From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933070AbcLIGSF (ORCPT ); Fri, 9 Dec 2016 01:18:05 -0500 Received: from mail-wj0-f194.google.com ([209.85.210.194]:35264 "EHLO mail-wj0-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752070AbcLIGSE (ORCPT ); Fri, 9 Dec 2016 01:18:04 -0500 Date: Fri, 9 Dec 2016 07:18:00 +0100 From: Michal Hocko To: Dave Chinner Cc: linux-mm@kvack.org, Andrew Morton , Vlastimil Babka , David Rientjes , Mel Gorman , Johannes Weiner , Anatoly Stepanov , LKML , Paolo Bonzini , Mike Snitzer , dm-devel@redhat.com, "Michael S. Tsirkin" , "Theodore Ts'o" , kvm@vger.kernel.org, linux-ext4@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-security-module@vger.kernel.org Subject: Re: [RFC PATCH] mm: introduce kv[mz]alloc helpers Message-ID: <20161209061759.GA12012@dhcp22.suse.cz> References: <20161208103300.23217-1-mhocko@kernel.org> <20161209014417.GN4326@dastard> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20161209014417.GN4326@dastard> User-Agent: Mutt/1.6.0 (2016-04-01) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri 09-12-16 12:44:17, Dave Chinner wrote: > On Thu, Dec 08, 2016 at 11:33:00AM +0100, Michal Hocko wrote: > > From: Michal Hocko > > > > Using kmalloc with the vmalloc fallback for larger allocations is a > > common pattern in the kernel code. Yet we do not have any common helper > > for that and so users have invented their own helpers. Some of them are > > really creative when doing so. Let's just add kv[mz]alloc and make sure > > it is implemented properly. This implementation makes sure to not make > > a large memory pressure for > PAGE_SZE requests (__GFP_NORETRY) and also > > to not warn about allocation failures. This also rules out the OOM > > killer as the vmalloc is a more approapriate fallback than a disruptive > > user visible action. > > > > This patch also changes some existing users and removes helpers which > > are specific for them. In some cases this is not possible (e.g. > > ext4_kvmalloc, libcfs_kvzalloc, __aa_kvmalloc) because those seems to be > > broken and require GFP_NO{FS,IO} context which is not vmalloc compatible > > in general (note that the page table allocation is GFP_KERNEL). Those > > need to be fixed separately. > > See fs/xfs/kmem.c::kmem_zalloc_large(), which is XFS's version of > kvmalloc() that is GFP_NOFS/GFP_NOIO safe. Any generic API for this > functionality will have to play these memalloc_noio_save/ > memalloc_noio_restore games to ensure they are GFP_NOFS safe.... Well, I didn't want to play this games in the generic kvmalloc, at least not now, because all the converted users didn't really need it so far and I believe that the existing users need a) inspection to check whether NO{FS,IO} context is really needed and b) I still believe that the scope nofs api should be used longterm rather than an explicit GFP_NOFS. I am already working on ext[34] code. -- Michal Hocko SUSE Labs