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

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Message-ID: <e7af885e08e1ced4f75313bfdfda166d@mail.ud19.udmedia.de>
Date:	Mon, 11 Jul 2016 10:31:22 +0200
From:	Matthias Dahl <ml_linux-kernel@...ary-island.eu>
To:	linux-mm@...ck.org
Cc:	dm-devel@...hat.com, linux-kernel@...r.kernel.org
Subject: Re: [4.7.0rc6] Page Allocation Failures with dm-crypt

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?

With Kind Regards from Germany
Matthias

-- 
Dipl.-Inf. (FH) Matthias Dahl | Software Engineer | binary-island.eu
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