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From: Daniel Vacek <neelx@redhat.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
	Michal Hocko <mhocko@suse.com>, Vlastimil Babka <vbabka@suse.cz>,
	Mel Gorman <mgorman@techsingularity.net>,
	Pavel Tatashin <pasha.tatashin@oracle.com>,
	Paul Burton <paul.burton@imgtec.com>,
	stable@vger.kernel.org
Subject: Re: [PATCH v3 2/2] mm/page_alloc: fix memmap_init_zone pageblock alignment
Date: Sat, 3 Mar 2018 02:08:27 +0100	[thread overview]
Message-ID: <CACjP9X_tpVVDPUvyc-B2QU=2J5MXbuFsDcG90d7L0KuwEEuR-g@mail.gmail.com> (raw)
In-Reply-To: <20180302164052.5eea1b896e3a7125d1e1f23a@linux-foundation.org>

On Sat, Mar 3, 2018 at 1:40 AM, Andrew Morton <akpm@linux-foundation.org> wrote:
> On Sat,  3 Mar 2018 01:12:26 +0100 Daniel Vacek <neelx@redhat.com> wrote:
>
>> Commit b92df1de5d28 ("mm: page_alloc: skip over regions of invalid pfns
>> where possible") introduced a bug where move_freepages() triggers a
>> VM_BUG_ON() on uninitialized page structure due to pageblock alignment.
>
> b92df1de5d28 was merged a year ago.  Can you suggest why this hasn't
> been reported before now?

Yeah. I was surprised myself I couldn't find a fix to backport to
RHEL. But actually customers started to report this as soon as 7.4
(where b92df1de5d28 was merged in RHEL) was released. I remember
reports from September/October-ish times. It's not easily reproduced
and happens on a handful of machines only. I guess that's why. But
that does not make it less serious, I think.

Though there actually is a report here:
https://bugzilla.kernel.org/show_bug.cgi?id=196443

And there are reports for Fedora from July:
https://bugzilla.redhat.com/show_bug.cgi?id=1473242
and CentOS: https://bugs.centos.org/view.php?id=13964
and we internally track several dozens reports for RHEL bug
https://bugzilla.redhat.com/show_bug.cgi?id=1525121

Enough? ;-)

> This makes me wonder whether a -stable backport is really needed...

For some machines it definitely is. Won't hurt either, IMHO.

--nX

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  reply	other threads:[~2018-03-03  1:08 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-03-01 12:47 [PATCH] " Daniel Vacek
2018-03-01 13:10 ` Michal Hocko
2018-03-01 15:09   ` Daniel Vacek
2018-03-01 15:27     ` Michal Hocko
2018-03-01 16:20       ` Daniel Vacek
2018-03-01 23:21         ` Andrew Morton
2018-03-02 10:54         ` Daniel Vacek
2018-03-02 13:01         ` Michal Hocko
2018-03-02 15:27           ` Daniel Vacek
2018-03-01 17:24       ` Daniel Vacek
2018-03-02 11:01 ` [PATCH v2] " Daniel Vacek
2018-03-03  0:12 ` [PATCH v3 0/2] mm/page_alloc: fix kernel BUG at mm/page_alloc.c:1913! crash in move_freepages() Daniel Vacek
2018-03-03  0:12   ` [PATCH v3 1/2] mm/memblock: hardcode the end_pfn being -1 Daniel Vacek
2018-03-03  0:12   ` [PATCH v3 2/2] mm/page_alloc: fix memmap_init_zone pageblock alignment Daniel Vacek
2018-03-03  0:40     ` Andrew Morton
2018-03-03  1:08       ` Daniel Vacek [this message]
2018-03-12 12:26         ` Sudeep Holla
2018-03-12 14:49           ` Naresh Kamboju
2018-03-12 16:51             ` Daniel Vacek
2018-03-12 17:11               ` Sudeep Holla
2018-03-13  6:34               ` Naresh Kamboju
2018-03-13 22:47                 ` Daniel Vacek

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