Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751564AbbLHWTl (ORCPT ); Tue, 8 Dec 2015 17:19:41 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:57651 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750815AbbLHWTk (ORCPT ); Tue, 8 Dec 2015 17:19:40 -0500 Date: Tue, 8 Dec 2015 14:19:39 -0800 From: Andrew Morton To: Qais Yousef Cc: , , , , Subject: Re: [PATCH] MIPS: Fix DMA contiguous allocation Message-Id: <20151208141939.d0edbb72b3c15844c5ac25ea@linux-foundation.org> In-Reply-To: <1449569930-2118-1-git-send-email-qais.yousef@imgtec.com> References: <1449569930-2118-1-git-send-email-qais.yousef@imgtec.com> X-Mailer: Sylpheed 3.4.1 (GTK+ 2.24.23; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1623 Lines: 42 On Tue, 8 Dec 2015 10:18:50 +0000 Qais Yousef wrote: > Recent changes to how GFP_ATOMIC is defined seems to have broken the condition > to use mips_alloc_from_contiguous() in mips_dma_alloc_coherent(). > > I couldn't bottom out the exact change but I think it's this one > > d0164adc89f6 (mm, page_alloc: distinguish between being unable to sleep, > unwilling to sleep and avoiding waking kswapd) > > >From what I see GFP_ATOMIC has multiple bits set and the check for !(gfp > & GFP_ATOMIC) isn't enough. To verify if the flag is atomic we need to make > sure that (gfp & GFP_ATOMIC) == GFP_ATOMIC to verify that all bits rquired to > satisfy GFP_ATOMIC condition are set. > > ... > > --- a/arch/mips/mm/dma-default.c > +++ b/arch/mips/mm/dma-default.c > @@ -145,7 +145,7 @@ static void *mips_dma_alloc_coherent(struct device *dev, size_t size, > > gfp = massage_gfp_flags(dev, gfp); > > - if (IS_ENABLED(CONFIG_DMA_CMA) && !(gfp & GFP_ATOMIC)) > + if (IS_ENABLED(CONFIG_DMA_CMA) && ((gfp & GFP_ATOMIC) != GFP_ATOMIC)) > page = dma_alloc_from_contiguous(dev, > count, get_order(size)); > if (!page) hm. It seems that the code is asking "can I do a potentially-sleeping memory allocation"? The way to do that under the new regime is if (IS_ENABLED(CONFIG_DMA_CMA) && gfpflags_allow_blocking(gfp)) Mel, can you please confirm? -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/