From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f42.google.com (mail-wm0-f42.google.com [74.125.82.42]) by kanga.kvack.org (Postfix) with ESMTP id 537276B0254 for ; Tue, 8 Dec 2015 17:19:42 -0500 (EST) Received: by wmec201 with SMTP id c201so233126609wme.0 for ; Tue, 08 Dec 2015 14:19:42 -0800 (PST) Received: from mail.linuxfoundation.org (mail.linuxfoundation.org. [140.211.169.12]) by mx.google.com with ESMTPS id j62si7823980wmd.65.2015.12.08.14.19.41 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 08 Dec 2015 14:19:41 -0800 (PST) Date: Tue, 8 Dec 2015 14:19:39 -0800 From: Andrew Morton 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> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Qais Yousef Cc: linux-mips@linux-mips.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, ralf@linux-mips.org, mgorman@techsingularity.net 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, 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