Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752819AbcD0Tny (ORCPT ); Wed, 27 Apr 2016 15:43:54 -0400 Received: from mail-wm0-f67.google.com ([74.125.82.67]:32969 "EHLO mail-wm0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752388AbcD0Tnv (ORCPT ); Wed, 27 Apr 2016 15:43:51 -0400 Date: Wed, 27 Apr 2016 21:43:47 +0200 From: Michal Hocko To: Andreas Dilger Cc: Linux MM , linux-fsdevel , Andrew Morton , Dave Chinner , "Theodore Ts'o" , Chris Mason , Jan Kara , ceph-devel@vger.kernel.org, cluster-devel , Linux NFS Mailing List , logfs@logfs.org, XFS Developers , linux-ext4@vger.kernel.org, linux-btrfs@vger.kernel.org, linux-mtd@lists.infradead.org, reiserfs-devel@vger.kernel.org, linux-ntfs-dev@lists.sourceforge.net, linux-f2fs-devel@lists.sourceforge.net, linux-afs@lists.infradead.org, LKML Subject: Re: [PATCH 1.1/2] xfs: abstract PF_FSTRANS to PF_MEMALLOC_NOFS Message-ID: <20160427194347.GA22544@dhcp22.suse.cz> References: <1461671772-1269-2-git-send-email-mhocko@kernel.org> <1461758075-21815-1-git-send-email-mhocko@kernel.org> <04798BA8-2157-4611-B4EA-B8BCBA88AEC3@dilger.ca> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <04798BA8-2157-4611-B4EA-B8BCBA88AEC3@dilger.ca> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1574 Lines: 34 On Wed 27-04-16 11:41:51, Andreas Dilger wrote: > On Apr 27, 2016, at 5:54 AM, Michal Hocko wrote: [...] > > --- a/fs/xfs/kmem.c > > +++ b/fs/xfs/kmem.c > > @@ -80,13 +80,13 @@ kmem_zalloc_large(size_t size, xfs_km_flags_t flags) > > * context via PF_MEMALLOC_NOIO to prevent memory reclaim re-entering > > * the filesystem here and potentially deadlocking. > > */ > > - if ((current->flags & PF_FSTRANS) || (flags & KM_NOFS)) > > + if ((current->flags & PF_MEMALLOC_NOFS) || (flags & KM_NOFS)) > > noio_flag = memalloc_noio_save(); > > > > lflags = kmem_flags_convert(flags); > > ptr = __vmalloc(size, lflags | __GFP_HIGHMEM | __GFP_ZERO, PAGE_KERNEL); > > > > - if ((current->flags & PF_FSTRANS) || (flags & KM_NOFS)) > > + if ((current->flags & PF_MEMALLOC_NOFS) || (flags & KM_NOFS)) > > memalloc_noio_restore(noio_flag); > > Not really the fault of this patch, but it brings this nasty bit of code into > the light. Is all of this machinery still needed given that __vmalloc() can > accept GFP flags? If yes, wouldn't it be better to fix __vmalloc() to honor > the GFP flags instead of working around it in the filesystem code? This is not that easy. __vmalloc can accept gfp flags but it doesn't honor __GFP_IO 100%. IIRC some paths like page table allocations are hardcoded GFP_KERNEL. Besides that I would like to have GFP_NOIO used via memalloc_noio_{save,restore} API as well for the similar reasons as GFP_NOFS - it is just easier to explain scope than particular code paths which might be shared. -- Michal Hocko SUSE Labs