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