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>

diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c
index 2c715df63f23f4d3735c4130e5707d855ebb576e..3ecaafacfd20388626627d65578b352a64200fe9 100644 (file)
--- a/drivers/block/ublk_drv.c
+++ b/drivers/block/ublk_drv.c
@@ -3673,6 +3673,19 @@ exit:
        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);