filemap.c revision 2ed7c03ec17779afb4fcfa3b8c61df61bd4879ba
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 mem_cgroup_uncharge_cache_page(page); 125 126 /* 127 * Some filesystems seem to re-dirty the page even after 128 * the VM has canceled the dirty bit (eg ext3 journaling). 129 * 130 * Fix it up by doing a final dirty accounting check after 131 * having removed the page entirely. 132 */ 133 if (PageDirty(page) && mapping_cap_account_dirty(mapping)) { 134 dec_zone_page_state(page, NR_FILE_DIRTY); 135 dec_bdi_stat(mapping->backing_dev_info, BDI_RECLAIMABLE); 136 } 137} 138 139void remove_from_page_cache(struct page *page) 140{ 141 struct address_space *mapping = page->mapping; 142 143 BUG_ON(!PageLocked(page)); 144 145 spin_lock_irq(&mapping->tree_lock); 146 __remove_from_page_cache(page); 147 spin_unlock_irq(&mapping->tree_lock); 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} 444 445/** 446 * add_to_page_cache_locked - add a locked page to the pagecache 447 * @page: page to add 448 * @mapping: the page's address_space 449 * @offset: page index 450 * @gfp_mask: page allocation mode 451 * 452 * This function is used to add a page to the pagecache. It must be locked. 453 * This function does not add the page to the LRU. The caller must do that. 454 */ 455int add_to_page_cache_locked(struct page *page, struct address_space *mapping, 456 pgoff_t offset, gfp_t gfp_mask) 457{ 458 int error; 459 460 VM_BUG_ON(!PageLocked(page)); 461 462 error = mem_cgroup_cache_charge(page, current->mm, 463 gfp_mask & GFP_RECLAIM_MASK); 464 if (error) 465 goto out; 466 467 error = radix_tree_preload(gfp_mask & ~__GFP_HIGHMEM); 468 if (error == 0) { 469 page_cache_get(page); 470 page->mapping = mapping; 471 page->index = offset; 472 473 spin_lock_irq(&mapping->tree_lock); 474 error = radix_tree_insert(&mapping->page_tree, offset, page); 475 if (likely(!error)) { 476 mapping->nrpages++; 477 __inc_zone_page_state(page, NR_FILE_PAGES); 478 } else { 479 page->mapping = NULL; 480 mem_cgroup_uncharge_cache_page(page); 481 page_cache_release(page); 482 } 483 484 spin_unlock_irq(&mapping->tree_lock); 485 radix_tree_preload_end(); 486 } else 487 mem_cgroup_uncharge_cache_page(page); 488out: 489 return error; 490} 491EXPORT_SYMBOL(add_to_page_cache_locked); 492 493int add_to_page_cache_lru(struct page *page, struct address_space *mapping, 494 pgoff_t offset, gfp_t gfp_mask) 495{ 496 int ret; 497 498 /* 499 * Splice_read and readahead add shmem/tmpfs pages into the page cache 500 * before shmem_readpage has a chance to mark them as SwapBacked: they 501 * need to go on the active_anon lru below, and mem_cgroup_cache_charge 502 * (called in add_to_page_cache) needs to know where they're going too. 503 */ 504 if (mapping_cap_swap_backed(mapping)) 505 SetPageSwapBacked(page); 506 507 ret = add_to_page_cache(page, mapping, offset, gfp_mask); 508 if (ret == 0) { 509 if (page_is_file_cache(page)) 510 lru_cache_add_file(page); 511 else 512 lru_cache_add_active_anon(page); 513 } 514 return ret; 515} 516 517#ifdef CONFIG_NUMA 518struct page *__page_cache_alloc(gfp_t gfp) 519{ 520 if (cpuset_do_page_mem_spread()) { 521 int n = cpuset_mem_spread_node(); 522 return alloc_pages_node(n, gfp, 0); 523 } 524 return alloc_pages(gfp, 0); 525} 526EXPORT_SYMBOL(__page_cache_alloc); 527#endif 528 529static int __sleep_on_page_lock(void *word) 530{ 531 io_schedule(); 532 return 0; 533} 534 535/* 536 * In order to wait for pages to become available there must be 537 * waitqueues associated with pages. By using a hash table of 538 * waitqueues where the bucket discipline is to maintain all 539 * waiters on the same queue and wake all when any of the pages 540 * become available, and for the woken contexts to check to be 541 * sure the appropriate page became available, this saves space 542 * at a cost of "thundering herd" phenomena during rare hash 543 * collisions. 544 */ 545static wait_queue_head_t *page_waitqueue(struct page *page) 546{ 547 const struct zone *zone = page_zone(page); 548 549 return &zone->wait_table[hash_ptr(page, zone->wait_table_bits)]; 550} 551 552static inline void wake_up_page(struct page *page, int bit) 553{ 554 __wake_up_bit(page_waitqueue(page), &page->flags, bit); 555} 556 557void wait_on_page_bit(struct page *page, int bit_nr) 558{ 559 DEFINE_WAIT_BIT(wait, &page->flags, bit_nr); 560 561 if (test_bit(bit_nr, &page->flags)) 562 __wait_on_bit(page_waitqueue(page), &wait, sync_page, 563 TASK_UNINTERRUPTIBLE); 564} 565EXPORT_SYMBOL(wait_on_page_bit); 566 567/** 568 * unlock_page - unlock a locked page 569 * @page: the page 570 * 571 * Unlocks the page and wakes up sleepers in ___wait_on_page_locked(). 572 * Also wakes sleepers in wait_on_page_writeback() because the wakeup 573 * mechananism between PageLocked pages and PageWriteback pages is shared. 574 * But that's OK - sleepers in wait_on_page_writeback() just go back to sleep. 575 * 576 * The mb is necessary to enforce ordering between the clear_bit and the read 577 * of the waitqueue (to avoid SMP races with a parallel wait_on_page_locked()). 578 */ 579void unlock_page(struct page *page) 580{ 581 VM_BUG_ON(!PageLocked(page)); 582 clear_bit_unlock(PG_locked, &page->flags); 583 smp_mb__after_clear_bit(); 584 wake_up_page(page, PG_locked); 585} 586EXPORT_SYMBOL(unlock_page); 587 588/** 589 * end_page_writeback - end writeback against a page 590 * @page: the page 591 */ 592void end_page_writeback(struct page *page) 593{ 594 if (TestClearPageReclaim(page)) 595 rotate_reclaimable_page(page); 596 597 if (!test_clear_page_writeback(page)) 598 BUG(); 599 600 smp_mb__after_clear_bit(); 601 wake_up_page(page, PG_writeback); 602} 603EXPORT_SYMBOL(end_page_writeback); 604 605/** 606 * __lock_page - get a lock on the page, assuming we need to sleep to get it 607 * @page: the page to lock 608 * 609 * Ugly. Running sync_page() in state TASK_UNINTERRUPTIBLE is scary. If some 610 * random driver's requestfn sets TASK_RUNNING, we could busywait. However 611 * chances are that on the second loop, the block layer's plug list is empty, 612 * so sync_page() will then return in state TASK_UNINTERRUPTIBLE. 613 */ 614void __lock_page(struct page *page) 615{ 616 DEFINE_WAIT_BIT(wait, &page->flags, PG_locked); 617 618 __wait_on_bit_lock(page_waitqueue(page), &wait, sync_page, 619 TASK_UNINTERRUPTIBLE); 620} 621EXPORT_SYMBOL(__lock_page); 622 623int __lock_page_killable(struct page *page) 624{ 625 DEFINE_WAIT_BIT(wait, &page->flags, PG_locked); 626 627 return __wait_on_bit_lock(page_waitqueue(page), &wait, 628 sync_page_killable, TASK_KILLABLE); 629} 630 631/** 632 * __lock_page_nosync - get a lock on the page, without calling sync_page() 633 * @page: the page to lock 634 * 635 * Variant of lock_page that does not require the caller to hold a reference 636 * on the page's mapping. 637 */ 638void __lock_page_nosync(struct page *page) 639{ 640 DEFINE_WAIT_BIT(wait, &page->flags, PG_locked); 641 __wait_on_bit_lock(page_waitqueue(page), &wait, __sleep_on_page_lock, 642 TASK_UNINTERRUPTIBLE); 643} 644 645/** 646 * find_get_page - find and get a page reference 647 * @mapping: the address_space to search 648 * @offset: the page index 649 * 650 * Is there a pagecache struct page at the given (mapping, offset) tuple? 651 * If yes, increment its refcount and return it; if no, return NULL. 652 */ 653struct page *find_get_page(struct address_space *mapping, pgoff_t offset) 654{ 655 void **pagep; 656 struct page *page; 657 658 rcu_read_lock(); 659repeat: 660 page = NULL; 661 pagep = radix_tree_lookup_slot(&mapping->page_tree, offset); 662 if (pagep) { 663 page = radix_tree_deref_slot(pagep); 664 if (unlikely(!page || page == RADIX_TREE_RETRY)) 665 goto repeat; 666 667 if (!page_cache_get_speculative(page)) 668 goto repeat; 669 670 /* 671 * Has the page moved? 672 * This is part of the lockless pagecache protocol. See 673 * include/linux/pagemap.h for details. 674 */ 675 if (unlikely(page != *pagep)) { 676 page_cache_release(page); 677 goto repeat; 678 } 679 } 680 rcu_read_unlock(); 681 682 return page; 683} 684EXPORT_SYMBOL(find_get_page); 685 686/** 687 * find_lock_page - locate, pin and lock a pagecache page 688 * @mapping: the address_space to search 689 * @offset: the page index 690 * 691 * Locates the desired pagecache page, locks it, increments its reference 692 * count and returns its address. 693 * 694 * Returns zero if the page was not present. find_lock_page() may sleep. 695 */ 696struct page *find_lock_page(struct address_space *mapping, pgoff_t offset) 697{ 698 struct page *page; 699 700repeat: 701 page = find_get_page(mapping, offset); 702 if (page) { 703 lock_page(page); 704 /* Has the page been truncated? */ 705 if (unlikely(page->mapping != mapping)) { 706 unlock_page(page); 707 page_cache_release(page); 708 goto repeat; 709 } 710 VM_BUG_ON(page->index != offset); 711 } 712 return page; 713} 714EXPORT_SYMBOL(find_lock_page); 715 716/** 717 * find_or_create_page - locate or add a pagecache page 718 * @mapping: the page's address_space 719 * @index: the page's index into the mapping 720 * @gfp_mask: page allocation mode 721 * 722 * Locates a page in the pagecache. If the page is not present, a new page 723 * is allocated using @gfp_mask and is added to the pagecache and to the VM's 724 * LRU list. The returned page is locked and has its reference count 725 * incremented. 726 * 727 * find_or_create_page() may sleep, even if @gfp_flags specifies an atomic 728 * allocation! 729 * 730 * find_or_create_page() returns the desired page's address, or zero on 731 * memory exhaustion. 732 */ 733struct page *find_or_create_page(struct address_space *mapping, 734 pgoff_t index, gfp_t gfp_mask) 735{ 736 struct page *page; 737 int err; 738repeat: 739 page = find_lock_page(mapping, index); 740 if (!page) { 741 page = __page_cache_alloc(gfp_mask); 742 if (!page) 743 return NULL; 744 /* 745 * We want a regular kernel memory (not highmem or DMA etc) 746 * allocation for the radix tree nodes, but we need to honour 747 * the context-specific requirements the caller has asked for. 748 * GFP_RECLAIM_MASK collects those requirements. 749 */ 750 err = add_to_page_cache_lru(page, mapping, index, 751 (gfp_mask & GFP_RECLAIM_MASK)); 752 if (unlikely(err)) { 753 page_cache_release(page); 754 page = NULL; 755 if (err == -EEXIST) 756 goto repeat; 757 } 758 } 759 return page; 760} 761EXPORT_SYMBOL(find_or_create_page); 762 763/** 764 * find_get_pages - gang pagecache lookup 765 * @mapping: The address_space to search 766 * @start: The starting page index 767 * @nr_pages: The maximum number of pages 768 * @pages: Where the resulting pages are placed 769 * 770 * find_get_pages() will search for and return a group of up to 771 * @nr_pages pages in the mapping. The pages are placed at @pages. 772 * find_get_pages() takes a reference against the returned pages. 773 * 774 * The search returns a group of mapping-contiguous pages with ascending 775 * indexes. There may be holes in the indices due to not-present pages. 776 * 777 * find_get_pages() returns the number of pages which were found. 778 */ 779unsigned find_get_pages(struct address_space *mapping, pgoff_t start, 780 unsigned int nr_pages, struct page **pages) 781{ 782 unsigned int i; 783 unsigned int ret; 784 unsigned int nr_found; 785 786 rcu_read_lock(); 787restart: 788 nr_found = radix_tree_gang_lookup_slot(&mapping->page_tree, 789 (void ***)pages, start, nr_pages); 790 ret = 0; 791 for (i = 0; i < nr_found; i++) { 792 struct page *page; 793repeat: 794 page = radix_tree_deref_slot((void **)pages[i]); 795 if (unlikely(!page)) 796 continue; 797 /* 798 * this can only trigger if nr_found == 1, making livelock 799 * a non issue. 800 */ 801 if (unlikely(page == RADIX_TREE_RETRY)) 802 goto restart; 803 804 if (!page_cache_get_speculative(page)) 805 goto repeat; 806 807 /* Has the page moved? */ 808 if (unlikely(page != *((void **)pages[i]))) { 809 page_cache_release(page); 810 goto repeat; 811 } 812 813 pages[ret] = page; 814 ret++; 815 } 816 rcu_read_unlock(); 817 return ret; 818} 819 820/** 821 * find_get_pages_contig - gang contiguous pagecache lookup 822 * @mapping: The address_space to search 823 * @index: The starting page index 824 * @nr_pages: The maximum number of pages 825 * @pages: Where the resulting pages are placed 826 * 827 * find_get_pages_contig() works exactly like find_get_pages(), except 828 * that the returned number of pages are guaranteed to be contiguous. 829 * 830 * find_get_pages_contig() returns the number of pages which were found. 831 */ 832unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t index, 833 unsigned int nr_pages, struct page **pages) 834{ 835 unsigned int i; 836 unsigned int ret; 837 unsigned int nr_found; 838 839 rcu_read_lock(); 840restart: 841 nr_found = radix_tree_gang_lookup_slot(&mapping->page_tree, 842 (void ***)pages, index, nr_pages); 843 ret = 0; 844 for (i = 0; i < nr_found; i++) { 845 struct page *page; 846repeat: 847 page = radix_tree_deref_slot((void **)pages[i]); 848 if (unlikely(!page)) 849 continue; 850 /* 851 * this can only trigger if nr_found == 1, making livelock 852 * a non issue. 853 */ 854 if (unlikely(page == RADIX_TREE_RETRY)) 855 goto restart; 856 857 if (page->mapping == NULL || page->index != index) 858 break; 859 860 if (!page_cache_get_speculative(page)) 861 goto repeat; 862 863 /* Has the page moved? */ 864 if (unlikely(page != *((void **)pages[i]))) { 865 page_cache_release(page); 866 goto repeat; 867 } 868 869 pages[ret] = page; 870 ret++; 871 index++; 872 } 873 rcu_read_unlock(); 874 return ret; 875} 876EXPORT_SYMBOL(find_get_pages_contig); 877 878/** 879 * find_get_pages_tag - find and return pages that match @tag 880 * @mapping: the address_space to search 881 * @index: the starting page index 882 * @tag: the tag index 883 * @nr_pages: the maximum number of pages 884 * @pages: where the resulting pages are placed 885 * 886 * Like find_get_pages, except we only return pages which are tagged with 887 * @tag. We update @index to index the next page for the traversal. 888 */ 889unsigned find_get_pages_tag(struct address_space *mapping, pgoff_t *index, 890 int tag, unsigned int nr_pages, struct page **pages) 891{ 892 unsigned int i; 893 unsigned int ret; 894 unsigned int nr_found; 895 896 rcu_read_lock(); 897restart: 898 nr_found = radix_tree_gang_lookup_tag_slot(&mapping->page_tree, 899 (void ***)pages, *index, nr_pages, tag); 900 ret = 0; 901 for (i = 0; i < nr_found; i++) { 902 struct page *page; 903repeat: 904 page = radix_tree_deref_slot((void **)pages[i]); 905 if (unlikely(!page)) 906 continue; 907 /* 908 * this can only trigger if nr_found == 1, making livelock 909 * a non issue. 910 */ 911 if (unlikely(page == RADIX_TREE_RETRY)) 912 goto restart; 913 914 if (!page_cache_get_speculative(page)) 915 goto repeat; 916 917 /* Has the page moved? */ 918 if (unlikely(page != *((void **)pages[i]))) { 919 page_cache_release(page); 920 goto repeat; 921 } 922 923 pages[ret] = page; 924 ret++; 925 } 926 rcu_read_unlock(); 927 928 if (ret) 929 *index = pages[ret - 1]->index + 1; 930 931 return ret; 932} 933EXPORT_SYMBOL(find_get_pages_tag); 934 935/** 936 * grab_cache_page_nowait - returns locked page at given index in given cache 937 * @mapping: target address_space 938 * @index: the page index 939 * 940 * Same as grab_cache_page(), but do not wait if the page is unavailable. 941 * This is intended for speculative data generators, where the data can 942 * be regenerated if the page couldn't be grabbed. This routine should 943 * be safe to call while holding the lock for another page. 944 * 945 * Clear __GFP_FS when allocating the page to avoid recursion into the fs 946 * and deadlock against the caller's locked page. 947 */ 948struct page * 949grab_cache_page_nowait(struct address_space *mapping, pgoff_t index) 950{ 951 struct page *page = find_get_page(mapping, index); 952 953 if (page) { 954 if (trylock_page(page)) 955 return page; 956 page_cache_release(page); 957 return NULL; 958 } 959 page = __page_cache_alloc(mapping_gfp_mask(mapping) & ~__GFP_FS); 960 if (page && add_to_page_cache_lru(page, mapping, index, GFP_NOFS)) { 961 page_cache_release(page); 962 page = NULL; 963 } 964 return page; 965} 966EXPORT_SYMBOL(grab_cache_page_nowait); 967 968/* 969 * CD/DVDs are error prone. When a medium error occurs, the driver may fail 970 * a _large_ part of the i/o request. Imagine the worst scenario: 971 * 972 * ---R__________________________________________B__________ 973 * ^ reading here ^ bad block(assume 4k) 974 * 975 * read(R) => miss => readahead(R...B) => media error => frustrating retries 976 * => failing the whole request => read(R) => read(R+1) => 977 * readahead(R+1...B+1) => bang => read(R+2) => read(R+3) => 978 * readahead(R+3...B+2) => bang => read(R+3) => read(R+4) => 979 * readahead(R+4...B+3) => bang => read(R+4) => read(R+5) => ...... 980 * 981 * It is going insane. Fix it by quickly scaling down the readahead size. 982 */ 983static void shrink_readahead_size_eio(struct file *filp, 984 struct file_ra_state *ra) 985{ 986 if (!ra->ra_pages) 987 return; 988 989 ra->ra_pages /= 4; 990} 991 992/** 993 * do_generic_file_read - generic file read routine 994 * @filp: the file to read 995 * @ppos: current file position 996 * @desc: read_descriptor 997 * @actor: read method 998 * 999 * This is a generic file read routine, and uses the 1000 * mapping->a_ops->readpage() function for the actual low-level stuff. 1001 * 1002 * This is really ugly. But the goto's actually try to clarify some 1003 * of the logic when it comes to error handling etc. 1004 */ 1005static void do_generic_file_read(struct file *filp, loff_t *ppos, 1006 read_descriptor_t *desc, read_actor_t actor) 1007{ 1008 struct address_space *mapping = filp->f_mapping; 1009 struct inode *inode = mapping->host; 1010 struct file_ra_state *ra = &filp->f_ra; 1011 pgoff_t index; 1012 pgoff_t last_index; 1013 pgoff_t prev_index; 1014 unsigned long offset; /* offset into pagecache page */ 1015 unsigned int prev_offset; 1016 int error; 1017 1018 index = *ppos >> PAGE_CACHE_SHIFT; 1019 prev_index = ra->prev_pos >> PAGE_CACHE_SHIFT; 1020 prev_offset = ra->prev_pos & (PAGE_CACHE_SIZE-1); 1021 last_index = (*ppos + desc->count + PAGE_CACHE_SIZE-1) >> PAGE_CACHE_SHIFT; 1022 offset = *ppos & ~PAGE_CACHE_MASK; 1023 1024 for (;;) { 1025 struct page *page; 1026 pgoff_t end_index; 1027 loff_t isize; 1028 unsigned long nr, ret; 1029 1030 cond_resched(); 1031find_page: 1032 page = find_get_page(mapping, index); 1033 if (!page) { 1034 page_cache_sync_readahead(mapping, 1035 ra, filp, 1036 index, last_index - index); 1037 page = find_get_page(mapping, index); 1038 if (unlikely(page == NULL)) 1039 goto no_cached_page; 1040 } 1041 if (PageReadahead(page)) { 1042 page_cache_async_readahead(mapping, 1043 ra, filp, page, 1044 index, last_index - index); 1045 } 1046 if (!PageUptodate(page)) { 1047 if (inode->i_blkbits == PAGE_CACHE_SHIFT || 1048 !mapping->a_ops->is_partially_uptodate) 1049 goto page_not_up_to_date; 1050 if (!trylock_page(page)) 1051 goto page_not_up_to_date; 1052 if (!mapping->a_ops->is_partially_uptodate(page, 1053 desc, offset)) 1054 goto page_not_up_to_date_locked; 1055 unlock_page(page); 1056 } 1057page_ok: 1058 /* 1059 * i_size must be checked after we know the page is Uptodate. 1060 * 1061 * Checking i_size after the check allows us to calculate 1062 * the correct value for "nr", which means the zero-filled 1063 * part of the page is not copied back to userspace (unless 1064 * another truncate extends the file - this is desired though). 1065 */ 1066 1067 isize = i_size_read(inode); 1068 end_index = (isize - 1) >> PAGE_CACHE_SHIFT; 1069 if (unlikely(!isize || index > end_index)) { 1070 page_cache_release(page); 1071 goto out; 1072 } 1073 1074 /* nr is the maximum number of bytes to copy from this page */ 1075 nr = PAGE_CACHE_SIZE; 1076 if (index == end_index) { 1077 nr = ((isize - 1) & ~PAGE_CACHE_MASK) + 1; 1078 if (nr <= offset) { 1079 page_cache_release(page); 1080 goto out; 1081 } 1082 } 1083 nr = nr - offset; 1084 1085 /* If users can be writing to this page using arbitrary 1086 * virtual addresses, take care about potential aliasing 1087 * before reading the page on the kernel side. 1088 */ 1089 if (mapping_writably_mapped(mapping)) 1090 flush_dcache_page(page); 1091 1092 /* 1093 * When a sequential read accesses a page several times, 1094 * only mark it as accessed the first time. 1095 */ 1096 if (prev_index != index || offset != prev_offset) 1097 mark_page_accessed(page); 1098 prev_index = index; 1099 1100 /* 1101 * Ok, we have the page, and it's up-to-date, so 1102 * now we can copy it to user space... 1103 * 1104 * The actor routine returns how many bytes were actually used.. 1105 * NOTE! This may not be the same as how much of a user buffer 1106 * we filled up (we may be padding etc), so we can only update 1107 * "pos" here (the actor routine has to update the user buffer 1108 * pointers and the remaining count). 1109 */ 1110 ret = actor(desc, page, offset, nr); 1111 offset += ret; 1112 index += offset >> PAGE_CACHE_SHIFT; 1113 offset &= ~PAGE_CACHE_MASK; 1114 prev_offset = offset; 1115 1116 page_cache_release(page); 1117 if (ret == nr && desc->count) 1118 continue; 1119 goto out; 1120 1121page_not_up_to_date: 1122 /* Get exclusive access to the page ... */ 1123 error = lock_page_killable(page); 1124 if (unlikely(error)) 1125 goto readpage_error; 1126 1127page_not_up_to_date_locked: 1128 /* Did it get truncated before we got the lock? */ 1129 if (!page->mapping) { 1130 unlock_page(page); 1131 page_cache_release(page); 1132 continue; 1133 } 1134 1135 /* Did somebody else fill it already? */ 1136 if (PageUptodate(page)) { 1137 unlock_page(page); 1138 goto page_ok; 1139 } 1140 1141readpage: 1142 /* Start the actual read. The read will unlock the page. */ 1143 error = mapping->a_ops->readpage(filp, page); 1144 1145 if (unlikely(error)) { 1146 if (error == AOP_TRUNCATED_PAGE) { 1147 page_cache_release(page); 1148 goto find_page; 1149 } 1150 goto readpage_error; 1151 } 1152 1153 if (!PageUptodate(page)) { 1154 error = lock_page_killable(page); 1155 if (unlikely(error)) 1156 goto readpage_error; 1157 if (!PageUptodate(page)) { 1158 if (page->mapping == NULL) { 1159 /* 1160 * invalidate_inode_pages got it 1161 */ 1162 unlock_page(page); 1163 page_cache_release(page); 1164 goto find_page; 1165 } 1166 unlock_page(page); 1167 shrink_readahead_size_eio(filp, ra); 1168 error = -EIO; 1169 goto readpage_error; 1170 } 1171 unlock_page(page); 1172 } 1173 1174 goto page_ok; 1175 1176readpage_error: 1177 /* UHHUH! A synchronous read error occurred. Report it */ 1178 desc->error = error; 1179 page_cache_release(page); 1180 goto out; 1181 1182no_cached_page: 1183 /* 1184 * Ok, it wasn't cached, so we need to create a new 1185 * page.. 1186 */ 1187 page = page_cache_alloc_cold(mapping); 1188 if (!page) { 1189 desc->error = -ENOMEM; 1190 goto out; 1191 } 1192 error = add_to_page_cache_lru(page, mapping, 1193 index, GFP_KERNEL); 1194 if (error) { 1195 page_cache_release(page); 1196 if (error == -EEXIST) 1197 goto find_page; 1198 desc->error = error; 1199 goto out; 1200 } 1201 goto readpage; 1202 } 1203 1204out: 1205 ra->prev_pos = prev_index; 1206 ra->prev_pos <<= PAGE_CACHE_SHIFT; 1207 ra->prev_pos |= prev_offset; 1208 1209 *ppos = ((loff_t)index << PAGE_CACHE_SHIFT) + offset; 1210 file_accessed(filp); 1211} 1212 1213int file_read_actor(read_descriptor_t *desc, struct page *page, 1214 unsigned long offset, unsigned long size) 1215{ 1216 char *kaddr; 1217 unsigned long left, count = desc->count; 1218 1219 if (size > count) 1220 size = count; 1221 1222 /* 1223 * Faults on the destination of a read are common, so do it before 1224 * taking the kmap. 1225 */ 1226 if (!fault_in_pages_writeable(desc->arg.buf, size)) { 1227 kaddr = kmap_atomic(page, KM_USER0); 1228 left = __copy_to_user_inatomic(desc->arg.buf, 1229 kaddr + offset, size); 1230 kunmap_atomic(kaddr, KM_USER0); 1231 if (left == 0) 1232 goto success; 1233 } 1234 1235 /* Do it the slow way */ 1236 kaddr = kmap(page); 1237 left = __copy_to_user(desc->arg.buf, kaddr + offset, size); 1238 kunmap(page); 1239 1240 if (left) { 1241 size -= left; 1242 desc->error = -EFAULT; 1243 } 1244success: 1245 desc->count = count - size; 1246 desc->written += size; 1247 desc->arg.buf += size; 1248 return size; 1249} 1250 1251/* 1252 * Performs necessary checks before doing a write 1253 * @iov: io vector request 1254 * @nr_segs: number of segments in the iovec 1255 * @count: number of bytes to write 1256 * @access_flags: type of access: %VERIFY_READ or %VERIFY_WRITE 1257 * 1258 * Adjust number of segments and amount of bytes to write (nr_segs should be 1259 * properly initialized first). Returns appropriate error code that caller 1260 * should return or zero in case that write should be allowed. 1261 */ 1262int generic_segment_checks(const struct iovec *iov, 1263 unsigned long *nr_segs, size_t *count, int access_flags) 1264{ 1265 unsigned long seg; 1266 size_t cnt = 0; 1267 for (seg = 0; seg < *nr_segs; seg++) { 1268 const struct iovec *iv = &iov[seg]; 1269 1270 /* 1271 * If any segment has a negative length, or the cumulative 1272 * length ever wraps negative then return -EINVAL. 1273 */ 1274 cnt += iv->iov_len; 1275 if (unlikely((ssize_t)(cnt|iv->iov_len) < 0)) 1276 return -EINVAL; 1277 if (access_ok(access_flags, iv->iov_base, iv->iov_len)) 1278 continue; 1279 if (seg == 0) 1280 return -EFAULT; 1281 *nr_segs = seg; 1282 cnt -= iv->iov_len; /* This segment is no good */ 1283 break; 1284 } 1285 *count = cnt; 1286 return 0; 1287} 1288EXPORT_SYMBOL(generic_segment_checks); 1289 1290/** 1291 * generic_file_aio_read - generic filesystem read routine 1292 * @iocb: kernel I/O control block 1293 * @iov: io vector request 1294 * @nr_segs: number of segments in the iovec 1295 * @pos: current file position 1296 * 1297 * This is the "read()" routine for all filesystems 1298 * that can use the page cache directly. 1299 */ 1300ssize_t 1301generic_file_aio_read(struct kiocb *iocb, const struct iovec *iov, 1302 unsigned long nr_segs, loff_t pos) 1303{ 1304 struct file *filp = iocb->ki_filp; 1305 ssize_t retval; 1306 unsigned long seg; 1307 size_t count; 1308 loff_t *ppos = &iocb->ki_pos; 1309 1310 count = 0; 1311 retval = generic_segment_checks(iov, &nr_segs, &count, VERIFY_WRITE); 1312 if (retval) 1313 return retval; 1314 1315 /* coalesce the iovecs and go direct-to-BIO for O_DIRECT */ 1316 if (filp->f_flags & O_DIRECT) { 1317 loff_t size; 1318 struct address_space *mapping; 1319 struct inode *inode; 1320 1321 mapping = filp->f_mapping; 1322 inode = mapping->host; 1323 if (!count) 1324 goto out; /* skip atime */ 1325 size = i_size_read(inode); 1326 if (pos < size) { 1327 retval = filemap_write_and_wait_range(mapping, pos, 1328 pos + iov_length(iov, nr_segs) - 1); 1329 if (!retval) { 1330 retval = mapping->a_ops->direct_IO(READ, iocb, 1331 iov, pos, nr_segs); 1332 } 1333 if (retval > 0) 1334 *ppos = pos + retval; 1335 if (retval) { 1336 file_accessed(filp); 1337 goto out; 1338 } 1339 } 1340 } 1341 1342 for (seg = 0; seg < nr_segs; seg++) { 1343 read_descriptor_t desc; 1344 1345 desc.written = 0; 1346 desc.arg.buf = iov[seg].iov_base; 1347 desc.count = iov[seg].iov_len; 1348 if (desc.count == 0) 1349 continue; 1350 desc.error = 0; 1351 do_generic_file_read(filp, ppos, &desc, file_read_actor); 1352 retval += desc.written; 1353 if (desc.error) { 1354 retval = retval ?: desc.error; 1355 break; 1356 } 1357 if (desc.count > 0) 1358 break; 1359 } 1360out: 1361 return retval; 1362} 1363EXPORT_SYMBOL(generic_file_aio_read); 1364 1365static ssize_t 1366do_readahead(struct address_space *mapping, struct file *filp, 1367 pgoff_t index, unsigned long nr) 1368{ 1369 if (!mapping || !mapping->a_ops || !mapping->a_ops->readpage) 1370 return -EINVAL; 1371 1372 force_page_cache_readahead(mapping, filp, index, 1373 max_sane_readahead(nr)); 1374 return 0; 1375} 1376 1377asmlinkage long sys_readahead(int fd, loff_t offset, size_t count) 1378{ 1379 ssize_t ret; 1380 struct file *file; 1381 1382 ret = -EBADF; 1383 file = fget(fd); 1384 if (file) { 1385 if (file->f_mode & FMODE_READ) { 1386 struct address_space *mapping = file->f_mapping; 1387 pgoff_t start = offset >> PAGE_CACHE_SHIFT; 1388 pgoff_t end = (offset + count - 1) >> PAGE_CACHE_SHIFT; 1389 unsigned long len = end - start + 1; 1390 ret = do_readahead(mapping, file, start, len); 1391 } 1392 fput(file); 1393 } 1394 return ret; 1395} 1396 1397#ifdef CONFIG_MMU 1398/** 1399 * page_cache_read - adds requested page to the page cache if not already there 1400 * @file: file to read 1401 * @offset: page index 1402 * 1403 * This adds the requested page to the page cache if it isn't already there, 1404 * and schedules an I/O to read in its contents from disk. 1405 */ 1406static int page_cache_read(struct file *file, pgoff_t offset) 1407{ 1408 struct address_space *mapping = file->f_mapping; 1409 struct page *page; 1410 int ret; 1411 1412 do { 1413 page = page_cache_alloc_cold(mapping); 1414 if (!page) 1415 return -ENOMEM; 1416 1417 ret = add_to_page_cache_lru(page, mapping, offset, GFP_KERNEL); 1418 if (ret == 0) 1419 ret = mapping->a_ops->readpage(file, page); 1420 else if (ret == -EEXIST) 1421 ret = 0; /* losing race to add is OK */ 1422 1423 page_cache_release(page); 1424 1425 } while (ret == AOP_TRUNCATED_PAGE); 1426 1427 return ret; 1428} 1429 1430#define MMAP_LOTSAMISS (100) 1431 1432/** 1433 * filemap_fault - read in file data for page fault handling 1434 * @vma: vma in which the fault was taken 1435 * @vmf: struct vm_fault containing details of the fault 1436 * 1437 * filemap_fault() is invoked via the vma operations vector for a 1438 * mapped memory region to read in file data during a page fault. 1439 * 1440 * The goto's are kind of ugly, but this streamlines the normal case of having 1441 * it in the page cache, and handles the special cases reasonably without 1442 * having a lot of duplicated code. 1443 */ 1444int filemap_fault(struct vm_area_struct *vma, struct vm_fault *vmf) 1445{ 1446 int error; 1447 struct file *file = vma->vm_file; 1448 struct address_space *mapping = file->f_mapping; 1449 struct file_ra_state *ra = &file->f_ra; 1450 struct inode *inode = mapping->host; 1451 struct page *page; 1452 pgoff_t size; 1453 int did_readaround = 0; 1454 int ret = 0; 1455 1456 size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT; 1457 if (vmf->pgoff >= size) 1458 return VM_FAULT_SIGBUS; 1459 1460 /* If we don't want any read-ahead, don't bother */ 1461 if (VM_RandomReadHint(vma)) 1462 goto no_cached_page; 1463 1464 /* 1465 * Do we have something in the page cache already? 1466 */ 1467retry_find: 1468 page = find_lock_page(mapping, vmf->pgoff); 1469 /* 1470 * For sequential accesses, we use the generic readahead logic. 1471 */ 1472 if (VM_SequentialReadHint(vma)) { 1473 if (!page) { 1474 page_cache_sync_readahead(mapping, ra, file, 1475 vmf->pgoff, 1); 1476 page = find_lock_page(mapping, vmf->pgoff); 1477 if (!page) 1478 goto no_cached_page; 1479 } 1480 if (PageReadahead(page)) { 1481 page_cache_async_readahead(mapping, ra, file, page, 1482 vmf->pgoff, 1); 1483 } 1484 } 1485 1486 if (!page) { 1487 unsigned long ra_pages; 1488 1489 ra->mmap_miss++; 1490 1491 /* 1492 * Do we miss much more than hit in this file? If so, 1493 * stop bothering with read-ahead. It will only hurt. 1494 */ 1495 if (ra->mmap_miss > MMAP_LOTSAMISS) 1496 goto no_cached_page; 1497 1498 /* 1499 * To keep the pgmajfault counter straight, we need to 1500 * check did_readaround, as this is an inner loop. 1501 */ 1502 if (!did_readaround) { 1503 ret = VM_FAULT_MAJOR; 1504 count_vm_event(PGMAJFAULT); 1505 } 1506 did_readaround = 1; 1507 ra_pages = max_sane_readahead(file->f_ra.ra_pages); 1508 if (ra_pages) { 1509 pgoff_t start = 0; 1510 1511 if (vmf->pgoff > ra_pages / 2) 1512 start = vmf->pgoff - ra_pages / 2; 1513 do_page_cache_readahead(mapping, file, start, ra_pages); 1514 } 1515 page = find_lock_page(mapping, vmf->pgoff); 1516 if (!page) 1517 goto no_cached_page; 1518 } 1519 1520 if (!did_readaround) 1521 ra->mmap_miss--; 1522 1523 /* 1524 * We have a locked page in the page cache, now we need to check 1525 * that it's up-to-date. If not, it is going to be due to an error. 1526 */ 1527 if (unlikely(!PageUptodate(page))) 1528 goto page_not_uptodate; 1529 1530 /* Must recheck i_size under page lock */ 1531 size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT; 1532 if (unlikely(vmf->pgoff >= size)) { 1533 unlock_page(page); 1534 page_cache_release(page); 1535 return VM_FAULT_SIGBUS; 1536 } 1537 1538 /* 1539 * Found the page and have a reference on it. 1540 */ 1541 ra->prev_pos = (loff_t)page->index << PAGE_CACHE_SHIFT; 1542 vmf->page = page; 1543 return ret | VM_FAULT_LOCKED; 1544 1545no_cached_page: 1546 /* 1547 * We're only likely to ever get here if MADV_RANDOM is in 1548 * effect. 1549 */ 1550 error = page_cache_read(file, vmf->pgoff); 1551 1552 /* 1553 * The page we want has now been added to the page cache. 1554 * In the unlikely event that someone removed it in the 1555 * meantime, we'll just come back here and read it again. 1556 */ 1557 if (error >= 0) 1558 goto retry_find; 1559 1560 /* 1561 * An error return from page_cache_read can result if the 1562 * system is low on memory, or a problem occurs while trying 1563 * to schedule I/O. 1564 */ 1565 if (error == -ENOMEM) 1566 return VM_FAULT_OOM; 1567 return VM_FAULT_SIGBUS; 1568 1569page_not_uptodate: 1570 /* IO error path */ 1571 if (!did_readaround) { 1572 ret = VM_FAULT_MAJOR; 1573 count_vm_event(PGMAJFAULT); 1574 } 1575 1576 /* 1577 * Umm, take care of errors if the page isn't up-to-date. 1578 * Try to re-read it _once_. We do this synchronously, 1579 * because there really aren't any performance issues here 1580 * and we need to check for errors. 1581 */ 1582 ClearPageError(page); 1583 error = mapping->a_ops->readpage(file, page); 1584 if (!error) { 1585 wait_on_page_locked(page); 1586 if (!PageUptodate(page)) 1587 error = -EIO; 1588 } 1589 page_cache_release(page); 1590 1591 if (!error || error == AOP_TRUNCATED_PAGE) 1592 goto retry_find; 1593 1594 /* Things didn't work out. Return zero to tell the mm layer so. */ 1595 shrink_readahead_size_eio(file, ra); 1596 return VM_FAULT_SIGBUS; 1597} 1598EXPORT_SYMBOL(filemap_fault); 1599 1600struct vm_operations_struct generic_file_vm_ops = { 1601 .fault = filemap_fault, 1602}; 1603 1604/* This is used for a general mmap of a disk file */ 1605 1606int generic_file_mmap(struct file * file, struct vm_area_struct * vma) 1607{ 1608 struct address_space *mapping = file->f_mapping; 1609 1610 if (!mapping->a_ops->readpage) 1611 return -ENOEXEC; 1612 file_accessed(file); 1613 vma->vm_ops = &generic_file_vm_ops; 1614 vma->vm_flags |= VM_CAN_NONLINEAR; 1615 return 0; 1616} 1617 1618/* 1619 * This is for filesystems which do not implement ->writepage. 1620 */ 1621int generic_file_readonly_mmap(struct file *file, struct vm_area_struct *vma) 1622{ 1623 if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_MAYWRITE)) 1624 return -EINVAL; 1625 return generic_file_mmap(file, vma); 1626} 1627#else 1628int generic_file_mmap(struct file * file, struct vm_area_struct * vma) 1629{ 1630 return -ENOSYS; 1631} 1632int generic_file_readonly_mmap(struct file * file, struct vm_area_struct * vma) 1633{ 1634 return -ENOSYS; 1635} 1636#endif /* CONFIG_MMU */ 1637 1638EXPORT_SYMBOL(generic_file_mmap); 1639EXPORT_SYMBOL(generic_file_readonly_mmap); 1640 1641static struct page *__read_cache_page(struct address_space *mapping, 1642 pgoff_t index, 1643 int (*filler)(void *,struct page*), 1644 void *data) 1645{ 1646 struct page *page; 1647 int err; 1648repeat: 1649 page = find_get_page(mapping, index); 1650 if (!page) { 1651 page = page_cache_alloc_cold(mapping); 1652 if (!page) 1653 return ERR_PTR(-ENOMEM); 1654 err = add_to_page_cache_lru(page, mapping, index, GFP_KERNEL); 1655 if (unlikely(err)) { 1656 page_cache_release(page); 1657 if (err == -EEXIST) 1658 goto repeat; 1659 /* Presumably ENOMEM for radix tree node */ 1660 return ERR_PTR(err); 1661 } 1662 err = filler(data, page); 1663 if (err < 0) { 1664 page_cache_release(page); 1665 page = ERR_PTR(err); 1666 } 1667 } 1668 return page; 1669} 1670 1671/** 1672 * read_cache_page_async - read into page cache, fill it if needed 1673 * @mapping: the page's address_space 1674 * @index: the page index 1675 * @filler: function to perform the read 1676 * @data: destination for read data 1677 * 1678 * Same as read_cache_page, but don't wait for page to become unlocked 1679 * after submitting it to the filler. 1680 * 1681 * Read into the page cache. If a page already exists, and PageUptodate() is 1682 * not set, try to fill the page but don't wait for it to become unlocked. 1683 * 1684 * If the page does not get brought uptodate, return -EIO. 1685 */ 1686struct page *read_cache_page_async(struct address_space *mapping, 1687 pgoff_t index, 1688 int (*filler)(void *,struct page*), 1689 void *data) 1690{ 1691 struct page *page; 1692 int err; 1693 1694retry: 1695 page = __read_cache_page(mapping, index, filler, data); 1696 if (IS_ERR(page)) 1697 return page; 1698 if (PageUptodate(page)) 1699 goto out; 1700 1701 lock_page(page); 1702 if (!page->mapping) { 1703 unlock_page(page); 1704 page_cache_release(page); 1705 goto retry; 1706 } 1707 if (PageUptodate(page)) { 1708 unlock_page(page); 1709 goto out; 1710 } 1711 err = filler(data, page); 1712 if (err < 0) { 1713 page_cache_release(page); 1714 return ERR_PTR(err); 1715 } 1716out: 1717 mark_page_accessed(page); 1718 return page; 1719} 1720EXPORT_SYMBOL(read_cache_page_async); 1721 1722/** 1723 * read_cache_page - read into page cache, fill it if needed 1724 * @mapping: the page's address_space 1725 * @index: the page index 1726 * @filler: function to perform the read 1727 * @data: destination for read data 1728 * 1729 * Read into the page cache. If a page already exists, and PageUptodate() is 1730 * not set, try to fill the page then wait for it to become unlocked. 1731 * 1732 * If the page does not get brought uptodate, return -EIO. 1733 */ 1734struct page *read_cache_page(struct address_space *mapping, 1735 pgoff_t index, 1736 int (*filler)(void *,struct page*), 1737 void *data) 1738{ 1739 struct page *page; 1740 1741 page = read_cache_page_async(mapping, index, filler, data); 1742 if (IS_ERR(page)) 1743 goto out; 1744 wait_on_page_locked(page); 1745 if (!PageUptodate(page)) { 1746 page_cache_release(page); 1747 page = ERR_PTR(-EIO); 1748 } 1749 out: 1750 return page; 1751} 1752EXPORT_SYMBOL(read_cache_page); 1753 1754/* 1755 * The logic we want is 1756 * 1757 * if suid or (sgid and xgrp) 1758 * remove privs 1759 */ 1760int should_remove_suid(struct dentry *dentry) 1761{ 1762 mode_t mode = dentry->d_inode->i_mode; 1763 int kill = 0; 1764 1765 /* suid always must be killed */ 1766 if (unlikely(mode & S_ISUID)) 1767 kill = ATTR_KILL_SUID; 1768 1769 /* 1770 * sgid without any exec bits is just a mandatory locking mark; leave 1771 * it alone. If some exec bits are set, it's a real sgid; kill it. 1772 */ 1773 if (unlikely((mode & S_ISGID) && (mode & S_IXGRP))) 1774 kill |= ATTR_KILL_SGID; 1775 1776 if (unlikely(kill && !capable(CAP_FSETID) && S_ISREG(mode))) 1777 return kill; 1778 1779 return 0; 1780} 1781EXPORT_SYMBOL(should_remove_suid); 1782 1783static int __remove_suid(struct dentry *dentry, int kill) 1784{ 1785 struct iattr newattrs; 1786 1787 newattrs.ia_valid = ATTR_FORCE | kill; 1788 return notify_change(dentry, &newattrs); 1789} 1790 1791int file_remove_suid(struct file *file) 1792{ 1793 struct dentry *dentry = file->f_path.dentry; 1794 int killsuid = should_remove_suid(dentry); 1795 int killpriv = security_inode_need_killpriv(dentry); 1796 int error = 0; 1797 1798 if (killpriv < 0) 1799 return killpriv; 1800 if (killpriv) 1801 error = security_inode_killpriv(dentry); 1802 if (!error && killsuid) 1803 error = __remove_suid(dentry, killsuid); 1804 1805 return error; 1806} 1807EXPORT_SYMBOL(file_remove_suid); 1808 1809static size_t __iovec_copy_from_user_inatomic(char *vaddr, 1810 const struct iovec *iov, size_t base, size_t bytes) 1811{ 1812 size_t copied = 0, left = 0; 1813 1814 while (bytes) { 1815 char __user *buf = iov->iov_base + base; 1816 int copy = min(bytes, iov->iov_len - base); 1817 1818 base = 0; 1819 left = __copy_from_user_inatomic_nocache(vaddr, buf, copy); 1820 copied += copy; 1821 bytes -= copy; 1822 vaddr += copy; 1823 iov++; 1824 1825 if (unlikely(left)) 1826 break; 1827 } 1828 return copied - left; 1829} 1830 1831/* 1832 * Copy as much as we can into the page and return the number of bytes which 1833 * were sucessfully copied. If a fault is encountered then return the number of 1834 * bytes which were copied. 1835 */ 1836size_t iov_iter_copy_from_user_atomic(struct page *page, 1837 struct iov_iter *i, unsigned long offset, size_t bytes) 1838{ 1839 char *kaddr; 1840 size_t copied; 1841 1842 BUG_ON(!in_atomic()); 1843 kaddr = kmap_atomic(page, KM_USER0); 1844 if (likely(i->nr_segs == 1)) { 1845 int left; 1846 char __user *buf = i->iov->iov_base + i->iov_offset; 1847 left = __copy_from_user_inatomic_nocache(kaddr + offset, 1848 buf, bytes); 1849 copied = bytes - left; 1850 } else { 1851 copied = __iovec_copy_from_user_inatomic(kaddr + offset, 1852 i->iov, i->iov_offset, bytes); 1853 } 1854 kunmap_atomic(kaddr, KM_USER0); 1855 1856 return copied; 1857} 1858EXPORT_SYMBOL(iov_iter_copy_from_user_atomic); 1859 1860/* 1861 * This has the same sideeffects and return value as 1862 * iov_iter_copy_from_user_atomic(). 1863 * The difference is that it attempts to resolve faults. 1864 * Page must not be locked. 1865 */ 1866size_t iov_iter_copy_from_user(struct page *page, 1867 struct iov_iter *i, unsigned long offset, size_t bytes) 1868{ 1869 char *kaddr; 1870 size_t copied; 1871 1872 kaddr = kmap(page); 1873 if (likely(i->nr_segs == 1)) { 1874 int left; 1875 char __user *buf = i->iov->iov_base + i->iov_offset; 1876 left = __copy_from_user_nocache(kaddr + offset, buf, bytes); 1877 copied = bytes - left; 1878 } else { 1879 copied = __iovec_copy_from_user_inatomic(kaddr + offset, 1880 i->iov, i->iov_offset, bytes); 1881 } 1882 kunmap(page); 1883 return copied; 1884} 1885EXPORT_SYMBOL(iov_iter_copy_from_user); 1886 1887void iov_iter_advance(struct iov_iter *i, size_t bytes) 1888{ 1889 BUG_ON(i->count < bytes); 1890 1891 if (likely(i->nr_segs == 1)) { 1892 i->iov_offset += bytes; 1893 i->count -= bytes; 1894 } else { 1895 const struct iovec *iov = i->iov; 1896 size_t base = i->iov_offset; 1897 1898 /* 1899 * The !iov->iov_len check ensures we skip over unlikely 1900 * zero-length segments (without overruning the iovec). 1901 */ 1902 while (bytes || unlikely(i->count && !iov->iov_len)) { 1903 int copy; 1904 1905 copy = min(bytes, iov->iov_len - base); 1906 BUG_ON(!i->count || i->count < copy); 1907 i->count -= copy; 1908 bytes -= copy; 1909 base += copy; 1910 if (iov->iov_len == base) { 1911 iov++; 1912 base = 0; 1913 } 1914 } 1915 i->iov = iov; 1916 i->iov_offset = base; 1917 } 1918} 1919EXPORT_SYMBOL(iov_iter_advance); 1920 1921/* 1922 * Fault in the first iovec of the given iov_iter, to a maximum length 1923 * of bytes. Returns 0 on success, or non-zero if the memory could not be 1924 * accessed (ie. because it is an invalid address). 1925 * 1926 * writev-intensive code may want this to prefault several iovecs -- that 1927 * would be possible (callers must not rely on the fact that _only_ the 1928 * first iovec will be faulted with the current implementation). 1929 */ 1930int iov_iter_fault_in_readable(struct iov_iter *i, size_t bytes) 1931{ 1932 char __user *buf = i->iov->iov_base + i->iov_offset; 1933 bytes = min(bytes, i->iov->iov_len - i->iov_offset); 1934 return fault_in_pages_readable(buf, bytes); 1935} 1936EXPORT_SYMBOL(iov_iter_fault_in_readable); 1937 1938/* 1939 * Return the count of just the current iov_iter segment. 1940 */ 1941size_t iov_iter_single_seg_count(struct iov_iter *i) 1942{ 1943 const struct iovec *iov = i->iov; 1944 if (i->nr_segs == 1) 1945 return i->count; 1946 else 1947 return min(i->count, iov->iov_len - i->iov_offset); 1948} 1949EXPORT_SYMBOL(iov_iter_single_seg_count); 1950 1951/* 1952 * Performs necessary checks before doing a write 1953 * 1954 * Can adjust writing position or amount of bytes to write. 1955 * Returns appropriate error code that caller should return or 1956 * zero in case that write should be allowed. 1957 */ 1958inline int generic_write_checks(struct file *file, loff_t *pos, size_t *count, int isblk) 1959{ 1960 struct inode *inode = file->f_mapping->host; 1961 unsigned long limit = current->signal->rlim[RLIMIT_FSIZE].rlim_cur; 1962 1963 if (unlikely(*pos < 0)) 1964 return -EINVAL; 1965 1966 if (!isblk) { 1967 /* FIXME: this is for backwards compatibility with 2.4 */ 1968 if (file->f_flags & O_APPEND) 1969 *pos = i_size_read(inode); 1970 1971 if (limit != RLIM_INFINITY) { 1972 if (*pos >= limit) { 1973 send_sig(SIGXFSZ, current, 0); 1974 return -EFBIG; 1975 } 1976 if (*count > limit - (typeof(limit))*pos) { 1977 *count = limit - (typeof(limit))*pos; 1978 } 1979 } 1980 } 1981 1982 /* 1983 * LFS rule 1984 */ 1985 if (unlikely(*pos + *count > MAX_NON_LFS && 1986 !(file->f_flags & O_LARGEFILE))) { 1987 if (*pos >= MAX_NON_LFS) { 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 return -EFBIG; 2006 } 2007 /* zero-length writes at ->s_maxbytes are OK */ 2008 } 2009 2010 if (unlikely(*pos + *count > inode->i_sb->s_maxbytes)) 2011 *count = inode->i_sb->s_maxbytes - *pos; 2012 } else { 2013#ifdef CONFIG_BLOCK 2014 loff_t isize; 2015 if (bdev_read_only(I_BDEV(inode))) 2016 return -EPERM; 2017 isize = i_size_read(inode); 2018 if (*pos >= isize) { 2019 if (*count || *pos > isize) 2020 return -ENOSPC; 2021 } 2022 2023 if (*pos + *count > isize) 2024 *count = isize - *pos; 2025#else 2026 return -EPERM; 2027#endif 2028 } 2029 return 0; 2030} 2031EXPORT_SYMBOL(generic_write_checks); 2032 2033int pagecache_write_begin(struct file *file, struct address_space *mapping, 2034 loff_t pos, unsigned len, unsigned flags, 2035 struct page **pagep, void **fsdata) 2036{ 2037 const struct address_space_operations *aops = mapping->a_ops; 2038 2039 return aops->write_begin(file, mapping, pos, len, flags, 2040 pagep, fsdata); 2041} 2042EXPORT_SYMBOL(pagecache_write_begin); 2043 2044int pagecache_write_end(struct file *file, struct address_space *mapping, 2045 loff_t pos, unsigned len, unsigned copied, 2046 struct page *page, void *fsdata) 2047{ 2048 const struct address_space_operations *aops = mapping->a_ops; 2049 2050 mark_page_accessed(page); 2051 return aops->write_end(file, mapping, pos, len, copied, page, fsdata); 2052} 2053EXPORT_SYMBOL(pagecache_write_end); 2054 2055ssize_t 2056generic_file_direct_write(struct kiocb *iocb, const struct iovec *iov, 2057 unsigned long *nr_segs, loff_t pos, loff_t *ppos, 2058 size_t count, size_t ocount) 2059{ 2060 struct file *file = iocb->ki_filp; 2061 struct address_space *mapping = file->f_mapping; 2062 struct inode *inode = mapping->host; 2063 ssize_t written; 2064 size_t write_len; 2065 pgoff_t end; 2066 2067 if (count != ocount) 2068 *nr_segs = iov_shorten((struct iovec *)iov, *nr_segs, count); 2069 2070 write_len = iov_length(iov, *nr_segs); 2071 end = (pos + write_len - 1) >> PAGE_CACHE_SHIFT; 2072 2073 written = filemap_write_and_wait_range(mapping, pos, pos + write_len - 1); 2074 if (written) 2075 goto out; 2076 2077 /* 2078 * After a write we want buffered reads to be sure to go to disk to get 2079 * the new data. We invalidate clean cached page from the region we're 2080 * about to write. We do this *before* the write so that we can return 2081 * without clobbering -EIOCBQUEUED from ->direct_IO(). 2082 */ 2083 if (mapping->nrpages) { 2084 written = invalidate_inode_pages2_range(mapping, 2085 pos >> PAGE_CACHE_SHIFT, end); 2086 /* 2087 * If a page can not be invalidated, return 0 to fall back 2088 * to buffered write. 2089 */ 2090 if (written) { 2091 if (written == -EBUSY) 2092 return 0; 2093 goto out; 2094 } 2095 } 2096 2097 written = mapping->a_ops->direct_IO(WRITE, iocb, iov, pos, *nr_segs); 2098 2099 /* 2100 * Finally, try again to invalidate clean pages which might have been 2101 * cached by non-direct readahead, or faulted in by get_user_pages() 2102 * if the source of the write was an mmap'ed region of the file 2103 * we're writing. Either one is a pretty crazy thing to do, 2104 * so we don't support it 100%. If this invalidation 2105 * fails, tough, the write still worked... 2106 */ 2107 if (mapping->nrpages) { 2108 invalidate_inode_pages2_range(mapping, 2109 pos >> PAGE_CACHE_SHIFT, end); 2110 } 2111 2112 if (written > 0) { 2113 loff_t end = pos + written; 2114 if (end > i_size_read(inode) && !S_ISBLK(inode->i_mode)) { 2115 i_size_write(inode, end); 2116 mark_inode_dirty(inode); 2117 } 2118 *ppos = end; 2119 } 2120 2121 /* 2122 * Sync the fs metadata but not the minor inode changes and 2123 * of course not the data as we did direct DMA for the IO. 2124 * i_mutex is held, which protects generic_osync_inode() from 2125 * livelocking. AIO O_DIRECT ops attempt to sync metadata here. 2126 */ 2127out: 2128 if ((written >= 0 || written == -EIOCBQUEUED) && 2129 ((file->f_flags & O_SYNC) || IS_SYNC(inode))) { 2130 int err = generic_osync_inode(inode, mapping, OSYNC_METADATA); 2131 if (err < 0) 2132 written = err; 2133 } 2134 return written; 2135} 2136EXPORT_SYMBOL(generic_file_direct_write); 2137 2138/* 2139 * Find or create a page at the given pagecache position. Return the locked 2140 * page. This function is specifically for buffered writes. 2141 */ 2142struct page *grab_cache_page_write_begin(struct address_space *mapping, 2143 pgoff_t index, unsigned flags) 2144{ 2145 int status; 2146 struct page *page; 2147 gfp_t gfp_notmask = 0; 2148 if (flags & AOP_FLAG_NOFS) 2149 gfp_notmask = __GFP_FS; 2150repeat: 2151 page = find_lock_page(mapping, index); 2152 if (likely(page)) 2153 return page; 2154 2155 page = __page_cache_alloc(mapping_gfp_mask(mapping) & ~gfp_notmask); 2156 if (!page) 2157 return NULL; 2158 status = add_to_page_cache_lru(page, mapping, index, 2159 GFP_KERNEL & ~gfp_notmask); 2160 if (unlikely(status)) { 2161 page_cache_release(page); 2162 if (status == -EEXIST) 2163 goto repeat; 2164 return NULL; 2165 } 2166 return page; 2167} 2168EXPORT_SYMBOL(grab_cache_page_write_begin); 2169 2170static ssize_t generic_perform_write(struct file *file, 2171 struct iov_iter *i, loff_t pos) 2172{ 2173 struct address_space *mapping = file->f_mapping; 2174 const struct address_space_operations *a_ops = mapping->a_ops; 2175 long status = 0; 2176 ssize_t written = 0; 2177 unsigned int flags = 0; 2178 2179 /* 2180 * Copies from kernel address space cannot fail (NFSD is a big user). 2181 */ 2182 if (segment_eq(get_fs(), KERNEL_DS)) 2183 flags |= AOP_FLAG_UNINTERRUPTIBLE; 2184 2185 do { 2186 struct page *page; 2187 pgoff_t index; /* Pagecache index for current page */ 2188 unsigned long offset; /* Offset into pagecache page */ 2189 unsigned long bytes; /* Bytes to write to page */ 2190 size_t copied; /* Bytes copied from user */ 2191 void *fsdata; 2192 2193 offset = (pos & (PAGE_CACHE_SIZE - 1)); 2194 index = pos >> PAGE_CACHE_SHIFT; 2195 bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset, 2196 iov_iter_count(i)); 2197 2198again: 2199 2200 /* 2201 * Bring in the user page that we will copy from _first_. 2202 * Otherwise there's a nasty deadlock on copying from the 2203 * same page as we're writing to, without it being marked 2204 * up-to-date. 2205 * 2206 * Not only is this an optimisation, but it is also required 2207 * to check that the address is actually valid, when atomic 2208 * usercopies are used, below. 2209 */ 2210 if (unlikely(iov_iter_fault_in_readable(i, bytes))) { 2211 status = -EFAULT; 2212 break; 2213 } 2214 2215 status = a_ops->write_begin(file, mapping, pos, bytes, flags, 2216 &page, &fsdata); 2217 if (unlikely(status)) 2218 break; 2219 2220 pagefault_disable(); 2221 copied = iov_iter_copy_from_user_atomic(page, i, offset, bytes); 2222 pagefault_enable(); 2223 flush_dcache_page(page); 2224 2225 status = a_ops->write_end(file, mapping, pos, bytes, copied, 2226 page, fsdata); 2227 if (unlikely(status < 0)) 2228 break; 2229 copied = status; 2230 2231 cond_resched(); 2232 2233 iov_iter_advance(i, copied); 2234 if (unlikely(copied == 0)) { 2235 /* 2236 * If we were unable to copy any data at all, we must 2237 * fall back to a single segment length write. 2238 * 2239 * If we didn't fallback here, we could livelock 2240 * because not all segments in the iov can be copied at 2241 * once without a pagefault. 2242 */ 2243 bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset, 2244 iov_iter_single_seg_count(i)); 2245 goto again; 2246 } 2247 pos += copied; 2248 written += copied; 2249 2250 balance_dirty_pages_ratelimited(mapping); 2251 2252 } while (iov_iter_count(i)); 2253 2254 return written ? written : status; 2255} 2256 2257ssize_t 2258generic_file_buffered_write(struct kiocb *iocb, const struct iovec *iov, 2259 unsigned long nr_segs, loff_t pos, loff_t *ppos, 2260 size_t count, ssize_t written) 2261{ 2262 struct file *file = iocb->ki_filp; 2263 struct address_space *mapping = file->f_mapping; 2264 const struct address_space_operations *a_ops = mapping->a_ops; 2265 struct inode *inode = mapping->host; 2266 ssize_t status; 2267 struct iov_iter i; 2268 2269 iov_iter_init(&i, iov, nr_segs, count, written); 2270 status = generic_perform_write(file, &i, pos); 2271 2272 if (likely(status >= 0)) { 2273 written += status; 2274 *ppos = pos + status; 2275 2276 /* 2277 * For now, when the user asks for O_SYNC, we'll actually give 2278 * O_DSYNC 2279 */ 2280 if (unlikely((file->f_flags & O_SYNC) || IS_SYNC(inode))) { 2281 if (!a_ops->writepage || !is_sync_kiocb(iocb)) 2282 status = generic_osync_inode(inode, mapping, 2283 OSYNC_METADATA|OSYNC_DATA); 2284 } 2285 } 2286 2287 /* 2288 * If we get here for O_DIRECT writes then we must have fallen through 2289 * to buffered writes (block instantiation inside i_size). So we sync 2290 * the file data here, to try to honour O_DIRECT expectations. 2291 */ 2292 if (unlikely(file->f_flags & O_DIRECT) && written) 2293 status = filemap_write_and_wait_range(mapping, 2294 pos, pos + written - 1); 2295 2296 return written ? written : status; 2297} 2298EXPORT_SYMBOL(generic_file_buffered_write); 2299 2300static ssize_t 2301__generic_file_aio_write_nolock(struct kiocb *iocb, const struct iovec *iov, 2302 unsigned long nr_segs, loff_t *ppos) 2303{ 2304 struct file *file = iocb->ki_filp; 2305 struct address_space * mapping = file->f_mapping; 2306 size_t ocount; /* original count */ 2307 size_t count; /* after file limit checks */ 2308 struct inode *inode = mapping->host; 2309 loff_t pos; 2310 ssize_t written; 2311 ssize_t err; 2312 2313 ocount = 0; 2314 err = generic_segment_checks(iov, &nr_segs, &ocount, VERIFY_READ); 2315 if (err) 2316 return err; 2317 2318 count = ocount; 2319 pos = *ppos; 2320 2321 vfs_check_frozen(inode->i_sb, SB_FREEZE_WRITE); 2322 2323 /* We can write back this queue in page reclaim */ 2324 current->backing_dev_info = mapping->backing_dev_info; 2325 written = 0; 2326 2327 err = generic_write_checks(file, &pos, &count, S_ISBLK(inode->i_mode)); 2328 if (err) 2329 goto out; 2330 2331 if (count == 0) 2332 goto out; 2333 2334 err = file_remove_suid(file); 2335 if (err) 2336 goto out; 2337 2338 file_update_time(file); 2339 2340 /* coalesce the iovecs and go direct-to-BIO for O_DIRECT */ 2341 if (unlikely(file->f_flags & O_DIRECT)) { 2342 loff_t endbyte; 2343 ssize_t written_buffered; 2344 2345 written = generic_file_direct_write(iocb, iov, &nr_segs, pos, 2346 ppos, count, ocount); 2347 if (written < 0 || written == count) 2348 goto out; 2349 /* 2350 * direct-io write to a hole: fall through to buffered I/O 2351 * for completing the rest of the request. 2352 */ 2353 pos += written; 2354 count -= written; 2355 written_buffered = generic_file_buffered_write(iocb, iov, 2356 nr_segs, pos, ppos, count, 2357 written); 2358 /* 2359 * If generic_file_buffered_write() retuned a synchronous error 2360 * then we want to return the number of bytes which were 2361 * direct-written, or the error code if that was zero. Note 2362 * that this differs from normal direct-io semantics, which 2363 * will return -EFOO even if some bytes were written. 2364 */ 2365 if (written_buffered < 0) { 2366 err = written_buffered; 2367 goto out; 2368 } 2369 2370 /* 2371 * We need to ensure that the page cache pages are written to 2372 * disk and invalidated to preserve the expected O_DIRECT 2373 * semantics. 2374 */ 2375 endbyte = pos + written_buffered - written - 1; 2376 err = do_sync_mapping_range(file->f_mapping, pos, endbyte, 2377 SYNC_FILE_RANGE_WAIT_BEFORE| 2378 SYNC_FILE_RANGE_WRITE| 2379 SYNC_FILE_RANGE_WAIT_AFTER); 2380 if (err == 0) { 2381 written = written_buffered; 2382 invalidate_mapping_pages(mapping, 2383 pos >> PAGE_CACHE_SHIFT, 2384 endbyte >> PAGE_CACHE_SHIFT); 2385 } else { 2386 /* 2387 * We don't know how much we wrote, so just return 2388 * the number of bytes which were direct-written 2389 */ 2390 } 2391 } else { 2392 written = generic_file_buffered_write(iocb, iov, nr_segs, 2393 pos, ppos, count, written); 2394 } 2395out: 2396 current->backing_dev_info = NULL; 2397 return written ? written : err; 2398} 2399 2400ssize_t generic_file_aio_write_nolock(struct kiocb *iocb, 2401 const struct iovec *iov, unsigned long nr_segs, loff_t pos) 2402{ 2403 struct file *file = iocb->ki_filp; 2404 struct address_space *mapping = file->f_mapping; 2405 struct inode *inode = mapping->host; 2406 ssize_t ret; 2407 2408 BUG_ON(iocb->ki_pos != pos); 2409 2410 ret = __generic_file_aio_write_nolock(iocb, iov, nr_segs, 2411 &iocb->ki_pos); 2412 2413 if (ret > 0 && ((file->f_flags & O_SYNC) || IS_SYNC(inode))) { 2414 ssize_t err; 2415 2416 err = sync_page_range_nolock(inode, mapping, pos, ret); 2417 if (err < 0) 2418 ret = err; 2419 } 2420 return ret; 2421} 2422EXPORT_SYMBOL(generic_file_aio_write_nolock); 2423 2424ssize_t generic_file_aio_write(struct kiocb *iocb, const struct iovec *iov, 2425 unsigned long nr_segs, loff_t pos) 2426{ 2427 struct file *file = iocb->ki_filp; 2428 struct address_space *mapping = file->f_mapping; 2429 struct inode *inode = mapping->host; 2430 ssize_t ret; 2431 2432 BUG_ON(iocb->ki_pos != pos); 2433 2434 mutex_lock(&inode->i_mutex); 2435 ret = __generic_file_aio_write_nolock(iocb, iov, nr_segs, 2436 &iocb->ki_pos); 2437 mutex_unlock(&inode->i_mutex); 2438 2439 if (ret > 0 && ((file->f_flags & O_SYNC) || IS_SYNC(inode))) { 2440 ssize_t err; 2441 2442 err = sync_page_range(inode, mapping, pos, ret); 2443 if (err < 0) 2444 ret = err; 2445 } 2446 return ret; 2447} 2448EXPORT_SYMBOL(generic_file_aio_write); 2449 2450/** 2451 * try_to_release_page() - release old fs-specific metadata on a page 2452 * 2453 * @page: the page which the kernel is trying to free 2454 * @gfp_mask: memory allocation flags (and I/O mode) 2455 * 2456 * The address_space is to try to release any data against the page 2457 * (presumably at page->private). If the release was successful, return `1'. 2458 * Otherwise return zero. 2459 * 2460 * The @gfp_mask argument specifies whether I/O may be performed to release 2461 * this page (__GFP_IO), and whether the call may block (__GFP_WAIT & __GFP_FS). 2462 * 2463 */ 2464int try_to_release_page(struct page *page, gfp_t gfp_mask) 2465{ 2466 struct address_space * const mapping = page->mapping; 2467 2468 BUG_ON(!PageLocked(page)); 2469 if (PageWriteback(page)) 2470 return 0; 2471 2472 if (mapping && mapping->a_ops->releasepage) 2473 return mapping->a_ops->releasepage(page, gfp_mask); 2474 return try_to_free_buffers(page); 2475} 2476 2477EXPORT_SYMBOL(try_to_release_page); 2478