linux-kernel - Re: [PATCH v2 2/2] mm, sl[aou]b: guarantee natural alignment for kmalloc(power-of-two)

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Message-ID: <alpine.DEB.2.21.1909242048020.17661@www.lameter.com>
Date:   Tue, 24 Sep 2019 20:52:52 +0000 (UTC)
From:   cl@...ux.com
To:     David Sterba <dsterba@...e.cz>
cc:     Vlastimil Babka <vbabka@...e.cz>,
        Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Ming Lei <ming.lei@...hat.com>,
        Dave Chinner <david@...morbit.com>,
        Matthew Wilcox <willy@...radead.org>,
        "Darrick J . Wong" <darrick.wong@...cle.com>,
        Christoph Hellwig <hch@....de>, linux-xfs@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, linux-block@...r.kernel.org,
        James Bottomley <James.Bottomley@...senPartnership.com>,
        linux-btrfs@...r.kernel.org, Roman Gushchin <guro@...com>,
        Johannes Weiner <hannes@...xchg.org>
Subject: Re: [PATCH v2 2/2] mm, sl[aou]b: guarantee natural alignment for
 kmalloc(power-of-two)

On Mon, 23 Sep 2019, David Sterba wrote:

> As a user of the allocator interface in filesystem, I'd like to see a
> more generic way to address the alignment guarantees so we don't have to
> apply workarounds like 3acd48507dc43eeeb each time we find that we
> missed something. (Where 'missed' might be another sort of weird memory
> corruption hard to trigger.)

The alignment guarantees are clearly documented and objects are misaligned
in debugging kernels.

Looking at 3acd48507dc43eeeb:Looks like no one tested that patch with a
debug kernel or full debugging on until it hit mainline. Not good.

The consequence for the lack of proper testing is to make the production
kernel contain the debug measures?