* - The last sg element is allowed to have length less than page_size.
* - If sg_nents total byte length exceeds the mr max_num_sge * page_size
* then only max_num_sg entries will be mapped.
+ * - If the MR was allocated with type IB_MR_TYPE_SG_GAPS_REG, non of these
+ * constraints holds and the page_size argument is ignored.
*
* Returns the number of sg elements that were mapped to the memory region.
*