nvme: do not let the user delete a ctrl before a complete initialization
If a userspace application performes a "delete_controller" command
early during the ctrl initialization, the delete operation
may race against the init code and the kernel will crash.
Fix the crash by checking the NVME_CTRL_STARTED_ONCE bit;
if it's not set it means that the nvme controller is still
in the process of getting initialized and the kernel
will return an -EBUSY error to userspace.
Set the NVME_CTRL_STARTED_ONCE later in the nvme_start_ctrl()
function, after the controller start operation is completed.
Signed-off-by: Maurizio Lombardi <mlombard@redhat.com> Reviewed-by: Sagi Grimberg <sagi@grimberg.me> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Keith Busch <kbusch@kernel.org>