linux-kernel - Re: zram corruption due to uninitialized do_swap

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Date:   Fri, 25 Mar 2022 09:33:57 +0100
From:   David Hildenbrand <david@...hat.com>
To:     Ivan Babrou <ivan@...udflare.com>, Minchan Kim <minchan@...nel.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Linux MM <linux-mm@...ck.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Nitin Gupta <ngupta@...are.org>,
        Sergey Senozhatsky <senozhatsky@...omium.org>,
        Jens Axboe <axboe@...nel.dk>, linux-block@...r.kernel.org,
        kernel-team <kernel-team@...udflare.com>
Subject: Re: zram corruption due to uninitialized do_swap_page fault

On 25.03.22 03:10, Ivan Babrou wrote:
> On Fri, Mar 18, 2022 at 11:54 AM Minchan Kim <minchan@...nel.org> wrote:
>>
>> On Fri, Mar 18, 2022 at 10:32:07AM -0700, Minchan Kim wrote:
>>> On Fri, Mar 18, 2022 at 09:30:09AM -0700, Ivan Babrou wrote:
>>>> On Wed, Mar 16, 2022 at 11:26 AM Ivan Babrou <ivan@...udflare.com> wrote:
>>>>> I'm making an internal build and will push it to some location to see
>>>>> how it behaves, but it might take a few days to get any sort of
>>>>> confidence in the results (unless it breaks immediately).
>>>>>
>>>>> I've also pushed my patch that disables SWP_SYNCHRONOUS_IO to a few
>>>>> locations yesterday to see how it fares.
>>>>
>>>> I have some updates before the weekend. There are two experimental groups:
>>>>
>>>> * My patch that removes the SWP_SYNCHRONOUS_IO flag. There are 704
>>>> machines in this group across 5 datacenters with cumulative uptime of
>>>> 916 days.
>>>> * Minchan's patch to remove swap_slot_free_notify. There are 376
>>>> machines in this group across 3 datacenters with cumulative uptime of
>>>> 240 days.
>>>>
>>>> Our machines take a couple of hours to start swapping anything after
>>>> boot, and I discounted these two hours from the cumulative uptime.
>>>>
>>>> Neither of these two groups experienced unexpected coredumps or
>>>> rocksdb corruptions.
>>>>
>>>> I think at this point it's reasonable to proceed with Minchan's patch
>>>> (including a backport).
>>>
>>> Let me cook the patch and then will post it.
>>>
>>> Thanks for the testing as well as reporting, Ivan!
>>
>> From 1ede54d46f0b1958bfc624f17fe709637ef8f12a Mon Sep 17 00:00:00 2001
>> From: Minchan Kim <minchan@...nel.org>
>> Date: Tue, 15 Mar 2022 14:14:23 -0700
>> Subject: [PATCH] mm: fix unexpected zeroed page mapping with zram swap
> 
> Is there any action needed from me to make sure that this lands into
> the mm tree and eventually into stable releases?
> 

Sending it as a proper patch with a proper subject, not buried deep down
in a conversation might help ;)

-- 
Thanks,

David / dhildenb