btrfs_pinned_by_swapfile
if (btrfs_pinned_by_swapfile(fs_info, src_device)) {
if (btrfs_pinned_by_swapfile(fs_info, bg)) {
if (btrfs_pinned_by_swapfile(fs_info, device)) {
bool btrfs_pinned_by_swapfile(struct btrfs_fs_info *fs_info, void *ptr);