From: Theodore Ts'o Subject: Re: [PATCH] ext4, jbd2: add REQ_FUA flag when recording an error flag Date: Thu, 23 Jul 2015 09:48:02 -0400 Message-ID: <20150723134802.GK2944@thunk.org> References: <1153399123.83011435025959601.JavaMail.weblogic@ep2mlwas05d> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: daeho.jeong@samsung.com, linux-ext4@vger.kernel.org To: Daeho Jeong Return-path: Received: from imap.thunk.org ([74.207.234.97]:41915 "EHLO imap.thunk.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752488AbbGWNsG (ORCPT ); Thu, 23 Jul 2015 09:48:06 -0400 Content-Disposition: inline In-Reply-To: Sender: linux-ext4-owner@vger.kernel.org List-ID: > @@ -4638,7 +4639,10 @@ static int ext4_commit_super(struct super_block *sb, > int sync) > ext4_superblock_csum_set(sb); > mark_buffer_dirty(sbh); > if (sync) { > - error = sync_dirty_buffer(sbh); > + if (journal->j_flags & JBD2_BARRIER) > + error = __sync_dirty_buffer(sbh, WRITE_FUA); > + else > + error = sync_dirty_buffer(sbh); > if (error) > return error; The problem with this is that the journal structure will not be present in no-journal mode, so it will result in a NULL dereference. So I've changed this to use test_opt(sb, BARRIER) instead. - Ted commit 564bc402526e437729ecafe3c3511f7cab9f0327 Author: Daeho Jeong Date: Thu Jul 23 09:46:11 2015 -0400 ext4, jbd2: add REQ_FUA flag when recording an error in the superblock When an error condition is detected, an error status should be recorded into superblocks of EXT4 or JBD2. However, the write request is submitted now without REQ_FUA flag, even in "barrier=1" mode, which is followed by panic() function in "errors=panic" mode. On mobile devices which make whole system reset as soon as kernel panic occurs, this write request containing an error flag will disappear just from storage cache without written to the physical cells. Therefore, when next start, even forever, the error flag cannot be shown in both superblocks, and e2fsck cannot fix the filesystem problems automatically, unless e2fsck is executed in force checking mode. [ Changed use test_opt(sb, BARRIER) of checking the journal flags -- TYT ] Signed-off-by: Daeho Jeong Signed-off-by: Theodore Ts'o diff --git a/fs/ext4/super.c b/fs/ext4/super.c index 14909cd..a51db9c 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -4667,7 +4667,8 @@ static int ext4_commit_super(struct super_block *sb, int sync) ext4_superblock_csum_set(sb); mark_buffer_dirty(sbh); if (sync) { - error = sync_dirty_buffer(sbh); + error = __sync_dirty_buffer(sbh, + test_opt(sb, BARRIER) ? WRITE_FUA : WRITE_SYNC); if (error) return error; diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c index 4ff3fad..fe1b4bd 100644 --- a/fs/jbd2/journal.c +++ b/fs/jbd2/journal.c @@ -1456,7 +1456,7 @@ void jbd2_journal_update_sb_errno(journal_t *journal) sb->s_errno = cpu_to_be32(journal->j_errno); read_unlock(&journal->j_state_lock); - jbd2_write_superblock(journal, WRITE_SYNC); + jbd2_write_superblock(journal, WRITE_FUA); } EXPORT_SYMBOL(jbd2_journal_update_sb_errno);