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From: Joonsoo Kim <js1304@gmail.com>
Date: Fri, 13 Jul 2018 15:29:29 +0900
Message-ID: <CAAmzW4MNuZOZRP1fHt7E42Mm6+-CLkYYA1Ju2Cfe0ik4Ynb4Lw@mail.gmail.com>
Subject: Re: [PATCH 1/2] mm/cma: remove unsupported gfp_mask parameter from cma_alloc()
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To: Christoph Hellwig <hch@lst.de>
Cc: Michal Hocko <mhocko@kernel.org>, Marek Szyprowski <m.szyprowski@samsung.com>, Linux Memory Management List <linux-mm@kvack.org>, LKML <linux-kernel@vger.kernel.org>, linux-arm-kernel@lists.infradead.org, linuxppc-dev <linuxppc-dev@lists.ozlabs.org>, iommu@lists.linux-foundation.org, Andrew Morton <akpm@linux-foundation.org>, Michal Nazarewicz <mina86@mina86.com>, Joonsoo Kim <iamjoonsoo.kim@lge.com>, Vlastimil Babka <vbabka@suse.cz>, Russell King <linux@armlinux.org.uk>, Catalin Marinas <catalin.marinas@arm.com>, Will Deacon <will.deacon@arm.com>, Paul Mackerras <paulus@ozlabs.org>, Benjamin Herrenschmidt <benh@kernel.crashing.org>, Chris Zankel <chris@zankel.net>, Martin Schwidefsky <schwidefsky@de.ibm.com>, Joerg Roedel <joro@8bytes.org>, Sumit Semwal <sumit.semwal@linaro.org>, Robin Murphy <robin.murphy@arm.com>, Laura Abbott <labbott@redhat.com>, linaro-mm-sig@lists.linaro.org

2018-07-12 16:15 GMT+09:00 Christoph Hellwig <hch@lst.de>:
> On Thu, Jul 12, 2018 at 11:48:47AM +0900, Joonsoo Kim wrote:
>> One of existing user is general DMA layer and it takes gfp flags that is
>> provided by user. I don't check all the DMA allocation sites but how do
>> you convince that none of them try to use anything other
>> than GFP_KERNEL [|__GFP_NOWARN]?
>
> They use a few others things still like __GFP_COMP, __GPF_DMA or
> GFP_HUGEPAGE.  But all these are bogus as we have various implementations
> that can't respect them.  I plan to get rid of the gfp_t argument
> in the dma_map_ops alloc method in a few merge windows because of that,
> but it needs further implementation consolidation first.

Okay. If those flags are all, this change would be okay.

For the remind of this gfp flag introduction in cma_alloc(), see the
following link.

https://marc.info/?l=linux-mm&m=148431452118407

Thanks.