filemap.c revision ef00e08e26dd5d84271ef706262506b82195e752
1/* 2 * linux/mm/filemap.c 3 * 4 * Copyright (C) 1994-1999 Linus Torvalds 5 */ 6 7/* 8 * This file handles the generic file mmap semantics used by 9 * most "normal" filesystems (but you don't /have/ to use this: 10 * the NFS filesystem used to do this differently, for example) 11 */ 12#include <linux/module.h> 13#include <linux/slab.h> 14#include <linux/compiler.h> 15#include <linux/fs.h> 16#include <linux/uaccess.h> 17#include <linux/aio.h> 18#include <linux/capability.h> 19#include <linux/kernel_stat.h> 20#include <linux/mm.h> 21#include <linux/swap.h> 22#include <linux/mman.h> 23#include <linux/pagemap.h> 24#include <linux/file.h> 25#include <linux/uio.h> 26#include <linux/hash.h> 27#include <linux/writeback.h> 28#include <linux/backing-dev.h> 29#include <linux/pagevec.h> 30#include <linux/blkdev.h> 31#include <linux/security.h> 32#include <linux/syscalls.h> 33#include <linux/cpuset.h> 34#include <linux/hardirq.h> /* for BUG_ON(!in_atomic()) only */ 35#include <linux/memcontrol.h> 36#include <linux/mm_inline.h> /* for page_is_file_cache() */ 37#include "internal.h" 38 39/* 40 * FIXME: remove all knowledge of the buffer layer from the core VM 41 */ 42#include <linux/buffer_head.h> /* for generic_osync_inode */ 43 44#include <asm/mman.h> 45 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 the mapping's tree_lock. 114 */ 115void __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 BUG_ON(page_mapped(page)); 124 125 /* 126 * Some filesystems seem to re-dirty the page even after 127 * the VM has canceled the dirty bit (eg ext3 journaling). 128 * 129 * Fix it up by doing a final dirty accounting check after 130 * having removed the page entirely. 131 */ 132 if (PageDirty(page) && mapping_cap_account_dirty(mapping)) { 133 dec_zone_page_state(page, NR_FILE_DIRTY); 134 dec_bdi_stat(mapping->backing_dev_info, BDI_RECLAIMABLE); 135 } 136} 137 138void remove_from_page_cache(struct page *page) 139{ 140 struct address_space *mapping = page->mapping; 141 142 BUG_ON(!PageLocked(page)); 143 144 spin_lock_irq(&mapping->tree_lock); 145 __remove_from_page_cache(page); 146 spin_unlock_irq(&mapping->tree_lock); 147 mem_cgroup_uncharge_cache_page(page); 148} 149 150static int sync_page(void *word) 151{ 152 struct address_space *mapping; 153 struct page *page; 154 155 page = container_of((unsigned long *)word, struct page, flags); 156 157 /* 158 * page_mapping() is being called without PG_locked held. 159 * Some knowledge of the state and use of the page is used to 160 * reduce the requirements down to a memory barrier. 161 * The danger here is of a stale page_mapping() return value 162 * indicating a struct address_space different from the one it's 163 * associated with when it is associated with one. 164 * After smp_mb(), it's either the correct page_mapping() for 165 * the page, or an old page_mapping() and the page's own 166 * page_mapping() has gone NULL. 167 * The ->sync_page() address_space operation must tolerate 168 * page_mapping() going NULL. By an amazing coincidence, 169 * this comes about because none of the users of the page 170 * in the ->sync_page() methods make essential use of the 171 * page_mapping(), merely passing the page down to the backing 172 * device's unplug functions when it's non-NULL, which in turn 173 * ignore it for all cases but swap, where only page_private(page) is 174 * of interest. When page_mapping() does go NULL, the entire 175 * call stack gracefully ignores the page and returns. 176 * -- wli 177 */ 178 smp_mb(); 179 mapping = page_mapping(page); 180 if (mapping && mapping->a_ops && mapping->a_ops->sync_page) 181 mapping->a_ops->sync_page(page); 182 io_schedule(); 183 return 0; 184} 185 186static int sync_page_killable(void *word) 187{ 188 sync_page(word); 189 return fatal_signal_pending(current) ? -EINTR : 0; 190} 191 192/** 193 * __filemap_fdatawrite_range - start writeback on mapping dirty pages in range 194 * @mapping: address space structure to write 195 * @start: offset in bytes where the range starts 196 * @end: offset in bytes where the range ends (inclusive) 197 * @sync_mode: enable synchronous operation 198 * 199 * Start writeback against all of a mapping's dirty pages that lie 200 * within the byte offsets <start, end> inclusive. 201 * 202 * If sync_mode is WB_SYNC_ALL then this is a "data integrity" operation, as 203 * opposed to a regular memory cleansing writeback. The difference between 204 * these two operations is that if a dirty page/buffer is encountered, it must 205 * be waited upon, and not just skipped over. 206 */ 207int __filemap_fdatawrite_range(struct address_space *mapping, loff_t start, 208 loff_t end, int sync_mode) 209{ 210 int ret; 211 struct writeback_control wbc = { 212 .sync_mode = sync_mode, 213 .nr_to_write = LONG_MAX, 214 .range_start = start, 215 .range_end = end, 216 }; 217 218 if (!mapping_cap_writeback_dirty(mapping)) 219 return 0; 220 221 ret = do_writepages(mapping, &wbc); 222 return ret; 223} 224 225static inline int __filemap_fdatawrite(struct address_space *mapping, 226 int sync_mode) 227{ 228 return __filemap_fdatawrite_range(mapping, 0, LLONG_MAX, sync_mode); 229} 230 231int filemap_fdatawrite(struct address_space *mapping) 232{ 233 return __filemap_fdatawrite(mapping, WB_SYNC_ALL); 234} 235EXPORT_SYMBOL(filemap_fdatawrite); 236 237int filemap_fdatawrite_range(struct address_space *mapping, loff_t start, 238 loff_t end) 239{ 240 return __filemap_fdatawrite_range(mapping, start, end, WB_SYNC_ALL); 241} 242EXPORT_SYMBOL(filemap_fdatawrite_range); 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 - write & wait on all pages in the passed range without locking 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} 444EXPORT_SYMBOL(filemap_write_and_wait_range); 445 446/** 447 * add_to_page_cache_locked - add a locked page to the pagecache 448 * @page: page to add 449 * @mapping: the page's address_space 450 * @offset: page index 451 * @gfp_mask: page allocation mode 452 * 453 * This function is used to add a page to the pagecache. It must be locked. 454 * This function does not add the page to the LRU. The caller must do that. 455 */ 456int add_to_page_cache_locked(struct page *page, struct address_space *mapping, 457 pgoff_t offset, gfp_t gfp_mask) 458{ 459 int error; 460 461 VM_BUG_ON(!PageLocked(page)); 462 463 error = mem_cgroup_cache_charge(page, current->mm, 464 gfp_mask & GFP_RECLAIM_MASK); 465 if (error) 466 goto out; 467 468 error = radix_tree_preload(gfp_mask & ~__GFP_HIGHMEM); 469 if (error == 0) { 470 page_cache_get(page); 471 page->mapping = mapping; 472 page->index = offset; 473 474 spin_lock_irq(&mapping->tree_lock); 475 error = radix_tree_insert(&mapping->page_tree, offset, page); 476 if (likely(!error)) { 477 mapping->nrpages++; 478 __inc_zone_page_state(page, NR_FILE_PAGES); 479 spin_unlock_irq(&mapping->tree_lock); 480 } else { 481 page->mapping = NULL; 482 spin_unlock_irq(&mapping->tree_lock); 483 mem_cgroup_uncharge_cache_page(page); 484 page_cache_release(page); 485 } 486 radix_tree_preload_end(); 487 } else 488 mem_cgroup_uncharge_cache_page(page); 489out: 490 return error; 491} 492EXPORT_SYMBOL(add_to_page_cache_locked); 493 494int add_to_page_cache_lru(struct page *page, struct address_space *mapping, 495 pgoff_t offset, gfp_t gfp_mask) 496{ 497 int ret; 498 499 /* 500 * Splice_read and readahead add shmem/tmpfs pages into the page cache 501 * before shmem_readpage has a chance to mark them as SwapBacked: they 502 * need to go on the active_anon lru below, and mem_cgroup_cache_charge 503 * (called in add_to_page_cache) needs to know where they're going too. 504 */ 505 if (mapping_cap_swap_backed(mapping)) 506 SetPageSwapBacked(page); 507 508 ret = add_to_page_cache(page, mapping, offset, gfp_mask); 509 if (ret == 0) { 510 if (page_is_file_cache(page)) 511 lru_cache_add_file(page); 512 else 513 lru_cache_add_active_anon(page); 514 } 515 return ret; 516} 517EXPORT_SYMBOL_GPL(add_to_page_cache_lru); 518 519#ifdef CONFIG_NUMA 520struct page *__page_cache_alloc(gfp_t gfp) 521{ 522 if (cpuset_do_page_mem_spread()) { 523 int n = cpuset_mem_spread_node(); 524 return alloc_pages_node(n, gfp, 0); 525 } 526 return alloc_pages(gfp, 0); 527} 528EXPORT_SYMBOL(__page_cache_alloc); 529#endif 530 531static int __sleep_on_page_lock(void *word) 532{ 533 io_schedule(); 534 return 0; 535} 536 537/* 538 * In order to wait for pages to become available there must be 539 * waitqueues associated with pages. By using a hash table of 540 * waitqueues where the bucket discipline is to maintain all 541 * waiters on the same queue and wake all when any of the pages 542 * become available, and for the woken contexts to check to be 543 * sure the appropriate page became available, this saves space 544 * at a cost of "thundering herd" phenomena during rare hash 545 * collisions. 546 */ 547static wait_queue_head_t *page_waitqueue(struct page *page) 548{ 549 const struct zone *zone = page_zone(page); 550 551 return &zone->wait_table[hash_ptr(page, zone->wait_table_bits)]; 552} 553 554static inline void wake_up_page(struct page *page, int bit) 555{ 556 __wake_up_bit(page_waitqueue(page), &page->flags, bit); 557} 558 559void wait_on_page_bit(struct page *page, int bit_nr) 560{ 561 DEFINE_WAIT_BIT(wait, &page->flags, bit_nr); 562 563 if (test_bit(bit_nr, &page->flags)) 564 __wait_on_bit(page_waitqueue(page), &wait, sync_page, 565 TASK_UNINTERRUPTIBLE); 566} 567EXPORT_SYMBOL(wait_on_page_bit); 568 569/** 570 * add_page_wait_queue - Add an arbitrary waiter to a page's wait queue 571 * @page: Page defining the wait queue of interest 572 * @waiter: Waiter to add to the queue 573 * 574 * Add an arbitrary @waiter to the wait queue for the nominated @page. 575 */ 576void add_page_wait_queue(struct page *page, wait_queue_t *waiter) 577{ 578 wait_queue_head_t *q = page_waitqueue(page); 579 unsigned long flags; 580 581 spin_lock_irqsave(&q->lock, flags); 582 __add_wait_queue(q, waiter); 583 spin_unlock_irqrestore(&q->lock, flags); 584} 585EXPORT_SYMBOL_GPL(add_page_wait_queue); 586 587/** 588 * unlock_page - unlock a locked page 589 * @page: the page 590 * 591 * Unlocks the page and wakes up sleepers in ___wait_on_page_locked(). 592 * Also wakes sleepers in wait_on_page_writeback() because the wakeup 593 * mechananism between PageLocked pages and PageWriteback pages is shared. 594 * But that's OK - sleepers in wait_on_page_writeback() just go back to sleep. 595 * 596 * The mb is necessary to enforce ordering between the clear_bit and the read 597 * of the waitqueue (to avoid SMP races with a parallel wait_on_page_locked()). 598 */ 599void unlock_page(struct page *page) 600{ 601 VM_BUG_ON(!PageLocked(page)); 602 clear_bit_unlock(PG_locked, &page->flags); 603 smp_mb__after_clear_bit(); 604 wake_up_page(page, PG_locked); 605} 606EXPORT_SYMBOL(unlock_page); 607 608/** 609 * end_page_writeback - end writeback against a page 610 * @page: the page 611 */ 612void end_page_writeback(struct page *page) 613{ 614 if (TestClearPageReclaim(page)) 615 rotate_reclaimable_page(page); 616 617 if (!test_clear_page_writeback(page)) 618 BUG(); 619 620 smp_mb__after_clear_bit(); 621 wake_up_page(page, PG_writeback); 622} 623EXPORT_SYMBOL(end_page_writeback); 624 625/** 626 * __lock_page - get a lock on the page, assuming we need to sleep to get it 627 * @page: the page to lock 628 * 629 * Ugly. Running sync_page() in state TASK_UNINTERRUPTIBLE is scary. If some 630 * random driver's requestfn sets TASK_RUNNING, we could busywait. However 631 * chances are that on the second loop, the block layer's plug list is empty, 632 * so sync_page() will then return in state TASK_UNINTERRUPTIBLE. 633 */ 634void __lock_page(struct page *page) 635{ 636 DEFINE_WAIT_BIT(wait, &page->flags, PG_locked); 637 638 __wait_on_bit_lock(page_waitqueue(page), &wait, sync_page, 639 TASK_UNINTERRUPTIBLE); 640} 641EXPORT_SYMBOL(__lock_page); 642 643int __lock_page_killable(struct page *page) 644{ 645 DEFINE_WAIT_BIT(wait, &page->flags, PG_locked); 646 647 return __wait_on_bit_lock(page_waitqueue(page), &wait, 648 sync_page_killable, TASK_KILLABLE); 649} 650EXPORT_SYMBOL_GPL(__lock_page_killable); 651 652/** 653 * __lock_page_nosync - get a lock on the page, without calling sync_page() 654 * @page: the page to lock 655 * 656 * Variant of lock_page that does not require the caller to hold a reference 657 * on the page's mapping. 658 */ 659void __lock_page_nosync(struct page *page) 660{ 661 DEFINE_WAIT_BIT(wait, &page->flags, PG_locked); 662 __wait_on_bit_lock(page_waitqueue(page), &wait, __sleep_on_page_lock, 663 TASK_UNINTERRUPTIBLE); 664} 665 666/** 667 * find_get_page - find and get a page reference 668 * @mapping: the address_space to search 669 * @offset: the page index 670 * 671 * Is there a pagecache struct page at the given (mapping, offset) tuple? 672 * If yes, increment its refcount and return it; if no, return NULL. 673 */ 674struct page *find_get_page(struct address_space *mapping, pgoff_t offset) 675{ 676 void **pagep; 677 struct page *page; 678 679 rcu_read_lock(); 680repeat: 681 page = NULL; 682 pagep = radix_tree_lookup_slot(&mapping->page_tree, offset); 683 if (pagep) { 684 page = radix_tree_deref_slot(pagep); 685 if (unlikely(!page || page == RADIX_TREE_RETRY)) 686 goto repeat; 687 688 if (!page_cache_get_speculative(page)) 689 goto repeat; 690 691 /* 692 * Has the page moved? 693 * This is part of the lockless pagecache protocol. See 694 * include/linux/pagemap.h for details. 695 */ 696 if (unlikely(page != *pagep)) { 697 page_cache_release(page); 698 goto repeat; 699 } 700 } 701 rcu_read_unlock(); 702 703 return page; 704} 705EXPORT_SYMBOL(find_get_page); 706 707/** 708 * find_lock_page - locate, pin and lock a pagecache page 709 * @mapping: the address_space to search 710 * @offset: the page index 711 * 712 * Locates the desired pagecache page, locks it, increments its reference 713 * count and returns its address. 714 * 715 * Returns zero if the page was not present. find_lock_page() may sleep. 716 */ 717struct page *find_lock_page(struct address_space *mapping, pgoff_t offset) 718{ 719 struct page *page; 720 721repeat: 722 page = find_get_page(mapping, offset); 723 if (page) { 724 lock_page(page); 725 /* Has the page been truncated? */ 726 if (unlikely(page->mapping != mapping)) { 727 unlock_page(page); 728 page_cache_release(page); 729 goto repeat; 730 } 731 VM_BUG_ON(page->index != offset); 732 } 733 return page; 734} 735EXPORT_SYMBOL(find_lock_page); 736 737/** 738 * find_or_create_page - locate or add a pagecache page 739 * @mapping: the page's address_space 740 * @index: the page's index into the mapping 741 * @gfp_mask: page allocation mode 742 * 743 * Locates a page in the pagecache. If the page is not present, a new page 744 * is allocated using @gfp_mask and is added to the pagecache and to the VM's 745 * LRU list. The returned page is locked and has its reference count 746 * incremented. 747 * 748 * find_or_create_page() may sleep, even if @gfp_flags specifies an atomic 749 * allocation! 750 * 751 * find_or_create_page() returns the desired page's address, or zero on 752 * memory exhaustion. 753 */ 754struct page *find_or_create_page(struct address_space *mapping, 755 pgoff_t index, gfp_t gfp_mask) 756{ 757 struct page *page; 758 int err; 759repeat: 760 page = find_lock_page(mapping, index); 761 if (!page) { 762 page = __page_cache_alloc(gfp_mask); 763 if (!page) 764 return NULL; 765 /* 766 * We want a regular kernel memory (not highmem or DMA etc) 767 * allocation for the radix tree nodes, but we need to honour 768 * the context-specific requirements the caller has asked for. 769 * GFP_RECLAIM_MASK collects those requirements. 770 */ 771 err = add_to_page_cache_lru(page, mapping, index, 772 (gfp_mask & GFP_RECLAIM_MASK)); 773 if (unlikely(err)) { 774 page_cache_release(page); 775 page = NULL; 776 if (err == -EEXIST) 777 goto repeat; 778 } 779 } 780 return page; 781} 782EXPORT_SYMBOL(find_or_create_page); 783 784/** 785 * find_get_pages - gang pagecache lookup 786 * @mapping: The address_space to search 787 * @start: The starting page index 788 * @nr_pages: The maximum number of pages 789 * @pages: Where the resulting pages are placed 790 * 791 * find_get_pages() will search for and return a group of up to 792 * @nr_pages pages in the mapping. The pages are placed at @pages. 793 * find_get_pages() takes a reference against the returned pages. 794 * 795 * The search returns a group of mapping-contiguous pages with ascending 796 * indexes. There may be holes in the indices due to not-present pages. 797 * 798 * find_get_pages() returns the number of pages which were found. 799 */ 800unsigned find_get_pages(struct address_space *mapping, pgoff_t start, 801 unsigned int nr_pages, struct page **pages) 802{ 803 unsigned int i; 804 unsigned int ret; 805 unsigned int nr_found; 806 807 rcu_read_lock(); 808restart: 809 nr_found = radix_tree_gang_lookup_slot(&mapping->page_tree, 810 (void ***)pages, start, nr_pages); 811 ret = 0; 812 for (i = 0; i < nr_found; i++) { 813 struct page *page; 814repeat: 815 page = radix_tree_deref_slot((void **)pages[i]); 816 if (unlikely(!page)) 817 continue; 818 /* 819 * this can only trigger if nr_found == 1, making livelock 820 * a non issue. 821 */ 822 if (unlikely(page == RADIX_TREE_RETRY)) 823 goto restart; 824 825 if (!page_cache_get_speculative(page)) 826 goto repeat; 827 828 /* Has the page moved? */ 829 if (unlikely(page != *((void **)pages[i]))) { 830 page_cache_release(page); 831 goto repeat; 832 } 833 834 pages[ret] = page; 835 ret++; 836 } 837 rcu_read_unlock(); 838 return ret; 839} 840 841/** 842 * find_get_pages_contig - gang contiguous pagecache lookup 843 * @mapping: The address_space to search 844 * @index: The starting page index 845 * @nr_pages: The maximum number of pages 846 * @pages: Where the resulting pages are placed 847 * 848 * find_get_pages_contig() works exactly like find_get_pages(), except 849 * that the returned number of pages are guaranteed to be contiguous. 850 * 851 * find_get_pages_contig() returns the number of pages which were found. 852 */ 853unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t index, 854 unsigned int nr_pages, struct page **pages) 855{ 856 unsigned int i; 857 unsigned int ret; 858 unsigned int nr_found; 859 860 rcu_read_lock(); 861restart: 862 nr_found = radix_tree_gang_lookup_slot(&mapping->page_tree, 863 (void ***)pages, index, nr_pages); 864 ret = 0; 865 for (i = 0; i < nr_found; i++) { 866 struct page *page; 867repeat: 868 page = radix_tree_deref_slot((void **)pages[i]); 869 if (unlikely(!page)) 870 continue; 871 /* 872 * this can only trigger if nr_found == 1, making livelock 873 * a non issue. 874 */ 875 if (unlikely(page == RADIX_TREE_RETRY)) 876 goto restart; 877 878 if (page->mapping == NULL || page->index != index) 879 break; 880 881 if (!page_cache_get_speculative(page)) 882 goto repeat; 883 884 /* Has the page moved? */ 885 if (unlikely(page != *((void **)pages[i]))) { 886 page_cache_release(page); 887 goto repeat; 888 } 889 890 pages[ret] = page; 891 ret++; 892 index++; 893 } 894 rcu_read_unlock(); 895 return ret; 896} 897EXPORT_SYMBOL(find_get_pages_contig); 898 899/** 900 * find_get_pages_tag - find and return pages that match @tag 901 * @mapping: the address_space to search 902 * @index: the starting page index 903 * @tag: the tag index 904 * @nr_pages: the maximum number of pages 905 * @pages: where the resulting pages are placed 906 * 907 * Like find_get_pages, except we only return pages which are tagged with 908 * @tag. We update @index to index the next page for the traversal. 909 */ 910unsigned find_get_pages_tag(struct address_space *mapping, pgoff_t *index, 911 int tag, unsigned int nr_pages, struct page **pages) 912{ 913 unsigned int i; 914 unsigned int ret; 915 unsigned int nr_found; 916 917 rcu_read_lock(); 918restart: 919 nr_found = radix_tree_gang_lookup_tag_slot(&mapping->page_tree, 920 (void ***)pages, *index, nr_pages, tag); 921 ret = 0; 922 for (i = 0; i < nr_found; i++) { 923 struct page *page; 924repeat: 925 page = radix_tree_deref_slot((void **)pages[i]); 926 if (unlikely(!page)) 927 continue; 928 /* 929 * this can only trigger if nr_found == 1, making livelock 930 * a non issue. 931 */ 932 if (unlikely(page == RADIX_TREE_RETRY)) 933 goto restart; 934 935 if (!page_cache_get_speculative(page)) 936 goto repeat; 937 938 /* Has the page moved? */ 939 if (unlikely(page != *((void **)pages[i]))) { 940 page_cache_release(page); 941 goto repeat; 942 } 943 944 pages[ret] = page; 945 ret++; 946 } 947 rcu_read_unlock(); 948 949 if (ret) 950 *index = pages[ret - 1]->index + 1; 951 952 return ret; 953} 954EXPORT_SYMBOL(find_get_pages_tag); 955 956/** 957 * grab_cache_page_nowait - returns locked page at given index in given cache 958 * @mapping: target address_space 959 * @index: the page index 960 * 961 * Same as grab_cache_page(), but do not wait if the page is unavailable. 962 * This is intended for speculative data generators, where the data can 963 * be regenerated if the page couldn't be grabbed. This routine should 964 * be safe to call while holding the lock for another page. 965 * 966 * Clear __GFP_FS when allocating the page to avoid recursion into the fs 967 * and deadlock against the caller's locked page. 968 */ 969struct page * 970grab_cache_page_nowait(struct address_space *mapping, pgoff_t index) 971{ 972 struct page *page = find_get_page(mapping, index); 973 974 if (page) { 975 if (trylock_page(page)) 976 return page; 977 page_cache_release(page); 978 return NULL; 979 } 980 page = __page_cache_alloc(mapping_gfp_mask(mapping) & ~__GFP_FS); 981 if (page && add_to_page_cache_lru(page, mapping, index, GFP_NOFS)) { 982 page_cache_release(page); 983 page = NULL; 984 } 985 return page; 986} 987EXPORT_SYMBOL(grab_cache_page_nowait); 988 989/* 990 * CD/DVDs are error prone. When a medium error occurs, the driver may fail 991 * a _large_ part of the i/o request. Imagine the worst scenario: 992 * 993 * ---R__________________________________________B__________ 994 * ^ reading here ^ bad block(assume 4k) 995 * 996 * read(R) => miss => readahead(R...B) => media error => frustrating retries 997 * => failing the whole request => read(R) => read(R+1) => 998 * readahead(R+1...B+1) => bang => read(R+2) => read(R+3) => 999 * readahead(R+3...B+2) => bang => read(R+3) => read(R+4) => 1000 * readahead(R+4...B+3) => bang => read(R+4) => read(R+5) => ...... 1001 * 1002 * It is going insane. Fix it by quickly scaling down the readahead size. 1003 */ 1004static void shrink_readahead_size_eio(struct file *filp, 1005 struct file_ra_state *ra) 1006{ 1007 if (!ra->ra_pages) 1008 return; 1009 1010 ra->ra_pages /= 4; 1011} 1012 1013/** 1014 * do_generic_file_read - generic file read routine 1015 * @filp: the file to read 1016 * @ppos: current file position 1017 * @desc: read_descriptor 1018 * @actor: read method 1019 * 1020 * This is a generic file read routine, and uses the 1021 * mapping->a_ops->readpage() function for the actual low-level stuff. 1022 * 1023 * This is really ugly. But the goto's actually try to clarify some 1024 * of the logic when it comes to error handling etc. 1025 */ 1026static void do_generic_file_read(struct file *filp, loff_t *ppos, 1027 read_descriptor_t *desc, read_actor_t actor) 1028{ 1029 struct address_space *mapping = filp->f_mapping; 1030 struct inode *inode = mapping->host; 1031 struct file_ra_state *ra = &filp->f_ra; 1032 pgoff_t index; 1033 pgoff_t last_index; 1034 pgoff_t prev_index; 1035 unsigned long offset; /* offset into pagecache page */ 1036 unsigned int prev_offset; 1037 int error; 1038 1039 index = *ppos >> PAGE_CACHE_SHIFT; 1040 prev_index = ra->prev_pos >> PAGE_CACHE_SHIFT; 1041 prev_offset = ra->prev_pos & (PAGE_CACHE_SIZE-1); 1042 last_index = (*ppos + desc->count + PAGE_CACHE_SIZE-1) >> PAGE_CACHE_SHIFT; 1043 offset = *ppos & ~PAGE_CACHE_MASK; 1044 1045 for (;;) { 1046 struct page *page; 1047 pgoff_t end_index; 1048 loff_t isize; 1049 unsigned long nr, ret; 1050 1051 cond_resched(); 1052find_page: 1053 page = find_get_page(mapping, index); 1054 if (!page) { 1055 page_cache_sync_readahead(mapping, 1056 ra, filp, 1057 index, last_index - index); 1058 page = find_get_page(mapping, index); 1059 if (unlikely(page == NULL)) 1060 goto no_cached_page; 1061 } 1062 if (PageReadahead(page)) { 1063 page_cache_async_readahead(mapping, 1064 ra, filp, page, 1065 index, last_index - index); 1066 } 1067 if (!PageUptodate(page)) { 1068 if (inode->i_blkbits == PAGE_CACHE_SHIFT || 1069 !mapping->a_ops->is_partially_uptodate) 1070 goto page_not_up_to_date; 1071 if (!trylock_page(page)) 1072 goto page_not_up_to_date; 1073 if (!mapping->a_ops->is_partially_uptodate(page, 1074 desc, offset)) 1075 goto page_not_up_to_date_locked; 1076 unlock_page(page); 1077 } 1078page_ok: 1079 /* 1080 * i_size must be checked after we know the page is Uptodate. 1081 * 1082 * Checking i_size after the check allows us to calculate 1083 * the correct value for "nr", which means the zero-filled 1084 * part of the page is not copied back to userspace (unless 1085 * another truncate extends the file - this is desired though). 1086 */ 1087 1088 isize = i_size_read(inode); 1089 end_index = (isize - 1) >> PAGE_CACHE_SHIFT; 1090 if (unlikely(!isize || index > end_index)) { 1091 page_cache_release(page); 1092 goto out; 1093 } 1094 1095 /* nr is the maximum number of bytes to copy from this page */ 1096 nr = PAGE_CACHE_SIZE; 1097 if (index == end_index) { 1098 nr = ((isize - 1) & ~PAGE_CACHE_MASK) + 1; 1099 if (nr <= offset) { 1100 page_cache_release(page); 1101 goto out; 1102 } 1103 } 1104 nr = nr - offset; 1105 1106 /* If users can be writing to this page using arbitrary 1107 * virtual addresses, take care about potential aliasing 1108 * before reading the page on the kernel side. 1109 */ 1110 if (mapping_writably_mapped(mapping)) 1111 flush_dcache_page(page); 1112 1113 /* 1114 * When a sequential read accesses a page several times, 1115 * only mark it as accessed the first time. 1116 */ 1117 if (prev_index != index || offset != prev_offset) 1118 mark_page_accessed(page); 1119 prev_index = index; 1120 1121 /* 1122 * Ok, we have the page, and it's up-to-date, so 1123 * now we can copy it to user space... 1124 * 1125 * The actor routine returns how many bytes were actually used.. 1126 * NOTE! This may not be the same as how much of a user buffer 1127 * we filled up (we may be padding etc), so we can only update 1128 * "pos" here (the actor routine has to update the user buffer 1129 * pointers and the remaining count). 1130 */ 1131 ret = actor(desc, page, offset, nr); 1132 offset += ret; 1133 index += offset >> PAGE_CACHE_SHIFT; 1134 offset &= ~PAGE_CACHE_MASK; 1135 prev_offset = offset; 1136 1137 page_cache_release(page); 1138 if (ret == nr && desc->count) 1139 continue; 1140 goto out; 1141 1142page_not_up_to_date: 1143 /* Get exclusive access to the page ... */ 1144 error = lock_page_killable(page); 1145 if (unlikely(error)) 1146 goto readpage_error; 1147 1148page_not_up_to_date_locked: 1149 /* Did it get truncated before we got the lock? */ 1150 if (!page->mapping) { 1151 unlock_page(page); 1152 page_cache_release(page); 1153 continue; 1154 } 1155 1156 /* Did somebody else fill it already? */ 1157 if (PageUptodate(page)) { 1158 unlock_page(page); 1159 goto page_ok; 1160 } 1161 1162readpage: 1163 /* Start the actual read. The read will unlock the page. */ 1164 error = mapping->a_ops->readpage(filp, page); 1165 1166 if (unlikely(error)) { 1167 if (error == AOP_TRUNCATED_PAGE) { 1168 page_cache_release(page); 1169 goto find_page; 1170 } 1171 goto readpage_error; 1172 } 1173 1174 if (!PageUptodate(page)) { 1175 error = lock_page_killable(page); 1176 if (unlikely(error)) 1177 goto readpage_error; 1178 if (!PageUptodate(page)) { 1179 if (page->mapping == NULL) { 1180 /* 1181 * invalidate_inode_pages got it 1182 */ 1183 unlock_page(page); 1184 page_cache_release(page); 1185 goto find_page; 1186 } 1187 unlock_page(page); 1188 shrink_readahead_size_eio(filp, ra); 1189 error = -EIO; 1190 goto readpage_error; 1191 } 1192 unlock_page(page); 1193 } 1194 1195 goto page_ok; 1196 1197readpage_error: 1198 /* UHHUH! A synchronous read error occurred. Report it */ 1199 desc->error = error; 1200 page_cache_release(page); 1201 goto out; 1202 1203no_cached_page: 1204 /* 1205 * Ok, it wasn't cached, so we need to create a new 1206 * page.. 1207 */ 1208 page = page_cache_alloc_cold(mapping); 1209 if (!page) { 1210 desc->error = -ENOMEM; 1211 goto out; 1212 } 1213 error = add_to_page_cache_lru(page, mapping, 1214 index, GFP_KERNEL); 1215 if (error) { 1216 page_cache_release(page); 1217 if (error == -EEXIST) 1218 goto find_page; 1219 desc->error = error; 1220 goto out; 1221 } 1222 goto readpage; 1223 } 1224 1225out: 1226 ra->prev_pos = prev_index; 1227 ra->prev_pos <<= PAGE_CACHE_SHIFT; 1228 ra->prev_pos |= prev_offset; 1229 1230 *ppos = ((loff_t)index << PAGE_CACHE_SHIFT) + offset; 1231 file_accessed(filp); 1232} 1233 1234int file_read_actor(read_descriptor_t *desc, struct page *page, 1235 unsigned long offset, unsigned long size) 1236{ 1237 char *kaddr; 1238 unsigned long left, count = desc->count; 1239 1240 if (size > count) 1241 size = count; 1242 1243 /* 1244 * Faults on the destination of a read are common, so do it before 1245 * taking the kmap. 1246 */ 1247 if (!fault_in_pages_writeable(desc->arg.buf, size)) { 1248 kaddr = kmap_atomic(page, KM_USER0); 1249 left = __copy_to_user_inatomic(desc->arg.buf, 1250 kaddr + offset, size); 1251 kunmap_atomic(kaddr, KM_USER0); 1252 if (left == 0) 1253 goto success; 1254 } 1255 1256 /* Do it the slow way */ 1257 kaddr = kmap(page); 1258 left = __copy_to_user(desc->arg.buf, kaddr + offset, size); 1259 kunmap(page); 1260 1261 if (left) { 1262 size -= left; 1263 desc->error = -EFAULT; 1264 } 1265success: 1266 desc->count = count - size; 1267 desc->written += size; 1268 desc->arg.buf += size; 1269 return size; 1270} 1271 1272/* 1273 * Performs necessary checks before doing a write 1274 * @iov: io vector request 1275 * @nr_segs: number of segments in the iovec 1276 * @count: number of bytes to write 1277 * @access_flags: type of access: %VERIFY_READ or %VERIFY_WRITE 1278 * 1279 * Adjust number of segments and amount of bytes to write (nr_segs should be 1280 * properly initialized first). Returns appropriate error code that caller 1281 * should return or zero in case that write should be allowed. 1282 */ 1283int generic_segment_checks(const struct iovec *iov, 1284 unsigned long *nr_segs, size_t *count, int access_flags) 1285{ 1286 unsigned long seg; 1287 size_t cnt = 0; 1288 for (seg = 0; seg < *nr_segs; seg++) { 1289 const struct iovec *iv = &iov[seg]; 1290 1291 /* 1292 * If any segment has a negative length, or the cumulative 1293 * length ever wraps negative then return -EINVAL. 1294 */ 1295 cnt += iv->iov_len; 1296 if (unlikely((ssize_t)(cnt|iv->iov_len) < 0)) 1297 return -EINVAL; 1298 if (access_ok(access_flags, iv->iov_base, iv->iov_len)) 1299 continue; 1300 if (seg == 0) 1301 return -EFAULT; 1302 *nr_segs = seg; 1303 cnt -= iv->iov_len; /* This segment is no good */ 1304 break; 1305 } 1306 *count = cnt; 1307 return 0; 1308} 1309EXPORT_SYMBOL(generic_segment_checks); 1310 1311/** 1312 * generic_file_aio_read - generic filesystem read routine 1313 * @iocb: kernel I/O control block 1314 * @iov: io vector request 1315 * @nr_segs: number of segments in the iovec 1316 * @pos: current file position 1317 * 1318 * This is the "read()" routine for all filesystems 1319 * that can use the page cache directly. 1320 */ 1321ssize_t 1322generic_file_aio_read(struct kiocb *iocb, const struct iovec *iov, 1323 unsigned long nr_segs, loff_t pos) 1324{ 1325 struct file *filp = iocb->ki_filp; 1326 ssize_t retval; 1327 unsigned long seg; 1328 size_t count; 1329 loff_t *ppos = &iocb->ki_pos; 1330 1331 count = 0; 1332 retval = generic_segment_checks(iov, &nr_segs, &count, VERIFY_WRITE); 1333 if (retval) 1334 return retval; 1335 1336 /* coalesce the iovecs and go direct-to-BIO for O_DIRECT */ 1337 if (filp->f_flags & O_DIRECT) { 1338 loff_t size; 1339 struct address_space *mapping; 1340 struct inode *inode; 1341 1342 mapping = filp->f_mapping; 1343 inode = mapping->host; 1344 if (!count) 1345 goto out; /* skip atime */ 1346 size = i_size_read(inode); 1347 if (pos < size) { 1348 retval = filemap_write_and_wait_range(mapping, pos, 1349 pos + iov_length(iov, nr_segs) - 1); 1350 if (!retval) { 1351 retval = mapping->a_ops->direct_IO(READ, iocb, 1352 iov, pos, nr_segs); 1353 } 1354 if (retval > 0) 1355 *ppos = pos + retval; 1356 if (retval) { 1357 file_accessed(filp); 1358 goto out; 1359 } 1360 } 1361 } 1362 1363 for (seg = 0; seg < nr_segs; seg++) { 1364 read_descriptor_t desc; 1365 1366 desc.written = 0; 1367 desc.arg.buf = iov[seg].iov_base; 1368 desc.count = iov[seg].iov_len; 1369 if (desc.count == 0) 1370 continue; 1371 desc.error = 0; 1372 do_generic_file_read(filp, ppos, &desc, file_read_actor); 1373 retval += desc.written; 1374 if (desc.error) { 1375 retval = retval ?: desc.error; 1376 break; 1377 } 1378 if (desc.count > 0) 1379 break; 1380 } 1381out: 1382 return retval; 1383} 1384EXPORT_SYMBOL(generic_file_aio_read); 1385 1386static ssize_t 1387do_readahead(struct address_space *mapping, struct file *filp, 1388 pgoff_t index, unsigned long nr) 1389{ 1390 if (!mapping || !mapping->a_ops || !mapping->a_ops->readpage) 1391 return -EINVAL; 1392 1393 force_page_cache_readahead(mapping, filp, index, nr); 1394 return 0; 1395} 1396 1397SYSCALL_DEFINE(readahead)(int fd, loff_t offset, size_t count) 1398{ 1399 ssize_t ret; 1400 struct file *file; 1401 1402 ret = -EBADF; 1403 file = fget(fd); 1404 if (file) { 1405 if (file->f_mode & FMODE_READ) { 1406 struct address_space *mapping = file->f_mapping; 1407 pgoff_t start = offset >> PAGE_CACHE_SHIFT; 1408 pgoff_t end = (offset + count - 1) >> PAGE_CACHE_SHIFT; 1409 unsigned long len = end - start + 1; 1410 ret = do_readahead(mapping, file, start, len); 1411 } 1412 fput(file); 1413 } 1414 return ret; 1415} 1416#ifdef CONFIG_HAVE_SYSCALL_WRAPPERS 1417asmlinkage long SyS_readahead(long fd, loff_t offset, long count) 1418{ 1419 return SYSC_readahead((int) fd, offset, (size_t) count); 1420} 1421SYSCALL_ALIAS(sys_readahead, SyS_readahead); 1422#endif 1423 1424#ifdef CONFIG_MMU 1425/** 1426 * page_cache_read - adds requested page to the page cache if not already there 1427 * @file: file to read 1428 * @offset: page index 1429 * 1430 * This adds the requested page to the page cache if it isn't already there, 1431 * and schedules an I/O to read in its contents from disk. 1432 */ 1433static int page_cache_read(struct file *file, pgoff_t offset) 1434{ 1435 struct address_space *mapping = file->f_mapping; 1436 struct page *page; 1437 int ret; 1438 1439 do { 1440 page = page_cache_alloc_cold(mapping); 1441 if (!page) 1442 return -ENOMEM; 1443 1444 ret = add_to_page_cache_lru(page, mapping, offset, GFP_KERNEL); 1445 if (ret == 0) 1446 ret = mapping->a_ops->readpage(file, page); 1447 else if (ret == -EEXIST) 1448 ret = 0; /* losing race to add is OK */ 1449 1450 page_cache_release(page); 1451 1452 } while (ret == AOP_TRUNCATED_PAGE); 1453 1454 return ret; 1455} 1456 1457#define MMAP_LOTSAMISS (100) 1458 1459/* 1460 * Synchronous readahead happens when we don't even find 1461 * a page in the page cache at all. 1462 */ 1463static void do_sync_mmap_readahead(struct vm_area_struct *vma, 1464 struct file_ra_state *ra, 1465 struct file *file, 1466 pgoff_t offset) 1467{ 1468 unsigned long ra_pages; 1469 struct address_space *mapping = file->f_mapping; 1470 1471 /* If we don't want any read-ahead, don't bother */ 1472 if (VM_RandomReadHint(vma)) 1473 return; 1474 1475 if (VM_SequentialReadHint(vma)) { 1476 page_cache_sync_readahead(mapping, ra, file, offset, 1); 1477 return; 1478 } 1479 1480 if (ra->mmap_miss < INT_MAX) 1481 ra->mmap_miss++; 1482 1483 /* 1484 * Do we miss much more than hit in this file? If so, 1485 * stop bothering with read-ahead. It will only hurt. 1486 */ 1487 if (ra->mmap_miss > MMAP_LOTSAMISS) 1488 return; 1489 1490 ra_pages = max_sane_readahead(ra->ra_pages); 1491 if (ra_pages) { 1492 pgoff_t start = 0; 1493 1494 if (offset > ra_pages / 2) 1495 start = offset - ra_pages / 2; 1496 do_page_cache_readahead(mapping, file, start, ra_pages); 1497 } 1498} 1499 1500/* 1501 * Asynchronous readahead happens when we find the page and PG_readahead, 1502 * so we want to possibly extend the readahead further.. 1503 */ 1504static void do_async_mmap_readahead(struct vm_area_struct *vma, 1505 struct file_ra_state *ra, 1506 struct file *file, 1507 struct page *page, 1508 pgoff_t offset) 1509{ 1510 struct address_space *mapping = file->f_mapping; 1511 1512 /* If we don't want any read-ahead, don't bother */ 1513 if (VM_RandomReadHint(vma)) 1514 return; 1515 if (ra->mmap_miss > 0) 1516 ra->mmap_miss--; 1517 if (PageReadahead(page)) 1518 page_cache_async_readahead(mapping, ra, file, page, offset, 1); 1519} 1520 1521/** 1522 * filemap_fault - read in file data for page fault handling 1523 * @vma: vma in which the fault was taken 1524 * @vmf: struct vm_fault containing details of the fault 1525 * 1526 * filemap_fault() is invoked via the vma operations vector for a 1527 * mapped memory region to read in file data during a page fault. 1528 * 1529 * The goto's are kind of ugly, but this streamlines the normal case of having 1530 * it in the page cache, and handles the special cases reasonably without 1531 * having a lot of duplicated code. 1532 */ 1533int filemap_fault(struct vm_area_struct *vma, struct vm_fault *vmf) 1534{ 1535 int error; 1536 struct file *file = vma->vm_file; 1537 struct address_space *mapping = file->f_mapping; 1538 struct file_ra_state *ra = &file->f_ra; 1539 struct inode *inode = mapping->host; 1540 pgoff_t offset = vmf->pgoff; 1541 struct page *page; 1542 pgoff_t size; 1543 int ret = 0; 1544 1545 size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT; 1546 if (offset >= size) 1547 return VM_FAULT_SIGBUS; 1548 1549 /* 1550 * Do we have something in the page cache already? 1551 */ 1552 page = find_get_page(mapping, offset); 1553 if (likely(page)) { 1554 /* 1555 * We found the page, so try async readahead before 1556 * waiting for the lock. 1557 */ 1558 do_async_mmap_readahead(vma, ra, file, page, offset); 1559 lock_page(page); 1560 1561 /* Did it get truncated? */ 1562 if (unlikely(page->mapping != mapping)) { 1563 unlock_page(page); 1564 put_page(page); 1565 goto no_cached_page; 1566 } 1567 } else { 1568 /* No page in the page cache at all */ 1569 do_sync_mmap_readahead(vma, ra, file, offset); 1570 count_vm_event(PGMAJFAULT); 1571 ret = VM_FAULT_MAJOR; 1572retry_find: 1573 page = find_lock_page(mapping, offset); 1574 if (!page) 1575 goto no_cached_page; 1576 } 1577 1578 /* 1579 * We have a locked page in the page cache, now we need to check 1580 * that it's up-to-date. If not, it is going to be due to an error. 1581 */ 1582 if (unlikely(!PageUptodate(page))) 1583 goto page_not_uptodate; 1584 1585 /* 1586 * Found the page and have a reference on it. 1587 * We must recheck i_size under page lock. 1588 */ 1589 size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT; 1590 if (unlikely(offset >= size)) { 1591 unlock_page(page); 1592 page_cache_release(page); 1593 return VM_FAULT_SIGBUS; 1594 } 1595 1596 ra->prev_pos = (loff_t)offset << PAGE_CACHE_SHIFT; 1597 vmf->page = page; 1598 return ret | VM_FAULT_LOCKED; 1599 1600no_cached_page: 1601 /* 1602 * We're only likely to ever get here if MADV_RANDOM is in 1603 * effect. 1604 */ 1605 error = page_cache_read(file, offset); 1606 1607 /* 1608 * The page we want has now been added to the page cache. 1609 * In the unlikely event that someone removed it in the 1610 * meantime, we'll just come back here and read it again. 1611 */ 1612 if (error >= 0) 1613 goto retry_find; 1614 1615 /* 1616 * An error return from page_cache_read can result if the 1617 * system is low on memory, or a problem occurs while trying 1618 * to schedule I/O. 1619 */ 1620 if (error == -ENOMEM) 1621 return VM_FAULT_OOM; 1622 return VM_FAULT_SIGBUS; 1623 1624page_not_uptodate: 1625 /* 1626 * Umm, take care of errors if the page isn't up-to-date. 1627 * Try to re-read it _once_. We do this synchronously, 1628 * because there really aren't any performance issues here 1629 * and we need to check for errors. 1630 */ 1631 ClearPageError(page); 1632 error = mapping->a_ops->readpage(file, page); 1633 if (!error) { 1634 wait_on_page_locked(page); 1635 if (!PageUptodate(page)) 1636 error = -EIO; 1637 } 1638 page_cache_release(page); 1639 1640 if (!error || error == AOP_TRUNCATED_PAGE) 1641 goto retry_find; 1642 1643 /* Things didn't work out. Return zero to tell the mm layer so. */ 1644 shrink_readahead_size_eio(file, ra); 1645 return VM_FAULT_SIGBUS; 1646} 1647EXPORT_SYMBOL(filemap_fault); 1648 1649struct vm_operations_struct generic_file_vm_ops = { 1650 .fault = filemap_fault, 1651}; 1652 1653/* This is used for a general mmap of a disk file */ 1654 1655int generic_file_mmap(struct file * file, struct vm_area_struct * vma) 1656{ 1657 struct address_space *mapping = file->f_mapping; 1658 1659 if (!mapping->a_ops->readpage) 1660 return -ENOEXEC; 1661 file_accessed(file); 1662 vma->vm_ops = &generic_file_vm_ops; 1663 vma->vm_flags |= VM_CAN_NONLINEAR; 1664 return 0; 1665} 1666 1667/* 1668 * This is for filesystems which do not implement ->writepage. 1669 */ 1670int generic_file_readonly_mmap(struct file *file, struct vm_area_struct *vma) 1671{ 1672 if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_MAYWRITE)) 1673 return -EINVAL; 1674 return generic_file_mmap(file, vma); 1675} 1676#else 1677int generic_file_mmap(struct file * file, struct vm_area_struct * vma) 1678{ 1679 return -ENOSYS; 1680} 1681int generic_file_readonly_mmap(struct file * file, struct vm_area_struct * vma) 1682{ 1683 return -ENOSYS; 1684} 1685#endif /* CONFIG_MMU */ 1686 1687EXPORT_SYMBOL(generic_file_mmap); 1688EXPORT_SYMBOL(generic_file_readonly_mmap); 1689 1690static struct page *__read_cache_page(struct address_space *mapping, 1691 pgoff_t index, 1692 int (*filler)(void *,struct page*), 1693 void *data) 1694{ 1695 struct page *page; 1696 int err; 1697repeat: 1698 page = find_get_page(mapping, index); 1699 if (!page) { 1700 page = page_cache_alloc_cold(mapping); 1701 if (!page) 1702 return ERR_PTR(-ENOMEM); 1703 err = add_to_page_cache_lru(page, mapping, index, GFP_KERNEL); 1704 if (unlikely(err)) { 1705 page_cache_release(page); 1706 if (err == -EEXIST) 1707 goto repeat; 1708 /* Presumably ENOMEM for radix tree node */ 1709 return ERR_PTR(err); 1710 } 1711 err = filler(data, page); 1712 if (err < 0) { 1713 page_cache_release(page); 1714 page = ERR_PTR(err); 1715 } 1716 } 1717 return page; 1718} 1719 1720/** 1721 * read_cache_page_async - read into page cache, fill it if needed 1722 * @mapping: the page's address_space 1723 * @index: the page index 1724 * @filler: function to perform the read 1725 * @data: destination for read data 1726 * 1727 * Same as read_cache_page, but don't wait for page to become unlocked 1728 * after submitting it to the filler. 1729 * 1730 * Read into the page cache. If a page already exists, and PageUptodate() is 1731 * not set, try to fill the page but don't wait for it to become unlocked. 1732 * 1733 * If the page does not get brought uptodate, return -EIO. 1734 */ 1735struct page *read_cache_page_async(struct address_space *mapping, 1736 pgoff_t index, 1737 int (*filler)(void *,struct page*), 1738 void *data) 1739{ 1740 struct page *page; 1741 int err; 1742 1743retry: 1744 page = __read_cache_page(mapping, index, filler, data); 1745 if (IS_ERR(page)) 1746 return page; 1747 if (PageUptodate(page)) 1748 goto out; 1749 1750 lock_page(page); 1751 if (!page->mapping) { 1752 unlock_page(page); 1753 page_cache_release(page); 1754 goto retry; 1755 } 1756 if (PageUptodate(page)) { 1757 unlock_page(page); 1758 goto out; 1759 } 1760 err = filler(data, page); 1761 if (err < 0) { 1762 page_cache_release(page); 1763 return ERR_PTR(err); 1764 } 1765out: 1766 mark_page_accessed(page); 1767 return page; 1768} 1769EXPORT_SYMBOL(read_cache_page_async); 1770 1771/** 1772 * read_cache_page - read into page cache, fill it if needed 1773 * @mapping: the page's address_space 1774 * @index: the page index 1775 * @filler: function to perform the read 1776 * @data: destination for read data 1777 * 1778 * Read into the page cache. If a page already exists, and PageUptodate() is 1779 * not set, try to fill the page then wait for it to become unlocked. 1780 * 1781 * If the page does not get brought uptodate, return -EIO. 1782 */ 1783struct page *read_cache_page(struct address_space *mapping, 1784 pgoff_t index, 1785 int (*filler)(void *,struct page*), 1786 void *data) 1787{ 1788 struct page *page; 1789 1790 page = read_cache_page_async(mapping, index, filler, data); 1791 if (IS_ERR(page)) 1792 goto out; 1793 wait_on_page_locked(page); 1794 if (!PageUptodate(page)) { 1795 page_cache_release(page); 1796 page = ERR_PTR(-EIO); 1797 } 1798 out: 1799 return page; 1800} 1801EXPORT_SYMBOL(read_cache_page); 1802 1803/* 1804 * The logic we want is 1805 * 1806 * if suid or (sgid and xgrp) 1807 * remove privs 1808 */ 1809int should_remove_suid(struct dentry *dentry) 1810{ 1811 mode_t mode = dentry->d_inode->i_mode; 1812 int kill = 0; 1813 1814 /* suid always must be killed */ 1815 if (unlikely(mode & S_ISUID)) 1816 kill = ATTR_KILL_SUID; 1817 1818 /* 1819 * sgid without any exec bits is just a mandatory locking mark; leave 1820 * it alone. If some exec bits are set, it's a real sgid; kill it. 1821 */ 1822 if (unlikely((mode & S_ISGID) && (mode & S_IXGRP))) 1823 kill |= ATTR_KILL_SGID; 1824 1825 if (unlikely(kill && !capable(CAP_FSETID) && S_ISREG(mode))) 1826 return kill; 1827 1828 return 0; 1829} 1830EXPORT_SYMBOL(should_remove_suid); 1831 1832static int __remove_suid(struct dentry *dentry, int kill) 1833{ 1834 struct iattr newattrs; 1835 1836 newattrs.ia_valid = ATTR_FORCE | kill; 1837 return notify_change(dentry, &newattrs); 1838} 1839 1840int file_remove_suid(struct file *file) 1841{ 1842 struct dentry *dentry = file->f_path.dentry; 1843 int killsuid = should_remove_suid(dentry); 1844 int killpriv = security_inode_need_killpriv(dentry); 1845 int error = 0; 1846 1847 if (killpriv < 0) 1848 return killpriv; 1849 if (killpriv) 1850 error = security_inode_killpriv(dentry); 1851 if (!error && killsuid) 1852 error = __remove_suid(dentry, killsuid); 1853 1854 return error; 1855} 1856EXPORT_SYMBOL(file_remove_suid); 1857 1858static size_t __iovec_copy_from_user_inatomic(char *vaddr, 1859 const struct iovec *iov, size_t base, size_t bytes) 1860{ 1861 size_t copied = 0, left = 0; 1862 1863 while (bytes) { 1864 char __user *buf = iov->iov_base + base; 1865 int copy = min(bytes, iov->iov_len - base); 1866 1867 base = 0; 1868 left = __copy_from_user_inatomic(vaddr, buf, copy); 1869 copied += copy; 1870 bytes -= copy; 1871 vaddr += copy; 1872 iov++; 1873 1874 if (unlikely(left)) 1875 break; 1876 } 1877 return copied - left; 1878} 1879 1880/* 1881 * Copy as much as we can into the page and return the number of bytes which 1882 * were sucessfully copied. If a fault is encountered then return the number of 1883 * bytes which were copied. 1884 */ 1885size_t iov_iter_copy_from_user_atomic(struct page *page, 1886 struct iov_iter *i, unsigned long offset, size_t bytes) 1887{ 1888 char *kaddr; 1889 size_t copied; 1890 1891 BUG_ON(!in_atomic()); 1892 kaddr = kmap_atomic(page, KM_USER0); 1893 if (likely(i->nr_segs == 1)) { 1894 int left; 1895 char __user *buf = i->iov->iov_base + i->iov_offset; 1896 left = __copy_from_user_inatomic(kaddr + offset, buf, bytes); 1897 copied = bytes - left; 1898 } else { 1899 copied = __iovec_copy_from_user_inatomic(kaddr + offset, 1900 i->iov, i->iov_offset, bytes); 1901 } 1902 kunmap_atomic(kaddr, KM_USER0); 1903 1904 return copied; 1905} 1906EXPORT_SYMBOL(iov_iter_copy_from_user_atomic); 1907 1908/* 1909 * This has the same sideeffects and return value as 1910 * iov_iter_copy_from_user_atomic(). 1911 * The difference is that it attempts to resolve faults. 1912 * Page must not be locked. 1913 */ 1914size_t iov_iter_copy_from_user(struct page *page, 1915 struct iov_iter *i, unsigned long offset, size_t bytes) 1916{ 1917 char *kaddr; 1918 size_t copied; 1919 1920 kaddr = kmap(page); 1921 if (likely(i->nr_segs == 1)) { 1922 int left; 1923 char __user *buf = i->iov->iov_base + i->iov_offset; 1924 left = __copy_from_user(kaddr + offset, buf, bytes); 1925 copied = bytes - left; 1926 } else { 1927 copied = __iovec_copy_from_user_inatomic(kaddr + offset, 1928 i->iov, i->iov_offset, bytes); 1929 } 1930 kunmap(page); 1931 return copied; 1932} 1933EXPORT_SYMBOL(iov_iter_copy_from_user); 1934 1935void iov_iter_advance(struct iov_iter *i, size_t bytes) 1936{ 1937 BUG_ON(i->count < bytes); 1938 1939 if (likely(i->nr_segs == 1)) { 1940 i->iov_offset += bytes; 1941 i->count -= bytes; 1942 } else { 1943 const struct iovec *iov = i->iov; 1944 size_t base = i->iov_offset; 1945 1946 /* 1947 * The !iov->iov_len check ensures we skip over unlikely 1948 * zero-length segments (without overruning the iovec). 1949 */ 1950 while (bytes || unlikely(i->count && !iov->iov_len)) { 1951 int copy; 1952 1953 copy = min(bytes, iov->iov_len - base); 1954 BUG_ON(!i->count || i->count < copy); 1955 i->count -= copy; 1956 bytes -= copy; 1957 base += copy; 1958 if (iov->iov_len == base) { 1959 iov++; 1960 base = 0; 1961 } 1962 } 1963 i->iov = iov; 1964 i->iov_offset = base; 1965 } 1966} 1967EXPORT_SYMBOL(iov_iter_advance); 1968 1969/* 1970 * Fault in the first iovec of the given iov_iter, to a maximum length 1971 * of bytes. Returns 0 on success, or non-zero if the memory could not be 1972 * accessed (ie. because it is an invalid address). 1973 * 1974 * writev-intensive code may want this to prefault several iovecs -- that 1975 * would be possible (callers must not rely on the fact that _only_ the 1976 * first iovec will be faulted with the current implementation). 1977 */ 1978int iov_iter_fault_in_readable(struct iov_iter *i, size_t bytes) 1979{ 1980 char __user *buf = i->iov->iov_base + i->iov_offset; 1981 bytes = min(bytes, i->iov->iov_len - i->iov_offset); 1982 return fault_in_pages_readable(buf, bytes); 1983} 1984EXPORT_SYMBOL(iov_iter_fault_in_readable); 1985 1986/* 1987 * Return the count of just the current iov_iter segment. 1988 */ 1989size_t iov_iter_single_seg_count(struct iov_iter *i) 1990{ 1991 const struct iovec *iov = i->iov; 1992 if (i->nr_segs == 1) 1993 return i->count; 1994 else 1995 return min(i->count, iov->iov_len - i->iov_offset); 1996} 1997EXPORT_SYMBOL(iov_iter_single_seg_count); 1998 1999/* 2000 * Performs necessary checks before doing a write 2001 * 2002 * Can adjust writing position or amount of bytes to write. 2003 * Returns appropriate error code that caller should return or 2004 * zero in case that write should be allowed. 2005 */ 2006inline int generic_write_checks(struct file *file, loff_t *pos, size_t *count, int isblk) 2007{ 2008 struct inode *inode = file->f_mapping->host; 2009 unsigned long limit = current->signal->rlim[RLIMIT_FSIZE].rlim_cur; 2010 2011 if (unlikely(*pos < 0)) 2012 return -EINVAL; 2013 2014 if (!isblk) { 2015 /* FIXME: this is for backwards compatibility with 2.4 */ 2016 if (file->f_flags & O_APPEND) 2017 *pos = i_size_read(inode); 2018 2019 if (limit != RLIM_INFINITY) { 2020 if (*pos >= limit) { 2021 send_sig(SIGXFSZ, current, 0); 2022 return -EFBIG; 2023 } 2024 if (*count > limit - (typeof(limit))*pos) { 2025 *count = limit - (typeof(limit))*pos; 2026 } 2027 } 2028 } 2029 2030 /* 2031 * LFS rule 2032 */ 2033 if (unlikely(*pos + *count > MAX_NON_LFS && 2034 !(file->f_flags & O_LARGEFILE))) { 2035 if (*pos >= MAX_NON_LFS) { 2036 return -EFBIG; 2037 } 2038 if (*count > MAX_NON_LFS - (unsigned long)*pos) { 2039 *count = MAX_NON_LFS - (unsigned long)*pos; 2040 } 2041 } 2042 2043 /* 2044 * Are we about to exceed the fs block limit ? 2045 * 2046 * If we have written data it becomes a short write. If we have 2047 * exceeded without writing data we send a signal and return EFBIG. 2048 * Linus frestrict idea will clean these up nicely.. 2049 */ 2050 if (likely(!isblk)) { 2051 if (unlikely(*pos >= inode->i_sb->s_maxbytes)) { 2052 if (*count || *pos > inode->i_sb->s_maxbytes) { 2053 return -EFBIG; 2054 } 2055 /* zero-length writes at ->s_maxbytes are OK */ 2056 } 2057 2058 if (unlikely(*pos + *count > inode->i_sb->s_maxbytes)) 2059 *count = inode->i_sb->s_maxbytes - *pos; 2060 } else { 2061#ifdef CONFIG_BLOCK 2062 loff_t isize; 2063 if (bdev_read_only(I_BDEV(inode))) 2064 return -EPERM; 2065 isize = i_size_read(inode); 2066 if (*pos >= isize) { 2067 if (*count || *pos > isize) 2068 return -ENOSPC; 2069 } 2070 2071 if (*pos + *count > isize) 2072 *count = isize - *pos; 2073#else 2074 return -EPERM; 2075#endif 2076 } 2077 return 0; 2078} 2079EXPORT_SYMBOL(generic_write_checks); 2080 2081int pagecache_write_begin(struct file *file, struct address_space *mapping, 2082 loff_t pos, unsigned len, unsigned flags, 2083 struct page **pagep, void **fsdata) 2084{ 2085 const struct address_space_operations *aops = mapping->a_ops; 2086 2087 return aops->write_begin(file, mapping, pos, len, flags, 2088 pagep, fsdata); 2089} 2090EXPORT_SYMBOL(pagecache_write_begin); 2091 2092int pagecache_write_end(struct file *file, struct address_space *mapping, 2093 loff_t pos, unsigned len, unsigned copied, 2094 struct page *page, void *fsdata) 2095{ 2096 const struct address_space_operations *aops = mapping->a_ops; 2097 2098 mark_page_accessed(page); 2099 return aops->write_end(file, mapping, pos, len, copied, page, fsdata); 2100} 2101EXPORT_SYMBOL(pagecache_write_end); 2102 2103ssize_t 2104generic_file_direct_write(struct kiocb *iocb, const struct iovec *iov, 2105 unsigned long *nr_segs, loff_t pos, loff_t *ppos, 2106 size_t count, size_t ocount) 2107{ 2108 struct file *file = iocb->ki_filp; 2109 struct address_space *mapping = file->f_mapping; 2110 struct inode *inode = mapping->host; 2111 ssize_t written; 2112 size_t write_len; 2113 pgoff_t end; 2114 2115 if (count != ocount) 2116 *nr_segs = iov_shorten((struct iovec *)iov, *nr_segs, count); 2117 2118 write_len = iov_length(iov, *nr_segs); 2119 end = (pos + write_len - 1) >> PAGE_CACHE_SHIFT; 2120 2121 written = filemap_write_and_wait_range(mapping, pos, pos + write_len - 1); 2122 if (written) 2123 goto out; 2124 2125 /* 2126 * After a write we want buffered reads to be sure to go to disk to get 2127 * the new data. We invalidate clean cached page from the region we're 2128 * about to write. We do this *before* the write so that we can return 2129 * without clobbering -EIOCBQUEUED from ->direct_IO(). 2130 */ 2131 if (mapping->nrpages) { 2132 written = invalidate_inode_pages2_range(mapping, 2133 pos >> PAGE_CACHE_SHIFT, end); 2134 /* 2135 * If a page can not be invalidated, return 0 to fall back 2136 * to buffered write. 2137 */ 2138 if (written) { 2139 if (written == -EBUSY) 2140 return 0; 2141 goto out; 2142 } 2143 } 2144 2145 written = mapping->a_ops->direct_IO(WRITE, iocb, iov, pos, *nr_segs); 2146 2147 /* 2148 * Finally, try again to invalidate clean pages which might have been 2149 * cached by non-direct readahead, or faulted in by get_user_pages() 2150 * if the source of the write was an mmap'ed region of the file 2151 * we're writing. Either one is a pretty crazy thing to do, 2152 * so we don't support it 100%. If this invalidation 2153 * fails, tough, the write still worked... 2154 */ 2155 if (mapping->nrpages) { 2156 invalidate_inode_pages2_range(mapping, 2157 pos >> PAGE_CACHE_SHIFT, end); 2158 } 2159 2160 if (written > 0) { 2161 loff_t end = pos + written; 2162 if (end > i_size_read(inode) && !S_ISBLK(inode->i_mode)) { 2163 i_size_write(inode, end); 2164 mark_inode_dirty(inode); 2165 } 2166 *ppos = end; 2167 } 2168 2169 /* 2170 * Sync the fs metadata but not the minor inode changes and 2171 * of course not the data as we did direct DMA for the IO. 2172 * i_mutex is held, which protects generic_osync_inode() from 2173 * livelocking. AIO O_DIRECT ops attempt to sync metadata here. 2174 */ 2175out: 2176 if ((written >= 0 || written == -EIOCBQUEUED) && 2177 ((file->f_flags & O_SYNC) || IS_SYNC(inode))) { 2178 int err = generic_osync_inode(inode, mapping, OSYNC_METADATA); 2179 if (err < 0) 2180 written = err; 2181 } 2182 return written; 2183} 2184EXPORT_SYMBOL(generic_file_direct_write); 2185 2186/* 2187 * Find or create a page at the given pagecache position. Return the locked 2188 * page. This function is specifically for buffered writes. 2189 */ 2190struct page *grab_cache_page_write_begin(struct address_space *mapping, 2191 pgoff_t index, unsigned flags) 2192{ 2193 int status; 2194 struct page *page; 2195 gfp_t gfp_notmask = 0; 2196 if (flags & AOP_FLAG_NOFS) 2197 gfp_notmask = __GFP_FS; 2198repeat: 2199 page = find_lock_page(mapping, index); 2200 if (likely(page)) 2201 return page; 2202 2203 page = __page_cache_alloc(mapping_gfp_mask(mapping) & ~gfp_notmask); 2204 if (!page) 2205 return NULL; 2206 status = add_to_page_cache_lru(page, mapping, index, 2207 GFP_KERNEL & ~gfp_notmask); 2208 if (unlikely(status)) { 2209 page_cache_release(page); 2210 if (status == -EEXIST) 2211 goto repeat; 2212 return NULL; 2213 } 2214 return page; 2215} 2216EXPORT_SYMBOL(grab_cache_page_write_begin); 2217 2218static ssize_t generic_perform_write(struct file *file, 2219 struct iov_iter *i, loff_t pos) 2220{ 2221 struct address_space *mapping = file->f_mapping; 2222 const struct address_space_operations *a_ops = mapping->a_ops; 2223 long status = 0; 2224 ssize_t written = 0; 2225 unsigned int flags = 0; 2226 2227 /* 2228 * Copies from kernel address space cannot fail (NFSD is a big user). 2229 */ 2230 if (segment_eq(get_fs(), KERNEL_DS)) 2231 flags |= AOP_FLAG_UNINTERRUPTIBLE; 2232 2233 do { 2234 struct page *page; 2235 pgoff_t index; /* Pagecache index for current page */ 2236 unsigned long offset; /* Offset into pagecache page */ 2237 unsigned long bytes; /* Bytes to write to page */ 2238 size_t copied; /* Bytes copied from user */ 2239 void *fsdata; 2240 2241 offset = (pos & (PAGE_CACHE_SIZE - 1)); 2242 index = pos >> PAGE_CACHE_SHIFT; 2243 bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset, 2244 iov_iter_count(i)); 2245 2246again: 2247 2248 /* 2249 * Bring in the user page that we will copy from _first_. 2250 * Otherwise there's a nasty deadlock on copying from the 2251 * same page as we're writing to, without it being marked 2252 * up-to-date. 2253 * 2254 * Not only is this an optimisation, but it is also required 2255 * to check that the address is actually valid, when atomic 2256 * usercopies are used, below. 2257 */ 2258 if (unlikely(iov_iter_fault_in_readable(i, bytes))) { 2259 status = -EFAULT; 2260 break; 2261 } 2262 2263 status = a_ops->write_begin(file, mapping, pos, bytes, flags, 2264 &page, &fsdata); 2265 if (unlikely(status)) 2266 break; 2267 2268 pagefault_disable(); 2269 copied = iov_iter_copy_from_user_atomic(page, i, offset, bytes); 2270 pagefault_enable(); 2271 flush_dcache_page(page); 2272 2273 status = a_ops->write_end(file, mapping, pos, bytes, copied, 2274 page, fsdata); 2275 if (unlikely(status < 0)) 2276 break; 2277 copied = status; 2278 2279 cond_resched(); 2280 2281 iov_iter_advance(i, copied); 2282 if (unlikely(copied == 0)) { 2283 /* 2284 * If we were unable to copy any data at all, we must 2285 * fall back to a single segment length write. 2286 * 2287 * If we didn't fallback here, we could livelock 2288 * because not all segments in the iov can be copied at 2289 * once without a pagefault. 2290 */ 2291 bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset, 2292 iov_iter_single_seg_count(i)); 2293 goto again; 2294 } 2295 pos += copied; 2296 written += copied; 2297 2298 balance_dirty_pages_ratelimited(mapping); 2299 2300 } while (iov_iter_count(i)); 2301 2302 return written ? written : status; 2303} 2304 2305ssize_t 2306generic_file_buffered_write(struct kiocb *iocb, const struct iovec *iov, 2307 unsigned long nr_segs, loff_t pos, loff_t *ppos, 2308 size_t count, ssize_t written) 2309{ 2310 struct file *file = iocb->ki_filp; 2311 struct address_space *mapping = file->f_mapping; 2312 const struct address_space_operations *a_ops = mapping->a_ops; 2313 struct inode *inode = mapping->host; 2314 ssize_t status; 2315 struct iov_iter i; 2316 2317 iov_iter_init(&i, iov, nr_segs, count, written); 2318 status = generic_perform_write(file, &i, pos); 2319 2320 if (likely(status >= 0)) { 2321 written += status; 2322 *ppos = pos + status; 2323 2324 /* 2325 * For now, when the user asks for O_SYNC, we'll actually give 2326 * O_DSYNC 2327 */ 2328 if (unlikely((file->f_flags & O_SYNC) || IS_SYNC(inode))) { 2329 if (!a_ops->writepage || !is_sync_kiocb(iocb)) 2330 status = generic_osync_inode(inode, mapping, 2331 OSYNC_METADATA|OSYNC_DATA); 2332 } 2333 } 2334 2335 /* 2336 * If we get here for O_DIRECT writes then we must have fallen through 2337 * to buffered writes (block instantiation inside i_size). So we sync 2338 * the file data here, to try to honour O_DIRECT expectations. 2339 */ 2340 if (unlikely(file->f_flags & O_DIRECT) && written) 2341 status = filemap_write_and_wait_range(mapping, 2342 pos, pos + written - 1); 2343 2344 return written ? written : status; 2345} 2346EXPORT_SYMBOL(generic_file_buffered_write); 2347 2348static ssize_t 2349__generic_file_aio_write_nolock(struct kiocb *iocb, const struct iovec *iov, 2350 unsigned long nr_segs, loff_t *ppos) 2351{ 2352 struct file *file = iocb->ki_filp; 2353 struct address_space * mapping = file->f_mapping; 2354 size_t ocount; /* original count */ 2355 size_t count; /* after file limit checks */ 2356 struct inode *inode = mapping->host; 2357 loff_t pos; 2358 ssize_t written; 2359 ssize_t err; 2360 2361 ocount = 0; 2362 err = generic_segment_checks(iov, &nr_segs, &ocount, VERIFY_READ); 2363 if (err) 2364 return err; 2365 2366 count = ocount; 2367 pos = *ppos; 2368 2369 vfs_check_frozen(inode->i_sb, SB_FREEZE_WRITE); 2370 2371 /* We can write back this queue in page reclaim */ 2372 current->backing_dev_info = mapping->backing_dev_info; 2373 written = 0; 2374 2375 err = generic_write_checks(file, &pos, &count, S_ISBLK(inode->i_mode)); 2376 if (err) 2377 goto out; 2378 2379 if (count == 0) 2380 goto out; 2381 2382 err = file_remove_suid(file); 2383 if (err) 2384 goto out; 2385 2386 file_update_time(file); 2387 2388 /* coalesce the iovecs and go direct-to-BIO for O_DIRECT */ 2389 if (unlikely(file->f_flags & O_DIRECT)) { 2390 loff_t endbyte; 2391 ssize_t written_buffered; 2392 2393 written = generic_file_direct_write(iocb, iov, &nr_segs, pos, 2394 ppos, count, ocount); 2395 if (written < 0 || written == count) 2396 goto out; 2397 /* 2398 * direct-io write to a hole: fall through to buffered I/O 2399 * for completing the rest of the request. 2400 */ 2401 pos += written; 2402 count -= written; 2403 written_buffered = generic_file_buffered_write(iocb, iov, 2404 nr_segs, pos, ppos, count, 2405 written); 2406 /* 2407 * If generic_file_buffered_write() retuned a synchronous error 2408 * then we want to return the number of bytes which were 2409 * direct-written, or the error code if that was zero. Note 2410 * that this differs from normal direct-io semantics, which 2411 * will return -EFOO even if some bytes were written. 2412 */ 2413 if (written_buffered < 0) { 2414 err = written_buffered; 2415 goto out; 2416 } 2417 2418 /* 2419 * We need to ensure that the page cache pages are written to 2420 * disk and invalidated to preserve the expected O_DIRECT 2421 * semantics. 2422 */ 2423 endbyte = pos + written_buffered - written - 1; 2424 err = do_sync_mapping_range(file->f_mapping, pos, endbyte, 2425 SYNC_FILE_RANGE_WAIT_BEFORE| 2426 SYNC_FILE_RANGE_WRITE| 2427 SYNC_FILE_RANGE_WAIT_AFTER); 2428 if (err == 0) { 2429 written = written_buffered; 2430 invalidate_mapping_pages(mapping, 2431 pos >> PAGE_CACHE_SHIFT, 2432 endbyte >> PAGE_CACHE_SHIFT); 2433 } else { 2434 /* 2435 * We don't know how much we wrote, so just return 2436 * the number of bytes which were direct-written 2437 */ 2438 } 2439 } else { 2440 written = generic_file_buffered_write(iocb, iov, nr_segs, 2441 pos, ppos, count, written); 2442 } 2443out: 2444 current->backing_dev_info = NULL; 2445 return written ? written : err; 2446} 2447 2448ssize_t generic_file_aio_write_nolock(struct kiocb *iocb, 2449 const struct iovec *iov, unsigned long nr_segs, loff_t pos) 2450{ 2451 struct file *file = iocb->ki_filp; 2452 struct address_space *mapping = file->f_mapping; 2453 struct inode *inode = mapping->host; 2454 ssize_t ret; 2455 2456 BUG_ON(iocb->ki_pos != pos); 2457 2458 ret = __generic_file_aio_write_nolock(iocb, iov, nr_segs, 2459 &iocb->ki_pos); 2460 2461 if (ret > 0 && ((file->f_flags & O_SYNC) || IS_SYNC(inode))) { 2462 ssize_t err; 2463 2464 err = sync_page_range_nolock(inode, mapping, pos, ret); 2465 if (err < 0) 2466 ret = err; 2467 } 2468 return ret; 2469} 2470EXPORT_SYMBOL(generic_file_aio_write_nolock); 2471 2472ssize_t generic_file_aio_write(struct kiocb *iocb, const struct iovec *iov, 2473 unsigned long nr_segs, loff_t pos) 2474{ 2475 struct file *file = iocb->ki_filp; 2476 struct address_space *mapping = file->f_mapping; 2477 struct inode *inode = mapping->host; 2478 ssize_t ret; 2479 2480 BUG_ON(iocb->ki_pos != pos); 2481 2482 mutex_lock(&inode->i_mutex); 2483 ret = __generic_file_aio_write_nolock(iocb, iov, nr_segs, 2484 &iocb->ki_pos); 2485 mutex_unlock(&inode->i_mutex); 2486 2487 if (ret > 0 && ((file->f_flags & O_SYNC) || IS_SYNC(inode))) { 2488 ssize_t err; 2489 2490 err = sync_page_range(inode, mapping, pos, ret); 2491 if (err < 0) 2492 ret = err; 2493 } 2494 return ret; 2495} 2496EXPORT_SYMBOL(generic_file_aio_write); 2497 2498/** 2499 * try_to_release_page() - release old fs-specific metadata on a page 2500 * 2501 * @page: the page which the kernel is trying to free 2502 * @gfp_mask: memory allocation flags (and I/O mode) 2503 * 2504 * The address_space is to try to release any data against the page 2505 * (presumably at page->private). If the release was successful, return `1'. 2506 * Otherwise return zero. 2507 * 2508 * This may also be called if PG_fscache is set on a page, indicating that the 2509 * page is known to the local caching routines. 2510 * 2511 * The @gfp_mask argument specifies whether I/O may be performed to release 2512 * this page (__GFP_IO), and whether the call may block (__GFP_WAIT & __GFP_FS). 2513 * 2514 */ 2515int try_to_release_page(struct page *page, gfp_t gfp_mask) 2516{ 2517 struct address_space * const mapping = page->mapping; 2518 2519 BUG_ON(!PageLocked(page)); 2520 if (PageWriteback(page)) 2521 return 0; 2522 2523 if (mapping && mapping->a_ops->releasepage) 2524 return mapping->a_ops->releasepage(page, gfp_mask); 2525 return try_to_free_buffers(page); 2526} 2527 2528EXPORT_SYMBOL(try_to_release_page); 2529