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

From: Guenter Roeck
Date: Fri Jan 23 2015 - 12:00:34 EST


On 01/23/2015 08:02 AM, Johannes Weiner wrote:
On Fri, Jan 23, 2015 at 09:17:44AM -0600, Christoph Lameter wrote:
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.

Okay, that makes sense, thank you.

Andrew, can you please drop this patch?

Problem is that there are three patches.

2537ffb mm: memcontrol: consolidate swap controller code
2f9b346 mm: memcontrol: consolidate memory controller initialization
a40d0d2 mm: memcontrol: remove unnecessary soft limit tree node test

Reverting (or dropping) a40d0d2 alone is not possible since it modifies
mem_cgroup_soft_limit_tree_init which is removed by 2f9b346.

Guenter

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