On 12/12/2017 01:00 AM, Bart Van Assche wrote:
> On Fri, 2017-12-08 at 11:14 +0100, Hannes Reinecke wrote:
>> @@ -541,6 +544,20 @@ static int alua_rtpg(struct scsi_device *sdev, struct
>> alua_port_group *pg)
>> retval = submit_rtpg(sdev, buff, bufflen, &sense_hdr, pg->flags);
>>
>> if (retval) {
>> + /*
>> + * If the target only supports active/optimized there's
>> + * not much we can do; it's not that we can switch paths
>> + * or somesuch.
>> + * So ignore any errors to avoid spurious failures during
>> + * path failover.
>> + */
>> + if ((pg->valid_states & ~TPGS_SUPPORT_OPTIMIZED) == 0) {
>> + sdev_printk(KERN_INFO, sdev,
>> + "%s: ignoring rtpg result %d\n",
>> + ALUA_DH_NAME, retval);
>> + kfree(buff);
>> + return SCSI_DH_OK;
>> + }
>
> Hello Hannes,
>
> Sorry but this change looks weird to me. If an RTPG fails, shouldn't
> alua_rtpg() return SCSI_DH_IO independent of what ALUA states the target
> supports? Are you perhaps trying to implement a work-around for an array
> that does not respond to RTPG during path transitions?
>
Yes, precisely.
Thing is: if an array is only supporting active/optimized the entire
device-handler stuff is basically a no-op as we can't switch paths anyway.
So it doesn't really matter if the RTPG fails; in fact, we could just
short-circuit the entire logic. I did not do that to allow for a state
modification (ie arrays _might_ decide to announce additional states
eventually, and only starting off with active/optimized as an initial
state set).
But if we return SCSI_DH_IO here the multipath logic will not attempt to
switch paths, and failover will not work.
Cheers,
Hannes
--
Dr. Hannes Reinecke Teamlead Storage & Networking
[email protected] +49 911 74053 688
SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: F. Imendörffer, J. Smithard, J. Guild, D. Upmanyu, G. Norton
HRB 21284 (AG Nürnberg)
