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Date: Tue, 27 Mar 2018 16:33:41 +0200
From: Christoph Hellwig <hch@lst.de>
To: Sebastian Ott <sebott@linux.vnet.ibm.com>
Cc: Christoph Hellwig <hch@lst.de>,
        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
Message-ID: <20180327143341.GA4968@lst.de>
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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().