From mboxrd@z Thu Jan 1 00:00:00 1970 From: m.szyprowski@samsung.com (Marek Szyprowski) Date: Thu, 23 Aug 2012 09:52:07 +0200 Subject: [RFC 2/4] ARM: dma-mapping: IOMMU allocates pages from pool with GFP_ATOMIC In-Reply-To: <20120823091519.804aeae4ba93bcfe011e787c@nvidia.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> <20120823091519.804aeae4ba93bcfe011e787c@nvidia.com> Message-ID: <014501cd8104$35a8ce40$a0fa6ac0$%szyprowski@samsung.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.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