linux-kernel - RE: [PATCH] mm, compaction: fix fast_isolate

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Date:   Wed, 9 Nov 2022 05:41:12 +0000
From:   "Akira Naribayashi (Fujitsu)" <a.naribayashi@...itsu.com>
To:     'Mel Gorman' <mgorman@...hsingularity.net>
CC:     "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "vbabka@...e.cz" <vbabka@...e.cz>,
        "rientjes@...gle.com" <rientjes@...gle.com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>,
        "Akira Naribayashi (Fujitsu)" <a.naribayashi@...itsu.com>
Subject: RE: [PATCH] mm, compaction: fix fast_isolate_around() to stay within
 boundaries

On Mon, 7 Nov 2022 15:43:56 +0000, Mei Gorman wrote:
> On Mon, Nov 07, 2022 at 12:32:34PM +0000, Akira Naribayashi (Fujitsu) wrote:
> > > Under what circumstances will this panic occur?  I assume those
> > > circumstnces are pretty rare, give that 6e2b7044c1992 was nearly two
> > > years ago.
> > > 
> > > Did you consider the desirability of backporting this fix into earlier
> > > kernels?
> > 
> > 
> > Panic can occur on systems with multiple zones in a single pageblock.
> > 
> 
> Please provide an example of the panic and the zoneinfo.

This issue is occurring in our customer's environment and cannot 
be shared publicly as it contains customer information.
Also, the panic is occurring with the kernel in RHEL and may not 
panic with Upstream's community kernel.
In other words, it is possible to panic on older kernels.
I think this fix should be backported to stable kernel series.

> > The reason it is rare is that it only happens in special configurations.
> 
> How is this special configuration created?

This is the case when the node boundary is not aligned to pageblock boundary.