mlx5: Fix mlx5_ib_map_mr_sg mr length

In case we got an initial sg_offset, we need to
account for it in the mr length.

Cc: stable@vger.kernel.org
Fixes: ff2ba9936591 ("IB/core: Add passing an offset into the SG to
ib_map_mr_sg")
Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
Tested-by: Israel Rukshin <israelr@mellanox.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>

drivers/infiniband/hw/mlx5/mr.c

@@ -1784,7 +1784,7 @@ mlx5_ib_sg_to_klms(struct mlx5_ib_mr *mr,
 		klms[i].va = cpu_to_be64(sg_dma_address(sg) + sg_offset);
 		klms[i].bcount = cpu_to_be32(sg_dma_len(sg) - sg_offset);
 		klms[i].key = cpu_to_be32(lkey);
-		mr->ibmr.length += sg_dma_len(sg);
+		mr->ibmr.length += sg_dma_len(sg) - sg_offset;
 
 		sg_offset = 0;
 	}