ion: Speed up scatterlist duplication when chaining isn't used

When scatterlist chaining isn't used, the entire allocation is just one
contiguous array that can be quickly copied with memcpy. Do so to speed
up the scatterlist duplication process.

Signed-off-by: Sultan Alsawaf <sultan@kerneltoast.com>
Signed-off-by: Adam W. Willis <return.of.octobot@gmail.com>

drivers/staging/android/ion/ion.c

@@ -1064,10 +1064,15 @@ static struct sg_table *ion_dupe_sg_table(struct sg_table *orig_table)
 		return NULL;
 	}
 
-	sg_orig = orig_table->sgl;
-	for_each_sg(table->sgl, sg, table->nents, i) {
-		*sg = *sg_orig;
-		sg_orig = sg_next(sg_orig);
+	if (table->nents <= SG_MAX_SINGLE_ALLOC) {
+		memcpy(table->sgl, orig_table->sgl,
+		       table->nents * sizeof(*table->sgl));
+	} else {
+		sg_orig = orig_table->sgl;
+		for_each_sg(table->sgl, sg, table->nents, i) {
+			*sg = *sg_orig;
+			sg_orig = sg_next(sg_orig);
+		}
 	}
 	return table;
 }