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/export.h> 13 #include <linux/compiler.h> 14 #include <linux/fs.h> 15 #include <linux/uaccess.h> 16 #include <linux/aio.h> 17 #include <linux/capability.h> 18 #include <linux/kernel_stat.h> 19 #include <linux/gfp.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/cpuset.h> 33 #include <linux/hardirq.h> /* for BUG_ON(!in_atomic()) only */ 34 #include <linux/memcontrol.h> 35 #include <linux/cleancache.h> 36 #include "internal.h" 37 38 /* 39 * FIXME: remove all knowledge of the buffer layer from the core VM 40 */ 41 #include <linux/buffer_head.h> /* for try_to_free_buffers */ 42 43 #include <asm/mman.h> 44 45 /* 46 * Shared mappings implemented 30.11.1994. It's not fully working yet, 47 * though. 48 * 49 * Shared mappings now work. 15.8.1995 Bruno. 50 * 51 * finished 'unifying' the page and buffer cache and SMP-threaded the 52 * page-cache, 21.05.1999, Ingo Molnar <mingo@redhat.com> 53 * 54 * SMP-threaded pagemap-LRU 1999, Andrea Arcangeli <andrea@suse.de> 55 */ 56 57 /* 58 * Lock ordering: 59 * 60 * ->i_mmap_mutex (truncate_pagecache) 61 * ->private_lock (__free_pte->__set_page_dirty_buffers) 62 * ->swap_lock (exclusive_swap_page, others) 63 * ->mapping->tree_lock 64 * 65 * ->i_mutex 66 * ->i_mmap_mutex (truncate->unmap_mapping_range) 67 * 68 * ->mmap_sem 69 * ->i_mmap_mutex 70 * ->page_table_lock or pte_lock (various, mainly in memory.c) 71 * ->mapping->tree_lock (arch-dependent flush_dcache_mmap_lock) 72 * 73 * ->mmap_sem 74 * ->lock_page (access_process_vm) 75 * 76 * ->i_mutex (generic_file_buffered_write) 77 * ->mmap_sem (fault_in_pages_readable->do_page_fault) 78 * 79 * bdi->wb.list_lock 80 * sb_lock (fs/fs-writeback.c) 81 * ->mapping->tree_lock (__sync_single_inode) 82 * 83 * ->i_mmap_mutex 84 * ->anon_vma.lock (vma_adjust) 85 * 86 * ->anon_vma.lock 87 * ->page_table_lock or pte_lock (anon_vma_prepare and various) 88 * 89 * ->page_table_lock or pte_lock 90 * ->swap_lock (try_to_unmap_one) 91 * ->private_lock (try_to_unmap_one) 92 * ->tree_lock (try_to_unmap_one) 93 * ->zone.lru_lock (follow_page->mark_page_accessed) 94 * ->zone.lru_lock (check_pte_range->isolate_lru_page) 95 * ->private_lock (page_remove_rmap->set_page_dirty) 96 * ->tree_lock (page_remove_rmap->set_page_dirty) 97 * bdi.wb->list_lock (page_remove_rmap->set_page_dirty) 98 * ->inode->i_lock (page_remove_rmap->set_page_dirty) 99 * bdi.wb->list_lock (zap_pte_range->set_page_dirty) 100 * ->inode->i_lock (zap_pte_range->set_page_dirty) 101 * ->private_lock (zap_pte_range->__set_page_dirty_buffers) 102 * 103 * ->i_mmap_mutex 104 * ->tasklist_lock (memory_failure, collect_procs_ao) 105 */ 106 107 /* 108 * Delete a page from the page cache and free it. Caller has to make 109 * sure the page is locked and that nobody else uses it - or that usage 110 * is safe. The caller must hold the mapping's tree_lock. 111 */ 112 void __delete_from_page_cache(struct page *page) 113 { 114 struct address_space *mapping = page->mapping; 115 116 /* 117 * if we're uptodate, flush out into the cleancache, otherwise 118 * invalidate any existing cleancache entries. We can't leave 119 * stale data around in the cleancache once our page is gone 120 */ 121 if (PageUptodate(page) && PageMappedToDisk(page)) 122 cleancache_put_page(page); 123 else 124 cleancache_invalidate_page(mapping, page); 125 126 radix_tree_delete(&mapping->page_tree, page->index); 127 page->mapping = NULL; 128 /* Leave page->index set: truncation lookup relies upon it */ 129 mapping->nrpages--; 130 __dec_zone_page_state(page, NR_FILE_PAGES); 131 if (PageSwapBacked(page)) 132 __dec_zone_page_state(page, NR_SHMEM); 133 BUG_ON(page_mapped(page)); 134 135 /* 136 * Some filesystems seem to re-dirty the page even after 137 * the VM has canceled the dirty bit (eg ext3 journaling). 138 * 139 * Fix it up by doing a final dirty accounting check after 140 * having removed the page entirely. 141 */ 142 if (PageDirty(page) && mapping_cap_account_dirty(mapping)) { 143 dec_zone_page_state(page, NR_FILE_DIRTY); 144 dec_bdi_stat(mapping->backing_dev_info, BDI_RECLAIMABLE); 145 } 146 } 147 148 /** 149 * delete_from_page_cache - delete page from page cache 150 * @page: the page which the kernel is trying to remove from page cache 151 * 152 * This must be called only on pages that have been verified to be in the page 153 * cache and locked. It will never put the page into the free list, the caller 154 * has a reference on the page. 155 */ 156 void delete_from_page_cache(struct page *page) 157 { 158 struct address_space *mapping = page->mapping; 159 void (*freepage)(struct page *); 160 161 BUG_ON(!PageLocked(page)); 162 163 freepage = mapping->a_ops->freepage; 164 spin_lock_irq(&mapping->tree_lock); 165 __delete_from_page_cache(page); 166 spin_unlock_irq(&mapping->tree_lock); 167 mem_cgroup_uncharge_cache_page(page); 168 169 if (freepage) 170 freepage(page); 171 page_cache_release(page); 172 } 173 EXPORT_SYMBOL(delete_from_page_cache); 174 175 static int sleep_on_page(void *word) 176 { 177 io_schedule(); 178 return 0; 179 } 180 181 static int sleep_on_page_killable(void *word) 182 { 183 sleep_on_page(word); 184 return fatal_signal_pending(current) ? -EINTR : 0; 185 } 186 187 /** 188 * __filemap_fdatawrite_range - start writeback on mapping dirty pages in range 189 * @mapping: address space structure to write 190 * @start: offset in bytes where the range starts 191 * @end: offset in bytes where the range ends (inclusive) 192 * @sync_mode: enable synchronous operation 193 * 194 * Start writeback against all of a mapping's dirty pages that lie 195 * within the byte offsets <start, end> inclusive. 196 * 197 * If sync_mode is WB_SYNC_ALL then this is a "data integrity" operation, as 198 * opposed to a regular memory cleansing writeback. The difference between 199 * these two operations is that if a dirty page/buffer is encountered, it must 200 * be waited upon, and not just skipped over. 201 */ 202 int __filemap_fdatawrite_range(struct address_space *mapping, loff_t start, 203 loff_t end, int sync_mode) 204 { 205 int ret; 206 struct writeback_control wbc = { 207 .sync_mode = sync_mode, 208 .nr_to_write = LONG_MAX, 209 .range_start = start, 210 .range_end = end, 211 }; 212 213 if (!mapping_cap_writeback_dirty(mapping)) 214 return 0; 215 216 ret = do_writepages(mapping, &wbc); 217 return ret; 218 } 219 220 static inline int __filemap_fdatawrite(struct address_space *mapping, 221 int sync_mode) 222 { 223 return __filemap_fdatawrite_range(mapping, 0, LLONG_MAX, sync_mode); 224 } 225 226 int filemap_fdatawrite(struct address_space *mapping) 227 { 228 return __filemap_fdatawrite(mapping, WB_SYNC_ALL); 229 } 230 EXPORT_SYMBOL(filemap_fdatawrite); 231 232 int filemap_fdatawrite_range(struct address_space *mapping, loff_t start, 233 loff_t end) 234 { 235 return __filemap_fdatawrite_range(mapping, start, end, WB_SYNC_ALL); 236 } 237 EXPORT_SYMBOL(filemap_fdatawrite_range); 238 239 /** 240 * filemap_flush - mostly a non-blocking flush 241 * @mapping: target address_space 242 * 243 * This is a mostly non-blocking flush. Not suitable for data-integrity 244 * purposes - I/O may not be started against all dirty pages. 245 */ 246 int filemap_flush(struct address_space *mapping) 247 { 248 return __filemap_fdatawrite(mapping, WB_SYNC_NONE); 249 } 250 EXPORT_SYMBOL(filemap_flush); 251 252 /** 253 * filemap_fdatawait_range - wait for writeback to complete 254 * @mapping: address space structure to wait for 255 * @start_byte: offset in bytes where the range starts 256 * @end_byte: offset in bytes where the range ends (inclusive) 257 * 258 * Walk the list of under-writeback pages of the given address space 259 * in the given range and wait for all of them. 260 */ 261 int filemap_fdatawait_range(struct address_space *mapping, loff_t start_byte, 262 loff_t end_byte) 263 { 264 pgoff_t index = start_byte >> PAGE_CACHE_SHIFT; 265 pgoff_t end = end_byte >> PAGE_CACHE_SHIFT; 266 struct pagevec pvec; 267 int nr_pages; 268 int ret = 0; 269 270 if (end_byte < start_byte) 271 return 0; 272 273 pagevec_init(&pvec, 0); 274 while ((index <= end) && 275 (nr_pages = pagevec_lookup_tag(&pvec, mapping, &index, 276 PAGECACHE_TAG_WRITEBACK, 277 min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1)) != 0) { 278 unsigned i; 279 280 for (i = 0; i < nr_pages; i++) { 281 struct page *page = pvec.pages[i]; 282 283 /* until radix tree lookup accepts end_index */ 284 if (page->index > end) 285 continue; 286 287 wait_on_page_writeback(page); 288 if (TestClearPageError(page)) 289 ret = -EIO; 290 } 291 pagevec_release(&pvec); 292 cond_resched(); 293 } 294 295 /* Check for outstanding write errors */ 296 if (test_and_clear_bit(AS_ENOSPC, &mapping->flags)) 297 ret = -ENOSPC; 298 if (test_and_clear_bit(AS_EIO, &mapping->flags)) 299 ret = -EIO; 300 301 return ret; 302 } 303 EXPORT_SYMBOL(filemap_fdatawait_range); 304 305 /** 306 * filemap_fdatawait - wait for all under-writeback pages to complete 307 * @mapping: address space structure to wait for 308 * 309 * Walk the list of under-writeback pages of the given address space 310 * and wait for all of them. 311 */ 312 int filemap_fdatawait(struct address_space *mapping) 313 { 314 loff_t i_size = i_size_read(mapping->host); 315 316 if (i_size == 0) 317 return 0; 318 319 return filemap_fdatawait_range(mapping, 0, i_size - 1); 320 } 321 EXPORT_SYMBOL(filemap_fdatawait); 322 323 int filemap_write_and_wait(struct address_space *mapping) 324 { 325 int err = 0; 326 327 if (mapping->nrpages) { 328 err = filemap_fdatawrite(mapping); 329 /* 330 * Even if the above returned error, the pages may be 331 * written partially (e.g. -ENOSPC), so we wait for it. 332 * But the -EIO is special case, it may indicate the worst 333 * thing (e.g. bug) happened, so we avoid waiting for it. 334 */ 335 if (err != -EIO) { 336 int err2 = filemap_fdatawait(mapping); 337 if (!err) 338 err = err2; 339 } 340 } 341 return err; 342 } 343 EXPORT_SYMBOL(filemap_write_and_wait); 344 345 /** 346 * filemap_write_and_wait_range - write out & wait on a file range 347 * @mapping: the address_space for the pages 348 * @lstart: offset in bytes where the range starts 349 * @lend: offset in bytes where the range ends (inclusive) 350 * 351 * Write out and wait upon file offsets lstart->lend, inclusive. 352 * 353 * Note that `lend' is inclusive (describes the last byte to be written) so 354 * that this function can be used to write to the very end-of-file (end = -1). 355 */ 356 int filemap_write_and_wait_range(struct address_space *mapping, 357 loff_t lstart, loff_t lend) 358 { 359 int err = 0; 360 361 if (mapping->nrpages) { 362 err = __filemap_fdatawrite_range(mapping, lstart, lend, 363 WB_SYNC_ALL); 364 /* See comment of filemap_write_and_wait() */ 365 if (err != -EIO) { 366 int err2 = filemap_fdatawait_range(mapping, 367 lstart, lend); 368 if (!err) 369 err = err2; 370 } 371 } 372 return err; 373 } 374 EXPORT_SYMBOL(filemap_write_and_wait_range); 375 376 /** 377 * replace_page_cache_page - replace a pagecache page with a new one 378 * @old: page to be replaced 379 * @new: page to replace with 380 * @gfp_mask: allocation mode 381 * 382 * This function replaces a page in the pagecache with a new one. On 383 * success it acquires the pagecache reference for the new page and 384 * drops it for the old page. Both the old and new pages must be 385 * locked. This function does not add the new page to the LRU, the 386 * caller must do that. 387 * 388 * The remove + add is atomic. The only way this function can fail is 389 * memory allocation failure. 390 */ 391 int replace_page_cache_page(struct page *old, struct page *new, gfp_t gfp_mask) 392 { 393 int error; 394 395 VM_BUG_ON(!PageLocked(old)); 396 VM_BUG_ON(!PageLocked(new)); 397 VM_BUG_ON(new->mapping); 398 399 error = radix_tree_preload(gfp_mask & ~__GFP_HIGHMEM); 400 if (!error) { 401 struct address_space *mapping = old->mapping; 402 void (*freepage)(struct page *); 403 404 pgoff_t offset = old->index; 405 freepage = mapping->a_ops->freepage; 406 407 page_cache_get(new); 408 new->mapping = mapping; 409 new->index = offset; 410 411 spin_lock_irq(&mapping->tree_lock); 412 __delete_from_page_cache(old); 413 error = radix_tree_insert(&mapping->page_tree, offset, new); 414 BUG_ON(error); 415 mapping->nrpages++; 416 __inc_zone_page_state(new, NR_FILE_PAGES); 417 if (PageSwapBacked(new)) 418 __inc_zone_page_state(new, NR_SHMEM); 419 spin_unlock_irq(&mapping->tree_lock); 420 /* mem_cgroup codes must not be called under tree_lock */ 421 mem_cgroup_replace_page_cache(old, new); 422 radix_tree_preload_end(); 423 if (freepage) 424 freepage(old); 425 page_cache_release(old); 426 } 427 428 return error; 429 } 430 EXPORT_SYMBOL_GPL(replace_page_cache_page); 431 432 /** 433 * add_to_page_cache_locked - add a locked page to the pagecache 434 * @page: page to add 435 * @mapping: the page's address_space 436 * @offset: page index 437 * @gfp_mask: page allocation mode 438 * 439 * This function is used to add a page to the pagecache. It must be locked. 440 * This function does not add the page to the LRU. The caller must do that. 441 */ 442 int add_to_page_cache_locked(struct page *page, struct address_space *mapping, 443 pgoff_t offset, gfp_t gfp_mask) 444 { 445 int error; 446 447 VM_BUG_ON(!PageLocked(page)); 448 VM_BUG_ON(PageSwapBacked(page)); 449 450 error = mem_cgroup_cache_charge(page, current->mm, 451 gfp_mask & GFP_RECLAIM_MASK); 452 if (error) 453 goto out; 454 455 error = radix_tree_preload(gfp_mask & ~__GFP_HIGHMEM); 456 if (error == 0) { 457 page_cache_get(page); 458 page->mapping = mapping; 459 page->index = offset; 460 461 spin_lock_irq(&mapping->tree_lock); 462 error = radix_tree_insert(&mapping->page_tree, offset, page); 463 if (likely(!error)) { 464 mapping->nrpages++; 465 __inc_zone_page_state(page, NR_FILE_PAGES); 466 spin_unlock_irq(&mapping->tree_lock); 467 } else { 468 page->mapping = NULL; 469 /* Leave page->index set: truncation relies upon it */ 470 spin_unlock_irq(&mapping->tree_lock); 471 mem_cgroup_uncharge_cache_page(page); 472 page_cache_release(page); 473 } 474 radix_tree_preload_end(); 475 } else 476 mem_cgroup_uncharge_cache_page(page); 477 out: 478 return error; 479 } 480 EXPORT_SYMBOL(add_to_page_cache_locked); 481 482 int add_to_page_cache_lru(struct page *page, struct address_space *mapping, 483 pgoff_t offset, gfp_t gfp_mask) 484 { 485 int ret; 486 487 ret = add_to_page_cache(page, mapping, offset, gfp_mask); 488 if (ret == 0) 489 lru_cache_add_file(page); 490 return ret; 491 } 492 EXPORT_SYMBOL_GPL(add_to_page_cache_lru); 493 494 #ifdef CONFIG_NUMA 495 struct page *__page_cache_alloc(gfp_t gfp) 496 { 497 int n; 498 struct page *page; 499 500 if (cpuset_do_page_mem_spread()) { 501 unsigned int cpuset_mems_cookie; 502 do { 503 cpuset_mems_cookie = get_mems_allowed(); 504 n = cpuset_mem_spread_node(); 505 page = alloc_pages_exact_node(n, gfp, 0); 506 } while (!put_mems_allowed(cpuset_mems_cookie) && !page); 507 508 return page; 509 } 510 return alloc_pages(gfp, 0); 511 } 512 EXPORT_SYMBOL(__page_cache_alloc); 513 #endif 514 515 /* 516 * In order to wait for pages to become available there must be 517 * waitqueues associated with pages. By using a hash table of 518 * waitqueues where the bucket discipline is to maintain all 519 * waiters on the same queue and wake all when any of the pages 520 * become available, and for the woken contexts to check to be 521 * sure the appropriate page became available, this saves space 522 * at a cost of "thundering herd" phenomena during rare hash 523 * collisions. 524 */ 525 static wait_queue_head_t *page_waitqueue(struct page *page) 526 { 527 const struct zone *zone = page_zone(page); 528 529 return &zone->wait_table[hash_ptr(page, zone->wait_table_bits)]; 530 } 531 532 static inline void wake_up_page(struct page *page, int bit) 533 { 534 __wake_up_bit(page_waitqueue(page), &page->flags, bit); 535 } 536 537 void wait_on_page_bit(struct page *page, int bit_nr) 538 { 539 DEFINE_WAIT_BIT(wait, &page->flags, bit_nr); 540 541 if (test_bit(bit_nr, &page->flags)) 542 __wait_on_bit(page_waitqueue(page), &wait, sleep_on_page, 543 TASK_UNINTERRUPTIBLE); 544 } 545 EXPORT_SYMBOL(wait_on_page_bit); 546 547 int wait_on_page_bit_killable(struct page *page, int bit_nr) 548 { 549 DEFINE_WAIT_BIT(wait, &page->flags, bit_nr); 550 551 if (!test_bit(bit_nr, &page->flags)) 552 return 0; 553 554 return __wait_on_bit(page_waitqueue(page), &wait, 555 sleep_on_page_killable, TASK_KILLABLE); 556 } 557 558 /** 559 * add_page_wait_queue - Add an arbitrary waiter to a page's wait queue 560 * @page: Page defining the wait queue of interest 561 * @waiter: Waiter to add to the queue 562 * 563 * Add an arbitrary @waiter to the wait queue for the nominated @page. 564 */ 565 void add_page_wait_queue(struct page *page, wait_queue_t *waiter) 566 { 567 wait_queue_head_t *q = page_waitqueue(page); 568 unsigned long flags; 569 570 spin_lock_irqsave(&q->lock, flags); 571 __add_wait_queue(q, waiter); 572 spin_unlock_irqrestore(&q->lock, flags); 573 } 574 EXPORT_SYMBOL_GPL(add_page_wait_queue); 575 576 /** 577 * unlock_page - unlock a locked page 578 * @page: the page 579 * 580 * Unlocks the page and wakes up sleepers in ___wait_on_page_locked(). 581 * Also wakes sleepers in wait_on_page_writeback() because the wakeup 582 * mechananism between PageLocked pages and PageWriteback pages is shared. 583 * But that's OK - sleepers in wait_on_page_writeback() just go back to sleep. 584 * 585 * The mb is necessary to enforce ordering between the clear_bit and the read 586 * of the waitqueue (to avoid SMP races with a parallel wait_on_page_locked()). 587 */ 588 void unlock_page(struct page *page) 589 { 590 VM_BUG_ON(!PageLocked(page)); 591 clear_bit_unlock(PG_locked, &page->flags); 592 smp_mb__after_clear_bit(); 593 wake_up_page(page, PG_locked); 594 } 595 EXPORT_SYMBOL(unlock_page); 596 597 /** 598 * end_page_writeback - end writeback against a page 599 * @page: the page 600 */ 601 void end_page_writeback(struct page *page) 602 { 603 if (TestClearPageReclaim(page)) 604 rotate_reclaimable_page(page); 605 606 if (!test_clear_page_writeback(page)) 607 BUG(); 608 609 smp_mb__after_clear_bit(); 610 wake_up_page(page, PG_writeback); 611 } 612 EXPORT_SYMBOL(end_page_writeback); 613 614 /** 615 * __lock_page - get a lock on the page, assuming we need to sleep to get it 616 * @page: the page to lock 617 */ 618 void __lock_page(struct page *page) 619 { 620 DEFINE_WAIT_BIT(wait, &page->flags, PG_locked); 621 622 __wait_on_bit_lock(page_waitqueue(page), &wait, sleep_on_page, 623 TASK_UNINTERRUPTIBLE); 624 } 625 EXPORT_SYMBOL(__lock_page); 626 627 int __lock_page_killable(struct page *page) 628 { 629 DEFINE_WAIT_BIT(wait, &page->flags, PG_locked); 630 631 return __wait_on_bit_lock(page_waitqueue(page), &wait, 632 sleep_on_page_killable, TASK_KILLABLE); 633 } 634 EXPORT_SYMBOL_GPL(__lock_page_killable); 635 636 int __lock_page_or_retry(struct page *page, struct mm_struct *mm, 637 unsigned int flags) 638 { 639 if (flags & FAULT_FLAG_ALLOW_RETRY) { 640 /* 641 * CAUTION! In this case, mmap_sem is not released 642 * even though return 0. 643 */ 644 if (flags & FAULT_FLAG_RETRY_NOWAIT) 645 return 0; 646 647 up_read(&mm->mmap_sem); 648 if (flags & FAULT_FLAG_KILLABLE) 649 wait_on_page_locked_killable(page); 650 else 651 wait_on_page_locked(page); 652 return 0; 653 } else { 654 if (flags & FAULT_FLAG_KILLABLE) { 655 int ret; 656 657 ret = __lock_page_killable(page); 658 if (ret) { 659 up_read(&mm->mmap_sem); 660 return 0; 661 } 662 } else 663 __lock_page(page); 664 return 1; 665 } 666 } 667 668 /** 669 * find_get_page - find and get a page reference 670 * @mapping: the address_space to search 671 * @offset: the page index 672 * 673 * Is there a pagecache struct page at the given (mapping, offset) tuple? 674 * If yes, increment its refcount and return it; if no, return NULL. 675 */ 676 struct page *find_get_page(struct address_space *mapping, pgoff_t offset) 677 { 678 void **pagep; 679 struct page *page; 680 681 rcu_read_lock(); 682 repeat: 683 page = NULL; 684 pagep = radix_tree_lookup_slot(&mapping->page_tree, offset); 685 if (pagep) { 686 page = radix_tree_deref_slot(pagep); 687 if (unlikely(!page)) 688 goto out; 689 if (radix_tree_exception(page)) { 690 if (radix_tree_deref_retry(page)) 691 goto repeat; 692 /* 693 * Otherwise, shmem/tmpfs must be storing a swap entry 694 * here as an exceptional entry: so return it without 695 * attempting to raise page count. 696 */ 697 goto out; 698 } 699 if (!page_cache_get_speculative(page)) 700 goto repeat; 701 702 /* 703 * Has the page moved? 704 * This is part of the lockless pagecache protocol. See 705 * include/linux/pagemap.h for details. 706 */ 707 if (unlikely(page != *pagep)) { 708 page_cache_release(page); 709 goto repeat; 710 } 711 } 712 out: 713 rcu_read_unlock(); 714 715 return page; 716 } 717 EXPORT_SYMBOL(find_get_page); 718 719 /** 720 * find_lock_page - locate, pin and lock a pagecache page 721 * @mapping: the address_space to search 722 * @offset: the page index 723 * 724 * Locates the desired pagecache page, locks it, increments its reference 725 * count and returns its address. 726 * 727 * Returns zero if the page was not present. find_lock_page() may sleep. 728 */ 729 struct page *find_lock_page(struct address_space *mapping, pgoff_t offset) 730 { 731 struct page *page; 732 733 repeat: 734 page = find_get_page(mapping, offset); 735 if (page && !radix_tree_exception(page)) { 736 lock_page(page); 737 /* Has the page been truncated? */ 738 if (unlikely(page->mapping != mapping)) { 739 unlock_page(page); 740 page_cache_release(page); 741 goto repeat; 742 } 743 VM_BUG_ON(page->index != offset); 744 } 745 return page; 746 } 747 EXPORT_SYMBOL(find_lock_page); 748 749 /** 750 * find_or_create_page - locate or add a pagecache page 751 * @mapping: the page's address_space 752 * @index: the page's index into the mapping 753 * @gfp_mask: page allocation mode 754 * 755 * Locates a page in the pagecache. If the page is not present, a new page 756 * is allocated using @gfp_mask and is added to the pagecache and to the VM's 757 * LRU list. The returned page is locked and has its reference count 758 * incremented. 759 * 760 * find_or_create_page() may sleep, even if @gfp_flags specifies an atomic 761 * allocation! 762 * 763 * find_or_create_page() returns the desired page's address, or zero on 764 * memory exhaustion. 765 */ 766 struct page *find_or_create_page(struct address_space *mapping, 767 pgoff_t index, gfp_t gfp_mask) 768 { 769 struct page *page; 770 int err; 771 repeat: 772 page = find_lock_page(mapping, index); 773 if (!page) { 774 page = __page_cache_alloc(gfp_mask); 775 if (!page) 776 return NULL; 777 /* 778 * We want a regular kernel memory (not highmem or DMA etc) 779 * allocation for the radix tree nodes, but we need to honour 780 * the context-specific requirements the caller has asked for. 781 * GFP_RECLAIM_MASK collects those requirements. 782 */ 783 err = add_to_page_cache_lru(page, mapping, index, 784 (gfp_mask & GFP_RECLAIM_MASK)); 785 if (unlikely(err)) { 786 page_cache_release(page); 787 page = NULL; 788 if (err == -EEXIST) 789 goto repeat; 790 } 791 } 792 return page; 793 } 794 EXPORT_SYMBOL(find_or_create_page); 795 796 /** 797 * find_get_pages - gang pagecache lookup 798 * @mapping: The address_space to search 799 * @start: 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() will search for and return a group of up to 804 * @nr_pages pages in the mapping. The pages are placed at @pages. 805 * find_get_pages() takes a reference against the returned pages. 806 * 807 * The search returns a group of mapping-contiguous pages with ascending 808 * indexes. There may be holes in the indices due to not-present pages. 809 * 810 * find_get_pages() returns the number of pages which were found. 811 */ 812 unsigned find_get_pages(struct address_space *mapping, pgoff_t start, 813 unsigned int nr_pages, struct page **pages) 814 { 815 struct radix_tree_iter iter; 816 void **slot; 817 unsigned ret = 0; 818 819 if (unlikely(!nr_pages)) 820 return 0; 821 822 rcu_read_lock(); 823 restart: 824 radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, start) { 825 struct page *page; 826 repeat: 827 page = radix_tree_deref_slot(slot); 828 if (unlikely(!page)) 829 continue; 830 831 if (radix_tree_exception(page)) { 832 if (radix_tree_deref_retry(page)) { 833 /* 834 * Transient condition which can only trigger 835 * when entry at index 0 moves out of or back 836 * to root: none yet gotten, safe to restart. 837 */ 838 WARN_ON(iter.index); 839 goto restart; 840 } 841 /* 842 * Otherwise, shmem/tmpfs must be storing a swap entry 843 * here as an exceptional entry: so skip over it - 844 * we only reach this from invalidate_mapping_pages(). 845 */ 846 continue; 847 } 848 849 if (!page_cache_get_speculative(page)) 850 goto repeat; 851 852 /* Has the page moved? */ 853 if (unlikely(page != *slot)) { 854 page_cache_release(page); 855 goto repeat; 856 } 857 858 pages[ret] = page; 859 if (++ret == nr_pages) 860 break; 861 } 862 863 rcu_read_unlock(); 864 return ret; 865 } 866 867 /** 868 * find_get_pages_contig - gang contiguous pagecache lookup 869 * @mapping: The address_space to search 870 * @index: The starting page index 871 * @nr_pages: The maximum number of pages 872 * @pages: Where the resulting pages are placed 873 * 874 * find_get_pages_contig() works exactly like find_get_pages(), except 875 * that the returned number of pages are guaranteed to be contiguous. 876 * 877 * find_get_pages_contig() returns the number of pages which were found. 878 */ 879 unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t index, 880 unsigned int nr_pages, struct page **pages) 881 { 882 struct radix_tree_iter iter; 883 void **slot; 884 unsigned int ret = 0; 885 886 if (unlikely(!nr_pages)) 887 return 0; 888 889 rcu_read_lock(); 890 restart: 891 radix_tree_for_each_contig(slot, &mapping->page_tree, &iter, index) { 892 struct page *page; 893 repeat: 894 page = radix_tree_deref_slot(slot); 895 /* The hole, there no reason to continue */ 896 if (unlikely(!page)) 897 break; 898 899 if (radix_tree_exception(page)) { 900 if (radix_tree_deref_retry(page)) { 901 /* 902 * Transient condition which can only trigger 903 * when entry at index 0 moves out of or back 904 * to root: none yet gotten, safe to restart. 905 */ 906 goto restart; 907 } 908 /* 909 * Otherwise, shmem/tmpfs must be storing a swap entry 910 * here as an exceptional entry: so stop looking for 911 * contiguous pages. 912 */ 913 break; 914 } 915 916 if (!page_cache_get_speculative(page)) 917 goto repeat; 918 919 /* Has the page moved? */ 920 if (unlikely(page != *slot)) { 921 page_cache_release(page); 922 goto repeat; 923 } 924 925 /* 926 * must check mapping and index after taking the ref. 927 * otherwise we can get both false positives and false 928 * negatives, which is just confusing to the caller. 929 */ 930 if (page->mapping == NULL || page->index != iter.index) { 931 page_cache_release(page); 932 break; 933 } 934 935 pages[ret] = page; 936 if (++ret == nr_pages) 937 break; 938 } 939 rcu_read_unlock(); 940 return ret; 941 } 942 EXPORT_SYMBOL(find_get_pages_contig); 943 944 /** 945 * find_get_pages_tag - find and return pages that match @tag 946 * @mapping: the address_space to search 947 * @index: the starting page index 948 * @tag: the tag index 949 * @nr_pages: the maximum number of pages 950 * @pages: where the resulting pages are placed 951 * 952 * Like find_get_pages, except we only return pages which are tagged with 953 * @tag. We update @index to index the next page for the traversal. 954 */ 955 unsigned find_get_pages_tag(struct address_space *mapping, pgoff_t *index, 956 int tag, unsigned int nr_pages, struct page **pages) 957 { 958 struct radix_tree_iter iter; 959 void **slot; 960 unsigned ret = 0; 961 962 if (unlikely(!nr_pages)) 963 return 0; 964 965 rcu_read_lock(); 966 restart: 967 radix_tree_for_each_tagged(slot, &mapping->page_tree, 968 &iter, *index, tag) { 969 struct page *page; 970 repeat: 971 page = radix_tree_deref_slot(slot); 972 if (unlikely(!page)) 973 continue; 974 975 if (radix_tree_exception(page)) { 976 if (radix_tree_deref_retry(page)) { 977 /* 978 * Transient condition which can only trigger 979 * when entry at index 0 moves out of or back 980 * to root: none yet gotten, safe to restart. 981 */ 982 goto restart; 983 } 984 /* 985 * This function is never used on a shmem/tmpfs 986 * mapping, so a swap entry won't be found here. 987 */ 988 BUG(); 989 } 990 991 if (!page_cache_get_speculative(page)) 992 goto repeat; 993 994 /* Has the page moved? */ 995 if (unlikely(page != *slot)) { 996 page_cache_release(page); 997 goto repeat; 998 } 999 1000 pages[ret] = page; 1001 if (++ret == nr_pages) 1002 break; 1003 } 1004 1005 rcu_read_unlock(); 1006 1007 if (ret) 1008 *index = pages[ret - 1]->index + 1; 1009 1010 return ret; 1011 } 1012 EXPORT_SYMBOL(find_get_pages_tag); 1013 1014 /** 1015 * grab_cache_page_nowait - returns locked page at given index in given cache 1016 * @mapping: target address_space 1017 * @index: the page index 1018 * 1019 * Same as grab_cache_page(), but do not wait if the page is unavailable. 1020 * This is intended for speculative data generators, where the data can 1021 * be regenerated if the page couldn't be grabbed. This routine should 1022 * be safe to call while holding the lock for another page. 1023 * 1024 * Clear __GFP_FS when allocating the page to avoid recursion into the fs 1025 * and deadlock against the caller's locked page. 1026 */ 1027 struct page * 1028 grab_cache_page_nowait(struct address_space *mapping, pgoff_t index) 1029 { 1030 struct page *page = find_get_page(mapping, index); 1031 1032 if (page) { 1033 if (trylock_page(page)) 1034 return page; 1035 page_cache_release(page); 1036 return NULL; 1037 } 1038 page = __page_cache_alloc(mapping_gfp_mask(mapping) & ~__GFP_FS); 1039 if (page && add_to_page_cache_lru(page, mapping, index, GFP_NOFS)) { 1040 page_cache_release(page); 1041 page = NULL; 1042 } 1043 return page; 1044 } 1045 EXPORT_SYMBOL(grab_cache_page_nowait); 1046 1047 /* 1048 * CD/DVDs are error prone. When a medium error occurs, the driver may fail 1049 * a _large_ part of the i/o request. Imagine the worst scenario: 1050 * 1051 * ---R__________________________________________B__________ 1052 * ^ reading here ^ bad block(assume 4k) 1053 * 1054 * read(R) => miss => readahead(R...B) => media error => frustrating retries 1055 * => failing the whole request => read(R) => read(R+1) => 1056 * readahead(R+1...B+1) => bang => read(R+2) => read(R+3) => 1057 * readahead(R+3...B+2) => bang => read(R+3) => read(R+4) => 1058 * readahead(R+4...B+3) => bang => read(R+4) => read(R+5) => ...... 1059 * 1060 * It is going insane. Fix it by quickly scaling down the readahead size. 1061 */ 1062 static void shrink_readahead_size_eio(struct file *filp, 1063 struct file_ra_state *ra) 1064 { 1065 ra->ra_pages /= 4; 1066 } 1067 1068 /** 1069 * do_generic_file_read - generic file read routine 1070 * @filp: the file to read 1071 * @ppos: current file position 1072 * @desc: read_descriptor 1073 * @actor: read method 1074 * 1075 * This is a generic file read routine, and uses the 1076 * mapping->a_ops->readpage() function for the actual low-level stuff. 1077 * 1078 * This is really ugly. But the goto's actually try to clarify some 1079 * of the logic when it comes to error handling etc. 1080 */ 1081 static void do_generic_file_read(struct file *filp, loff_t *ppos, 1082 read_descriptor_t *desc, read_actor_t actor) 1083 { 1084 struct address_space *mapping = filp->f_mapping; 1085 struct inode *inode = mapping->host; 1086 struct file_ra_state *ra = &filp->f_ra; 1087 pgoff_t index; 1088 pgoff_t last_index; 1089 pgoff_t prev_index; 1090 unsigned long offset; /* offset into pagecache page */ 1091 unsigned int prev_offset; 1092 int error; 1093 1094 index = *ppos >> PAGE_CACHE_SHIFT; 1095 prev_index = ra->prev_pos >> PAGE_CACHE_SHIFT; 1096 prev_offset = ra->prev_pos & (PAGE_CACHE_SIZE-1); 1097 last_index = (*ppos + desc->count + PAGE_CACHE_SIZE-1) >> PAGE_CACHE_SHIFT; 1098 offset = *ppos & ~PAGE_CACHE_MASK; 1099 1100 for (;;) { 1101 struct page *page; 1102 pgoff_t end_index; 1103 loff_t isize; 1104 unsigned long nr, ret; 1105 1106 cond_resched(); 1107 find_page: 1108 page = find_get_page(mapping, index); 1109 if (!page) { 1110 page_cache_sync_readahead(mapping, 1111 ra, filp, 1112 index, last_index - index); 1113 page = find_get_page(mapping, index); 1114 if (unlikely(page == NULL)) 1115 goto no_cached_page; 1116 } 1117 if (PageReadahead(page)) { 1118 page_cache_async_readahead(mapping, 1119 ra, filp, page, 1120 index, last_index - index); 1121 } 1122 if (!PageUptodate(page)) { 1123 if (inode->i_blkbits == PAGE_CACHE_SHIFT || 1124 !mapping->a_ops->is_partially_uptodate) 1125 goto page_not_up_to_date; 1126 if (!trylock_page(page)) 1127 goto page_not_up_to_date; 1128 /* Did it get truncated before we got the lock? */ 1129 if (!page->mapping) 1130 goto page_not_up_to_date_locked; 1131 if (!mapping->a_ops->is_partially_uptodate(page, 1132 desc, offset)) 1133 goto page_not_up_to_date_locked; 1134 unlock_page(page); 1135 } 1136 page_ok: 1137 /* 1138 * i_size must be checked after we know the page is Uptodate. 1139 * 1140 * Checking i_size after the check allows us to calculate 1141 * the correct value for "nr", which means the zero-filled 1142 * part of the page is not copied back to userspace (unless 1143 * another truncate extends the file - this is desired though). 1144 */ 1145 1146 isize = i_size_read(inode); 1147 end_index = (isize - 1) >> PAGE_CACHE_SHIFT; 1148 if (unlikely(!isize || index > end_index)) { 1149 page_cache_release(page); 1150 goto out; 1151 } 1152 1153 /* nr is the maximum number of bytes to copy from this page */ 1154 nr = PAGE_CACHE_SIZE; 1155 if (index == end_index) { 1156 nr = ((isize - 1) & ~PAGE_CACHE_MASK) + 1; 1157 if (nr <= offset) { 1158 page_cache_release(page); 1159 goto out; 1160 } 1161 } 1162 nr = nr - offset; 1163 1164 /* If users can be writing to this page using arbitrary 1165 * virtual addresses, take care about potential aliasing 1166 * before reading the page on the kernel side. 1167 */ 1168 if (mapping_writably_mapped(mapping)) 1169 flush_dcache_page(page); 1170 1171 /* 1172 * When a sequential read accesses a page several times, 1173 * only mark it as accessed the first time. 1174 */ 1175 if (prev_index != index || offset != prev_offset) 1176 mark_page_accessed(page); 1177 prev_index = index; 1178 1179 /* 1180 * Ok, we have the page, and it's up-to-date, so 1181 * now we can copy it to user space... 1182 * 1183 * The actor routine returns how many bytes were actually used.. 1184 * NOTE! This may not be the same as how much of a user buffer 1185 * we filled up (we may be padding etc), so we can only update 1186 * "pos" here (the actor routine has to update the user buffer 1187 * pointers and the remaining count). 1188 */ 1189 ret = actor(desc, page, offset, nr); 1190 offset += ret; 1191 index += offset >> PAGE_CACHE_SHIFT; 1192 offset &= ~PAGE_CACHE_MASK; 1193 prev_offset = offset; 1194 1195 page_cache_release(page); 1196 if (ret == nr && desc->count) 1197 continue; 1198 goto out; 1199 1200 page_not_up_to_date: 1201 /* Get exclusive access to the page ... */ 1202 error = lock_page_killable(page); 1203 if (unlikely(error)) 1204 goto readpage_error; 1205 1206 page_not_up_to_date_locked: 1207 /* Did it get truncated before we got the lock? */ 1208 if (!page->mapping) { 1209 unlock_page(page); 1210 page_cache_release(page); 1211 continue; 1212 } 1213 1214 /* Did somebody else fill it already? */ 1215 if (PageUptodate(page)) { 1216 unlock_page(page); 1217 goto page_ok; 1218 } 1219 1220 readpage: 1221 /* 1222 * A previous I/O error may have been due to temporary 1223 * failures, eg. multipath errors. 1224 * PG_error will be set again if readpage fails. 1225 */ 1226 ClearPageError(page); 1227 /* Start the actual read. The read will unlock the page. */ 1228 error = mapping->a_ops->readpage(filp, page); 1229 1230 if (unlikely(error)) { 1231 if (error == AOP_TRUNCATED_PAGE) { 1232 page_cache_release(page); 1233 goto find_page; 1234 } 1235 goto readpage_error; 1236 } 1237 1238 if (!PageUptodate(page)) { 1239 error = lock_page_killable(page); 1240 if (unlikely(error)) 1241 goto readpage_error; 1242 if (!PageUptodate(page)) { 1243 if (page->mapping == NULL) { 1244 /* 1245 * invalidate_mapping_pages got it 1246 */ 1247 unlock_page(page); 1248 page_cache_release(page); 1249 goto find_page; 1250 } 1251 unlock_page(page); 1252 shrink_readahead_size_eio(filp, ra); 1253 error = -EIO; 1254 goto readpage_error; 1255 } 1256 unlock_page(page); 1257 } 1258 1259 goto page_ok; 1260 1261 readpage_error: 1262 /* UHHUH! A synchronous read error occurred. Report it */ 1263 desc->error = error; 1264 page_cache_release(page); 1265 goto out; 1266 1267 no_cached_page: 1268 /* 1269 * Ok, it wasn't cached, so we need to create a new 1270 * page.. 1271 */ 1272 page = page_cache_alloc_cold(mapping); 1273 if (!page) { 1274 desc->error = -ENOMEM; 1275 goto out; 1276 } 1277 error = add_to_page_cache_lru(page, mapping, 1278 index, GFP_KERNEL); 1279 if (error) { 1280 page_cache_release(page); 1281 if (error == -EEXIST) 1282 goto find_page; 1283 desc->error = error; 1284 goto out; 1285 } 1286 goto readpage; 1287 } 1288 1289 out: 1290 ra->prev_pos = prev_index; 1291 ra->prev_pos <<= PAGE_CACHE_SHIFT; 1292 ra->prev_pos |= prev_offset; 1293 1294 *ppos = ((loff_t)index << PAGE_CACHE_SHIFT) + offset; 1295 file_accessed(filp); 1296 } 1297 1298 int file_read_actor(read_descriptor_t *desc, struct page *page, 1299 unsigned long offset, unsigned long size) 1300 { 1301 char *kaddr; 1302 unsigned long left, count = desc->count; 1303 1304 if (size > count) 1305 size = count; 1306 1307 /* 1308 * Faults on the destination of a read are common, so do it before 1309 * taking the kmap. 1310 */ 1311 if (!fault_in_pages_writeable(desc->arg.buf, size)) { 1312 kaddr = kmap_atomic(page); 1313 left = __copy_to_user_inatomic(desc->arg.buf, 1314 kaddr + offset, size); 1315 kunmap_atomic(kaddr); 1316 if (left == 0) 1317 goto success; 1318 } 1319 1320 /* Do it the slow way */ 1321 kaddr = kmap(page); 1322 left = __copy_to_user(desc->arg.buf, kaddr + offset, size); 1323 kunmap(page); 1324 1325 if (left) { 1326 size -= left; 1327 desc->error = -EFAULT; 1328 } 1329 success: 1330 desc->count = count - size; 1331 desc->written += size; 1332 desc->arg.buf += size; 1333 return size; 1334 } 1335 1336 /* 1337 * Performs necessary checks before doing a write 1338 * @iov: io vector request 1339 * @nr_segs: number of segments in the iovec 1340 * @count: number of bytes to write 1341 * @access_flags: type of access: %VERIFY_READ or %VERIFY_WRITE 1342 * 1343 * Adjust number of segments and amount of bytes to write (nr_segs should be 1344 * properly initialized first). Returns appropriate error code that caller 1345 * should return or zero in case that write should be allowed. 1346 */ 1347 int generic_segment_checks(const struct iovec *iov, 1348 unsigned long *nr_segs, size_t *count, int access_flags) 1349 { 1350 unsigned long seg; 1351 size_t cnt = 0; 1352 for (seg = 0; seg < *nr_segs; seg++) { 1353 const struct iovec *iv = &iov[seg]; 1354 1355 /* 1356 * If any segment has a negative length, or the cumulative 1357 * length ever wraps negative then return -EINVAL. 1358 */ 1359 cnt += iv->iov_len; 1360 if (unlikely((ssize_t)(cnt|iv->iov_len) < 0)) 1361 return -EINVAL; 1362 if (access_ok(access_flags, iv->iov_base, iv->iov_len)) 1363 continue; 1364 if (seg == 0) 1365 return -EFAULT; 1366 *nr_segs = seg; 1367 cnt -= iv->iov_len; /* This segment is no good */ 1368 break; 1369 } 1370 *count = cnt; 1371 return 0; 1372 } 1373 EXPORT_SYMBOL(generic_segment_checks); 1374 1375 /** 1376 * generic_file_aio_read - generic filesystem read routine 1377 * @iocb: kernel I/O control block 1378 * @iov: io vector request 1379 * @nr_segs: number of segments in the iovec 1380 * @pos: current file position 1381 * 1382 * This is the "read()" routine for all filesystems 1383 * that can use the page cache directly. 1384 */ 1385 ssize_t 1386 generic_file_aio_read(struct kiocb *iocb, const struct iovec *iov, 1387 unsigned long nr_segs, loff_t pos) 1388 { 1389 struct file *filp = iocb->ki_filp; 1390 ssize_t retval; 1391 unsigned long seg = 0; 1392 size_t count; 1393 loff_t *ppos = &iocb->ki_pos; 1394 1395 count = 0; 1396 retval = generic_segment_checks(iov, &nr_segs, &count, VERIFY_WRITE); 1397 if (retval) 1398 return retval; 1399 1400 /* coalesce the iovecs and go direct-to-BIO for O_DIRECT */ 1401 if (filp->f_flags & O_DIRECT) { 1402 loff_t size; 1403 struct address_space *mapping; 1404 struct inode *inode; 1405 1406 mapping = filp->f_mapping; 1407 inode = mapping->host; 1408 if (!count) 1409 goto out; /* skip atime */ 1410 size = i_size_read(inode); 1411 if (pos < size) { 1412 retval = filemap_write_and_wait_range(mapping, pos, 1413 pos + iov_length(iov, nr_segs) - 1); 1414 if (!retval) { 1415 retval = mapping->a_ops->direct_IO(READ, iocb, 1416 iov, pos, nr_segs); 1417 } 1418 if (retval > 0) { 1419 *ppos = pos + retval; 1420 count -= retval; 1421 } 1422 1423 /* 1424 * Btrfs can have a short DIO read if we encounter 1425 * compressed extents, so if there was an error, or if 1426 * we've already read everything we wanted to, or if 1427 * there was a short read because we hit EOF, go ahead 1428 * and return. Otherwise fallthrough to buffered io for 1429 * the rest of the read. 1430 */ 1431 if (retval < 0 || !count || *ppos >= size) { 1432 file_accessed(filp); 1433 goto out; 1434 } 1435 } 1436 } 1437 1438 count = retval; 1439 for (seg = 0; seg < nr_segs; seg++) { 1440 read_descriptor_t desc; 1441 loff_t offset = 0; 1442 1443 /* 1444 * If we did a short DIO read we need to skip the section of the 1445 * iov that we've already read data into. 1446 */ 1447 if (count) { 1448 if (count > iov[seg].iov_len) { 1449 count -= iov[seg].iov_len; 1450 continue; 1451 } 1452 offset = count; 1453 count = 0; 1454 } 1455 1456 desc.written = 0; 1457 desc.arg.buf = iov[seg].iov_base + offset; 1458 desc.count = iov[seg].iov_len - offset; 1459 if (desc.count == 0) 1460 continue; 1461 desc.error = 0; 1462 do_generic_file_read(filp, ppos, &desc, file_read_actor); 1463 retval += desc.written; 1464 if (desc.error) { 1465 retval = retval ?: desc.error; 1466 break; 1467 } 1468 if (desc.count > 0) 1469 break; 1470 } 1471 out: 1472 return retval; 1473 } 1474 EXPORT_SYMBOL(generic_file_aio_read); 1475 1476 #ifdef CONFIG_MMU 1477 /** 1478 * page_cache_read - adds requested page to the page cache if not already there 1479 * @file: file to read 1480 * @offset: page index 1481 * 1482 * This adds the requested page to the page cache if it isn't already there, 1483 * and schedules an I/O to read in its contents from disk. 1484 */ 1485 static int page_cache_read(struct file *file, pgoff_t offset) 1486 { 1487 struct address_space *mapping = file->f_mapping; 1488 struct page *page; 1489 int ret; 1490 1491 do { 1492 page = page_cache_alloc_cold(mapping); 1493 if (!page) 1494 return -ENOMEM; 1495 1496 ret = add_to_page_cache_lru(page, mapping, offset, GFP_KERNEL); 1497 if (ret == 0) 1498 ret = mapping->a_ops->readpage(file, page); 1499 else if (ret == -EEXIST) 1500 ret = 0; /* losing race to add is OK */ 1501 1502 page_cache_release(page); 1503 1504 } while (ret == AOP_TRUNCATED_PAGE); 1505 1506 return ret; 1507 } 1508 1509 #define MMAP_LOTSAMISS (100) 1510 1511 /* 1512 * Synchronous readahead happens when we don't even find 1513 * a page in the page cache at all. 1514 */ 1515 static void do_sync_mmap_readahead(struct vm_area_struct *vma, 1516 struct file_ra_state *ra, 1517 struct file *file, 1518 pgoff_t offset) 1519 { 1520 unsigned long ra_pages; 1521 struct address_space *mapping = file->f_mapping; 1522 1523 /* If we don't want any read-ahead, don't bother */ 1524 if (VM_RandomReadHint(vma)) 1525 return; 1526 if (!ra->ra_pages) 1527 return; 1528 1529 if (VM_SequentialReadHint(vma)) { 1530 page_cache_sync_readahead(mapping, ra, file, offset, 1531 ra->ra_pages); 1532 return; 1533 } 1534 1535 /* Avoid banging the cache line if not needed */ 1536 if (ra->mmap_miss < MMAP_LOTSAMISS * 10) 1537 ra->mmap_miss++; 1538 1539 /* 1540 * Do we miss much more than hit in this file? If so, 1541 * stop bothering with read-ahead. It will only hurt. 1542 */ 1543 if (ra->mmap_miss > MMAP_LOTSAMISS) 1544 return; 1545 1546 /* 1547 * mmap read-around 1548 */ 1549 ra_pages = max_sane_readahead(ra->ra_pages); 1550 ra->start = max_t(long, 0, offset - ra_pages / 2); 1551 ra->size = ra_pages; 1552 ra->async_size = ra_pages / 4; 1553 ra_submit(ra, mapping, file); 1554 } 1555 1556 /* 1557 * Asynchronous readahead happens when we find the page and PG_readahead, 1558 * so we want to possibly extend the readahead further.. 1559 */ 1560 static void do_async_mmap_readahead(struct vm_area_struct *vma, 1561 struct file_ra_state *ra, 1562 struct file *file, 1563 struct page *page, 1564 pgoff_t offset) 1565 { 1566 struct address_space *mapping = file->f_mapping; 1567 1568 /* If we don't want any read-ahead, don't bother */ 1569 if (VM_RandomReadHint(vma)) 1570 return; 1571 if (ra->mmap_miss > 0) 1572 ra->mmap_miss--; 1573 if (PageReadahead(page)) 1574 page_cache_async_readahead(mapping, ra, file, 1575 page, offset, ra->ra_pages); 1576 } 1577 1578 /** 1579 * filemap_fault - read in file data for page fault handling 1580 * @vma: vma in which the fault was taken 1581 * @vmf: struct vm_fault containing details of the fault 1582 * 1583 * filemap_fault() is invoked via the vma operations vector for a 1584 * mapped memory region to read in file data during a page fault. 1585 * 1586 * The goto's are kind of ugly, but this streamlines the normal case of having 1587 * it in the page cache, and handles the special cases reasonably without 1588 * having a lot of duplicated code. 1589 */ 1590 int filemap_fault(struct vm_area_struct *vma, struct vm_fault *vmf) 1591 { 1592 int error; 1593 struct file *file = vma->vm_file; 1594 struct address_space *mapping = file->f_mapping; 1595 struct file_ra_state *ra = &file->f_ra; 1596 struct inode *inode = mapping->host; 1597 pgoff_t offset = vmf->pgoff; 1598 struct page *page; 1599 pgoff_t size; 1600 int ret = 0; 1601 1602 size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT; 1603 if (offset >= size) 1604 return VM_FAULT_SIGBUS; 1605 1606 /* 1607 * Do we have something in the page cache already? 1608 */ 1609 page = find_get_page(mapping, offset); 1610 if (likely(page) && !(vmf->flags & FAULT_FLAG_TRIED)) { 1611 /* 1612 * We found the page, so try async readahead before 1613 * waiting for the lock. 1614 */ 1615 do_async_mmap_readahead(vma, ra, file, page, offset); 1616 } else if (!page) { 1617 /* No page in the page cache at all */ 1618 do_sync_mmap_readahead(vma, ra, file, offset); 1619 count_vm_event(PGMAJFAULT); 1620 mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT); 1621 ret = VM_FAULT_MAJOR; 1622 retry_find: 1623 page = find_get_page(mapping, offset); 1624 if (!page) 1625 goto no_cached_page; 1626 } 1627 1628 if (!lock_page_or_retry(page, vma->vm_mm, vmf->flags)) { 1629 page_cache_release(page); 1630 return ret | VM_FAULT_RETRY; 1631 } 1632 1633 /* Did it get truncated? */ 1634 if (unlikely(page->mapping != mapping)) { 1635 unlock_page(page); 1636 put_page(page); 1637 goto retry_find; 1638 } 1639 VM_BUG_ON(page->index != offset); 1640 1641 /* 1642 * We have a locked page in the page cache, now we need to check 1643 * that it's up-to-date. If not, it is going to be due to an error. 1644 */ 1645 if (unlikely(!PageUptodate(page))) 1646 goto page_not_uptodate; 1647 1648 /* 1649 * Found the page and have a reference on it. 1650 * We must recheck i_size under page lock. 1651 */ 1652 size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT; 1653 if (unlikely(offset >= size)) { 1654 unlock_page(page); 1655 page_cache_release(page); 1656 return VM_FAULT_SIGBUS; 1657 } 1658 1659 vmf->page = page; 1660 return ret | VM_FAULT_LOCKED; 1661 1662 no_cached_page: 1663 /* 1664 * We're only likely to ever get here if MADV_RANDOM is in 1665 * effect. 1666 */ 1667 error = page_cache_read(file, offset); 1668 1669 /* 1670 * The page we want has now been added to the page cache. 1671 * In the unlikely event that someone removed it in the 1672 * meantime, we'll just come back here and read it again. 1673 */ 1674 if (error >= 0) 1675 goto retry_find; 1676 1677 /* 1678 * An error return from page_cache_read can result if the 1679 * system is low on memory, or a problem occurs while trying 1680 * to schedule I/O. 1681 */ 1682 if (error == -ENOMEM) 1683 return VM_FAULT_OOM; 1684 return VM_FAULT_SIGBUS; 1685 1686 page_not_uptodate: 1687 /* 1688 * Umm, take care of errors if the page isn't up-to-date. 1689 * Try to re-read it _once_. We do this synchronously, 1690 * because there really aren't any performance issues here 1691 * and we need to check for errors. 1692 */ 1693 ClearPageError(page); 1694 error = mapping->a_ops->readpage(file, page); 1695 if (!error) { 1696 wait_on_page_locked(page); 1697 if (!PageUptodate(page)) 1698 error = -EIO; 1699 } 1700 page_cache_release(page); 1701 1702 if (!error || error == AOP_TRUNCATED_PAGE) 1703 goto retry_find; 1704 1705 /* Things didn't work out. Return zero to tell the mm layer so. */ 1706 shrink_readahead_size_eio(file, ra); 1707 return VM_FAULT_SIGBUS; 1708 } 1709 EXPORT_SYMBOL(filemap_fault); 1710 1711 int filemap_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf) 1712 { 1713 struct page *page = vmf->page; 1714 struct inode *inode = vma->vm_file->f_path.dentry->d_inode; 1715 int ret = VM_FAULT_LOCKED; 1716 1717 sb_start_pagefault(inode->i_sb); 1718 file_update_time(vma->vm_file); 1719 lock_page(page); 1720 if (page->mapping != inode->i_mapping) { 1721 unlock_page(page); 1722 ret = VM_FAULT_NOPAGE; 1723 goto out; 1724 } 1725 /* 1726 * We mark the page dirty already here so that when freeze is in 1727 * progress, we are guaranteed that writeback during freezing will 1728 * see the dirty page and writeprotect it again. 1729 */ 1730 set_page_dirty(page); 1731 out: 1732 sb_end_pagefault(inode->i_sb); 1733 return ret; 1734 } 1735 EXPORT_SYMBOL(filemap_page_mkwrite); 1736 1737 const struct vm_operations_struct generic_file_vm_ops = { 1738 .fault = filemap_fault, 1739 .page_mkwrite = filemap_page_mkwrite, 1740 .remap_pages = generic_file_remap_pages, 1741 }; 1742 1743 /* This is used for a general mmap of a disk file */ 1744 1745 int generic_file_mmap(struct file * file, struct vm_area_struct * vma) 1746 { 1747 struct address_space *mapping = file->f_mapping; 1748 1749 if (!mapping->a_ops->readpage) 1750 return -ENOEXEC; 1751 file_accessed(file); 1752 vma->vm_ops = &generic_file_vm_ops; 1753 return 0; 1754 } 1755 1756 /* 1757 * This is for filesystems which do not implement ->writepage. 1758 */ 1759 int generic_file_readonly_mmap(struct file *file, struct vm_area_struct *vma) 1760 { 1761 if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_MAYWRITE)) 1762 return -EINVAL; 1763 return generic_file_mmap(file, vma); 1764 } 1765 #else 1766 int generic_file_mmap(struct file * file, struct vm_area_struct * vma) 1767 { 1768 return -ENOSYS; 1769 } 1770 int generic_file_readonly_mmap(struct file * file, struct vm_area_struct * vma) 1771 { 1772 return -ENOSYS; 1773 } 1774 #endif /* CONFIG_MMU */ 1775 1776 EXPORT_SYMBOL(generic_file_mmap); 1777 EXPORT_SYMBOL(generic_file_readonly_mmap); 1778 1779 static struct page *__read_cache_page(struct address_space *mapping, 1780 pgoff_t index, 1781 int (*filler)(void *, struct page *), 1782 void *data, 1783 gfp_t gfp) 1784 { 1785 struct page *page; 1786 int err; 1787 repeat: 1788 page = find_get_page(mapping, index); 1789 if (!page) { 1790 page = __page_cache_alloc(gfp | __GFP_COLD); 1791 if (!page) 1792 return ERR_PTR(-ENOMEM); 1793 err = add_to_page_cache_lru(page, mapping, index, gfp); 1794 if (unlikely(err)) { 1795 page_cache_release(page); 1796 if (err == -EEXIST) 1797 goto repeat; 1798 /* Presumably ENOMEM for radix tree node */ 1799 return ERR_PTR(err); 1800 } 1801 err = filler(data, page); 1802 if (err < 0) { 1803 page_cache_release(page); 1804 page = ERR_PTR(err); 1805 } 1806 } 1807 return page; 1808 } 1809 1810 static struct page *do_read_cache_page(struct address_space *mapping, 1811 pgoff_t index, 1812 int (*filler)(void *, struct page *), 1813 void *data, 1814 gfp_t gfp) 1815 1816 { 1817 struct page *page; 1818 int err; 1819 1820 retry: 1821 page = __read_cache_page(mapping, index, filler, data, gfp); 1822 if (IS_ERR(page)) 1823 return page; 1824 if (PageUptodate(page)) 1825 goto out; 1826 1827 lock_page(page); 1828 if (!page->mapping) { 1829 unlock_page(page); 1830 page_cache_release(page); 1831 goto retry; 1832 } 1833 if (PageUptodate(page)) { 1834 unlock_page(page); 1835 goto out; 1836 } 1837 err = filler(data, page); 1838 if (err < 0) { 1839 page_cache_release(page); 1840 return ERR_PTR(err); 1841 } 1842 out: 1843 mark_page_accessed(page); 1844 return page; 1845 } 1846 1847 /** 1848 * read_cache_page_async - read into page cache, fill it if needed 1849 * @mapping: the page's address_space 1850 * @index: the page index 1851 * @filler: function to perform the read 1852 * @data: first arg to filler(data, page) function, often left as NULL 1853 * 1854 * Same as read_cache_page, but don't wait for page to become unlocked 1855 * after submitting it to the filler. 1856 * 1857 * Read into the page cache. If a page already exists, and PageUptodate() is 1858 * not set, try to fill the page but don't wait for it to become unlocked. 1859 * 1860 * If the page does not get brought uptodate, return -EIO. 1861 */ 1862 struct page *read_cache_page_async(struct address_space *mapping, 1863 pgoff_t index, 1864 int (*filler)(void *, struct page *), 1865 void *data) 1866 { 1867 return do_read_cache_page(mapping, index, filler, data, mapping_gfp_mask(mapping)); 1868 } 1869 EXPORT_SYMBOL(read_cache_page_async); 1870 1871 static struct page *wait_on_page_read(struct page *page) 1872 { 1873 if (!IS_ERR(page)) { 1874 wait_on_page_locked(page); 1875 if (!PageUptodate(page)) { 1876 page_cache_release(page); 1877 page = ERR_PTR(-EIO); 1878 } 1879 } 1880 return page; 1881 } 1882 1883 /** 1884 * read_cache_page_gfp - read into page cache, using specified page allocation flags. 1885 * @mapping: the page's address_space 1886 * @index: the page index 1887 * @gfp: the page allocator flags to use if allocating 1888 * 1889 * This is the same as "read_mapping_page(mapping, index, NULL)", but with 1890 * any new page allocations done using the specified allocation flags. 1891 * 1892 * If the page does not get brought uptodate, return -EIO. 1893 */ 1894 struct page *read_cache_page_gfp(struct address_space *mapping, 1895 pgoff_t index, 1896 gfp_t gfp) 1897 { 1898 filler_t *filler = (filler_t *)mapping->a_ops->readpage; 1899 1900 return wait_on_page_read(do_read_cache_page(mapping, index, filler, NULL, gfp)); 1901 } 1902 EXPORT_SYMBOL(read_cache_page_gfp); 1903 1904 /** 1905 * read_cache_page - read into page cache, fill it if needed 1906 * @mapping: the page's address_space 1907 * @index: the page index 1908 * @filler: function to perform the read 1909 * @data: first arg to filler(data, page) function, often left as NULL 1910 * 1911 * Read into the page cache. If a page already exists, and PageUptodate() is 1912 * not set, try to fill the page then wait for it to become unlocked. 1913 * 1914 * If the page does not get brought uptodate, return -EIO. 1915 */ 1916 struct page *read_cache_page(struct address_space *mapping, 1917 pgoff_t index, 1918 int (*filler)(void *, struct page *), 1919 void *data) 1920 { 1921 return wait_on_page_read(read_cache_page_async(mapping, index, filler, data)); 1922 } 1923 EXPORT_SYMBOL(read_cache_page); 1924 1925 static size_t __iovec_copy_from_user_inatomic(char *vaddr, 1926 const struct iovec *iov, size_t base, size_t bytes) 1927 { 1928 size_t copied = 0, left = 0; 1929 1930 while (bytes) { 1931 char __user *buf = iov->iov_base + base; 1932 int copy = min(bytes, iov->iov_len - base); 1933 1934 base = 0; 1935 left = __copy_from_user_inatomic(vaddr, buf, copy); 1936 copied += copy; 1937 bytes -= copy; 1938 vaddr += copy; 1939 iov++; 1940 1941 if (unlikely(left)) 1942 break; 1943 } 1944 return copied - left; 1945 } 1946 1947 /* 1948 * Copy as much as we can into the page and return the number of bytes which 1949 * were successfully copied. If a fault is encountered then return the number of 1950 * bytes which were copied. 1951 */ 1952 size_t iov_iter_copy_from_user_atomic(struct page *page, 1953 struct iov_iter *i, unsigned long offset, size_t bytes) 1954 { 1955 char *kaddr; 1956 size_t copied; 1957 1958 BUG_ON(!in_atomic()); 1959 kaddr = kmap_atomic(page); 1960 if (likely(i->nr_segs == 1)) { 1961 int left; 1962 char __user *buf = i->iov->iov_base + i->iov_offset; 1963 left = __copy_from_user_inatomic(kaddr + offset, buf, bytes); 1964 copied = bytes - left; 1965 } else { 1966 copied = __iovec_copy_from_user_inatomic(kaddr + offset, 1967 i->iov, i->iov_offset, bytes); 1968 } 1969 kunmap_atomic(kaddr); 1970 1971 return copied; 1972 } 1973 EXPORT_SYMBOL(iov_iter_copy_from_user_atomic); 1974 1975 /* 1976 * This has the same sideeffects and return value as 1977 * iov_iter_copy_from_user_atomic(). 1978 * The difference is that it attempts to resolve faults. 1979 * Page must not be locked. 1980 */ 1981 size_t iov_iter_copy_from_user(struct page *page, 1982 struct iov_iter *i, unsigned long offset, size_t bytes) 1983 { 1984 char *kaddr; 1985 size_t copied; 1986 1987 kaddr = kmap(page); 1988 if (likely(i->nr_segs == 1)) { 1989 int left; 1990 char __user *buf = i->iov->iov_base + i->iov_offset; 1991 left = __copy_from_user(kaddr + offset, buf, bytes); 1992 copied = bytes - left; 1993 } else { 1994 copied = __iovec_copy_from_user_inatomic(kaddr + offset, 1995 i->iov, i->iov_offset, bytes); 1996 } 1997 kunmap(page); 1998 return copied; 1999 } 2000 EXPORT_SYMBOL(iov_iter_copy_from_user); 2001 2002 void iov_iter_advance(struct iov_iter *i, size_t bytes) 2003 { 2004 BUG_ON(i->count < bytes); 2005 2006 if (likely(i->nr_segs == 1)) { 2007 i->iov_offset += bytes; 2008 i->count -= bytes; 2009 } else { 2010 const struct iovec *iov = i->iov; 2011 size_t base = i->iov_offset; 2012 unsigned long nr_segs = i->nr_segs; 2013 2014 /* 2015 * The !iov->iov_len check ensures we skip over unlikely 2016 * zero-length segments (without overruning the iovec). 2017 */ 2018 while (bytes || unlikely(i->count && !iov->iov_len)) { 2019 int copy; 2020 2021 copy = min(bytes, iov->iov_len - base); 2022 BUG_ON(!i->count || i->count < copy); 2023 i->count -= copy; 2024 bytes -= copy; 2025 base += copy; 2026 if (iov->iov_len == base) { 2027 iov++; 2028 nr_segs--; 2029 base = 0; 2030 } 2031 } 2032 i->iov = iov; 2033 i->iov_offset = base; 2034 i->nr_segs = nr_segs; 2035 } 2036 } 2037 EXPORT_SYMBOL(iov_iter_advance); 2038 2039 /* 2040 * Fault in the first iovec of the given iov_iter, to a maximum length 2041 * of bytes. Returns 0 on success, or non-zero if the memory could not be 2042 * accessed (ie. because it is an invalid address). 2043 * 2044 * writev-intensive code may want this to prefault several iovecs -- that 2045 * would be possible (callers must not rely on the fact that _only_ the 2046 * first iovec will be faulted with the current implementation). 2047 */ 2048 int iov_iter_fault_in_readable(struct iov_iter *i, size_t bytes) 2049 { 2050 char __user *buf = i->iov->iov_base + i->iov_offset; 2051 bytes = min(bytes, i->iov->iov_len - i->iov_offset); 2052 return fault_in_pages_readable(buf, bytes); 2053 } 2054 EXPORT_SYMBOL(iov_iter_fault_in_readable); 2055 2056 /* 2057 * Return the count of just the current iov_iter segment. 2058 */ 2059 size_t iov_iter_single_seg_count(struct iov_iter *i) 2060 { 2061 const struct iovec *iov = i->iov; 2062 if (i->nr_segs == 1) 2063 return i->count; 2064 else 2065 return min(i->count, iov->iov_len - i->iov_offset); 2066 } 2067 EXPORT_SYMBOL(iov_iter_single_seg_count); 2068 2069 /* 2070 * Performs necessary checks before doing a write 2071 * 2072 * Can adjust writing position or amount of bytes to write. 2073 * Returns appropriate error code that caller should return or 2074 * zero in case that write should be allowed. 2075 */ 2076 inline int generic_write_checks(struct file *file, loff_t *pos, size_t *count, int isblk) 2077 { 2078 struct inode *inode = file->f_mapping->host; 2079 unsigned long limit = rlimit(RLIMIT_FSIZE); 2080 2081 if (unlikely(*pos < 0)) 2082 return -EINVAL; 2083 2084 if (!isblk) { 2085 /* FIXME: this is for backwards compatibility with 2.4 */ 2086 if (file->f_flags & O_APPEND) 2087 *pos = i_size_read(inode); 2088 2089 if (limit != RLIM_INFINITY) { 2090 if (*pos >= limit) { 2091 send_sig(SIGXFSZ, current, 0); 2092 return -EFBIG; 2093 } 2094 if (*count > limit - (typeof(limit))*pos) { 2095 *count = limit - (typeof(limit))*pos; 2096 } 2097 } 2098 } 2099 2100 /* 2101 * LFS rule 2102 */ 2103 if (unlikely(*pos + *count > MAX_NON_LFS && 2104 !(file->f_flags & O_LARGEFILE))) { 2105 if (*pos >= MAX_NON_LFS) { 2106 return -EFBIG; 2107 } 2108 if (*count > MAX_NON_LFS - (unsigned long)*pos) { 2109 *count = MAX_NON_LFS - (unsigned long)*pos; 2110 } 2111 } 2112 2113 /* 2114 * Are we about to exceed the fs block limit ? 2115 * 2116 * If we have written data it becomes a short write. If we have 2117 * exceeded without writing data we send a signal and return EFBIG. 2118 * Linus frestrict idea will clean these up nicely.. 2119 */ 2120 if (likely(!isblk)) { 2121 if (unlikely(*pos >= inode->i_sb->s_maxbytes)) { 2122 if (*count || *pos > inode->i_sb->s_maxbytes) { 2123 return -EFBIG; 2124 } 2125 /* zero-length writes at ->s_maxbytes are OK */ 2126 } 2127 2128 if (unlikely(*pos + *count > inode->i_sb->s_maxbytes)) 2129 *count = inode->i_sb->s_maxbytes - *pos; 2130 } else { 2131 #ifdef CONFIG_BLOCK 2132 loff_t isize; 2133 if (bdev_read_only(I_BDEV(inode))) 2134 return -EPERM; 2135 isize = i_size_read(inode); 2136 if (*pos >= isize) { 2137 if (*count || *pos > isize) 2138 return -ENOSPC; 2139 } 2140 2141 if (*pos + *count > isize) 2142 *count = isize - *pos; 2143 #else 2144 return -EPERM; 2145 #endif 2146 } 2147 return 0; 2148 } 2149 EXPORT_SYMBOL(generic_write_checks); 2150 2151 int pagecache_write_begin(struct file *file, struct address_space *mapping, 2152 loff_t pos, unsigned len, unsigned flags, 2153 struct page **pagep, void **fsdata) 2154 { 2155 const struct address_space_operations *aops = mapping->a_ops; 2156 2157 return aops->write_begin(file, mapping, pos, len, flags, 2158 pagep, fsdata); 2159 } 2160 EXPORT_SYMBOL(pagecache_write_begin); 2161 2162 int pagecache_write_end(struct file *file, struct address_space *mapping, 2163 loff_t pos, unsigned len, unsigned copied, 2164 struct page *page, void *fsdata) 2165 { 2166 const struct address_space_operations *aops = mapping->a_ops; 2167 2168 mark_page_accessed(page); 2169 return aops->write_end(file, mapping, pos, len, copied, page, fsdata); 2170 } 2171 EXPORT_SYMBOL(pagecache_write_end); 2172 2173 ssize_t 2174 generic_file_direct_write(struct kiocb *iocb, const struct iovec *iov, 2175 unsigned long *nr_segs, loff_t pos, loff_t *ppos, 2176 size_t count, size_t ocount) 2177 { 2178 struct file *file = iocb->ki_filp; 2179 struct address_space *mapping = file->f_mapping; 2180 struct inode *inode = mapping->host; 2181 ssize_t written; 2182 size_t write_len; 2183 pgoff_t end; 2184 2185 if (count != ocount) 2186 *nr_segs = iov_shorten((struct iovec *)iov, *nr_segs, count); 2187 2188 write_len = iov_length(iov, *nr_segs); 2189 end = (pos + write_len - 1) >> PAGE_CACHE_SHIFT; 2190 2191 written = filemap_write_and_wait_range(mapping, pos, pos + write_len - 1); 2192 if (written) 2193 goto out; 2194 2195 /* 2196 * After a write we want buffered reads to be sure to go to disk to get 2197 * the new data. We invalidate clean cached page from the region we're 2198 * about to write. We do this *before* the write so that we can return 2199 * without clobbering -EIOCBQUEUED from ->direct_IO(). 2200 */ 2201 if (mapping->nrpages) { 2202 written = invalidate_inode_pages2_range(mapping, 2203 pos >> PAGE_CACHE_SHIFT, end); 2204 /* 2205 * If a page can not be invalidated, return 0 to fall back 2206 * to buffered write. 2207 */ 2208 if (written) { 2209 if (written == -EBUSY) 2210 return 0; 2211 goto out; 2212 } 2213 } 2214 2215 written = mapping->a_ops->direct_IO(WRITE, iocb, iov, pos, *nr_segs); 2216 2217 /* 2218 * Finally, try again to invalidate clean pages which might have been 2219 * cached by non-direct readahead, or faulted in by get_user_pages() 2220 * if the source of the write was an mmap'ed region of the file 2221 * we're writing. Either one is a pretty crazy thing to do, 2222 * so we don't support it 100%. If this invalidation 2223 * fails, tough, the write still worked... 2224 */ 2225 if (mapping->nrpages) { 2226 invalidate_inode_pages2_range(mapping, 2227 pos >> PAGE_CACHE_SHIFT, end); 2228 } 2229 2230 if (written > 0) { 2231 pos += written; 2232 if (pos > i_size_read(inode) && !S_ISBLK(inode->i_mode)) { 2233 i_size_write(inode, pos); 2234 mark_inode_dirty(inode); 2235 } 2236 *ppos = pos; 2237 } 2238 out: 2239 return written; 2240 } 2241 EXPORT_SYMBOL(generic_file_direct_write); 2242 2243 /* 2244 * Find or create a page at the given pagecache position. Return the locked 2245 * page. This function is specifically for buffered writes. 2246 */ 2247 struct page *grab_cache_page_write_begin(struct address_space *mapping, 2248 pgoff_t index, unsigned flags) 2249 { 2250 int status; 2251 gfp_t gfp_mask; 2252 struct page *page; 2253 gfp_t gfp_notmask = 0; 2254 2255 gfp_mask = mapping_gfp_mask(mapping); 2256 if (mapping_cap_account_dirty(mapping)) 2257 gfp_mask |= __GFP_WRITE; 2258 if (flags & AOP_FLAG_NOFS) 2259 gfp_notmask = __GFP_FS; 2260 repeat: 2261 page = find_lock_page(mapping, index); 2262 if (page) 2263 goto found; 2264 2265 page = __page_cache_alloc(gfp_mask & ~gfp_notmask); 2266 if (!page) 2267 return NULL; 2268 status = add_to_page_cache_lru(page, mapping, index, 2269 GFP_KERNEL & ~gfp_notmask); 2270 if (unlikely(status)) { 2271 page_cache_release(page); 2272 if (status == -EEXIST) 2273 goto repeat; 2274 return NULL; 2275 } 2276 found: 2277 wait_on_page_writeback(page); 2278 return page; 2279 } 2280 EXPORT_SYMBOL(grab_cache_page_write_begin); 2281 2282 static ssize_t generic_perform_write(struct file *file, 2283 struct iov_iter *i, loff_t pos) 2284 { 2285 struct address_space *mapping = file->f_mapping; 2286 const struct address_space_operations *a_ops = mapping->a_ops; 2287 long status = 0; 2288 ssize_t written = 0; 2289 unsigned int flags = 0; 2290 2291 /* 2292 * Copies from kernel address space cannot fail (NFSD is a big user). 2293 */ 2294 if (segment_eq(get_fs(), KERNEL_DS)) 2295 flags |= AOP_FLAG_UNINTERRUPTIBLE; 2296 2297 do { 2298 struct page *page; 2299 unsigned long offset; /* Offset into pagecache page */ 2300 unsigned long bytes; /* Bytes to write to page */ 2301 size_t copied; /* Bytes copied from user */ 2302 void *fsdata; 2303 2304 offset = (pos & (PAGE_CACHE_SIZE - 1)); 2305 bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset, 2306 iov_iter_count(i)); 2307 2308 again: 2309 /* 2310 * Bring in the user page that we will copy from _first_. 2311 * Otherwise there's a nasty deadlock on copying from the 2312 * same page as we're writing to, without it being marked 2313 * up-to-date. 2314 * 2315 * Not only is this an optimisation, but it is also required 2316 * to check that the address is actually valid, when atomic 2317 * usercopies are used, below. 2318 */ 2319 if (unlikely(iov_iter_fault_in_readable(i, bytes))) { 2320 status = -EFAULT; 2321 break; 2322 } 2323 2324 status = a_ops->write_begin(file, mapping, pos, bytes, flags, 2325 &page, &fsdata); 2326 if (unlikely(status)) 2327 break; 2328 2329 if (mapping_writably_mapped(mapping)) 2330 flush_dcache_page(page); 2331 2332 pagefault_disable(); 2333 copied = iov_iter_copy_from_user_atomic(page, i, offset, bytes); 2334 pagefault_enable(); 2335 flush_dcache_page(page); 2336 2337 mark_page_accessed(page); 2338 status = a_ops->write_end(file, mapping, pos, bytes, copied, 2339 page, fsdata); 2340 if (unlikely(status < 0)) 2341 break; 2342 copied = status; 2343 2344 cond_resched(); 2345 2346 iov_iter_advance(i, copied); 2347 if (unlikely(copied == 0)) { 2348 /* 2349 * If we were unable to copy any data at all, we must 2350 * fall back to a single segment length write. 2351 * 2352 * If we didn't fallback here, we could livelock 2353 * because not all segments in the iov can be copied at 2354 * once without a pagefault. 2355 */ 2356 bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset, 2357 iov_iter_single_seg_count(i)); 2358 goto again; 2359 } 2360 pos += copied; 2361 written += copied; 2362 2363 balance_dirty_pages_ratelimited(mapping); 2364 if (fatal_signal_pending(current)) { 2365 status = -EINTR; 2366 break; 2367 } 2368 } while (iov_iter_count(i)); 2369 2370 return written ? written : status; 2371 } 2372 2373 ssize_t 2374 generic_file_buffered_write(struct kiocb *iocb, const struct iovec *iov, 2375 unsigned long nr_segs, loff_t pos, loff_t *ppos, 2376 size_t count, ssize_t written) 2377 { 2378 struct file *file = iocb->ki_filp; 2379 ssize_t status; 2380 struct iov_iter i; 2381 2382 iov_iter_init(&i, iov, nr_segs, count, written); 2383 status = generic_perform_write(file, &i, pos); 2384 2385 if (likely(status >= 0)) { 2386 written += status; 2387 *ppos = pos + status; 2388 } 2389 2390 return written ? written : status; 2391 } 2392 EXPORT_SYMBOL(generic_file_buffered_write); 2393 2394 /** 2395 * __generic_file_aio_write - write data to a file 2396 * @iocb: IO state structure (file, offset, etc.) 2397 * @iov: vector with data to write 2398 * @nr_segs: number of segments in the vector 2399 * @ppos: position where to write 2400 * 2401 * This function does all the work needed for actually writing data to a 2402 * file. It does all basic checks, removes SUID from the file, updates 2403 * modification times and calls proper subroutines depending on whether we 2404 * do direct IO or a standard buffered write. 2405 * 2406 * It expects i_mutex to be grabbed unless we work on a block device or similar 2407 * object which does not need locking at all. 2408 * 2409 * This function does *not* take care of syncing data in case of O_SYNC write. 2410 * A caller has to handle it. This is mainly due to the fact that we want to 2411 * avoid syncing under i_mutex. 2412 */ 2413 ssize_t __generic_file_aio_write(struct kiocb *iocb, const struct iovec *iov, 2414 unsigned long nr_segs, loff_t *ppos) 2415 { 2416 struct file *file = iocb->ki_filp; 2417 struct address_space * mapping = file->f_mapping; 2418 size_t ocount; /* original count */ 2419 size_t count; /* after file limit checks */ 2420 struct inode *inode = mapping->host; 2421 loff_t pos; 2422 ssize_t written; 2423 ssize_t err; 2424 2425 ocount = 0; 2426 err = generic_segment_checks(iov, &nr_segs, &ocount, VERIFY_READ); 2427 if (err) 2428 return err; 2429 2430 count = ocount; 2431 pos = *ppos; 2432 2433 /* We can write back this queue in page reclaim */ 2434 current->backing_dev_info = mapping->backing_dev_info; 2435 written = 0; 2436 2437 err = generic_write_checks(file, &pos, &count, S_ISBLK(inode->i_mode)); 2438 if (err) 2439 goto out; 2440 2441 if (count == 0) 2442 goto out; 2443 2444 err = file_remove_suid(file); 2445 if (err) 2446 goto out; 2447 2448 err = file_update_time(file); 2449 if (err) 2450 goto out; 2451 2452 /* coalesce the iovecs and go direct-to-BIO for O_DIRECT */ 2453 if (unlikely(file->f_flags & O_DIRECT)) { 2454 loff_t endbyte; 2455 ssize_t written_buffered; 2456 2457 written = generic_file_direct_write(iocb, iov, &nr_segs, pos, 2458 ppos, count, ocount); 2459 if (written < 0 || written == count) 2460 goto out; 2461 /* 2462 * direct-io write to a hole: fall through to buffered I/O 2463 * for completing the rest of the request. 2464 */ 2465 pos += written; 2466 count -= written; 2467 written_buffered = generic_file_buffered_write(iocb, iov, 2468 nr_segs, pos, ppos, count, 2469 written); 2470 /* 2471 * If generic_file_buffered_write() retuned a synchronous error 2472 * then we want to return the number of bytes which were 2473 * direct-written, or the error code if that was zero. Note 2474 * that this differs from normal direct-io semantics, which 2475 * will return -EFOO even if some bytes were written. 2476 */ 2477 if (written_buffered < 0) { 2478 err = written_buffered; 2479 goto out; 2480 } 2481 2482 /* 2483 * We need to ensure that the page cache pages are written to 2484 * disk and invalidated to preserve the expected O_DIRECT 2485 * semantics. 2486 */ 2487 endbyte = pos + written_buffered - written - 1; 2488 err = filemap_write_and_wait_range(file->f_mapping, pos, endbyte); 2489 if (err == 0) { 2490 written = written_buffered; 2491 invalidate_mapping_pages(mapping, 2492 pos >> PAGE_CACHE_SHIFT, 2493 endbyte >> PAGE_CACHE_SHIFT); 2494 } else { 2495 /* 2496 * We don't know how much we wrote, so just return 2497 * the number of bytes which were direct-written 2498 */ 2499 } 2500 } else { 2501 written = generic_file_buffered_write(iocb, iov, nr_segs, 2502 pos, ppos, count, written); 2503 } 2504 out: 2505 current->backing_dev_info = NULL; 2506 return written ? written : err; 2507 } 2508 EXPORT_SYMBOL(__generic_file_aio_write); 2509 2510 /** 2511 * generic_file_aio_write - write data to a file 2512 * @iocb: IO state structure 2513 * @iov: vector with data to write 2514 * @nr_segs: number of segments in the vector 2515 * @pos: position in file where to write 2516 * 2517 * This is a wrapper around __generic_file_aio_write() to be used by most 2518 * filesystems. It takes care of syncing the file in case of O_SYNC file 2519 * and acquires i_mutex as needed. 2520 */ 2521 ssize_t generic_file_aio_write(struct kiocb *iocb, const struct iovec *iov, 2522 unsigned long nr_segs, loff_t pos) 2523 { 2524 struct file *file = iocb->ki_filp; 2525 struct inode *inode = file->f_mapping->host; 2526 ssize_t ret; 2527 2528 BUG_ON(iocb->ki_pos != pos); 2529 2530 sb_start_write(inode->i_sb); 2531 mutex_lock(&inode->i_mutex); 2532 ret = __generic_file_aio_write(iocb, iov, nr_segs, &iocb->ki_pos); 2533 mutex_unlock(&inode->i_mutex); 2534 2535 if (ret > 0 || ret == -EIOCBQUEUED) { 2536 ssize_t err; 2537 2538 err = generic_write_sync(file, pos, ret); 2539 if (err < 0 && ret > 0) 2540 ret = err; 2541 } 2542 sb_end_write(inode->i_sb); 2543 return ret; 2544 } 2545 EXPORT_SYMBOL(generic_file_aio_write); 2546 2547 /** 2548 * try_to_release_page() - release old fs-specific metadata on a page 2549 * 2550 * @page: the page which the kernel is trying to free 2551 * @gfp_mask: memory allocation flags (and I/O mode) 2552 * 2553 * The address_space is to try to release any data against the page 2554 * (presumably at page->private). If the release was successful, return `1'. 2555 * Otherwise return zero. 2556 * 2557 * This may also be called if PG_fscache is set on a page, indicating that the 2558 * page is known to the local caching routines. 2559 * 2560 * The @gfp_mask argument specifies whether I/O may be performed to release 2561 * this page (__GFP_IO), and whether the call may block (__GFP_WAIT & __GFP_FS). 2562 * 2563 */ 2564 int try_to_release_page(struct page *page, gfp_t gfp_mask) 2565 { 2566 struct address_space * const mapping = page->mapping; 2567 2568 BUG_ON(!PageLocked(page)); 2569 if (PageWriteback(page)) 2570 return 0; 2571 2572 if (mapping && mapping->a_ops->releasepage) 2573 return mapping->a_ops->releasepage(page, gfp_mask); 2574 return try_to_free_buffers(page); 2575 } 2576 2577 EXPORT_SYMBOL(try_to_release_page); 2578