diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h
index e5996984ddd..9aaf5bfdad1 100644
--- a/include/linux/scatterlist.h
+++ b/include/linux/scatterlist.h
@@ -242,6 +242,8 @@ size_t sg_copy_to_buffer(struct scatterlist *sgl, unsigned int nents,
  */
 
 #define SG_MITER_ATOMIC		(1 << 0)	 /* use kmap_atomic */
+#define SG_MITER_TO_SG		(1 << 1)	/* flush back to phys on unmap */
+#define SG_MITER_FROM_SG	(1 << 2)	/* nop */
 
 struct sg_mapping_iter {
 	/* the following three fields can be accessed directly */
diff --git a/lib/scatterlist.c b/lib/scatterlist.c
index a295e404e90..0d475d8167b 100644
--- a/lib/scatterlist.c
+++ b/lib/scatterlist.c
@@ -314,6 +314,7 @@ void sg_miter_start(struct sg_mapping_iter *miter, struct scatterlist *sgl,
 	miter->__sg = sgl;
 	miter->__nents = nents;
 	miter->__offset = 0;
+	WARN_ON(!(flags & (SG_MITER_TO_SG | SG_MITER_FROM_SG)));
 	miter->__flags = flags;
 }
 EXPORT_SYMBOL(sg_miter_start);
@@ -394,6 +395,9 @@ void sg_miter_stop(struct sg_mapping_iter *miter)
 	if (miter->addr) {
 		miter->__offset += miter->consumed;
 
+		if (miter->__flags & SG_MITER_TO_SG)
+			flush_kernel_dcache_page(miter->page);
+
 		if (miter->__flags & SG_MITER_ATOMIC) {
 			WARN_ON(!irqs_disabled());
 			kunmap_atomic(miter->addr, KM_BIO_SRC_IRQ);
@@ -426,8 +430,14 @@ static size_t sg_copy_buffer(struct scatterlist *sgl, unsigned int nents,
 	unsigned int offset = 0;
 	struct sg_mapping_iter miter;
 	unsigned long flags;
+	unsigned int sg_flags = SG_MITER_ATOMIC;
 
-	sg_miter_start(&miter, sgl, nents, SG_MITER_ATOMIC);
+	if (to_buffer)
+		sg_flags |= SG_MITER_FROM_SG;
+	else
+		sg_flags |= SG_MITER_TO_SG;
+
+	sg_miter_start(&miter, sgl, nents, sg_flags);
 
 	local_irq_save(flags);
 
@@ -438,10 +448,8 @@ static size_t sg_copy_buffer(struct scatterlist *sgl, unsigned int nents,
 
 		if (to_buffer)
 			memcpy(buf + offset, miter.addr, len);
-		else {
+		else
 			memcpy(miter.addr, buf + offset, len);
-			flush_kernel_dcache_page(miter.page);
-		}
 
 		offset += len;
 	}