Robert Love wrote:
From: Vasu Dev <vasu.dev@xxxxxxxxx> Adds last_can_queue_ramp_down_time and updates this on every ramp down. If last_can_queue_ramp_down_time is not zero then do ramp up on any IO completion in added fc_fcp_can_queue_ramp_up. Reset last_can_queue_ramp_down_time to zero once can_queue is ramped up to added max_can_queue limit, this is to avoid any more ramp up attempts on subsequent IO completion. The ramp down and up are skipped for FC_CAN_QUEUE_PERIOD to avoid infrequent changes to can_queue, this required keeping track of ramp up time also in last_can_queue_ramp_up_time. Adds code to ramp down can_queue if lp->qfull is set, with added new ramp up code the can_queue will be increased after FC_CAN_QUEUE_PERIOD, therefore it is safe to do ramp down without fsp in this case and will avoid thrash. This required fc_fcp_can_queue_ramp_down locking change so that it can be called with Scsi_Host lock held.
It looks like this could be a more common helper like the sdev ramp up/down code. Software drivers like iscsi_tcp and drivers that do not have hardware cmd limits like ib_iser, srp and cxgb3i could use it. And I think this what lpfc wants in lpfc_queuecommand when lpfc_get_scsi_buf fails instead of doing lpfc_rampdown_queue_depth.
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