filemap.c revision 18f2ee705d98034b0f229a3202d827468d4bffd9
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 try_to_free_buffers */ 43 44#include <asm/mman.h> 45 46/* 47 * Shared mappings implemented 30.11.1994. It's not fully working yet, 48 * though. 49 * 50 * Shared mappings now work. 15.8.1995 Bruno. 51 * 52 * finished 'unifying' the page and buffer cache and SMP-threaded the 53 * page-cache, 21.05.1999, Ingo Molnar <mingo@redhat.com> 54 * 55 * SMP-threaded pagemap-LRU 1999, Andrea Arcangeli <andrea@suse.de> 56 */ 57 58/* 59 * Lock ordering: 60 * 61 * ->i_mmap_lock (vmtruncate) 62 * ->private_lock (__free_pte->__set_page_dirty_buffers) 63 * ->swap_lock (exclusive_swap_page, others) 64 * ->mapping->tree_lock 65 * 66 * ->i_mutex 67 * ->i_mmap_lock (truncate->unmap_mapping_range) 68 * 69 * ->mmap_sem 70 * ->i_mmap_lock 71 * ->page_table_lock or pte_lock (various, mainly in memory.c) 72 * ->mapping->tree_lock (arch-dependent flush_dcache_mmap_lock) 73 * 74 * ->mmap_sem 75 * ->lock_page (access_process_vm) 76 * 77 * ->i_mutex (generic_file_buffered_write) 78 * ->mmap_sem (fault_in_pages_readable->do_page_fault) 79 * 80 * ->i_mutex 81 * ->i_alloc_sem (various) 82 * 83 * ->inode_lock 84 * ->sb_lock (fs/fs-writeback.c) 85 * ->mapping->tree_lock (__sync_single_inode) 86 * 87 * ->i_mmap_lock 88 * ->anon_vma.lock (vma_adjust) 89 * 90 * ->anon_vma.lock 91 * ->page_table_lock or pte_lock (anon_vma_prepare and various) 92 * 93 * ->page_table_lock or pte_lock 94 * ->swap_lock (try_to_unmap_one) 95 * ->private_lock (try_to_unmap_one) 96 * ->tree_lock (try_to_unmap_one) 97 * ->zone.lru_lock (follow_page->mark_page_accessed) 98 * ->zone.lru_lock (check_pte_range->isolate_lru_page) 99 * ->private_lock (page_remove_rmap->set_page_dirty) 100 * ->tree_lock (page_remove_rmap->set_page_dirty) 101 * ->inode_lock (page_remove_rmap->set_page_dirty) 102 * ->inode_lock (zap_pte_range->set_page_dirty) 103 * ->private_lock (zap_pte_range->__set_page_dirty_buffers) 104 * 105 * ->task->proc_lock 106 * ->dcache_lock (proc_pid_lookup) 107 */ 108 109/* 110 * Remove a page from the page cache and free it. Caller has to make 111 * sure the page is locked and that nobody else uses it - or that usage 112 * is safe. The caller must hold the mapping's tree_lock. 113 */ 114void __remove_from_page_cache(struct page *page) 115{ 116 struct address_space *mapping = page->mapping; 117 118 radix_tree_delete(&mapping->page_tree, page->index); 119 page->mapping = NULL; 120 mapping->nrpages--; 121 __dec_zone_page_state(page, NR_FILE_PAGES); 122 BUG_ON(page_mapped(page)); 123 124 /* 125 * Some filesystems seem to re-dirty the page even after 126 * the VM has canceled the dirty bit (eg ext3 journaling). 127 * 128 * Fix it up by doing a final dirty accounting check after 129 * having removed the page entirely. 130 */ 131 if (PageDirty(page) && mapping_cap_account_dirty(mapping)) { 132 dec_zone_page_state(page, NR_FILE_DIRTY); 133 dec_bdi_stat(mapping->backing_dev_info, BDI_RECLAIMABLE); 134 } 135} 136 137void remove_from_page_cache(struct page *page) 138{ 139 struct address_space *mapping = page->mapping; 140 141 BUG_ON(!PageLocked(page)); 142 143 spin_lock_irq(&mapping->tree_lock); 144 __remove_from_page_cache(page); 145 spin_unlock_irq(&mapping->tree_lock); 146 mem_cgroup_uncharge_cache_page(page); 147} 148 149static int sync_page(void *word) 150{ 151 struct address_space *mapping; 152 struct page *page; 153 154 page = container_of((unsigned long *)word, struct page, flags); 155 156 /* 157 * page_mapping() is being called without PG_locked held. 158 * Some knowledge of the state and use of the page is used to 159 * reduce the requirements down to a memory barrier. 160 * The danger here is of a stale page_mapping() return value 161 * indicating a struct address_space different from the one it's 162 * associated with when it is associated with one. 163 * After smp_mb(), it's either the correct page_mapping() for 164 * the page, or an old page_mapping() and the page's own 165 * page_mapping() has gone NULL. 166 * The ->sync_page() address_space operation must tolerate 167 * page_mapping() going NULL. By an amazing coincidence, 168 * this comes about because none of the users of the page 169 * in the ->sync_page() methods make essential use of the 170 * page_mapping(), merely passing the page down to the backing 171 * device's unplug functions when it's non-NULL, which in turn 172 * ignore it for all cases but swap, where only page_private(page) is 173 * of interest. When page_mapping() does go NULL, the entire 174 * call stack gracefully ignores the page and returns. 175 * -- wli 176 */ 177 smp_mb(); 178 mapping = page_mapping(page); 179 if (mapping && mapping->a_ops && mapping->a_ops->sync_page) 180 mapping->a_ops->sync_page(page); 181 io_schedule(); 182 return 0; 183} 184 185static int sync_page_killable(void *word) 186{ 187 sync_page(word); 188 return fatal_signal_pending(current) ? -EINTR : 0; 189} 190 191/** 192 * __filemap_fdatawrite_range - start writeback on mapping dirty pages in range 193 * @mapping: address space structure to write 194 * @start: offset in bytes where the range starts 195 * @end: offset in bytes where the range ends (inclusive) 196 * @sync_mode: enable synchronous operation 197 * 198 * Start writeback against all of a mapping's dirty pages that lie 199 * within the byte offsets <start, end> inclusive. 200 * 201 * If sync_mode is WB_SYNC_ALL then this is a "data integrity" operation, as 202 * opposed to a regular memory cleansing writeback. The difference between 203 * these two operations is that if a dirty page/buffer is encountered, it must 204 * be waited upon, and not just skipped over. 205 */ 206int __filemap_fdatawrite_range(struct address_space *mapping, loff_t start, 207 loff_t end, int sync_mode) 208{ 209 int ret; 210 struct writeback_control wbc = { 211 .sync_mode = sync_mode, 212 .nr_to_write = LONG_MAX, 213 .range_start = start, 214 .range_end = end, 215 }; 216 217 if (!mapping_cap_writeback_dirty(mapping)) 218 return 0; 219 220 ret = do_writepages(mapping, &wbc); 221 return ret; 222} 223 224static inline int __filemap_fdatawrite(struct address_space *mapping, 225 int sync_mode) 226{ 227 return __filemap_fdatawrite_range(mapping, 0, LLONG_MAX, sync_mode); 228} 229 230int filemap_fdatawrite(struct address_space *mapping) 231{ 232 return __filemap_fdatawrite(mapping, WB_SYNC_ALL); 233} 234EXPORT_SYMBOL(filemap_fdatawrite); 235 236int filemap_fdatawrite_range(struct address_space *mapping, loff_t start, 237 loff_t end) 238{ 239 return __filemap_fdatawrite_range(mapping, start, end, WB_SYNC_ALL); 240} 241EXPORT_SYMBOL(filemap_fdatawrite_range); 242 243/** 244 * filemap_flush - mostly a non-blocking flush 245 * @mapping: target address_space 246 * 247 * This is a mostly non-blocking flush. Not suitable for data-integrity 248 * purposes - I/O may not be started against all dirty pages. 249 */ 250int filemap_flush(struct address_space *mapping) 251{ 252 return __filemap_fdatawrite(mapping, WB_SYNC_NONE); 253} 254EXPORT_SYMBOL(filemap_flush); 255 256/** 257 * wait_on_page_writeback_range - wait for writeback to complete 258 * @mapping: target address_space 259 * @start: beginning page index 260 * @end: ending page index 261 * 262 * Wait for writeback to complete against pages indexed by start->end 263 * inclusive 264 */ 265int wait_on_page_writeback_range(struct address_space *mapping, 266 pgoff_t start, pgoff_t end) 267{ 268 struct pagevec pvec; 269 int nr_pages; 270 int ret = 0; 271 pgoff_t index; 272 273 if (end < start) 274 return 0; 275 276 pagevec_init(&pvec, 0); 277 index = start; 278 while ((index <= end) && 279 (nr_pages = pagevec_lookup_tag(&pvec, mapping, &index, 280 PAGECACHE_TAG_WRITEBACK, 281 min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1)) != 0) { 282 unsigned i; 283 284 for (i = 0; i < nr_pages; i++) { 285 struct page *page = pvec.pages[i]; 286 287 /* until radix tree lookup accepts end_index */ 288 if (page->index > end) 289 continue; 290 291 wait_on_page_writeback(page); 292 if (PageError(page)) 293 ret = -EIO; 294 } 295 pagevec_release(&pvec); 296 cond_resched(); 297 } 298 299 /* Check for outstanding write errors */ 300 if (test_and_clear_bit(AS_ENOSPC, &mapping->flags)) 301 ret = -ENOSPC; 302 if (test_and_clear_bit(AS_EIO, &mapping->flags)) 303 ret = -EIO; 304 305 return ret; 306} 307 308/** 309 * filemap_fdatawait_range - wait for all under-writeback pages to complete in a given range 310 * @mapping: address space structure to wait for 311 * @start: offset in bytes where the range starts 312 * @end: offset in bytes where the range ends (inclusive) 313 * 314 * Walk the list of under-writeback pages of the given address space 315 * in the given range and wait for all of them. 316 * 317 * This is just a simple wrapper so that callers don't have to convert offsets 318 * to page indexes themselves 319 */ 320int filemap_fdatawait_range(struct address_space *mapping, loff_t start, 321 loff_t end) 322{ 323 return wait_on_page_writeback_range(mapping, start >> PAGE_CACHE_SHIFT, 324 end >> PAGE_CACHE_SHIFT); 325} 326EXPORT_SYMBOL(filemap_fdatawait_range); 327 328/** 329 * filemap_fdatawait - wait for all under-writeback pages to complete 330 * @mapping: address space structure to wait for 331 * 332 * Walk the list of under-writeback pages of the given address space 333 * and wait for all of them. 334 */ 335int filemap_fdatawait(struct address_space *mapping) 336{ 337 loff_t i_size = i_size_read(mapping->host); 338 339 if (i_size == 0) 340 return 0; 341 342 return wait_on_page_writeback_range(mapping, 0, 343 (i_size - 1) >> PAGE_CACHE_SHIFT); 344} 345EXPORT_SYMBOL(filemap_fdatawait); 346 347int filemap_write_and_wait(struct address_space *mapping) 348{ 349 int err = 0; 350 351 if (mapping->nrpages) { 352 err = filemap_fdatawrite(mapping); 353 /* 354 * Even if the above returned error, the pages may be 355 * written partially (e.g. -ENOSPC), so we wait for it. 356 * But the -EIO is special case, it may indicate the worst 357 * thing (e.g. bug) happened, so we avoid waiting for it. 358 */ 359 if (err != -EIO) { 360 int err2 = filemap_fdatawait(mapping); 361 if (!err) 362 err = err2; 363 } 364 } 365 return err; 366} 367EXPORT_SYMBOL(filemap_write_and_wait); 368 369/** 370 * filemap_write_and_wait_range - write out & wait on a file range 371 * @mapping: the address_space for the pages 372 * @lstart: offset in bytes where the range starts 373 * @lend: offset in bytes where the range ends (inclusive) 374 * 375 * Write out and wait upon file offsets lstart->lend, inclusive. 376 * 377 * Note that `lend' is inclusive (describes the last byte to be written) so 378 * that this function can be used to write to the very end-of-file (end = -1). 379 */ 380int filemap_write_and_wait_range(struct address_space *mapping, 381 loff_t lstart, loff_t lend) 382{ 383 int err = 0; 384 385 if (mapping->nrpages) { 386 err = __filemap_fdatawrite_range(mapping, lstart, lend, 387 WB_SYNC_ALL); 388 /* See comment of filemap_write_and_wait() */ 389 if (err != -EIO) { 390 int err2 = wait_on_page_writeback_range(mapping, 391 lstart >> PAGE_CACHE_SHIFT, 392 lend >> PAGE_CACHE_SHIFT); 393 if (!err) 394 err = err2; 395 } 396 } 397 return err; 398} 399EXPORT_SYMBOL(filemap_write_and_wait_range); 400 401/** 402 * add_to_page_cache_locked - add a locked page to the pagecache 403 * @page: page to add 404 * @mapping: the page's address_space 405 * @offset: page index 406 * @gfp_mask: page allocation mode 407 * 408 * This function is used to add a page to the pagecache. It must be locked. 409 * This function does not add the page to the LRU. The caller must do that. 410 */ 411int add_to_page_cache_locked(struct page *page, struct address_space *mapping, 412 pgoff_t offset, gfp_t gfp_mask) 413{ 414 int error; 415 416 VM_BUG_ON(!PageLocked(page)); 417 418 error = mem_cgroup_cache_charge(page, current->mm, 419 gfp_mask & GFP_RECLAIM_MASK); 420 if (error) 421 goto out; 422 423 error = radix_tree_preload(gfp_mask & ~__GFP_HIGHMEM); 424 if (error == 0) { 425 page_cache_get(page); 426 page->mapping = mapping; 427 page->index = offset; 428 429 spin_lock_irq(&mapping->tree_lock); 430 error = radix_tree_insert(&mapping->page_tree, offset, page); 431 if (likely(!error)) { 432 mapping->nrpages++; 433 __inc_zone_page_state(page, NR_FILE_PAGES); 434 spin_unlock_irq(&mapping->tree_lock); 435 } else { 436 page->mapping = NULL; 437 spin_unlock_irq(&mapping->tree_lock); 438 mem_cgroup_uncharge_cache_page(page); 439 page_cache_release(page); 440 } 441 radix_tree_preload_end(); 442 } else 443 mem_cgroup_uncharge_cache_page(page); 444out: 445 return error; 446} 447EXPORT_SYMBOL(add_to_page_cache_locked); 448 449int add_to_page_cache_lru(struct page *page, struct address_space *mapping, 450 pgoff_t offset, gfp_t gfp_mask) 451{ 452 int ret; 453 454 /* 455 * Splice_read and readahead add shmem/tmpfs pages into the page cache 456 * before shmem_readpage has a chance to mark them as SwapBacked: they 457 * need to go on the active_anon lru below, and mem_cgroup_cache_charge 458 * (called in add_to_page_cache) needs to know where they're going too. 459 */ 460 if (mapping_cap_swap_backed(mapping)) 461 SetPageSwapBacked(page); 462 463 ret = add_to_page_cache(page, mapping, offset, gfp_mask); 464 if (ret == 0) { 465 if (page_is_file_cache(page)) 466 lru_cache_add_file(page); 467 else 468 lru_cache_add_active_anon(page); 469 } 470 return ret; 471} 472EXPORT_SYMBOL_GPL(add_to_page_cache_lru); 473 474#ifdef CONFIG_NUMA 475struct page *__page_cache_alloc(gfp_t gfp) 476{ 477 if (cpuset_do_page_mem_spread()) { 478 int n = cpuset_mem_spread_node(); 479 return alloc_pages_exact_node(n, gfp, 0); 480 } 481 return alloc_pages(gfp, 0); 482} 483EXPORT_SYMBOL(__page_cache_alloc); 484#endif 485 486static int __sleep_on_page_lock(void *word) 487{ 488 io_schedule(); 489 return 0; 490} 491 492/* 493 * In order to wait for pages to become available there must be 494 * waitqueues associated with pages. By using a hash table of 495 * waitqueues where the bucket discipline is to maintain all 496 * waiters on the same queue and wake all when any of the pages 497 * become available, and for the woken contexts to check to be 498 * sure the appropriate page became available, this saves space 499 * at a cost of "thundering herd" phenomena during rare hash 500 * collisions. 501 */ 502static wait_queue_head_t *page_waitqueue(struct page *page) 503{ 504 const struct zone *zone = page_zone(page); 505 506 return &zone->wait_table[hash_ptr(page, zone->wait_table_bits)]; 507} 508 509static inline void wake_up_page(struct page *page, int bit) 510{ 511 __wake_up_bit(page_waitqueue(page), &page->flags, bit); 512} 513 514void wait_on_page_bit(struct page *page, int bit_nr) 515{ 516 DEFINE_WAIT_BIT(wait, &page->flags, bit_nr); 517 518 if (test_bit(bit_nr, &page->flags)) 519 __wait_on_bit(page_waitqueue(page), &wait, sync_page, 520 TASK_UNINTERRUPTIBLE); 521} 522EXPORT_SYMBOL(wait_on_page_bit); 523 524/** 525 * add_page_wait_queue - Add an arbitrary waiter to a page's wait queue 526 * @page: Page defining the wait queue of interest 527 * @waiter: Waiter to add to the queue 528 * 529 * Add an arbitrary @waiter to the wait queue for the nominated @page. 530 */ 531void add_page_wait_queue(struct page *page, wait_queue_t *waiter) 532{ 533 wait_queue_head_t *q = page_waitqueue(page); 534 unsigned long flags; 535 536 spin_lock_irqsave(&q->lock, flags); 537 __add_wait_queue(q, waiter); 538 spin_unlock_irqrestore(&q->lock, flags); 539} 540EXPORT_SYMBOL_GPL(add_page_wait_queue); 541 542/** 543 * unlock_page - unlock a locked page 544 * @page: the page 545 * 546 * Unlocks the page and wakes up sleepers in ___wait_on_page_locked(). 547 * Also wakes sleepers in wait_on_page_writeback() because the wakeup 548 * mechananism between PageLocked pages and PageWriteback pages is shared. 549 * But that's OK - sleepers in wait_on_page_writeback() just go back to sleep. 550 * 551 * The mb is necessary to enforce ordering between the clear_bit and the read 552 * of the waitqueue (to avoid SMP races with a parallel wait_on_page_locked()). 553 */ 554void unlock_page(struct page *page) 555{ 556 VM_BUG_ON(!PageLocked(page)); 557 clear_bit_unlock(PG_locked, &page->flags); 558 smp_mb__after_clear_bit(); 559 wake_up_page(page, PG_locked); 560} 561EXPORT_SYMBOL(unlock_page); 562 563/** 564 * end_page_writeback - end writeback against a page 565 * @page: the page 566 */ 567void end_page_writeback(struct page *page) 568{ 569 if (TestClearPageReclaim(page)) 570 rotate_reclaimable_page(page); 571 572 if (!test_clear_page_writeback(page)) 573 BUG(); 574 575 smp_mb__after_clear_bit(); 576 wake_up_page(page, PG_writeback); 577} 578EXPORT_SYMBOL(end_page_writeback); 579 580/** 581 * __lock_page - get a lock on the page, assuming we need to sleep to get it 582 * @page: the page to lock 583 * 584 * Ugly. Running sync_page() in state TASK_UNINTERRUPTIBLE is scary. If some 585 * random driver's requestfn sets TASK_RUNNING, we could busywait. However 586 * chances are that on the second loop, the block layer's plug list is empty, 587 * so sync_page() will then return in state TASK_UNINTERRUPTIBLE. 588 */ 589void __lock_page(struct page *page) 590{ 591 DEFINE_WAIT_BIT(wait, &page->flags, PG_locked); 592 593 __wait_on_bit_lock(page_waitqueue(page), &wait, sync_page, 594 TASK_UNINTERRUPTIBLE); 595} 596EXPORT_SYMBOL(__lock_page); 597 598int __lock_page_killable(struct page *page) 599{ 600 DEFINE_WAIT_BIT(wait, &page->flags, PG_locked); 601 602 return __wait_on_bit_lock(page_waitqueue(page), &wait, 603 sync_page_killable, TASK_KILLABLE); 604} 605EXPORT_SYMBOL_GPL(__lock_page_killable); 606 607/** 608 * __lock_page_nosync - get a lock on the page, without calling sync_page() 609 * @page: the page to lock 610 * 611 * Variant of lock_page that does not require the caller to hold a reference 612 * on the page's mapping. 613 */ 614void __lock_page_nosync(struct page *page) 615{ 616 DEFINE_WAIT_BIT(wait, &page->flags, PG_locked); 617 __wait_on_bit_lock(page_waitqueue(page), &wait, __sleep_on_page_lock, 618 TASK_UNINTERRUPTIBLE); 619} 620 621/** 622 * find_get_page - find and get a page reference 623 * @mapping: the address_space to search 624 * @offset: the page index 625 * 626 * Is there a pagecache struct page at the given (mapping, offset) tuple? 627 * If yes, increment its refcount and return it; if no, return NULL. 628 */ 629struct page *find_get_page(struct address_space *mapping, pgoff_t offset) 630{ 631 void **pagep; 632 struct page *page; 633 634 rcu_read_lock(); 635repeat: 636 page = NULL; 637 pagep = radix_tree_lookup_slot(&mapping->page_tree, offset); 638 if (pagep) { 639 page = radix_tree_deref_slot(pagep); 640 if (unlikely(!page || page == RADIX_TREE_RETRY)) 641 goto repeat; 642 643 if (!page_cache_get_speculative(page)) 644 goto repeat; 645 646 /* 647 * Has the page moved? 648 * This is part of the lockless pagecache protocol. See 649 * include/linux/pagemap.h for details. 650 */ 651 if (unlikely(page != *pagep)) { 652 page_cache_release(page); 653 goto repeat; 654 } 655 } 656 rcu_read_unlock(); 657 658 return page; 659} 660EXPORT_SYMBOL(find_get_page); 661 662/** 663 * find_lock_page - locate, pin and lock a pagecache page 664 * @mapping: the address_space to search 665 * @offset: the page index 666 * 667 * Locates the desired pagecache page, locks it, increments its reference 668 * count and returns its address. 669 * 670 * Returns zero if the page was not present. find_lock_page() may sleep. 671 */ 672struct page *find_lock_page(struct address_space *mapping, pgoff_t offset) 673{ 674 struct page *page; 675 676repeat: 677 page = find_get_page(mapping, offset); 678 if (page) { 679 lock_page(page); 680 /* Has the page been truncated? */ 681 if (unlikely(page->mapping != mapping)) { 682 unlock_page(page); 683 page_cache_release(page); 684 goto repeat; 685 } 686 VM_BUG_ON(page->index != offset); 687 } 688 return page; 689} 690EXPORT_SYMBOL(find_lock_page); 691 692/** 693 * find_or_create_page - locate or add a pagecache page 694 * @mapping: the page's address_space 695 * @index: the page's index into the mapping 696 * @gfp_mask: page allocation mode 697 * 698 * Locates a page in the pagecache. If the page is not present, a new page 699 * is allocated using @gfp_mask and is added to the pagecache and to the VM's 700 * LRU list. The returned page is locked and has its reference count 701 * incremented. 702 * 703 * find_or_create_page() may sleep, even if @gfp_flags specifies an atomic 704 * allocation! 705 * 706 * find_or_create_page() returns the desired page's address, or zero on 707 * memory exhaustion. 708 */ 709struct page *find_or_create_page(struct address_space *mapping, 710 pgoff_t index, gfp_t gfp_mask) 711{ 712 struct page *page; 713 int err; 714repeat: 715 page = find_lock_page(mapping, index); 716 if (!page) { 717 page = __page_cache_alloc(gfp_mask); 718 if (!page) 719 return NULL; 720 /* 721 * We want a regular kernel memory (not highmem or DMA etc) 722 * allocation for the radix tree nodes, but we need to honour 723 * the context-specific requirements the caller has asked for. 724 * GFP_RECLAIM_MASK collects those requirements. 725 */ 726 err = add_to_page_cache_lru(page, mapping, index, 727 (gfp_mask & GFP_RECLAIM_MASK)); 728 if (unlikely(err)) { 729 page_cache_release(page); 730 page = NULL; 731 if (err == -EEXIST) 732 goto repeat; 733 } 734 } 735 return page; 736} 737EXPORT_SYMBOL(find_or_create_page); 738 739/** 740 * find_get_pages - gang pagecache lookup 741 * @mapping: The address_space to search 742 * @start: The starting page index 743 * @nr_pages: The maximum number of pages 744 * @pages: Where the resulting pages are placed 745 * 746 * find_get_pages() will search for and return a group of up to 747 * @nr_pages pages in the mapping. The pages are placed at @pages. 748 * find_get_pages() takes a reference against the returned pages. 749 * 750 * The search returns a group of mapping-contiguous pages with ascending 751 * indexes. There may be holes in the indices due to not-present pages. 752 * 753 * find_get_pages() returns the number of pages which were found. 754 */ 755unsigned find_get_pages(struct address_space *mapping, pgoff_t start, 756 unsigned int nr_pages, struct page **pages) 757{ 758 unsigned int i; 759 unsigned int ret; 760 unsigned int nr_found; 761 762 rcu_read_lock(); 763restart: 764 nr_found = radix_tree_gang_lookup_slot(&mapping->page_tree, 765 (void ***)pages, start, nr_pages); 766 ret = 0; 767 for (i = 0; i < nr_found; i++) { 768 struct page *page; 769repeat: 770 page = radix_tree_deref_slot((void **)pages[i]); 771 if (unlikely(!page)) 772 continue; 773 /* 774 * this can only trigger if nr_found == 1, making livelock 775 * a non issue. 776 */ 777 if (unlikely(page == RADIX_TREE_RETRY)) 778 goto restart; 779 780 if (!page_cache_get_speculative(page)) 781 goto repeat; 782 783 /* Has the page moved? */ 784 if (unlikely(page != *((void **)pages[i]))) { 785 page_cache_release(page); 786 goto repeat; 787 } 788 789 pages[ret] = page; 790 ret++; 791 } 792 rcu_read_unlock(); 793 return ret; 794} 795 796/** 797 * find_get_pages_contig - gang contiguous pagecache lookup 798 * @mapping: The address_space to search 799 * @index: The starting page index 800 * @nr_pages: The maximum number of pages 801 * @pages: Where the resulting pages are placed 802 * 803 * find_get_pages_contig() works exactly like find_get_pages(), except 804 * that the returned number of pages are guaranteed to be contiguous. 805 * 806 * find_get_pages_contig() returns the number of pages which were found. 807 */ 808unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t index, 809 unsigned int nr_pages, struct page **pages) 810{ 811 unsigned int i; 812 unsigned int ret; 813 unsigned int nr_found; 814 815 rcu_read_lock(); 816restart: 817 nr_found = radix_tree_gang_lookup_slot(&mapping->page_tree, 818 (void ***)pages, index, nr_pages); 819 ret = 0; 820 for (i = 0; i < nr_found; i++) { 821 struct page *page; 822repeat: 823 page = radix_tree_deref_slot((void **)pages[i]); 824 if (unlikely(!page)) 825 continue; 826 /* 827 * this can only trigger if nr_found == 1, making livelock 828 * a non issue. 829 */ 830 if (unlikely(page == RADIX_TREE_RETRY)) 831 goto restart; 832 833 if (page->mapping == NULL || page->index != index) 834 break; 835 836 if (!page_cache_get_speculative(page)) 837 goto repeat; 838 839 /* Has the page moved? */ 840 if (unlikely(page != *((void **)pages[i]))) { 841 page_cache_release(page); 842 goto repeat; 843 } 844 845 pages[ret] = page; 846 ret++; 847 index++; 848 } 849 rcu_read_unlock(); 850 return ret; 851} 852EXPORT_SYMBOL(find_get_pages_contig); 853 854/** 855 * find_get_pages_tag - find and return pages that match @tag 856 * @mapping: the address_space to search 857 * @index: the starting page index 858 * @tag: the tag index 859 * @nr_pages: the maximum number of pages 860 * @pages: where the resulting pages are placed 861 * 862 * Like find_get_pages, except we only return pages which are tagged with 863 * @tag. We update @index to index the next page for the traversal. 864 */ 865unsigned find_get_pages_tag(struct address_space *mapping, pgoff_t *index, 866 int tag, unsigned int nr_pages, struct page **pages) 867{ 868 unsigned int i; 869 unsigned int ret; 870 unsigned int nr_found; 871 872 rcu_read_lock(); 873restart: 874 nr_found = radix_tree_gang_lookup_tag_slot(&mapping->page_tree, 875 (void ***)pages, *index, nr_pages, tag); 876 ret = 0; 877 for (i = 0; i < nr_found; i++) { 878 struct page *page; 879repeat: 880 page = radix_tree_deref_slot((void **)pages[i]); 881 if (unlikely(!page)) 882 continue; 883 /* 884 * this can only trigger if nr_found == 1, making livelock 885 * a non issue. 886 */ 887 if (unlikely(page == RADIX_TREE_RETRY)) 888 goto restart; 889 890 if (!page_cache_get_speculative(page)) 891 goto repeat; 892 893 /* Has the page moved? */ 894 if (unlikely(page != *((void **)pages[i]))) { 895 page_cache_release(page); 896 goto repeat; 897 } 898 899 pages[ret] = page; 900 ret++; 901 } 902 rcu_read_unlock(); 903 904 if (ret) 905 *index = pages[ret - 1]->index + 1; 906 907 return ret; 908} 909EXPORT_SYMBOL(find_get_pages_tag); 910 911/** 912 * grab_cache_page_nowait - returns locked page at given index in given cache 913 * @mapping: target address_space 914 * @index: the page index 915 * 916 * Same as grab_cache_page(), but do not wait if the page is unavailable. 917 * This is intended for speculative data generators, where the data can 918 * be regenerated if the page couldn't be grabbed. This routine should 919 * be safe to call while holding the lock for another page. 920 * 921 * Clear __GFP_FS when allocating the page to avoid recursion into the fs 922 * and deadlock against the caller's locked page. 923 */ 924struct page * 925grab_cache_page_nowait(struct address_space *mapping, pgoff_t index) 926{ 927 struct page *page = find_get_page(mapping, index); 928 929 if (page) { 930 if (trylock_page(page)) 931 return page; 932 page_cache_release(page); 933 return NULL; 934 } 935 page = __page_cache_alloc(mapping_gfp_mask(mapping) & ~__GFP_FS); 936 if (page && add_to_page_cache_lru(page, mapping, index, GFP_NOFS)) { 937 page_cache_release(page); 938 page = NULL; 939 } 940 return page; 941} 942EXPORT_SYMBOL(grab_cache_page_nowait); 943 944/* 945 * CD/DVDs are error prone. When a medium error occurs, the driver may fail 946 * a _large_ part of the i/o request. Imagine the worst scenario: 947 * 948 * ---R__________________________________________B__________ 949 * ^ reading here ^ bad block(assume 4k) 950 * 951 * read(R) => miss => readahead(R...B) => media error => frustrating retries 952 * => failing the whole request => read(R) => read(R+1) => 953 * readahead(R+1...B+1) => bang => read(R+2) => read(R+3) => 954 * readahead(R+3...B+2) => bang => read(R+3) => read(R+4) => 955 * readahead(R+4...B+3) => bang => read(R+4) => read(R+5) => ...... 956 * 957 * It is going insane. Fix it by quickly scaling down the readahead size. 958 */ 959static void shrink_readahead_size_eio(struct file *filp, 960 struct file_ra_state *ra) 961{ 962 ra->ra_pages /= 4; 963} 964 965/** 966 * do_generic_file_read - generic file read routine 967 * @filp: the file to read 968 * @ppos: current file position 969 * @desc: read_descriptor 970 * @actor: read method 971 * 972 * This is a generic file read routine, and uses the 973 * mapping->a_ops->readpage() function for the actual low-level stuff. 974 * 975 * This is really ugly. But the goto's actually try to clarify some 976 * of the logic when it comes to error handling etc. 977 */ 978static void do_generic_file_read(struct file *filp, loff_t *ppos, 979 read_descriptor_t *desc, read_actor_t actor) 980{ 981 struct address_space *mapping = filp->f_mapping; 982 struct inode *inode = mapping->host; 983 struct file_ra_state *ra = &filp->f_ra; 984 pgoff_t index; 985 pgoff_t last_index; 986 pgoff_t prev_index; 987 unsigned long offset; /* offset into pagecache page */ 988 unsigned int prev_offset; 989 int error; 990 991 index = *ppos >> PAGE_CACHE_SHIFT; 992 prev_index = ra->prev_pos >> PAGE_CACHE_SHIFT; 993 prev_offset = ra->prev_pos & (PAGE_CACHE_SIZE-1); 994 last_index = (*ppos + desc->count + PAGE_CACHE_SIZE-1) >> PAGE_CACHE_SHIFT; 995 offset = *ppos & ~PAGE_CACHE_MASK; 996 997 for (;;) { 998 struct page *page; 999 pgoff_t end_index; 1000 loff_t isize; 1001 unsigned long nr, ret; 1002 1003 cond_resched(); 1004find_page: 1005 page = find_get_page(mapping, index); 1006 if (!page) { 1007 page_cache_sync_readahead(mapping, 1008 ra, filp, 1009 index, last_index - index); 1010 page = find_get_page(mapping, index); 1011 if (unlikely(page == NULL)) 1012 goto no_cached_page; 1013 } 1014 if (PageReadahead(page)) { 1015 page_cache_async_readahead(mapping, 1016 ra, filp, page, 1017 index, last_index - index); 1018 } 1019 if (!PageUptodate(page)) { 1020 if (inode->i_blkbits == PAGE_CACHE_SHIFT || 1021 !mapping->a_ops->is_partially_uptodate) 1022 goto page_not_up_to_date; 1023 if (!trylock_page(page)) 1024 goto page_not_up_to_date; 1025 if (!mapping->a_ops->is_partially_uptodate(page, 1026 desc, offset)) 1027 goto page_not_up_to_date_locked; 1028 unlock_page(page); 1029 } 1030page_ok: 1031 /* 1032 * i_size must be checked after we know the page is Uptodate. 1033 * 1034 * Checking i_size after the check allows us to calculate 1035 * the correct value for "nr", which means the zero-filled 1036 * part of the page is not copied back to userspace (unless 1037 * another truncate extends the file - this is desired though). 1038 */ 1039 1040 isize = i_size_read(inode); 1041 end_index = (isize - 1) >> PAGE_CACHE_SHIFT; 1042 if (unlikely(!isize || index > end_index)) { 1043 page_cache_release(page); 1044 goto out; 1045 } 1046 1047 /* nr is the maximum number of bytes to copy from this page */ 1048 nr = PAGE_CACHE_SIZE; 1049 if (index == end_index) { 1050 nr = ((isize - 1) & ~PAGE_CACHE_MASK) + 1; 1051 if (nr <= offset) { 1052 page_cache_release(page); 1053 goto out; 1054 } 1055 } 1056 nr = nr - offset; 1057 1058 /* If users can be writing to this page using arbitrary 1059 * virtual addresses, take care about potential aliasing 1060 * before reading the page on the kernel side. 1061 */ 1062 if (mapping_writably_mapped(mapping)) 1063 flush_dcache_page(page); 1064 1065 /* 1066 * When a sequential read accesses a page several times, 1067 * only mark it as accessed the first time. 1068 */ 1069 if (prev_index != index || offset != prev_offset) 1070 mark_page_accessed(page); 1071 prev_index = index; 1072 1073 /* 1074 * Ok, we have the page, and it's up-to-date, so 1075 * now we can copy it to user space... 1076 * 1077 * The actor routine returns how many bytes were actually used.. 1078 * NOTE! This may not be the same as how much of a user buffer 1079 * we filled up (we may be padding etc), so we can only update 1080 * "pos" here (the actor routine has to update the user buffer 1081 * pointers and the remaining count). 1082 */ 1083 ret = actor(desc, page, offset, nr); 1084 offset += ret; 1085 index += offset >> PAGE_CACHE_SHIFT; 1086 offset &= ~PAGE_CACHE_MASK; 1087 prev_offset = offset; 1088 1089 page_cache_release(page); 1090 if (ret == nr && desc->count) 1091 continue; 1092 goto out; 1093 1094page_not_up_to_date: 1095 /* Get exclusive access to the page ... */ 1096 error = lock_page_killable(page); 1097 if (unlikely(error)) 1098 goto readpage_error; 1099 1100page_not_up_to_date_locked: 1101 /* Did it get truncated before we got the lock? */ 1102 if (!page->mapping) { 1103 unlock_page(page); 1104 page_cache_release(page); 1105 continue; 1106 } 1107 1108 /* Did somebody else fill it already? */ 1109 if (PageUptodate(page)) { 1110 unlock_page(page); 1111 goto page_ok; 1112 } 1113 1114readpage: 1115 /* Start the actual read. The read will unlock the page. */ 1116 error = mapping->a_ops->readpage(filp, page); 1117 1118 if (unlikely(error)) { 1119 if (error == AOP_TRUNCATED_PAGE) { 1120 page_cache_release(page); 1121 goto find_page; 1122 } 1123 goto readpage_error; 1124 } 1125 1126 if (!PageUptodate(page)) { 1127 error = lock_page_killable(page); 1128 if (unlikely(error)) 1129 goto readpage_error; 1130 if (!PageUptodate(page)) { 1131 if (page->mapping == NULL) { 1132 /* 1133 * invalidate_inode_pages got it 1134 */ 1135 unlock_page(page); 1136 page_cache_release(page); 1137 goto find_page; 1138 } 1139 unlock_page(page); 1140 shrink_readahead_size_eio(filp, ra); 1141 error = -EIO; 1142 goto readpage_error; 1143 } 1144 unlock_page(page); 1145 } 1146 1147 goto page_ok; 1148 1149readpage_error: 1150 /* UHHUH! A synchronous read error occurred. Report it */ 1151 desc->error = error; 1152 page_cache_release(page); 1153 goto out; 1154 1155no_cached_page: 1156 /* 1157 * Ok, it wasn't cached, so we need to create a new 1158 * page.. 1159 */ 1160 page = page_cache_alloc_cold(mapping); 1161 if (!page) { 1162 desc->error = -ENOMEM; 1163 goto out; 1164 } 1165 error = add_to_page_cache_lru(page, mapping, 1166 index, GFP_KERNEL); 1167 if (error) { 1168 page_cache_release(page); 1169 if (error == -EEXIST) 1170 goto find_page; 1171 desc->error = error; 1172 goto out; 1173 } 1174 goto readpage; 1175 } 1176 1177out: 1178 ra->prev_pos = prev_index; 1179 ra->prev_pos <<= PAGE_CACHE_SHIFT; 1180 ra->prev_pos |= prev_offset; 1181 1182 *ppos = ((loff_t)index << PAGE_CACHE_SHIFT) + offset; 1183 file_accessed(filp); 1184} 1185 1186int file_read_actor(read_descriptor_t *desc, struct page *page, 1187 unsigned long offset, unsigned long size) 1188{ 1189 char *kaddr; 1190 unsigned long left, count = desc->count; 1191 1192 if (size > count) 1193 size = count; 1194 1195 /* 1196 * Faults on the destination of a read are common, so do it before 1197 * taking the kmap. 1198 */ 1199 if (!fault_in_pages_writeable(desc->arg.buf, size)) { 1200 kaddr = kmap_atomic(page, KM_USER0); 1201 left = __copy_to_user_inatomic(desc->arg.buf, 1202 kaddr + offset, size); 1203 kunmap_atomic(kaddr, KM_USER0); 1204 if (left == 0) 1205 goto success; 1206 } 1207 1208 /* Do it the slow way */ 1209 kaddr = kmap(page); 1210 left = __copy_to_user(desc->arg.buf, kaddr + offset, size); 1211 kunmap(page); 1212 1213 if (left) { 1214 size -= left; 1215 desc->error = -EFAULT; 1216 } 1217success: 1218 desc->count = count - size; 1219 desc->written += size; 1220 desc->arg.buf += size; 1221 return size; 1222} 1223 1224/* 1225 * Performs necessary checks before doing a write 1226 * @iov: io vector request 1227 * @nr_segs: number of segments in the iovec 1228 * @count: number of bytes to write 1229 * @access_flags: type of access: %VERIFY_READ or %VERIFY_WRITE 1230 * 1231 * Adjust number of segments and amount of bytes to write (nr_segs should be 1232 * properly initialized first). Returns appropriate error code that caller 1233 * should return or zero in case that write should be allowed. 1234 */ 1235int generic_segment_checks(const struct iovec *iov, 1236 unsigned long *nr_segs, size_t *count, int access_flags) 1237{ 1238 unsigned long seg; 1239 size_t cnt = 0; 1240 for (seg = 0; seg < *nr_segs; seg++) { 1241 const struct iovec *iv = &iov[seg]; 1242 1243 /* 1244 * If any segment has a negative length, or the cumulative 1245 * length ever wraps negative then return -EINVAL. 1246 */ 1247 cnt += iv->iov_len; 1248 if (unlikely((ssize_t)(cnt|iv->iov_len) < 0)) 1249 return -EINVAL; 1250 if (access_ok(access_flags, iv->iov_base, iv->iov_len)) 1251 continue; 1252 if (seg == 0) 1253 return -EFAULT; 1254 *nr_segs = seg; 1255 cnt -= iv->iov_len; /* This segment is no good */ 1256 break; 1257 } 1258 *count = cnt; 1259 return 0; 1260} 1261EXPORT_SYMBOL(generic_segment_checks); 1262 1263/** 1264 * generic_file_aio_read - generic filesystem read routine 1265 * @iocb: kernel I/O control block 1266 * @iov: io vector request 1267 * @nr_segs: number of segments in the iovec 1268 * @pos: current file position 1269 * 1270 * This is the "read()" routine for all filesystems 1271 * that can use the page cache directly. 1272 */ 1273ssize_t 1274generic_file_aio_read(struct kiocb *iocb, const struct iovec *iov, 1275 unsigned long nr_segs, loff_t pos) 1276{ 1277 struct file *filp = iocb->ki_filp; 1278 ssize_t retval; 1279 unsigned long seg; 1280 size_t count; 1281 loff_t *ppos = &iocb->ki_pos; 1282 1283 count = 0; 1284 retval = generic_segment_checks(iov, &nr_segs, &count, VERIFY_WRITE); 1285 if (retval) 1286 return retval; 1287 1288 /* coalesce the iovecs and go direct-to-BIO for O_DIRECT */ 1289 if (filp->f_flags & O_DIRECT) { 1290 loff_t size; 1291 struct address_space *mapping; 1292 struct inode *inode; 1293 1294 mapping = filp->f_mapping; 1295 inode = mapping->host; 1296 if (!count) 1297 goto out; /* skip atime */ 1298 size = i_size_read(inode); 1299 if (pos < size) { 1300 retval = filemap_write_and_wait_range(mapping, pos, 1301 pos + iov_length(iov, nr_segs) - 1); 1302 if (!retval) { 1303 retval = mapping->a_ops->direct_IO(READ, iocb, 1304 iov, pos, nr_segs); 1305 } 1306 if (retval > 0) 1307 *ppos = pos + retval; 1308 if (retval) { 1309 file_accessed(filp); 1310 goto out; 1311 } 1312 } 1313 } 1314 1315 for (seg = 0; seg < nr_segs; seg++) { 1316 read_descriptor_t desc; 1317 1318 desc.written = 0; 1319 desc.arg.buf = iov[seg].iov_base; 1320 desc.count = iov[seg].iov_len; 1321 if (desc.count == 0) 1322 continue; 1323 desc.error = 0; 1324 do_generic_file_read(filp, ppos, &desc, file_read_actor); 1325 retval += desc.written; 1326 if (desc.error) { 1327 retval = retval ?: desc.error; 1328 break; 1329 } 1330 if (desc.count > 0) 1331 break; 1332 } 1333out: 1334 return retval; 1335} 1336EXPORT_SYMBOL(generic_file_aio_read); 1337 1338static ssize_t 1339do_readahead(struct address_space *mapping, struct file *filp, 1340 pgoff_t index, unsigned long nr) 1341{ 1342 if (!mapping || !mapping->a_ops || !mapping->a_ops->readpage) 1343 return -EINVAL; 1344 1345 force_page_cache_readahead(mapping, filp, index, nr); 1346 return 0; 1347} 1348 1349SYSCALL_DEFINE(readahead)(int fd, loff_t offset, size_t count) 1350{ 1351 ssize_t ret; 1352 struct file *file; 1353 1354 ret = -EBADF; 1355 file = fget(fd); 1356 if (file) { 1357 if (file->f_mode & FMODE_READ) { 1358 struct address_space *mapping = file->f_mapping; 1359 pgoff_t start = offset >> PAGE_CACHE_SHIFT; 1360 pgoff_t end = (offset + count - 1) >> PAGE_CACHE_SHIFT; 1361 unsigned long len = end - start + 1; 1362 ret = do_readahead(mapping, file, start, len); 1363 } 1364 fput(file); 1365 } 1366 return ret; 1367} 1368#ifdef CONFIG_HAVE_SYSCALL_WRAPPERS 1369asmlinkage long SyS_readahead(long fd, loff_t offset, long count) 1370{ 1371 return SYSC_readahead((int) fd, offset, (size_t) count); 1372} 1373SYSCALL_ALIAS(sys_readahead, SyS_readahead); 1374#endif 1375 1376#ifdef CONFIG_MMU 1377/** 1378 * page_cache_read - adds requested page to the page cache if not already there 1379 * @file: file to read 1380 * @offset: page index 1381 * 1382 * This adds the requested page to the page cache if it isn't already there, 1383 * and schedules an I/O to read in its contents from disk. 1384 */ 1385static int page_cache_read(struct file *file, pgoff_t offset) 1386{ 1387 struct address_space *mapping = file->f_mapping; 1388 struct page *page; 1389 int ret; 1390 1391 do { 1392 page = page_cache_alloc_cold(mapping); 1393 if (!page) 1394 return -ENOMEM; 1395 1396 ret = add_to_page_cache_lru(page, mapping, offset, GFP_KERNEL); 1397 if (ret == 0) 1398 ret = mapping->a_ops->readpage(file, page); 1399 else if (ret == -EEXIST) 1400 ret = 0; /* losing race to add is OK */ 1401 1402 page_cache_release(page); 1403 1404 } while (ret == AOP_TRUNCATED_PAGE); 1405 1406 return ret; 1407} 1408 1409#define MMAP_LOTSAMISS (100) 1410 1411/* 1412 * Synchronous readahead happens when we don't even find 1413 * a page in the page cache at all. 1414 */ 1415static void do_sync_mmap_readahead(struct vm_area_struct *vma, 1416 struct file_ra_state *ra, 1417 struct file *file, 1418 pgoff_t offset) 1419{ 1420 unsigned long ra_pages; 1421 struct address_space *mapping = file->f_mapping; 1422 1423 /* If we don't want any read-ahead, don't bother */ 1424 if (VM_RandomReadHint(vma)) 1425 return; 1426 1427 if (VM_SequentialReadHint(vma) || 1428 offset - 1 == (ra->prev_pos >> PAGE_CACHE_SHIFT)) { 1429 page_cache_sync_readahead(mapping, ra, file, offset, 1430 ra->ra_pages); 1431 return; 1432 } 1433 1434 if (ra->mmap_miss < INT_MAX) 1435 ra->mmap_miss++; 1436 1437 /* 1438 * Do we miss much more than hit in this file? If so, 1439 * stop bothering with read-ahead. It will only hurt. 1440 */ 1441 if (ra->mmap_miss > MMAP_LOTSAMISS) 1442 return; 1443 1444 /* 1445 * mmap read-around 1446 */ 1447 ra_pages = max_sane_readahead(ra->ra_pages); 1448 if (ra_pages) { 1449 ra->start = max_t(long, 0, offset - ra_pages/2); 1450 ra->size = ra_pages; 1451 ra->async_size = 0; 1452 ra_submit(ra, mapping, file); 1453 } 1454} 1455 1456/* 1457 * Asynchronous readahead happens when we find the page and PG_readahead, 1458 * so we want to possibly extend the readahead further.. 1459 */ 1460static void do_async_mmap_readahead(struct vm_area_struct *vma, 1461 struct file_ra_state *ra, 1462 struct file *file, 1463 struct page *page, 1464 pgoff_t offset) 1465{ 1466 struct address_space *mapping = file->f_mapping; 1467 1468 /* If we don't want any read-ahead, don't bother */ 1469 if (VM_RandomReadHint(vma)) 1470 return; 1471 if (ra->mmap_miss > 0) 1472 ra->mmap_miss--; 1473 if (PageReadahead(page)) 1474 page_cache_async_readahead(mapping, ra, file, 1475 page, offset, ra->ra_pages); 1476} 1477 1478/** 1479 * filemap_fault - read in file data for page fault handling 1480 * @vma: vma in which the fault was taken 1481 * @vmf: struct vm_fault containing details of the fault 1482 * 1483 * filemap_fault() is invoked via the vma operations vector for a 1484 * mapped memory region to read in file data during a page fault. 1485 * 1486 * The goto's are kind of ugly, but this streamlines the normal case of having 1487 * it in the page cache, and handles the special cases reasonably without 1488 * having a lot of duplicated code. 1489 */ 1490int filemap_fault(struct vm_area_struct *vma, struct vm_fault *vmf) 1491{ 1492 int error; 1493 struct file *file = vma->vm_file; 1494 struct address_space *mapping = file->f_mapping; 1495 struct file_ra_state *ra = &file->f_ra; 1496 struct inode *inode = mapping->host; 1497 pgoff_t offset = vmf->pgoff; 1498 struct page *page; 1499 pgoff_t size; 1500 int ret = 0; 1501 1502 size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT; 1503 if (offset >= size) 1504 return VM_FAULT_SIGBUS; 1505 1506 /* 1507 * Do we have something in the page cache already? 1508 */ 1509 page = find_get_page(mapping, offset); 1510 if (likely(page)) { 1511 /* 1512 * We found the page, so try async readahead before 1513 * waiting for the lock. 1514 */ 1515 do_async_mmap_readahead(vma, ra, file, page, offset); 1516 lock_page(page); 1517 1518 /* Did it get truncated? */ 1519 if (unlikely(page->mapping != mapping)) { 1520 unlock_page(page); 1521 put_page(page); 1522 goto no_cached_page; 1523 } 1524 } else { 1525 /* No page in the page cache at all */ 1526 do_sync_mmap_readahead(vma, ra, file, offset); 1527 count_vm_event(PGMAJFAULT); 1528 ret = VM_FAULT_MAJOR; 1529retry_find: 1530 page = find_lock_page(mapping, offset); 1531 if (!page) 1532 goto no_cached_page; 1533 } 1534 1535 /* 1536 * We have a locked page in the page cache, now we need to check 1537 * that it's up-to-date. If not, it is going to be due to an error. 1538 */ 1539 if (unlikely(!PageUptodate(page))) 1540 goto page_not_uptodate; 1541 1542 /* 1543 * Found the page and have a reference on it. 1544 * We must recheck i_size under page lock. 1545 */ 1546 size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT; 1547 if (unlikely(offset >= size)) { 1548 unlock_page(page); 1549 page_cache_release(page); 1550 return VM_FAULT_SIGBUS; 1551 } 1552 1553 ra->prev_pos = (loff_t)offset << PAGE_CACHE_SHIFT; 1554 vmf->page = page; 1555 return ret | VM_FAULT_LOCKED; 1556 1557no_cached_page: 1558 /* 1559 * We're only likely to ever get here if MADV_RANDOM is in 1560 * effect. 1561 */ 1562 error = page_cache_read(file, offset); 1563 1564 /* 1565 * The page we want has now been added to the page cache. 1566 * In the unlikely event that someone removed it in the 1567 * meantime, we'll just come back here and read it again. 1568 */ 1569 if (error >= 0) 1570 goto retry_find; 1571 1572 /* 1573 * An error return from page_cache_read can result if the 1574 * system is low on memory, or a problem occurs while trying 1575 * to schedule I/O. 1576 */ 1577 if (error == -ENOMEM) 1578 return VM_FAULT_OOM; 1579 return VM_FAULT_SIGBUS; 1580 1581page_not_uptodate: 1582 /* 1583 * Umm, take care of errors if the page isn't up-to-date. 1584 * Try to re-read it _once_. We do this synchronously, 1585 * because there really aren't any performance issues here 1586 * and we need to check for errors. 1587 */ 1588 ClearPageError(page); 1589 error = mapping->a_ops->readpage(file, page); 1590 if (!error) { 1591 wait_on_page_locked(page); 1592 if (!PageUptodate(page)) 1593 error = -EIO; 1594 } 1595 page_cache_release(page); 1596 1597 if (!error || error == AOP_TRUNCATED_PAGE) 1598 goto retry_find; 1599 1600 /* Things didn't work out. Return zero to tell the mm layer so. */ 1601 shrink_readahead_size_eio(file, ra); 1602 return VM_FAULT_SIGBUS; 1603} 1604EXPORT_SYMBOL(filemap_fault); 1605 1606struct vm_operations_struct generic_file_vm_ops = { 1607 .fault = filemap_fault, 1608}; 1609 1610/* This is used for a general mmap of a disk file */ 1611 1612int generic_file_mmap(struct file * file, struct vm_area_struct * vma) 1613{ 1614 struct address_space *mapping = file->f_mapping; 1615 1616 if (!mapping->a_ops->readpage) 1617 return -ENOEXEC; 1618 file_accessed(file); 1619 vma->vm_ops = &generic_file_vm_ops; 1620 vma->vm_flags |= VM_CAN_NONLINEAR; 1621 return 0; 1622} 1623 1624/* 1625 * This is for filesystems which do not implement ->writepage. 1626 */ 1627int generic_file_readonly_mmap(struct file *file, struct vm_area_struct *vma) 1628{ 1629 if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_MAYWRITE)) 1630 return -EINVAL; 1631 return generic_file_mmap(file, vma); 1632} 1633#else 1634int generic_file_mmap(struct file * file, struct vm_area_struct * vma) 1635{ 1636 return -ENOSYS; 1637} 1638int generic_file_readonly_mmap(struct file * file, struct vm_area_struct * vma) 1639{ 1640 return -ENOSYS; 1641} 1642#endif /* CONFIG_MMU */ 1643 1644EXPORT_SYMBOL(generic_file_mmap); 1645EXPORT_SYMBOL(generic_file_readonly_mmap); 1646 1647static struct page *__read_cache_page(struct address_space *mapping, 1648 pgoff_t index, 1649 int (*filler)(void *,struct page*), 1650 void *data) 1651{ 1652 struct page *page; 1653 int err; 1654repeat: 1655 page = find_get_page(mapping, index); 1656 if (!page) { 1657 page = page_cache_alloc_cold(mapping); 1658 if (!page) 1659 return ERR_PTR(-ENOMEM); 1660 err = add_to_page_cache_lru(page, mapping, index, GFP_KERNEL); 1661 if (unlikely(err)) { 1662 page_cache_release(page); 1663 if (err == -EEXIST) 1664 goto repeat; 1665 /* Presumably ENOMEM for radix tree node */ 1666 return ERR_PTR(err); 1667 } 1668 err = filler(data, page); 1669 if (err < 0) { 1670 page_cache_release(page); 1671 page = ERR_PTR(err); 1672 } 1673 } 1674 return page; 1675} 1676 1677/** 1678 * read_cache_page_async - read into page cache, fill it if needed 1679 * @mapping: the page's address_space 1680 * @index: the page index 1681 * @filler: function to perform the read 1682 * @data: destination for read data 1683 * 1684 * Same as read_cache_page, but don't wait for page to become unlocked 1685 * after submitting it to the filler. 1686 * 1687 * Read into the page cache. If a page already exists, and PageUptodate() is 1688 * not set, try to fill the page but don't wait for it to become unlocked. 1689 * 1690 * If the page does not get brought uptodate, return -EIO. 1691 */ 1692struct page *read_cache_page_async(struct address_space *mapping, 1693 pgoff_t index, 1694 int (*filler)(void *,struct page*), 1695 void *data) 1696{ 1697 struct page *page; 1698 int err; 1699 1700retry: 1701 page = __read_cache_page(mapping, index, filler, data); 1702 if (IS_ERR(page)) 1703 return page; 1704 if (PageUptodate(page)) 1705 goto out; 1706 1707 lock_page(page); 1708 if (!page->mapping) { 1709 unlock_page(page); 1710 page_cache_release(page); 1711 goto retry; 1712 } 1713 if (PageUptodate(page)) { 1714 unlock_page(page); 1715 goto out; 1716 } 1717 err = filler(data, page); 1718 if (err < 0) { 1719 page_cache_release(page); 1720 return ERR_PTR(err); 1721 } 1722out: 1723 mark_page_accessed(page); 1724 return page; 1725} 1726EXPORT_SYMBOL(read_cache_page_async); 1727 1728/** 1729 * read_cache_page - read into page cache, fill it if needed 1730 * @mapping: the page's address_space 1731 * @index: the page index 1732 * @filler: function to perform the read 1733 * @data: destination for read data 1734 * 1735 * Read into the page cache. If a page already exists, and PageUptodate() is 1736 * not set, try to fill the page then wait for it to become unlocked. 1737 * 1738 * If the page does not get brought uptodate, return -EIO. 1739 */ 1740struct page *read_cache_page(struct address_space *mapping, 1741 pgoff_t index, 1742 int (*filler)(void *,struct page*), 1743 void *data) 1744{ 1745 struct page *page; 1746 1747 page = read_cache_page_async(mapping, index, filler, data); 1748 if (IS_ERR(page)) 1749 goto out; 1750 wait_on_page_locked(page); 1751 if (!PageUptodate(page)) { 1752 page_cache_release(page); 1753 page = ERR_PTR(-EIO); 1754 } 1755 out: 1756 return page; 1757} 1758EXPORT_SYMBOL(read_cache_page); 1759 1760/* 1761 * The logic we want is 1762 * 1763 * if suid or (sgid and xgrp) 1764 * remove privs 1765 */ 1766int should_remove_suid(struct dentry *dentry) 1767{ 1768 mode_t mode = dentry->d_inode->i_mode; 1769 int kill = 0; 1770 1771 /* suid always must be killed */ 1772 if (unlikely(mode & S_ISUID)) 1773 kill = ATTR_KILL_SUID; 1774 1775 /* 1776 * sgid without any exec bits is just a mandatory locking mark; leave 1777 * it alone. If some exec bits are set, it's a real sgid; kill it. 1778 */ 1779 if (unlikely((mode & S_ISGID) && (mode & S_IXGRP))) 1780 kill |= ATTR_KILL_SGID; 1781 1782 if (unlikely(kill && !capable(CAP_FSETID) && S_ISREG(mode))) 1783 return kill; 1784 1785 return 0; 1786} 1787EXPORT_SYMBOL(should_remove_suid); 1788 1789static int __remove_suid(struct dentry *dentry, int kill) 1790{ 1791 struct iattr newattrs; 1792 1793 newattrs.ia_valid = ATTR_FORCE | kill; 1794 return notify_change(dentry, &newattrs); 1795} 1796 1797int file_remove_suid(struct file *file) 1798{ 1799 struct dentry *dentry = file->f_path.dentry; 1800 int killsuid = should_remove_suid(dentry); 1801 int killpriv = security_inode_need_killpriv(dentry); 1802 int error = 0; 1803 1804 if (killpriv < 0) 1805 return killpriv; 1806 if (killpriv) 1807 error = security_inode_killpriv(dentry); 1808 if (!error && killsuid) 1809 error = __remove_suid(dentry, killsuid); 1810 1811 return error; 1812} 1813EXPORT_SYMBOL(file_remove_suid); 1814 1815static size_t __iovec_copy_from_user_inatomic(char *vaddr, 1816 const struct iovec *iov, size_t base, size_t bytes) 1817{ 1818 size_t copied = 0, left = 0; 1819 1820 while (bytes) { 1821 char __user *buf = iov->iov_base + base; 1822 int copy = min(bytes, iov->iov_len - base); 1823 1824 base = 0; 1825 left = __copy_from_user_inatomic(vaddr, buf, copy); 1826 copied += copy; 1827 bytes -= copy; 1828 vaddr += copy; 1829 iov++; 1830 1831 if (unlikely(left)) 1832 break; 1833 } 1834 return copied - left; 1835} 1836 1837/* 1838 * Copy as much as we can into the page and return the number of bytes which 1839 * were sucessfully copied. If a fault is encountered then return the number of 1840 * bytes which were copied. 1841 */ 1842size_t iov_iter_copy_from_user_atomic(struct page *page, 1843 struct iov_iter *i, unsigned long offset, size_t bytes) 1844{ 1845 char *kaddr; 1846 size_t copied; 1847 1848 BUG_ON(!in_atomic()); 1849 kaddr = kmap_atomic(page, KM_USER0); 1850 if (likely(i->nr_segs == 1)) { 1851 int left; 1852 char __user *buf = i->iov->iov_base + i->iov_offset; 1853 left = __copy_from_user_inatomic(kaddr + offset, buf, bytes); 1854 copied = bytes - left; 1855 } else { 1856 copied = __iovec_copy_from_user_inatomic(kaddr + offset, 1857 i->iov, i->iov_offset, bytes); 1858 } 1859 kunmap_atomic(kaddr, KM_USER0); 1860 1861 return copied; 1862} 1863EXPORT_SYMBOL(iov_iter_copy_from_user_atomic); 1864 1865/* 1866 * This has the same sideeffects and return value as 1867 * iov_iter_copy_from_user_atomic(). 1868 * The difference is that it attempts to resolve faults. 1869 * Page must not be locked. 1870 */ 1871size_t iov_iter_copy_from_user(struct page *page, 1872 struct iov_iter *i, unsigned long offset, size_t bytes) 1873{ 1874 char *kaddr; 1875 size_t copied; 1876 1877 kaddr = kmap(page); 1878 if (likely(i->nr_segs == 1)) { 1879 int left; 1880 char __user *buf = i->iov->iov_base + i->iov_offset; 1881 left = __copy_from_user(kaddr + offset, buf, bytes); 1882 copied = bytes - left; 1883 } else { 1884 copied = __iovec_copy_from_user_inatomic(kaddr + offset, 1885 i->iov, i->iov_offset, bytes); 1886 } 1887 kunmap(page); 1888 return copied; 1889} 1890EXPORT_SYMBOL(iov_iter_copy_from_user); 1891 1892void iov_iter_advance(struct iov_iter *i, size_t bytes) 1893{ 1894 BUG_ON(i->count < bytes); 1895 1896 if (likely(i->nr_segs == 1)) { 1897 i->iov_offset += bytes; 1898 i->count -= bytes; 1899 } else { 1900 const struct iovec *iov = i->iov; 1901 size_t base = i->iov_offset; 1902 1903 /* 1904 * The !iov->iov_len check ensures we skip over unlikely 1905 * zero-length segments (without overruning the iovec). 1906 */ 1907 while (bytes || unlikely(i->count && !iov->iov_len)) { 1908 int copy; 1909 1910 copy = min(bytes, iov->iov_len - base); 1911 BUG_ON(!i->count || i->count < copy); 1912 i->count -= copy; 1913 bytes -= copy; 1914 base += copy; 1915 if (iov->iov_len == base) { 1916 iov++; 1917 base = 0; 1918 } 1919 } 1920 i->iov = iov; 1921 i->iov_offset = base; 1922 } 1923} 1924EXPORT_SYMBOL(iov_iter_advance); 1925 1926/* 1927 * Fault in the first iovec of the given iov_iter, to a maximum length 1928 * of bytes. Returns 0 on success, or non-zero if the memory could not be 1929 * accessed (ie. because it is an invalid address). 1930 * 1931 * writev-intensive code may want this to prefault several iovecs -- that 1932 * would be possible (callers must not rely on the fact that _only_ the 1933 * first iovec will be faulted with the current implementation). 1934 */ 1935int iov_iter_fault_in_readable(struct iov_iter *i, size_t bytes) 1936{ 1937 char __user *buf = i->iov->iov_base + i->iov_offset; 1938 bytes = min(bytes, i->iov->iov_len - i->iov_offset); 1939 return fault_in_pages_readable(buf, bytes); 1940} 1941EXPORT_SYMBOL(iov_iter_fault_in_readable); 1942 1943/* 1944 * Return the count of just the current iov_iter segment. 1945 */ 1946size_t iov_iter_single_seg_count(struct iov_iter *i) 1947{ 1948 const struct iovec *iov = i->iov; 1949 if (i->nr_segs == 1) 1950 return i->count; 1951 else 1952 return min(i->count, iov->iov_len - i->iov_offset); 1953} 1954EXPORT_SYMBOL(iov_iter_single_seg_count); 1955 1956/* 1957 * Performs necessary checks before doing a write 1958 * 1959 * Can adjust writing position or amount of bytes to write. 1960 * Returns appropriate error code that caller should return or 1961 * zero in case that write should be allowed. 1962 */ 1963inline int generic_write_checks(struct file *file, loff_t *pos, size_t *count, int isblk) 1964{ 1965 struct inode *inode = file->f_mapping->host; 1966 unsigned long limit = current->signal->rlim[RLIMIT_FSIZE].rlim_cur; 1967 1968 if (unlikely(*pos < 0)) 1969 return -EINVAL; 1970 1971 if (!isblk) { 1972 /* FIXME: this is for backwards compatibility with 2.4 */ 1973 if (file->f_flags & O_APPEND) 1974 *pos = i_size_read(inode); 1975 1976 if (limit != RLIM_INFINITY) { 1977 if (*pos >= limit) { 1978 send_sig(SIGXFSZ, current, 0); 1979 return -EFBIG; 1980 } 1981 if (*count > limit - (typeof(limit))*pos) { 1982 *count = limit - (typeof(limit))*pos; 1983 } 1984 } 1985 } 1986 1987 /* 1988 * LFS rule 1989 */ 1990 if (unlikely(*pos + *count > MAX_NON_LFS && 1991 !(file->f_flags & O_LARGEFILE))) { 1992 if (*pos >= MAX_NON_LFS) { 1993 return -EFBIG; 1994 } 1995 if (*count > MAX_NON_LFS - (unsigned long)*pos) { 1996 *count = MAX_NON_LFS - (unsigned long)*pos; 1997 } 1998 } 1999 2000 /* 2001 * Are we about to exceed the fs block limit ? 2002 * 2003 * If we have written data it becomes a short write. If we have 2004 * exceeded without writing data we send a signal and return EFBIG. 2005 * Linus frestrict idea will clean these up nicely.. 2006 */ 2007 if (likely(!isblk)) { 2008 if (unlikely(*pos >= inode->i_sb->s_maxbytes)) { 2009 if (*count || *pos > inode->i_sb->s_maxbytes) { 2010 return -EFBIG; 2011 } 2012 /* zero-length writes at ->s_maxbytes are OK */ 2013 } 2014 2015 if (unlikely(*pos + *count > inode->i_sb->s_maxbytes)) 2016 *count = inode->i_sb->s_maxbytes - *pos; 2017 } else { 2018#ifdef CONFIG_BLOCK 2019 loff_t isize; 2020 if (bdev_read_only(I_BDEV(inode))) 2021 return -EPERM; 2022 isize = i_size_read(inode); 2023 if (*pos >= isize) { 2024 if (*count || *pos > isize) 2025 return -ENOSPC; 2026 } 2027 2028 if (*pos + *count > isize) 2029 *count = isize - *pos; 2030#else 2031 return -EPERM; 2032#endif 2033 } 2034 return 0; 2035} 2036EXPORT_SYMBOL(generic_write_checks); 2037 2038int pagecache_write_begin(struct file *file, struct address_space *mapping, 2039 loff_t pos, unsigned len, unsigned flags, 2040 struct page **pagep, void **fsdata) 2041{ 2042 const struct address_space_operations *aops = mapping->a_ops; 2043 2044 return aops->write_begin(file, mapping, pos, len, flags, 2045 pagep, fsdata); 2046} 2047EXPORT_SYMBOL(pagecache_write_begin); 2048 2049int pagecache_write_end(struct file *file, struct address_space *mapping, 2050 loff_t pos, unsigned len, unsigned copied, 2051 struct page *page, void *fsdata) 2052{ 2053 const struct address_space_operations *aops = mapping->a_ops; 2054 2055 mark_page_accessed(page); 2056 return aops->write_end(file, mapping, pos, len, copied, page, fsdata); 2057} 2058EXPORT_SYMBOL(pagecache_write_end); 2059 2060ssize_t 2061generic_file_direct_write(struct kiocb *iocb, const struct iovec *iov, 2062 unsigned long *nr_segs, loff_t pos, loff_t *ppos, 2063 size_t count, size_t ocount) 2064{ 2065 struct file *file = iocb->ki_filp; 2066 struct address_space *mapping = file->f_mapping; 2067 struct inode *inode = mapping->host; 2068 ssize_t written; 2069 size_t write_len; 2070 pgoff_t end; 2071 2072 if (count != ocount) 2073 *nr_segs = iov_shorten((struct iovec *)iov, *nr_segs, count); 2074 2075 write_len = iov_length(iov, *nr_segs); 2076 end = (pos + write_len - 1) >> PAGE_CACHE_SHIFT; 2077 2078 written = filemap_write_and_wait_range(mapping, pos, pos + write_len - 1); 2079 if (written) 2080 goto out; 2081 2082 /* 2083 * After a write we want buffered reads to be sure to go to disk to get 2084 * the new data. We invalidate clean cached page from the region we're 2085 * about to write. We do this *before* the write so that we can return 2086 * without clobbering -EIOCBQUEUED from ->direct_IO(). 2087 */ 2088 if (mapping->nrpages) { 2089 written = invalidate_inode_pages2_range(mapping, 2090 pos >> PAGE_CACHE_SHIFT, end); 2091 /* 2092 * If a page can not be invalidated, return 0 to fall back 2093 * to buffered write. 2094 */ 2095 if (written) { 2096 if (written == -EBUSY) 2097 return 0; 2098 goto out; 2099 } 2100 } 2101 2102 written = mapping->a_ops->direct_IO(WRITE, iocb, iov, pos, *nr_segs); 2103 2104 /* 2105 * Finally, try again to invalidate clean pages which might have been 2106 * cached by non-direct readahead, or faulted in by get_user_pages() 2107 * if the source of the write was an mmap'ed region of the file 2108 * we're writing. Either one is a pretty crazy thing to do, 2109 * so we don't support it 100%. If this invalidation 2110 * fails, tough, the write still worked... 2111 */ 2112 if (mapping->nrpages) { 2113 invalidate_inode_pages2_range(mapping, 2114 pos >> PAGE_CACHE_SHIFT, end); 2115 } 2116 2117 if (written > 0) { 2118 loff_t end = pos + written; 2119 if (end > i_size_read(inode) && !S_ISBLK(inode->i_mode)) { 2120 i_size_write(inode, end); 2121 mark_inode_dirty(inode); 2122 } 2123 *ppos = end; 2124 } 2125out: 2126 return written; 2127} 2128EXPORT_SYMBOL(generic_file_direct_write); 2129 2130/* 2131 * Find or create a page at the given pagecache position. Return the locked 2132 * page. This function is specifically for buffered writes. 2133 */ 2134struct page *grab_cache_page_write_begin(struct address_space *mapping, 2135 pgoff_t index, unsigned flags) 2136{ 2137 int status; 2138 struct page *page; 2139 gfp_t gfp_notmask = 0; 2140 if (flags & AOP_FLAG_NOFS) 2141 gfp_notmask = __GFP_FS; 2142repeat: 2143 page = find_lock_page(mapping, index); 2144 if (likely(page)) 2145 return page; 2146 2147 page = __page_cache_alloc(mapping_gfp_mask(mapping) & ~gfp_notmask); 2148 if (!page) 2149 return NULL; 2150 status = add_to_page_cache_lru(page, mapping, index, 2151 GFP_KERNEL & ~gfp_notmask); 2152 if (unlikely(status)) { 2153 page_cache_release(page); 2154 if (status == -EEXIST) 2155 goto repeat; 2156 return NULL; 2157 } 2158 return page; 2159} 2160EXPORT_SYMBOL(grab_cache_page_write_begin); 2161 2162static ssize_t generic_perform_write(struct file *file, 2163 struct iov_iter *i, loff_t pos) 2164{ 2165 struct address_space *mapping = file->f_mapping; 2166 const struct address_space_operations *a_ops = mapping->a_ops; 2167 long status = 0; 2168 ssize_t written = 0; 2169 unsigned int flags = 0; 2170 2171 /* 2172 * Copies from kernel address space cannot fail (NFSD is a big user). 2173 */ 2174 if (segment_eq(get_fs(), KERNEL_DS)) 2175 flags |= AOP_FLAG_UNINTERRUPTIBLE; 2176 2177 do { 2178 struct page *page; 2179 pgoff_t index; /* Pagecache index for current page */ 2180 unsigned long offset; /* Offset into pagecache page */ 2181 unsigned long bytes; /* Bytes to write to page */ 2182 size_t copied; /* Bytes copied from user */ 2183 void *fsdata; 2184 2185 offset = (pos & (PAGE_CACHE_SIZE - 1)); 2186 index = pos >> PAGE_CACHE_SHIFT; 2187 bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset, 2188 iov_iter_count(i)); 2189 2190again: 2191 2192 /* 2193 * Bring in the user page that we will copy from _first_. 2194 * Otherwise there's a nasty deadlock on copying from the 2195 * same page as we're writing to, without it being marked 2196 * up-to-date. 2197 * 2198 * Not only is this an optimisation, but it is also required 2199 * to check that the address is actually valid, when atomic 2200 * usercopies are used, below. 2201 */ 2202 if (unlikely(iov_iter_fault_in_readable(i, bytes))) { 2203 status = -EFAULT; 2204 break; 2205 } 2206 2207 status = a_ops->write_begin(file, mapping, pos, bytes, flags, 2208 &page, &fsdata); 2209 if (unlikely(status)) 2210 break; 2211 2212 pagefault_disable(); 2213 copied = iov_iter_copy_from_user_atomic(page, i, offset, bytes); 2214 pagefault_enable(); 2215 flush_dcache_page(page); 2216 2217 mark_page_accessed(page); 2218 status = a_ops->write_end(file, mapping, pos, bytes, copied, 2219 page, fsdata); 2220 if (unlikely(status < 0)) 2221 break; 2222 copied = status; 2223 2224 cond_resched(); 2225 2226 iov_iter_advance(i, copied); 2227 if (unlikely(copied == 0)) { 2228 /* 2229 * If we were unable to copy any data at all, we must 2230 * fall back to a single segment length write. 2231 * 2232 * If we didn't fallback here, we could livelock 2233 * because not all segments in the iov can be copied at 2234 * once without a pagefault. 2235 */ 2236 bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset, 2237 iov_iter_single_seg_count(i)); 2238 goto again; 2239 } 2240 pos += copied; 2241 written += copied; 2242 2243 balance_dirty_pages_ratelimited(mapping); 2244 2245 } while (iov_iter_count(i)); 2246 2247 return written ? written : status; 2248} 2249 2250ssize_t 2251generic_file_buffered_write(struct kiocb *iocb, const struct iovec *iov, 2252 unsigned long nr_segs, loff_t pos, loff_t *ppos, 2253 size_t count, ssize_t written) 2254{ 2255 struct file *file = iocb->ki_filp; 2256 struct address_space *mapping = file->f_mapping; 2257 ssize_t status; 2258 struct iov_iter i; 2259 2260 iov_iter_init(&i, iov, nr_segs, count, written); 2261 status = generic_perform_write(file, &i, pos); 2262 2263 if (likely(status >= 0)) { 2264 written += status; 2265 *ppos = pos + status; 2266 } 2267 2268 /* 2269 * If we get here for O_DIRECT writes then we must have fallen through 2270 * to buffered writes (block instantiation inside i_size). So we sync 2271 * the file data here, to try to honour O_DIRECT expectations. 2272 */ 2273 if (unlikely(file->f_flags & O_DIRECT) && written) 2274 status = filemap_write_and_wait_range(mapping, 2275 pos, pos + written - 1); 2276 2277 return written ? written : status; 2278} 2279EXPORT_SYMBOL(generic_file_buffered_write); 2280 2281/** 2282 * __generic_file_aio_write - write data to a file 2283 * @iocb: IO state structure (file, offset, etc.) 2284 * @iov: vector with data to write 2285 * @nr_segs: number of segments in the vector 2286 * @ppos: position where to write 2287 * 2288 * This function does all the work needed for actually writing data to a 2289 * file. It does all basic checks, removes SUID from the file, updates 2290 * modification times and calls proper subroutines depending on whether we 2291 * do direct IO or a standard buffered write. 2292 * 2293 * It expects i_mutex to be grabbed unless we work on a block device or similar 2294 * object which does not need locking at all. 2295 * 2296 * This function does *not* take care of syncing data in case of O_SYNC write. 2297 * A caller has to handle it. This is mainly due to the fact that we want to 2298 * avoid syncing under i_mutex. 2299 */ 2300ssize_t __generic_file_aio_write(struct kiocb *iocb, const struct iovec *iov, 2301 unsigned long nr_segs, loff_t *ppos) 2302{ 2303 struct file *file = iocb->ki_filp; 2304 struct address_space * mapping = file->f_mapping; 2305 size_t ocount; /* original count */ 2306 size_t count; /* after file limit checks */ 2307 struct inode *inode = mapping->host; 2308 loff_t pos; 2309 ssize_t written; 2310 ssize_t err; 2311 2312 ocount = 0; 2313 err = generic_segment_checks(iov, &nr_segs, &ocount, VERIFY_READ); 2314 if (err) 2315 return err; 2316 2317 count = ocount; 2318 pos = *ppos; 2319 2320 vfs_check_frozen(inode->i_sb, SB_FREEZE_WRITE); 2321 2322 /* We can write back this queue in page reclaim */ 2323 current->backing_dev_info = mapping->backing_dev_info; 2324 written = 0; 2325 2326 err = generic_write_checks(file, &pos, &count, S_ISBLK(inode->i_mode)); 2327 if (err) 2328 goto out; 2329 2330 if (count == 0) 2331 goto out; 2332 2333 err = file_remove_suid(file); 2334 if (err) 2335 goto out; 2336 2337 file_update_time(file); 2338 2339 /* coalesce the iovecs and go direct-to-BIO for O_DIRECT */ 2340 if (unlikely(file->f_flags & O_DIRECT)) { 2341 loff_t endbyte; 2342 ssize_t written_buffered; 2343 2344 written = generic_file_direct_write(iocb, iov, &nr_segs, pos, 2345 ppos, count, ocount); 2346 if (written < 0 || written == count) 2347 goto out; 2348 /* 2349 * direct-io write to a hole: fall through to buffered I/O 2350 * for completing the rest of the request. 2351 */ 2352 pos += written; 2353 count -= written; 2354 written_buffered = generic_file_buffered_write(iocb, iov, 2355 nr_segs, pos, ppos, count, 2356 written); 2357 /* 2358 * If generic_file_buffered_write() retuned a synchronous error 2359 * then we want to return the number of bytes which were 2360 * direct-written, or the error code if that was zero. Note 2361 * that this differs from normal direct-io semantics, which 2362 * will return -EFOO even if some bytes were written. 2363 */ 2364 if (written_buffered < 0) { 2365 err = written_buffered; 2366 goto out; 2367 } 2368 2369 /* 2370 * We need to ensure that the page cache pages are written to 2371 * disk and invalidated to preserve the expected O_DIRECT 2372 * semantics. 2373 */ 2374 endbyte = pos + written_buffered - written - 1; 2375 err = do_sync_mapping_range(file->f_mapping, pos, endbyte, 2376 SYNC_FILE_RANGE_WAIT_BEFORE| 2377 SYNC_FILE_RANGE_WRITE| 2378 SYNC_FILE_RANGE_WAIT_AFTER); 2379 if (err == 0) { 2380 written = written_buffered; 2381 invalidate_mapping_pages(mapping, 2382 pos >> PAGE_CACHE_SHIFT, 2383 endbyte >> PAGE_CACHE_SHIFT); 2384 } else { 2385 /* 2386 * We don't know how much we wrote, so just return 2387 * the number of bytes which were direct-written 2388 */ 2389 } 2390 } else { 2391 written = generic_file_buffered_write(iocb, iov, nr_segs, 2392 pos, ppos, count, written); 2393 } 2394out: 2395 current->backing_dev_info = NULL; 2396 return written ? written : err; 2397} 2398EXPORT_SYMBOL(__generic_file_aio_write); 2399 2400/** 2401 * generic_file_aio_write - write data to a file 2402 * @iocb: IO state structure 2403 * @iov: vector with data to write 2404 * @nr_segs: number of segments in the vector 2405 * @pos: position in file where to write 2406 * 2407 * This is a wrapper around __generic_file_aio_write() to be used by most 2408 * filesystems. It takes care of syncing the file in case of O_SYNC file 2409 * and acquires i_mutex as needed. 2410 */ 2411ssize_t generic_file_aio_write(struct kiocb *iocb, const struct iovec *iov, 2412 unsigned long nr_segs, loff_t pos) 2413{ 2414 struct file *file = iocb->ki_filp; 2415 struct inode *inode = file->f_mapping->host; 2416 ssize_t ret; 2417 2418 BUG_ON(iocb->ki_pos != pos); 2419 2420 mutex_lock(&inode->i_mutex); 2421 ret = __generic_file_aio_write(iocb, iov, nr_segs, &iocb->ki_pos); 2422 mutex_unlock(&inode->i_mutex); 2423 2424 if (ret > 0 || ret == -EIOCBQUEUED) { 2425 ssize_t err; 2426 2427 err = generic_write_sync(file, pos, ret); 2428 if (err < 0 && ret > 0) 2429 ret = err; 2430 } 2431 return ret; 2432} 2433EXPORT_SYMBOL(generic_file_aio_write); 2434 2435/** 2436 * try_to_release_page() - release old fs-specific metadata on a page 2437 * 2438 * @page: the page which the kernel is trying to free 2439 * @gfp_mask: memory allocation flags (and I/O mode) 2440 * 2441 * The address_space is to try to release any data against the page 2442 * (presumably at page->private). If the release was successful, return `1'. 2443 * Otherwise return zero. 2444 * 2445 * This may also be called if PG_fscache is set on a page, indicating that the 2446 * page is known to the local caching routines. 2447 * 2448 * The @gfp_mask argument specifies whether I/O may be performed to release 2449 * this page (__GFP_IO), and whether the call may block (__GFP_WAIT & __GFP_FS). 2450 * 2451 */ 2452int try_to_release_page(struct page *page, gfp_t gfp_mask) 2453{ 2454 struct address_space * const mapping = page->mapping; 2455 2456 BUG_ON(!PageLocked(page)); 2457 if (PageWriteback(page)) 2458 return 0; 2459 2460 if (mapping && mapping->a_ops->releasepage) 2461 return mapping->a_ops->releasepage(page, gfp_mask); 2462 return try_to_free_buffers(page); 2463} 2464 2465EXPORT_SYMBOL(try_to_release_page); 2466