linux-kernel - Re: [4.7.0rc6] Page Allocation Failures with dm-crypt

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Message-ID: <20160711131818.GA28102@redhat.com>
Date:	Mon, 11 Jul 2016 09:18:19 -0400
From:	Mike Snitzer <snitzer@...hat.com>
To:	Matthias Dahl <ml_linux-kernel@...ary-island.eu>
Cc:	linux-mm@...ck.org, dm-devel@...hat.com,
	linux-kernel@...r.kernel.org
Subject: Re: [4.7.0rc6] Page Allocation Failures with dm-crypt

On Mon, Jul 11 2016 at  4:31am -0400,
Matthias Dahl <ml_linux-kernel@...ary-island.eu> wrote:

> Hello,
> 
> I made a few more tests and here my observations:
> 
> - kernels 4.4.8 and 4.5.5 show the same behavior
> 
> - the moment dd starts, memory usage spikes rapidly and within a just
>   a few seconds has filled up all 32 GiB of RAM
> 
> - dd w/ direct i/o works just fine
> 
> - mkfs.ext4 unfortunately shows the same behavior as dd w/o direct i/o
>   and such makes creation of an ext4 fs on dm-crypt a game of luck
> 
>   (much more exposed so with e2fsprogs 1.43.1)
> 
> I am kind of puzzled that this bug has seemingly gone so long unnoticed
> since it is rather severe and makes dm-crypt unusable to a certain
> degree
> for fs encryption (or at least the initial creation of the fs). Am I
> missing something here or doing something terribly stupid?

Not clear.  Certainly haven't had any reports of memory leaks with
dm-crypt.  Something must explain the execessive nature of your leak but
it isn't a known issue.

Have you tried running with kmemleak enabled?