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fs/mpage.c
19.9 KB
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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. * |
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* 15May2002 Andrew Morton |
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* Initial version * 27Jun2002 axboe@suse.de * use bio_add_page() to build bio's just the right size */ #include <linux/kernel.h> |
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#include <linux/export.h> |
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#include <linux/mm.h> #include <linux/kdev_t.h> |
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#include <linux/gfp.h> |
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#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> |
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#include <linux/cleancache.h> |
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#include "internal.h" |
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/* * 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. */ |
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static void mpage_end_io(struct bio *bio, int err) |
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{ |
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struct bio_vec *bv; int i; |
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|
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bio_for_each_segment_all(bv, bio, i) { struct page *page = bv->bv_page; |
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page_endio(page, bio_data_dir(bio), err); |
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} |
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bio_put(bio); |
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} |
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static struct bio *mpage_bio_submit(int rw, struct bio *bio) |
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{ |
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bio->bi_end_io = mpage_end_io; |
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guard_bio_eod(rw, bio); |
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submit_bio(rw, bio); return NULL; } static struct bio * mpage_alloc(struct block_device *bdev, sector_t first_sector, int nr_vecs, |
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gfp_t gfp_flags) |
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{ 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; |
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bio->bi_iter.bi_sector = first_sector; |
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} 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); } |
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/* * This is the worker routine which does all the work of mapping the disk * blocks and constructs largest possible bios, submits them for IO if the * blocks are not contiguous on the disk. * * We pass a buffer_head back and forth and use its buffer_mapped() flag to * represent the validity of its disk mapping and to decide when to do the next * get_block() call. */ |
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static struct bio * do_mpage_readpage(struct bio *bio, struct page *page, unsigned nr_pages, |
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sector_t *last_block_in_bio, struct buffer_head *map_bh, unsigned long *first_logical_block, get_block_t get_block) |
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{ 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; |
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sector_t last_block_in_file; |
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sector_t blocks[MAX_BUF_PER_PAGE]; unsigned page_block; unsigned first_hole = blocks_per_page; struct block_device *bdev = NULL; |
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int length; int fully_mapped = 1; |
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unsigned nblocks; unsigned relative_block; |
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if (page_has_buffers(page)) goto confused; |
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block_in_file = (sector_t)page->index << (PAGE_CACHE_SHIFT - blkbits); |
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last_block = block_in_file + nr_pages * blocks_per_page; last_block_in_file = (i_size_read(inode) + blocksize - 1) >> blkbits; if (last_block > last_block_in_file) last_block = last_block_in_file; page_block = 0; /* * Map blocks using the result from the previous get_blocks call first. */ nblocks = map_bh->b_size >> blkbits; if (buffer_mapped(map_bh) && block_in_file > *first_logical_block && block_in_file < (*first_logical_block + nblocks)) { unsigned map_offset = block_in_file - *first_logical_block; unsigned last = nblocks - map_offset; for (relative_block = 0; ; relative_block++) { if (relative_block == last) { clear_buffer_mapped(map_bh); break; } if (page_block == blocks_per_page) break; blocks[page_block] = map_bh->b_blocknr + map_offset + relative_block; page_block++; block_in_file++; } bdev = map_bh->b_bdev; } /* * Then do more get_blocks calls until we are done with this page. */ map_bh->b_page = page; while (page_block < blocks_per_page) { map_bh->b_state = 0; map_bh->b_size = 0; |
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|
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if (block_in_file < last_block) { |
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map_bh->b_size = (last_block-block_in_file) << blkbits; if (get_block(inode, block_in_file, map_bh, 0)) |
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goto confused; |
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*first_logical_block = block_in_file; |
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} |
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if (!buffer_mapped(map_bh)) { |
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fully_mapped = 0; if (first_hole == blocks_per_page) first_hole = page_block; |
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page_block++; block_in_file++; |
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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 */ |
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if (buffer_uptodate(map_bh)) { map_buffer_to_page(page, map_bh, page_block); |
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goto confused; } if (first_hole != blocks_per_page) goto confused; /* hole -> non-hole */ /* Contiguous blocks? */ |
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if (page_block && blocks[page_block-1] != map_bh->b_blocknr-1) |
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goto confused; |
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nblocks = map_bh->b_size >> blkbits; for (relative_block = 0; ; relative_block++) { if (relative_block == nblocks) { clear_buffer_mapped(map_bh); break; } else if (page_block == blocks_per_page) break; blocks[page_block] = map_bh->b_blocknr+relative_block; page_block++; block_in_file++; } bdev = map_bh->b_bdev; |
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} if (first_hole != blocks_per_page) { |
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zero_user_segment(page, first_hole << blkbits, PAGE_CACHE_SIZE); |
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if (first_hole == 0) { SetPageUptodate(page); unlock_page(page); goto out; } } else if (fully_mapped) { SetPageMappedToDisk(page); } |
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if (fully_mapped && blocks_per_page == 1 && !PageUptodate(page) && cleancache_get_page(page) == 0) { SetPageUptodate(page); goto confused; } |
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/* * 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) { |
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if (first_hole == blocks_per_page) { if (!bdev_read_page(bdev, blocks[0] << (blkbits - 9), page)) goto out; } |
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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; } |
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relative_block = block_in_file - *first_logical_block; nblocks = map_bh->b_size >> blkbits; if ((buffer_boundary(map_bh) && relative_block == nblocks) || (first_hole != blocks_per_page)) |
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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; } |
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/** |
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* mpage_readpages - populate an address space with some pages & start reads against them |
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* @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. |
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* The page at @pages->prev has the lowest file offset, and reads should be * issued in @pages->prev to @pages->next order. |
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* @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 |
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* |
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* 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. */ |
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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; |
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struct buffer_head map_bh; unsigned long first_logical_block = 0; |
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|
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map_bh.b_state = 0; map_bh.b_size = 0; |
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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); |
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if (!add_to_page_cache_lru(page, mapping, |
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page->index, GFP_KERNEL)) { bio = do_mpage_readpage(bio, page, nr_pages - page_idx, |
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&last_block_in_bio, &map_bh, &first_logical_block, get_block); |
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} |
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page_cache_release(page); |
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} |
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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; |
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struct buffer_head map_bh; unsigned long first_logical_block = 0; |
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|
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map_bh.b_state = 0; map_bh.b_size = 0; |
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bio = do_mpage_readpage(bio, page, 1, &last_block_in_bio, &map_bh, &first_logical_block, get_block); |
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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. */ |
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|
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struct mpage_data { struct bio *bio; sector_t last_block_in_bio; get_block_t *get_block; unsigned use_writepage; }; |
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/* * We have our BIO, so we can now mark the buffers clean. Make * sure to only clean buffers which we know we'll be writing. */ static void clean_buffers(struct page *page, unsigned first_unmapped) { unsigned buffer_counter = 0; struct buffer_head *bh, *head; if (!page_has_buffers(page)) return; head = page_buffers(page); bh = head; do { if (buffer_counter++ == first_unmapped) break; clear_buffer_dirty(bh); bh = bh->b_this_page; } while (bh != head); /* * we cannot drop the bh if the page is not uptodate or a concurrent * readpage would fail to serialize with the bh and it would read from * disk before we reach the platter. */ if (buffer_heads_over_limit && PageUptodate(page)) try_to_free_buffers(page); } |
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static int __mpage_writepage(struct page *page, struct writeback_control *wbc, |
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void *data) |
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{ |
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struct mpage_data *mpd = data; struct bio *bio = mpd->bio; |
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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); |
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int ret = 0; |
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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)); |
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block_in_file = (sector_t)page->index << (PAGE_CACHE_SHIFT - blkbits); |
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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; |
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map_bh.b_size = 1 << blkbits; |
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if (mpd->get_block(inode, block_in_file, &map_bh, 1)) |
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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; if (page->index >= end_index) { /* * The page straddles i_size. It must be zeroed out on each |
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* and every writepage invocation because it may be mmapped. |
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* "A file is mapped in multiples of the page size. For a file * that is not a multiple of the page size, the remaining memory * is zeroed when mapped, and writes to that region are not * written out to the file." */ unsigned offset = i_size & (PAGE_CACHE_SIZE - 1); |
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if (page->index > end_index || !offset) goto confused; |
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zero_user_segment(page, offset, PAGE_CACHE_SIZE); |
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} /* * This page will go to BIO. Do we need to send this BIO off first? */ |
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if (bio && mpd->last_block_in_bio != blocks[0] - 1) |
1da177e4c Linux-2.6.12-rc2 |
582 583 584 585 |
bio = mpage_bio_submit(WRITE, bio); alloc_new: if (bio == NULL) { |
47a191fd3 fs/block_dev.c: a... |
586 587 588 589 590 591 592 |
if (first_unmapped == blocks_per_page) { if (!bdev_write_page(bdev, blocks[0] << (blkbits - 9), page, wbc)) { clean_buffers(page, first_unmapped); goto out; } } |
1da177e4c Linux-2.6.12-rc2 |
593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 |
bio = mpage_alloc(bdev, blocks[0] << (blkbits - 9), bio_get_nr_vecs(bdev), GFP_NOFS|__GFP_HIGH); if (bio == NULL) goto confused; } /* * Must try to add the page before marking the buffer clean or * the confused fail path above (OOM) will be very confused when * it finds all bh marked clean (i.e. it will not write anything) */ length = first_unmapped << blkbits; if (bio_add_page(bio, page, length, 0) < length) { bio = mpage_bio_submit(WRITE, bio); goto alloc_new; } |
90768eee4 fs/mpage.c: facto... |
609 |
clean_buffers(page, first_unmapped); |
1da177e4c Linux-2.6.12-rc2 |
610 611 612 613 614 615 616 617 618 619 620 |
BUG_ON(PageWriteback(page)); set_page_writeback(page); unlock_page(page); if (boundary || (first_unmapped != blocks_per_page)) { bio = mpage_bio_submit(WRITE, bio); if (boundary_block) { write_boundary_block(boundary_bdev, boundary_block, 1 << blkbits); } } else { |
0ea971801 consolidate gener... |
621 |
mpd->last_block_in_bio = blocks[blocks_per_page - 1]; |
1da177e4c Linux-2.6.12-rc2 |
622 623 624 625 626 627 |
} goto out; confused: if (bio) bio = mpage_bio_submit(WRITE, bio); |
0ea971801 consolidate gener... |
628 629 |
if (mpd->use_writepage) { ret = mapping->a_ops->writepage(page, wbc); |
1da177e4c Linux-2.6.12-rc2 |
630 |
} else { |
0ea971801 consolidate gener... |
631 |
ret = -EAGAIN; |
1da177e4c Linux-2.6.12-rc2 |
632 633 634 635 636 |
goto out; } /* * The caller has a ref on the inode, so *mapping is stable */ |
0ea971801 consolidate gener... |
637 |
mapping_set_error(mapping, ret); |
1da177e4c Linux-2.6.12-rc2 |
638 |
out: |
0ea971801 consolidate gener... |
639 640 |
mpd->bio = bio; return ret; |
1da177e4c Linux-2.6.12-rc2 |
641 642 643 |
} /** |
78a4a50a8 docbook: fix file... |
644 |
* mpage_writepages - walk the list of dirty pages of the given address space & writepage() all of them |
1da177e4c Linux-2.6.12-rc2 |
645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 |
* @mapping: address space structure to write * @wbc: subtract the number of written pages from *@wbc->nr_to_write * @get_block: the filesystem's block mapper function. * If this is NULL then use a_ops->writepage. Otherwise, go * direct-to-BIO. * * This is a library function, which implements the writepages() * address_space_operation. * * If a page is already under I/O, generic_writepages() skips it, even * if it's dirty. This is desirable behaviour for memory-cleaning writeback, * but it is INCORRECT for data-integrity system calls such as fsync(). fsync() * and msync() need to guarantee that all the data which was dirty at the time * the call was made get new I/O started against them. If wbc->sync_mode is * WB_SYNC_ALL then we were called for data integrity and we must wait for * existing IO to complete. */ int mpage_writepages(struct address_space *mapping, struct writeback_control *wbc, get_block_t get_block) { |
2ed1a6bcf fs: make mpage re... |
666 |
struct blk_plug plug; |
0ea971801 consolidate gener... |
667 |
int ret; |
2ed1a6bcf fs: make mpage re... |
668 |
blk_start_plug(&plug); |
0ea971801 consolidate gener... |
669 670 671 672 673 674 675 676 677 678 679 680 681 |
if (!get_block) ret = generic_writepages(mapping, wbc); else { struct mpage_data mpd = { .bio = NULL, .last_block_in_bio = 0, .get_block = get_block, .use_writepage = 1, }; ret = write_cache_pages(mapping, wbc, __mpage_writepage, &mpd); if (mpd.bio) mpage_bio_submit(WRITE, mpd.bio); |
1da177e4c Linux-2.6.12-rc2 |
682 |
} |
2ed1a6bcf fs: make mpage re... |
683 |
blk_finish_plug(&plug); |
1da177e4c Linux-2.6.12-rc2 |
684 685 686 |
return ret; } EXPORT_SYMBOL(mpage_writepages); |
1da177e4c Linux-2.6.12-rc2 |
687 688 689 690 |
int mpage_writepage(struct page *page, get_block_t get_block, struct writeback_control *wbc) { |
0ea971801 consolidate gener... |
691 692 693 694 695 696 697 698 699 |
struct mpage_data mpd = { .bio = NULL, .last_block_in_bio = 0, .get_block = get_block, .use_writepage = 0, }; int ret = __mpage_writepage(page, wbc, &mpd); if (mpd.bio) mpage_bio_submit(WRITE, mpd.bio); |
1da177e4c Linux-2.6.12-rc2 |
700 701 702 |
return ret; } EXPORT_SYMBOL(mpage_writepage); |