On 3/26/26 13:16, John Garry wrote:
On 26/03/2026 10:19, Hannes Reinecke wrote:
@@ -80,6 +80,7 @@ config SCSI_MULTIPATH
bool "SCSI multipath support"
depends on SCSI_MOD
select LIBMULTIPATH
+ select SCSI_DH_ALUA
help
This option enables support for native SCSI multipath
support for
SCSI host.
And that is even enough, as Kconfigs should only specify build
requirements.
We really should be also calling something like scsi_dh_attach() for
scsi multipath to ensure that DH is attached (and running to update
sdev->access_state).
And I am not sure how the dh alua module is even autoloaded. I think
that on my ubuntu machine the multipath-tools.service does it -
something like this would not be nice for native SCSI multipath support.
Gnaa. But then we don't need this patchset at all.
Main point was that we _do not_ need to hook into scsi dh for implicit
ALUA.
But again I don't think that this is good enough. Native SCSI
multipathing will read sdev->access_state to know ALUA state. We can't
just rely on dh alua module running and doing what we need to know that
this value is valid. AFAICS, dm mpath relies on dh alua module to even
work at all:
device-mapper: table: 252:1: multipath: error attaching hardware
handler (-EINVAL)
At this point I am more inclined to just have a small SCSI core ALUA
support for implicit ALUA, and allow scsi_dh_alua.c reuse functions from
that but not use sdev->alua structure, like in this series - trying that
is turning into a mess, I am finding.
... where one finds himself inclined to think: 'told you so' :-)
And really, the SCSI alua handling doesn't need to be precise, in the
sense that the state is always up-to-date. It should be sufficient to
read the state once during startup, and then resend RTPG whenever we
get a sense code indicating that the ALUA state doesn't match.
We will be missing any changes between non-optimized and optimized,
but they are meaningless for the SCSI core anyway.
Cheers,
Hannes
--
Dr. Hannes Reinecke Kernel Storage Architect
[email protected] +49 911 74053 688
SUSE Software Solutions GmbH, Frankenstr. 146, 90461 Nürnberg
HRB 36809 (AG Nürnberg), GF: I. Totev, A. McDonald, W. Knoblich
