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References: <20210429122519.15183-1-david@redhat.com>
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From:   David Hildenbrand <david@redhat.com>
Organization: Red Hat
Subject: Re: [PATCH v1 3/7] mm: rename and move page_is_poisoned()
Message-ID: <57ac524c-b49a-99ec-c1e4-ef5027bfb61b@redhat.com>
Date:   Wed, 5 May 2021 15:39:08 +0200
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>> Long story short, this should be good enough for the cases we actually can
>> handle? What am I missing?
> 
> I am not sure I follow. My point is that I fail to see any added value
> of the check as it doesn't prevent the race (it fundamentally cannot as
> the page can be poisoned at any time) but the failure path doesn't
> put_page which is incorrect even for hwpoison pages.

Oh, I think you are right. If we have a page and return NULL we would 
leak a reference.

Actually, we discussed in that thread handling this entirely 
differently, which resulted in a v7 [1]; however Andrew moved forward 
with this (outdated?) patch, maybe that was just a mistake?

Yes, I agree we should revert that patch for now.

Regarding the race comment: AFAIU e.g., [2], it's not really a problem 
with a race, but rather some corner case issue that can happen if we 
fail in memory_failure().


[1] https://lkml.kernel.org/r/20210406104123.451ee3c3@alex-virtual-machine
[2] 
https://lkml.kernel.org/r/20210331015258.GB22060@hori.linux.bs1.fc.nec.co.jp

-- 
Thanks,

David / dhildenb