linux-kernel - Re: [PATCH v2] mm/swapfile: unuse_pte can map random data if swap read fails

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Message-ID: <a6707adc-6d3e-92bb-4bb3-29a6e1f350f1@huawei.com>
Date:   Tue, 19 Apr 2022 20:00:32 +0800
From:   Miaohe Lin <linmiaohe@...wei.com>
To:     David Hildenbrand <david@...hat.com>, <akpm@...ux-foundation.org>
CC:     <willy@...radead.org>, <vbabka@...e.cz>, <dhowells@...hat.com>,
        <neilb@...e.de>, <apopple@...dia.com>, <surenb@...gle.com>,
        <minchan@...nel.org>, <peterx@...hat.com>, <sfr@...b.auug.org.au>,
        <rcampbell@...dia.com>, <naoya.horiguchi@....com>,
        <linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] mm/swapfile: unuse_pte can map random data if swap
 read fails

On 2022/4/19 19:46, David Hildenbrand wrote:
...
>> Do you mean that we should set the pfn to 0 for the hwpoison marker so that we can
>> distinguish swapin error case from real hwpoison case?
> 
> I am not sure if we really have to distinguish. However, "0" seems to
> make sense to indicate "this is not an actual problematic PFN, the
> information is simply no longer around due to a hardware issue.
> 

IMHO, we have to distinguish. For example, we might need to return VM_FAULT_SIGBUS
instead of VM_FAULT_HWPOISON when user accesses the error page. Or should we simply
return VM_FAULT_HWPOISON to simplify the handling?

Thanks!