crypto: caam - Handle errors in dma_map_sg_chained

Currently dma_map_sg_chained does not handle errors from the
underlying dma_map_sg calls.  This patch adds rollback in case
of an error by simply calling dma_unmap_sg_chained for the ones
that we've already mapped.

All current callers ignore the return value so this should have
no impact on them.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

drivers/crypto/caam/sg_sw_sec4.h

@@ -100,34 +100,41 @@ static inline int sg_count(struct scatterlist *sg_list, int nbytes,
 	return sg_nents;
 }
 
-static int dma_map_sg_chained(struct device *dev, struct scatterlist *sg,
-			      unsigned int nents, enum dma_data_direction dir,
-			      bool chained)
+static inline void dma_unmap_sg_chained(
+	struct device *dev, struct scatterlist *sg, unsigned int nents,
+	enum dma_data_direction dir, bool chained)
 {
 	if (unlikely(chained)) {
 		int i;
 		for (i = 0; i < nents; i++) {
-			dma_map_sg(dev, sg, 1, dir);
+			dma_unmap_sg(dev, sg, 1, dir);
 			sg = sg_next(sg);
 		}
-	} else {
-		dma_map_sg(dev, sg, nents, dir);
+	} else if (nents) {
+		dma_unmap_sg(dev, sg, nents, dir);
 	}
-	return nents;
 }
 
-static int dma_unmap_sg_chained(struct device *dev, struct scatterlist *sg,
-				unsigned int nents, enum dma_data_direction dir,
-				bool chained)
+static inline int dma_map_sg_chained(
+	struct device *dev, struct scatterlist *sg, unsigned int nents,
+	enum dma_data_direction dir, bool chained)
 {
+	struct scatterlist *first = sg;
+
 	if (unlikely(chained)) {
 		int i;
 		for (i = 0; i < nents; i++) {
-			dma_unmap_sg(dev, sg, 1, dir);
+			if (!dma_map_sg(dev, sg, 1, dir)) {
+				dma_unmap_sg_chained(dev, first, i, dir,
+						     chained);
+				nents = 0;
+				break;
+			}
+
 			sg = sg_next(sg);
 		}
-	} else {
-		dma_unmap_sg(dev, sg, nents, dir);
-	}
+	} else
+		nents = dma_map_sg(dev, sg, nents, dir);
+
 	return nents;
 }