Missing SAS phy enumeration in newer versions of udev path_id

[Nils Carlson]

Hi,

We recently upgraded our version of udev and I saw that the symlinks
under /dev/disk/by-path/ have changed since udev started using the
path_id C code to no longer include phy enumeration for SAS disks. Was
this change intentional? Would anyone mind if i re-create the behavior
of the old bash script as we were using it?

Best Regards,
Nils Carlson

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[Hannes Reinecke]

Post by Nils Carlson
Hi,
=20
We recently upgraded our version of udev and I saw that the symlinks
under /dev/disk/by-path/ have changed since udev started using the
path_id C code to no longer include phy enumeration for SAS disks.
Was this change intentional? Would anyone mind if i re-create the
behavior of the old bash script as we were using it?
=20

Not everybody at once ... I've just had several customer calls for
exactly the same issue.

Actually ... the company name seems to be vaguely familiar ...

Post by Nils Carlson
Problem is that SAS has something called 'wide-ports', ie inherent
port-bonding for SAS. When a system has wide ports, several PHYs
are merged _physically_ together into a single connector.
However, on the system side we're only seeing PHYs, so it'
impossible to tell which of the phy has been used.
So to handle this correctly we would need to generate symlinks for
each phy in a wide port; however, currently the path_id program is
only capable of printing out _one_ link per wide port.
And actually, the original path_id script also printed out only
one symlink, so even there it didn't handle wide ports correctly.

I've discussed this issue with Kay Sievers, and we agreed that we
should be fixing this.
It should be relatively easy to update the path_id program to print
out a link for each phy in a wide-port, and then we could do a
static enumeration via udev rules like

$env{ID_SAS_PHY0}=3D=3D"?*", SYMLINK+=3D"/dev/disk/by-path/$ID_SAS_PHY0=
"
$env{ID_SAS_PHY1}=3D=3D"?*", SYMLINK+=3D"/dev/disk/by-path/$ID_SAS_PHY1=
"

seeing that there is currently a max of 8 phys per wide port, we
only would need to specify 8 lines here. Which should be too bad.

You're welcome to lend a hand ...

Cheers,

Hannes
--=20
Dr. Hannes Reinecke zSeries & Storage
***@suse.de [phone]
SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 N=FCrnberg
GF: J. Hawn, J. Guild, F. Imend=F6rffer, HRB 16746 (AG N=FCrnberg)
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