linux-kernel - Re: [PATCH] btrfs: turn unpin_extent

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Message-ID: <7f2db85d-5090-8614-adae-d0ee64a26ec6@wdc.com>
Date:   Thu, 20 Jul 2023 07:12:58 +0000
From:   Johannes Thumshirn <Johannes.Thumshirn@....com>
To:     Luís Henriques <lhenriques@...e.de>,
        Chris Mason <clm@...com>, Josef Bacik <josef@...icpanda.com>,
        David Sterba <dsterba@...e.com>
CC:     "linux-btrfs@...r.kernel.org" <linux-btrfs@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] btrfs: turn unpin_extent_cache() into a void function

On 18.07.23 19:39, Luís Henriques wrote:
> The value of the 'ret' variable is never changed in function
> unpin_extent_cache().  And since the only caller of this function doesn't
> check the return value, it can simply be turned into a void function.
> 
> Signed-off-by: Luís Henriques <lhenriques@...e.de>

Hmm but inside unpin_extent_cache() there is this:


	/* [...] */
	em = lookup_extent_mapping(tree, start, len);

	WARN_ON(!em || em->start != start);

	if (!em)
		goto out;
	/* [...] */

out:
	write_unlock(&tree->lock);
	return ret;

}

Wouldn't it be better to either actually handle the error, OR
change the WARN_ON() into an ASSERT()?

Given the fact, that if the lookup fails, we've passed wrong 
parameters somehow, an ASSERT() would be a good way IMHO.

Thoughts?