From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751180AbdFBHk6 (ORCPT ); Fri, 2 Jun 2017 03:40:58 -0400 Received: from omzsmtpe02.verizonbusiness.com ([199.249.25.209]:37035 "EHLO omzsmtpe02.verizonbusiness.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750826AbdFBHk4 (ORCPT ); Fri, 2 Jun 2017 03:40:56 -0400 X-IronPort-Anti-Spam-Filtered: false From: "Levin, Alexander (Sasha Levin)" X-IronPort-AV: E=Sophos;i="5.39,284,1493683200"; d="scan'208";a="213457208" To: Michal Hocko CC: Andrew Morton , "linux-mm@kvack.org" , LKML , John Hubbard , Andreas Dilger , Vlastimil Babka Subject: Re: [PATCH 1/9] mm: introduce kv[mz]alloc helpers Thread-Topic: [PATCH 1/9] mm: introduce kv[mz]alloc helpers Thread-Index: AQHS23N3wwUShPXV2Eeff8C7p3C+JQ== Date: Fri, 2 Jun 2017 07:40:12 +0000 Message-ID: <20170602074008.wctxj5il3rqnnpbf@sasha-lappy> References: <20170306103032.2540-1-mhocko@kernel.org> <20170306103032.2540-2-mhocko@kernel.org> <20170602071718.zk3ujm64xesoqyrr@sasha-lappy> <20170602072855.GB29840@dhcp22.suse.cz> In-Reply-To: <20170602072855.GB29840@dhcp22.suse.cz> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: user-agent: NeoMutt/20170113 (1.7.2) x-ms-exchange-messagesentrepresentingtype: 1 x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [10.144.60.250] Content-Type: text/plain; charset="us-ascii" Content-ID: <45AC844B5179814AAD5D5FB40FE7AC3F@vzwcorp.com> MIME-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from quoted-printable to 8bit by mail.home.local id v527f1Fm029628 On Fri, Jun 02, 2017 at 09:28:56AM +0200, Michal Hocko wrote: > On Fri 02-06-17 07:17:22, Sasha Levin wrote: > > On Mon, Mar 06, 2017 at 11:30:24AM +0100, Michal Hocko wrote: > > > +void *kvmalloc_node(size_t size, gfp_t flags, int node) > > > +{ > > > + gfp_t kmalloc_flags = flags; > > > + void *ret; > > > + > > > + /* > > > + * vmalloc uses GFP_KERNEL for some internal allocations (e.g page tables) > > > + * so the given set of flags has to be compatible. > > > + */ > > > + WARN_ON_ONCE((flags & GFP_KERNEL) != GFP_KERNEL); > > > > Hm, there are quite a few locations in the kernel that do something like: > > > > __vmalloc(len, GFP_NOFS, PAGE_KERNEL); > > > > According to your patch, vmalloc can't really do GFP_NOFS, right? > > Yes. It is quite likely that they will just work because the hardcoded > GFP_KERNEL inside the vmalloc path is in unlikely paths (page table > allocations for example) but yes they are broken. I didn't convert some > places which opencode the kvmalloc with GFP_NOFS because I strongly > _believe_ that the GFP_NOFS should be revisited, checked whether it is > needed, documented if so and then memalloc_nofs__{save,restore} be used > for the scope which is reclaim recursion unsafe. This would turn all > those vmalloc users to the default GFP_KERNEL and still do the right > thing. While you haven't converted those paths, other folks have picked up on that: commit beeeccca9bebcec386cc31c250cff8a06cf27034 Author: Vinnie Magro Date: Thu May 25 12:18:02 2017 -0700 btrfs: Use kvzalloc instead of kzalloc/vmalloc in alloc_bitmap [...] Maybe we should make kvmalloc_node() fail non-GFP_KERNEL allocations rather than just warn on them to make this error more evident? I'm not sure how these warnings were missed during testing. -- Thanks, Sasha