linux-kernel - Re: mmotm 2015-01-22-15-04: qemu failure due to 'mm: memcontrol: remove unnecessary soft limit tree node test'

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Date:	Fri, 23 Jan 2015 09:17:44 -0600 (CST)
From:	Christoph Lameter <cl@...ux.com>
To:	Johannes Weiner <hannes@...xchg.org>
cc:	Guenter Roeck <linux@...ck-us.net>, akpm@...ux-foundation.org,
	mm-commits@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org, linux-fsdevel@...r.kernel.org,
	linux-next@...r.kernel.org,
	Stephen Rothwell <sfr@...b.auug.org.au>, mhocko@...e.cz
Subject: Re: mmotm 2015-01-22-15-04: qemu failure due to 'mm: memcontrol:
 remove unnecessary soft limit tree node test'

On Fri, 23 Jan 2015, Johannes Weiner wrote:

> Is the assumption of this patch wrong?  Does the specified node have
> to be online for the fallback to work?

Nodes that are offline have no control structures allocated and thus
allocations will likely segfault when the address of the controls
structure for the node is accessed.

If we wanted to prevent that then every allocation would have to add a
check to see if the nodes are online which would impact performance.


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