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