On 02/15/2016 12:24 AM, Hannes Reinecke wrote:
The current ALUA device_handler has two drawbacks: - We're sending a 'SET TARGET PORT GROUP' command to every LUN, disregarding the fact that several LUNs might be in a port group and will be automatically switched whenever _any_ LUN within that port group receives the command. - Whenever a LUN is in 'transitioning' mode we cannot block I/O to that LUN, instead the controller has to abort the command. This leads to increased traffic across the wire and heavy load on the controller during switchover. With this patch the RTPG handling is moved to a per-portgroup workqueue. This reduces the number of 'REPORT TARGET PORT GROUP' and 'SET TARGET PORT GROUPS' sent to the controller as we're sending them now per port group, and not per device as previously. It also allows us to block I/O to any LUN / port group found to be in 'transitioning' ALUA mode, as the workqueue item will be requeued until the controller moves out of transitioning.
Reviewed-by: Bart Van Assche <bart.vanassche@xxxxxxxxxxx> -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
