Re: [PATCH 2/6] scsi: iscsi: Speed up session unblocking and removal.

[Lee Duncan <lduncan@suse.com>]

On 2/26/22 15:04, Mike Christie wrote:
> When the iscsi class was added upstream blocking a queue was fast because
> it just set some flag bits and didn't handle IO that was in the process
> of being sent to the driver. That's no longer the case so blocking a queue
> is expensive and we can end up with a backlog of blocks by the time we
> have relogged in and are trying to start the queues.
> 
> For the session unblock case, this has try to cancel the block and
> recovery work in case they are still queued so we can avoid unneeded queue
> manipulations. For removal we also now try to cancel all the recovery
> related works since a couple lines down we will set the session and device
> state so running those functions are not necessary.
> 
> Signed-off-by: Mike Christie <michael.christie@oracle.com>
> ---
>   drivers/scsi/scsi_transport_iscsi.c | 9 +++++----
>   1 file changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/scsi/scsi_transport_iscsi.c b/drivers/scsi/scsi_transport_iscsi.c
> index c58126e8cd88..732938f5436b 100644
> --- a/drivers/scsi/scsi_transport_iscsi.c
> +++ b/drivers/scsi/scsi_transport_iscsi.c
> @@ -1944,7 +1944,8 @@ static void __iscsi_unblock_session(struct work_struct *work)
>    */
>   void iscsi_unblock_session(struct iscsi_cls_session *session)
>   {
> -	flush_work(&session->block_work);
> +	if (!cancel_work_sync(&session->block_work))
> +		cancel_delayed_work_sync(&session->recovery_work);
>   
>   	queue_work(iscsi_eh_timer_workq, &session->unblock_work);
>   	/*
> @@ -2177,9 +2178,9 @@ void iscsi_remove_session(struct iscsi_cls_session *session)
>   		list_del(&session->sess_list);
>   	spin_unlock_irqrestore(&sesslock, flags);
>   
> -	flush_work(&session->block_work);
> -	flush_work(&session->unblock_work);
> -	cancel_delayed_work_sync(&session->recovery_work);
> +	if (!cancel_work_sync(&session->block_work))
> +		cancel_delayed_work_sync(&session->recovery_work);
> +	cancel_work_sync(&session->unblock_work);
>   	/*
>   	 * If we are blocked let commands flow again. The lld or iscsi
>   	 * layer should set up the queuecommand to fail commands.

Reviewed-by: Lee Duncan <lduncan@suse.com>