linux-ext4 - [PATCH] ext4: don't mark mmp buffer head dirty

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Date:   Sun,  9 Sep 2018 16:30:28 +1000
From:   Li Dongyang <dongyangli@....com>
To:     linux-ext4@...r.kernel.org
Cc:     adilger@...ger.ca
Subject: [PATCH] ext4: don't mark mmp buffer head dirty

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>
Cc: Andreas Dilger <adilger@...ger.ca>
---
 fs/ext4/mmp.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/fs/ext4/mmp.c b/fs/ext4/mmp.c
index 39b07c2d3384..2305b4374fd3 100644
--- a/fs/ext4/mmp.c
+++ b/fs/ext4/mmp.c
@@ -49,7 +49,6 @@ static int write_mmp_block(struct super_block *sb, struct buffer_head *bh)
 	 */
 	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);
-- 
2.18.0