On 5/20/24 03:20, Nitesh Shetty wrote:
We add two new opcode REQ_OP_COPY_DST, REQ_OP_COPY_SRC. Since copy is a composite operation involving src and dst sectors/lba, each needs to be represented by a separate bio to make it compatible with device mapper. We expect caller to take a plug and send bio with destination information, followed by bio with source information. Once the dst bio arrives we form a request and wait for source bio. Upon arrival of source bio we merge these two bio's and send corresponding request down to device driver. Merging non copy offload bio is avoided by checking for copy specific opcodes in merge function.
Plugs are per task. Can the following happen? * Task A calls blk_start_plug() * Task B calls blk_start_plug() * Task A submits a REQ_OP_COPY_DST bio and a REQ_OP_COPY_SRC bio. * Task B submits a REQ_OP_COPY_DST bio and a REQ_OP_COPY_SRC bio. * Task A calls blk_finish_plug() * Task B calls blk_finish_plug() * The REQ_OP_COPY_DST bio from task A and the REQ_OP_COPY_SRC bio from task B are combined into a single request. * The REQ_OP_COPY_DST bio from task B and the REQ_OP_COPY_SRC bio from task A are combined into a single request. Thanks, Bart.
