From: Shaohua Li Subject: [RFC]jbd2: use GFP_NOFS for blkdev_issue_flush Date: Fri, 13 Apr 2012 10:27:35 +0800 Message-ID: <4F878F17.2030900@kernel.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit To: linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org, tytso@mit.edu Return-path: Sender: linux-fsdevel-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org flush request is issued in transaction commit code path, so looks using GFP_KERNEL to allocate memory for flush request bio falls into the classic deadlock issue. I saw btrfs and dm get it right, but ext4, xfs and md are using GFP_KERNEL, which makes me confused. Hoping filesystem developers clarify. Signed-off-by: Shaohua Li --- fs/jbd2/commit.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) Index: linux/fs/jbd2/commit.c =================================================================== --- linux.orig/fs/jbd2/commit.c 2012-04-13 09:57:51.785506925 +0800 +++ linux/fs/jbd2/commit.c 2012-04-13 09:58:29.585498773 +0800 @@ -723,7 +723,7 @@ start_journal_io: if (commit_transaction->t_need_data_flush && (journal->j_fs_dev != journal->j_dev) && (journal->j_flags & JBD2_BARRIER)) - blkdev_issue_flush(journal->j_fs_dev, GFP_KERNEL, NULL); + blkdev_issue_flush(journal->j_fs_dev, GFP_NOFS, NULL); /* Done it all: now write the commit record asynchronously. */ if (JBD2_HAS_INCOMPAT_FEATURE(journal, @@ -859,7 +859,7 @@ wait_for_iobuf: if (JBD2_HAS_INCOMPAT_FEATURE(journal, JBD2_FEATURE_INCOMPAT_ASYNC_COMMIT) && journal->j_flags & JBD2_BARRIER) { - blkdev_issue_flush(journal->j_dev, GFP_KERNEL, NULL); + blkdev_issue_flush(journal->j_dev, GFP_NOFS, NULL); } if (err)