linux-kernel - [PATCH 3.16 240/328] ext4: don't mark mmp buffer head dirty

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Message-ID: <lsq.1544392233.338095852@decadent.org.uk>
Date:   Sun, 09 Dec 2018 21:50:33 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "Li Dongyang" <dongyangli@....com>,
        "Theodore Ts'o" <tytso@....edu>,
        "Andreas Dilger" <adilger@...ger.ca>
Subject: [PATCH 3.16 240/328] ext4: don't mark mmp buffer head dirty

3.16.62-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Li Dongyang <dongyangli@....com>

commit fe18d649891d813964d3aaeebad873f281627fbc upstream.

Marking mmp bh dirty before writing it will make writeback
pick up mmp block later and submit a write, we don't want the
duplicate write as kmmpd thread should have full control of
reading and writing the mmp block.
Another reason is we will also have random I/O error on
the writeback request when blk integrity is enabled, because
kmmpd could modify the content of the mmp block(e.g. setting
new seq and time) while the mmp block is under I/O requested
by writeback.

Signed-off-by: Li Dongyang <dongyangli@....com>
Signed-off-by: Theodore Ts'o <tytso@....edu>
Reviewed-by: Andreas Dilger <adilger@...ger.ca>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 fs/ext4/mmp.c | 1 -
 1 file changed, 1 deletion(-)

--- a/fs/ext4/mmp.c
+++ b/fs/ext4/mmp.c
@@ -48,7 +48,6 @@ static int write_mmp_block(struct super_
 	 */
 	sb_start_write(sb);
 	ext4_mmp_csum_set(sb, mmp);
-	mark_buffer_dirty(bh);
 	lock_buffer(bh);
 	bh->b_end_io = end_buffer_write_sync;
 	get_bh(bh);