linux-kernel - [PATCH v2 21/21] dma-mapping: Disallow .map_sg operations from returning zero on error

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Message-Id: <20210723175008.22410-22-logang@deltatee.com>
Date:   Fri, 23 Jul 2021 11:50:08 -0600
From:   Logan Gunthorpe <logang@...tatee.com>
To:     linux-kernel@...r.kernel.org, linux-alpha@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-ia64@...r.kernel.org,
        linux-mips@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        linux-s390@...r.kernel.org, sparclinux@...r.kernel.org,
        iommu@...ts.linux-foundation.org, linux-parisc@...r.kernel.org,
        xen-devel@...ts.xenproject.org
Cc:     Christoph Hellwig <hch@....de>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Robin Murphy <robin.murphy@....com>,
        Stephen Bates <sbates@...thlin.com>,
        Martin Oliveira <martin.oliveira@...eticom.com>,
        Logan Gunthorpe <logang@...tatee.com>
Subject: [PATCH v2 21/21] dma-mapping: Disallow .map_sg operations from returning zero on error

Now that all the .map_sg operations have been converted to returning
proper error codes, drop the code to handle a zero return value,
add a warning if a zero is returned and update the comment for the
map_sg operation.

Signed-off-by: Logan Gunthorpe <logang@...tatee.com>
---
 kernel/dma/mapping.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/kernel/dma/mapping.c b/kernel/dma/mapping.c
index b8dc8b1cb402..86a8a421344a 100644
--- a/kernel/dma/mapping.c
+++ b/kernel/dma/mapping.c
@@ -194,6 +194,9 @@ static int __dma_map_sg_attrs(struct device *dev, struct scatterlist *sg,
 	else
 		ents = ops->map_sg(dev, sg, nents, dir, attrs);
 
+	if (WARN_ON_ONCE(ents == 0))
+		return -EIO;
+
 	if (ents > 0)
 		debug_dma_map_sg(dev, sg, nents, ents, dir);
 
@@ -259,9 +262,7 @@ int dma_map_sgtable(struct device *dev, struct sg_table *sgt,
 	int nents;
 
 	nents = __dma_map_sg_attrs(dev, sgt->sgl, sgt->orig_nents, dir, attrs);
-	if (nents == 0)
-		return -EIO;
-	else if (nents < 0) {
+	if (nents < 0) {
 		if (WARN_ON_ONCE(nents != -EINVAL && nents != -ENOMEM &&
 				 nents != -EIO))
 			return -EIO;
-- 
2.20.1