[PATCH V2 2/3] nvme-tcp: fix potential unbalanced freeze & unfreeze

[Yi Zhang]

Verified it with the nvme/tcp scenario, Thanks Ming
Tested-by: Yi Zhang <yi.zhang at redhat.com>

On Tue, Jul 11, 2023 at 5:41 PM Ming Lei <ming.lei at redhat.com> wrote:
>
> Move start_freeze into nvme_tcp_configure_io_queues(), and there is
> at least two benefits:
>
> 1) fix unbalanced freeze and unfreeze, since re-connection work may
> fail or be broken by removal
>
> 2) IO during error recovery can be failfast quickly because nvme fabrics
> unquiesces queues after teardown.
>
> One side-effect is that !mpath request may timeout during connecting
> because of queue topo change, but that looks not one big deal:
>
> 1) same problem exists with current code base
>
> 2) compared with !mpath, mpath use case is dominant
>
> Fixes: 2875b0aecabe ("nvme-tcp: fix controller reset hang during traffic")
> Cc: stable at vger.kernel.org
> Signed-off-by: Ming Lei <ming.lei at redhat.com>
> ---
>  drivers/nvme/host/tcp.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/nvme/host/tcp.c b/drivers/nvme/host/tcp.c
> index 3e7dd6f91832..fb24cd8ac46c 100644
> --- a/drivers/nvme/host/tcp.c
> +++ b/drivers/nvme/host/tcp.c
> @@ -1868,6 +1868,7 @@ static int nvme_tcp_configure_io_queues(struct nvme_ctrl *ctrl, bool new)
>                 goto out_cleanup_connect_q;
>
>         if (!new) {
> +               nvme_start_freeze(ctrl);
>                 nvme_unquiesce_io_queues(ctrl);
>                 if (!nvme_wait_freeze_timeout(ctrl, NVME_IO_TIMEOUT)) {
>                         /*
> @@ -1876,6 +1877,7 @@ static int nvme_tcp_configure_io_queues(struct nvme_ctrl *ctrl, bool new)
>                          * to be safe.
>                          */
>                         ret = -ENODEV;
> +                       nvme_unfreeze(ctrl);
>                         goto out_wait_freeze_timed_out;
>                 }
>                 blk_mq_update_nr_hw_queues(ctrl->tagset,
> @@ -1980,7 +1982,6 @@ static void nvme_tcp_teardown_io_queues(struct nvme_ctrl *ctrl,
>         if (ctrl->queue_count <= 1)
>                 return;
>         nvme_quiesce_admin_queue(ctrl);
> -       nvme_start_freeze(ctrl);
>         nvme_quiesce_io_queues(ctrl);
>         nvme_sync_io_queues(ctrl);
>         nvme_tcp_stop_io_queues(ctrl);
> --
> 2.40.1
>


-- 
Best Regards,
  Yi Zhang