linux-kernel - Re: [PATCH v3 1/3] mm/swapfile: unuse_pte can map random data if swap read fails

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Message-ID: <d091a455-bab0-4094-d0dd-7e194c487d30@huawei.com>
Date:   Fri, 13 May 2022 11:14:06 +0800
From:   Miaohe Lin <linmiaohe@...wei.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
CC:     HORIGUCHI NAOYA (堀口 直也) 
        <naoya.horiguchi@....com>,
        "willy@...radead.org" <willy@...radead.org>,
        "vbabka@...e.cz" <vbabka@...e.cz>,
        "dhowells@...hat.com" <dhowells@...hat.com>,
        "neilb@...e.de" <neilb@...e.de>,
        "david@...hat.com" <david@...hat.com>,
        "apopple@...dia.com" <apopple@...dia.com>,
        "surenb@...gle.com" <surenb@...gle.com>,
        "minchan@...nel.org" <minchan@...nel.org>,
        "peterx@...hat.com" <peterx@...hat.com>,
        "sfr@...b.auug.org.au" <sfr@...b.auug.org.au>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 1/3] mm/swapfile: unuse_pte can map random data if swap
 read fails

On 2022/5/13 8:42, Andrew Morton wrote:
> On Tue, 10 May 2022 14:58:05 +0800 Miaohe Lin <linmiaohe@...wei.com> wrote:
> 
>>>> Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>
>>>> Acked-by: David Hildenbrand <david@...hat.com>
>>>
>>> When I reproduced the issue (generated read error with dm-dust), I saw
>>> infinite loop in the while loop in shmem_unuse_inode() (and this happens
>>> even with this patch). I confirmed that shmem_swapin_page() returns -EIO,
>>> but shmem_unuse_swap_entries() does not return the error to the callers,
>>> so the while loop in shmem_unuse_inode() seems not break.
>>>
>>
>> Many thanks for your report! I didn't test the shmem case because I saw -EIO
>> is returned. So I just focus on the normal page case. Sorry about it. :(
>>
>>> So maybe you need more code around shmem_unuse_inode() to handle the error?
>>
>> I will try to reproduce it and come up a fixup patch asap! And if you like, you
>> can kindly solve this issue too. ;)
> 
> Seems that this patch didn't cause the infinite loop, so as far as I
> can tell it is good to be merged up.  But the problem it solves isn't
> urgent and fixing that infinite loop might impact this change so I
> think I'll drop this version.

I will update and resend the corresponding patch series when I fix this infinite loop.

Thanks!

> .
>