[PATCH 2/2] nvme: don't do scan work if io queue count is zero

[Keith Busch]

On Tue, Aug 03, 2021 at 05:06:30PM +0800, Ruozhu Li wrote:
> kernel panic when try to rescan ns when io queue count is zero.Because
> kernel BUG_ON when hctx_idx is greater than ctrl->queue_count.
> --
> nvme_rdma_init_hctx+0x58/0x60 [nvme_rdma]
> blk_mq_realloc_hw_ctxs+0x140/0x4c0
> blk_mq_init_allocated_queue+0x130/0x410
> blk_mq_init_queue+0x40/0x88
> nvme_validate_ns+0xb8/0x740
> nvme_scan_work+0x29c/0x460
> process_one_work+0x1f8/0x490
> worker_thread+0x50/0x4b8
> kthread+0x134/0x138
> ret_from_fork+0x10/0x18
> --
> Defence it by not allowing rescan ns when io queue count is zero.
> 
> Signed-off-by: Ruozhu Li <liruozhu at huawei.com>
> ---
>  drivers/nvme/host/core.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
> index dfd9dec0c1f6..d9f837eb3e26 100644
> --- a/drivers/nvme/host/core.c
> +++ b/drivers/nvme/host/core.c
> @@ -141,7 +141,8 @@ void nvme_queue_scan(struct nvme_ctrl *ctrl)
>  	/*
>  	 * Only new queue scan work when admin and IO queues are both alive
>  	 */
> -	if (ctrl->state == NVME_CTRL_LIVE && ctrl->tagset)
> +	if (ctrl->state == NVME_CTRL_LIVE &&
> +	    ctrl->tagset && ctrl->queue_count > 1)

Why is the transport driver leaving an unusable tagset allocated when
there are no IO queues to support it? I think it should free the tagset
in that case. At least that's what pci does.