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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Theodore Tso <tytso@mit.edu>,
        Andreas Dilger <adilger@dilger.ca>,
        Sasha Levin <alexander.levin@microsoft.com>
Subject: [PATCH 4.14 007/165] ext4: clear mmp sequence number when remounting read-only
Date:   Mon,  3 Sep 2018 18:54:53 +0200
Message-Id: <20180903165655.374039052@linuxfoundation.org>
In-Reply-To: <20180903165655.003605184@linuxfoundation.org>
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4.14-stable review patch.  If anyone has any objections, please let me know.

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

From: Theodore Ts'o <tytso@mit.edu>

[ Upstream commit 2dca60d98e241bea686004168f85208f215fc697 ]

Previously, when an MMP-protected file system is remounted read-only,
the kmmpd thread would exit the next time it woke up (a few seconds
later), without resetting the MMP sequence number back to
EXT4_MMP_SEQ_CLEAN.

Fix this by explicitly killing the MMP thread when the file system is
remounted read-only.

Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: Andreas Dilger <adilger@dilger.ca>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 fs/ext4/mmp.c   |    7 ++-----
 fs/ext4/super.c |    2 ++
 2 files changed, 4 insertions(+), 5 deletions(-)

--- a/fs/ext4/mmp.c
+++ b/fs/ext4/mmp.c
@@ -186,11 +186,8 @@ static int kmmpd(void *data)
 			goto exit_thread;
 		}
 
-		if (sb_rdonly(sb)) {
-			ext4_warning(sb, "kmmpd being stopped since filesystem "
-				     "has been remounted as readonly.");
-			goto exit_thread;
-		}
+		if (sb_rdonly(sb))
+			break;
 
 		diff = jiffies - last_update_time;
 		if (diff < mmp_update_interval * HZ)
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -5163,6 +5163,8 @@ static int ext4_remount(struct super_blo
 
 			if (sbi->s_journal)
 				ext4_mark_recovery_complete(sb, es);
+			if (sbi->s_mmp_tsk)
+				kthread_stop(sbi->s_mmp_tsk);
 		} else {
 			/* Make sure we can mount this feature set readwrite */
 			if (ext4_has_feature_readonly(sb) ||