[PATCH] nvme: don't call blk_mq_{,un}quiesce_tagset when ctrl->tagset is NULL

[Sagi Grimberg]

On 11/16/22 09:27, Christoph Hellwig wrote:
> The NVMe drivers support a mode where no tagset is allocated for the I/O
> queues and only the admin queue is usable.  In that case ctrl->tagset is
> NULL and we must not call the block per-tagset quiesce helpers that
> dereference it.
> 
> Fixes: 98d81f0df70c ("nvme: use blk_mq_[un]quiesce_tagset")
> Reported-by: Gerd Bayer <gbayer at linux.ibm.com>
> Signed-off-by: Christoph Hellwig <hch at lst.de>
> ---
> 
> It turns out we have a bunch of other quiesce calls that can happen when
> only the admin queue is live.  So bring back the original quick fix to
> check for the tagset pointer in the quiesce helpers.
> 
>   drivers/nvme/host/core.c | 4 ++++
>   1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
> index 3195ae17df309..fd2e26cb7a688 100644
> --- a/drivers/nvme/host/core.c
> +++ b/drivers/nvme/host/core.c
> @@ -5215,6 +5215,8 @@ EXPORT_SYMBOL_GPL(nvme_start_freeze);
>   
>   void nvme_quiesce_io_queues(struct nvme_ctrl *ctrl)
>   {
> +	if (!ctrl->tagset)
> +		return;

Can this be placed in the pci code instead?

>   	if (!test_and_set_bit(NVME_CTRL_STOPPED, &ctrl->flags))
>   		blk_mq_quiesce_tagset(ctrl->tagset);
>   	else
> @@ -5224,6 +5226,8 @@ EXPORT_SYMBOL_GPL(nvme_quiesce_io_queues);
>   
>   void nvme_unquiesce_io_queues(struct nvme_ctrl *ctrl)
>   {
> +	if (!ctrl->tagset)
> +		return;
>   	if (test_and_clear_bit(NVME_CTRL_STOPPED, &ctrl->flags))
>   		blk_mq_unquiesce_tagset(ctrl->tagset);
>   }