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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, Anand Jain <anand.jain@oracle.com>,
        Johannes Thumshirn <johannes.thumshirn@wdc.com>,
        David Sterba <dsterba@suse.com>
Subject: [PATCH 5.4 22/66] btrfs: log message when rw remount is attempted with unclean tree-log
Date:   Tue, 18 Feb 2020 20:54:49 +0100
Message-Id: <20200218190430.142378570@linuxfoundation.org>
In-Reply-To: <20200218190428.035153861@linuxfoundation.org>
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From: David Sterba <dsterba@suse.com>

commit 10a3a3edc5b89a8cd095bc63495fb1e0f42047d9 upstream.

A remount to a read-write filesystem is not safe when there's tree-log
to be replayed. Files that could be opened until now might be affected
by the changes in the tree-log.

A regular mount is needed to replay the log so the filesystem presents
the consistent view with the pending changes included.

CC: stable@vger.kernel.org # 4.4+
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 fs/btrfs/super.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -1804,6 +1804,8 @@ static int btrfs_remount(struct super_bl
 		}
 
 		if (btrfs_super_log_root(fs_info->super_copy) != 0) {
+			btrfs_warn(fs_info,
+		"mount required to replay tree-log, cannot remount read-write");
 			ret = -EINVAL;
 			goto restore;
 		}