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Date:   Wed, 11 May 2022 21:47:13 -0700
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Subject: Re: [PATCH v4] mm: fix is_pinnable_page against on cma page
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To:     Minchan Kim <minchan@kernel.org>
Cc:     "Paul E. McKenney" <paulmck@kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        linux-mm <linux-mm@kvack.org>,
        LKML <linux-kernel@vger.kernel.org>,
        John Dias <joaodias@google.com>,
        David Hildenbrand <david@redhat.com>
References: <20220511234534.GG1790663@paulmck-ThinkPad-P17-Gen-1>
 <ea64b36c-ecc1-74db-dd2e-909e7e507ef8@nvidia.com>
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 <20220512002207.GJ1790663@paulmck-ThinkPad-P17-Gen-1>
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 <f7ff4186-e629-a5da-3f4d-ec629b0c8dd9@nvidia.com>
 <20220512004949.GK1790663@paulmck-ThinkPad-P17-Gen-1>
 <YnxczoehQJ+x6m9Y@google.com>
 <0accce46-fac6-cdfb-db7f-d08396bf9d35@nvidia.com>
 <aafc0954-80df-dceb-03f2-2caea29cbbda@nvidia.com>
 <YnyCqwY4DxcZ/NjM@google.com>
From:   John Hubbard <jhubbard@nvidia.com>
In-Reply-To: <YnyCqwY4DxcZ/NjM@google.com>
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On 5/11/22 20:44, Minchan Kim wrote:
> Thanks for checking, John.
> 
> I don't want to have the READ_ONCE in __get_pfnblock_flags_mask
> atm even though it's an extra memory dereference for specific
> architecutre and specific compiler unless other callsites *do*
> need it.
> 
> We choose the choice(i.e., having __READ_ONCE in is_pinanble_
> page) for *potential* cases(e.g., aggressive LTO for future)
> and if it's an extra memory dereference atm, it would be multiple
> instructions *potentailly* as having more change or different
> compiler and/or arches now or later. It's out of scope in
> this patch.

Agreed!


thanks,
-- 
John Hubbard
NVIDIA