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Date: Wed, 2 Feb 2022 18:28:26 +0000
From: Matthew Wilcox <willy@infradead.org>
To: Muchun Song <songmuchun@bytedance.com>
Cc: dan.j.williams@intel.com, jack@suse.cz, viro@zeniv.linux.org.uk,
	akpm@linux-foundation.org, apopple@nvidia.com, shy828301@gmail.com,
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	nvdimm@lists.linux.dev, linux-kernel@vger.kernel.org,
	linux-mm@kvack.org, duanxiongchun@bytedance.com
Subject: Re: [PATCH v2 3/6] mm: page_vma_mapped: support checking if a pfn is
 mapped into a vma
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References: <20220202143307.96282-1-songmuchun@bytedance.com>
 <20220202143307.96282-4-songmuchun@bytedance.com>
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In-Reply-To: <20220202143307.96282-4-songmuchun@bytedance.com>

On Wed, Feb 02, 2022 at 10:33:04PM +0800, Muchun Song wrote:
> page_vma_mapped_walk() is supposed to check if a page is mapped into a vma.
> However, not all page frames (e.g. PFN_DEV) have a associated struct page
> with it. There is going to be some duplicate codes similar with this function
> if someone want to check if a pfn (without a struct page) is mapped into a
> vma. So add support for checking if a pfn is mapped into a vma. In the next
> patch, the dax will use this new feature.

I'm coming to more or less the same solution for fixing the bug in
page_mapped_in_vma().  If you call it with a head page, it will look
for any page in the THP instead of the precise page.  I think we can do
a fairly significant simplification though, so I'm going to go off
and work on that next ...