From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f45.google.com (mail-wm0-f45.google.com [74.125.82.45]) by kanga.kvack.org (Postfix) with ESMTP id AFD0E6B025D for ; Wed, 9 Dec 2015 06:36:43 -0500 (EST) Received: by wmuu63 with SMTP id u63so218204194wmu.0 for ; Wed, 09 Dec 2015 03:36:43 -0800 (PST) Received: from outbound-smtp01.blacknight.com (outbound-smtp01.blacknight.com. [81.17.249.7]) by mx.google.com with ESMTPS id 202si36896546wmp.104.2015.12.09.03.36.42 for (version=TLS1 cipher=AES128-SHA bits=128/128); Wed, 09 Dec 2015 03:36:42 -0800 (PST) Received: from mail.blacknight.com (pemlinmail04.blacknight.ie [81.17.254.17]) by outbound-smtp01.blacknight.com (Postfix) with ESMTPS id 10A2898C1C for ; Wed, 9 Dec 2015 11:36:41 +0000 (UTC) Date: Wed, 9 Dec 2015 11:36:35 +0000 From: Mel Gorman Subject: Re: [PATCH] MIPS: Fix DMA contiguous allocation Message-ID: <20151209113635.GA15910@techsingularity.net> References: <1449569930-2118-1-git-send-email-qais.yousef@imgtec.com> <20151208141939.d0edbb72b3c15844c5ac25ea@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <20151208141939.d0edbb72b3c15844c5ac25ea@linux-foundation.org> Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: Qais Yousef , linux-mips@linux-mips.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, ralf@linux-mips.org On Tue, Dec 08, 2015 at 02:19:39PM -0800, Andrew Morton wrote: > 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? Yes, this is the correct way it should be checked. The full flags cover watermark and kswapd treatment which potentially could be altered by the caller. -- Mel Gorman SUSE Labs -- 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