From mboxrd@z Thu Jan  1 00:00:00 1970
From: Doug Berger <opendmb@gmail.com>
Subject: Re: [PATCH 03/21] mm/hugetlb: correct demote page offset logic
Date: Tue, 13 Sep 2022 18:07:41 -0700
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To: Matthew Wilcox <willy@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>, Jonathan Corbet <corbet@lwn.net>, Rob Herring <robh+dt@kernel.org>, Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>, Frank Rowand <frowand.list@gmail.com>, Mike Kravetz <mike.kravetz@oracle.com>, Muchun Song <songmuchun@bytedance.com>, Mike Rapoport <rppt@kernel.org>, Christoph Hellwig <hch@lst.de>, Marek Szyprowski <m.szyprowski@samsung.com>, Robin Murphy <robin.murphy@arm.com>, Borislav Petkov <bp@suse.de>, "Paul E. McKenney" <paulmck@kernel.org>, Neeraj Upadhyay <quic_neeraju@quicinc.com>, Randy Dunlap <rdunlap@infradead.org>, Damien Le Moal <damien.lemoal@opensource.wdc.com>, Florian Fainelli <f.fainelli@gmail.com>, David Hildenbrand <david@redhat.com>, Zi Yan <ziy@nvidia.com>, Oscar

On 9/13/2022 4:34 PM, Matthew Wilcox wrote:
> On Tue, Sep 13, 2022 at 12:54:50PM -0700, Doug Berger wrote:
>> With gigantic pages it may not be true that struct page structures
>> are contiguous across the entire gigantic page. The mem_map_offset
>> function is used here in place of direct pointer arithmetic to
>> correct for this.
> 
> We're just eliminating mem_map_offset().  Please use nth_page()
> instead.That's good to know. I will include that in v2.

> 
>>   	for (i = 0; i < pages_per_huge_page(h);
>>   				i += pages_per_huge_page(target_hstate)) {
>> +		subpage = mem_map_offset(page, i);
>>   		if (hstate_is_gigantic(target_hstate))