btrfs: change BUG_ON to assertion when checking for delayed_node root

BugLink: https://bugs.launchpad.net/bugs/2084005

[ Upstream commit be73f4448b607e6b7ce41cd8ef2214fdf6e7986f ]

The pointer to root is initialized in btrfs_init_delayed_node(), no need
to check for it again. Change the BUG_ON to assertion.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Koichiro Den <koichiro.den@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

Author: kdave

fs/btrfs/delayed-inode.c

@@ -978,7 +978,7 @@ static void btrfs_release_delayed_inode(struct btrfs_delayed_node *delayed_node)
 
 	if (delayed_node &&
 	    test_bit(BTRFS_DELAYED_NODE_INODE_DIRTY, &delayed_node->flags)) {
-		BUG_ON(!delayed_node->root);
+		ASSERT(delayed_node->root);
 		clear_bit(BTRFS_DELAYED_NODE_INODE_DIRTY, &delayed_node->flags);
 		delayed_node->count--;