linux-kernel - [PATCH 30/67] dma-direct: retry allocations using GFP

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Date:   Fri, 29 Dec 2017 09:18:34 +0100
From:   Christoph Hellwig <hch@....de>
To:     iommu@...ts.linux-foundation.org
Cc:     linux-alpha@...r.kernel.org, linux-snps-arc@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org,
        adi-buildroot-devel@...ts.sourceforge.net,
        linux-c6x-dev@...ux-c6x.org, linux-cris-kernel@...s.com,
        linux-hexagon@...r.kernel.org, linux-ia64@...r.kernel.org,
        linux-m68k@...ts.linux-m68k.org, linux-metag@...r.kernel.org,
        Michal Simek <monstr@...str.eu>, linux-mips@...ux-mips.org,
        linux-parisc@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        patches@...ups.riscv.org, linux-s390@...r.kernel.org,
        linux-sh@...r.kernel.org, sparclinux@...r.kernel.org,
        Guan Xuetao <gxt@...c.pku.edu.cn>, x86@...nel.org,
        linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 30/67] dma-direct: retry allocations using GFP_DMA for small masks

If we got back an allocation that wasn't inside the support coherent mask,
retry the allocation using GFP_DMA.

Based on the x86 code.

Signed-off-by: Christoph Hellwig <hch@....de>
---
 lib/dma-direct.c | 25 ++++++++++++++++++++++++-
 1 file changed, 24 insertions(+), 1 deletion(-)

diff --git a/lib/dma-direct.c b/lib/dma-direct.c
index ab81de3ac1d3..f8467cb3d89a 100644
--- a/lib/dma-direct.c
+++ b/lib/dma-direct.c
@@ -28,6 +28,11 @@ check_addr(struct device *dev, dma_addr_t dma_addr, size_t size,
 	return true;
 }
 
+static bool dma_coherent_ok(struct device *dev, phys_addr_t phys, size_t size)
+{
+	return phys_to_dma(dev, phys) + size <= dev->coherent_dma_mask;
+}
+
 static void *dma_direct_alloc(struct device *dev, size_t size,
 		dma_addr_t *dma_handle, gfp_t gfp, unsigned long attrs)
 {
@@ -35,11 +40,29 @@ static void *dma_direct_alloc(struct device *dev, size_t size,
 	int page_order = get_order(size);
 	struct page *page = NULL;
 
+again:
 	/* CMA can be used only in the context which permits sleeping */
-	if (gfpflags_allow_blocking(gfp))
+	if (gfpflags_allow_blocking(gfp)) {
 		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;
+		}
+	}
 	if (!page)
 		page = alloc_pages_node(dev_to_node(dev), gfp, page_order);
+
+	if (page && !dma_coherent_ok(dev, page_to_phys(page), size)) {
+		__free_pages(page, page_order);
+		page = NULL;
+
+		if (dev->coherent_dma_mask < DMA_BIT_MASK(32) &&
+		    !(gfp & GFP_DMA)) {
+			gfp = (gfp & ~GFP_DMA32) | GFP_DMA;
+			goto again;
+		}
+	}
+
 	if (!page)
 		return NULL;
 
-- 
2.14.2