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Date:   Fri, 17 Nov 2023 19:36:57 +0000
From:   Matthew Wilcox <willy@infradead.org>
To:     Barry Song <21cnbao@gmail.com>
Cc:     David Hildenbrand <david@redhat.com>, steven.price@arm.com,
        akpm@linux-foundation.org, ryan.roberts@arm.com,
        catalin.marinas@arm.com, will@kernel.org,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org, mhocko@suse.com,
        shy828301@gmail.com, v-songbaohua@oppo.com,
        wangkefeng.wang@huawei.com, xiang@kernel.org, ying.huang@intel.com,
        yuzhao@google.com
Subject: Re: [RFC V3 PATCH] arm64: mm: swap: save and restore mte tags for
 large folios
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On Fri, Nov 17, 2023 at 07:47:00AM +0800, Barry Song wrote:
> This has been discussed. Steven, Ryan and I all don't think this is a good
> option. in case we have a large folio with 16 basepages, as do_swap_page
> can only map one base page for each page fault, that means we have
> to restore 16(tags we restore in each page fault) * 16(the times of page faults)
> for this large folio.

That doesn't seem all that hard to fix?  Call set_ptes() instead of
set_pte_at().  The biggest thing, I guess, is making sure that all
the PTEs you're going to set up are still pte_none().