RDMA/core: Add weak ordering dma attr to dma mapping

For memory regions registered with IB_ACCESS_RELAXED_ORDERING will be dma
mapped with the DMA_ATTR_WEAK_ORDERING.

This will allow reads and writes to the mapping to be weakly ordered, such
change can enhance performance on some supporting architectures.

Link: https://lore.kernel.org/r/20200212073559.684139-1-leon@kernel.orgSigned-off-by: Michael Guralnik <michaelgur@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

drivers/infiniband/core/umem.c

@@ -197,6 +197,7 @@ struct ib_umem *ib_umem_get(struct ib_device *device, unsigned long addr,
 	unsigned long lock_limit;
 	unsigned long new_pinned;
 	unsigned long cur_base;
+	unsigned long dma_attr = 0;
 	struct mm_struct *mm;
 	unsigned long npages;
 	int ret;
@@ -278,10 +279,12 @@ struct ib_umem *ib_umem_get(struct ib_device *device, unsigned long addr,
 
 	sg_mark_end(sg);
 
-	umem->nmap = ib_dma_map_sg(device,
-				   umem->sg_head.sgl,
-				   umem->sg_nents,
-				   DMA_BIDIRECTIONAL);
+	if (access & IB_ACCESS_RELAXED_ORDERING)
+		dma_attr |= DMA_ATTR_WEAK_ORDERING;
+
+	umem->nmap =
+		ib_dma_map_sg_attrs(device, umem->sg_head.sgl, umem->sg_nents,
+				    DMA_BIDIRECTIONAL, dma_attr);
 
 	if (!umem->nmap) {
 		ret = -ENOMEM;