On Wed, Nov 23, 2022 at 11:28:19AM +0530, Nitesh Shetty wrote: > Introduce blkdev_issue_copy which supports source and destination bdevs, > and an array of (source, destination and copy length) tuples. > Introduce REQ_COPY copy offload operation flag. Create a read-write > bio pair with a token as payload and submitted to the device in order. > Read request populates token with source specific information which > is then passed with write request. > This design is courtesy Mikulas Patocka's token based copy I thought this patchset is just for enabling copy command which is supported by hardware. But turns out it isn't, because blk_copy_offload() still submits read/write bios for doing the copy. I am just wondering why not let copy_file_range() cover this kind of copy, and the framework has been there. When I was researching pipe/splice code for supporting ublk zero copy[1], I have got idea for async copy_file_range(), such as: io uring based direct splice, user backed intermediate buffer, still zero copy, if these ideas are finally implemented, we could get super-fast generic offload copy, and bdev copy is really covered too. [1] https://lore.kernel.org/linux-block/20221103085004.1029763-1-ming.lei@xxxxxxxxxx/ thanks, Ming
