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From: Joonsoo Kim <js1304@gmail.com>
Date: Wed, 11 Jul 2018 16:35:28 +0900
Message-ID: <CAAmzW4P1m_T77DfQzDD6ysGaOF46++-0gwRaOajmo6ef=VYp=A@mail.gmail.com>
Subject: Re: [PATCH 1/2] mm/cma: remove unsupported gfp_mask parameter from
 cma_alloc()
To: Michal Hocko <mhocko@kernel.org>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>,
 Linux Memory Management List <linux-mm@kvack.org>,
 LKML <linux-kernel@vger.kernel.org>,
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 Andrew Morton <akpm@linux-foundation.org>,
 Michal Nazarewicz <mina86@mina86.com>,
 Joonsoo Kim <iamjoonsoo.kim@lge.com>, Vlastimil Babka <vbabka@suse.cz>,
 Christoph Hellwig <hch@lst.de>,
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2018-07-10 18:50 GMT+09:00 Michal Hocko <mhocko@kernel.org>:
> On Tue 10-07-18 16:19:32, Joonsoo Kim wrote:
>> Hello, Marek.
>>
>> 2018-07-09 21:19 GMT+09:00 Marek Szyprowski <m.szyprowski@samsung.com>:
>> > cma_alloc() function doesn't really support gfp flags other than
>> > __GFP_NOWARN, so convert gfp_mask parameter to boolean no_warn parameter.
>>
>> Although gfp_mask isn't used in cma_alloc() except no_warn, it can be used
>> in alloc_contig_range(). For example, if passed gfp mask has no __GFP_FS,
>> compaction(isolation) would work differently. Do you have considered
>> such a case?
>
> Does any of cma_alloc users actually care about GFP_NO{FS,IO}?

I don't know. My guess is that cma_alloc() is used for DMA allocation so
block device would use it, too. If fs/block subsystem initiates the
request for the device,
it would be possible that cma_alloc() is called with such a flag.
Again, I don't know
much about those subsystem so I would be wrong.

Thanks.