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Message-ID: <351ca47e-e981-4697-8a2d-10c65de93aa6@huawei.com>
Date:   Tue, 10 Oct 2023 19:10:41 +0800
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Subject: Re: [PATCH -next 1/7] mm_types: add _last_cpupid into folio
To:     "Huang, Ying" <ying.huang@intel.com>
CC:     Andrew Morton <akpm@linux-foundation.org>, <willy@infradead.org>,
        <linux-mm@kvack.org>, <linux-kernel@vger.kernel.org>,
        <david@redhat.com>, Zi Yan <ziy@nvidia.com>
References: <20231010064544.4162286-1-wangkefeng.wang@huawei.com>
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 <87il7ehoxh.fsf@yhuang6-desk2.ccr.corp.intel.com>
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From:   Kefeng Wang <wangkefeng.wang@huawei.com>
In-Reply-To: <87il7ehoxh.fsf@yhuang6-desk2.ccr.corp.intel.com>
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On 2023/10/10 16:17, Huang, Ying wrote:
> Kefeng Wang <wangkefeng.wang@huawei.com> writes:
> 
>> At present, only arc/sparc/m68k define WANT_PAGE_VIRTUAL, both of
>> them don't support numa balancing, and the page struct is aligned
>> to _struct_page_alignment, it is safe to move _last_cpupid before
>> 'virtual' in page, meanwhile, add it into folio, which make us to
>> use folio->_last_cpupid directly.
> 
> Add BUILD_BUG_ON() to check this automatically?

The WANT_PAGE_VIRTUAL and LAST_CPUPID_NOT_IN_PAGE_FLAGS are not
conflict, the check is to make sure that the re-order the virtual
and _last_cpupid is minimal impact, and there is a build warning in
mm/memory.c when the LAST_CPUPID_NOT_IN_PAGE_FLAGS is enabled, so I
don't think we need a new BUILD_BUG_ON here.

Thanks.

> 
> --
> Best Regards,
> Huang, Ying