From: Marek Szyprowski <m.szyprowski@samsung.com>
To: "'Hiroshi Doyu'" <hdoyu@nvidia.com>, pullip.cho@samsung.com
Cc: linux-arm-kernel@lists.infradead.org, linaro-mm-sig@lists.linaro.org,
        linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        kyungmin.park@samsung.com, arnd@arndb.de, linux@arm.linux.org.uk,
        chunsang.jeong@linaro.org, "'Krishna Reddy'" <vdumpa@nvidia.com>,
        konrad.wilk@oracle.com, subashrp@gmail.com, minchan@kernel.org
References: <1345630830-9586-1-git-send-email-hdoyu@nvidia.com>
 <1345630830-9586-3-git-send-email-hdoyu@nvidia.com>
 <CAHQjnOOF7Ca-Dz8K_zcS=gxQsJvKYaWA3tqUeK1RSd-wLYZ44w@mail.gmail.com>
 <20120822.163648.3800987367886904.hdoyu@nvidia.com>
In-reply-to: <20120822.163648.3800987367886904.hdoyu@nvidia.com>
Subject: RE: [RFC 2/4] ARM: dma-mapping: IOMMU allocates pages from pool with
 GFP_ATOMIC
Date: Thu, 23 Aug 2012 07:58:34 +0200
Organization: SPRC
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Hello,

On Wednesday, August 22, 2012 3:37 PM Hiroshi Doyu wrote:

> KyongHo Cho <pullip.cho@samsung.com> wrote @ Wed, 22 Aug 2012 14:47:00 +0200:
> 
> > vzalloc() call in __iommu_alloc_buffer() also causes BUG() in atomic context.
> 
> Right.
> 
> I've been thinking that kzalloc() may be enough here, since
> vzalloc() was introduced to avoid allocation failure for big chunk of
> memory, but I think that it's unlikely that the number of page array
> can be so big. So I propose to drop vzalloc() here, and just simply to
> use kzalloc only as below(*1).

We already had a discussion about this, so I don't think it makes much sense to
change it back to kzalloc. This vmalloc() call won't hurt anyone. It should not
be considered a problem for atomic allocations, because no sane driver will try
to allocate buffers larger than a dozen KiB with GFP_ATOMIC flag. I would call
such try a serious bug, which we should not care here.

Best regards
-- 
Marek Szyprowski
Samsung Poland R&D Center


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