Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933896AbdC3N7i (ORCPT ); Thu, 30 Mar 2017 09:59:38 -0400 Received: from mx2.suse.de ([195.135.220.15]:46692 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933527AbdC3N7h (ORCPT ); Thu, 30 Mar 2017 09:59:37 -0400 Date: Thu, 30 Mar 2017 15:59:34 +0200 From: Michal Hocko To: Ilya Dryomov Cc: Greg Kroah-Hartman , "linux-kernel@vger.kernel.org" , stable@vger.kernel.org, Sergey Jerusalimov , Jeff Layton , linux-xfs@vger.kernel.org Subject: Re: [PATCH 4.4 48/76] libceph: force GFP_NOIO for socket allocations Message-ID: <20170330135934.GH1972@dhcp22.suse.cz> References: <20170328133040.GJ18241@dhcp22.suse.cz> <20170329104126.GF27994@dhcp22.suse.cz> <20170329105536.GH27994@dhcp22.suse.cz> <20170329111650.GI27994@dhcp22.suse.cz> <20170330062500.GB1972@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 741 Lines: 20 On Thu 30-03-17 15:53:35, Ilya Dryomov wrote: > On Thu, Mar 30, 2017 at 8:25 AM, Michal Hocko wrote: > > On Wed 29-03-17 16:25:18, Ilya Dryomov wrote: [...] > >> are you saying it's OK for a block > >> device to recurse back into the filesystem when doing I/O, potentially > >> generating more I/O? > > > > No, block device has to make a forward progress guarantee when > > allocating and so use mempools or other means to achieve the same. > > OK, let me put this differently. Do you agree that a block device > cannot make _any_ kind of progress guarantee if it does a GFP_KERNEL > allocation in the I/O path? yes that is correct. And the same is correct for GFP_NOIO allocations as well. -- Michal Hocko SUSE Labs