From: Theodore Ts'o Subject: [PATCH 3/3] ext3: Avoid starting a transaction in writepage when not necessary Date: Fri, 27 Mar 2009 16:24:31 -0400 Message-ID: <1238185471-31152-4-git-send-email-tytso@mit.edu> References: <1238185471-31152-1-git-send-email-tytso@mit.edu> <1238185471-31152-2-git-send-email-tytso@mit.edu> <1238185471-31152-3-git-send-email-tytso@mit.edu> Cc: Ext4 Developers List , jack@suse.cz, "Theodore Ts'o" To: Linux Kernel Developers List Return-path: Received: from THUNK.ORG ([69.25.196.29]:45716 "EHLO thunker.thunk.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1761413AbZC0UYf (ORCPT ); Fri, 27 Mar 2009 16:24:35 -0400 In-Reply-To: <1238185471-31152-3-git-send-email-tytso@mit.edu> Sender: linux-ext4-owner@vger.kernel.org List-ID: From: Jan Kara We don't have to start a transaction in writepage() when all the blocks are a properly allocated. Even in ordered mode either the data has been written via write() and they are thus already added to transaction's list or the data was written via mmap and then it's random in which transaction they get written anyway. This should help VM to pageout dirty memory without blocking on transaction commits. Signed-off-by: Jan Kara Signed-off-by: "Theodore Ts'o" --- fs/ext3/inode.c | 19 ++++++++++++++----- 1 files changed, 14 insertions(+), 5 deletions(-) diff --git a/fs/ext3/inode.c b/fs/ext3/inode.c index 5fa453b..a9c12b1 100644 --- a/fs/ext3/inode.c +++ b/fs/ext3/inode.c @@ -1435,6 +1435,10 @@ static int journal_dirty_data_fn(handle_t *handle, struct buffer_head *bh) return 0; } +static int buffer_unmapped(handle_t *handle, struct buffer_head *bh) +{ + return !buffer_mapped(bh); +} /* * Note that we always start a transaction even if we're not journalling * data. This is to preserve ordering: any hole instantiation within @@ -1505,6 +1509,16 @@ static int ext3_ordered_writepage(struct page *page, if (ext3_journal_current_handle()) goto out_fail; + if (!page_has_buffers(page)) { + create_empty_buffers(page, inode->i_sb->s_blocksize, + (1 << BH_Dirty)|(1 << BH_Uptodate)); + } else if (!walk_page_buffers(NULL, page_buffers(page), 0, PAGE_CACHE_SIZE, NULL, buffer_unmapped)) { + /* Provide NULL instead of get_block so that we catch bugs if buffers weren't really mapped */ + return block_write_full_page(page, NULL, wbc); + } + page_bufs = page_buffers(page); + + handle = ext3_journal_start(inode, ext3_writepage_trans_blocks(inode)); if (IS_ERR(handle)) { @@ -1512,11 +1526,6 @@ static int ext3_ordered_writepage(struct page *page, goto out_fail; } - if (!page_has_buffers(page)) { - create_empty_buffers(page, inode->i_sb->s_blocksize, - (1 << BH_Dirty)|(1 << BH_Uptodate)); - } - page_bufs = page_buffers(page); walk_page_buffers(handle, page_bufs, 0, PAGE_CACHE_SIZE, NULL, bget_one); -- 1.5.6.3