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Date:   Tue, 27 Jun 2023 09:03:07 -0700
From:   Christoph Hellwig <hch@infradead.org>
To:     Qu Wenruo <wqu@suse.com>
Cc:     linux-btrfs@vger.kernel.org
Subject: Re: [PATCH] btrfs: avoid duplicated chunk lookup during
 btrfs_map_block()
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References: <c063726e0bdcf99226ba474f93b56f9fd2f939f3.1687848314.git.wqu@suse.com>
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On Tue, Jun 27, 2023 at 02:45:18PM +0800, Qu Wenruo wrote:
> +	num_copies = map_num_copies(map);
> +
> +	if (mirror_num > num_copies) {

num_copies is only used for this single comparism, so I think we'd be
better off just dropping the variable and writing this as:

	if (mirror_num > map_num_copies(map)) {

> +		free_extent_map(em);
> +		return -EINVAL;

And I'd probably add a free_extent_map label to the end of the
function and jump to that to avoid extra error returns.