From: "Aneesh Kumar K.V" Subject: [PATCH -V3] ext4: Fix file fragmentation during large file write. Date: Thu, 16 Oct 2008 16:50:26 +0530 Message-ID: <1224156026-11095-2-git-send-email-aneesh.kumar@linux.vnet.ibm.com> References: <1224156026-11095-1-git-send-email-aneesh.kumar@linux.vnet.ibm.com> Cc: linux-ext4@vger.kernel.org To: aneesh.kumar@linux.vnet.ibm.com, cmm@us.ibm.com, tytso@mit.edu, sandeen@redhat.com, chris.mason@oracle.com Return-path: Received: from e28smtp03.in.ibm.com ([59.145.155.3]:54846 "EHLO e28esmtp03.in.ibm.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1754291AbYJPLUk (ORCPT ); Thu, 16 Oct 2008 07:20:40 -0400 Received: from d28relay04.in.ibm.com (d28relay04.in.ibm.com [9.184.220.61]) by e28esmtp03.in.ibm.com (8.13.1/8.13.1) with ESMTP id m9GBKbWv015899 for ; Thu, 16 Oct 2008 16:50:37 +0530 Received: from d28av02.in.ibm.com (d28av02.in.ibm.com [9.184.220.64]) by d28relay04.in.ibm.com (8.13.8/8.13.8/NCO v9.1) with ESMTP id m9GBKb4F1822732 for ; Thu, 16 Oct 2008 16:50:37 +0530 Received: from d28av02.in.ibm.com (loopback [127.0.0.1]) by d28av02.in.ibm.com (8.13.1/8.13.3) with ESMTP id m9GBKavr023047 for ; Thu, 16 Oct 2008 22:20:37 +1100 In-Reply-To: <1224156026-11095-1-git-send-email-aneesh.kumar@linux.vnet.ibm.com> Sender: linux-ext4-owner@vger.kernel.org List-ID: The range_cyclic writeback mode uses the address_space writeback_index as the start index for writeback. With delayed allocation we were updating writeback_index wrongly resulting in highly fragmented file. Number of extents reduced from 4000 to 27 for a 3GB file with the below patch. Signed-off-by: Aneesh Kumar K.V Signed-off-by: Theodore Ts'o --- fs/ext4/inode.c | 91 ++++++++++++++++++++++++++++++++++-------------------- 1 files changed, 57 insertions(+), 34 deletions(-) diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c index cba7960..46ffd0a 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -1648,6 +1648,7 @@ static int mpage_da_submit_io(struct mpage_da_data *mpd) int ret = 0, err, nr_pages, i; unsigned long index, end; struct pagevec pvec; + long pages_skipped; BUG_ON(mpd->next_page <= mpd->first_page); pagevec_init(&pvec, 0); @@ -1655,7 +1656,6 @@ static int mpage_da_submit_io(struct mpage_da_data *mpd) end = mpd->next_page - 1; while (index <= end) { - /* XXX: optimize tail */ /* * We can use PAGECACHE_TAG_DIRTY lookup here because * even though we have cleared the dirty flag on the page @@ -1673,8 +1673,13 @@ static int mpage_da_submit_io(struct mpage_da_data *mpd) for (i = 0; i < nr_pages; i++) { struct page *page = pvec.pages[i]; + pages_skipped = mpd->wbc->pages_skipped; err = mapping->a_ops->writepage(page, mpd->wbc); - if (!err) + if (!err && (pages_skipped == mpd->wbc->pages_skipped)) + /* + * have successfully written the page + * without skipping the same + */ mpd->pages_written++; /* * In error case, we have to continue because @@ -2110,7 +2115,6 @@ static int mpage_da_writepages(struct address_space *mapping, struct writeback_control *wbc, struct mpage_da_data *mpd) { - long to_write; int ret; if (!mpd->get_block) @@ -2125,19 +2129,18 @@ static int mpage_da_writepages(struct address_space *mapping, mpd->pages_written = 0; mpd->retval = 0; - to_write = wbc->nr_to_write; - ret = write_cache_pages(mapping, wbc, __mpage_da_writepage, mpd); - /* * Handle last extent of pages */ if (!mpd->io_done && mpd->next_page != mpd->first_page) { if (mpage_da_map_blocks(mpd) == 0) mpage_da_submit_io(mpd); - } - wbc->nr_to_write = to_write - mpd->pages_written; + mpd->io_done = 1; + ret = MPAGE_DA_EXTENT_TAIL; + } + wbc->nr_to_write -= mpd->pages_written; return ret; } @@ -2366,11 +2369,14 @@ static int ext4_da_writepages_trans_blocks(struct inode *inode) static int ext4_da_writepages(struct address_space *mapping, struct writeback_control *wbc) { + pgoff_t index; + int range_whole = 0; handle_t *handle = NULL; struct mpage_da_data mpd; struct inode *inode = mapping->host; + int no_nrwrite_index_update; + long pages_written = 0, pages_skipped; int needed_blocks, ret = 0, nr_to_writebump = 0; - long to_write, pages_skipped = 0; struct ext4_sb_info *sbi = EXT4_SB(mapping->host->i_sb); /* @@ -2390,16 +2396,26 @@ static int ext4_da_writepages(struct address_space *mapping, nr_to_writebump = sbi->s_mb_stream_request - wbc->nr_to_write; wbc->nr_to_write = sbi->s_mb_stream_request; } + if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX) + range_whole = 1; - - pages_skipped = wbc->pages_skipped; + if (wbc->range_cyclic) + index = mapping->writeback_index; + else + index = wbc->range_start >> PAGE_CACHE_SHIFT; mpd.wbc = wbc; mpd.inode = mapping->host; -restart_loop: - to_write = wbc->nr_to_write; - while (!ret && to_write > 0) { + /* + * we don't want write_cache_pages to update + * nr_to_write and writeback_index + */ + no_nrwrite_index_update = wbc->no_nrwrite_index_update; + wbc->no_nrwrite_index_update = 1; + pages_skipped = wbc->pages_skipped; + + while (!ret && wbc->nr_to_write > 0) { /* * we insert one extent at a time. So we need @@ -2420,46 +2436,53 @@ static int ext4_da_writepages(struct address_space *mapping, dump_stack(); goto out_writepages; } - to_write -= wbc->nr_to_write; - mpd.get_block = ext4_da_get_block_write; ret = mpage_da_writepages(mapping, wbc, &mpd); ext4_journal_stop(handle); - if (mpd.retval == -ENOSPC) + if (mpd.retval == -ENOSPC) { + /* commit the transaction which would + * free blocks released in the transaction + * and try again + */ jbd2_journal_force_commit_nested(sbi->s_journal); - - /* reset the retry count */ - if (ret == MPAGE_DA_EXTENT_TAIL) { + wbc->pages_skipped = pages_skipped; + ret = 0; + } else if (ret == MPAGE_DA_EXTENT_TAIL) { /* * got one extent now try with * rest of the pages */ - to_write += wbc->nr_to_write; + pages_written += mpd.pages_written; + wbc->pages_skipped = pages_skipped; ret = 0; - } else if (wbc->nr_to_write) { + } else if (wbc->nr_to_write) /* * There is no more writeout needed * or we requested for a noblocking writeout * and we found the device congested */ - to_write += wbc->nr_to_write; break; - } - wbc->nr_to_write = to_write; - } - - if (!wbc->range_cyclic && (pages_skipped != wbc->pages_skipped)) { - /* We skipped pages in this loop */ - wbc->nr_to_write = to_write + - wbc->pages_skipped - pages_skipped; - wbc->pages_skipped = pages_skipped; - goto restart_loop; } + if (pages_skipped != wbc->pages_skipped) + printk(KERN_EMERG "This should not happen leaving %s " + "with nr_to_write = %ld ret = %d\n", + __func__, wbc->nr_to_write, ret); + + /* Update index */ + index += pages_written; + if (wbc->range_cyclic || (range_whole && wbc->nr_to_write > 0)) + /* + * set the writeback_index so that range_cyclic + * mode will write it back later + */ + mapping->writeback_index = index; out_writepages: - wbc->nr_to_write = to_write - nr_to_writebump; + if (!no_nrwrite_index_update) + wbc->no_nrwrite_index_update = 0; + wbc->nr_to_write -= nr_to_writebump; return ret; } -- 1.6.0.2.526.g5c283