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

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Date:   Thu, 24 Mar 2022 19:10:14 -0700
From:   Ivan Babrou <ivan@...udflare.com>
To:     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 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?