diff --git a/fs/ext4/mmp.c b/fs/ext4/mmp.c
index 79d05e464c432594aeed09ad0f8c3a1c3101a592..b7a850b0070b83b69fe68df59b499c56b0b62cf0 100644
--- a/fs/ext4/mmp.c
+++ b/fs/ext4/mmp.c
@@ -150,8 +150,6 @@ static int kmmpd(void *data)
 	mmp_check_interval = max(EXT4_MMP_CHECK_MULT * mmp_update_interval,
 				 EXT4_MMP_MIN_CHECK_INTERVAL);
 	mmp->mmp_check_interval = cpu_to_le16(mmp_check_interval);
-	BUILD_BUG_ON(sizeof(mmp->mmp_bdevname) < BDEVNAME_SIZE);
-	bdevname(bh->b_bdev, mmp->mmp_bdevname);
 
 	memcpy(mmp->mmp_nodename, init_utsname()->nodename,
 	       sizeof(mmp->mmp_nodename));
@@ -372,13 +370,15 @@ int ext4_multi_mount_protect(struct super_block *sb,
 
 	EXT4_SB(sb)->s_mmp_bh = bh;
 
+	BUILD_BUG_ON(sizeof(mmp->mmp_bdevname) < BDEVNAME_SIZE);
+	bdevname(bh->b_bdev, mmp->mmp_bdevname);
+
 	/*
 	 * Start a kernel thread to update the MMP block periodically.
 	 */
 	EXT4_SB(sb)->s_mmp_tsk = kthread_run(kmmpd, sb, "kmmpd-%.*s",
 					     (int)sizeof(mmp->mmp_bdevname),
-					     bdevname(bh->b_bdev,
-						      mmp->mmp_bdevname));
+					     mmp->mmp_bdevname);
 	if (IS_ERR(EXT4_SB(sb)->s_mmp_tsk)) {
 		EXT4_SB(sb)->s_mmp_tsk = NULL;
 		ext4_warning(sb, "Unable to create kmmpd thread for %s.",