/* * fs/mpage.c * * Copyright (C) 2002, Linus Torvalds. * * Contains functions related to preparing and submitting BIOs which contain * multiple pagecache pages. * * 15May2002 akpm@zip.com.au * Initial version * 27Jun2002 axboe@suse.de * use bio_add_page() to build bio's just the right size */ #include <linux/kernel.h>#include <linux/module.h>#include <linux/mm.h>#include <linux/kdev_t.h>#include <linux/bio.h>#include <linux/fs.h>#include <linux/buffer_head.h>#include <linux/blkdev.h>#include <linux/highmem.h>#include <linux/prefetch.h>#include <linux/mpage.h>#include <linux/writeback.h>#include <linux/backing-dev.h>#include <linux/pagevec.h> /* * I/O completion handler for multipage BIOs. * * The mpage code never puts partial pages into a BIO (except for end-of-file). * If a page does not map to a contiguous run of blocks then it simply falls * back to block_read_full_page(). * * Why is this? If a page's completion depends on a number of different BIOs * which can complete in any order (or at the same time) then determining the * status of that page is hard. See end_buffer_async_read() for the details. * There is no point in duplicating all that complexity. */static int mpage_end_io_read(struct bio *bio, unsigned int bytes_done, int err){ const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags); struct bio_vec *bvec = bio->bi_io_vec + bio->bi_vcnt - 1; if (bio->bi_size) return 1; do { struct page *page = bvec->bv_page; if (--bvec >= bio->bi_io_vec) prefetchw(&bvec->bv_page->flags); if (uptodate) { SetPageUptodate(page); } else { ClearPageUptodate(page); SetPageError(page); } unlock_page(page); } while (bvec >= bio->bi_io_vec); bio_put(bio); return 0;} static int mpage_end_io_write(struct bio *bio, unsigned int bytes_done, int err){ const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags); struct bio_vec *bvec = bio->bi_io_vec + bio->bi_vcnt - 1; if (bio->bi_size) return 1; do { struct page *page = bvec->bv_page; if (--bvec >= bio->bi_io_vec) prefetchw(&bvec->bv_page->flags); if (!uptodate){ SetPageError(page); if (page->mapping) set_bit(AS_EIO, &page->mapping->flags); } end_page_writeback(page); } while (bvec >= bio->bi_io_vec); bio_put(bio); return 0;} static struct bio *mpage_bio_submit(int rw, struct bio *bio){ bio->bi_end_io = mpage_end_io_read; if (rw == WRITE) bio->bi_end_io = mpage_end_io_write; submit_bio(rw, bio); return NULL;} static struct bio *mpage_alloc(struct block_device *bdev, sector_t first_sector, int nr_vecs, unsigned int __nocast gfp_flags){ struct bio *bio; bio = bio_alloc(gfp_flags, nr_vecs); if (bio == NULL && (current->flags & PF_MEMALLOC)) { while (!bio && (nr_vecs /= 2)) bio = bio_alloc(gfp_flags, nr_vecs); } if (bio) { bio->bi_bdev = bdev; bio->bi_sector = first_sector; } return bio;} /* * support function for mpage_readpages. The fs supplied get_block might * return an up to date buffer. This is used to map that buffer into * the page, which allows readpage to avoid triggering a duplicate call * to get_block. * * The idea is to avoid adding buffers to pages that don't already have * them. So when the buffer is up to date and the page size == block size, * this marks the page up to date instead of adding new buffers. */static void map_buffer_to_page(struct page *page, struct buffer_head *bh, int page_block) { struct inode *inode = page->mapping->host; struct buffer_head *page_bh, *head; int block = 0; if (!page_has_buffers(page)) { /* * don't make any buffers if there is only one buffer on * the page and the page just needs to be set up to date */ if (inode->i_blkbits == PAGE_CACHE_SHIFT && buffer_uptodate(bh)) { SetPageUptodate(page); return; } create_empty_buffers(page, 1 << inode->i_blkbits, 0); } head = page_buffers(page); page_bh = head; do { if (block == page_block) { page_bh->b_state = bh->b_state; page_bh->b_bdev = bh->b_bdev; page_bh->b_blocknr = bh->b_blocknr; break; } page_bh = page_bh->b_this_page; block++; } while (page_bh != head);} static struct bio *do_mpage_readpage(struct bio *bio, struct page *page, unsigned nr_pages, sector_t *last_block_in_bio, get_block_t get_block){ struct inode *inode = page->mapping->host; const unsigned blkbits = inode->i_blkbits; const unsigned blocks_per_page = PAGE_CACHE_SIZE >> blkbits; const unsigned blocksize = 1 << blkbits; sector_t block_in_file; sector_t last_block; sector_t blocks[MAX_BUF_PER_PAGE]; unsigned page_block; unsigned first_hole = blocks_per_page; struct block_device *bdev = NULL; struct buffer_head bh; int length; int fully_mapped = 1; if (page_has_buffers(page)) goto confused; block_in_file = page->index << (PAGE_CACHE_SHIFT - blkbits); last_block = (i_size_read(inode) + blocksize - 1) >> blkbits; bh.b_page = page; for (page_block = 0; page_block < blocks_per_page; page_block++, block_in_file++) { bh.b_state = 0; if (block_in_file < last_block) { if (get_block(inode, block_in_file, &bh, 0)) goto confused; } if (!buffer_mapped(&bh)) { fully_mapped = 0; if (first_hole == blocks_per_page) first_hole = page_block; continue; } /* some filesystems will copy data into the page during * the get_block call, in which case we don't want to * read it again. map_buffer_to_page copies the data * we just collected from get_block into the page's buffers * so readpage doesn't have to repeat the get_block call */ if (buffer_uptodate(&bh)) { map_buffer_to_page(page, &bh, page_block); goto confused; } if (first_hole != blocks_per_page) goto confused; /* hole -> non-hole */ /* Contiguous blocks? */ if (page_block && blocks[page_block-1] != bh.b_blocknr-1) goto confused; blocks[page_block] = bh.b_blocknr; bdev = bh.b_bdev; } if (first_hole != blocks_per_page) { char *kaddr = kmap_atomic(page, KM_USER0); memset(kaddr + (first_hole << blkbits), 0, PAGE_CACHE_SIZE - (first_hole << blkbits)); flush_dcache_page(page); kunmap_atomic(kaddr, KM_USER0); if (first_hole == 0) { SetPageUptodate(page); unlock_page(page); goto out; } } else if (fully_mapped) { SetPageMappedToDisk(page); } /* * This page will go to BIO. Do we need to send this BIO off first? */ if (bio && (*last_block_in_bio != blocks[0] - 1)) bio = mpage_bio_submit(READ, bio); alloc_new: if (bio == NULL) { bio = mpage_alloc(bdev, blocks[0] << (blkbits - 9), min_t(int, nr_pages, bio_get_nr_vecs(bdev)), GFP_KERNEL); if (bio == NULL) goto confused; } length = first_hole << blkbits; if (bio_add_page(bio, page, length, 0) < length) { bio = mpage_bio_submit(READ, bio); goto alloc_new; } if (buffer_boundary(&bh) || (first_hole != blocks_per_page)) bio = mpage_bio_submit(READ, bio); else *last_block_in_bio = blocks[blocks_per_page - 1];out: return bio; confused: if (bio) bio = mpage_bio_submit(READ, bio); if (!PageUptodate(page)) block_read_full_page(page, get_block); else unlock_page(page); goto out;} /** * mpage_readpages - populate an address space with some pages, and * start reads against them. * * @mapping: the address_space * @pages: The address of a list_head which contains the target pages. These * pages have their ->index populated and are otherwise uninitialised. * * The page at @pages->prev has the lowest file offset, and reads should be * issued in @pages->prev to @pages->next order. * * @nr_pages: The number of pages at *@pages * @get_block: The filesystem's block mapper function. * * This function walks the pages and the blocks within each page, building and * emitting large BIOs. * * If anything unusual happens, such as: * * - encountering a page which has buffers * - encountering a page which has a non-hole after a hole * - encountering a page with non-contiguous blocks * * then this code just gives up and calls the buffer_head-based read function. * It does handle a page which has holes at the end - that is a common case: * the end-of-file on blocksize < PAGE_CACHE_SIZE setups. * * BH_Boundary explanation: * * There is a problem. The mpage read code assembles several pages, gets all * their disk mappings, and then submits them all. That's fine, but obtaining * the disk mappings may require I/O. Reads of indirect blocks, for example. * * So an mpage read of the first 16 blocks of an ext2 file will cause I/O to be * submitted in the following order: * 12 0 1 2 3 4 5 6 7 8 9 10 11 13 14 15 16 * because the indirect block has to be read to get the mappings of blocks * 13,14,15,16. Obviously, this impacts performance. * * So what we do it to allow the filesystem's get_block() function to set * BH_Boundary when it maps block 11. BH_Boundary says: mapping of the block * after this one will require I/O against a block which is probably close to * this one. So you should push what I/O you have currently accumulated. * * This all causes the disk requests to be issued in the correct order. */intmpage_readpages(struct address_space *mapping, struct list_head *pages, unsigned nr_pages, get_block_t get_block){ struct bio *bio = NULL; unsigned page_idx; sector_t last_block_in_bio = 0; struct pagevec lru_pvec; pagevec_init(&lru_pvec, 0); for (page_idx = 0; page_idx < nr_pages; page_idx++) { struct page *page = list_entry(pages->prev, struct page, lru); prefetchw(&page->flags); list_del(&page->lru); if (!add_to_page_cache(page, mapping, page->index, GFP_KERNEL)) { bio = do_mpage_readpage(bio, page, nr_pages - page_idx, &last_block_in_bio, get_block); if (!pagevec_add(&lru_pvec, page)) __pagevec_lru_add(&lru_pvec); } else { page_cache_release(page); } } pagevec_lru_add(&lru_pvec); BUG_ON(!list_empty(pages)); if (bio) mpage_bio_submit(READ, bio); return 0;}EXPORT_SYMBOL(mpage_readpages); /* * This isn't called much at all */int mpage_readpage(struct page *page, get_block_t get_block){ struct bio *bio = NULL; sector_t last_block_in_bio = 0; bio = do_mpage_readpage(bio, page, 1, &last_block_in_bio, get_block); if (bio) mpage_bio_submit(READ, bio); return 0;}EXPORT_SYMBOL(mpage_readpage); /* * Writing is not so simple. * * If the page has buffers then they will be used for obtaining the disk * mapping. We only support pages which are fully mapped-and-dirty, with a * special case for pages which are unmapped at the end: end-of-file. * * If the page has no buffers (preferred) then the page is mapped here. * * If all blocks are found to be contiguous then the page can go into the * BIO. Otherwise fall back to the mapping's writepage(). * * FIXME: This code wants an estimate of how many pages are still to be * written, so it can intelligently allocate a suitably-sized BIO. For now, * just allocate full-size (16-page) BIOs. */static struct bio *__mpage_writepage(struct bio *bio, struct page *page, get_block_t get_block, sector_t *last_block_in_bio, int *ret, struct writeback_control *wbc, writepage_t writepage_fn){ struct address_space *mapping = page->mapping; struct inode *inode = page->mapping->host; const unsigned blkbits = inode->i_blkbits; unsigned long end_index; const unsigned blocks_per_page = PAGE_CACHE_SIZE >> blkbits; sector_t last_block; sector_t block_in_file; sector_t blocks[MAX_BUF_PER_PAGE]; unsigned page_block; unsigned first_unmapped = blocks_per_page; struct block_device *bdev = NULL; int boundary = 0; sector_t boundary_block = 0; struct block_device *boundary_bdev = NULL; int length; struct buffer_head map_bh; loff_t i_size = i_size_read(inode); if (page_has_buffers(page)) { struct buffer_head *head = page_buffers(page); struct buffer_head *bh = head; /* If they're all mapped and dirty, do it */ page_block = 0; do { BUG_ON(buffer_locked(bh)); if (!buffer_mapped(bh)) { /* * unmapped dirty buffers are created by * __set_page_dirty_buffers -> mmapped data */ if (buffer_dirty(bh)) goto confused; if (first_unmapped == blocks_per_page) first_unmapped = page_block; continue; } if (first_unmapped != blocks_per_page) goto confused; /* hole -> non-hole */ if (!buffer_dirty(bh) || !buffer_uptodate(bh)) goto confused; if (page_block) { if (bh->b_blocknr != blocks[page_block-1] + 1) goto confused; } blocks[page_block++] = bh->b_blocknr; boundary = buffer_boundary(bh); if (boundary) { boundary_block = bh->b_blocknr; boundary_bdev = bh->b_bdev; } bdev = bh->b_bdev; } while ((bh = bh->b_this_page) != head); if (first_unmapped) goto page_is_mapped; /* * Page has buffers, but they are all unmapped. The page was * created by pagein or read over a hole which was handled by * block_read_full_page(). If this address_space is also * using mpage_readpages then this can rarely happen. */ goto confused; } /* * The page has no buffers: map it to disk */ BUG_ON(!PageUptodate(page)); block_in_file = page->index << (PAGE_CACHE_SHIFT - blkbits); last_block = (i_size - 1) >> blkbits; map_bh.b_page = page; for (page_block = 0; page_block < blocks_per_page; ) { map_bh.b_state = 0; if (get_block(inode, block_in_file, &map_bh, 1)) goto confused; if (buffer_new(&map_bh)) unmap_underlying_metadata(map_bh.b_bdev, map_bh.b_blocknr); if (buffer_boundary(&map_bh)) { boundary_block = map_bh.b_blocknr; boundary_bdev = map_bh.b_bdev; } if (page_block) { if (map_bh.b_blocknr != blocks[page_block-1] + 1) goto confused; } blocks[page_block++] = map_bh.b_blocknr; boundary = buffer_boundary(&map_bh); bdev = map_bh.b_bdev; if (block_in_file == last_block) break; block_in_file++; } BUG_ON(page_block == 0); first_unmapped = page_block; page_is_mapped: end_index = i_size >> PAGE_CACHE_SHIFT;Lines 1–500 of 767. 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/* * fs/mpage.c * * Copyright (C) 2002, Linus Torvalds. * * Contains functions related to preparing and submitting BIOs which contain * multiple pagecache pages. * * 15May2002 akpm@zip.com.au * Initial version * 27Jun2002 axboe@suse.de * use bio_add_page() to build bio's just the right size */ #include <linux/kernel.h> #include <linux/module.h> #include <linux/mm.h> #include <linux/kdev_t.h> #include <linux/bio.h> #include <linux/fs.h> #include <linux/buffer_head.h> #include <linux/blkdev.h> #include <linux/highmem.h> #include <linux/prefetch.h> #include <linux/mpage.h> #include <linux/writeback.h> #include <linux/backing-dev.h> #include <linux/pagevec.h> /* * I/O completion handler for multipage BIOs. * * The mpage code never puts partial pages into a BIO (except for end-of-file). * If a page does not map to a contiguous run of blocks then it simply falls * back to block_read_full_page(). * * Why is this? If a page's completion depends on a number of different BIOs * which can complete in any order (or at the same time) then determining the * status of that page is hard. See end_buffer_async_read() for the details. * There is no point in duplicating all that complexity. */ static int mpage_end_io_read(struct bio *bio, unsigned int bytes_done, int err) { const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags); struct bio_vec *bvec = bio->bi_io_vec + bio->bi_vcnt - 1; if (bio->bi_size) return 1; do { struct page *page = bvec->bv_page; if (--bvec >= bio->bi_io_vec) prefetchw(&bvec->bv_page->flags); if (uptodate) { SetPageUptodate(page); } else { ClearPageUptodate(page); SetPageError(page); } unlock_page(page); } while (bvec >= bio->bi_io_vec); bio_put(bio); return 0; } static int mpage_end_io_write(struct bio *bio, unsigned int bytes_done, int err) { const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags); struct bio_vec *bvec = bio->bi_io_vec + bio->bi_vcnt - 1; if (bio->bi_size) return 1; do { struct page *page = bvec->bv_page; if (--bvec >= bio->bi_io_vec) prefetchw(&bvec->bv_page->flags); if (!uptodate){ SetPageError(page); if (page->mapping) set_bit(AS_EIO, &page->mapping->flags); } end_page_writeback(page); } while (bvec >= bio->bi_io_vec); bio_put(bio); return 0; } static struct bio *mpage_bio_submit(int rw, struct bio *bio) { bio->bi_end_io = mpage_end_io_read; if (rw == WRITE) bio->bi_end_io = mpage_end_io_write; submit_bio(rw, bio); return NULL; } static struct bio * mpage_alloc(struct block_device *bdev, sector_t first_sector, int nr_vecs, unsigned int __nocast gfp_flags) { struct bio *bio; bio = bio_alloc(gfp_flags, nr_vecs); if (bio == NULL && (current->flags & PF_MEMALLOC)) { while (!bio && (nr_vecs /= 2)) bio = bio_alloc(gfp_flags, nr_vecs); } if (bio) { bio->bi_bdev = bdev; bio->bi_sector = first_sector; } return bio; } /* * support function for mpage_readpages. The fs supplied get_block might * return an up to date buffer. This is used to map that buffer into * the page, which allows readpage to avoid triggering a duplicate call * to get_block. * * The idea is to avoid adding buffers to pages that don't already have * them. So when the buffer is up to date and the page size == block size, * this marks the page up to date instead of adding new buffers. */ static void map_buffer_to_page(struct page *page, struct buffer_head *bh, int page_block) { struct inode *inode = page->mapping->host; struct buffer_head *page_bh, *head; int block = 0; if (!page_has_buffers(page)) { /* * don't make any buffers if there is only one buffer on * the page and the page just needs to be set up to date */ if (inode->i_blkbits == PAGE_CACHE_SHIFT && buffer_uptodate(bh)) { SetPageUptodate(page); return; } create_empty_buffers(page, 1 << inode->i_blkbits, 0); } head = page_buffers(page); page_bh = head; do { if (block == page_block) { page_bh->b_state = bh->b_state; page_bh->b_bdev = bh->b_bdev; page_bh->b_blocknr = bh->b_blocknr; break; } page_bh = page_bh->b_this_page; block++; } while (page_bh != head); } static struct bio * do_mpage_readpage(struct bio *bio, struct page *page, unsigned nr_pages, sector_t *last_block_in_bio, get_block_t get_block) { struct inode *inode = page->mapping->host; const unsigned blkbits = inode->i_blkbits; const unsigned blocks_per_page = PAGE_CACHE_SIZE >> blkbits; const unsigned blocksize = 1 << blkbits; sector_t block_in_file; sector_t last_block; sector_t blocks[MAX_BUF_PER_PAGE]; unsigned page_block; unsigned first_hole = blocks_per_page; struct block_device *bdev = NULL; struct buffer_head bh; int length; int fully_mapped = 1; if (page_has_buffers(page)) goto confused; block_in_file = page->index << (PAGE_CACHE_SHIFT - blkbits); last_block = (i_size_read(inode) + blocksize - 1) >> blkbits; bh.b_page = page; for (page_block = 0; page_block < blocks_per_page; page_block++, block_in_file++) { bh.b_state = 0; if (block_in_file < last_block) { if (get_block(inode, block_in_file, &bh, 0)) goto confused; } if (!buffer_mapped(&bh)) { fully_mapped = 0; if (first_hole == blocks_per_page) first_hole = page_block; continue; } /* some filesystems will copy data into the page during * the get_block call, in which case we don't want to * read it again. map_buffer_to_page copies the data * we just collected from get_block into the page's buffers * so readpage doesn't have to repeat the get_block call */ if (buffer_uptodate(&bh)) { map_buffer_to_page(page, &bh, page_block); goto confused; } if (first_hole != blocks_per_page) goto confused; /* hole -> non-hole */ /* Contiguous blocks? */ if (page_block && blocks[page_block-1] != bh.b_blocknr-1) goto confused; blocks[page_block] = bh.b_blocknr; bdev = bh.b_bdev; } if (first_hole != blocks_per_page) { char *kaddr = kmap_atomic(page, KM_USER0); memset(kaddr + (first_hole << blkbits), 0, PAGE_CACHE_SIZE - (first_hole << blkbits)); flush_dcache_page(page); kunmap_atomic(kaddr, KM_USER0); if (first_hole == 0) { SetPageUptodate(page); unlock_page(page); goto out; } } else if (fully_mapped) { SetPageMappedToDisk(page); } /* * This page will go to BIO. Do we need to send this BIO off first? */ if (bio && (*last_block_in_bio != blocks[0] - 1)) bio = mpage_bio_submit(READ, bio); alloc_new: if (bio == NULL) { bio = mpage_alloc(bdev, blocks[0] << (blkbits - 9), min_t(int, nr_pages, bio_get_nr_vecs(bdev)), GFP_KERNEL); if (bio == NULL) goto confused; } length = first_hole << blkbits; if (bio_add_page(bio, page, length, 0) < length) { bio = mpage_bio_submit(READ, bio); goto alloc_new; } if (buffer_boundary(&bh) || (first_hole != blocks_per_page)) bio = mpage_bio_submit(READ, bio); else *last_block_in_bio = blocks[blocks_per_page - 1]; out: return bio; confused: if (bio) bio = mpage_bio_submit(READ, bio); if (!PageUptodate(page)) block_read_full_page(page, get_block); else unlock_page(page); goto out; } /** * mpage_readpages - populate an address space with some pages, and * start reads against them. * * @mapping: the address_space * @pages: The address of a list_head which contains the target pages. These * pages have their ->index populated and are otherwise uninitialised. * * The page at @pages->prev has the lowest file offset, and reads should be * issued in @pages->prev to @pages->next order. * * @nr_pages: The number of pages at *@pages * @get_block: The filesystem's block mapper function. * * This function walks the pages and the blocks within each page, building and * emitting large BIOs. * * If anything unusual happens, such as: * * - encountering a page which has buffers * - encountering a page which has a non-hole after a hole * - encountering a page with non-contiguous blocks * * then this code just gives up and calls the buffer_head-based read function. * It does handle a page which has holes at the end - that is a common case: * the end-of-file on blocksize < PAGE_CACHE_SIZE setups. * * BH_Boundary explanation: * * There is a problem. The mpage read code assembles several pages, gets all * their disk mappings, and then submits them all. That's fine, but obtaining * the disk mappings may require I/O. Reads of indirect blocks, for example. * * So an mpage read of the first 16 blocks of an ext2 file will cause I/O to be * submitted in the following order: * 12 0 1 2 3 4 5 6 7 8 9 10 11 13 14 15 16 * because the indirect block has to be read to get the mappings of blocks * 13,14,15,16. Obviously, this impacts performance. * * So what we do it to allow the filesystem's get_block() function to set * BH_Boundary when it maps block 11. BH_Boundary says: mapping of the block * after this one will require I/O against a block which is probably close to * this one. So you should push what I/O you have currently accumulated. * * This all causes the disk requests to be issued in the correct order. */ int mpage_readpages(struct address_space *mapping, struct list_head *pages, unsigned nr_pages, get_block_t get_block) { struct bio *bio = NULL; unsigned page_idx; sector_t last_block_in_bio = 0; struct pagevec lru_pvec; pagevec_init(&lru_pvec, 0); for (page_idx = 0; page_idx < nr_pages; page_idx++) { struct page *page = list_entry(pages->prev, struct page, lru); prefetchw(&page->flags); list_del(&page->lru); if (!add_to_page_cache(page, mapping, page->index, GFP_KERNEL)) { bio = do_mpage_readpage(bio, page, nr_pages - page_idx, &last_block_in_bio, get_block); if (!pagevec_add(&lru_pvec, page)) __pagevec_lru_add(&lru_pvec); } else { page_cache_release(page); } } pagevec_lru_add(&lru_pvec); BUG_ON(!list_empty(pages)); if (bio) mpage_bio_submit(READ, bio); return 0; } EXPORT_SYMBOL(mpage_readpages); /* * This isn't called much at all */ int mpage_readpage(struct page *page, get_block_t get_block) { struct bio *bio = NULL; sector_t last_block_in_bio = 0; bio = do_mpage_readpage(bio, page, 1, &last_block_in_bio, get_block); if (bio) mpage_bio_submit(READ, bio); return 0; } EXPORT_SYMBOL(mpage_readpage); /* * Writing is not so simple. * * If the page has buffers then they will be used for obtaining the disk * mapping. We only support pages which are fully mapped-and-dirty, with a * special case for pages which are unmapped at the end: end-of-file. * * If the page has no buffers (preferred) then the page is mapped here. * * If all blocks are found to be contiguous then the page can go into the * BIO. Otherwise fall back to the mapping's writepage(). * * FIXME: This code wants an estimate of how many pages are still to be * written, so it can intelligently allocate a suitably-sized BIO. For now, * just allocate full-size (16-page) BIOs. */ static struct bio * __mpage_writepage(struct bio *bio, struct page *page, get_block_t get_block, sector_t *last_block_in_bio, int *ret, struct writeback_control *wbc, writepage_t writepage_fn) { struct address_space *mapping = page->mapping; struct inode *inode = page->mapping->host; const unsigned blkbits = inode->i_blkbits; unsigned long end_index; const unsigned blocks_per_page = PAGE_CACHE_SIZE >> blkbits; sector_t last_block; sector_t block_in_file; sector_t blocks[MAX_BUF_PER_PAGE]; unsigned page_block; unsigned first_unmapped = blocks_per_page; struct block_device *bdev = NULL; int boundary = 0; sector_t boundary_block = 0; struct block_device *boundary_bdev = NULL; int length; struct buffer_head map_bh; loff_t i_size = i_size_read(inode); if (page_has_buffers(page)) { struct buffer_head *head = page_buffers(page); struct buffer_head *bh = head; /* If they're all mapped and dirty, do it */ page_block = 0; do { BUG_ON(buffer_locked(bh)); if (!buffer_mapped(bh)) { /* * unmapped dirty buffers are created by * __set_page_dirty_buffers -> mmapped data */ if (buffer_dirty(bh)) goto confused; if (first_unmapped == blocks_per_page) first_unmapped = page_block; continue; } if (first_unmapped != blocks_per_page) goto confused; /* hole -> non-hole */ if (!buffer_dirty(bh) || !buffer_uptodate(bh)) goto confused; if (page_block) { if (bh->b_blocknr != blocks[page_block-1] + 1) goto confused; } blocks[page_block++] = bh->b_blocknr; boundary = buffer_boundary(bh); if (boundary) { boundary_block = bh->b_blocknr; boundary_bdev = bh->b_bdev; } bdev = bh->b_bdev; } while ((bh = bh->b_this_page) != head); if (first_unmapped) goto page_is_mapped; /* * Page has buffers, but they are all unmapped. The page was * created by pagein or read over a hole which was handled by * block_read_full_page(). If this address_space is also * using mpage_readpages then this can rarely happen. */ goto confused; } /* * The page has no buffers: map it to disk */ BUG_ON(!PageUptodate(page)); block_in_file = page->index << (PAGE_CACHE_SHIFT - blkbits); last_block = (i_size - 1) >> blkbits; map_bh.b_page = page; for (page_block = 0; page_block < blocks_per_page; ) { map_bh.b_state = 0; if (get_block(inode, block_in_file, &map_bh, 1)) goto confused; if (buffer_new(&map_bh)) unmap_underlying_metadata(map_bh.b_bdev, map_bh.b_blocknr); if (buffer_boundary(&map_bh)) { boundary_block = map_bh.b_blocknr; boundary_bdev = map_bh.b_bdev; } if (page_block) { if (map_bh.b_blocknr != blocks[page_block-1] + 1) goto confused; } blocks[page_block++] = map_bh.b_blocknr; boundary = buffer_boundary(&map_bh); bdev = map_bh.b_bdev; if (block_in_file == last_block) break; block_in_file++; } BUG_ON(page_block == 0); first_unmapped = page_block; page_is_mapped: end_index = i_size >> PAGE_CACHE_SHIFT;