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Date: Tue, 27 Mar 2018 17:24:10 +0200 (CEST)
From: Sebastian Ott <sebott@linux.vnet.ibm.com>
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To: Christoph Hellwig <hch@lst.de>
cc: Jesper Nilsson <jesper.nilsson@axis.com>,
        Geert Uytterhoeven <geert@linux-m68k.org>,
        linux-kernel@vger.kernel.org
Subject: Re: dma_zalloc_coherent broken with
 57bf5a8963f80fb3828c46c3e3a5b2dd790e09a7
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On Tue, 27 Mar 2018, Christoph Hellwig wrote:

> On Tue, Mar 27, 2018 at 10:12:54AM +0200, Sebastian Ott wrote:
> > Hi,
> > 
> > commit 57bf5a8963f80fb3828c46c3e3a5b2dd790e09a7 broke usage of dma
> > allocations specifying __GFP_ZERO by silently removing that flag.
> > 
> > Why should "the memory returned [] always be zeroed."?
> 
> Because that is what the current implementations do - we always zero
> the memory returned from dma_map_ops.alloc().

What do you mean by current implementations? Arch specific code? At least
on s390 we don't do that. dma-mapping.h doesn't do it either.

Sebastian