Commit 87213b0d authored Dec 01, 2025 by Caleb Sander Mateos Committed by Jens Axboe Dec 08, 2025

ublk: allow non-blocking ctrl cmds in IO_URING_F_NONBLOCK issue



Handling most of the ublksrv_ctrl_cmd opcodes require locking a mutex,
so ublk_ctrl_uring_cmd() bails out with EAGAIN when called with the
IO_URING_F_NONBLOCK issue flag. However, several opcodes can be handled
without blocking:
- UBLK_CMD_GET_QUEUE_AFFINITY
- UBLK_CMD_GET_DEV_INFO
- UBLK_CMD_GET_DEV_INFO2
- UBLK_U_CMD_GET_FEATURES

Handle these opcodes synchronously instead of returning EAGAIN so
io_uring doesn't need to issue the command via the worker thread pool.

Signed-off-by: Caleb Sander Mateos <csander@purestorage.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

parent 0f45353d

drivers/block/ublk_drv.c

+15 −1

Original line number	Diff line number	Diff line
		@@ -3673,6 +3673,19 @@ static int ublk_ctrl_uring_cmd_permission(struct ublk_device *ub,
		return ret;
		}

		static bool ublk_ctrl_uring_cmd_may_sleep(u32 cmd_op)
		{
		switch (_IOC_NR(cmd_op)) {
		case UBLK_CMD_GET_QUEUE_AFFINITY:
		case UBLK_CMD_GET_DEV_INFO:
		case UBLK_CMD_GET_DEV_INFO2:
		case _IOC_NR(UBLK_U_CMD_GET_FEATURES):
		return false;
		default:
		return true;
		}
		}

		static int ublk_ctrl_uring_cmd(struct io_uring_cmd *cmd,
		unsigned int issue_flags)
		{
		@@ -3681,7 +3694,8 @@ static int ublk_ctrl_uring_cmd(struct io_uring_cmd *cmd,
		u32 cmd_op = cmd->cmd_op;
		int ret = -EINVAL;

		if (issue_flags & IO_URING_F_NONBLOCK)
		if (ublk_ctrl_uring_cmd_may_sleep(cmd_op) &&
		issue_flags & IO_URING_F_NONBLOCK)
		return -EAGAIN;

		ublk_ctrl_cmd_dump(cmd);