From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753837AbdEQJNA (ORCPT ); Wed, 17 May 2017 05:13:00 -0400 Received: from mail.fireflyinternet.com ([109.228.58.192]:51032 "EHLO fireflyinternet.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751887AbdEQJM6 (ORCPT ); Wed, 17 May 2017 05:12:58 -0400 X-Default-Received-SPF: pass (skip=forwardok (res=PASS)) x-ip-name=78.156.65.138; Date: Wed, 17 May 2017 10:12:41 +0100 From: Chris Wilson To: Michal Hocko Cc: dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Daniel Vetter , Jani Nikula , Sean Paul , David Airlie Subject: Re: [PATCH 1/2] drm: replace drm_[cm]alloc* by kvmalloc alternatives Message-ID: <20170517091241.GL26693@nuc-i3427.alporthouse.com> Mail-Followup-To: Chris Wilson , Michal Hocko , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Daniel Vetter , Jani Nikula , Sean Paul , David Airlie References: <20170517065509.18659-1-mhocko@kernel.org> <20170517073809.GJ26693@nuc-i3427.alporthouse.com> <20170517090350.GG18247@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170517090350.GG18247@dhcp22.suse.cz> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, May 17, 2017 at 11:03:50AM +0200, Michal Hocko wrote: > On Wed 17-05-17 08:38:09, Chris Wilson wrote: > > On Wed, May 17, 2017 at 08:55:08AM +0200, Michal Hocko wrote: > > > From: Michal Hocko > > > > > > drm_[cm]alloc* has grown their own kvmalloc with vmalloc fallback > > > implementations. MM has grown kvmalloc* helpers in the meantime. Let's > > > use those because it a) reduces the code and b) MM has a better idea > > > how to implement fallbacks (e.g. do not vmalloc before kmalloc is tried > > > with __GFP_NORETRY). > > > > > > drm_calloc_large needs to get __GFP_ZERO explicitly but it is the same > > > thing as kvmalloc_array in principle. > > > > > > Signed-off-by: Michal Hocko > > > > Just a little surprised that calloc_large users still exist. > > > > Reviewed-by: Chris Wilson > > Thanks! > > > One more feature request from mm, can we have the > > if (size != 0 && n > SIZE_MAX / size) > > check exported by itself. > > What do you exactly mean by exporting? Just make available to others so that little things like choice between SIZE_MAX and ULONG_MAX are consistent and actually reflect the right limit (as dictated by kmalloc/kvmalloc/vmalloc...). > Something like the following? > I haven't compile tested it outside of mm with different config options. > Sticking alloc_array_check into mm_types.h is kind of gross but I do not > have a great idea where to put it. A new header doesn't seem nice. > --- > diff --git a/include/linux/mm.h b/include/linux/mm.h > index 7cb17c6b97de..f908b14ffc4c 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -534,7 +534,7 @@ static inline void *kvzalloc(size_t size, gfp_t flags) > > static inline void *kvmalloc_array(size_t n, size_t size, gfp_t flags) > { > - if (size != 0 && n > SIZE_MAX / size) > + if (!alloc_array_check(n, size)) > return NULL; > > return kvmalloc(n * size, flags); > diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h > index 45cdb27791a3..d7154b43a0d1 100644 > --- a/include/linux/mm_types.h > +++ b/include/linux/mm_types.h > @@ -601,4 +601,10 @@ typedef struct { > unsigned long val; > } swp_entry_t; > > +static inline bool alloc_array_check(size_t n, size_t size) > +{ > + if (size != 0 && n > SIZE_MAX / size) > + return false; > + return true; Just return size == 0 || n <= SIZE_MAX /size ? Whether or not size being 0 makes for a sane user is another question. The guideline is that size is the known constant from sizeof() or whatever and n is the variable number to allocate. But yes, that inline is what I want :) -Chris -- Chris Wilson, Intel Open Source Technology Centre