From: Rafael Aquini <aquini@redhat.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Gao Xiang <hsiangkao@redhat.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Carlos Maiolino <cmaiolino@redhat.com>,
Eric Sandeen <esandeen@redhat.com>,
"Huang, Ying" <ying.huang@intel.com>,
stable <stable@vger.kernel.org>
Subject: Re: [PATCH] mm, THP, swap: fix allocating cluster for swapfile by mistake
Date: Wed, 19 Aug 2020 16:44:05 -0400 [thread overview]
Message-ID: <20200819204405.GB2096425@optiplex-lnx> (raw)
In-Reply-To: <20200819130506.eea076dd618644cd7ff875b6@linux-foundation.org>
On Wed, Aug 19, 2020 at 01:05:06PM -0700, Andrew Morton wrote:
> On Thu, 20 Aug 2020 03:56:13 +0800 Gao Xiang <hsiangkao@redhat.com> wrote:
>
> > SWP_FS doesn't mean the device is file-backed swap device,
> > which just means each writeback request should go through fs
> > by DIO. Or it'll just use extents added by .swap_activate(),
> > but it also works as file-backed swap device.
>
> This is very hard to understand :(
>
I'll work with Gao to rephrase that message. Sorry!
> > So in order to achieve the goal of the original patch,
> > SWP_BLKDEV should be used instead.
> >
> > FS corruption can be observed with SSD device + XFS +
> > fragmented swapfile due to CONFIG_THP_SWAP=y.
> >
> > Fixes: f0eea189e8e9 ("mm, THP, swap: Don't allocate huge cluster for file backed swap device")
> > Fixes: 38d8b4e6bdc8 ("mm, THP, swap: delay splitting THP during swap out")
>
> Why do you think it has taken three years to discover this?
>
My bet here is that it's rare to go for a swapfile on non-rotational
devices, and even rarer to create the swapfile when the filesystem is
already fragmented.
RHEL-8, v4.18-based, is starting to see more adpters among Red Hat's
customer base, thus the report now. We are also working on a secondary
issue related to CONFIG_THP_SWAP, as well, where the deferred THP split
registered shriker goes for a NULL pointer dereference in case the
swap device is backed by a rotational drive.
-- Rafael
next prev parent reply other threads:[~2020-08-19 20:44 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-19 19:56 Gao Xiang
2020-08-19 20:05 ` Andrew Morton
2020-08-19 20:15 ` Gao Xiang
2020-08-19 21:41 ` Yang Shi
2020-08-20 1:24 ` Gao Xiang
2020-08-19 20:44 ` Rafael Aquini [this message]
2020-08-19 20:54 ` Gao Xiang
2020-08-20 4:36 ` Huang, Ying
2020-08-20 4:41 ` Gao Xiang
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