linux-kernel - [PATCH] dma-mapping: Reduce dma_mapping

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Message-Id: <6a23eacf6603e75e995f8720c24b54c4fc2926f5.1500917215.git.robin.murphy@arm.com>
Date:   Mon, 24 Jul 2017 18:29:27 +0100
From:   Robin Murphy <robin.murphy@....com>
To:     hch@....de, m.szyprowski@...sung.com
Cc:     linux-kernel@...r.kernel.org
Subject: [PATCH] dma-mapping: Reduce dma_mapping_error() inline bloat

Thanks to the nested inlining, all drivers correctly calling
dma_mapping_error() after a mapping a page or single buffer generate two
calls to get_arch_dma_ops() per callsite, which all adds up to a fair
old chunk of useless code, e.g. ~3KB for an arm64 defconfig plus extras:

   text	   data	    bss	    dec	    hex	filename
13051391	1503898	 327768	14883057	 e318f1	vmlinux.o.old
13050751	1503898	 327768	14882417	 e31671	vmlinux.o.new

Give the compiler a hand by making it clear we want the same ops.

Signed-off-by: Robin Murphy <robin.murphy@....com>
---
 include/linux/dma-mapping.h | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
index 843ab866e0f4..239e53d12ee8 100644
--- a/include/linux/dma-mapping.h
+++ b/include/linux/dma-mapping.h
@@ -541,10 +541,11 @@ static inline void dma_free_noncoherent(struct device *dev, size_t size,
 
 static inline int dma_mapping_error(struct device *dev, dma_addr_t dma_addr)
 {
-	debug_dma_mapping_error(dev, dma_addr);
+	const struct dma_map_ops *ops = get_dma_ops(dev);
 
-	if (get_dma_ops(dev)->mapping_error)
-		return get_dma_ops(dev)->mapping_error(dev, dma_addr);
+	debug_dma_mapping_error(dev, dma_addr);
+	if (ops->mapping_error)
+		return ops->mapping_error(dev, dma_addr);
 	return 0;
 }
 
-- 
2.12.2.dirty