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Date: Tue, 2 Jun 2026 10:11:47 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: Zi Yan <ziy@nvidia.com>
Cc: Kaitao Cheng <kaitao.cheng@linux.dev>, Vlastimil Babka
 <vbabka@kernel.org>, Suren Baghdasaryan <surenb@google.com>, Michal Hocko
 <mhocko@suse.com>, Brendan Jackman <jackmanb@google.com>, Johannes Weiner
 <hannes@cmpxchg.org>, Liu Shixin <liushixin2@huawei.com>, David Hildenbrand
 <david@kernel.org>, Oscar Salvador <osalvador@suse.de>,
 muchun.song@linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org,
 Kaitao Cheng <chengkaitao@kylinos.cn>
Subject: Re: [PATCH v2] mm: page_isolation: avoid unsafe folio reads while
 scanning compound pages
Message-Id: <20260602101147.2892436f68fd383723c39855@linux-foundation.org>
In-Reply-To: <34F0943E-4ACD-4655-B9B8-41F658FCDB7E@nvidia.com>
References: <20260602130755.38794-1-kaitao.cheng@linux.dev>
	<34F0943E-4ACD-4655-B9B8-41F658FCDB7E@nvidia.com>
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On Tue, 02 Jun 2026 11:02:41 -0400 Zi Yan <ziy@nvidia.com> wrote:

> > -		*step = folio_nr_pages(folio) - folio_page_idx(folio, page);
> > +		nr_pages = 1UL << order;
> > +		pfn = page_to_pfn(page);
> > +		*step = (pfn | (nr_pages - 1)) + 1 - pfn;
> >  		return false;
> >  	}
> 
> LGTM. Thanks.
> 
> Just a comment, order can be dropped and use
> nr_pages = compound_nr(&folio->page) instead:
> 1. order > MAX_FOLIO_ORDER -> nr_pages > MAX_FOLIO_NR_PAGES
> 2. PAGE_SIZE << order -> PAGE_SIZE * nr_pages.
> But it is not worth a new version.
> 
> Reviewed-by: Zi Yan <ziy@nvidia.com>

Thanks, I queued this.

What are we to make of Sashiko's question?
https://sashiko.dev/#/patchset/20260602130755.38794-1-kaitao.cheng@linux.dev