Flood of SCSI retries when a port is in transitioning
Hi all,
our friends from NetApp discovered a SCSI retry flood when a remote port is in ALUA 'transitioning' state.
The device will then return
Not ready/LUN Not Accessible - ALUA state transition
which will be evaluated in scsi_dh_alua.c:alua_check_sense()
as ADD_TO_MLQUEUE.
This will cause an immediate retry of the command and hence the target will be pounded with a flood of retries.
I have now tried to alleviate this by returning 'NEEDS_RETRY',
drivers/scsi/device_handler/scsi_dh_alua.c +1 -1
@@ -451,7 +451,7 @@ static int alua_check_sense(struct scsi_device *sdev,/* * LUN Not Accessible - ALUA state transition */ -return ADD_TO_MLQUEUE ; +return NEEDS_RETRY ;if (sense_hdr->asc ==0x04 && sense_hdr->ascq ==0x0b )/* * LUN Not Accessible -- Target port in
standby state
but then the command will be aborted after the retry count has been exhausted. Which will then cause I/O errors. Also not good. Is there a way of forcing a delayed retry, like BLKPREP_DEFER does?
Cheers,
Hannes
Signature · 8 lines
Dr. Hannes Reinecke zSeries & Storage [email protected] +49 911 74053 688 SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg GF: J. Hawn, J. Guild, F. Imendörffer, HRB 16746 (AG Nürnberg) -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html