From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx198.postini.com [74.125.245.198]) by kanga.kvack.org (Postfix) with SMTP id 9E7936B005A for ; Thu, 23 Aug 2012 03:52:26 -0400 (EDT) Received: from epcpsbgm2.samsung.com (mailout4.samsung.com [203.254.224.34]) by mailout4.samsung.com (Oracle Communications Messaging Server 7u4-24.01(7.0.4.24.0) 64bit (built Nov 17 2011)) with ESMTP id <0M970060E77CBF00@mailout4.samsung.com> for linux-mm@kvack.org; Thu, 23 Aug 2012 16:52:24 +0900 (KST) Received: from AMDC159 ([106.116.147.30]) by mmp2.samsung.com (Oracle Communications Messaging Server 7u4-24.01 (7.0.4.24.0) 64bit (built Nov 17 2011)) with ESMTPA id <0M9700BKZ76WN630@mmp2.samsung.com> for linux-mm@kvack.org; Thu, 23 Aug 2012 16:52:24 +0900 (KST) From: Marek Szyprowski 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> <20120823091519.804aeae4ba93bcfe011e787c@nvidia.com> In-reply-to: <20120823091519.804aeae4ba93bcfe011e787c@nvidia.com> Subject: RE: [RFC 2/4] ARM: dma-mapping: IOMMU allocates pages from pool with GFP_ATOMIC Date: Thu, 23 Aug 2012 09:52:07 +0200 Message-id: <014501cd8104$35a8ce40$a0fa6ac0$%szyprowski@samsung.com> MIME-version: 1.0 Content-type: text/plain; charset=us-ascii Content-transfer-encoding: 7bit Content-language: pl Sender: owner-linux-mm@kvack.org List-ID: To: 'Hiroshi Doyu' 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 Hiroshi, On Thursday, August 23, 2012 8:15 AM Hiroshi Doyu wrote: > 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?) I've posted some comments to v2. If you agree with my suggestion, no changes around those vmalloc() calls will be needed. Best regards -- Marek Szyprowski Samsung Poland R&D Center -- 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