[dm-devel] [PATCH RESEND 0/4] multipath-tools: fixes for path wwid detection and path change uevents

[Martin Wilck]

Hi Ben, Christophe,

I found a problem with this old patch series of mine.

On Wed, 2018-03-14 at 12:40 -0500, Benjamin Marzinski wrote:
> On Thu, Mar 08, 2018 at 12:21:48AM +0100, Martin Wilck wrote:
> > Hi Christophe,
> > 
> > this small series fixes some minor glitches I found in the current
> > path
> > discovery code, and attempts to implement the safe part of the
> > functionality
> > discussed in the thread "multipathd: update path's udev in
> > uev_update_path"
> > in January (based on an idea from Wu Chongyun).
> > 
> > Resending the series, unchanged, rebased on 0.7.5.
> > 
> > Regards,
> > Martin
> > 
> 
> Reviewed-by: Benjamin Marzinski <bmarzins at redhat.com>
> 
> for the set.
> 
> > Martin Wilck (4):
> >   libmultipath: get_uid: check VPD pages for SCSI only
> >   libmultipath: get_uid: don't quit prematurely without udev
> >   libmultipath: uev_update_path: always warn if WWID changed
> >   libmultipath: uev_update_path: update path properties

while I am still pondering about your latest series, it occured to me
that my patch "get_uid: don't quit prematurely without udev" is against
the spirit of your "retrigger uevents to try and get the uid through
udev" patch from 2016 (688aa22b).

"get_uid: don't quit prematurely without udev" has been merged a while
ago (08d42ee6). Should it be reverted??

Pro: the patch is against the "udev first" philosophy and subverts the
retrigger logic.
Con: with the patch, we'll be able to retrieve WWIDs more quickly in
some situations, as we don't have to wait for udev.

Either way (but more likely with my patch), it may happen that we
retrieve a WWID from sysfs or elsewhere first, and from udev later.
These WWIDs may not necessarily match, and a "WWID changed" problem may
occur.

Please tell me what you think.

Martin


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