Re: udev / multipath-tools: WWID determination with SG_IO vs. sysfs

[Benjamin Marzinski <bmarzins@redhat.com>]

On Thu, Nov 12, 2026 at 09:47:54PM +0100, Martin Wilck wrote:
> On Thu, 2026-11-12 at 14:58 -0500, Benjamin Marzinski wrote:
> > On Thu, Nov 12, 2026 at 08:00:58PM +0100, Martin Wilck wrote:
> > 
> >  
> > > Brian's patch would add more such ioctls and thus increase the
> > > likelihood of observing a stall. To be observed.
> > > 
> > 
> > This is true, and unlike the existing recheck_wwids use and the
> > prioritizer, it won't be called right after the path checker
> > determined
> > a path to be up. We do also do SG_IO ioctls in pathinfo when DI_IOCTL
> > is
> > set (when we're adding a path, reconfiguring multipath, or
> > initializing
> > a partial path). In that case we do check if the path is up according
> > to
> > sysfs first, but we don't call the checker.
> 
> So, would you prefer making it conditional on something else but
> "recheck_wwid"?

Since recheck_wwid is set, we could just limit this new
check_path_wwid_change() check in ev_add_path() to paths that are up.
uev_add_path() will run the path checker before we get here. If the path
isn't up, recheck_wwid guarantees that we will do the check when the
path is up.

That should make this no more risky than the existing recheck_wwid
calls.

-Ben
 
> Martin
> 
> -- 
> Dr. Martin Wilck <mwilck@suse.com>
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