From: Theodore Ts'o Subject: [PATCH 2/2] ext4: Fix waiting and sending of a barrier in ext4_sync_file() Date: Sun, 22 May 2011 17:13:45 -0400 Message-ID: <1306098825-469-2-git-send-email-tytso@mit.edu> References: <20110522211239.GB10009@thunk.org> Cc: Jan Kara , "Theodore Ts'o" To: Ext4 Developers List Return-path: Received: from li9-11.members.linode.com ([67.18.176.11]:50431 "EHLO test.thunk.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754927Ab1EVVNr (ORCPT ); Sun, 22 May 2011 17:13:47 -0400 In-Reply-To: <20110522211239.GB10009@thunk.org> Sender: linux-ext4-owner@vger.kernel.org List-ID: From: Jan Kara jbd2_log_start_commit() returns 1 only when we really start a transaction. But we also need to wait for a transaction when the commit is already running. Fix this problem by waiting for transaction commit unconditionally (which is just a quick check if the transaction is already committed). Also we have to be more careful with sending of a barrier because when transaction is being committed in parallel to ext4_sync_file() running, we cannot be sure that the barrier the journalling code sends happens after we wrote all the data for fsync (note that not every data writeout needs to trigger metadata changes thus commit of some metadata changes can be running while other data is still written out). So use jbd2_will_send_data_barrier() helper to detect the common cases when we can be sure barrier will be issued by the commit code and issue the barrier ourselves in the remaining cases. [ Modified by tytso so that the external journal cases are handled in ext4_sync_file() to avoid needlessly issuing extra flush requests in the data=ordered and data=journalled cases. ] Signed-off-by: Jan Kara Signed-off-by: "Theodore Ts'o" --- fs/ext4/fsync.c | 31 ++++++++++++++++++++----------- 1 files changed, 20 insertions(+), 11 deletions(-) diff --git a/fs/ext4/fsync.c b/fs/ext4/fsync.c index 60fe572..b0e03fa 100644 --- a/fs/ext4/fsync.c +++ b/fs/ext4/fsync.c @@ -172,6 +172,7 @@ int ext4_sync_file(struct file *file, int datasync) journal_t *journal = EXT4_SB(inode->i_sb)->s_journal; int ret; tid_t commit_tid; + bool needs_barrier = false; J_ASSERT(ext4_journal_current_handle() == NULL); @@ -211,22 +212,30 @@ int ext4_sync_file(struct file *file, int datasync) } commit_tid = datasync ? ei->i_datasync_tid : ei->i_sync_tid; - if (jbd2_log_start_commit(journal, commit_tid)) { + if (journal->j_flags & JBD2_BARRIER) { /* * When the journal is on a different device than the - * fs data disk, we need to issue the barrier in - * writeback mode. (In ordered mode, the jbd2 layer - * will take care of issuing the barrier. In + * fs data disk, when data=writeback, we need to issue + * a barrier unconditionally. (In ordered mode, the + * jbd2 layer will take care of issuing the barrier if + * there were any writes associated with the inode; in * data=journal, all of the data blocks are written to * the journal device.) */ - if (ext4_should_writeback_data(inode) && - (journal->j_fs_dev != journal->j_dev) && - (journal->j_flags & JBD2_BARRIER)) - blkdev_issue_flush(inode->i_sb->s_bdev, GFP_KERNEL, - NULL); - ret = jbd2_log_wait_commit(journal, commit_tid); - } else if (journal->j_flags & JBD2_BARRIER) + if ((journal->j_fs_dev != journal->j_dev) && + ext4_should_writeback_data(inode)) + needs_barrier = true; + else if (!jbd2_trans_will_send_data_barrier(journal, + commit_tid)) + /* + * If the journal layer isn't going to issue + * the barrier, then we'd better. + */ + needs_barrier = true; + } + jbd2_log_start_commit(journal, commit_tid); + ret = jbd2_log_wait_commit(journal, commit_tid); + if (needs_barrier) blkdev_issue_flush(inode->i_sb->s_bdev, GFP_KERNEL, NULL); out: trace_ext4_sync_file_exit(inode, ret); -- 1.7.3.1