ext4: set lazytime on remount if MS_LAZYTIME is set by mount

Newer versions of mount parse the lazytime feature and pass it to the
mount system call via the flags field in the mount system call,
removing the lazytime string from the mount options list.  So we need
to check for the presence of MS_LAZYTIME and set it in sb->s_flags in
order for this flag to be set on a remount.
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@vger.kernel.org

fs/ext4/super.c

@@ -4971,6 +4971,9 @@ static int ext4_remount(struct super_block *sb, int *flags, char *data)
 		set_task_ioprio(sbi->s_journal->j_task, journal_ioprio);
 	}
 
+	if (*flags & MS_LAZYTIME)
+		sb->s_flags |= MS_LAZYTIME;
+
 	if ((*flags & MS_RDONLY) != (sb->s_flags & MS_RDONLY)) {
 		if (sbi->s_mount_flags & EXT4_MF_FS_ABORTED) {
 			err = -EROFS;