linux-kernel - Re: [PATCH] mm: make page pfmemalloc check more robust

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Message-ID: <55CDEC95.5050307@suse.cz>
Date:	Fri, 14 Aug 2015 15:26:45 +0200
From:	Vlastimil Babka <vbabka@...e.cz>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	mhocko@...nel.org, linux-mm@...ck.org,
	Mel Gorman <mgorman@...e.de>, Jiri Bohac <jbohac@...e.cz>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"David S. Miller" <davem@...emloft.net>,
	LKML <linux-kernel@...r.kernel.org>, netdev@...r.kernel.org,
	Michal Hocko <mhocko@...e.com>
Subject: Re: [PATCH] mm: make page pfmemalloc check more robust

On 08/13/2015 04:40 PM, Eric Dumazet wrote:
> On Thu, 2015-08-13 at 11:13 +0200, Vlastimil Babka wrote:
>
>> Given that this apparently isn't the first case of this localhost issue,
>> I wonder if network code should just clear skb->pfmemalloc during send
>> (or maybe just send over localhost). That would be probably easier than
>> distinguish the __skb_fill_page_desc() callers for send vs receive.
>
> Would this still needed after this patch ?

Not until another corner case is discovered :) Or something passes a 
genuine pfmemalloc page to a socket (sending contents of some slab 
objects perhaps, where the slab page was allocated as pfmemalloc? Dunno 
if that can happen right now).

> It is sad we do not have a SNMP counter to at least count how often we
> drop skb because pfmemalloc is set.
>
> I'll provide such a patch.
>
>

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