filemap.c revision 920c7a5d0c94b8ce740f1d76fa06422f2a95a757
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/backing-dev.h> 32#include <linux/security.h> 33#include <linux/syscalls.h> 34#include <linux/cpuset.h> 35#include <linux/hardirq.h> /* for BUG_ON(!in_atomic()) only */ 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 radix_tree_delete(&mapping->page_tree, page->index); 122 page->mapping = NULL; 123 mapping->nrpages--; 124 __dec_zone_page_state(page, NR_FILE_PAGES); 125 BUG_ON(page_mapped(page)); 126 127 /* 128 * Some filesystems seem to re-dirty the page even after 129 * the VM has canceled the dirty bit (eg ext3 journaling). 130 * 131 * Fix it up by doing a final dirty accounting check after 132 * having removed the page entirely. 133 */ 134 if (PageDirty(page) && mapping_cap_account_dirty(mapping)) { 135 dec_zone_page_state(page, NR_FILE_DIRTY); 136 dec_bdi_stat(mapping->backing_dev_info, BDI_RECLAIMABLE); 137 } 138} 139 140void remove_from_page_cache(struct page *page) 141{ 142 struct address_space *mapping = page->mapping; 143 144 BUG_ON(!PageLocked(page)); 145 146 write_lock_irq(&mapping->tree_lock); 147 __remove_from_page_cache(page); 148 write_unlock_irq(&mapping->tree_lock); 149} 150 151static int sync_page(void *word) 152{ 153 struct address_space *mapping; 154 struct page *page; 155 156 page = container_of((unsigned long *)word, struct page, flags); 157 158 /* 159 * page_mapping() is being called without PG_locked held. 160 * Some knowledge of the state and use of the page is used to 161 * reduce the requirements down to a memory barrier. 162 * The danger here is of a stale page_mapping() return value 163 * indicating a struct address_space different from the one it's 164 * associated with when it is associated with one. 165 * After smp_mb(), it's either the correct page_mapping() for 166 * the page, or an old page_mapping() and the page's own 167 * page_mapping() has gone NULL. 168 * The ->sync_page() address_space operation must tolerate 169 * page_mapping() going NULL. By an amazing coincidence, 170 * this comes about because none of the users of the page 171 * in the ->sync_page() methods make essential use of the 172 * page_mapping(), merely passing the page down to the backing 173 * device's unplug functions when it's non-NULL, which in turn 174 * ignore it for all cases but swap, where only page_private(page) is 175 * of interest. When page_mapping() does go NULL, the entire 176 * call stack gracefully ignores the page and returns. 177 * -- wli 178 */ 179 smp_mb(); 180 mapping = page_mapping(page); 181 if (mapping && mapping->a_ops && mapping->a_ops->sync_page) 182 mapping->a_ops->sync_page(page); 183 io_schedule(); 184 return 0; 185} 186 187static int sync_page_killable(void *word) 188{ 189 sync_page(word); 190 return fatal_signal_pending(current) ? -EINTR : 0; 191} 192 193/** 194 * __filemap_fdatawrite_range - start writeback on mapping dirty pages in range 195 * @mapping: address space structure to write 196 * @start: offset in bytes where the range starts 197 * @end: offset in bytes where the range ends (inclusive) 198 * @sync_mode: enable synchronous operation 199 * 200 * Start writeback against all of a mapping's dirty pages that lie 201 * within the byte offsets <start, end> inclusive. 202 * 203 * If sync_mode is WB_SYNC_ALL then this is a "data integrity" operation, as 204 * opposed to a regular memory cleansing writeback. The difference between 205 * these two operations is that if a dirty page/buffer is encountered, it must 206 * be waited upon, and not just skipped over. 207 */ 208int __filemap_fdatawrite_range(struct address_space *mapping, loff_t start, 209 loff_t end, int sync_mode) 210{ 211 int ret; 212 struct writeback_control wbc = { 213 .sync_mode = sync_mode, 214 .nr_to_write = mapping->nrpages * 2, 215 .range_start = start, 216 .range_end = end, 217 }; 218 219 if (!mapping_cap_writeback_dirty(mapping)) 220 return 0; 221 222 ret = do_writepages(mapping, &wbc); 223 return ret; 224} 225 226static inline int __filemap_fdatawrite(struct address_space *mapping, 227 int sync_mode) 228{ 229 return __filemap_fdatawrite_range(mapping, 0, LLONG_MAX, sync_mode); 230} 231 232int filemap_fdatawrite(struct address_space *mapping) 233{ 234 return __filemap_fdatawrite(mapping, WB_SYNC_ALL); 235} 236EXPORT_SYMBOL(filemap_fdatawrite); 237 238static int filemap_fdatawrite_range(struct address_space *mapping, loff_t start, 239 loff_t end) 240{ 241 return __filemap_fdatawrite_range(mapping, start, end, WB_SYNC_ALL); 242} 243 244/** 245 * filemap_flush - mostly a non-blocking flush 246 * @mapping: target address_space 247 * 248 * This is a mostly non-blocking flush. Not suitable for data-integrity 249 * purposes - I/O may not be started against all dirty pages. 250 */ 251int filemap_flush(struct address_space *mapping) 252{ 253 return __filemap_fdatawrite(mapping, WB_SYNC_NONE); 254} 255EXPORT_SYMBOL(filemap_flush); 256 257/** 258 * wait_on_page_writeback_range - wait for writeback to complete 259 * @mapping: target address_space 260 * @start: beginning page index 261 * @end: ending page index 262 * 263 * Wait for writeback to complete against pages indexed by start->end 264 * inclusive 265 */ 266int wait_on_page_writeback_range(struct address_space *mapping, 267 pgoff_t start, pgoff_t end) 268{ 269 struct pagevec pvec; 270 int nr_pages; 271 int ret = 0; 272 pgoff_t index; 273 274 if (end < start) 275 return 0; 276 277 pagevec_init(&pvec, 0); 278 index = start; 279 while ((index <= end) && 280 (nr_pages = pagevec_lookup_tag(&pvec, mapping, &index, 281 PAGECACHE_TAG_WRITEBACK, 282 min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1)) != 0) { 283 unsigned i; 284 285 for (i = 0; i < nr_pages; i++) { 286 struct page *page = pvec.pages[i]; 287 288 /* until radix tree lookup accepts end_index */ 289 if (page->index > end) 290 continue; 291 292 wait_on_page_writeback(page); 293 if (PageError(page)) 294 ret = -EIO; 295 } 296 pagevec_release(&pvec); 297 cond_resched(); 298 } 299 300 /* Check for outstanding write errors */ 301 if (test_and_clear_bit(AS_ENOSPC, &mapping->flags)) 302 ret = -ENOSPC; 303 if (test_and_clear_bit(AS_EIO, &mapping->flags)) 304 ret = -EIO; 305 306 return ret; 307} 308 309/** 310 * sync_page_range - write and wait on all pages in the passed range 311 * @inode: target inode 312 * @mapping: target address_space 313 * @pos: beginning offset in pages to write 314 * @count: number of bytes to write 315 * 316 * Write and wait upon all the pages in the passed range. This is a "data 317 * integrity" operation. It waits upon in-flight writeout before starting and 318 * waiting upon new writeout. If there was an IO error, return it. 319 * 320 * We need to re-take i_mutex during the generic_osync_inode list walk because 321 * it is otherwise livelockable. 322 */ 323int sync_page_range(struct inode *inode, struct address_space *mapping, 324 loff_t pos, loff_t count) 325{ 326 pgoff_t start = pos >> PAGE_CACHE_SHIFT; 327 pgoff_t end = (pos + count - 1) >> PAGE_CACHE_SHIFT; 328 int ret; 329 330 if (!mapping_cap_writeback_dirty(mapping) || !count) 331 return 0; 332 ret = filemap_fdatawrite_range(mapping, pos, pos + count - 1); 333 if (ret == 0) { 334 mutex_lock(&inode->i_mutex); 335 ret = generic_osync_inode(inode, mapping, OSYNC_METADATA); 336 mutex_unlock(&inode->i_mutex); 337 } 338 if (ret == 0) 339 ret = wait_on_page_writeback_range(mapping, start, end); 340 return ret; 341} 342EXPORT_SYMBOL(sync_page_range); 343 344/** 345 * sync_page_range_nolock 346 * @inode: target inode 347 * @mapping: target address_space 348 * @pos: beginning offset in pages to write 349 * @count: number of bytes to write 350 * 351 * Note: Holding i_mutex across sync_page_range_nolock() is not a good idea 352 * as it forces O_SYNC writers to different parts of the same file 353 * to be serialised right until io completion. 354 */ 355int sync_page_range_nolock(struct inode *inode, struct address_space *mapping, 356 loff_t pos, loff_t count) 357{ 358 pgoff_t start = pos >> PAGE_CACHE_SHIFT; 359 pgoff_t end = (pos + count - 1) >> PAGE_CACHE_SHIFT; 360 int ret; 361 362 if (!mapping_cap_writeback_dirty(mapping) || !count) 363 return 0; 364 ret = filemap_fdatawrite_range(mapping, pos, pos + count - 1); 365 if (ret == 0) 366 ret = generic_osync_inode(inode, mapping, OSYNC_METADATA); 367 if (ret == 0) 368 ret = wait_on_page_writeback_range(mapping, start, end); 369 return ret; 370} 371EXPORT_SYMBOL(sync_page_range_nolock); 372 373/** 374 * filemap_fdatawait - wait for all under-writeback pages to complete 375 * @mapping: address space structure to wait for 376 * 377 * Walk the list of under-writeback pages of the given address space 378 * and wait for all of them. 379 */ 380int filemap_fdatawait(struct address_space *mapping) 381{ 382 loff_t i_size = i_size_read(mapping->host); 383 384 if (i_size == 0) 385 return 0; 386 387 return wait_on_page_writeback_range(mapping, 0, 388 (i_size - 1) >> PAGE_CACHE_SHIFT); 389} 390EXPORT_SYMBOL(filemap_fdatawait); 391 392int filemap_write_and_wait(struct address_space *mapping) 393{ 394 int err = 0; 395 396 if (mapping->nrpages) { 397 err = filemap_fdatawrite(mapping); 398 /* 399 * Even if the above returned error, the pages may be 400 * written partially (e.g. -ENOSPC), so we wait for it. 401 * But the -EIO is special case, it may indicate the worst 402 * thing (e.g. bug) happened, so we avoid waiting for it. 403 */ 404 if (err != -EIO) { 405 int err2 = filemap_fdatawait(mapping); 406 if (!err) 407 err = err2; 408 } 409 } 410 return err; 411} 412EXPORT_SYMBOL(filemap_write_and_wait); 413 414/** 415 * filemap_write_and_wait_range - write out & wait on a file range 416 * @mapping: the address_space for the pages 417 * @lstart: offset in bytes where the range starts 418 * @lend: offset in bytes where the range ends (inclusive) 419 * 420 * Write out and wait upon file offsets lstart->lend, inclusive. 421 * 422 * Note that `lend' is inclusive (describes the last byte to be written) so 423 * that this function can be used to write to the very end-of-file (end = -1). 424 */ 425int filemap_write_and_wait_range(struct address_space *mapping, 426 loff_t lstart, loff_t lend) 427{ 428 int err = 0; 429 430 if (mapping->nrpages) { 431 err = __filemap_fdatawrite_range(mapping, lstart, lend, 432 WB_SYNC_ALL); 433 /* See comment of filemap_write_and_wait() */ 434 if (err != -EIO) { 435 int err2 = wait_on_page_writeback_range(mapping, 436 lstart >> PAGE_CACHE_SHIFT, 437 lend >> PAGE_CACHE_SHIFT); 438 if (!err) 439 err = err2; 440 } 441 } 442 return err; 443} 444 445/** 446 * add_to_page_cache - add newly allocated pagecache pages 447 * @page: page to add 448 * @mapping: the page's address_space 449 * @offset: page index 450 * @gfp_mask: page allocation mode 451 * 452 * This function is used to add newly allocated pagecache pages; 453 * the page is new, so we can just run SetPageLocked() against it. 454 * The other page state flags were set by rmqueue(). 455 * 456 * This function does not add the page to the LRU. The caller must do that. 457 */ 458int add_to_page_cache(struct page *page, struct address_space *mapping, 459 pgoff_t offset, gfp_t gfp_mask) 460{ 461 int error = radix_tree_preload(gfp_mask & ~__GFP_HIGHMEM); 462 463 if (error == 0) { 464 write_lock_irq(&mapping->tree_lock); 465 error = radix_tree_insert(&mapping->page_tree, offset, page); 466 if (!error) { 467 page_cache_get(page); 468 SetPageLocked(page); 469 page->mapping = mapping; 470 page->index = offset; 471 mapping->nrpages++; 472 __inc_zone_page_state(page, NR_FILE_PAGES); 473 } 474 write_unlock_irq(&mapping->tree_lock); 475 radix_tree_preload_end(); 476 } 477 return error; 478} 479EXPORT_SYMBOL(add_to_page_cache); 480 481int add_to_page_cache_lru(struct page *page, struct address_space *mapping, 482 pgoff_t offset, gfp_t gfp_mask) 483{ 484 int ret = add_to_page_cache(page, mapping, offset, gfp_mask); 485 if (ret == 0) 486 lru_cache_add(page); 487 return ret; 488} 489 490#ifdef CONFIG_NUMA 491struct page *__page_cache_alloc(gfp_t gfp) 492{ 493 if (cpuset_do_page_mem_spread()) { 494 int n = cpuset_mem_spread_node(); 495 return alloc_pages_node(n, gfp, 0); 496 } 497 return alloc_pages(gfp, 0); 498} 499EXPORT_SYMBOL(__page_cache_alloc); 500#endif 501 502static int __sleep_on_page_lock(void *word) 503{ 504 io_schedule(); 505 return 0; 506} 507 508/* 509 * In order to wait for pages to become available there must be 510 * waitqueues associated with pages. By using a hash table of 511 * waitqueues where the bucket discipline is to maintain all 512 * waiters on the same queue and wake all when any of the pages 513 * become available, and for the woken contexts to check to be 514 * sure the appropriate page became available, this saves space 515 * at a cost of "thundering herd" phenomena during rare hash 516 * collisions. 517 */ 518static wait_queue_head_t *page_waitqueue(struct page *page) 519{ 520 const struct zone *zone = page_zone(page); 521 522 return &zone->wait_table[hash_ptr(page, zone->wait_table_bits)]; 523} 524 525static inline void wake_up_page(struct page *page, int bit) 526{ 527 __wake_up_bit(page_waitqueue(page), &page->flags, bit); 528} 529 530void wait_on_page_bit(struct page *page, int bit_nr) 531{ 532 DEFINE_WAIT_BIT(wait, &page->flags, bit_nr); 533 534 if (test_bit(bit_nr, &page->flags)) 535 __wait_on_bit(page_waitqueue(page), &wait, sync_page, 536 TASK_UNINTERRUPTIBLE); 537} 538EXPORT_SYMBOL(wait_on_page_bit); 539 540/** 541 * unlock_page - unlock a locked page 542 * @page: the page 543 * 544 * Unlocks the page and wakes up sleepers in ___wait_on_page_locked(). 545 * Also wakes sleepers in wait_on_page_writeback() because the wakeup 546 * mechananism between PageLocked pages and PageWriteback pages is shared. 547 * But that's OK - sleepers in wait_on_page_writeback() just go back to sleep. 548 * 549 * The first mb is necessary to safely close the critical section opened by the 550 * TestSetPageLocked(), the second mb is necessary to enforce ordering between 551 * the clear_bit and the read of the waitqueue (to avoid SMP races with a 552 * parallel wait_on_page_locked()). 553 */ 554void unlock_page(struct page *page) 555{ 556 smp_mb__before_clear_bit(); 557 if (!TestClearPageLocked(page)) 558 BUG(); 559 smp_mb__after_clear_bit(); 560 wake_up_page(page, PG_locked); 561} 562EXPORT_SYMBOL(unlock_page); 563 564/** 565 * end_page_writeback - end writeback against a page 566 * @page: the page 567 */ 568void end_page_writeback(struct page *page) 569{ 570 if (!TestClearPageReclaim(page) || rotate_reclaimable_page(page)) { 571 if (!test_clear_page_writeback(page)) 572 BUG(); 573 } 574 smp_mb__after_clear_bit(); 575 wake_up_page(page, PG_writeback); 576} 577EXPORT_SYMBOL(end_page_writeback); 578 579/** 580 * __lock_page - get a lock on the page, assuming we need to sleep to get it 581 * @page: the page to lock 582 * 583 * Ugly. Running sync_page() in state TASK_UNINTERRUPTIBLE is scary. If some 584 * random driver's requestfn sets TASK_RUNNING, we could busywait. However 585 * chances are that on the second loop, the block layer's plug list is empty, 586 * so sync_page() will then return in state TASK_UNINTERRUPTIBLE. 587 */ 588void __lock_page(struct page *page) 589{ 590 DEFINE_WAIT_BIT(wait, &page->flags, PG_locked); 591 592 __wait_on_bit_lock(page_waitqueue(page), &wait, sync_page, 593 TASK_UNINTERRUPTIBLE); 594} 595EXPORT_SYMBOL(__lock_page); 596 597int fastcall __lock_page_killable(struct page *page) 598{ 599 DEFINE_WAIT_BIT(wait, &page->flags, PG_locked); 600 601 return __wait_on_bit_lock(page_waitqueue(page), &wait, 602 sync_page_killable, TASK_KILLABLE); 603} 604 605/* 606 * Variant of lock_page that does not require the caller to hold a reference 607 * on the page's mapping. 608 */ 609void __lock_page_nosync(struct page *page) 610{ 611 DEFINE_WAIT_BIT(wait, &page->flags, PG_locked); 612 __wait_on_bit_lock(page_waitqueue(page), &wait, __sleep_on_page_lock, 613 TASK_UNINTERRUPTIBLE); 614} 615 616/** 617 * find_get_page - find and get a page reference 618 * @mapping: the address_space to search 619 * @offset: the page index 620 * 621 * Is there a pagecache struct page at the given (mapping, offset) tuple? 622 * If yes, increment its refcount and return it; if no, return NULL. 623 */ 624struct page * find_get_page(struct address_space *mapping, pgoff_t offset) 625{ 626 struct page *page; 627 628 read_lock_irq(&mapping->tree_lock); 629 page = radix_tree_lookup(&mapping->page_tree, offset); 630 if (page) 631 page_cache_get(page); 632 read_unlock_irq(&mapping->tree_lock); 633 return page; 634} 635EXPORT_SYMBOL(find_get_page); 636 637/** 638 * find_lock_page - locate, pin and lock a pagecache page 639 * @mapping: the address_space to search 640 * @offset: the page index 641 * 642 * Locates the desired pagecache page, locks it, increments its reference 643 * count and returns its address. 644 * 645 * Returns zero if the page was not present. find_lock_page() may sleep. 646 */ 647struct page *find_lock_page(struct address_space *mapping, 648 pgoff_t offset) 649{ 650 struct page *page; 651 652repeat: 653 read_lock_irq(&mapping->tree_lock); 654 page = radix_tree_lookup(&mapping->page_tree, offset); 655 if (page) { 656 page_cache_get(page); 657 if (TestSetPageLocked(page)) { 658 read_unlock_irq(&mapping->tree_lock); 659 __lock_page(page); 660 661 /* Has the page been truncated while we slept? */ 662 if (unlikely(page->mapping != mapping)) { 663 unlock_page(page); 664 page_cache_release(page); 665 goto repeat; 666 } 667 VM_BUG_ON(page->index != offset); 668 goto out; 669 } 670 } 671 read_unlock_irq(&mapping->tree_lock); 672out: 673 return page; 674} 675EXPORT_SYMBOL(find_lock_page); 676 677/** 678 * find_or_create_page - locate or add a pagecache page 679 * @mapping: the page's address_space 680 * @index: the page's index into the mapping 681 * @gfp_mask: page allocation mode 682 * 683 * Locates a page in the pagecache. If the page is not present, a new page 684 * is allocated using @gfp_mask and is added to the pagecache and to the VM's 685 * LRU list. The returned page is locked and has its reference count 686 * incremented. 687 * 688 * find_or_create_page() may sleep, even if @gfp_flags specifies an atomic 689 * allocation! 690 * 691 * find_or_create_page() returns the desired page's address, or zero on 692 * memory exhaustion. 693 */ 694struct page *find_or_create_page(struct address_space *mapping, 695 pgoff_t index, gfp_t gfp_mask) 696{ 697 struct page *page; 698 int err; 699repeat: 700 page = find_lock_page(mapping, index); 701 if (!page) { 702 page = __page_cache_alloc(gfp_mask); 703 if (!page) 704 return NULL; 705 err = add_to_page_cache_lru(page, mapping, index, gfp_mask); 706 if (unlikely(err)) { 707 page_cache_release(page); 708 page = NULL; 709 if (err == -EEXIST) 710 goto repeat; 711 } 712 } 713 return page; 714} 715EXPORT_SYMBOL(find_or_create_page); 716 717/** 718 * find_get_pages - gang pagecache lookup 719 * @mapping: The address_space to search 720 * @start: The starting page index 721 * @nr_pages: The maximum number of pages 722 * @pages: Where the resulting pages are placed 723 * 724 * find_get_pages() will search for and return a group of up to 725 * @nr_pages pages in the mapping. The pages are placed at @pages. 726 * find_get_pages() takes a reference against the returned pages. 727 * 728 * The search returns a group of mapping-contiguous pages with ascending 729 * indexes. There may be holes in the indices due to not-present pages. 730 * 731 * find_get_pages() returns the number of pages which were found. 732 */ 733unsigned find_get_pages(struct address_space *mapping, pgoff_t start, 734 unsigned int nr_pages, struct page **pages) 735{ 736 unsigned int i; 737 unsigned int ret; 738 739 read_lock_irq(&mapping->tree_lock); 740 ret = radix_tree_gang_lookup(&mapping->page_tree, 741 (void **)pages, start, nr_pages); 742 for (i = 0; i < ret; i++) 743 page_cache_get(pages[i]); 744 read_unlock_irq(&mapping->tree_lock); 745 return ret; 746} 747 748/** 749 * find_get_pages_contig - gang contiguous pagecache lookup 750 * @mapping: The address_space to search 751 * @index: The starting page index 752 * @nr_pages: The maximum number of pages 753 * @pages: Where the resulting pages are placed 754 * 755 * find_get_pages_contig() works exactly like find_get_pages(), except 756 * that the returned number of pages are guaranteed to be contiguous. 757 * 758 * find_get_pages_contig() returns the number of pages which were found. 759 */ 760unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t index, 761 unsigned int nr_pages, struct page **pages) 762{ 763 unsigned int i; 764 unsigned int ret; 765 766 read_lock_irq(&mapping->tree_lock); 767 ret = radix_tree_gang_lookup(&mapping->page_tree, 768 (void **)pages, index, nr_pages); 769 for (i = 0; i < ret; i++) { 770 if (pages[i]->mapping == NULL || pages[i]->index != index) 771 break; 772 773 page_cache_get(pages[i]); 774 index++; 775 } 776 read_unlock_irq(&mapping->tree_lock); 777 return i; 778} 779EXPORT_SYMBOL(find_get_pages_contig); 780 781/** 782 * find_get_pages_tag - find and return pages that match @tag 783 * @mapping: the address_space to search 784 * @index: the starting page index 785 * @tag: the tag index 786 * @nr_pages: the maximum number of pages 787 * @pages: where the resulting pages are placed 788 * 789 * Like find_get_pages, except we only return pages which are tagged with 790 * @tag. We update @index to index the next page for the traversal. 791 */ 792unsigned find_get_pages_tag(struct address_space *mapping, pgoff_t *index, 793 int tag, unsigned int nr_pages, struct page **pages) 794{ 795 unsigned int i; 796 unsigned int ret; 797 798 read_lock_irq(&mapping->tree_lock); 799 ret = radix_tree_gang_lookup_tag(&mapping->page_tree, 800 (void **)pages, *index, nr_pages, tag); 801 for (i = 0; i < ret; i++) 802 page_cache_get(pages[i]); 803 if (ret) 804 *index = pages[ret - 1]->index + 1; 805 read_unlock_irq(&mapping->tree_lock); 806 return ret; 807} 808EXPORT_SYMBOL(find_get_pages_tag); 809 810/** 811 * grab_cache_page_nowait - returns locked page at given index in given cache 812 * @mapping: target address_space 813 * @index: the page index 814 * 815 * Same as grab_cache_page(), but do not wait if the page is unavailable. 816 * This is intended for speculative data generators, where the data can 817 * be regenerated if the page couldn't be grabbed. This routine should 818 * be safe to call while holding the lock for another page. 819 * 820 * Clear __GFP_FS when allocating the page to avoid recursion into the fs 821 * and deadlock against the caller's locked page. 822 */ 823struct page * 824grab_cache_page_nowait(struct address_space *mapping, pgoff_t index) 825{ 826 struct page *page = find_get_page(mapping, index); 827 828 if (page) { 829 if (!TestSetPageLocked(page)) 830 return page; 831 page_cache_release(page); 832 return NULL; 833 } 834 page = __page_cache_alloc(mapping_gfp_mask(mapping) & ~__GFP_FS); 835 if (page && add_to_page_cache_lru(page, mapping, index, GFP_KERNEL)) { 836 page_cache_release(page); 837 page = NULL; 838 } 839 return page; 840} 841EXPORT_SYMBOL(grab_cache_page_nowait); 842 843/* 844 * CD/DVDs are error prone. When a medium error occurs, the driver may fail 845 * a _large_ part of the i/o request. Imagine the worst scenario: 846 * 847 * ---R__________________________________________B__________ 848 * ^ reading here ^ bad block(assume 4k) 849 * 850 * read(R) => miss => readahead(R...B) => media error => frustrating retries 851 * => failing the whole request => read(R) => read(R+1) => 852 * readahead(R+1...B+1) => bang => read(R+2) => read(R+3) => 853 * readahead(R+3...B+2) => bang => read(R+3) => read(R+4) => 854 * readahead(R+4...B+3) => bang => read(R+4) => read(R+5) => ...... 855 * 856 * It is going insane. Fix it by quickly scaling down the readahead size. 857 */ 858static void shrink_readahead_size_eio(struct file *filp, 859 struct file_ra_state *ra) 860{ 861 if (!ra->ra_pages) 862 return; 863 864 ra->ra_pages /= 4; 865} 866 867/** 868 * do_generic_mapping_read - generic file read routine 869 * @mapping: address_space to be read 870 * @ra: file's readahead state 871 * @filp: the file to read 872 * @ppos: current file position 873 * @desc: read_descriptor 874 * @actor: read method 875 * 876 * This is a generic file read routine, and uses the 877 * mapping->a_ops->readpage() function for the actual low-level stuff. 878 * 879 * This is really ugly. But the goto's actually try to clarify some 880 * of the logic when it comes to error handling etc. 881 * 882 * Note the struct file* is only passed for the use of readpage. 883 * It may be NULL. 884 */ 885void do_generic_mapping_read(struct address_space *mapping, 886 struct file_ra_state *ra, 887 struct file *filp, 888 loff_t *ppos, 889 read_descriptor_t *desc, 890 read_actor_t actor) 891{ 892 struct inode *inode = mapping->host; 893 pgoff_t index; 894 pgoff_t last_index; 895 pgoff_t prev_index; 896 unsigned long offset; /* offset into pagecache page */ 897 unsigned int prev_offset; 898 int error; 899 900 index = *ppos >> PAGE_CACHE_SHIFT; 901 prev_index = ra->prev_pos >> PAGE_CACHE_SHIFT; 902 prev_offset = ra->prev_pos & (PAGE_CACHE_SIZE-1); 903 last_index = (*ppos + desc->count + PAGE_CACHE_SIZE-1) >> PAGE_CACHE_SHIFT; 904 offset = *ppos & ~PAGE_CACHE_MASK; 905 906 for (;;) { 907 struct page *page; 908 pgoff_t end_index; 909 loff_t isize; 910 unsigned long nr, ret; 911 912 cond_resched(); 913find_page: 914 page = find_get_page(mapping, index); 915 if (!page) { 916 page_cache_sync_readahead(mapping, 917 ra, filp, 918 index, last_index - index); 919 page = find_get_page(mapping, index); 920 if (unlikely(page == NULL)) 921 goto no_cached_page; 922 } 923 if (PageReadahead(page)) { 924 page_cache_async_readahead(mapping, 925 ra, filp, page, 926 index, last_index - index); 927 } 928 if (!PageUptodate(page)) 929 goto page_not_up_to_date; 930page_ok: 931 /* 932 * i_size must be checked after we know the page is Uptodate. 933 * 934 * Checking i_size after the check allows us to calculate 935 * the correct value for "nr", which means the zero-filled 936 * part of the page is not copied back to userspace (unless 937 * another truncate extends the file - this is desired though). 938 */ 939 940 isize = i_size_read(inode); 941 end_index = (isize - 1) >> PAGE_CACHE_SHIFT; 942 if (unlikely(!isize || index > end_index)) { 943 page_cache_release(page); 944 goto out; 945 } 946 947 /* nr is the maximum number of bytes to copy from this page */ 948 nr = PAGE_CACHE_SIZE; 949 if (index == end_index) { 950 nr = ((isize - 1) & ~PAGE_CACHE_MASK) + 1; 951 if (nr <= offset) { 952 page_cache_release(page); 953 goto out; 954 } 955 } 956 nr = nr - offset; 957 958 /* If users can be writing to this page using arbitrary 959 * virtual addresses, take care about potential aliasing 960 * before reading the page on the kernel side. 961 */ 962 if (mapping_writably_mapped(mapping)) 963 flush_dcache_page(page); 964 965 /* 966 * When a sequential read accesses a page several times, 967 * only mark it as accessed the first time. 968 */ 969 if (prev_index != index || offset != prev_offset) 970 mark_page_accessed(page); 971 prev_index = index; 972 973 /* 974 * Ok, we have the page, and it's up-to-date, so 975 * now we can copy it to user space... 976 * 977 * The actor routine returns how many bytes were actually used.. 978 * NOTE! This may not be the same as how much of a user buffer 979 * we filled up (we may be padding etc), so we can only update 980 * "pos" here (the actor routine has to update the user buffer 981 * pointers and the remaining count). 982 */ 983 ret = actor(desc, page, offset, nr); 984 offset += ret; 985 index += offset >> PAGE_CACHE_SHIFT; 986 offset &= ~PAGE_CACHE_MASK; 987 prev_offset = offset; 988 989 page_cache_release(page); 990 if (ret == nr && desc->count) 991 continue; 992 goto out; 993 994page_not_up_to_date: 995 /* Get exclusive access to the page ... */ 996 if (lock_page_killable(page)) 997 goto readpage_eio; 998 999 /* Did it get truncated before we got the lock? */ 1000 if (!page->mapping) { 1001 unlock_page(page); 1002 page_cache_release(page); 1003 continue; 1004 } 1005 1006 /* Did somebody else fill it already? */ 1007 if (PageUptodate(page)) { 1008 unlock_page(page); 1009 goto page_ok; 1010 } 1011 1012readpage: 1013 /* Start the actual read. The read will unlock the page. */ 1014 error = mapping->a_ops->readpage(filp, page); 1015 1016 if (unlikely(error)) { 1017 if (error == AOP_TRUNCATED_PAGE) { 1018 page_cache_release(page); 1019 goto find_page; 1020 } 1021 goto readpage_error; 1022 } 1023 1024 if (!PageUptodate(page)) { 1025 if (lock_page_killable(page)) 1026 goto readpage_eio; 1027 if (!PageUptodate(page)) { 1028 if (page->mapping == NULL) { 1029 /* 1030 * invalidate_inode_pages got it 1031 */ 1032 unlock_page(page); 1033 page_cache_release(page); 1034 goto find_page; 1035 } 1036 unlock_page(page); 1037 shrink_readahead_size_eio(filp, ra); 1038 goto readpage_eio; 1039 } 1040 unlock_page(page); 1041 } 1042 1043 goto page_ok; 1044 1045readpage_eio: 1046 error = -EIO; 1047readpage_error: 1048 /* UHHUH! A synchronous read error occurred. Report it */ 1049 desc->error = error; 1050 page_cache_release(page); 1051 goto out; 1052 1053no_cached_page: 1054 /* 1055 * Ok, it wasn't cached, so we need to create a new 1056 * page.. 1057 */ 1058 page = page_cache_alloc_cold(mapping); 1059 if (!page) { 1060 desc->error = -ENOMEM; 1061 goto out; 1062 } 1063 error = add_to_page_cache_lru(page, mapping, 1064 index, GFP_KERNEL); 1065 if (error) { 1066 page_cache_release(page); 1067 if (error == -EEXIST) 1068 goto find_page; 1069 desc->error = error; 1070 goto out; 1071 } 1072 goto readpage; 1073 } 1074 1075out: 1076 ra->prev_pos = prev_index; 1077 ra->prev_pos <<= PAGE_CACHE_SHIFT; 1078 ra->prev_pos |= prev_offset; 1079 1080 *ppos = ((loff_t)index << PAGE_CACHE_SHIFT) + offset; 1081 if (filp) 1082 file_accessed(filp); 1083} 1084EXPORT_SYMBOL(do_generic_mapping_read); 1085 1086int file_read_actor(read_descriptor_t *desc, struct page *page, 1087 unsigned long offset, unsigned long size) 1088{ 1089 char *kaddr; 1090 unsigned long left, count = desc->count; 1091 1092 if (size > count) 1093 size = count; 1094 1095 /* 1096 * Faults on the destination of a read are common, so do it before 1097 * taking the kmap. 1098 */ 1099 if (!fault_in_pages_writeable(desc->arg.buf, size)) { 1100 kaddr = kmap_atomic(page, KM_USER0); 1101 left = __copy_to_user_inatomic(desc->arg.buf, 1102 kaddr + offset, size); 1103 kunmap_atomic(kaddr, KM_USER0); 1104 if (left == 0) 1105 goto success; 1106 } 1107 1108 /* Do it the slow way */ 1109 kaddr = kmap(page); 1110 left = __copy_to_user(desc->arg.buf, kaddr + offset, size); 1111 kunmap(page); 1112 1113 if (left) { 1114 size -= left; 1115 desc->error = -EFAULT; 1116 } 1117success: 1118 desc->count = count - size; 1119 desc->written += size; 1120 desc->arg.buf += size; 1121 return size; 1122} 1123 1124/* 1125 * Performs necessary checks before doing a write 1126 * @iov: io vector request 1127 * @nr_segs: number of segments in the iovec 1128 * @count: number of bytes to write 1129 * @access_flags: type of access: %VERIFY_READ or %VERIFY_WRITE 1130 * 1131 * Adjust number of segments and amount of bytes to write (nr_segs should be 1132 * properly initialized first). Returns appropriate error code that caller 1133 * should return or zero in case that write should be allowed. 1134 */ 1135int generic_segment_checks(const struct iovec *iov, 1136 unsigned long *nr_segs, size_t *count, int access_flags) 1137{ 1138 unsigned long seg; 1139 size_t cnt = 0; 1140 for (seg = 0; seg < *nr_segs; seg++) { 1141 const struct iovec *iv = &iov[seg]; 1142 1143 /* 1144 * If any segment has a negative length, or the cumulative 1145 * length ever wraps negative then return -EINVAL. 1146 */ 1147 cnt += iv->iov_len; 1148 if (unlikely((ssize_t)(cnt|iv->iov_len) < 0)) 1149 return -EINVAL; 1150 if (access_ok(access_flags, iv->iov_base, iv->iov_len)) 1151 continue; 1152 if (seg == 0) 1153 return -EFAULT; 1154 *nr_segs = seg; 1155 cnt -= iv->iov_len; /* This segment is no good */ 1156 break; 1157 } 1158 *count = cnt; 1159 return 0; 1160} 1161EXPORT_SYMBOL(generic_segment_checks); 1162 1163/** 1164 * generic_file_aio_read - generic filesystem read routine 1165 * @iocb: kernel I/O control block 1166 * @iov: io vector request 1167 * @nr_segs: number of segments in the iovec 1168 * @pos: current file position 1169 * 1170 * This is the "read()" routine for all filesystems 1171 * that can use the page cache directly. 1172 */ 1173ssize_t 1174generic_file_aio_read(struct kiocb *iocb, const struct iovec *iov, 1175 unsigned long nr_segs, loff_t pos) 1176{ 1177 struct file *filp = iocb->ki_filp; 1178 ssize_t retval; 1179 unsigned long seg; 1180 size_t count; 1181 loff_t *ppos = &iocb->ki_pos; 1182 1183 count = 0; 1184 retval = generic_segment_checks(iov, &nr_segs, &count, VERIFY_WRITE); 1185 if (retval) 1186 return retval; 1187 1188 /* coalesce the iovecs and go direct-to-BIO for O_DIRECT */ 1189 if (filp->f_flags & O_DIRECT) { 1190 loff_t size; 1191 struct address_space *mapping; 1192 struct inode *inode; 1193 1194 mapping = filp->f_mapping; 1195 inode = mapping->host; 1196 retval = 0; 1197 if (!count) 1198 goto out; /* skip atime */ 1199 size = i_size_read(inode); 1200 if (pos < size) { 1201 retval = generic_file_direct_IO(READ, iocb, 1202 iov, pos, nr_segs); 1203 if (retval > 0) 1204 *ppos = pos + retval; 1205 } 1206 if (likely(retval != 0)) { 1207 file_accessed(filp); 1208 goto out; 1209 } 1210 } 1211 1212 retval = 0; 1213 if (count) { 1214 for (seg = 0; seg < nr_segs; seg++) { 1215 read_descriptor_t desc; 1216 1217 desc.written = 0; 1218 desc.arg.buf = iov[seg].iov_base; 1219 desc.count = iov[seg].iov_len; 1220 if (desc.count == 0) 1221 continue; 1222 desc.error = 0; 1223 do_generic_file_read(filp,ppos,&desc,file_read_actor); 1224 retval += desc.written; 1225 if (desc.error) { 1226 retval = retval ?: desc.error; 1227 break; 1228 } 1229 if (desc.count > 0) 1230 break; 1231 } 1232 } 1233out: 1234 return retval; 1235} 1236EXPORT_SYMBOL(generic_file_aio_read); 1237 1238static ssize_t 1239do_readahead(struct address_space *mapping, struct file *filp, 1240 pgoff_t index, unsigned long nr) 1241{ 1242 if (!mapping || !mapping->a_ops || !mapping->a_ops->readpage) 1243 return -EINVAL; 1244 1245 force_page_cache_readahead(mapping, filp, index, 1246 max_sane_readahead(nr)); 1247 return 0; 1248} 1249 1250asmlinkage ssize_t sys_readahead(int fd, loff_t offset, size_t count) 1251{ 1252 ssize_t ret; 1253 struct file *file; 1254 1255 ret = -EBADF; 1256 file = fget(fd); 1257 if (file) { 1258 if (file->f_mode & FMODE_READ) { 1259 struct address_space *mapping = file->f_mapping; 1260 pgoff_t start = offset >> PAGE_CACHE_SHIFT; 1261 pgoff_t end = (offset + count - 1) >> PAGE_CACHE_SHIFT; 1262 unsigned long len = end - start + 1; 1263 ret = do_readahead(mapping, file, start, len); 1264 } 1265 fput(file); 1266 } 1267 return ret; 1268} 1269 1270#ifdef CONFIG_MMU 1271/** 1272 * page_cache_read - adds requested page to the page cache if not already there 1273 * @file: file to read 1274 * @offset: page index 1275 * 1276 * This adds the requested page to the page cache if it isn't already there, 1277 * and schedules an I/O to read in its contents from disk. 1278 */ 1279static int page_cache_read(struct file *file, pgoff_t offset) 1280{ 1281 struct address_space *mapping = file->f_mapping; 1282 struct page *page; 1283 int ret; 1284 1285 do { 1286 page = page_cache_alloc_cold(mapping); 1287 if (!page) 1288 return -ENOMEM; 1289 1290 ret = add_to_page_cache_lru(page, mapping, offset, GFP_KERNEL); 1291 if (ret == 0) 1292 ret = mapping->a_ops->readpage(file, page); 1293 else if (ret == -EEXIST) 1294 ret = 0; /* losing race to add is OK */ 1295 1296 page_cache_release(page); 1297 1298 } while (ret == AOP_TRUNCATED_PAGE); 1299 1300 return ret; 1301} 1302 1303#define MMAP_LOTSAMISS (100) 1304 1305/** 1306 * filemap_fault - read in file data for page fault handling 1307 * @vma: vma in which the fault was taken 1308 * @vmf: struct vm_fault containing details of the fault 1309 * 1310 * filemap_fault() is invoked via the vma operations vector for a 1311 * mapped memory region to read in file data during a page fault. 1312 * 1313 * The goto's are kind of ugly, but this streamlines the normal case of having 1314 * it in the page cache, and handles the special cases reasonably without 1315 * having a lot of duplicated code. 1316 */ 1317int filemap_fault(struct vm_area_struct *vma, struct vm_fault *vmf) 1318{ 1319 int error; 1320 struct file *file = vma->vm_file; 1321 struct address_space *mapping = file->f_mapping; 1322 struct file_ra_state *ra = &file->f_ra; 1323 struct inode *inode = mapping->host; 1324 struct page *page; 1325 unsigned long size; 1326 int did_readaround = 0; 1327 int ret = 0; 1328 1329 size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT; 1330 if (vmf->pgoff >= size) 1331 return VM_FAULT_SIGBUS; 1332 1333 /* If we don't want any read-ahead, don't bother */ 1334 if (VM_RandomReadHint(vma)) 1335 goto no_cached_page; 1336 1337 /* 1338 * Do we have something in the page cache already? 1339 */ 1340retry_find: 1341 page = find_lock_page(mapping, vmf->pgoff); 1342 /* 1343 * For sequential accesses, we use the generic readahead logic. 1344 */ 1345 if (VM_SequentialReadHint(vma)) { 1346 if (!page) { 1347 page_cache_sync_readahead(mapping, ra, file, 1348 vmf->pgoff, 1); 1349 page = find_lock_page(mapping, vmf->pgoff); 1350 if (!page) 1351 goto no_cached_page; 1352 } 1353 if (PageReadahead(page)) { 1354 page_cache_async_readahead(mapping, ra, file, page, 1355 vmf->pgoff, 1); 1356 } 1357 } 1358 1359 if (!page) { 1360 unsigned long ra_pages; 1361 1362 ra->mmap_miss++; 1363 1364 /* 1365 * Do we miss much more than hit in this file? If so, 1366 * stop bothering with read-ahead. It will only hurt. 1367 */ 1368 if (ra->mmap_miss > MMAP_LOTSAMISS) 1369 goto no_cached_page; 1370 1371 /* 1372 * To keep the pgmajfault counter straight, we need to 1373 * check did_readaround, as this is an inner loop. 1374 */ 1375 if (!did_readaround) { 1376 ret = VM_FAULT_MAJOR; 1377 count_vm_event(PGMAJFAULT); 1378 } 1379 did_readaround = 1; 1380 ra_pages = max_sane_readahead(file->f_ra.ra_pages); 1381 if (ra_pages) { 1382 pgoff_t start = 0; 1383 1384 if (vmf->pgoff > ra_pages / 2) 1385 start = vmf->pgoff - ra_pages / 2; 1386 do_page_cache_readahead(mapping, file, start, ra_pages); 1387 } 1388 page = find_lock_page(mapping, vmf->pgoff); 1389 if (!page) 1390 goto no_cached_page; 1391 } 1392 1393 if (!did_readaround) 1394 ra->mmap_miss--; 1395 1396 /* 1397 * We have a locked page in the page cache, now we need to check 1398 * that it's up-to-date. If not, it is going to be due to an error. 1399 */ 1400 if (unlikely(!PageUptodate(page))) 1401 goto page_not_uptodate; 1402 1403 /* Must recheck i_size under page lock */ 1404 size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT; 1405 if (unlikely(vmf->pgoff >= size)) { 1406 unlock_page(page); 1407 page_cache_release(page); 1408 return VM_FAULT_SIGBUS; 1409 } 1410 1411 /* 1412 * Found the page and have a reference on it. 1413 */ 1414 mark_page_accessed(page); 1415 ra->prev_pos = (loff_t)page->index << PAGE_CACHE_SHIFT; 1416 vmf->page = page; 1417 return ret | VM_FAULT_LOCKED; 1418 1419no_cached_page: 1420 /* 1421 * We're only likely to ever get here if MADV_RANDOM is in 1422 * effect. 1423 */ 1424 error = page_cache_read(file, vmf->pgoff); 1425 1426 /* 1427 * The page we want has now been added to the page cache. 1428 * In the unlikely event that someone removed it in the 1429 * meantime, we'll just come back here and read it again. 1430 */ 1431 if (error >= 0) 1432 goto retry_find; 1433 1434 /* 1435 * An error return from page_cache_read can result if the 1436 * system is low on memory, or a problem occurs while trying 1437 * to schedule I/O. 1438 */ 1439 if (error == -ENOMEM) 1440 return VM_FAULT_OOM; 1441 return VM_FAULT_SIGBUS; 1442 1443page_not_uptodate: 1444 /* IO error path */ 1445 if (!did_readaround) { 1446 ret = VM_FAULT_MAJOR; 1447 count_vm_event(PGMAJFAULT); 1448 } 1449 1450 /* 1451 * Umm, take care of errors if the page isn't up-to-date. 1452 * Try to re-read it _once_. We do this synchronously, 1453 * because there really aren't any performance issues here 1454 * and we need to check for errors. 1455 */ 1456 ClearPageError(page); 1457 error = mapping->a_ops->readpage(file, page); 1458 page_cache_release(page); 1459 1460 if (!error || error == AOP_TRUNCATED_PAGE) 1461 goto retry_find; 1462 1463 /* Things didn't work out. Return zero to tell the mm layer so. */ 1464 shrink_readahead_size_eio(file, ra); 1465 return VM_FAULT_SIGBUS; 1466} 1467EXPORT_SYMBOL(filemap_fault); 1468 1469struct vm_operations_struct generic_file_vm_ops = { 1470 .fault = filemap_fault, 1471}; 1472 1473/* This is used for a general mmap of a disk file */ 1474 1475int generic_file_mmap(struct file * file, struct vm_area_struct * vma) 1476{ 1477 struct address_space *mapping = file->f_mapping; 1478 1479 if (!mapping->a_ops->readpage) 1480 return -ENOEXEC; 1481 file_accessed(file); 1482 vma->vm_ops = &generic_file_vm_ops; 1483 vma->vm_flags |= VM_CAN_NONLINEAR; 1484 return 0; 1485} 1486 1487/* 1488 * This is for filesystems which do not implement ->writepage. 1489 */ 1490int generic_file_readonly_mmap(struct file *file, struct vm_area_struct *vma) 1491{ 1492 if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_MAYWRITE)) 1493 return -EINVAL; 1494 return generic_file_mmap(file, vma); 1495} 1496#else 1497int generic_file_mmap(struct file * file, struct vm_area_struct * vma) 1498{ 1499 return -ENOSYS; 1500} 1501int generic_file_readonly_mmap(struct file * file, struct vm_area_struct * vma) 1502{ 1503 return -ENOSYS; 1504} 1505#endif /* CONFIG_MMU */ 1506 1507EXPORT_SYMBOL(generic_file_mmap); 1508EXPORT_SYMBOL(generic_file_readonly_mmap); 1509 1510static struct page *__read_cache_page(struct address_space *mapping, 1511 pgoff_t index, 1512 int (*filler)(void *,struct page*), 1513 void *data) 1514{ 1515 struct page *page; 1516 int err; 1517repeat: 1518 page = find_get_page(mapping, index); 1519 if (!page) { 1520 page = page_cache_alloc_cold(mapping); 1521 if (!page) 1522 return ERR_PTR(-ENOMEM); 1523 err = add_to_page_cache_lru(page, mapping, index, GFP_KERNEL); 1524 if (unlikely(err)) { 1525 page_cache_release(page); 1526 if (err == -EEXIST) 1527 goto repeat; 1528 /* Presumably ENOMEM for radix tree node */ 1529 return ERR_PTR(err); 1530 } 1531 err = filler(data, page); 1532 if (err < 0) { 1533 page_cache_release(page); 1534 page = ERR_PTR(err); 1535 } 1536 } 1537 return page; 1538} 1539 1540/* 1541 * Same as read_cache_page, but don't wait for page to become unlocked 1542 * after submitting it to the filler. 1543 */ 1544struct page *read_cache_page_async(struct address_space *mapping, 1545 pgoff_t index, 1546 int (*filler)(void *,struct page*), 1547 void *data) 1548{ 1549 struct page *page; 1550 int err; 1551 1552retry: 1553 page = __read_cache_page(mapping, index, filler, data); 1554 if (IS_ERR(page)) 1555 return page; 1556 if (PageUptodate(page)) 1557 goto out; 1558 1559 lock_page(page); 1560 if (!page->mapping) { 1561 unlock_page(page); 1562 page_cache_release(page); 1563 goto retry; 1564 } 1565 if (PageUptodate(page)) { 1566 unlock_page(page); 1567 goto out; 1568 } 1569 err = filler(data, page); 1570 if (err < 0) { 1571 page_cache_release(page); 1572 return ERR_PTR(err); 1573 } 1574out: 1575 mark_page_accessed(page); 1576 return page; 1577} 1578EXPORT_SYMBOL(read_cache_page_async); 1579 1580/** 1581 * read_cache_page - read into page cache, fill it if needed 1582 * @mapping: the page's address_space 1583 * @index: the page index 1584 * @filler: function to perform the read 1585 * @data: destination for read data 1586 * 1587 * Read into the page cache. If a page already exists, and PageUptodate() is 1588 * not set, try to fill the page then wait for it to become unlocked. 1589 * 1590 * If the page does not get brought uptodate, return -EIO. 1591 */ 1592struct page *read_cache_page(struct address_space *mapping, 1593 pgoff_t index, 1594 int (*filler)(void *,struct page*), 1595 void *data) 1596{ 1597 struct page *page; 1598 1599 page = read_cache_page_async(mapping, index, filler, data); 1600 if (IS_ERR(page)) 1601 goto out; 1602 wait_on_page_locked(page); 1603 if (!PageUptodate(page)) { 1604 page_cache_release(page); 1605 page = ERR_PTR(-EIO); 1606 } 1607 out: 1608 return page; 1609} 1610EXPORT_SYMBOL(read_cache_page); 1611 1612/* 1613 * The logic we want is 1614 * 1615 * if suid or (sgid and xgrp) 1616 * remove privs 1617 */ 1618int should_remove_suid(struct dentry *dentry) 1619{ 1620 mode_t mode = dentry->d_inode->i_mode; 1621 int kill = 0; 1622 1623 /* suid always must be killed */ 1624 if (unlikely(mode & S_ISUID)) 1625 kill = ATTR_KILL_SUID; 1626 1627 /* 1628 * sgid without any exec bits is just a mandatory locking mark; leave 1629 * it alone. If some exec bits are set, it's a real sgid; kill it. 1630 */ 1631 if (unlikely((mode & S_ISGID) && (mode & S_IXGRP))) 1632 kill |= ATTR_KILL_SGID; 1633 1634 if (unlikely(kill && !capable(CAP_FSETID))) 1635 return kill; 1636 1637 return 0; 1638} 1639EXPORT_SYMBOL(should_remove_suid); 1640 1641int __remove_suid(struct dentry *dentry, int kill) 1642{ 1643 struct iattr newattrs; 1644 1645 newattrs.ia_valid = ATTR_FORCE | kill; 1646 return notify_change(dentry, &newattrs); 1647} 1648 1649int remove_suid(struct dentry *dentry) 1650{ 1651 int killsuid = should_remove_suid(dentry); 1652 int killpriv = security_inode_need_killpriv(dentry); 1653 int error = 0; 1654 1655 if (killpriv < 0) 1656 return killpriv; 1657 if (killpriv) 1658 error = security_inode_killpriv(dentry); 1659 if (!error && killsuid) 1660 error = __remove_suid(dentry, killsuid); 1661 1662 return error; 1663} 1664EXPORT_SYMBOL(remove_suid); 1665 1666static size_t __iovec_copy_from_user_inatomic(char *vaddr, 1667 const struct iovec *iov, size_t base, size_t bytes) 1668{ 1669 size_t copied = 0, left = 0; 1670 1671 while (bytes) { 1672 char __user *buf = iov->iov_base + base; 1673 int copy = min(bytes, iov->iov_len - base); 1674 1675 base = 0; 1676 left = __copy_from_user_inatomic_nocache(vaddr, buf, copy); 1677 copied += copy; 1678 bytes -= copy; 1679 vaddr += copy; 1680 iov++; 1681 1682 if (unlikely(left)) 1683 break; 1684 } 1685 return copied - left; 1686} 1687 1688/* 1689 * Copy as much as we can into the page and return the number of bytes which 1690 * were sucessfully copied. If a fault is encountered then return the number of 1691 * bytes which were copied. 1692 */ 1693size_t iov_iter_copy_from_user_atomic(struct page *page, 1694 struct iov_iter *i, unsigned long offset, size_t bytes) 1695{ 1696 char *kaddr; 1697 size_t copied; 1698 1699 BUG_ON(!in_atomic()); 1700 kaddr = kmap_atomic(page, KM_USER0); 1701 if (likely(i->nr_segs == 1)) { 1702 int left; 1703 char __user *buf = i->iov->iov_base + i->iov_offset; 1704 left = __copy_from_user_inatomic_nocache(kaddr + offset, 1705 buf, bytes); 1706 copied = bytes - left; 1707 } else { 1708 copied = __iovec_copy_from_user_inatomic(kaddr + offset, 1709 i->iov, i->iov_offset, bytes); 1710 } 1711 kunmap_atomic(kaddr, KM_USER0); 1712 1713 return copied; 1714} 1715EXPORT_SYMBOL(iov_iter_copy_from_user_atomic); 1716 1717/* 1718 * This has the same sideeffects and return value as 1719 * iov_iter_copy_from_user_atomic(). 1720 * The difference is that it attempts to resolve faults. 1721 * Page must not be locked. 1722 */ 1723size_t iov_iter_copy_from_user(struct page *page, 1724 struct iov_iter *i, unsigned long offset, size_t bytes) 1725{ 1726 char *kaddr; 1727 size_t copied; 1728 1729 kaddr = kmap(page); 1730 if (likely(i->nr_segs == 1)) { 1731 int left; 1732 char __user *buf = i->iov->iov_base + i->iov_offset; 1733 left = __copy_from_user_nocache(kaddr + offset, buf, bytes); 1734 copied = bytes - left; 1735 } else { 1736 copied = __iovec_copy_from_user_inatomic(kaddr + offset, 1737 i->iov, i->iov_offset, bytes); 1738 } 1739 kunmap(page); 1740 return copied; 1741} 1742EXPORT_SYMBOL(iov_iter_copy_from_user); 1743 1744static void __iov_iter_advance_iov(struct iov_iter *i, size_t bytes) 1745{ 1746 if (likely(i->nr_segs == 1)) { 1747 i->iov_offset += bytes; 1748 } else { 1749 const struct iovec *iov = i->iov; 1750 size_t base = i->iov_offset; 1751 1752 /* 1753 * The !iov->iov_len check ensures we skip over unlikely 1754 * zero-length segments. 1755 */ 1756 while (bytes || !iov->iov_len) { 1757 int copy = min(bytes, iov->iov_len - base); 1758 1759 bytes -= copy; 1760 base += copy; 1761 if (iov->iov_len == base) { 1762 iov++; 1763 base = 0; 1764 } 1765 } 1766 i->iov = iov; 1767 i->iov_offset = base; 1768 } 1769} 1770 1771void iov_iter_advance(struct iov_iter *i, size_t bytes) 1772{ 1773 BUG_ON(i->count < bytes); 1774 1775 __iov_iter_advance_iov(i, bytes); 1776 i->count -= bytes; 1777} 1778EXPORT_SYMBOL(iov_iter_advance); 1779 1780/* 1781 * Fault in the first iovec of the given iov_iter, to a maximum length 1782 * of bytes. Returns 0 on success, or non-zero if the memory could not be 1783 * accessed (ie. because it is an invalid address). 1784 * 1785 * writev-intensive code may want this to prefault several iovecs -- that 1786 * would be possible (callers must not rely on the fact that _only_ the 1787 * first iovec will be faulted with the current implementation). 1788 */ 1789int iov_iter_fault_in_readable(struct iov_iter *i, size_t bytes) 1790{ 1791 char __user *buf = i->iov->iov_base + i->iov_offset; 1792 bytes = min(bytes, i->iov->iov_len - i->iov_offset); 1793 return fault_in_pages_readable(buf, bytes); 1794} 1795EXPORT_SYMBOL(iov_iter_fault_in_readable); 1796 1797/* 1798 * Return the count of just the current iov_iter segment. 1799 */ 1800size_t iov_iter_single_seg_count(struct iov_iter *i) 1801{ 1802 const struct iovec *iov = i->iov; 1803 if (i->nr_segs == 1) 1804 return i->count; 1805 else 1806 return min(i->count, iov->iov_len - i->iov_offset); 1807} 1808EXPORT_SYMBOL(iov_iter_single_seg_count); 1809 1810/* 1811 * Performs necessary checks before doing a write 1812 * 1813 * Can adjust writing position or amount of bytes to write. 1814 * Returns appropriate error code that caller should return or 1815 * zero in case that write should be allowed. 1816 */ 1817inline int generic_write_checks(struct file *file, loff_t *pos, size_t *count, int isblk) 1818{ 1819 struct inode *inode = file->f_mapping->host; 1820 unsigned long limit = current->signal->rlim[RLIMIT_FSIZE].rlim_cur; 1821 1822 if (unlikely(*pos < 0)) 1823 return -EINVAL; 1824 1825 if (!isblk) { 1826 /* FIXME: this is for backwards compatibility with 2.4 */ 1827 if (file->f_flags & O_APPEND) 1828 *pos = i_size_read(inode); 1829 1830 if (limit != RLIM_INFINITY) { 1831 if (*pos >= limit) { 1832 send_sig(SIGXFSZ, current, 0); 1833 return -EFBIG; 1834 } 1835 if (*count > limit - (typeof(limit))*pos) { 1836 *count = limit - (typeof(limit))*pos; 1837 } 1838 } 1839 } 1840 1841 /* 1842 * LFS rule 1843 */ 1844 if (unlikely(*pos + *count > MAX_NON_LFS && 1845 !(file->f_flags & O_LARGEFILE))) { 1846 if (*pos >= MAX_NON_LFS) { 1847 return -EFBIG; 1848 } 1849 if (*count > MAX_NON_LFS - (unsigned long)*pos) { 1850 *count = MAX_NON_LFS - (unsigned long)*pos; 1851 } 1852 } 1853 1854 /* 1855 * Are we about to exceed the fs block limit ? 1856 * 1857 * If we have written data it becomes a short write. If we have 1858 * exceeded without writing data we send a signal and return EFBIG. 1859 * Linus frestrict idea will clean these up nicely.. 1860 */ 1861 if (likely(!isblk)) { 1862 if (unlikely(*pos >= inode->i_sb->s_maxbytes)) { 1863 if (*count || *pos > inode->i_sb->s_maxbytes) { 1864 return -EFBIG; 1865 } 1866 /* zero-length writes at ->s_maxbytes are OK */ 1867 } 1868 1869 if (unlikely(*pos + *count > inode->i_sb->s_maxbytes)) 1870 *count = inode->i_sb->s_maxbytes - *pos; 1871 } else { 1872#ifdef CONFIG_BLOCK 1873 loff_t isize; 1874 if (bdev_read_only(I_BDEV(inode))) 1875 return -EPERM; 1876 isize = i_size_read(inode); 1877 if (*pos >= isize) { 1878 if (*count || *pos > isize) 1879 return -ENOSPC; 1880 } 1881 1882 if (*pos + *count > isize) 1883 *count = isize - *pos; 1884#else 1885 return -EPERM; 1886#endif 1887 } 1888 return 0; 1889} 1890EXPORT_SYMBOL(generic_write_checks); 1891 1892int pagecache_write_begin(struct file *file, struct address_space *mapping, 1893 loff_t pos, unsigned len, unsigned flags, 1894 struct page **pagep, void **fsdata) 1895{ 1896 const struct address_space_operations *aops = mapping->a_ops; 1897 1898 if (aops->write_begin) { 1899 return aops->write_begin(file, mapping, pos, len, flags, 1900 pagep, fsdata); 1901 } else { 1902 int ret; 1903 pgoff_t index = pos >> PAGE_CACHE_SHIFT; 1904 unsigned offset = pos & (PAGE_CACHE_SIZE - 1); 1905 struct inode *inode = mapping->host; 1906 struct page *page; 1907again: 1908 page = __grab_cache_page(mapping, index); 1909 *pagep = page; 1910 if (!page) 1911 return -ENOMEM; 1912 1913 if (flags & AOP_FLAG_UNINTERRUPTIBLE && !PageUptodate(page)) { 1914 /* 1915 * There is no way to resolve a short write situation 1916 * for a !Uptodate page (except by double copying in 1917 * the caller done by generic_perform_write_2copy). 1918 * 1919 * Instead, we have to bring it uptodate here. 1920 */ 1921 ret = aops->readpage(file, page); 1922 page_cache_release(page); 1923 if (ret) { 1924 if (ret == AOP_TRUNCATED_PAGE) 1925 goto again; 1926 return ret; 1927 } 1928 goto again; 1929 } 1930 1931 ret = aops->prepare_write(file, page, offset, offset+len); 1932 if (ret) { 1933 unlock_page(page); 1934 page_cache_release(page); 1935 if (pos + len > inode->i_size) 1936 vmtruncate(inode, inode->i_size); 1937 } 1938 return ret; 1939 } 1940} 1941EXPORT_SYMBOL(pagecache_write_begin); 1942 1943int pagecache_write_end(struct file *file, struct address_space *mapping, 1944 loff_t pos, unsigned len, unsigned copied, 1945 struct page *page, void *fsdata) 1946{ 1947 const struct address_space_operations *aops = mapping->a_ops; 1948 int ret; 1949 1950 if (aops->write_end) { 1951 mark_page_accessed(page); 1952 ret = aops->write_end(file, mapping, pos, len, copied, 1953 page, fsdata); 1954 } else { 1955 unsigned offset = pos & (PAGE_CACHE_SIZE - 1); 1956 struct inode *inode = mapping->host; 1957 1958 flush_dcache_page(page); 1959 ret = aops->commit_write(file, page, offset, offset+len); 1960 unlock_page(page); 1961 mark_page_accessed(page); 1962 page_cache_release(page); 1963 1964 if (ret < 0) { 1965 if (pos + len > inode->i_size) 1966 vmtruncate(inode, inode->i_size); 1967 } else if (ret > 0) 1968 ret = min_t(size_t, copied, ret); 1969 else 1970 ret = copied; 1971 } 1972 1973 return ret; 1974} 1975EXPORT_SYMBOL(pagecache_write_end); 1976 1977ssize_t 1978generic_file_direct_write(struct kiocb *iocb, const struct iovec *iov, 1979 unsigned long *nr_segs, loff_t pos, loff_t *ppos, 1980 size_t count, size_t ocount) 1981{ 1982 struct file *file = iocb->ki_filp; 1983 struct address_space *mapping = file->f_mapping; 1984 struct inode *inode = mapping->host; 1985 ssize_t written; 1986 1987 if (count != ocount) 1988 *nr_segs = iov_shorten((struct iovec *)iov, *nr_segs, count); 1989 1990 written = generic_file_direct_IO(WRITE, iocb, iov, pos, *nr_segs); 1991 if (written > 0) { 1992 loff_t end = pos + written; 1993 if (end > i_size_read(inode) && !S_ISBLK(inode->i_mode)) { 1994 i_size_write(inode, end); 1995 mark_inode_dirty(inode); 1996 } 1997 *ppos = end; 1998 } 1999 2000 /* 2001 * Sync the fs metadata but not the minor inode changes and 2002 * of course not the data as we did direct DMA for the IO. 2003 * i_mutex is held, which protects generic_osync_inode() from 2004 * livelocking. AIO O_DIRECT ops attempt to sync metadata here. 2005 */ 2006 if ((written >= 0 || written == -EIOCBQUEUED) && 2007 ((file->f_flags & O_SYNC) || IS_SYNC(inode))) { 2008 int err = generic_osync_inode(inode, mapping, OSYNC_METADATA); 2009 if (err < 0) 2010 written = err; 2011 } 2012 return written; 2013} 2014EXPORT_SYMBOL(generic_file_direct_write); 2015 2016/* 2017 * Find or create a page at the given pagecache position. Return the locked 2018 * page. This function is specifically for buffered writes. 2019 */ 2020struct page *__grab_cache_page(struct address_space *mapping, pgoff_t index) 2021{ 2022 int status; 2023 struct page *page; 2024repeat: 2025 page = find_lock_page(mapping, index); 2026 if (likely(page)) 2027 return page; 2028 2029 page = page_cache_alloc(mapping); 2030 if (!page) 2031 return NULL; 2032 status = add_to_page_cache_lru(page, mapping, index, GFP_KERNEL); 2033 if (unlikely(status)) { 2034 page_cache_release(page); 2035 if (status == -EEXIST) 2036 goto repeat; 2037 return NULL; 2038 } 2039 return page; 2040} 2041EXPORT_SYMBOL(__grab_cache_page); 2042 2043static ssize_t generic_perform_write_2copy(struct file *file, 2044 struct iov_iter *i, loff_t pos) 2045{ 2046 struct address_space *mapping = file->f_mapping; 2047 const struct address_space_operations *a_ops = mapping->a_ops; 2048 struct inode *inode = mapping->host; 2049 long status = 0; 2050 ssize_t written = 0; 2051 2052 do { 2053 struct page *src_page; 2054 struct page *page; 2055 pgoff_t index; /* Pagecache index for current page */ 2056 unsigned long offset; /* Offset into pagecache page */ 2057 unsigned long bytes; /* Bytes to write to page */ 2058 size_t copied; /* Bytes copied from user */ 2059 2060 offset = (pos & (PAGE_CACHE_SIZE - 1)); 2061 index = pos >> PAGE_CACHE_SHIFT; 2062 bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset, 2063 iov_iter_count(i)); 2064 2065 /* 2066 * a non-NULL src_page indicates that we're doing the 2067 * copy via get_user_pages and kmap. 2068 */ 2069 src_page = NULL; 2070 2071 /* 2072 * Bring in the user page that we will copy from _first_. 2073 * Otherwise there's a nasty deadlock on copying from the 2074 * same page as we're writing to, without it being marked 2075 * up-to-date. 2076 * 2077 * Not only is this an optimisation, but it is also required 2078 * to check that the address is actually valid, when atomic 2079 * usercopies are used, below. 2080 */ 2081 if (unlikely(iov_iter_fault_in_readable(i, bytes))) { 2082 status = -EFAULT; 2083 break; 2084 } 2085 2086 page = __grab_cache_page(mapping, index); 2087 if (!page) { 2088 status = -ENOMEM; 2089 break; 2090 } 2091 2092 /* 2093 * non-uptodate pages cannot cope with short copies, and we 2094 * cannot take a pagefault with the destination page locked. 2095 * So pin the source page to copy it. 2096 */ 2097 if (!PageUptodate(page) && !segment_eq(get_fs(), KERNEL_DS)) { 2098 unlock_page(page); 2099 2100 src_page = alloc_page(GFP_KERNEL); 2101 if (!src_page) { 2102 page_cache_release(page); 2103 status = -ENOMEM; 2104 break; 2105 } 2106 2107 /* 2108 * Cannot get_user_pages with a page locked for the 2109 * same reason as we can't take a page fault with a 2110 * page locked (as explained below). 2111 */ 2112 copied = iov_iter_copy_from_user(src_page, i, 2113 offset, bytes); 2114 if (unlikely(copied == 0)) { 2115 status = -EFAULT; 2116 page_cache_release(page); 2117 page_cache_release(src_page); 2118 break; 2119 } 2120 bytes = copied; 2121 2122 lock_page(page); 2123 /* 2124 * Can't handle the page going uptodate here, because 2125 * that means we would use non-atomic usercopies, which 2126 * zero out the tail of the page, which can cause 2127 * zeroes to become transiently visible. We could just 2128 * use a non-zeroing copy, but the APIs aren't too 2129 * consistent. 2130 */ 2131 if (unlikely(!page->mapping || PageUptodate(page))) { 2132 unlock_page(page); 2133 page_cache_release(page); 2134 page_cache_release(src_page); 2135 continue; 2136 } 2137 } 2138 2139 status = a_ops->prepare_write(file, page, offset, offset+bytes); 2140 if (unlikely(status)) 2141 goto fs_write_aop_error; 2142 2143 if (!src_page) { 2144 /* 2145 * Must not enter the pagefault handler here, because 2146 * we hold the page lock, so we might recursively 2147 * deadlock on the same lock, or get an ABBA deadlock 2148 * against a different lock, or against the mmap_sem 2149 * (which nests outside the page lock). So increment 2150 * preempt count, and use _atomic usercopies. 2151 * 2152 * The page is uptodate so we are OK to encounter a 2153 * short copy: if unmodified parts of the page are 2154 * marked dirty and written out to disk, it doesn't 2155 * really matter. 2156 */ 2157 pagefault_disable(); 2158 copied = iov_iter_copy_from_user_atomic(page, i, 2159 offset, bytes); 2160 pagefault_enable(); 2161 } else { 2162 void *src, *dst; 2163 src = kmap_atomic(src_page, KM_USER0); 2164 dst = kmap_atomic(page, KM_USER1); 2165 memcpy(dst + offset, src + offset, bytes); 2166 kunmap_atomic(dst, KM_USER1); 2167 kunmap_atomic(src, KM_USER0); 2168 copied = bytes; 2169 } 2170 flush_dcache_page(page); 2171 2172 status = a_ops->commit_write(file, page, offset, offset+bytes); 2173 if (unlikely(status < 0)) 2174 goto fs_write_aop_error; 2175 if (unlikely(status > 0)) /* filesystem did partial write */ 2176 copied = min_t(size_t, copied, status); 2177 2178 unlock_page(page); 2179 mark_page_accessed(page); 2180 page_cache_release(page); 2181 if (src_page) 2182 page_cache_release(src_page); 2183 2184 iov_iter_advance(i, copied); 2185 pos += copied; 2186 written += copied; 2187 2188 balance_dirty_pages_ratelimited(mapping); 2189 cond_resched(); 2190 continue; 2191 2192fs_write_aop_error: 2193 unlock_page(page); 2194 page_cache_release(page); 2195 if (src_page) 2196 page_cache_release(src_page); 2197 2198 /* 2199 * prepare_write() may have instantiated a few blocks 2200 * outside i_size. Trim these off again. Don't need 2201 * i_size_read because we hold i_mutex. 2202 */ 2203 if (pos + bytes > inode->i_size) 2204 vmtruncate(inode, inode->i_size); 2205 break; 2206 } while (iov_iter_count(i)); 2207 2208 return written ? written : status; 2209} 2210 2211static ssize_t generic_perform_write(struct file *file, 2212 struct iov_iter *i, loff_t pos) 2213{ 2214 struct address_space *mapping = file->f_mapping; 2215 const struct address_space_operations *a_ops = mapping->a_ops; 2216 long status = 0; 2217 ssize_t written = 0; 2218 unsigned int flags = 0; 2219 2220 /* 2221 * Copies from kernel address space cannot fail (NFSD is a big user). 2222 */ 2223 if (segment_eq(get_fs(), KERNEL_DS)) 2224 flags |= AOP_FLAG_UNINTERRUPTIBLE; 2225 2226 do { 2227 struct page *page; 2228 pgoff_t index; /* Pagecache index for current page */ 2229 unsigned long offset; /* Offset into pagecache page */ 2230 unsigned long bytes; /* Bytes to write to page */ 2231 size_t copied; /* Bytes copied from user */ 2232 void *fsdata; 2233 2234 offset = (pos & (PAGE_CACHE_SIZE - 1)); 2235 index = pos >> PAGE_CACHE_SHIFT; 2236 bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset, 2237 iov_iter_count(i)); 2238 2239again: 2240 2241 /* 2242 * Bring in the user page that we will copy from _first_. 2243 * Otherwise there's a nasty deadlock on copying from the 2244 * same page as we're writing to, without it being marked 2245 * up-to-date. 2246 * 2247 * Not only is this an optimisation, but it is also required 2248 * to check that the address is actually valid, when atomic 2249 * usercopies are used, below. 2250 */ 2251 if (unlikely(iov_iter_fault_in_readable(i, bytes))) { 2252 status = -EFAULT; 2253 break; 2254 } 2255 2256 status = a_ops->write_begin(file, mapping, pos, bytes, flags, 2257 &page, &fsdata); 2258 if (unlikely(status)) 2259 break; 2260 2261 pagefault_disable(); 2262 copied = iov_iter_copy_from_user_atomic(page, i, offset, bytes); 2263 pagefault_enable(); 2264 flush_dcache_page(page); 2265 2266 status = a_ops->write_end(file, mapping, pos, bytes, copied, 2267 page, fsdata); 2268 if (unlikely(status < 0)) 2269 break; 2270 copied = status; 2271 2272 cond_resched(); 2273 2274 iov_iter_advance(i, copied); 2275 if (unlikely(copied == 0)) { 2276 /* 2277 * If we were unable to copy any data at all, we must 2278 * fall back to a single segment length write. 2279 * 2280 * If we didn't fallback here, we could livelock 2281 * because not all segments in the iov can be copied at 2282 * once without a pagefault. 2283 */ 2284 bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset, 2285 iov_iter_single_seg_count(i)); 2286 goto again; 2287 } 2288 pos += copied; 2289 written += copied; 2290 2291 balance_dirty_pages_ratelimited(mapping); 2292 2293 } while (iov_iter_count(i)); 2294 2295 return written ? written : status; 2296} 2297 2298ssize_t 2299generic_file_buffered_write(struct kiocb *iocb, const struct iovec *iov, 2300 unsigned long nr_segs, loff_t pos, loff_t *ppos, 2301 size_t count, ssize_t written) 2302{ 2303 struct file *file = iocb->ki_filp; 2304 struct address_space *mapping = file->f_mapping; 2305 const struct address_space_operations *a_ops = mapping->a_ops; 2306 struct inode *inode = mapping->host; 2307 ssize_t status; 2308 struct iov_iter i; 2309 2310 iov_iter_init(&i, iov, nr_segs, count, written); 2311 if (a_ops->write_begin) 2312 status = generic_perform_write(file, &i, pos); 2313 else 2314 status = generic_perform_write_2copy(file, &i, pos); 2315 2316 if (likely(status >= 0)) { 2317 written += status; 2318 *ppos = pos + status; 2319 2320 /* 2321 * For now, when the user asks for O_SYNC, we'll actually give 2322 * O_DSYNC 2323 */ 2324 if (unlikely((file->f_flags & O_SYNC) || IS_SYNC(inode))) { 2325 if (!a_ops->writepage || !is_sync_kiocb(iocb)) 2326 status = generic_osync_inode(inode, mapping, 2327 OSYNC_METADATA|OSYNC_DATA); 2328 } 2329 } 2330 2331 /* 2332 * If we get here for O_DIRECT writes then we must have fallen through 2333 * to buffered writes (block instantiation inside i_size). So we sync 2334 * the file data here, to try to honour O_DIRECT expectations. 2335 */ 2336 if (unlikely(file->f_flags & O_DIRECT) && written) 2337 status = filemap_write_and_wait(mapping); 2338 2339 return written ? written : status; 2340} 2341EXPORT_SYMBOL(generic_file_buffered_write); 2342 2343static ssize_t 2344__generic_file_aio_write_nolock(struct kiocb *iocb, const struct iovec *iov, 2345 unsigned long nr_segs, loff_t *ppos) 2346{ 2347 struct file *file = iocb->ki_filp; 2348 struct address_space * mapping = file->f_mapping; 2349 size_t ocount; /* original count */ 2350 size_t count; /* after file limit checks */ 2351 struct inode *inode = mapping->host; 2352 loff_t pos; 2353 ssize_t written; 2354 ssize_t err; 2355 2356 ocount = 0; 2357 err = generic_segment_checks(iov, &nr_segs, &ocount, VERIFY_READ); 2358 if (err) 2359 return err; 2360 2361 count = ocount; 2362 pos = *ppos; 2363 2364 vfs_check_frozen(inode->i_sb, SB_FREEZE_WRITE); 2365 2366 /* We can write back this queue in page reclaim */ 2367 current->backing_dev_info = mapping->backing_dev_info; 2368 written = 0; 2369 2370 err = generic_write_checks(file, &pos, &count, S_ISBLK(inode->i_mode)); 2371 if (err) 2372 goto out; 2373 2374 if (count == 0) 2375 goto out; 2376 2377 err = remove_suid(file->f_path.dentry); 2378 if (err) 2379 goto out; 2380 2381 file_update_time(file); 2382 2383 /* coalesce the iovecs and go direct-to-BIO for O_DIRECT */ 2384 if (unlikely(file->f_flags & O_DIRECT)) { 2385 loff_t endbyte; 2386 ssize_t written_buffered; 2387 2388 written = generic_file_direct_write(iocb, iov, &nr_segs, pos, 2389 ppos, count, ocount); 2390 if (written < 0 || written == count) 2391 goto out; 2392 /* 2393 * direct-io write to a hole: fall through to buffered I/O 2394 * for completing the rest of the request. 2395 */ 2396 pos += written; 2397 count -= written; 2398 written_buffered = generic_file_buffered_write(iocb, iov, 2399 nr_segs, pos, ppos, count, 2400 written); 2401 /* 2402 * If generic_file_buffered_write() retuned a synchronous error 2403 * then we want to return the number of bytes which were 2404 * direct-written, or the error code if that was zero. Note 2405 * that this differs from normal direct-io semantics, which 2406 * will return -EFOO even if some bytes were written. 2407 */ 2408 if (written_buffered < 0) { 2409 err = written_buffered; 2410 goto out; 2411 } 2412 2413 /* 2414 * We need to ensure that the page cache pages are written to 2415 * disk and invalidated to preserve the expected O_DIRECT 2416 * semantics. 2417 */ 2418 endbyte = pos + written_buffered - written - 1; 2419 err = do_sync_mapping_range(file->f_mapping, pos, endbyte, 2420 SYNC_FILE_RANGE_WAIT_BEFORE| 2421 SYNC_FILE_RANGE_WRITE| 2422 SYNC_FILE_RANGE_WAIT_AFTER); 2423 if (err == 0) { 2424 written = written_buffered; 2425 invalidate_mapping_pages(mapping, 2426 pos >> PAGE_CACHE_SHIFT, 2427 endbyte >> PAGE_CACHE_SHIFT); 2428 } else { 2429 /* 2430 * We don't know how much we wrote, so just return 2431 * the number of bytes which were direct-written 2432 */ 2433 } 2434 } else { 2435 written = generic_file_buffered_write(iocb, iov, nr_segs, 2436 pos, ppos, count, written); 2437 } 2438out: 2439 current->backing_dev_info = NULL; 2440 return written ? written : err; 2441} 2442 2443ssize_t generic_file_aio_write_nolock(struct kiocb *iocb, 2444 const struct iovec *iov, unsigned long nr_segs, loff_t pos) 2445{ 2446 struct file *file = iocb->ki_filp; 2447 struct address_space *mapping = file->f_mapping; 2448 struct inode *inode = mapping->host; 2449 ssize_t ret; 2450 2451 BUG_ON(iocb->ki_pos != pos); 2452 2453 ret = __generic_file_aio_write_nolock(iocb, iov, nr_segs, 2454 &iocb->ki_pos); 2455 2456 if (ret > 0 && ((file->f_flags & O_SYNC) || IS_SYNC(inode))) { 2457 ssize_t err; 2458 2459 err = sync_page_range_nolock(inode, mapping, pos, ret); 2460 if (err < 0) 2461 ret = err; 2462 } 2463 return ret; 2464} 2465EXPORT_SYMBOL(generic_file_aio_write_nolock); 2466 2467ssize_t generic_file_aio_write(struct kiocb *iocb, const struct iovec *iov, 2468 unsigned long nr_segs, loff_t pos) 2469{ 2470 struct file *file = iocb->ki_filp; 2471 struct address_space *mapping = file->f_mapping; 2472 struct inode *inode = mapping->host; 2473 ssize_t ret; 2474 2475 BUG_ON(iocb->ki_pos != pos); 2476 2477 mutex_lock(&inode->i_mutex); 2478 ret = __generic_file_aio_write_nolock(iocb, iov, nr_segs, 2479 &iocb->ki_pos); 2480 mutex_unlock(&inode->i_mutex); 2481 2482 if (ret > 0 && ((file->f_flags & O_SYNC) || IS_SYNC(inode))) { 2483 ssize_t err; 2484 2485 err = sync_page_range(inode, mapping, pos, ret); 2486 if (err < 0) 2487 ret = err; 2488 } 2489 return ret; 2490} 2491EXPORT_SYMBOL(generic_file_aio_write); 2492 2493/* 2494 * Called under i_mutex for writes to S_ISREG files. Returns -EIO if something 2495 * went wrong during pagecache shootdown. 2496 */ 2497static ssize_t 2498generic_file_direct_IO(int rw, struct kiocb *iocb, const struct iovec *iov, 2499 loff_t offset, unsigned long nr_segs) 2500{ 2501 struct file *file = iocb->ki_filp; 2502 struct address_space *mapping = file->f_mapping; 2503 ssize_t retval; 2504 size_t write_len; 2505 pgoff_t end = 0; /* silence gcc */ 2506 2507 /* 2508 * If it's a write, unmap all mmappings of the file up-front. This 2509 * will cause any pte dirty bits to be propagated into the pageframes 2510 * for the subsequent filemap_write_and_wait(). 2511 */ 2512 if (rw == WRITE) { 2513 write_len = iov_length(iov, nr_segs); 2514 end = (offset + write_len - 1) >> PAGE_CACHE_SHIFT; 2515 if (mapping_mapped(mapping)) 2516 unmap_mapping_range(mapping, offset, write_len, 0); 2517 } 2518 2519 retval = filemap_write_and_wait(mapping); 2520 if (retval) 2521 goto out; 2522 2523 /* 2524 * After a write we want buffered reads to be sure to go to disk to get 2525 * the new data. We invalidate clean cached page from the region we're 2526 * about to write. We do this *before* the write so that we can return 2527 * -EIO without clobbering -EIOCBQUEUED from ->direct_IO(). 2528 */ 2529 if (rw == WRITE && mapping->nrpages) { 2530 retval = invalidate_inode_pages2_range(mapping, 2531 offset >> PAGE_CACHE_SHIFT, end); 2532 if (retval) 2533 goto out; 2534 } 2535 2536 retval = mapping->a_ops->direct_IO(rw, iocb, iov, offset, nr_segs); 2537 2538 /* 2539 * Finally, try again to invalidate clean pages which might have been 2540 * cached by non-direct readahead, or faulted in by get_user_pages() 2541 * if the source of the write was an mmap'ed region of the file 2542 * we're writing. Either one is a pretty crazy thing to do, 2543 * so we don't support it 100%. If this invalidation 2544 * fails, tough, the write still worked... 2545 */ 2546 if (rw == WRITE && mapping->nrpages) { 2547 invalidate_inode_pages2_range(mapping, offset >> PAGE_CACHE_SHIFT, end); 2548 } 2549out: 2550 return retval; 2551} 2552 2553/** 2554 * try_to_release_page() - release old fs-specific metadata on a page 2555 * 2556 * @page: the page which the kernel is trying to free 2557 * @gfp_mask: memory allocation flags (and I/O mode) 2558 * 2559 * The address_space is to try to release any data against the page 2560 * (presumably at page->private). If the release was successful, return `1'. 2561 * Otherwise return zero. 2562 * 2563 * The @gfp_mask argument specifies whether I/O may be performed to release 2564 * this page (__GFP_IO), and whether the call may block (__GFP_WAIT). 2565 * 2566 * NOTE: @gfp_mask may go away, and this function may become non-blocking. 2567 */ 2568int try_to_release_page(struct page *page, gfp_t gfp_mask) 2569{ 2570 struct address_space * const mapping = page->mapping; 2571 2572 BUG_ON(!PageLocked(page)); 2573 if (PageWriteback(page)) 2574 return 0; 2575 2576 if (mapping && mapping->a_ops->releasepage) 2577 return mapping->a_ops->releasepage(page, gfp_mask); 2578 return try_to_free_buffers(page); 2579} 2580 2581EXPORT_SYMBOL(try_to_release_page); 2582