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Message-ID: <0b734af9-d2c3-acef-3804-3a87e1e61a59@redhat.com>
Date: Thu, 20 Jan 2022 19:19:51 +0100
From: David Hildenbrand <david@...hat.com>
To: Nadav Amit <nadav.amit@...il.com>
Cc: "zhangliang (AG)" <zhangliang5@...wei.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Linux-MM <linux-mm@...ck.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
wangzhigang17@...wei.com, Matthew Wilcox <willy@...radead.org>,
Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH] mm: reuse the unshared swapcache page in do_wp_page
>> Sounds good? At least to me. If only swap/migration entries wouldn't be
>> harder to handle than I'd wish, that's why it's taking a little and will
>> take a little longer.
>
> Thanks for the quick response. I would have to see the logic to set/clear
> PageAnonExclusive to fully understand how things are handled.
>
I'll let you know as soon as I have something. I'll most probably share
a document explaining the design first.
> BTW, I just saw this patch form PeterZ [1] that seems to be related, as
> it deals with changing protection on pinned pages.
Unfortunately the use of page_maybe_dma_pinned() is racy, as we can race
with GUP fast. It's a problem for vmscan which currently relies on it
for correctness. For migration, it might be good enough as we should
fail later when trying to freeze the refcount.
>
>
> [1] https://lore.kernel.org/linux-mm/20220120160822.666778608@infradead.org/
>
--
Thanks,
David / dhildenb
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