Hi, This series takes a dig at expanding io_uring passthrough to have fixed-buffer support. For the NVMe side plumbing, it uses the per-namespace char-device as the backend. The work is on top of Jens' branch (which is 5.14-rc1 based): https://git.kernel.dk/cgit/linux-block/log/?h=io_uring-fops.v5 Testing is done by integrating user-space side with fio: https://github.com/joshkan/fio/commit/a8f40d4f7013ccd38fc51275d8b00fb4ce2404f5 Patches can be grouped into two parts - First part (patch 1 and 2) involves extending 'io_uring cmd' infra (for ioctl updates in task-context), and wire up nvme-passthrough on char-device (/dev/ngXnY). The second part (patch 4, 5, 6) introduces fixed-buffer variant of uring-cmd (IORING_OP_URING_CMD_FIXED), and new NVMe passthrough IOCTLs that operate on pre-registered buffers. The buffers are registered with io_uring in the usual fashion. And the buffer index is passed in command-SQE. This to be used along with two new fixed-buffer ioctl opcodes: NVME_IOCTL_IO_CMD_FIXED or NVME_IOCTL_IO64_CMD_FIXED. For existing passthrough ioctl, nvme-driver maps the buffers in I/O path for each command. For the new ioctl, driver supplies buffer-index to io_uring and gets to reuse pre-mapped buffers. If introducing new ioctls in nvme (for fixed-buffer) does not sound great, another option would be to use 'user flags' in the passthrough command. I look forward to the thoughts of the community on this. Jens, Command-SQE didn't have the field for buf_index. I'm torn among few options, but repurposed len for now. Please take a look. I'd appreciate the feedback/comments. Thanks, Changes from v4: https://lore.kernel.org/linux-nvme/20210325170540.59619-1-joshi.k@xxxxxxxxxxx/ 1. Moved to v5 branch of Jens, adapted to task-work changes in io_uring 2. Removed support for block-passthrough (over nvme0n1) for now 3. Added support for char-passthrough (over ng0n1) 4. Added fixed-buffer passthrough in io_uring and nvme plumbing Anuj Gupta (2): io_uring: mark iopoll not supported for uring-cmd io_uring: add support for uring_cmd with fixed-buffer Kanchan Joshi (4): io_uring: add infra for uring_cmd completion in submitter-task. nvme: wire-up support for async-passthru on char-device. io_uring: add helper for fixed-buffer uring-cmd nvme: enable passthrough with fixed-buffer drivers/nvme/host/core.c | 1 + drivers/nvme/host/ioctl.c | 245 +++++++++++++++++++++++++++++--- drivers/nvme/host/multipath.c | 1 + drivers/nvme/host/nvme.h | 5 + fs/io_uring.c | 69 ++++++++- include/linux/io_uring.h | 15 ++ include/uapi/linux/io_uring.h | 6 +- include/uapi/linux/nvme_ioctl.h | 2 + 8 files changed, 319 insertions(+), 25 deletions(-) -- 2.25.1
