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Date: Fri, 26 Jan 2018 23:34:50 -0800
From: Christoph Hellwig <hch@infradead.org>
Subject: Re: [PATCH 5/7] iomap: warn on zero-length mappings
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> -	if (WARN_ON(iomap.offset > pos))
> +	if (WARN_ON(iomap.offset > pos) || WARN_ON(iomap.length == 0))

Btw, shouldn't this be one WARN_ON with both conditions inside?
It's not like we can spot which one it was based on the output
anyway.

Alternatively just have two conditionals, which allows us to spot
what went wrong.