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Sender: Minchan Kim <minchan.kim@gmail.com>
Date:   Fri, 18 Mar 2022 10:32:07 -0700
From:   Minchan Kim <minchan@kernel.org>
To:     Ivan Babrou <ivan@cloudflare.com>
Cc:     Linux MM <linux-mm@kvack.org>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Nitin Gupta <ngupta@vflare.org>,
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        Jens Axboe <axboe@kernel.dk>, linux-block@vger.kernel.org,
        kernel-team <kernel-team@cloudflare.com>
Subject: Re: zram corruption due to uninitialized do_swap_page fault
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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@cloudflare.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!