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

From: Vlastimil Babka
Date: Fri Aug 14 2015 - 09:26:54 EST

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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