[dm-devel] [PATCH 20/31] 11-dm-mpath.rules: don't set READY->ACTIVATION

Martin Wilck mwilck at suse.com
Thu Sep 14 12:48:19 UTC 2017


On Wed, 2017-09-13 at 16:19 -0500, Benjamin Marzinski wrote:
> On Sun, Sep 03, 2017 at 12:38:49AM +0200, Martin Wilck wrote:
> > The fact alone that a map changes from not ready to ready does
> > not imply that it is activating.
> 
> NAK on this one and
> [PATCH 21/31] 11-dm-mpath.rules: Remember DM_ACTIVATION
> 
> This breaks things. It's often the case that there are devices
> stacked
> on top of multipath.  When multipath loses all of its paths, if it
> doesn't have queue_if_no_path set, it can fail IO up to these higher
> devices, forcing them to react to the failure.

Thinking about this again, most of the stuff we do in the multipath-
related udev rules is for the queueing case. Without
"queue_if_no_path", all that checking whether or not the map will
sustain IO is useless; it would be better to simply pass the device on
to upper layers, which will try to probe it and fail, which is intended
in the non-queueing setup. Perhaps we should check "queue_if_no_path"
early on and skip most of the stuff we  do in the queueing case?

If we did this, maybe even my patches 20/21 might be worth
reconsideration for the "queue_if_no_path" case only?

Cheers,
Martin

-- 
Dr. Martin Wilck <mwilck at suse.com>, Tel. +49 (0)911 74053 2107
SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton
HRB 21284 (AG Nürnberg)




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