linux-kernel - Re: [PATCH for 3.2.34] memcg: do not trigger OOM from add_to_page_cache

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Message-ID: <20121130153715.GK29317@dhcp22.suse.cz>
Date:	Fri, 30 Nov 2012 16:37:15 +0100
From:	Michal Hocko <mhocko@...e.cz>
To:	azurIt <azurit@...ox.sk>
Cc:	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	cgroups mailinglist <cgroups@...r.kernel.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Johannes Weiner <hannes@...xchg.org>
Subject: Re: [PATCH for 3.2.34] memcg: do not trigger OOM from
 add_to_page_cache_locked

On Fri 30-11-12 16:03:47, Michal Hocko wrote:
[...]
> Anyway, the more interesting thing is gfp_mask is GFP_NOWAIT allocation
> from the page fault? Huh this shouldn't happen - ever.

OK, it starts making sense now. The message came from
pagefault_out_of_memory which doesn't have gfp nor the required node
information any longer. This suggests that VM_FAULT_OOM has been
returned by the fault handler. So this hasn't been triggered by the page
fault allocator.
I am wondering whether this could be caused by the patch but the effect
of that one should be limitted to the write (unlike the later version
for -mm tree which hooks into the shmem as well).

Will have to think about it some more.
-- 
Michal Hocko
SUSE Labs
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