a short write situation 1937 * for a !Uptodate page (except by double copying in 1938 * the caller done by generic_perform_write_2copy). 1939 * 1940 * Instead, we have to bring it uptodate here. 1941 */ 1942 ret = aops->readpage(file, page); 1943 page_cache_release(page); 1944 if (ret) { 1945 if (ret == AOP_TRUNCATED_PAGE) 1946 goto again; 1947 return ret; 1948 } 1949 goto again; 1950 } 1951 1952 ret = aops->prepare_write(file, page, offset, offset+len); 1953 if (ret) { 1954 unlock_page(page); 1955 page_cache_release(page); 1956 if (pos + len > inode->i_size) 1957 vmtruncate(inode, inode->i_size); 1958 } 1959 return ret; 1960 } 1961} 1962EXPORT_SYMBOL(pagecache_write_begin); 1963 1964int pagecache_write_end(struct file *file, struct address_space *mapping, 1965 loff_t pos, unsigned len, unsigned copied, 1966 struct page *page, void *fsdata) 1967{ 1968 const struct address_space_operations *aops = mapping->a_ops; 1969 int ret; 1970 1971 if (aops->write_end) { 1972 mark_page_accessed(page); 1973 ret = aops->write_end(file, mapping, pos, len, copied, 1974 page, fsdata); 1975 } else { 1976 unsigned offset = pos & (PAGE_CACHE_SIZE - 1); 1977 struct inode *inode = mapping->host; 1978 1979 flush_dcache_page(page); 1980 ret = aops->commit_write(file, page, offset, offset+len); 1981 unlock_page(page); 1982 mark_page_accessed(page); 1983 page_cache_release(page); 1984 1985 if (ret < 0) { 1986 if (pos + len > inode->i_size) 1987 vmtruncate(inode, inode->i_size); 1988 } else if (ret > 0) 1989 ret = min_t(size_t, copied, ret); 1990 else 1991 ret = copied; 1992 } 1993 1994 return ret; 1995} 1996EXPORT_SYMBOL(pagecache_write_end); 1997 1998ssize_t 1999generic_file_direct_write(struct kiocb *iocb, const struct iovec *iov, 2000 unsigned long *nr_segs, loff_t pos, loff_t *ppos, 2001 size_t count, size_t ocount) 2002{ 2003 struct file *file = iocb->ki_filp; 2004 struct address_space *mapping = file->f_mapping; 2005 struct inode *inode = mapping->host; 2006 ssize_t written; 2007 2008 if (count != ocount) 2009 *nr_segs = iov_shorten((struct iovec *)iov, *nr_segs, count); 2010 2011 written = generic_file_direct_IO(WRITE, iocb, iov, pos, *nr_segs); 2012 if (written > 0) { 2013 loff_t end = pos + written; 2014 if (end > i_size_read(inode) && !S_ISBLK(inode->i_mode)) { 2015 i_size_write(inode, end); 2016 mark_inode_dirty(inode); 2017 } 2018 *ppos = end; 2019 } 2020 2021 /* 2022 * Sync the fs metadata but not the minor inode changes and 2023 * of course not the data as we did direct DMA for the IO. 2024 * i_mutex is held, which protects generic_osync_inode() from 2025 * livelocking. AIO O_DIRECT ops attempt to sync metadata here. 2026 */ 2027 if ((written >= 0 || written == -EIOCBQUEUED) && 2028 ((file->f_flags & O_SYNC) || IS_SYNC(inode))) { 2029 int err = generic_osync_inode(inode, mapping, OSYNC_METADATA); 2030 if (err < 0) 2031 written = err; 2032 } 2033 return written; 2034} 2035EXPORT_SYMBOL(generic_file_direct_write); 2036 2037/* 2038 * Find or create a page at the given pagecache position. Return the locked 2039 * page. This function is specifically for buffered writes. 2040 */ 2041struct page *__grab_cache_page(struct address_space *mapping, pgoff_t index) 2042{ 2043 int status; 2044 struct page *page; 2045repeat: 2046 page = find_lock_page(mapping, index); 2047 if (likely(page)) 2048 return page; 2049 2050 page = page_cache_alloc(mapping); 2051 if (!page) 2052 return NULL; 2053 status = add_to_page_cache_lru(page, mapping, index, GFP_KERNEL); 2054 if (unlikely(status)) { 2055 page_cache_release(page); 2056 if (status == -EEXIST) 2057 goto repeat; 2058 return NULL; 2059 } 2060 return page; 2061} 2062EXPORT_SYMBOL(__grab_cache_page); 2063 2064static ssize_t generic_perform_write_2copy(struct file *file, 2065 struct iov_iter *i, loff_t pos) 2066{ 2067 struct address_space *mapping = file->f_mapping; 2068 const struct address_space_operations *a_ops = mapping->a_ops; 2069 struct inode *inode = mapping->host; 2070 long status = 0; 2071 ssize_t written = 0; 2072 2073 do { 2074 struct page *src_page; 2075 struct page *page; 2076 pgoff_t index; /* Pagecache index for current page */ 2077 unsigned long offset; /* Offset into pagecache page */ 2078 unsigned long bytes; /* Bytes to write to page */ 2079 size_t copied; /* Bytes copied from user */ 2080 2081 offset = (pos & (PAGE_CACHE_SIZE - 1)); 2082 index = pos >> PAGE_CACHE_SHIFT; 2083 bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset, 2084 iov_iter_count(i)); 2085 2086 /* 2087 * a non-NULL src_page indicates that we're doing the 2088 * copy via get_user_pages and kmap. 2089 */ 2090 src_page = NULL; 2091 2092 /* 2093 * Bring in the user page that we will copy from _first_. 2094 * Otherwise there's a nasty deadlock on copying from the 2095 * same page as we're writing to, without it being marked 2096 * up-to-date. 2097 * 2098 * Not only is this an optimisation, but it is also required 2099 * to check that the address is actually valid, when atomic 2100 * usercopies are used, below. 2101 */ 2102 if (unlikely(iov_iter_fault_in_readable(i, bytes))) { 2103 status = -EFAULT; 2104 break; 2105 } 2106 2107 page = __grab_cache_page(mapping, index); 2108 if (!page) { 2109 status = -ENOMEM; 2110 break; 2111 } 2112 2113 /* 2114 * non-uptodate pages cannot cope with short copies, and we 2115 * cannot take a pagefault with the destination page locked. 2116 * So pin the source page to copy it. 2117 */ 2118 if (!PageUptodate(page) && !segment_eq(get_fs(), KERNEL_DS)) { 2119 unlock_page(page); 2120 2121 src_page = alloc_page(GFP_KERNEL); 2122 if (!src_page) { 2123 page_cache_release(page); 2124 status = -ENOMEM; 2125 break; 2126 } 2127 2128 /* 2129 * Cannot get_user_pages with a page locked for the 2130 * same reason as we can't take a page fault with a 2131 * page locked (as explained below). 2132 */ 2133 copied = iov_iter_copy_from_user(src_page, i, 2134 offset, bytes); 2135 if (unlikely(copied == 0)) { 2136 status = -EFAULT; 2137 page_cache_release(page); 2138 page_cache_release(src_page); 2139 break; 2140 } 2141 bytes = copied; 2142 2143 lock_page(page); 2144 /* 2145 * Can't handle the page going uptodate here, because 2146 * that means we would use non-atomic usercopies, which 2147 * zero out the tail of the page, which can cause 2148 * zeroes to become transiently visible. We could just 2149 * use a non-zeroing copy, but the APIs aren't too 2150 * consistent. 2151 */ 2152 if (unlikely(!page->mapping || PageUptodate(page))) { 2153 unlock_page(page); 2154 page_cache_release(page); 2155 page_cache_release(src_page); 2156 continue; 2157 } 2158 } 2159 2160 status = a_ops->prepare_write(file, page, offset, offset+bytes); 2161 if (unlikely(status)) 2162 goto fs_write_aop_error; 2163 2164 if (!src_page) { 2165 /* 2166 * Must not enter the pagefault handler here, because 2167 * we hold the page lock, so we might recursively 2168 * deadlock on the same lock, or get an ABBA deadlock 2169 * against a different lock, or against the mmap_sem 2170 * (which nests outside the page lock). So increment 2171 * preempt count, and use _atomic usercopies. 2172 * 2173 * The page is uptodate so we are OK to encounter a 2174 * short copy: if unmodified parts of the page are 2175 * marked dirty and written out to disk, it doesn't 2176 * really matter. 2177 */ 2178 pagefault_disable(); 2179 copied = iov_iter_copy_from_user_atomic(page, i, 2180 offset, bytes); 2181 pagefault_enable(); 2182 } else { 2183 void *src, *dst; 2184 src = kmap_atomic(src_page, KM_USER0); 2185 dst = kmap_atomic(page, KM_USER1); 2186 memcpy(dst + offset, src + offset, bytes); 2187 kunmap_atomic(dst, KM_USER1); 2188 kunmap_atomic(src, KM_USER0); 2189 copied = bytes; 2190 } 2191 flush_dcache_page(page); 2192 2193 status = a_ops->commit_write(file, page, offset, offset+bytes); 2194 if (unlikely(status < 0)) 2195 goto fs_write_aop_error; 2196 if (unlikely(status > 0)) /* filesystem did partial write */ 2197 copied = min_t(size_t, copied, status); 2198 2199 unlock_page(page); 2200 mark_page_accessed(page); 2201 page_cache_release(page); 2202 if (src_page) 2203 page_cache_release(src_page); 2204 2205 iov_iter_advance(i, copied); 2206 pos += copied; 2207 written += copied; 2208 2209 balance_dirty_pages_ratelimited(mapping); 2210 cond_resched(); 2211 continue; 2212 2213fs_write_aop_error: 2214 unlock_page(page); 2215 page_cache_release(page); 2216 if (src_page) 2217 page_cache_release(src_page); 2218 2219 /* 2220 * prepare_write() may have instantiated a few blocks 2221 * outside i_size. Trim these off again. Don't need 2222 * i_size_read because we hold i_mutex. 2223 */ 2224 if (pos + bytes > inode->i_size) 2225 vmtruncate(inode, inode->i_size); 2226 break; 2227 } while (iov_iter_count(i)); 2228 2229 return written ? written : status; 2230} 2231 2232static ssize_t generic_perform_write(struct file *file, 2233 struct iov_iter *i, loff_t pos) 2234{ 2235 struct address_space *mapping = file->f_mapping; 2236 const struct address_space_operations *a_ops = mapping->a_ops; 2237 long status = 0; 2238 ssize_t written = 0; 2239 unsigned int flags = 0; 2240 2241 /* 2242 * Copies from kernel address space cannot fail (NFSD is a big user). 2243 */ 2244 if (segment_eq(get_fs(), KERNEL_DS)) 2245 flags |= AOP_FLAG_UNINTERRUPTIBLE; 2246 2247 do { 2248 struct page *page; 2249 pgoff_t index; /* Pagecache index for current page */ 2250 unsigned long offset; /* Offset into pagecache page */ 2251 unsigned long bytes; /* Bytes to write to page */ 2252 size_t copied; /* Bytes copied from user */ 2253 void *fsdata; 2254 2255 offset = (pos & (PAGE_CACHE_SIZE - 1)); 2256 index = pos >> PAGE_CACHE_SHIFT; 2257 bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset, 2258 iov_iter_count(i)); 2259 2260again: 2261 2262 /* 2263 * Bring in the user page that we will copy from _first_. 2264 * Otherwise there's a nasty deadlock on copying from the 2265 * same page as we're writing to, without it being marked 2266 * up-to-date. 2267 * 2268 * Not only is this an optimisation, but it is also required 2269 * to check that the address is actually valid, when atomic 2270 * usercopies are used, below. 2271 */ 2272 if (unlikely(iov_iter_fault_in_readable(i, bytes))) { 2273 status = -EFAULT; 2274 break; 2275 } 2276 2277 status = a_ops->write_begin(file, mapping, pos, bytes, flags, 2278 &page, &fsdata); 2279 if (unlikely(status)) 2280 break; 2281 2282 pagefault_disable(); 2283 copied = iov_iter_copy_from_user_atomic(page, i, offset, bytes); 2284 pagefault_enable(); 2285 flush_dcache_page(page); 2286 2287 status = a_ops->write_end(file, mapping, pos, bytes, copied, 2288 page, fsdata); 2289 if (unlikely(status < 0)) 2290 break; 2291 copied = status; 2292 2293 cond_resched(); 2294 2295 iov_iter_advance(i, copied); 2296 if (unlikely(copied == 0)) { 2297 /* 2298 * If we were unable to copy any data at all, we must 2299 * fall back to a single segment length write. 2300 * 2301 * If we didn't fallback here, we could livelock 2302 * because not all segments in the iov can be copied at 2303 * once without a pagefault. 2304 */ 2305 bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset, 2306 iov_iter_single_seg_count(i)); 2307 goto again; 2308 } 2309 pos += copied; 2310 written += copied; 2311 2312 balance_dirty_pages_ratelimited(mapping); 2313 2314 } while (iov_iter_count(i)); 2315 2316 return written ? written : status; 2317} 2318 2319ssize_t 2320generic_file_buffered_write(struct kiocb *iocb, const struct iovec *iov, 2321 unsigned long nr_segs, loff_t pos, loff_t *ppos, 2322 size_t count, ssize_t written) 2323{ 2324 struct file *file = iocb->ki_filp; 2325 struct address_space *mapping = file->f_mapping; 2326 const struct address_space_operations *a_ops = mapping->a_ops; 2327 struct inode *inode = mapping->host; 2328 ssize_t status; 2329 struct iov_iter i; 2330 2331 iov_iter_init(&i, iov, nr_segs, count, written); 2332 if (a_ops->write_begin) 2333 status = generic_perform_write(file, &i, pos); 2334 else 2335 status = generic_perform_write_2copy(file, &i, pos); 2336 2337 if (likely(status >= 0)) { 2338 written += status; 2339 *ppos = pos + status; 2340 2341 /* 2342 * For now, when the user asks for O_SYNC, we'll actually give 2343 * O_DSYNC 2344 */ 2345 if (unlikely((file->f_flags & O_SYNC) || IS_SYNC(inode))) { 2346 if (!a_ops->writepage || !is_sync_kiocb(iocb)) 2347 status = generic_osync_inode(inode, mapping, 2348 OSYNC_METADATA|OSYNC_DATA); 2349 } 2350 } 2351 2352 /* 2353 * If we get here for O_DIRECT writes then we must have fallen through 2354 * to buffered writes (block instantiation inside i_size). So we sync 2355 * the file data here, to try to honour O_DIRECT expectations. 2356 */ 2357 if (unlikely(file->f_flags & O_DIRECT) && written) 2358 status = filemap_write_and_wait(mapping); 2359 2360 return written ? written : status; 2361} 2362EXPORT_SYMBOL(generic_file_buffered_write); 2363 2364static ssize_t 2365__generic_file_aio_write_nolock(struct kiocb *iocb, const struct iovec *iov, 2366 unsigned long nr_segs, loff_t *ppos) 2367{ 2368 struct file *file = iocb->ki_filp; 2369 struct address_space * mapping = file->f_mapping; 2370 size_t ocount; /* original count */ 2371 size_t count; /* after file limit checks */ 2372 struct inode *inode = mapping->host; 2373 loff_t pos; 2374 ssize_t written; 2375 ssize_t err; 2376 2377 ocount = 0; 2378 err = generic_segment_checks(iov, &nr_segs, &ocount, VERIFY_READ); 2379 if (err) 2380 return err; 2381 2382 count = ocount; 2383 pos = *ppos; 2384 2385 vfs_check_frozen(inode->i_sb, SB_FREEZE_WRITE); 2386 2387 /* We can write back this queue in page reclaim */ 2388 current->backing_dev_info = mapping->backing_dev_info; 2389 written = 0; 2390 2391 err = generic_write_checks(file, &pos, &count, S_ISBLK(inode->i_mode)); 2392 if (err) 2393 goto out; 2394 2395 if (count == 0) 2396 goto out; 2397 2398 err = remove_suid(file->f_path.dentry); 2399 if (err) 2400 goto out; 2401 2402 file_update_time(file); 2403 2404 /* coalesce the iovecs and go direct-to-BIO for O_DIRECT */ 2405 if (unlikely(file->f_flags & O_DIRECT)) { 2406 loff_t endbyte; 2407 ssize_t written_buffered; 2408 2409 written = generic_file_direct_write(iocb, iov, &nr_segs, pos, 2410 ppos, count, ocount); 2411 if (written < 0 || written == count) 2412 goto out; 2413 /* 2414 * direct-io write to a hole: fall through to buffered I/O 2415 * for completing the rest of the request. 2416 */ 2417 pos += written; 2418 count -= written; 2419 written_buffered = generic_file_buffered_write(iocb, iov, 2420 nr_segs, pos, ppos, count, 2421 written); 2422 /* 2423 * If generic_file_buffered_write() retuned a synchronous error 2424 * then we want to return the number of bytes which were 2425 * direct-written, or the error code if that was zero. Note 2426 * that this differs from normal direct-io semantics, which 2427 * will return -EFOO even if some bytes were written. 2428 */ 2429 if (written_buffered < 0) { 2430 err = written_buffered; 2431 goto out; 2432 } 2433 2434 /* 2435 * We need to ensure that the page cache pages are written to 2436 * disk and invalidated to preserve the expected O_DIRECT 2437 * semantics. 2438 */ 2439 endbyte = pos + written_buffered - written - 1; 2440 err = do_sync_mapping_range(file->f_mapping, pos, endbyte, 2441 SYNC_FILE_RANGE_WAIT_BEFORE| 2442 SYNC_FILE_RANGE_WRITE| 2443 SYNC_FILE_RANGE_WAIT_AFTER); 2444 if (err == 0) { 2445 written = written_buffered; 2446 invalidate_mapping_pages(mapping, 2447 pos >> PAGE_CACHE_SHIFT, 2448 endbyte >> PAGE_CACHE_SHIFT); 2449 } else { 2450 /* 2451 * We don't know how much we wrote, so just return 2452 * the number of bytes which were direct-written 2453 */ 2454 } 2455 } else { 2456 written = generic_file_buffered_write(iocb, iov, nr_segs, 2457 pos, ppos, count, written); 2458 } 2459out: 2460 current->backing_dev_info = NULL; 2461 return written ? written : err; 2462} 2463 2464ssize_t generic_file_aio_write_nolock(struct kiocb *iocb, 2465 const struct iovec *iov, unsigned long nr_segs, loff_t pos) 2466{ 2467 struct file *file = iocb->ki_filp; 2468 struct address_space *mapping = file->f_mapping; 2469 struct inode *inode = mapping->host; 2470 ssize_t ret; 2471 2472 BUG_ON(iocb->ki_pos != pos); 2473 2474 ret = __generic_file_aio_write_nolock(iocb, iov, nr_segs, 2475 &iocb->ki_pos); 2476 2477 if (ret > 0 && ((file->f_flags & O_SYNC) || IS_SYNC(inode))) { 2478 ssize_t err; 2479 2480 err = sync_page_range_nolock(inode, mapping, pos, ret); 2481 if (err < 0) 2482 ret = err; 2483 } 2484 return ret; 2485} 2486EXPORT_SYMBOL(generic_file_aio_write_nolock); 2487 2488ssize_t generic_file_aio_write(struct kiocb *iocb, const struct iovec *iov, 2489 unsigned long nr_segs, loff_t pos) 2490{ 2491 struct file *file = iocb->ki_filp; 2492 struct address_space *mapping = file->f_mapping; 2493 struct inode *inode = mapping->host; 2494 ssize_t ret; 2495 2496 BUG_ON(iocb->ki_pos != pos); 2497 2498 mutex_lock(&inode->i_mutex); 2499 ret = __generic_file_aio_write_nolock(iocb, iov, nr_segs, 2500 &iocb->ki_pos); 2501 mutex_unlock(&inode->i_mutex); 2502 2503 if (ret > 0 && ((file->f_flags & O_SYNC) || IS_SYNC(inode))) { 2504 ssize_t err; 2505 2506 err = sync_page_range(inode, mapping, pos, ret); 2507 if (err < 0) 2508 ret = err; 2509 } 2510 return ret; 2511} 2512EXPORT_SYMBOL(generic_file_aio_write); 2513 2514/* 2515 * Called under i_mutex for writes to S_ISREG files. Returns -EIO if something 2516 * went wrong during pagecache shootdown. 2517 */ 2518static ssize_t 2519generic_file_direct_IO(int rw, struct kiocb *iocb, const struct iovec *iov, 2520 loff_t offset, unsigned long nr_segs) 2521{ 2522 struct file *file = iocb->ki_filp; 2523 struct address_space *mapping = file->f_mapping; 2524 ssize_t retval; 2525 size_t write_len; 2526 pgoff_t end = 0; /* silence gcc */ 2527 2528 /* 2529 * If it's a write, unmap all mmappings of the file up-front. This 2530 * will cause any pte dirty bits to be propagated into the pageframes 2531 * for the subsequent filemap_write_and_wait(). 2532 */ 2533 if (rw == WRITE) { 2534 write_len = iov_length(iov, nr_segs); 2535 end = (offset + write_len - 1) >> PAGE_CACHE_SHIFT; 2536 if (mapping_mapped(mapping)) 2537 unmap_mapping_range(mapping, offset, write_len, 0); 2538 } 2539 2540 retval = filemap_write_and_wait(mapping); 2541 if (retval) 2542 goto out; 2543 2544 /* 2545 * After a write we want buffered reads to be sure to go to disk to get 2546 * the new data. We invalidate clean cached page from the region we're 2547 * about to write. We do this *before* the write so that we can return 2548 * -EIO without clobbering -EIOCBQUEUED from ->direct_IO(). 2549 */ 2550 if (rw == WRITE && mapping->nrpages) { 2551 retval = invalidate_inode_pages2_range(mapping, 2552 offset >> PAGE_CACHE_SHIFT, end); 2553 if (retval) 2554 goto out; 2555 } 2556 2557 retval = mapping->a_ops->direct_IO(rw, iocb, iov, offset, nr_segs); 2558 2559 /* 2560 * Finally, try again to invalidate clean pages which might have been 2561 * cached by non-direct readahead, or faulted in by get_user_pages() 2562 * if the source of the write was an mmap'ed region of the file 2563 * we're writing. Either one is a pretty crazy thing to do, 2564 * so we don't support it 100%. If this invalidation 2565 * fails, tough, the write still worked... 2566 */ 2567 if (rw == WRITE && mapping->nrpages) { 2568 invalidate_inode_pages2_range(mapping, offset >> PAGE_CACHE_SHIFT, end); 2569 } 2570out: 2571 return retval; 2572} 2573 2574/** 2575 * try_to_release_page() - release old fs-specific metadata on a page 2576 * 2577 * @page: the page which the kernel is trying to free 2578 * @gfp_mask: memory allocation flags (and I/O mode) 2579 * 2580 * The address_space is to try to release any data against the page 2581 * (presumably at page->private). If the release was successful, return `1'. 2582 * Otherwise return zero. 2583 * 2584 * The @gfp_mask argument specifies whether I/O may be performed to release 2585 * this page (__GFP_IO), and whether the call may block (__GFP_WAIT). 2586 * 2587 * NOTE: @gfp_mask may go away, and this function may become non-blocking. 2588 */ 2589int try_to_release_page(struct page *page, gfp_t gfp_mask) 2590{ 2591 struct address_space * const mapping = page->mapping; 2592 2593 BUG_ON(!PageLocked(page)); 2594 if (PageWriteback(page)) 2595 return 0; 2596 2597 if (mapping && mapping->a_ops->releasepage) 2598 return mapping->a_ops->releasepage(page, gfp_mask); 2599 return try_to_free_buffers(page); 2600} 2601 2602EXPORT_SYMBOL(try_to_release_page); 2603