linux-kernel - Re: [PATCH] ARM: dma-mapping: always clear allocated buffers

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Date:   Tue, 24 Jul 2018 11:09:06 -0700
From:   Christoph Hellwig <hch@...radead.org>
To:     YueHaibing <yuehaibing@...wei.com>
Cc:     linux@...linux.org.uk, matthias.bgg@...il.com,
        vladimir.murzin@....com, linux-kernel@...r.kernel.org,
        linux-mediatek@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, akpm@...ux-foundation.org,
        iamjoonsoo.kim@....com, robin.murphy@....com, treding@...dia.com,
        zhongjiang@...wei.com
Subject: Re: [PATCH] ARM: dma-mapping: always clear allocated buffers

On Tue, Jul 24, 2018 at 10:04:35PM +0800, YueHaibing wrote:
> Sean Wang report dma_zalloc_coherent doesn't work as expect on his
> armv7,the allocated mem is not zeroed.The reason is __alloc_from_pool
> doesn't honor __GFP_ZERO.

Please explain the "why" a little more.  All the explanations are in
the referenced arm64 commit and should be mentioned here as well.