From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx103.postini.com [74.125.245.103]) by kanga.kvack.org (Postfix) with SMTP id 190866B0044 for ; Thu, 23 Aug 2012 02:17:32 -0400 (EDT) Date: Thu, 23 Aug 2012 09:15:19 +0300 From: Hiroshi Doyu Subject: Re: [RFC 2/4] ARM: dma-mapping: IOMMU allocates pages from pool with GFP_ATOMIC Message-ID: <20120823091519.804aeae4ba93bcfe011e787c@nvidia.com> In-Reply-To: <012401cd80f4$59727020$0c575060$%szyprowski@samsung.com> References: <1345630830-9586-1-git-send-email-hdoyu@nvidia.com> <1345630830-9586-3-git-send-email-hdoyu@nvidia.com> <20120822.163648.3800987367886904.hdoyu@nvidia.com> <012401cd80f4$59727020$0c575060$%szyprowski@samsung.com> MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Marek Szyprowski Cc: "pullip.cho@samsung.com" , "linux-arm-kernel@lists.infradead.org" , "linaro-mm-sig@lists.linaro.org" , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , "kyungmin.park@samsung.com" , "arnd@arndb.de" , "linux@arm.linux.org.uk" , "chunsang.jeong@linaro.org" , Krishna Reddy , "konrad.wilk@oracle.com" , "subashrp@gmail.com" , "minchan@kernel.org" Hi, On Thu, 23 Aug 2012 07:58:34 +0200 Marek Szyprowski wrote: > Hello, > > On Wednesday, August 22, 2012 3:37 PM Hiroshi Doyu wrote: > > > KyongHo Cho wrote @ Wed, 22 Aug 2012 14:47:00 +0200: > > > > > vzalloc() call in __iommu_alloc_buffer() also causes BUG() in atomic context. > > > > Right. > > > > I've been thinking that kzalloc() may be enough here, since > > vzalloc() was introduced to avoid allocation failure for big chunk of > > memory, but I think that it's unlikely that the number of page array > > can be so big. So I propose to drop vzalloc() here, and just simply to > > use kzalloc only as below(*1). > > We already had a discussion about this, so I don't think it makes much sense to > change it back to kzalloc. This vmalloc() call won't hurt anyone. It should not > be considered a problem for atomic allocations, because no sane driver will try > to allocate buffers larger than a dozen KiB with GFP_ATOMIC flag. I would call > such try a serious bug, which we should not care here. Ok, I've already sent v2 just now, where, instead of changing it back, just with GFP_ATOMIC, kzalloc() would be selected, just in case. I guess that this would be ok(a bit safer?) -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org