Subject: Re: SOCK_MEMALLOC vs loopback

From: Mel Gorman <[email-masked]>
Date: Thu, 5 Mar 2015 09:50:44 +0000

On Wed, Mar 04, 2015 at 10:03:51PM -0600, Mike Christie wrote:
> On 03/04/2015 02:04 PM, Mel Gorman wrote:
> > other options. If that contract is not met then using it can deadlock the
> > system. It's the same for PF_MEMALLOC -- activating that is a recipe for
> > deadlock due to memory exhaustion.
> 
> For rbd and iscsi's SOCK_MEMALLOC/PF_MEMALLOC use, I copied what you did
> for nbd in commit 7f338fe4540b1d0600b02314c7d885fd358e9eca which always
> sets those flags and seems to rely on the network layer to do the right
> thing. Are they all incorrect?

NBD is a poor example and if it comes to that, I would suggest removing it
and let NBD easily deadlock like it used to. NBD has other failure cases
such as the client can get paged out if -swap is not specified. The same
commit notes that NBD may still deadlock and that min_free_kbytes may have
to be increased.

-- 
Mel Gorman
SUSE Labs