linux-kernel - Re: [PATCH v2 6/8] selftests/mm: fix faulting-in code in pagemap

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Message-ID: <cd9e1fca-81ef-4eaa-aea1-aac6dd00623d@kernel.org>
Date: Mon, 19 Jan 2026 12:09:07 +0100
From: "David Hildenbrand (Red Hat)" <david@...nel.org>
To: Kevin Brodsky <kevin.brodsky@....com>, linux-mm@...ck.org,
 linux-kselftest@...r.kernel.org
Cc: linux-kernel@...r.kernel.org, Andrew Morton <akpm@...ux-foundation.org>,
 Lorenzo Stoakes <lorenzo.stoakes@...cle.com>, Mark Brown
 <broonie@...nel.org>, Ryan Roberts <ryan.roberts@....com>,
 Shuah Khan <shuah@...nel.org>, Usama Anjum <Usama.Anjum@....com>
Subject: Re: [PATCH v2 6/8] selftests/mm: fix faulting-in code in
 pagemap_ioctl test

On 1/7/26 17:48, Kevin Brodsky wrote:
> One of the pagemap_ioctl tests attempts to fault in pages by
> memcpy()'ing them to an unused buffer. This probably worked
> originally, but since commit 46036188ea1f ("selftests/mm: build with
> -O2") the compiler is free to optimise away that unused buffer and
> the memcpy() with it. As a result there might not be any resident
> page in the mapping and the test may fail.

Yes, I assume so. Using FORCE_READ() etc is the way to go.


Should we add

Fixes: 46036188ea1f ("selftests/mm: build with -O2")

?

Acked-by: David Hildenbrand (Red Hat) <david@...nel.org>

-- 
Cheers

David