linux-kernel - Re: [PATCH v2 RFC/RFT] dma-contiguous: Get normal pages for single-page allocations

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Message-ID: <20190325121436.hwmzgqkaggxvnfqx@mbp>
Date:   Mon, 25 Mar 2019 12:14:37 +0000
From:   Catalin Marinas <catalin.marinas@....com>
To:     Nicolin Chen <nicoleotsuka@...il.com>
Cc:     hch@....de, robin.murphy@....com, vdumpa@...dia.com,
        will.deacon@....com, chris@...kel.net, jcmvbkbc@...il.com,
        joro@...tes.org, dwmw2@...radead.org, m.szyprowski@...sung.com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-xtensa@...ux-xtensa.org, iommu@...ts.linux-foundation.org,
        jonathanh@...dia.com
Subject: Re: [PATCH v2 RFC/RFT] dma-contiguous: Get normal pages for
 single-page allocations

On Fri, Mar 22, 2019 at 01:09:26PM -0700, Nicolin Chen wrote:
> On Fri, Mar 22, 2019 at 10:57:13AM +0000, Catalin Marinas wrote:
> > > > Do you have any numbers to back this up? You don't seem to address
> > > > dma_direct_alloc() either but, as I said above, it's not trivial since
> > > > some platforms expect certain physical range for DMA allocations.
> > > 
> > > What's the dma_direct_alloc() here about? Mind elaborating?
> > 
> > I just did a grep for dma_alloc_from_contiguous() in the 5.1-rc1 kernel
> > and came up with __dma_direct_alloc_pages(). Should your patch cover
> > this as well?
> 
> I don't get the meaning of "cover this" here. What missing part
> do you refer to?

What I meant, do you need this hunk as well in your patch?

diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
index fcdb23e8d2fc..8955ba6f52fc 100644
--- a/kernel/dma/direct.c
+++ b/kernel/dma/direct.c
@@ -111,8 +111,7 @@ struct page *__dma_direct_alloc_pages(struct device *dev, size_t size,
 again:
 	/* CMA can be used only in the context which permits sleeping */
 	if (gfpflags_allow_blocking(gfp)) {
-		page = dma_alloc_from_contiguous(dev, count, page_order,
-						 gfp & __GFP_NOWARN);
+		page = dma_alloc_from_contiguous(dev, count, page_order, gfp);
 		if (page && !dma_coherent_ok(dev, page_to_phys(page), size)) {
 			dma_release_from_contiguous(dev, page, count);
 			page = NULL;