btrfs_find_delayed_ref_head
head = btrfs_find_delayed_ref_head(ctx->fs_info, delayed_refs,
btrfs_find_delayed_ref_head(const struct btrfs_fs_info *fs_info,
head = btrfs_find_delayed_ref_head(fs_info, delayed_refs, bytenr);
head = btrfs_find_delayed_ref_head(root->fs_info, delayed_refs, bytenr);
head = btrfs_find_delayed_ref_head(fs_info, delayed_refs, bytenr);
head = btrfs_find_delayed_ref_head(root->fs_info, delayed_refs, bytenr);