1 /* 2 * fs/mpage.c 3 * 4 * Copyright (C) 2002, Linus Torvalds. 5 * 6 * Contains functions related to preparing and submitting BIOs which contain 7 * multiple pagecache pages. 8 * 9 * 15May2002 akpm@zip.com.au 10 * Initial version 11 * 27Jun2002 axboe@suse.de 12 * use bio_add_page() to build bio's just the right size 13 */ 14 15 #include <linux/kernel.h> 16 #include <linux/module.h> 17 #include <linux/mm.h> 18 #include <linux/kdev_t.h> 19 #include <linux/bio.h> 20 #include <linux/fs.h> 21 #include <linux/buffer_head.h> 22 #include <linux/blkdev.h> 23 #include <linux/highmem.h> 24 #include <linux/prefetch.h> 25 #include <linux/mpage.h> 26 #include <linux/writeback.h> 27 #include <linux/backing-dev.h> 28 #include <linux/pagevec.h> 29 30 /* 31 * I/O completion handler for multipage BIOs. 32 * 33 * The mpage code never puts partial pages into a BIO (except for end-of-file). 34 * If a page does not map to a contiguous run of blocks then it simply falls 35 * back to block_read_full_page(). 36 * 37 * Why is this? If a page's completion depends on a number of different BIOs 38 * which can complete in any order (or at the same time) then determining the 39 * status of that page is hard. See end_buffer_async_read() for the details. 40 * There is no point in duplicating all that complexity. 41 */ 42 static int mpage_end_io_read(struct bio *bio, unsigned int bytes_done, int err) 43 { 44 const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags); 45 struct bio_vec *bvec = bio->bi_io_vec + bio->bi_vcnt - 1; 46 47 if (bio->bi_size) 48 return 1; 49 50 do { 51 struct page *page = bvec->bv_page; 52 53 if (--bvec >= bio->bi_io_vec) 54 prefetchw(&bvec->bv_page->flags); 55 56 if (uptodate) { 57 SetPageUptodate(page); 58 } else { 59 ClearPageUptodate(page); 60 SetPageError(page); 61 } 62 unlock_page(page); 63 } while (bvec >= bio->bi_io_vec); 64 bio_put(bio); 65 return 0; 66 } 67 68 static int mpage_end_io_write(struct bio *bio, unsigned int bytes_done, int err) 69 { 70 const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags); 71 struct bio_vec *bvec = bio->bi_io_vec + bio->bi_vcnt - 1; 72 73 if (bio->bi_size) 74 return 1; 75 76 do { 77 struct page *page = bvec->bv_page; 78 79 if (--bvec >= bio->bi_io_vec) 80 prefetchw(&bvec->bv_page->flags); 81 82 if (!uptodate){ 83 SetPageError(page); 84 if (page->mapping) 85 set_bit(AS_EIO, &page->mapping->flags); 86 } 87 end_page_writeback(page); 88 } while (bvec >= bio->bi_io_vec); 89 bio_put(bio); 90 return 0; 91 } 92 93 static struct bio *mpage_bio_submit(int rw, struct bio *bio) 94 { 95 bio->bi_end_io = mpage_end_io_read; 96 if (rw == WRITE) 97 bio->bi_end_io = mpage_end_io_write; 98 submit_bio(rw, bio); 99 return NULL; 100 } 101 102 static struct bio * 103 mpage_alloc(struct block_device *bdev, 104 sector_t first_sector, int nr_vecs, 105 gfp_t gfp_flags) 106 { 107 struct bio *bio; 108 109 bio = bio_alloc(gfp_flags, nr_vecs); 110 111 if (bio == NULL && (current->flags & PF_MEMALLOC)) { 112 while (!bio && (nr_vecs /= 2)) 113 bio = bio_alloc(gfp_flags, nr_vecs); 114 } 115 116 if (bio) { 117 bio->bi_bdev = bdev; 118 bio->bi_sector = first_sector; 119 } 120 return bio; 121 } 122 123 /* 124 * support function for mpage_readpages. The fs supplied get_block might 125 * return an up to date buffer. This is used to map that buffer into 126 * the page, which allows readpage to avoid triggering a duplicate call 127 * to get_block. 128 * 129 * The idea is to avoid adding buffers to pages that don't already have 130 * them. So when the buffer is up to date and the page size == block size, 131 * this marks the page up to date instead of adding new buffers. 132 */ 133 static void 134 map_buffer_to_page(struct page *page, struct buffer_head *bh, int page_block) 135 { 136 struct inode *inode = page->mapping->host; 137 struct buffer_head *page_bh, *head; 138 int block = 0; 139 140 if (!page_has_buffers(page)) { 141 /* 142 * don't make any buffers if there is only one buffer on 143 * the page and the page just needs to be set up to date 144 */ 145 if (inode->i_blkbits == PAGE_CACHE_SHIFT && 146 buffer_uptodate(bh)) { 147 SetPageUptodate(page); 148 return; 149 } 150 create_empty_buffers(page, 1 << inode->i_blkbits, 0); 151 } 152 head = page_buffers(page); 153 page_bh = head; 154 do { 155 if (block == page_block) { 156 page_bh->b_state = bh->b_state; 157 page_bh->b_bdev = bh->b_bdev; 158 page_bh->b_blocknr = bh->b_blocknr; 159 break; 160 } 161 page_bh = page_bh->b_this_page; 162 block++; 163 } while (page_bh != head); 164 } 165 166 /* 167 * This is the worker routine which does all the work of mapping the disk 168 * blocks and constructs largest possible bios, submits them for IO if the 169 * blocks are not contiguous on the disk. 170 * 171 * We pass a buffer_head back and forth and use its buffer_mapped() flag to 172 * represent the validity of its disk mapping and to decide when to do the next 173 * get_block() call. 174 */ 175 static struct bio * 176 do_mpage_readpage(struct bio *bio, struct page *page, unsigned nr_pages, 177 sector_t *last_block_in_bio, struct buffer_head *map_bh, 178 unsigned long *first_logical_block, get_block_t get_block) 179 { 180 struct inode *inode = page->mapping->host; 181 const unsigned blkbits = inode->i_blkbits; 182 const unsigned blocks_per_page = PAGE_CACHE_SIZE >> blkbits; 183 const unsigned blocksize = 1 << blkbits; 184 sector_t block_in_file; 185 sector_t last_block; 186 sector_t last_block_in_file; 187 sector_t blocks[MAX_BUF_PER_PAGE]; 188 unsigned page_block; 189 unsigned first_hole = blocks_per_page; 190 struct block_device *bdev = NULL; 191 int length; 192 int fully_mapped = 1; 193 unsigned nblocks; 194 unsigned relative_block; 195 196 if (page_has_buffers(page)) 197 goto confused; 198 199 block_in_file = (sector_t)page->index << (PAGE_CACHE_SHIFT - blkbits); 200 last_block = block_in_file + nr_pages * blocks_per_page; 201 last_block_in_file = (i_size_read(inode) + blocksize - 1) >> blkbits; 202 if (last_block > last_block_in_file) 203 last_block = last_block_in_file; 204 page_block = 0; 205 206 /* 207 * Map blocks using the result from the previous get_blocks call first. 208 */ 209 nblocks = map_bh->b_size >> blkbits; 210 if (buffer_mapped(map_bh) && block_in_file > *first_logical_block && 211 block_in_file < (*first_logical_block + nblocks)) { 212 unsigned map_offset = block_in_file - *first_logical_block; 213 unsigned last = nblocks - map_offset; 214 215 for (relative_block = 0; ; relative_block++) { 216 if (relative_block == last) { 217 clear_buffer_mapped(map_bh); 218 break; 219 } 220 if (page_block == blocks_per_page) 221 break; 222 blocks[page_block] = map_bh->b_blocknr + map_offset + 223 relative_block; 224 page_block++; 225 block_in_file++; 226 } 227 bdev = map_bh->b_bdev; 228 } 229 230 /* 231 * Then do more get_blocks calls until we are done with this page. 232 */ 233 map_bh->b_page = page; 234 while (page_block < blocks_per_page) { 235 map_bh->b_state = 0; 236 map_bh->b_size = 0; 237 238 if (block_in_file < last_block) { 239 map_bh->b_size = (last_block-block_in_file) << blkbits; 240 if (get_block(inode, block_in_file, map_bh, 0)) 241 goto confused; 242 *first_logical_block = block_in_file; 243 } 244 245 if (!buffer_mapped(map_bh)) { 246 fully_mapped = 0; 247 if (first_hole == blocks_per_page) 248 first_hole = page_block; 249 page_block++; 250 block_in_file++; 251 clear_buffer_mapped(map_bh); 252 continue; 253 } 254 255 /* some filesystems will copy data into the page during 256 * the get_block call, in which case we don't want to 257 * read it again. map_buffer_to_page copies the data 258 * we just collected from get_block into the page's buffers 259 * so readpage doesn't have to repeat the get_block call 260 */ 261 if (buffer_uptodate(map_bh)) { 262 map_buffer_to_page(page, map_bh, page_block); 263 goto confused; 264 } 265 266 if (first_hole != blocks_per_page) 267 goto confused; /* hole -> non-hole */ 268 269 /* Contiguous blocks? */ 270 if (page_block && blocks[page_block-1] != map_bh->b_blocknr-1) 271 goto confused; 272 nblocks = map_bh->b_size >> blkbits; 273 for (relative_block = 0; ; relative_block++) { 274 if (relative_block == nblocks) { 275 clear_buffer_mapped(map_bh); 276 break; 277 } else if (page_block == blocks_per_page) 278 break; 279 blocks[page_block] = map_bh->b_blocknr+relative_block; 280 page_block++; 281 block_in_file++; 282 } 283 bdev = map_bh->b_bdev; 284 } 285 286 if (first_hole != blocks_per_page) { 287 zero_user_page(page, first_hole << blkbits, 288 PAGE_CACHE_SIZE - (first_hole << blkbits), 289 KM_USER0); 290 if (first_hole == 0) { 291 SetPageUptodate(page); 292 unlock_page(page); 293 goto out; 294 } 295 } else if (fully_mapped) { 296 SetPageMappedToDisk(page); 297 } 298 299 /* 300 * This page will go to BIO. Do we need to send this BIO off first? 301 */ 302 if (bio && (*last_block_in_bio != blocks[0] - 1)) 303 bio = mpage_bio_submit(READ, bio); 304 305 alloc_new: 306 if (bio == NULL) { 307 bio = mpage_alloc(bdev, blocks[0] << (blkbits - 9), 308 min_t(int, nr_pages, bio_get_nr_vecs(bdev)), 309 GFP_KERNEL); 310 if (bio == NULL) 311 goto confused; 312 } 313 314 length = first_hole << blkbits; 315 if (bio_add_page(bio, page, length, 0) < length) { 316 bio = mpage_bio_submit(READ, bio); 317 goto alloc_new; 318 } 319 320 if (buffer_boundary(map_bh) || (first_hole != blocks_per_page)) 321 bio = mpage_bio_submit(READ, bio); 322 else 323 *last_block_in_bio = blocks[blocks_per_page - 1]; 324 out: 325 return bio; 326 327 confused: 328 if (bio) 329 bio = mpage_bio_submit(READ, bio); 330 if (!PageUptodate(page)) 331 block_read_full_page(page, get_block); 332 else 333 unlock_page(page); 334 goto out; 335 } 336 337 /** 338 * mpage_readpages - populate an address space with some pages, and 339 * start reads against them. 340 * 341 * @mapping: the address_space 342 * @pages: The address of a list_head which contains the target pages. These 343 * pages have their ->index populated and are otherwise uninitialised. 344 * 345 * The page at @pages->prev has the lowest file offset, and reads should be 346 * issued in @pages->prev to @pages->next order. 347 * 348 * @nr_pages: The number of pages at *@pages 349 * @get_block: The filesystem's block mapper function. 350 * 351 * This function walks the pages and the blocks within each page, building and 352 * emitting large BIOs. 353 * 354 * If anything unusual happens, such as: 355 * 356 * - encountering a page which has buffers 357 * - encountering a page which has a non-hole after a hole 358 * - encountering a page with non-contiguous blocks 359 * 360 * then this code just gives up and calls the buffer_head-based read function. 361 * It does handle a page which has holes at the end - that is a common case: 362 * the end-of-file on blocksize < PAGE_CACHE_SIZE setups. 363 * 364 * BH_Boundary explanation: 365 * 366 * There is a problem. The mpage read code assembles several pages, gets all 367 * their disk mappings, and then submits them all. That's fine, but obtaining 368 * the disk mappings may require I/O. Reads of indirect blocks, for example. 369 * 370 * So an mpage read of the first 16 blocks of an ext2 file will cause I/O to be 371 * submitted in the following order: 372 * 12 0 1 2 3 4 5 6 7 8 9 10 11 13 14 15 16 373 * because the indirect block has to be read to get the mappings of blocks 374 * 13,14,15,16. Obviously, this impacts performance. 375 * 376 * So what we do it to allow the filesystem's get_block() function to set 377 * BH_Boundary when it maps block 11. BH_Boundary says: mapping of the block 378 * after this one will require I/O against a block which is probably close to 379 * this one. So you should push what I/O you have currently accumulated. 380 * 381 * This all causes the disk requests to be issued in the correct order. 382 */ 383 int 384 mpage_readpages(struct address_space *mapping, struct list_head *pages, 385 unsigned nr_pages, get_block_t get_block) 386 { 387 struct bio *bio = NULL; 388 unsigned page_idx; 389 sector_t last_block_in_bio = 0; 390 struct pagevec lru_pvec; 391 struct buffer_head map_bh; 392 unsigned long first_logical_block = 0; 393 394 clear_buffer_mapped(&map_bh); 395 pagevec_init(&lru_pvec, 0); 396 for (page_idx = 0; page_idx < nr_pages; page_idx++) { 397 struct page *page = list_entry(pages->prev, struct page, lru); 398 399 prefetchw(&page->flags); 400 list_del(&page->lru); 401 if (!add_to_page_cache(page, mapping, 402 page->index, GFP_KERNEL)) { 403 bio = do_mpage_readpage(bio, page, 404 nr_pages - page_idx, 405 &last_block_in_bio, &map_bh, 406 &first_logical_block, 407 get_block); 408 if (!pagevec_add(&lru_pvec, page)) 409 __pagevec_lru_add(&lru_pvec); 410 } else { 411 page_cache_release(page); 412 } 413 } 414 pagevec_lru_add(&lru_pvec); 415 BUG_ON(!list_empty(pages)); 416 if (bio) 417 mpage_bio_submit(READ, bio); 418 return 0; 419 } 420 EXPORT_SYMBOL(mpage_readpages); 421 422 /* 423 * This isn't called much at all 424 */ 425 int mpage_readpage(struct page *page, get_block_t get_block) 426 { 427 struct bio *bio = NULL; 428 sector_t last_block_in_bio = 0; 429 struct buffer_head map_bh; 430 unsigned long first_logical_block = 0; 431 432 clear_buffer_mapped(&map_bh); 433 bio = do_mpage_readpage(bio, page, 1, &last_block_in_bio, 434 &map_bh, &first_logical_block, get_block); 435 if (bio) 436 mpage_bio_submit(READ, bio); 437 return 0; 438 } 439 EXPORT_SYMBOL(mpage_readpage); 440 441 /* 442 * Writing is not so simple. 443 * 444 * If the page has buffers then they will be used for obtaining the disk 445 * mapping. We only support pages which are fully mapped-and-dirty, with a 446 * special case for pages which are unmapped at the end: end-of-file. 447 * 448 * If the page has no buffers (preferred) then the page is mapped here. 449 * 450 * If all blocks are found to be contiguous then the page can go into the 451 * BIO. Otherwise fall back to the mapping's writepage(). 452 * 453 * FIXME: This code wants an estimate of how many pages are still to be 454 * written, so it can intelligently allocate a suitably-sized BIO. For now, 455 * just allocate full-size (16-page) BIOs. 456 */ 457 struct mpage_data { 458 struct bio *bio; 459 sector_t last_block_in_bio; 460 get_block_t *get_block; 461 unsigned use_writepage; 462 }; 463 464 static int __mpage_writepage(struct page *page, struct writeback_control *wbc, 465 void *data) 466 { 467 struct mpage_data *mpd = data; 468 struct bio *bio = mpd->bio; 469 struct address_space *mapping = page->mapping; 470 struct inode *inode = page->mapping->host; 471 const unsigned blkbits = inode->i_blkbits; 472 unsigned long end_index; 473 const unsigned blocks_per_page = PAGE_CACHE_SIZE >> blkbits; 474 sector_t last_block; 475 sector_t block_in_file; 476 sector_t blocks[MAX_BUF_PER_PAGE]; 477 unsigned page_block; 478 unsigned first_unmapped = blocks_per_page; 479 struct block_device *bdev = NULL; 480 int boundary = 0; 481 sector_t boundary_block = 0; 482 struct block_device *boundary_bdev = NULL; 483 int length; 484 struct buffer_head map_bh; 485 loff_t i_size = i_size_read(inode); 486 int ret = 0; 487 488 if (page_has_buffers(page)) { 489 struct buffer_head *head = page_buffers(page); 490 struct buffer_head *bh = head; 491 492 /* If they're all mapped and dirty, do it */ 493 page_block = 0; 494 do { 495 BUG_ON(buffer_locked(bh)); 496 if (!buffer_mapped(bh)) { 497 /* 498 * unmapped dirty buffers are created by 499 * __set_page_dirty_buffers -> mmapped data 500 */ 501 if (buffer_dirty(bh)) 502 goto confused; 503 if (first_unmapped == blocks_per_page) 504 first_unmapped = page_block; 505 continue; 506 } 507 508 if (first_unmapped != blocks_per_page) 509 goto confused; /* hole -> non-hole */ 510 511 if (!buffer_dirty(bh) || !buffer_uptodate(bh)) 512 goto confused; 513 if (page_block) { 514 if (bh->b_blocknr != blocks[page_block-1] + 1) 515 goto confused; 516 } 517 blocks[page_block++] = bh->b_blocknr; 518 boundary = buffer_boundary(bh); 519 if (boundary) { 520 boundary_block = bh->b_blocknr; 521 boundary_bdev = bh->b_bdev; 522 } 523 bdev = bh->b_bdev; 524 } while ((bh = bh->b_this_page) != head); 525 526 if (first_unmapped) 527 goto page_is_mapped; 528 529 /* 530 * Page has buffers, but they are all unmapped. The page was 531 * created by pagein or read over a hole which was handled by 532 * block_read_full_page(). If this address_space is also 533 * using mpage_readpages then this can rarely happen. 534 */ 535 goto confused; 536 } 537 538 /* 539 * The page has no buffers: map it to disk 540 */ 541 BUG_ON(!PageUptodate(page)); 542 block_in_file = (sector_t)page->index << (PAGE_CACHE_SHIFT - blkbits); 543 last_block = (i_size - 1) >> blkbits; 544 map_bh.b_page = page; 545 for (page_block = 0; page_block < blocks_per_page; ) { 546 547 map_bh.b_state = 0; 548 map_bh.b_size = 1 << blkbits; 549 if (mpd->get_block(inode, block_in_file, &map_bh, 1)) 550 goto confused; 551 if (buffer_new(&map_bh)) 552 unmap_underlying_metadata(map_bh.b_bdev, 553 map_bh.b_blocknr); 554 if (buffer_boundary(&map_bh)) { 555 boundary_block = map_bh.b_blocknr; 556 boundary_bdev = map_bh.b_bdev; 557 } 558 if (page_block) { 559 if (map_bh.b_blocknr != blocks[page_block-1] + 1) 560 goto confused; 561 } 562 blocks[page_block++] = map_bh.b_blocknr; 563 boundary = buffer_boundary(&map_bh); 564 bdev = map_bh.b_bdev; 565 if (block_in_file == last_block) 566 break; 567 block_in_file++; 568 } 569 BUG_ON(page_block == 0); 570 571 first_unmapped = page_block; 572 573 page_is_mapped: 574 end_index = i_size >> PAGE_CACHE_SHIFT; 575 if (page->index >= end_index) { 576 /* 577 * The page straddles i_size. It must be zeroed out on each 578 * and every writepage invokation because it may be mmapped. 579 * "A file is mapped in multiples of the page size. For a file 580 * that is not a multiple of the page size, the remaining memory 581 * is zeroed when mapped, and writes to that region are not 582 * written out to the file." 583 */ 584 unsigned offset = i_size & (PAGE_CACHE_SIZE - 1); 585 586 if (page->index > end_index || !offset) 587 goto confused; 588 zero_user_page(page, offset, PAGE_CACHE_SIZE - offset, 589 KM_USER0); 590 } 591 592 /* 593 * This page will go to BIO. Do we need to send this BIO off first? 594 */ 595 if (bio && mpd->last_block_in_bio != blocks[0] - 1) 596 bio = mpage_bio_submit(WRITE, bio); 597 598 alloc_new: 599 if (bio == NULL) { 600 bio = mpage_alloc(bdev, blocks[0] << (blkbits - 9), 601 bio_get_nr_vecs(bdev), GFP_NOFS|__GFP_HIGH); 602 if (bio == NULL) 603 goto confused; 604 } 605 606 /* 607 * Must try to add the page before marking the buffer clean or 608 * the confused fail path above (OOM) will be very confused when 609 * it finds all bh marked clean (i.e. it will not write anything) 610 */ 611 length = first_unmapped << blkbits; 612 if (bio_add_page(bio, page, length, 0) < length) { 613 bio = mpage_bio_submit(WRITE, bio); 614 goto alloc_new; 615 } 616 617 /* 618 * OK, we have our BIO, so we can now mark the buffers clean. Make 619 * sure to only clean buffers which we know we'll be writing. 620 */ 621 if (page_has_buffers(page)) { 622 struct buffer_head *head = page_buffers(page); 623 struct buffer_head *bh = head; 624 unsigned buffer_counter = 0; 625 626 do { 627 if (buffer_counter++ == first_unmapped) 628 break; 629 clear_buffer_dirty(bh); 630 bh = bh->b_this_page; 631 } while (bh != head); 632 633 /* 634 * we cannot drop the bh if the page is not uptodate 635 * or a concurrent readpage would fail to serialize with the bh 636 * and it would read from disk before we reach the platter. 637 */ 638 if (buffer_heads_over_limit && PageUptodate(page)) 639 try_to_free_buffers(page); 640 } 641 642 BUG_ON(PageWriteback(page)); 643 set_page_writeback(page); 644 unlock_page(page); 645 if (boundary || (first_unmapped != blocks_per_page)) { 646 bio = mpage_bio_submit(WRITE, bio); 647 if (boundary_block) { 648 write_boundary_block(boundary_bdev, 649 boundary_block, 1 << blkbits); 650 } 651 } else { 652 mpd->last_block_in_bio = blocks[blocks_per_page - 1]; 653 } 654 goto out; 655 656 confused: 657 if (bio) 658 bio = mpage_bio_submit(WRITE, bio); 659 660 if (mpd->use_writepage) { 661 ret = mapping->a_ops->writepage(page, wbc); 662 } else { 663 ret = -EAGAIN; 664 goto out; 665 } 666 /* 667 * The caller has a ref on the inode, so *mapping is stable 668 */ 669 mapping_set_error(mapping, ret); 670 out: 671 mpd->bio = bio; 672 return ret; 673 } 674 675 /** 676 * mpage_writepages - walk the list of dirty pages of the given 677 * address space and writepage() all of them. 678 * 679 * @mapping: address space structure to write 680 * @wbc: subtract the number of written pages from *@wbc->nr_to_write 681 * @get_block: the filesystem's block mapper function. 682 * If this is NULL then use a_ops->writepage. Otherwise, go 683 * direct-to-BIO. 684 * 685 * This is a library function, which implements the writepages() 686 * address_space_operation. 687 * 688 * If a page is already under I/O, generic_writepages() skips it, even 689 * if it's dirty. This is desirable behaviour for memory-cleaning writeback, 690 * but it is INCORRECT for data-integrity system calls such as fsync(). fsync() 691 * and msync() need to guarantee that all the data which was dirty at the time 692 * the call was made get new I/O started against them. If wbc->sync_mode is 693 * WB_SYNC_ALL then we were called for data integrity and we must wait for 694 * existing IO to complete. 695 */ 696 int 697 mpage_writepages(struct address_space *mapping, 698 struct writeback_control *wbc, get_block_t get_block) 699 { 700 int ret; 701 702 if (!get_block) 703 ret = generic_writepages(mapping, wbc); 704 else { 705 struct mpage_data mpd = { 706 .bio = NULL, 707 .last_block_in_bio = 0, 708 .get_block = get_block, 709 .use_writepage = 1, 710 }; 711 712 ret = write_cache_pages(mapping, wbc, __mpage_writepage, &mpd); 713 if (mpd.bio) 714 mpage_bio_submit(WRITE, mpd.bio); 715 } 716 return ret; 717 } 718 EXPORT_SYMBOL(mpage_writepages); 719 720 int mpage_writepage(struct page *page, get_block_t get_block, 721 struct writeback_control *wbc) 722 { 723 struct mpage_data mpd = { 724 .bio = NULL, 725 .last_block_in_bio = 0, 726 .get_block = get_block, 727 .use_writepage = 0, 728 }; 729 int ret = __mpage_writepage(page, wbc, &mpd); 730 if (mpd.bio) 731 mpage_bio_submit(WRITE, mpd.bio); 732 return ret; 733 } 734 EXPORT_SYMBOL(mpage_writepage); 735