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/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/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/cleancache.h> 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_mutex (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_mutex (truncate->unmap_mapping_range) 68 * 69 * ->mmap_sem 70 * ->i_mmap_mutex 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 * bdi->wb.list_lock 81 * sb_lock (fs/fs-writeback.c) 82 * ->mapping->tree_lock (__sync_single_inode) 83 * 84 * ->i_mmap_mutex 85 * ->anon_vma.lock (vma_adjust) 86 * 87 * ->anon_vma.lock 88 * ->page_table_lock or pte_lock (anon_vma_prepare and various) 89 * 90 * ->page_table_lock or pte_lock 91 * ->swap_lock (try_to_unmap_one) 92 * ->private_lock (try_to_unmap_one) 93 * ->tree_lock (try_to_unmap_one) 94 * ->zone.lru_lock (follow_page->mark_page_accessed) 95 * ->zone.lru_lock (check_pte_range->isolate_lru_page) 96 * ->private_lock (page_remove_rmap->set_page_dirty) 97 * ->tree_lock (page_remove_rmap->set_page_dirty) 98 * bdi.wb->list_lock (page_remove_rmap->set_page_dirty) 99 * ->inode->i_lock (page_remove_rmap->set_page_dirty) 100 * bdi.wb->list_lock (zap_pte_range->set_page_dirty) 101 * ->inode->i_lock (zap_pte_range->set_page_dirty) 102 * ->private_lock (zap_pte_range->__set_page_dirty_buffers) 103 * 104 * (code doesn't rely on that order, so you could switch it around) 105 * ->tasklist_lock (memory_failure, collect_procs_ao) 106 * ->i_mmap_mutex 107 */ 108 109 /* 110 * Delete a page from the page cache and free it. Caller has to make 111 * sure the page is locked and that nobody else uses it - or that usage 112 * is safe. The caller must hold the mapping's tree_lock. 113 */ 114 void __delete_from_page_cache(struct page *page) 115 { 116 struct address_space *mapping = page->mapping; 117 118 /* 119 * if we're uptodate, flush out into the cleancache, otherwise 120 * invalidate any existing cleancache entries. We can't leave 121 * stale data around in the cleancache once our page is gone 122 */ 123 if (PageUptodate(page) && PageMappedToDisk(page)) 124 cleancache_put_page(page); 125 else 126 cleancache_flush_page(mapping, page); 127 128 radix_tree_delete(&mapping->page_tree, page->index); 129 page->mapping = NULL; 130 /* Leave page->index set: truncation lookup relies upon it */ 131 mapping->nrpages--; 132 __dec_zone_page_state(page, NR_FILE_PAGES); 133 if (PageSwapBacked(page)) 134 __dec_zone_page_state(page, NR_SHMEM); 135 BUG_ON(page_mapped(page)); 136 137 /* 138 * Some filesystems seem to re-dirty the page even after 139 * the VM has canceled the dirty bit (eg ext3 journaling). 140 * 141 * Fix it up by doing a final dirty accounting check after 142 * having removed the page entirely. 143 */ 144 if (PageDirty(page) && mapping_cap_account_dirty(mapping)) { 145 dec_zone_page_state(page, NR_FILE_DIRTY); 146 dec_bdi_stat(mapping->backing_dev_info, BDI_RECLAIMABLE); 147 } 148 } 149 150 /** 151 * delete_from_page_cache - delete page from page cache 152 * @page: the page which the kernel is trying to remove from page cache 153 * 154 * This must be called only on pages that have been verified to be in the page 155 * cache and locked. It will never put the page into the free list, the caller 156 * has a reference on the page. 157 */ 158 void delete_from_page_cache(struct page *page) 159 { 160 struct address_space *mapping = page->mapping; 161 void (*freepage)(struct page *); 162 163 BUG_ON(!PageLocked(page)); 164 165 freepage = mapping->a_ops->freepage; 166 spin_lock_irq(&mapping->tree_lock); 167 __delete_from_page_cache(page); 168 spin_unlock_irq(&mapping->tree_lock); 169 mem_cgroup_uncharge_cache_page(page); 170 171 if (freepage) 172 freepage(page); 173 page_cache_release(page); 174 } 175 EXPORT_SYMBOL(delete_from_page_cache); 176 177 static int sleep_on_page(void *word) 178 { 179 io_schedule(); 180 return 0; 181 } 182 183 static int sleep_on_page_killable(void *word) 184 { 185 sleep_on_page(word); 186 return fatal_signal_pending(current) ? -EINTR : 0; 187 } 188 189 /** 190 * __filemap_fdatawrite_range - start writeback on mapping dirty pages in range 191 * @mapping: address space structure to write 192 * @start: offset in bytes where the range starts 193 * @end: offset in bytes where the range ends (inclusive) 194 * @sync_mode: enable synchronous operation 195 * 196 * Start writeback against all of a mapping's dirty pages that lie 197 * within the byte offsets <start, end> inclusive. 198 * 199 * If sync_mode is WB_SYNC_ALL then this is a "data integrity" operation, as 200 * opposed to a regular memory cleansing writeback. The difference between 201 * these two operations is that if a dirty page/buffer is encountered, it must 202 * be waited upon, and not just skipped over. 203 */ 204 int __filemap_fdatawrite_range(struct address_space *mapping, loff_t start, 205 loff_t end, int sync_mode) 206 { 207 int ret; 208 struct writeback_control wbc = { 209 .sync_mode = sync_mode, 210 .nr_to_write = LONG_MAX, 211 .range_start = start, 212 .range_end = end, 213 }; 214 215 if (!mapping_cap_writeback_dirty(mapping)) 216 return 0; 217 218 ret = do_writepages(mapping, &wbc); 219 return ret; 220 } 221 222 static inline int __filemap_fdatawrite(struct address_space *mapping, 223 int sync_mode) 224 { 225 return __filemap_fdatawrite_range(mapping, 0, LLONG_MAX, sync_mode); 226 } 227 228 int filemap_fdatawrite(struct address_space *mapping) 229 { 230 return __filemap_fdatawrite(mapping, WB_SYNC_ALL); 231 } 232 EXPORT_SYMBOL(filemap_fdatawrite); 233 234 int filemap_fdatawrite_range(struct address_space *mapping, loff_t start, 235 loff_t end) 236 { 237 return __filemap_fdatawrite_range(mapping, start, end, WB_SYNC_ALL); 238 } 239 EXPORT_SYMBOL(filemap_fdatawrite_range); 240 241 /** 242 * filemap_flush - mostly a non-blocking flush 243 * @mapping: target address_space 244 * 245 * This is a mostly non-blocking flush. Not suitable for data-integrity 246 * purposes - I/O may not be started against all dirty pages. 247 */ 248 int filemap_flush(struct address_space *mapping) 249 { 250 return __filemap_fdatawrite(mapping, WB_SYNC_NONE); 251 } 252 EXPORT_SYMBOL(filemap_flush); 253 254 /** 255 * filemap_fdatawait_range - wait for writeback to complete 256 * @mapping: address space structure to wait for 257 * @start_byte: offset in bytes where the range starts 258 * @end_byte: offset in bytes where the range ends (inclusive) 259 * 260 * Walk the list of under-writeback pages of the given address space 261 * in the given range and wait for all of them. 262 */ 263 int filemap_fdatawait_range(struct address_space *mapping, loff_t start_byte, 264 loff_t end_byte) 265 { 266 pgoff_t index = start_byte >> PAGE_CACHE_SHIFT; 267 pgoff_t end = end_byte >> PAGE_CACHE_SHIFT; 268 struct pagevec pvec; 269 int nr_pages; 270 int ret = 0; 271 272 if (end_byte < start_byte) 273 return 0; 274 275 pagevec_init(&pvec, 0); 276 while ((index <= end) && 277 (nr_pages = pagevec_lookup_tag(&pvec, mapping, &index, 278 PAGECACHE_TAG_WRITEBACK, 279 min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1)) != 0) { 280 unsigned i; 281 282 for (i = 0; i < nr_pages; i++) { 283 struct page *page = pvec.pages[i]; 284 285 /* until radix tree lookup accepts end_index */ 286 if (page->index > end) 287 continue; 288 289 wait_on_page_writeback(page); 290 if (TestClearPageError(page)) 291 ret = -EIO; 292 } 293 pagevec_release(&pvec); 294 cond_resched(); 295 } 296 297 /* Check for outstanding write errors */ 298 if (test_and_clear_bit(AS_ENOSPC, &mapping->flags)) 299 ret = -ENOSPC; 300 if (test_and_clear_bit(AS_EIO, &mapping->flags)) 301 ret = -EIO; 302 303 return ret; 304 } 305 EXPORT_SYMBOL(filemap_fdatawait_range); 306 307 /** 308 * filemap_fdatawait - wait for all under-writeback pages to complete 309 * @mapping: address space structure to wait for 310 * 311 * Walk the list of under-writeback pages of the given address space 312 * and wait for all of them. 313 */ 314 int filemap_fdatawait(struct address_space *mapping) 315 { 316 loff_t i_size = i_size_read(mapping->host); 317 318 if (i_size == 0) 319 return 0; 320 321 return filemap_fdatawait_range(mapping, 0, i_size - 1); 322 } 323 EXPORT_SYMBOL(filemap_fdatawait); 324 325 int filemap_write_and_wait(struct address_space *mapping) 326 { 327 int err = 0; 328 329 if (mapping->nrpages) { 330 err = filemap_fdatawrite(mapping); 331 /* 332 * Even if the above returned error, the pages may be 333 * written partially (e.g. -ENOSPC), so we wait for it. 334 * But the -EIO is special case, it may indicate the worst 335 * thing (e.g. bug) happened, so we avoid waiting for it. 336 */ 337 if (err != -EIO) { 338 int err2 = filemap_fdatawait(mapping); 339 if (!err) 340 err = err2; 341 } 342 } 343 return err; 344 } 345 EXPORT_SYMBOL(filemap_write_and_wait); 346 347 /** 348 * filemap_write_and_wait_range - write out & wait on a file range 349 * @mapping: the address_space for the pages 350 * @lstart: offset in bytes where the range starts 351 * @lend: offset in bytes where the range ends (inclusive) 352 * 353 * Write out and wait upon file offsets lstart->lend, inclusive. 354 * 355 * Note that `lend' is inclusive (describes the last byte to be written) so 356 * that this function can be used to write to the very end-of-file (end = -1). 357 */ 358 int filemap_write_and_wait_range(struct address_space *mapping, 359 loff_t lstart, loff_t lend) 360 { 361 int err = 0; 362 363 if (mapping->nrpages) { 364 err = __filemap_fdatawrite_range(mapping, lstart, lend, 365 WB_SYNC_ALL); 366 /* See comment of filemap_write_and_wait() */ 367 if (err != -EIO) { 368 int err2 = filemap_fdatawait_range(mapping, 369 lstart, lend); 370 if (!err) 371 err = err2; 372 } 373 } 374 return err; 375 } 376 EXPORT_SYMBOL(filemap_write_and_wait_range); 377 378 /** 379 * replace_page_cache_page - replace a pagecache page with a new one 380 * @old: page to be replaced 381 * @new: page to replace with 382 * @gfp_mask: allocation mode 383 * 384 * This function replaces a page in the pagecache with a new one. On 385 * success it acquires the pagecache reference for the new page and 386 * drops it for the old page. Both the old and new pages must be 387 * locked. This function does not add the new page to the LRU, the 388 * caller must do that. 389 * 390 * The remove + add is atomic. The only way this function can fail is 391 * memory allocation failure. 392 */ 393 int replace_page_cache_page(struct page *old, struct page *new, gfp_t gfp_mask) 394 { 395 int error; 396 struct mem_cgroup *memcg = NULL; 397 398 VM_BUG_ON(!PageLocked(old)); 399 VM_BUG_ON(!PageLocked(new)); 400 VM_BUG_ON(new->mapping); 401 402 /* 403 * This is not page migration, but prepare_migration and 404 * end_migration does enough work for charge replacement. 405 * 406 * In the longer term we probably want a specialized function 407 * for moving the charge from old to new in a more efficient 408 * manner. 409 */ 410 error = mem_cgroup_prepare_migration(old, new, &memcg, gfp_mask); 411 if (error) 412 return error; 413 414 error = radix_tree_preload(gfp_mask & ~__GFP_HIGHMEM); 415 if (!error) { 416 struct address_space *mapping = old->mapping; 417 void (*freepage)(struct page *); 418 419 pgoff_t offset = old->index; 420 freepage = mapping->a_ops->freepage; 421 422 page_cache_get(new); 423 new->mapping = mapping; 424 new->index = offset; 425 426 spin_lock_irq(&mapping->tree_lock); 427 __delete_from_page_cache(old); 428 error = radix_tree_insert(&mapping->page_tree, offset, new); 429 BUG_ON(error); 430 mapping->nrpages++; 431 __inc_zone_page_state(new, NR_FILE_PAGES); 432 if (PageSwapBacked(new)) 433 __inc_zone_page_state(new, NR_SHMEM); 434 spin_unlock_irq(&mapping->tree_lock); 435 radix_tree_preload_end(); 436 if (freepage) 437 freepage(old); 438 page_cache_release(old); 439 mem_cgroup_end_migration(memcg, old, new, true); 440 } else { 441 mem_cgroup_end_migration(memcg, old, new, false); 442 } 443 444 return error; 445 } 446 EXPORT_SYMBOL_GPL(replace_page_cache_page); 447 448 /** 449 * add_to_page_cache_locked - add a locked page to the pagecache 450 * @page: page to add 451 * @mapping: the page's address_space 452 * @offset: page index 453 * @gfp_mask: page allocation mode 454 * 455 * This function is used to add a page to the pagecache. It must be locked. 456 * This function does not add the page to the LRU. The caller must do that. 457 */ 458 int add_to_page_cache_locked(struct page *page, struct address_space *mapping, 459 pgoff_t offset, gfp_t gfp_mask) 460 { 461 int error; 462 463 VM_BUG_ON(!PageLocked(page)); 464 VM_BUG_ON(PageSwapBacked(page)); 465 466 error = mem_cgroup_cache_charge(page, current->mm, 467 gfp_mask & GFP_RECLAIM_MASK); 468 if (error) 469 goto out; 470 471 error = radix_tree_preload(gfp_mask & ~__GFP_HIGHMEM); 472 if (error == 0) { 473 page_cache_get(page); 474 page->mapping = mapping; 475 page->index = offset; 476 477 spin_lock_irq(&mapping->tree_lock); 478 error = radix_tree_insert(&mapping->page_tree, offset, page); 479 if (likely(!error)) { 480 mapping->nrpages++; 481 __inc_zone_page_state(page, NR_FILE_PAGES); 482 spin_unlock_irq(&mapping->tree_lock); 483 } else { 484 page->mapping = NULL; 485 /* Leave page->index set: truncation relies upon it */ 486 spin_unlock_irq(&mapping->tree_lock); 487 mem_cgroup_uncharge_cache_page(page); 488 page_cache_release(page); 489 } 490 radix_tree_preload_end(); 491 } else 492 mem_cgroup_uncharge_cache_page(page); 493 out: 494 return error; 495 } 496 EXPORT_SYMBOL(add_to_page_cache_locked); 497 498 int add_to_page_cache_lru(struct page *page, struct address_space *mapping, 499 pgoff_t offset, gfp_t gfp_mask) 500 { 501 int ret; 502 503 ret = add_to_page_cache(page, mapping, offset, gfp_mask); 504 if (ret == 0) 505 lru_cache_add_file(page); 506 return ret; 507 } 508 EXPORT_SYMBOL_GPL(add_to_page_cache_lru); 509 510 #ifdef CONFIG_NUMA 511 struct page *__page_cache_alloc(gfp_t gfp) 512 { 513 int n; 514 struct page *page; 515 516 if (cpuset_do_page_mem_spread()) { 517 get_mems_allowed(); 518 n = cpuset_mem_spread_node(); 519 page = alloc_pages_exact_node(n, gfp, 0); 520 put_mems_allowed(); 521 return page; 522 } 523 return alloc_pages(gfp, 0); 524 } 525 EXPORT_SYMBOL(__page_cache_alloc); 526 #endif 527 528 /* 529 * In order to wait for pages to become available there must be 530 * waitqueues associated with pages. By using a hash table of 531 * waitqueues where the bucket discipline is to maintain all 532 * waiters on the same queue and wake all when any of the pages 533 * become available, and for the woken contexts to check to be 534 * sure the appropriate page became available, this saves space 535 * at a cost of "thundering herd" phenomena during rare hash 536 * collisions. 537 */ 538 static wait_queue_head_t *page_waitqueue(struct page *page) 539 { 540 const struct zone *zone = page_zone(page); 541 542 return &zone->wait_table[hash_ptr(page, zone->wait_table_bits)]; 543 } 544 545 static inline void wake_up_page(struct page *page, int bit) 546 { 547 __wake_up_bit(page_waitqueue(page), &page->flags, bit); 548 } 549 550 void wait_on_page_bit(struct page *page, int bit_nr) 551 { 552 DEFINE_WAIT_BIT(wait, &page->flags, bit_nr); 553 554 if (test_bit(bit_nr, &page->flags)) 555 __wait_on_bit(page_waitqueue(page), &wait, sleep_on_page, 556 TASK_UNINTERRUPTIBLE); 557 } 558 EXPORT_SYMBOL(wait_on_page_bit); 559 560 int wait_on_page_bit_killable(struct page *page, int bit_nr) 561 { 562 DEFINE_WAIT_BIT(wait, &page->flags, bit_nr); 563 564 if (!test_bit(bit_nr, &page->flags)) 565 return 0; 566 567 return __wait_on_bit(page_waitqueue(page), &wait, 568 sleep_on_page_killable, TASK_KILLABLE); 569 } 570 571 /** 572 * add_page_wait_queue - Add an arbitrary waiter to a page's wait queue 573 * @page: Page defining the wait queue of interest 574 * @waiter: Waiter to add to the queue 575 * 576 * Add an arbitrary @waiter to the wait queue for the nominated @page. 577 */ 578 void add_page_wait_queue(struct page *page, wait_queue_t *waiter) 579 { 580 wait_queue_head_t *q = page_waitqueue(page); 581 unsigned long flags; 582 583 spin_lock_irqsave(&q->lock, flags); 584 __add_wait_queue(q, waiter); 585 spin_unlock_irqrestore(&q->lock, flags); 586 } 587 EXPORT_SYMBOL_GPL(add_page_wait_queue); 588 589 /** 590 * unlock_page - unlock a locked page 591 * @page: the page 592 * 593 * Unlocks the page and wakes up sleepers in ___wait_on_page_locked(). 594 * Also wakes sleepers in wait_on_page_writeback() because the wakeup 595 * mechananism between PageLocked pages and PageWriteback pages is shared. 596 * But that's OK - sleepers in wait_on_page_writeback() just go back to sleep. 597 * 598 * The mb is necessary to enforce ordering between the clear_bit and the read 599 * of the waitqueue (to avoid SMP races with a parallel wait_on_page_locked()). 600 */ 601 void unlock_page(struct page *page) 602 { 603 VM_BUG_ON(!PageLocked(page)); 604 clear_bit_unlock(PG_locked, &page->flags); 605 smp_mb__after_clear_bit(); 606 wake_up_page(page, PG_locked); 607 } 608 EXPORT_SYMBOL(unlock_page); 609 610 /** 611 * end_page_writeback - end writeback against a page 612 * @page: the page 613 */ 614 void end_page_writeback(struct page *page) 615 { 616 if (TestClearPageReclaim(page)) 617 rotate_reclaimable_page(page); 618 619 if (!test_clear_page_writeback(page)) 620 BUG(); 621 622 smp_mb__after_clear_bit(); 623 wake_up_page(page, PG_writeback); 624 } 625 EXPORT_SYMBOL(end_page_writeback); 626 627 /** 628 * __lock_page - get a lock on the page, assuming we need to sleep to get it 629 * @page: the page to lock 630 */ 631 void __lock_page(struct page *page) 632 { 633 DEFINE_WAIT_BIT(wait, &page->flags, PG_locked); 634 635 __wait_on_bit_lock(page_waitqueue(page), &wait, sleep_on_page, 636 TASK_UNINTERRUPTIBLE); 637 } 638 EXPORT_SYMBOL(__lock_page); 639 640 int __lock_page_killable(struct page *page) 641 { 642 DEFINE_WAIT_BIT(wait, &page->flags, PG_locked); 643 644 return __wait_on_bit_lock(page_waitqueue(page), &wait, 645 sleep_on_page_killable, TASK_KILLABLE); 646 } 647 EXPORT_SYMBOL_GPL(__lock_page_killable); 648 649 int __lock_page_or_retry(struct page *page, struct mm_struct *mm, 650 unsigned int flags) 651 { 652 if (flags & FAULT_FLAG_ALLOW_RETRY) { 653 /* 654 * CAUTION! In this case, mmap_sem is not released 655 * even though return 0. 656 */ 657 if (flags & FAULT_FLAG_RETRY_NOWAIT) 658 return 0; 659 660 up_read(&mm->mmap_sem); 661 if (flags & FAULT_FLAG_KILLABLE) 662 wait_on_page_locked_killable(page); 663 else 664 wait_on_page_locked(page); 665 return 0; 666 } else { 667 if (flags & FAULT_FLAG_KILLABLE) { 668 int ret; 669 670 ret = __lock_page_killable(page); 671 if (ret) { 672 up_read(&mm->mmap_sem); 673 return 0; 674 } 675 } else 676 __lock_page(page); 677 return 1; 678 } 679 } 680 681 /** 682 * find_get_page - find and get a page reference 683 * @mapping: the address_space to search 684 * @offset: the page index 685 * 686 * Is there a pagecache struct page at the given (mapping, offset) tuple? 687 * If yes, increment its refcount and return it; if no, return NULL. 688 */ 689 struct page *find_get_page(struct address_space *mapping, pgoff_t offset) 690 { 691 void **pagep; 692 struct page *page; 693 694 rcu_read_lock(); 695 repeat: 696 page = NULL; 697 pagep = radix_tree_lookup_slot(&mapping->page_tree, offset); 698 if (pagep) { 699 page = radix_tree_deref_slot(pagep); 700 if (unlikely(!page)) 701 goto out; 702 if (radix_tree_exception(page)) { 703 if (radix_tree_deref_retry(page)) 704 goto repeat; 705 /* 706 * Otherwise, shmem/tmpfs must be storing a swap entry 707 * here as an exceptional entry: so return it without 708 * attempting to raise page count. 709 */ 710 goto out; 711 } 712 if (!page_cache_get_speculative(page)) 713 goto repeat; 714 715 /* 716 * Has the page moved? 717 * This is part of the lockless pagecache protocol. See 718 * include/linux/pagemap.h for details. 719 */ 720 if (unlikely(page != *pagep)) { 721 page_cache_release(page); 722 goto repeat; 723 } 724 } 725 out: 726 rcu_read_unlock(); 727 728 return page; 729 } 730 EXPORT_SYMBOL(find_get_page); 731 732 /** 733 * find_lock_page - locate, pin and lock a pagecache page 734 * @mapping: the address_space to search 735 * @offset: the page index 736 * 737 * Locates the desired pagecache page, locks it, increments its reference 738 * count and returns its address. 739 * 740 * Returns zero if the page was not present. find_lock_page() may sleep. 741 */ 742 struct page *find_lock_page(struct address_space *mapping, pgoff_t offset) 743 { 744 struct page *page; 745 746 repeat: 747 page = find_get_page(mapping, offset); 748 if (page && !radix_tree_exception(page)) { 749 lock_page(page); 750 /* Has the page been truncated? */ 751 if (unlikely(page->mapping != mapping)) { 752 unlock_page(page); 753 page_cache_release(page); 754 goto repeat; 755 } 756 VM_BUG_ON(page->index != offset); 757 } 758 return page; 759 } 760 EXPORT_SYMBOL(find_lock_page); 761 762 /** 763 * find_or_create_page - locate or add a pagecache page 764 * @mapping: the page's address_space 765 * @index: the page's index into the mapping 766 * @gfp_mask: page allocation mode 767 * 768 * Locates a page in the pagecache. If the page is not present, a new page 769 * is allocated using @gfp_mask and is added to the pagecache and to the VM's 770 * LRU list. The returned page is locked and has its reference count 771 * incremented. 772 * 773 * find_or_create_page() may sleep, even if @gfp_flags specifies an atomic 774 * allocation! 775 * 776 * find_or_create_page() returns the desired page's address, or zero on 777 * memory exhaustion. 778 */ 779 struct page *find_or_create_page(struct address_space *mapping, 780 pgoff_t index, gfp_t gfp_mask) 781 { 782 struct page *page; 783 int err; 784 repeat: 785 page = find_lock_page(mapping, index); 786 if (!page) { 787 page = __page_cache_alloc(gfp_mask); 788 if (!page) 789 return NULL; 790 /* 791 * We want a regular kernel memory (not highmem or DMA etc) 792 * allocation for the radix tree nodes, but we need to honour 793 * the context-specific requirements the caller has asked for. 794 * GFP_RECLAIM_MASK collects those requirements. 795 */ 796 err = add_to_page_cache_lru(page, mapping, index, 797 (gfp_mask & GFP_RECLAIM_MASK)); 798 if (unlikely(err)) { 799 page_cache_release(page); 800 page = NULL; 801 if (err == -EEXIST) 802 goto repeat; 803 } 804 } 805 return page; 806 } 807 EXPORT_SYMBOL(find_or_create_page); 808 809 /** 810 * find_get_pages - gang pagecache lookup 811 * @mapping: The address_space to search 812 * @start: The starting page index 813 * @nr_pages: The maximum number of pages 814 * @pages: Where the resulting pages are placed 815 * 816 * find_get_pages() will search for and return a group of up to 817 * @nr_pages pages in the mapping. The pages are placed at @pages. 818 * find_get_pages() takes a reference against the returned pages. 819 * 820 * The search returns a group of mapping-contiguous pages with ascending 821 * indexes. There may be holes in the indices due to not-present pages. 822 * 823 * find_get_pages() returns the number of pages which were found. 824 */ 825 unsigned find_get_pages(struct address_space *mapping, pgoff_t start, 826 unsigned int nr_pages, struct page **pages) 827 { 828 unsigned int i; 829 unsigned int ret; 830 unsigned int nr_found, nr_skip; 831 832 rcu_read_lock(); 833 restart: 834 nr_found = radix_tree_gang_lookup_slot(&mapping->page_tree, 835 (void ***)pages, NULL, start, nr_pages); 836 ret = 0; 837 nr_skip = 0; 838 for (i = 0; i < nr_found; i++) { 839 struct page *page; 840 repeat: 841 page = radix_tree_deref_slot((void **)pages[i]); 842 if (unlikely(!page)) 843 continue; 844 845 if (radix_tree_exception(page)) { 846 if (radix_tree_deref_retry(page)) { 847 /* 848 * Transient condition which can only trigger 849 * when entry at index 0 moves out of or back 850 * to root: none yet gotten, safe to restart. 851 */ 852 WARN_ON(start | i); 853 goto restart; 854 } 855 /* 856 * Otherwise, shmem/tmpfs must be storing a swap entry 857 * here as an exceptional entry: so skip over it - 858 * we only reach this from invalidate_mapping_pages(). 859 */ 860 nr_skip++; 861 continue; 862 } 863 864 if (!page_cache_get_speculative(page)) 865 goto repeat; 866 867 /* Has the page moved? */ 868 if (unlikely(page != *((void **)pages[i]))) { 869 page_cache_release(page); 870 goto repeat; 871 } 872 873 pages[ret] = page; 874 ret++; 875 } 876 877 /* 878 * If all entries were removed before we could secure them, 879 * try again, because callers stop trying once 0 is returned. 880 */ 881 if (unlikely(!ret && nr_found > nr_skip)) 882 goto restart; 883 rcu_read_unlock(); 884 return ret; 885 } 886 887 /** 888 * find_get_pages_contig - gang contiguous pagecache lookup 889 * @mapping: The address_space to search 890 * @index: The starting page index 891 * @nr_pages: The maximum number of pages 892 * @pages: Where the resulting pages are placed 893 * 894 * find_get_pages_contig() works exactly like find_get_pages(), except 895 * that the returned number of pages are guaranteed to be contiguous. 896 * 897 * find_get_pages_contig() returns the number of pages which were found. 898 */ 899 unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t index, 900 unsigned int nr_pages, struct page **pages) 901 { 902 unsigned int i; 903 unsigned int ret; 904 unsigned int nr_found; 905 906 rcu_read_lock(); 907 restart: 908 nr_found = radix_tree_gang_lookup_slot(&mapping->page_tree, 909 (void ***)pages, NULL, index, nr_pages); 910 ret = 0; 911 for (i = 0; i < nr_found; i++) { 912 struct page *page; 913 repeat: 914 page = radix_tree_deref_slot((void **)pages[i]); 915 if (unlikely(!page)) 916 continue; 917 918 if (radix_tree_exception(page)) { 919 if (radix_tree_deref_retry(page)) { 920 /* 921 * Transient condition which can only trigger 922 * when entry at index 0 moves out of or back 923 * to root: none yet gotten, safe to restart. 924 */ 925 goto restart; 926 } 927 /* 928 * Otherwise, shmem/tmpfs must be storing a swap entry 929 * here as an exceptional entry: so stop looking for 930 * contiguous pages. 931 */ 932 break; 933 } 934 935 if (!page_cache_get_speculative(page)) 936 goto repeat; 937 938 /* Has the page moved? */ 939 if (unlikely(page != *((void **)pages[i]))) { 940 page_cache_release(page); 941 goto repeat; 942 } 943 944 /* 945 * must check mapping and index after taking the ref. 946 * otherwise we can get both false positives and false 947 * negatives, which is just confusing to the caller. 948 */ 949 if (page->mapping == NULL || page->index != index) { 950 page_cache_release(page); 951 break; 952 } 953 954 pages[ret] = page; 955 ret++; 956 index++; 957 } 958 rcu_read_unlock(); 959 return ret; 960 } 961 EXPORT_SYMBOL(find_get_pages_contig); 962 963 /** 964 * find_get_pages_tag - find and return pages that match @tag 965 * @mapping: the address_space to search 966 * @index: the starting page index 967 * @tag: the tag index 968 * @nr_pages: the maximum number of pages 969 * @pages: where the resulting pages are placed 970 * 971 * Like find_get_pages, except we only return pages which are tagged with 972 * @tag. We update @index to index the next page for the traversal. 973 */ 974 unsigned find_get_pages_tag(struct address_space *mapping, pgoff_t *index, 975 int tag, unsigned int nr_pages, struct page **pages) 976 { 977 unsigned int i; 978 unsigned int ret; 979 unsigned int nr_found; 980 981 rcu_read_lock(); 982 restart: 983 nr_found = radix_tree_gang_lookup_tag_slot(&mapping->page_tree, 984 (void ***)pages, *index, nr_pages, tag); 985 ret = 0; 986 for (i = 0; i < nr_found; i++) { 987 struct page *page; 988 repeat: 989 page = radix_tree_deref_slot((void **)pages[i]); 990 if (unlikely(!page)) 991 continue; 992 993 if (radix_tree_exception(page)) { 994 if (radix_tree_deref_retry(page)) { 995 /* 996 * Transient condition which can only trigger 997 * when entry at index 0 moves out of or back 998 * to root: none yet gotten, safe to restart. 999 */ 1000 goto restart; 1001 } 1002 /* 1003 * This function is never used on a shmem/tmpfs 1004 * mapping, so a swap entry won't be found here. 1005 */ 1006 BUG(); 1007 } 1008 1009 if (!page_cache_get_speculative(page)) 1010 goto repeat; 1011 1012 /* Has the page moved? */ 1013 if (unlikely(page != *((void **)pages[i]))) { 1014 page_cache_release(page); 1015 goto repeat; 1016 } 1017 1018 pages[ret] = page; 1019 ret++; 1020 } 1021 1022 /* 1023 * If all entries were removed before we could secure them, 1024 * try again, because callers stop trying once 0 is returned. 1025 */ 1026 if (unlikely(!ret && nr_found)) 1027 goto restart; 1028 rcu_read_unlock(); 1029 1030 if (ret) 1031 *index = pages[ret - 1]->index + 1; 1032 1033 return ret; 1034 } 1035 EXPORT_SYMBOL(find_get_pages_tag); 1036 1037 /** 1038 * grab_cache_page_nowait - returns locked page at given index in given cache 1039 * @mapping: target address_space 1040 * @index: the page index 1041 * 1042 * Same as grab_cache_page(), but do not wait if the page is unavailable. 1043 * This is intended for speculative data generators, where the data can 1044 * be regenerated if the page couldn't be grabbed. This routine should 1045 * be safe to call while holding the lock for another page. 1046 * 1047 * Clear __GFP_FS when allocating the page to avoid recursion into the fs 1048 * and deadlock against the caller's locked page. 1049 */ 1050 struct page * 1051 grab_cache_page_nowait(struct address_space *mapping, pgoff_t index) 1052 { 1053 struct page *page = find_get_page(mapping, index); 1054 1055 if (page) { 1056 if (trylock_page(page)) 1057 return page; 1058 page_cache_release(page); 1059 return NULL; 1060 } 1061 page = __page_cache_alloc(mapping_gfp_mask(mapping) & ~__GFP_FS); 1062 if (page && add_to_page_cache_lru(page, mapping, index, GFP_NOFS)) { 1063 page_cache_release(page); 1064 page = NULL; 1065 } 1066 return page; 1067 } 1068 EXPORT_SYMBOL(grab_cache_page_nowait); 1069 1070 /* 1071 * CD/DVDs are error prone. When a medium error occurs, the driver may fail 1072 * a _large_ part of the i/o request. Imagine the worst scenario: 1073 * 1074 * ---R__________________________________________B__________ 1075 * ^ reading here ^ bad block(assume 4k) 1076 * 1077 * read(R) => miss => readahead(R...B) => media error => frustrating retries 1078 * => failing the whole request => read(R) => read(R+1) => 1079 * readahead(R+1...B+1) => bang => read(R+2) => read(R+3) => 1080 * readahead(R+3...B+2) => bang => read(R+3) => read(R+4) => 1081 * readahead(R+4...B+3) => bang => read(R+4) => read(R+5) => ...... 1082 * 1083 * It is going insane. Fix it by quickly scaling down the readahead size. 1084 */ 1085 static void shrink_readahead_size_eio(struct file *filp, 1086 struct file_ra_state *ra) 1087 { 1088 ra->ra_pages /= 4; 1089 } 1090 1091 /** 1092 * do_generic_file_read - generic file read routine 1093 * @filp: the file to read 1094 * @ppos: current file position 1095 * @desc: read_descriptor 1096 * @actor: read method 1097 * 1098 * This is a generic file read routine, and uses the 1099 * mapping->a_ops->readpage() function for the actual low-level stuff. 1100 * 1101 * This is really ugly. But the goto's actually try to clarify some 1102 * of the logic when it comes to error handling etc. 1103 */ 1104 static void do_generic_file_read(struct file *filp, loff_t *ppos, 1105 read_descriptor_t *desc, read_actor_t actor) 1106 { 1107 struct address_space *mapping = filp->f_mapping; 1108 struct inode *inode = mapping->host; 1109 struct file_ra_state *ra = &filp->f_ra; 1110 pgoff_t index; 1111 pgoff_t last_index; 1112 pgoff_t prev_index; 1113 unsigned long offset; /* offset into pagecache page */ 1114 unsigned int prev_offset; 1115 int error; 1116 1117 index = *ppos >> PAGE_CACHE_SHIFT; 1118 prev_index = ra->prev_pos >> PAGE_CACHE_SHIFT; 1119 prev_offset = ra->prev_pos & (PAGE_CACHE_SIZE-1); 1120 last_index = (*ppos + desc->count + PAGE_CACHE_SIZE-1) >> PAGE_CACHE_SHIFT; 1121 offset = *ppos & ~PAGE_CACHE_MASK; 1122 1123 for (;;) { 1124 struct page *page; 1125 pgoff_t end_index; 1126 loff_t isize; 1127 unsigned long nr, ret; 1128 1129 cond_resched(); 1130 find_page: 1131 page = find_get_page(mapping, index); 1132 if (!page) { 1133 page_cache_sync_readahead(mapping, 1134 ra, filp, 1135 index, last_index - index); 1136 page = find_get_page(mapping, index); 1137 if (unlikely(page == NULL)) 1138 goto no_cached_page; 1139 } 1140 if (PageReadahead(page)) { 1141 page_cache_async_readahead(mapping, 1142 ra, filp, page, 1143 index, last_index - index); 1144 } 1145 if (!PageUptodate(page)) { 1146 if (inode->i_blkbits == PAGE_CACHE_SHIFT || 1147 !mapping->a_ops->is_partially_uptodate) 1148 goto page_not_up_to_date; 1149 if (!trylock_page(page)) 1150 goto page_not_up_to_date; 1151 /* Did it get truncated before we got the lock? */ 1152 if (!page->mapping) 1153 goto page_not_up_to_date_locked; 1154 if (!mapping->a_ops->is_partially_uptodate(page, 1155 desc, offset)) 1156 goto page_not_up_to_date_locked; 1157 unlock_page(page); 1158 } 1159 page_ok: 1160 /* 1161 * i_size must be checked after we know the page is Uptodate. 1162 * 1163 * Checking i_size after the check allows us to calculate 1164 * the correct value for "nr", which means the zero-filled 1165 * part of the page is not copied back to userspace (unless 1166 * another truncate extends the file - this is desired though). 1167 */ 1168 1169 isize = i_size_read(inode); 1170 end_index = (isize - 1) >> PAGE_CACHE_SHIFT; 1171 if (unlikely(!isize || index > end_index)) { 1172 page_cache_release(page); 1173 goto out; 1174 } 1175 1176 /* nr is the maximum number of bytes to copy from this page */ 1177 nr = PAGE_CACHE_SIZE; 1178 if (index == end_index) { 1179 nr = ((isize - 1) & ~PAGE_CACHE_MASK) + 1; 1180 if (nr <= offset) { 1181 page_cache_release(page); 1182 goto out; 1183 } 1184 } 1185 nr = nr - offset; 1186 1187 /* If users can be writing to this page using arbitrary 1188 * virtual addresses, take care about potential aliasing 1189 * before reading the page on the kernel side. 1190 */ 1191 if (mapping_writably_mapped(mapping)) 1192 flush_dcache_page(page); 1193 1194 /* 1195 * When a sequential read accesses a page several times, 1196 * only mark it as accessed the first time. 1197 */ 1198 if (prev_index != index || offset != prev_offset) 1199 mark_page_accessed(page); 1200 prev_index = index; 1201 1202 /* 1203 * Ok, we have the page, and it's up-to-date, so 1204 * now we can copy it to user space... 1205 * 1206 * The actor routine returns how many bytes were actually used.. 1207 * NOTE! This may not be the same as how much of a user buffer 1208 * we filled up (we may be padding etc), so we can only update 1209 * "pos" here (the actor routine has to update the user buffer 1210 * pointers and the remaining count). 1211 */ 1212 ret = actor(desc, page, offset, nr); 1213 offset += ret; 1214 index += offset >> PAGE_CACHE_SHIFT; 1215 offset &= ~PAGE_CACHE_MASK; 1216 prev_offset = offset; 1217 1218 page_cache_release(page); 1219 if (ret == nr && desc->count) 1220 continue; 1221 goto out; 1222 1223 page_not_up_to_date: 1224 /* Get exclusive access to the page ... */ 1225 error = lock_page_killable(page); 1226 if (unlikely(error)) 1227 goto readpage_error; 1228 1229 page_not_up_to_date_locked: 1230 /* Did it get truncated before we got the lock? */ 1231 if (!page->mapping) { 1232 unlock_page(page); 1233 page_cache_release(page); 1234 continue; 1235 } 1236 1237 /* Did somebody else fill it already? */ 1238 if (PageUptodate(page)) { 1239 unlock_page(page); 1240 goto page_ok; 1241 } 1242 1243 readpage: 1244 /* 1245 * A previous I/O error may have been due to temporary 1246 * failures, eg. multipath errors. 1247 * PG_error will be set again if readpage fails. 1248 */ 1249 ClearPageError(page); 1250 /* Start the actual read. The read will unlock the page. */ 1251 error = mapping->a_ops->readpage(filp, page); 1252 1253 if (unlikely(error)) { 1254 if (error == AOP_TRUNCATED_PAGE) { 1255 page_cache_release(page); 1256 goto find_page; 1257 } 1258 goto readpage_error; 1259 } 1260 1261 if (!PageUptodate(page)) { 1262 error = lock_page_killable(page); 1263 if (unlikely(error)) 1264 goto readpage_error; 1265 if (!PageUptodate(page)) { 1266 if (page->mapping == NULL) { 1267 /* 1268 * invalidate_mapping_pages got it 1269 */ 1270 unlock_page(page); 1271 page_cache_release(page); 1272 goto find_page; 1273 } 1274 unlock_page(page); 1275 shrink_readahead_size_eio(filp, ra); 1276 error = -EIO; 1277 goto readpage_error; 1278 } 1279 unlock_page(page); 1280 } 1281 1282 goto page_ok; 1283 1284 readpage_error: 1285 /* UHHUH! A synchronous read error occurred. Report it */ 1286 desc->error = error; 1287 page_cache_release(page); 1288 goto out; 1289 1290 no_cached_page: 1291 /* 1292 * Ok, it wasn't cached, so we need to create a new 1293 * page.. 1294 */ 1295 page = page_cache_alloc_cold(mapping); 1296 if (!page) { 1297 desc->error = -ENOMEM; 1298 goto out; 1299 } 1300 error = add_to_page_cache_lru(page, mapping, 1301 index, GFP_KERNEL); 1302 if (error) { 1303 page_cache_release(page); 1304 if (error == -EEXIST) 1305 goto find_page; 1306 desc->error = error; 1307 goto out; 1308 } 1309 goto readpage; 1310 } 1311 1312 out: 1313 ra->prev_pos = prev_index; 1314 ra->prev_pos <<= PAGE_CACHE_SHIFT; 1315 ra->prev_pos |= prev_offset; 1316 1317 *ppos = ((loff_t)index << PAGE_CACHE_SHIFT) + offset; 1318 file_accessed(filp); 1319 } 1320 1321 int file_read_actor(read_descriptor_t *desc, struct page *page, 1322 unsigned long offset, unsigned long size) 1323 { 1324 char *kaddr; 1325 unsigned long left, count = desc->count; 1326 1327 if (size > count) 1328 size = count; 1329 1330 /* 1331 * Faults on the destination of a read are common, so do it before 1332 * taking the kmap. 1333 */ 1334 if (!fault_in_pages_writeable(desc->arg.buf, size)) { 1335 kaddr = kmap_atomic(page, KM_USER0); 1336 left = __copy_to_user_inatomic(desc->arg.buf, 1337 kaddr + offset, size); 1338 kunmap_atomic(kaddr, KM_USER0); 1339 if (left == 0) 1340 goto success; 1341 } 1342 1343 /* Do it the slow way */ 1344 kaddr = kmap(page); 1345 left = __copy_to_user(desc->arg.buf, kaddr + offset, size); 1346 kunmap(page); 1347 1348 if (left) { 1349 size -= left; 1350 desc->error = -EFAULT; 1351 } 1352 success: 1353 desc->count = count - size; 1354 desc->written += size; 1355 desc->arg.buf += size; 1356 return size; 1357 } 1358 1359 /* 1360 * Performs necessary checks before doing a write 1361 * @iov: io vector request 1362 * @nr_segs: number of segments in the iovec 1363 * @count: number of bytes to write 1364 * @access_flags: type of access: %VERIFY_READ or %VERIFY_WRITE 1365 * 1366 * Adjust number of segments and amount of bytes to write (nr_segs should be 1367 * properly initialized first). Returns appropriate error code that caller 1368 * should return or zero in case that write should be allowed. 1369 */ 1370 int generic_segment_checks(const struct iovec *iov, 1371 unsigned long *nr_segs, size_t *count, int access_flags) 1372 { 1373 unsigned long seg; 1374 size_t cnt = 0; 1375 for (seg = 0; seg < *nr_segs; seg++) { 1376 const struct iovec *iv = &iov[seg]; 1377 1378 /* 1379 * If any segment has a negative length, or the cumulative 1380 * length ever wraps negative then return -EINVAL. 1381 */ 1382 cnt += iv->iov_len; 1383 if (unlikely((ssize_t)(cnt|iv->iov_len) < 0)) 1384 return -EINVAL; 1385 if (access_ok(access_flags, iv->iov_base, iv->iov_len)) 1386 continue; 1387 if (seg == 0) 1388 return -EFAULT; 1389 *nr_segs = seg; 1390 cnt -= iv->iov_len; /* This segment is no good */ 1391 break; 1392 } 1393 *count = cnt; 1394 return 0; 1395 } 1396 EXPORT_SYMBOL(generic_segment_checks); 1397 1398 /** 1399 * generic_file_aio_read - generic filesystem read routine 1400 * @iocb: kernel I/O control block 1401 * @iov: io vector request 1402 * @nr_segs: number of segments in the iovec 1403 * @pos: current file position 1404 * 1405 * This is the "read()" routine for all filesystems 1406 * that can use the page cache directly. 1407 */ 1408 ssize_t 1409 generic_file_aio_read(struct kiocb *iocb, const struct iovec *iov, 1410 unsigned long nr_segs, loff_t pos) 1411 { 1412 struct file *filp = iocb->ki_filp; 1413 ssize_t retval; 1414 unsigned long seg = 0; 1415 size_t count; 1416 loff_t *ppos = &iocb->ki_pos; 1417 struct blk_plug plug; 1418 1419 count = 0; 1420 retval = generic_segment_checks(iov, &nr_segs, &count, VERIFY_WRITE); 1421 if (retval) 1422 return retval; 1423 1424 blk_start_plug(&plug); 1425 1426 /* coalesce the iovecs and go direct-to-BIO for O_DIRECT */ 1427 if (filp->f_flags & O_DIRECT) { 1428 loff_t size; 1429 struct address_space *mapping; 1430 struct inode *inode; 1431 1432 mapping = filp->f_mapping; 1433 inode = mapping->host; 1434 if (!count) 1435 goto out; /* skip atime */ 1436 size = i_size_read(inode); 1437 if (pos < size) { 1438 retval = filemap_write_and_wait_range(mapping, pos, 1439 pos + iov_length(iov, nr_segs) - 1); 1440 if (!retval) { 1441 retval = mapping->a_ops->direct_IO(READ, iocb, 1442 iov, pos, nr_segs); 1443 } 1444 if (retval > 0) { 1445 *ppos = pos + retval; 1446 count -= retval; 1447 } 1448 1449 /* 1450 * Btrfs can have a short DIO read if we encounter 1451 * compressed extents, so if there was an error, or if 1452 * we've already read everything we wanted to, or if 1453 * there was a short read because we hit EOF, go ahead 1454 * and return. Otherwise fallthrough to buffered io for 1455 * the rest of the read. 1456 */ 1457 if (retval < 0 || !count || *ppos >= size) { 1458 file_accessed(filp); 1459 goto out; 1460 } 1461 } 1462 } 1463 1464 count = retval; 1465 for (seg = 0; seg < nr_segs; seg++) { 1466 read_descriptor_t desc; 1467 loff_t offset = 0; 1468 1469 /* 1470 * If we did a short DIO read we need to skip the section of the 1471 * iov that we've already read data into. 1472 */ 1473 if (count) { 1474 if (count > iov[seg].iov_len) { 1475 count -= iov[seg].iov_len; 1476 continue; 1477 } 1478 offset = count; 1479 count = 0; 1480 } 1481 1482 desc.written = 0; 1483 desc.arg.buf = iov[seg].iov_base + offset; 1484 desc.count = iov[seg].iov_len - offset; 1485 if (desc.count == 0) 1486 continue; 1487 desc.error = 0; 1488 do_generic_file_read(filp, ppos, &desc, file_read_actor); 1489 retval += desc.written; 1490 if (desc.error) { 1491 retval = retval ?: desc.error; 1492 break; 1493 } 1494 if (desc.count > 0) 1495 break; 1496 } 1497 out: 1498 blk_finish_plug(&plug); 1499 return retval; 1500 } 1501 EXPORT_SYMBOL(generic_file_aio_read); 1502 1503 static ssize_t 1504 do_readahead(struct address_space *mapping, struct file *filp, 1505 pgoff_t index, unsigned long nr) 1506 { 1507 if (!mapping || !mapping->a_ops || !mapping->a_ops->readpage) 1508 return -EINVAL; 1509 1510 force_page_cache_readahead(mapping, filp, index, nr); 1511 return 0; 1512 } 1513 1514 SYSCALL_DEFINE(readahead)(int fd, loff_t offset, size_t count) 1515 { 1516 ssize_t ret; 1517 struct file *file; 1518 1519 ret = -EBADF; 1520 file = fget(fd); 1521 if (file) { 1522 if (file->f_mode & FMODE_READ) { 1523 struct address_space *mapping = file->f_mapping; 1524 pgoff_t start = offset >> PAGE_CACHE_SHIFT; 1525 pgoff_t end = (offset + count - 1) >> PAGE_CACHE_SHIFT; 1526 unsigned long len = end - start + 1; 1527 ret = do_readahead(mapping, file, start, len); 1528 } 1529 fput(file); 1530 } 1531 return ret; 1532 } 1533 #ifdef CONFIG_HAVE_SYSCALL_WRAPPERS 1534 asmlinkage long SyS_readahead(long fd, loff_t offset, long count) 1535 { 1536 return SYSC_readahead((int) fd, offset, (size_t) count); 1537 } 1538 SYSCALL_ALIAS(sys_readahead, SyS_readahead); 1539 #endif 1540 1541 #ifdef CONFIG_MMU 1542 /** 1543 * page_cache_read - adds requested page to the page cache if not already there 1544 * @file: file to read 1545 * @offset: page index 1546 * 1547 * This adds the requested page to the page cache if it isn't already there, 1548 * and schedules an I/O to read in its contents from disk. 1549 */ 1550 static int page_cache_read(struct file *file, pgoff_t offset) 1551 { 1552 struct address_space *mapping = file->f_mapping; 1553 struct page *page; 1554 int ret; 1555 1556 do { 1557 page = page_cache_alloc_cold(mapping); 1558 if (!page) 1559 return -ENOMEM; 1560 1561 ret = add_to_page_cache_lru(page, mapping, offset, GFP_KERNEL); 1562 if (ret == 0) 1563 ret = mapping->a_ops->readpage(file, page); 1564 else if (ret == -EEXIST) 1565 ret = 0; /* losing race to add is OK */ 1566 1567 page_cache_release(page); 1568 1569 } while (ret == AOP_TRUNCATED_PAGE); 1570 1571 return ret; 1572 } 1573 1574 #define MMAP_LOTSAMISS (100) 1575 1576 /* 1577 * Synchronous readahead happens when we don't even find 1578 * a page in the page cache at all. 1579 */ 1580 static void do_sync_mmap_readahead(struct vm_area_struct *vma, 1581 struct file_ra_state *ra, 1582 struct file *file, 1583 pgoff_t offset) 1584 { 1585 unsigned long ra_pages; 1586 struct address_space *mapping = file->f_mapping; 1587 1588 /* If we don't want any read-ahead, don't bother */ 1589 if (VM_RandomReadHint(vma)) 1590 return; 1591 if (!ra->ra_pages) 1592 return; 1593 1594 if (VM_SequentialReadHint(vma)) { 1595 page_cache_sync_readahead(mapping, ra, file, offset, 1596 ra->ra_pages); 1597 return; 1598 } 1599 1600 /* Avoid banging the cache line if not needed */ 1601 if (ra->mmap_miss < MMAP_LOTSAMISS * 10) 1602 ra->mmap_miss++; 1603 1604 /* 1605 * Do we miss much more than hit in this file? If so, 1606 * stop bothering with read-ahead. It will only hurt. 1607 */ 1608 if (ra->mmap_miss > MMAP_LOTSAMISS) 1609 return; 1610 1611 /* 1612 * mmap read-around 1613 */ 1614 ra_pages = max_sane_readahead(ra->ra_pages); 1615 ra->start = max_t(long, 0, offset - ra_pages / 2); 1616 ra->size = ra_pages; 1617 ra->async_size = ra_pages / 4; 1618 ra_submit(ra, mapping, file); 1619 } 1620 1621 /* 1622 * Asynchronous readahead happens when we find the page and PG_readahead, 1623 * so we want to possibly extend the readahead further.. 1624 */ 1625 static void do_async_mmap_readahead(struct vm_area_struct *vma, 1626 struct file_ra_state *ra, 1627 struct file *file, 1628 struct page *page, 1629 pgoff_t offset) 1630 { 1631 struct address_space *mapping = file->f_mapping; 1632 1633 /* If we don't want any read-ahead, don't bother */ 1634 if (VM_RandomReadHint(vma)) 1635 return; 1636 if (ra->mmap_miss > 0) 1637 ra->mmap_miss--; 1638 if (PageReadahead(page)) 1639 page_cache_async_readahead(mapping, ra, file, 1640 page, offset, ra->ra_pages); 1641 } 1642 1643 /** 1644 * filemap_fault - read in file data for page fault handling 1645 * @vma: vma in which the fault was taken 1646 * @vmf: struct vm_fault containing details of the fault 1647 * 1648 * filemap_fault() is invoked via the vma operations vector for a 1649 * mapped memory region to read in file data during a page fault. 1650 * 1651 * The goto's are kind of ugly, but this streamlines the normal case of having 1652 * it in the page cache, and handles the special cases reasonably without 1653 * having a lot of duplicated code. 1654 */ 1655 int filemap_fault(struct vm_area_struct *vma, struct vm_fault *vmf) 1656 { 1657 int error; 1658 struct file *file = vma->vm_file; 1659 struct address_space *mapping = file->f_mapping; 1660 struct file_ra_state *ra = &file->f_ra; 1661 struct inode *inode = mapping->host; 1662 pgoff_t offset = vmf->pgoff; 1663 struct page *page; 1664 pgoff_t size; 1665 int ret = 0; 1666 1667 size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT; 1668 if (offset >= size) 1669 return VM_FAULT_SIGBUS; 1670 1671 /* 1672 * Do we have something in the page cache already? 1673 */ 1674 page = find_get_page(mapping, offset); 1675 if (likely(page)) { 1676 /* 1677 * We found the page, so try async readahead before 1678 * waiting for the lock. 1679 */ 1680 do_async_mmap_readahead(vma, ra, file, page, offset); 1681 } else { 1682 /* No page in the page cache at all */ 1683 do_sync_mmap_readahead(vma, ra, file, offset); 1684 count_vm_event(PGMAJFAULT); 1685 mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT); 1686 ret = VM_FAULT_MAJOR; 1687 retry_find: 1688 page = find_get_page(mapping, offset); 1689 if (!page) 1690 goto no_cached_page; 1691 } 1692 1693 if (!lock_page_or_retry(page, vma->vm_mm, vmf->flags)) { 1694 page_cache_release(page); 1695 return ret | VM_FAULT_RETRY; 1696 } 1697 1698 /* Did it get truncated? */ 1699 if (unlikely(page->mapping != mapping)) { 1700 unlock_page(page); 1701 put_page(page); 1702 goto retry_find; 1703 } 1704 VM_BUG_ON(page->index != offset); 1705 1706 /* 1707 * We have a locked page in the page cache, now we need to check 1708 * that it's up-to-date. If not, it is going to be due to an error. 1709 */ 1710 if (unlikely(!PageUptodate(page))) 1711 goto page_not_uptodate; 1712 1713 /* 1714 * Found the page and have a reference on it. 1715 * We must recheck i_size under page lock. 1716 */ 1717 size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT; 1718 if (unlikely(offset >= size)) { 1719 unlock_page(page); 1720 page_cache_release(page); 1721 return VM_FAULT_SIGBUS; 1722 } 1723 1724 vmf->page = page; 1725 return ret | VM_FAULT_LOCKED; 1726 1727 no_cached_page: 1728 /* 1729 * We're only likely to ever get here if MADV_RANDOM is in 1730 * effect. 1731 */ 1732 error = page_cache_read(file, offset); 1733 1734 /* 1735 * The page we want has now been added to the page cache. 1736 * In the unlikely event that someone removed it in the 1737 * meantime, we'll just come back here and read it again. 1738 */ 1739 if (error >= 0) 1740 goto retry_find; 1741 1742 /* 1743 * An error return from page_cache_read can result if the 1744 * system is low on memory, or a problem occurs while trying 1745 * to schedule I/O. 1746 */ 1747 if (error == -ENOMEM) 1748 return VM_FAULT_OOM; 1749 return VM_FAULT_SIGBUS; 1750 1751 page_not_uptodate: 1752 /* 1753 * Umm, take care of errors if the page isn't up-to-date. 1754 * Try to re-read it _once_. We do this synchronously, 1755 * because there really aren't any performance issues here 1756 * and we need to check for errors. 1757 */ 1758 ClearPageError(page); 1759 error = mapping->a_ops->readpage(file, page); 1760 if (!error) { 1761 wait_on_page_locked(page); 1762 if (!PageUptodate(page)) 1763 error = -EIO; 1764 } 1765 page_cache_release(page); 1766 1767 if (!error || error == AOP_TRUNCATED_PAGE) 1768 goto retry_find; 1769 1770 /* Things didn't work out. Return zero to tell the mm layer so. */ 1771 shrink_readahead_size_eio(file, ra); 1772 return VM_FAULT_SIGBUS; 1773 } 1774 EXPORT_SYMBOL(filemap_fault); 1775 1776 const struct vm_operations_struct generic_file_vm_ops = { 1777 .fault = filemap_fault, 1778 }; 1779 1780 /* This is used for a general mmap of a disk file */ 1781 1782 int generic_file_mmap(struct file * file, struct vm_area_struct * vma) 1783 { 1784 struct address_space *mapping = file->f_mapping; 1785 1786 if (!mapping->a_ops->readpage) 1787 return -ENOEXEC; 1788 file_accessed(file); 1789 vma->vm_ops = &generic_file_vm_ops; 1790 vma->vm_flags |= VM_CAN_NONLINEAR; 1791 return 0; 1792 } 1793 1794 /* 1795 * This is for filesystems which do not implement ->writepage. 1796 */ 1797 int generic_file_readonly_mmap(struct file *file, struct vm_area_struct *vma) 1798 { 1799 if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_MAYWRITE)) 1800 return -EINVAL; 1801 return generic_file_mmap(file, vma); 1802 } 1803 #else 1804 int generic_file_mmap(struct file * file, struct vm_area_struct * vma) 1805 { 1806 return -ENOSYS; 1807 } 1808 int generic_file_readonly_mmap(struct file * file, struct vm_area_struct * vma) 1809 { 1810 return -ENOSYS; 1811 } 1812 #endif /* CONFIG_MMU */ 1813 1814 EXPORT_SYMBOL(generic_file_mmap); 1815 EXPORT_SYMBOL(generic_file_readonly_mmap); 1816 1817 static struct page *__read_cache_page(struct address_space *mapping, 1818 pgoff_t index, 1819 int (*filler)(void *, struct page *), 1820 void *data, 1821 gfp_t gfp) 1822 { 1823 struct page *page; 1824 int err; 1825 repeat: 1826 page = find_get_page(mapping, index); 1827 if (!page) { 1828 page = __page_cache_alloc(gfp | __GFP_COLD); 1829 if (!page) 1830 return ERR_PTR(-ENOMEM); 1831 err = add_to_page_cache_lru(page, mapping, index, GFP_KERNEL); 1832 if (unlikely(err)) { 1833 page_cache_release(page); 1834 if (err == -EEXIST) 1835 goto repeat; 1836 /* Presumably ENOMEM for radix tree node */ 1837 return ERR_PTR(err); 1838 } 1839 err = filler(data, page); 1840 if (err < 0) { 1841 page_cache_release(page); 1842 page = ERR_PTR(err); 1843 } 1844 } 1845 return page; 1846 } 1847 1848 static struct page *do_read_cache_page(struct address_space *mapping, 1849 pgoff_t index, 1850 int (*filler)(void *, struct page *), 1851 void *data, 1852 gfp_t gfp) 1853 1854 { 1855 struct page *page; 1856 int err; 1857 1858 retry: 1859 page = __read_cache_page(mapping, index, filler, data, gfp); 1860 if (IS_ERR(page)) 1861 return page; 1862 if (PageUptodate(page)) 1863 goto out; 1864 1865 lock_page(page); 1866 if (!page->mapping) { 1867 unlock_page(page); 1868 page_cache_release(page); 1869 goto retry; 1870 } 1871 if (PageUptodate(page)) { 1872 unlock_page(page); 1873 goto out; 1874 } 1875 err = filler(data, page); 1876 if (err < 0) { 1877 page_cache_release(page); 1878 return ERR_PTR(err); 1879 } 1880 out: 1881 mark_page_accessed(page); 1882 return page; 1883 } 1884 1885 /** 1886 * read_cache_page_async - read into page cache, fill it if needed 1887 * @mapping: the page's address_space 1888 * @index: the page index 1889 * @filler: function to perform the read 1890 * @data: first arg to filler(data, page) function, often left as NULL 1891 * 1892 * Same as read_cache_page, but don't wait for page to become unlocked 1893 * after submitting it to the filler. 1894 * 1895 * Read into the page cache. If a page already exists, and PageUptodate() is 1896 * not set, try to fill the page but don't wait for it to become unlocked. 1897 * 1898 * If the page does not get brought uptodate, return -EIO. 1899 */ 1900 struct page *read_cache_page_async(struct address_space *mapping, 1901 pgoff_t index, 1902 int (*filler)(void *, struct page *), 1903 void *data) 1904 { 1905 return do_read_cache_page(mapping, index, filler, data, mapping_gfp_mask(mapping)); 1906 } 1907 EXPORT_SYMBOL(read_cache_page_async); 1908 1909 static struct page *wait_on_page_read(struct page *page) 1910 { 1911 if (!IS_ERR(page)) { 1912 wait_on_page_locked(page); 1913 if (!PageUptodate(page)) { 1914 page_cache_release(page); 1915 page = ERR_PTR(-EIO); 1916 } 1917 } 1918 return page; 1919 } 1920 1921 /** 1922 * read_cache_page_gfp - read into page cache, using specified page allocation flags. 1923 * @mapping: the page's address_space 1924 * @index: the page index 1925 * @gfp: the page allocator flags to use if allocating 1926 * 1927 * This is the same as "read_mapping_page(mapping, index, NULL)", but with 1928 * any new page allocations done using the specified allocation flags. Note 1929 * that the Radix tree operations will still use GFP_KERNEL, so you can't 1930 * expect to do this atomically or anything like that - but you can pass in 1931 * other page requirements. 1932 * 1933 * If the page does not get brought uptodate, return -EIO. 1934 */ 1935 struct page *read_cache_page_gfp(struct address_space *mapping, 1936 pgoff_t index, 1937 gfp_t gfp) 1938 { 1939 filler_t *filler = (filler_t *)mapping->a_ops->readpage; 1940 1941 return wait_on_page_read(do_read_cache_page(mapping, index, filler, NULL, gfp)); 1942 } 1943 EXPORT_SYMBOL(read_cache_page_gfp); 1944 1945 /** 1946 * read_cache_page - read into page cache, fill it if needed 1947 * @mapping: the page's address_space 1948 * @index: the page index 1949 * @filler: function to perform the read 1950 * @data: first arg to filler(data, page) function, often left as NULL 1951 * 1952 * Read into the page cache. If a page already exists, and PageUptodate() is 1953 * not set, try to fill the page then wait for it to become unlocked. 1954 * 1955 * If the page does not get brought uptodate, return -EIO. 1956 */ 1957 struct page *read_cache_page(struct address_space *mapping, 1958 pgoff_t index, 1959 int (*filler)(void *, struct page *), 1960 void *data) 1961 { 1962 return wait_on_page_read(read_cache_page_async(mapping, index, filler, data)); 1963 } 1964 EXPORT_SYMBOL(read_cache_page); 1965 1966 /* 1967 * The logic we want is 1968 * 1969 * if suid or (sgid and xgrp) 1970 * remove privs 1971 */ 1972 int should_remove_suid(struct dentry *dentry) 1973 { 1974 mode_t mode = dentry->d_inode->i_mode; 1975 int kill = 0; 1976 1977 /* suid always must be killed */ 1978 if (unlikely(mode & S_ISUID)) 1979 kill = ATTR_KILL_SUID; 1980 1981 /* 1982 * sgid without any exec bits is just a mandatory locking mark; leave 1983 * it alone. If some exec bits are set, it's a real sgid; kill it. 1984 */ 1985 if (unlikely((mode & S_ISGID) && (mode & S_IXGRP))) 1986 kill |= ATTR_KILL_SGID; 1987 1988 if (unlikely(kill && !capable(CAP_FSETID) && S_ISREG(mode))) 1989 return kill; 1990 1991 return 0; 1992 } 1993 EXPORT_SYMBOL(should_remove_suid); 1994 1995 static int __remove_suid(struct dentry *dentry, int kill) 1996 { 1997 struct iattr newattrs; 1998 1999 newattrs.ia_valid = ATTR_FORCE | kill; 2000 return notify_change(dentry, &newattrs); 2001 } 2002 2003 int file_remove_suid(struct file *file) 2004 { 2005 struct dentry *dentry = file->f_path.dentry; 2006 struct inode *inode = dentry->d_inode; 2007 int killsuid; 2008 int killpriv; 2009 int error = 0; 2010 2011 /* Fast path for nothing security related */ 2012 if (IS_NOSEC(inode)) 2013 return 0; 2014 2015 killsuid = should_remove_suid(dentry); 2016 killpriv = security_inode_need_killpriv(dentry); 2017 2018 if (killpriv < 0) 2019 return killpriv; 2020 if (killpriv) 2021 error = security_inode_killpriv(dentry); 2022 if (!error && killsuid) 2023 error = __remove_suid(dentry, killsuid); 2024 if (!error && (inode->i_sb->s_flags & MS_NOSEC)) 2025 inode->i_flags |= S_NOSEC; 2026 2027 return error; 2028 } 2029 EXPORT_SYMBOL(file_remove_suid); 2030 2031 static size_t __iovec_copy_from_user_inatomic(char *vaddr, 2032 const struct iovec *iov, size_t base, size_t bytes) 2033 { 2034 size_t copied = 0, left = 0; 2035 2036 while (bytes) { 2037 char __user *buf = iov->iov_base + base; 2038 int copy = min(bytes, iov->iov_len - base); 2039 2040 base = 0; 2041 left = __copy_from_user_inatomic(vaddr, buf, copy); 2042 copied += copy; 2043 bytes -= copy; 2044 vaddr += copy; 2045 iov++; 2046 2047 if (unlikely(left)) 2048 break; 2049 } 2050 return copied - left; 2051 } 2052 2053 /* 2054 * Copy as much as we can into the page and return the number of bytes which 2055 * were successfully copied. If a fault is encountered then return the number of 2056 * bytes which were copied. 2057 */ 2058 size_t iov_iter_copy_from_user_atomic(struct page *page, 2059 struct iov_iter *i, unsigned long offset, size_t bytes) 2060 { 2061 char *kaddr; 2062 size_t copied; 2063 2064 BUG_ON(!in_atomic()); 2065 kaddr = kmap_atomic(page, KM_USER0); 2066 if (likely(i->nr_segs == 1)) { 2067 int left; 2068 char __user *buf = i->iov->iov_base + i->iov_offset; 2069 left = __copy_from_user_inatomic(kaddr + offset, buf, bytes); 2070 copied = bytes - left; 2071 } else { 2072 copied = __iovec_copy_from_user_inatomic(kaddr + offset, 2073 i->iov, i->iov_offset, bytes); 2074 } 2075 kunmap_atomic(kaddr, KM_USER0); 2076 2077 return copied; 2078 } 2079 EXPORT_SYMBOL(iov_iter_copy_from_user_atomic); 2080 2081 /* 2082 * This has the same sideeffects and return value as 2083 * iov_iter_copy_from_user_atomic(). 2084 * The difference is that it attempts to resolve faults. 2085 * Page must not be locked. 2086 */ 2087 size_t iov_iter_copy_from_user(struct page *page, 2088 struct iov_iter *i, unsigned long offset, size_t bytes) 2089 { 2090 char *kaddr; 2091 size_t copied; 2092 2093 kaddr = kmap(page); 2094 if (likely(i->nr_segs == 1)) { 2095 int left; 2096 char __user *buf = i->iov->iov_base + i->iov_offset; 2097 left = __copy_from_user(kaddr + offset, buf, bytes); 2098 copied = bytes - left; 2099 } else { 2100 copied = __iovec_copy_from_user_inatomic(kaddr + offset, 2101 i->iov, i->iov_offset, bytes); 2102 } 2103 kunmap(page); 2104 return copied; 2105 } 2106 EXPORT_SYMBOL(iov_iter_copy_from_user); 2107 2108 void iov_iter_advance(struct iov_iter *i, size_t bytes) 2109 { 2110 BUG_ON(i->count < bytes); 2111 2112 if (likely(i->nr_segs == 1)) { 2113 i->iov_offset += bytes; 2114 i->count -= bytes; 2115 } else { 2116 const struct iovec *iov = i->iov; 2117 size_t base = i->iov_offset; 2118 2119 /* 2120 * The !iov->iov_len check ensures we skip over unlikely 2121 * zero-length segments (without overruning the iovec). 2122 */ 2123 while (bytes || unlikely(i->count && !iov->iov_len)) { 2124 int copy; 2125 2126 copy = min(bytes, iov->iov_len - base); 2127 BUG_ON(!i->count || i->count < copy); 2128 i->count -= copy; 2129 bytes -= copy; 2130 base += copy; 2131 if (iov->iov_len == base) { 2132 iov++; 2133 base = 0; 2134 } 2135 } 2136 i->iov = iov; 2137 i->iov_offset = base; 2138 } 2139 } 2140 EXPORT_SYMBOL(iov_iter_advance); 2141 2142 /* 2143 * Fault in the first iovec of the given iov_iter, to a maximum length 2144 * of bytes. Returns 0 on success, or non-zero if the memory could not be 2145 * accessed (ie. because it is an invalid address). 2146 * 2147 * writev-intensive code may want this to prefault several iovecs -- that 2148 * would be possible (callers must not rely on the fact that _only_ the 2149 * first iovec will be faulted with the current implementation). 2150 */ 2151 int iov_iter_fault_in_readable(struct iov_iter *i, size_t bytes) 2152 { 2153 char __user *buf = i->iov->iov_base + i->iov_offset; 2154 bytes = min(bytes, i->iov->iov_len - i->iov_offset); 2155 return fault_in_pages_readable(buf, bytes); 2156 } 2157 EXPORT_SYMBOL(iov_iter_fault_in_readable); 2158 2159 /* 2160 * Return the count of just the current iov_iter segment. 2161 */ 2162 size_t iov_iter_single_seg_count(struct iov_iter *i) 2163 { 2164 const struct iovec *iov = i->iov; 2165 if (i->nr_segs == 1) 2166 return i->count; 2167 else 2168 return min(i->count, iov->iov_len - i->iov_offset); 2169 } 2170 EXPORT_SYMBOL(iov_iter_single_seg_count); 2171 2172 /* 2173 * Performs necessary checks before doing a write 2174 * 2175 * Can adjust writing position or amount of bytes to write. 2176 * Returns appropriate error code that caller should return or 2177 * zero in case that write should be allowed. 2178 */ 2179 inline int generic_write_checks(struct file *file, loff_t *pos, size_t *count, int isblk) 2180 { 2181 struct inode *inode = file->f_mapping->host; 2182 unsigned long limit = rlimit(RLIMIT_FSIZE); 2183 2184 if (unlikely(*pos < 0)) 2185 return -EINVAL; 2186 2187 if (!isblk) { 2188 /* FIXME: this is for backwards compatibility with 2.4 */ 2189 if (file->f_flags & O_APPEND) 2190 *pos = i_size_read(inode); 2191 2192 if (limit != RLIM_INFINITY) { 2193 if (*pos >= limit) { 2194 send_sig(SIGXFSZ, current, 0); 2195 return -EFBIG; 2196 } 2197 if (*count > limit - (typeof(limit))*pos) { 2198 *count = limit - (typeof(limit))*pos; 2199 } 2200 } 2201 } 2202 2203 /* 2204 * LFS rule 2205 */ 2206 if (unlikely(*pos + *count > MAX_NON_LFS && 2207 !(file->f_flags & O_LARGEFILE))) { 2208 if (*pos >= MAX_NON_LFS) { 2209 return -EFBIG; 2210 } 2211 if (*count > MAX_NON_LFS - (unsigned long)*pos) { 2212 *count = MAX_NON_LFS - (unsigned long)*pos; 2213 } 2214 } 2215 2216 /* 2217 * Are we about to exceed the fs block limit ? 2218 * 2219 * If we have written data it becomes a short write. If we have 2220 * exceeded without writing data we send a signal and return EFBIG. 2221 * Linus frestrict idea will clean these up nicely.. 2222 */ 2223 if (likely(!isblk)) { 2224 if (unlikely(*pos >= inode->i_sb->s_maxbytes)) { 2225 if (*count || *pos > inode->i_sb->s_maxbytes) { 2226 return -EFBIG; 2227 } 2228 /* zero-length writes at ->s_maxbytes are OK */ 2229 } 2230 2231 if (unlikely(*pos + *count > inode->i_sb->s_maxbytes)) 2232 *count = inode->i_sb->s_maxbytes - *pos; 2233 } else { 2234 #ifdef CONFIG_BLOCK 2235 loff_t isize; 2236 if (bdev_read_only(I_BDEV(inode))) 2237 return -EPERM; 2238 isize = i_size_read(inode); 2239 if (*pos >= isize) { 2240 if (*count || *pos > isize) 2241 return -ENOSPC; 2242 } 2243 2244 if (*pos + *count > isize) 2245 *count = isize - *pos; 2246 #else 2247 return -EPERM; 2248 #endif 2249 } 2250 return 0; 2251 } 2252 EXPORT_SYMBOL(generic_write_checks); 2253 2254 int pagecache_write_begin(struct file *file, struct address_space *mapping, 2255 loff_t pos, unsigned len, unsigned flags, 2256 struct page **pagep, void **fsdata) 2257 { 2258 const struct address_space_operations *aops = mapping->a_ops; 2259 2260 return aops->write_begin(file, mapping, pos, len, flags, 2261 pagep, fsdata); 2262 } 2263 EXPORT_SYMBOL(pagecache_write_begin); 2264 2265 int pagecache_write_end(struct file *file, struct address_space *mapping, 2266 loff_t pos, unsigned len, unsigned copied, 2267 struct page *page, void *fsdata) 2268 { 2269 const struct address_space_operations *aops = mapping->a_ops; 2270 2271 mark_page_accessed(page); 2272 return aops->write_end(file, mapping, pos, len, copied, page, fsdata); 2273 } 2274 EXPORT_SYMBOL(pagecache_write_end); 2275 2276 ssize_t 2277 generic_file_direct_write(struct kiocb *iocb, const struct iovec *iov, 2278 unsigned long *nr_segs, loff_t pos, loff_t *ppos, 2279 size_t count, size_t ocount) 2280 { 2281 struct file *file = iocb->ki_filp; 2282 struct address_space *mapping = file->f_mapping; 2283 struct inode *inode = mapping->host; 2284 ssize_t written; 2285 size_t write_len; 2286 pgoff_t end; 2287 2288 if (count != ocount) 2289 *nr_segs = iov_shorten((struct iovec *)iov, *nr_segs, count); 2290 2291 write_len = iov_length(iov, *nr_segs); 2292 end = (pos + write_len - 1) >> PAGE_CACHE_SHIFT; 2293 2294 written = filemap_write_and_wait_range(mapping, pos, pos + write_len - 1); 2295 if (written) 2296 goto out; 2297 2298 /* 2299 * After a write we want buffered reads to be sure to go to disk to get 2300 * the new data. We invalidate clean cached page from the region we're 2301 * about to write. We do this *before* the write so that we can return 2302 * without clobbering -EIOCBQUEUED from ->direct_IO(). 2303 */ 2304 if (mapping->nrpages) { 2305 written = invalidate_inode_pages2_range(mapping, 2306 pos >> PAGE_CACHE_SHIFT, end); 2307 /* 2308 * If a page can not be invalidated, return 0 to fall back 2309 * to buffered write. 2310 */ 2311 if (written) { 2312 if (written == -EBUSY) 2313 return 0; 2314 goto out; 2315 } 2316 } 2317 2318 written = mapping->a_ops->direct_IO(WRITE, iocb, iov, pos, *nr_segs); 2319 2320 /* 2321 * Finally, try again to invalidate clean pages which might have been 2322 * cached by non-direct readahead, or faulted in by get_user_pages() 2323 * if the source of the write was an mmap'ed region of the file 2324 * we're writing. Either one is a pretty crazy thing to do, 2325 * so we don't support it 100%. If this invalidation 2326 * fails, tough, the write still worked... 2327 */ 2328 if (mapping->nrpages) { 2329 invalidate_inode_pages2_range(mapping, 2330 pos >> PAGE_CACHE_SHIFT, end); 2331 } 2332 2333 if (written > 0) { 2334 pos += written; 2335 if (pos > i_size_read(inode) && !S_ISBLK(inode->i_mode)) { 2336 i_size_write(inode, pos); 2337 mark_inode_dirty(inode); 2338 } 2339 *ppos = pos; 2340 } 2341 out: 2342 return written; 2343 } 2344 EXPORT_SYMBOL(generic_file_direct_write); 2345 2346 /* 2347 * Find or create a page at the given pagecache position. Return the locked 2348 * page. This function is specifically for buffered writes. 2349 */ 2350 struct page *grab_cache_page_write_begin(struct address_space *mapping, 2351 pgoff_t index, unsigned flags) 2352 { 2353 int status; 2354 struct page *page; 2355 gfp_t gfp_notmask = 0; 2356 if (flags & AOP_FLAG_NOFS) 2357 gfp_notmask = __GFP_FS; 2358 repeat: 2359 page = find_lock_page(mapping, index); 2360 if (page) 2361 goto found; 2362 2363 page = __page_cache_alloc(mapping_gfp_mask(mapping) & ~gfp_notmask); 2364 if (!page) 2365 return NULL; 2366 status = add_to_page_cache_lru(page, mapping, index, 2367 GFP_KERNEL & ~gfp_notmask); 2368 if (unlikely(status)) { 2369 page_cache_release(page); 2370 if (status == -EEXIST) 2371 goto repeat; 2372 return NULL; 2373 } 2374 found: 2375 wait_on_page_writeback(page); 2376 return page; 2377 } 2378 EXPORT_SYMBOL(grab_cache_page_write_begin); 2379 2380 static ssize_t generic_perform_write(struct file *file, 2381 struct iov_iter *i, loff_t pos) 2382 { 2383 struct address_space *mapping = file->f_mapping; 2384 const struct address_space_operations *a_ops = mapping->a_ops; 2385 long status = 0; 2386 ssize_t written = 0; 2387 unsigned int flags = 0; 2388 2389 /* 2390 * Copies from kernel address space cannot fail (NFSD is a big user). 2391 */ 2392 if (segment_eq(get_fs(), KERNEL_DS)) 2393 flags |= AOP_FLAG_UNINTERRUPTIBLE; 2394 2395 do { 2396 struct page *page; 2397 unsigned long offset; /* Offset into pagecache page */ 2398 unsigned long bytes; /* Bytes to write to page */ 2399 size_t copied; /* Bytes copied from user */ 2400 void *fsdata; 2401 2402 offset = (pos & (PAGE_CACHE_SIZE - 1)); 2403 bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset, 2404 iov_iter_count(i)); 2405 2406 again: 2407 2408 /* 2409 * Bring in the user page that we will copy from _first_. 2410 * Otherwise there's a nasty deadlock on copying from the 2411 * same page as we're writing to, without it being marked 2412 * up-to-date. 2413 * 2414 * Not only is this an optimisation, but it is also required 2415 * to check that the address is actually valid, when atomic 2416 * usercopies are used, below. 2417 */ 2418 if (unlikely(iov_iter_fault_in_readable(i, bytes))) { 2419 status = -EFAULT; 2420 break; 2421 } 2422 2423 status = a_ops->write_begin(file, mapping, pos, bytes, flags, 2424 &page, &fsdata); 2425 if (unlikely(status)) 2426 break; 2427 2428 if (mapping_writably_mapped(mapping)) 2429 flush_dcache_page(page); 2430 2431 pagefault_disable(); 2432 copied = iov_iter_copy_from_user_atomic(page, i, offset, bytes); 2433 pagefault_enable(); 2434 flush_dcache_page(page); 2435 2436 mark_page_accessed(page); 2437 status = a_ops->write_end(file, mapping, pos, bytes, copied, 2438 page, fsdata); 2439 if (unlikely(status < 0)) 2440 break; 2441 copied = status; 2442 2443 cond_resched(); 2444 2445 iov_iter_advance(i, copied); 2446 if (unlikely(copied == 0)) { 2447 /* 2448 * If we were unable to copy any data at all, we must 2449 * fall back to a single segment length write. 2450 * 2451 * If we didn't fallback here, we could livelock 2452 * because not all segments in the iov can be copied at 2453 * once without a pagefault. 2454 */ 2455 bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset, 2456 iov_iter_single_seg_count(i)); 2457 goto again; 2458 } 2459 pos += copied; 2460 written += copied; 2461 2462 balance_dirty_pages_ratelimited(mapping); 2463 2464 } while (iov_iter_count(i)); 2465 2466 return written ? written : status; 2467 } 2468 2469 ssize_t 2470 generic_file_buffered_write(struct kiocb *iocb, const struct iovec *iov, 2471 unsigned long nr_segs, loff_t pos, loff_t *ppos, 2472 size_t count, ssize_t written) 2473 { 2474 struct file *file = iocb->ki_filp; 2475 ssize_t status; 2476 struct iov_iter i; 2477 2478 iov_iter_init(&i, iov, nr_segs, count, written); 2479 status = generic_perform_write(file, &i, pos); 2480 2481 if (likely(status >= 0)) { 2482 written += status; 2483 *ppos = pos + status; 2484 } 2485 2486 return written ? written : status; 2487 } 2488 EXPORT_SYMBOL(generic_file_buffered_write); 2489 2490 /** 2491 * __generic_file_aio_write - write data to a file 2492 * @iocb: IO state structure (file, offset, etc.) 2493 * @iov: vector with data to write 2494 * @nr_segs: number of segments in the vector 2495 * @ppos: position where to write 2496 * 2497 * This function does all the work needed for actually writing data to a 2498 * file. It does all basic checks, removes SUID from the file, updates 2499 * modification times and calls proper subroutines depending on whether we 2500 * do direct IO or a standard buffered write. 2501 * 2502 * It expects i_mutex to be grabbed unless we work on a block device or similar 2503 * object which does not need locking at all. 2504 * 2505 * This function does *not* take care of syncing data in case of O_SYNC write. 2506 * A caller has to handle it. This is mainly due to the fact that we want to 2507 * avoid syncing under i_mutex. 2508 */ 2509 ssize_t __generic_file_aio_write(struct kiocb *iocb, const struct iovec *iov, 2510 unsigned long nr_segs, loff_t *ppos) 2511 { 2512 struct file *file = iocb->ki_filp; 2513 struct address_space * mapping = file->f_mapping; 2514 size_t ocount; /* original count */ 2515 size_t count; /* after file limit checks */ 2516 struct inode *inode = mapping->host; 2517 loff_t pos; 2518 ssize_t written; 2519 ssize_t err; 2520 2521 ocount = 0; 2522 err = generic_segment_checks(iov, &nr_segs, &ocount, VERIFY_READ); 2523 if (err) 2524 return err; 2525 2526 count = ocount; 2527 pos = *ppos; 2528 2529 vfs_check_frozen(inode->i_sb, SB_FREEZE_WRITE); 2530 2531 /* We can write back this queue in page reclaim */ 2532 current->backing_dev_info = mapping->backing_dev_info; 2533 written = 0; 2534 2535 err = generic_write_checks(file, &pos, &count, S_ISBLK(inode->i_mode)); 2536 if (err) 2537 goto out; 2538 2539 if (count == 0) 2540 goto out; 2541 2542 err = file_remove_suid(file); 2543 if (err) 2544 goto out; 2545 2546 file_update_time(file); 2547 2548 /* coalesce the iovecs and go direct-to-BIO for O_DIRECT */ 2549 if (unlikely(file->f_flags & O_DIRECT)) { 2550 loff_t endbyte; 2551 ssize_t written_buffered; 2552 2553 written = generic_file_direct_write(iocb, iov, &nr_segs, pos, 2554 ppos, count, ocount); 2555 if (written < 0 || written == count) 2556 goto out; 2557 /* 2558 * direct-io write to a hole: fall through to buffered I/O 2559 * for completing the rest of the request. 2560 */ 2561 pos += written; 2562 count -= written; 2563 written_buffered = generic_file_buffered_write(iocb, iov, 2564 nr_segs, pos, ppos, count, 2565 written); 2566 /* 2567 * If generic_file_buffered_write() retuned a synchronous error 2568 * then we want to return the number of bytes which were 2569 * direct-written, or the error code if that was zero. Note 2570 * that this differs from normal direct-io semantics, which 2571 * will return -EFOO even if some bytes were written. 2572 */ 2573 if (written_buffered < 0) { 2574 err = written_buffered; 2575 goto out; 2576 } 2577 2578 /* 2579 * We need to ensure that the page cache pages are written to 2580 * disk and invalidated to preserve the expected O_DIRECT 2581 * semantics. 2582 */ 2583 endbyte = pos + written_buffered - written - 1; 2584 err = filemap_write_and_wait_range(file->f_mapping, pos, endbyte); 2585 if (err == 0) { 2586 written = written_buffered; 2587 invalidate_mapping_pages(mapping, 2588 pos >> PAGE_CACHE_SHIFT, 2589 endbyte >> PAGE_CACHE_SHIFT); 2590 } else { 2591 /* 2592 * We don't know how much we wrote, so just return 2593 * the number of bytes which were direct-written 2594 */ 2595 } 2596 } else { 2597 written = generic_file_buffered_write(iocb, iov, nr_segs, 2598 pos, ppos, count, written); 2599 } 2600 out: 2601 current->backing_dev_info = NULL; 2602 return written ? written : err; 2603 } 2604 EXPORT_SYMBOL(__generic_file_aio_write); 2605 2606 /** 2607 * generic_file_aio_write - write data to a file 2608 * @iocb: IO state structure 2609 * @iov: vector with data to write 2610 * @nr_segs: number of segments in the vector 2611 * @pos: position in file where to write 2612 * 2613 * This is a wrapper around __generic_file_aio_write() to be used by most 2614 * filesystems. It takes care of syncing the file in case of O_SYNC file 2615 * and acquires i_mutex as needed. 2616 */ 2617 ssize_t generic_file_aio_write(struct kiocb *iocb, const struct iovec *iov, 2618 unsigned long nr_segs, loff_t pos) 2619 { 2620 struct file *file = iocb->ki_filp; 2621 struct inode *inode = file->f_mapping->host; 2622 struct blk_plug plug; 2623 ssize_t ret; 2624 2625 BUG_ON(iocb->ki_pos != pos); 2626 2627 mutex_lock(&inode->i_mutex); 2628 blk_start_plug(&plug); 2629 ret = __generic_file_aio_write(iocb, iov, nr_segs, &iocb->ki_pos); 2630 mutex_unlock(&inode->i_mutex); 2631 2632 if (ret > 0 || ret == -EIOCBQUEUED) { 2633 ssize_t err; 2634 2635 err = generic_write_sync(file, pos, ret); 2636 if (err < 0 && ret > 0) 2637 ret = err; 2638 } 2639 blk_finish_plug(&plug); 2640 return ret; 2641 } 2642 EXPORT_SYMBOL(generic_file_aio_write); 2643 2644 /** 2645 * try_to_release_page() - release old fs-specific metadata on a page 2646 * 2647 * @page: the page which the kernel is trying to free 2648 * @gfp_mask: memory allocation flags (and I/O mode) 2649 * 2650 * The address_space is to try to release any data against the page 2651 * (presumably at page->private). If the release was successful, return `1'. 2652 * Otherwise return zero. 2653 * 2654 * This may also be called if PG_fscache is set on a page, indicating that the 2655 * page is known to the local caching routines. 2656 * 2657 * The @gfp_mask argument specifies whether I/O may be performed to release 2658 * this page (__GFP_IO), and whether the call may block (__GFP_WAIT & __GFP_FS). 2659 * 2660 */ 2661 int try_to_release_page(struct page *page, gfp_t gfp_mask) 2662 { 2663 struct address_space * const mapping = page->mapping; 2664 2665 BUG_ON(!PageLocked(page)); 2666 if (PageWriteback(page)) 2667 return 0; 2668 2669 if (mapping && mapping->a_ops->releasepage) 2670 return mapping->a_ops->releasepage(page, gfp_mask); 2671 return try_to_free_buffers(page); 2672 } 2673 2674 EXPORT_SYMBOL(try_to_release_page); 2675