Re: [Xen-devel] Re: [PATCH 2/2] Fix and clean up vscsi_util.py andother files

[Masaki Kanno <kanno.masaki@xxxxxxxxxxxxxx>]

Hi Ian,

Tue, 21 Oct 2008 11:00:26 +0100, Ian Jackson wrote:

>Masaki Kanno writes ("[PATCH 2/2] Fix and clean up vscsi_util.py and other 
>files"):
>> Fix and clean up vscsi_util.py and other files
>> Signed-off-by: Masaki Kanno <kanno.masaki@xxxxxxxxxxxxxx>
>
>Thanks.  This looks like a definite improvement.  I think it should
>make the vscsi stuff more or less harmless in situations where it's
>not being used.
>
>So:
> Acked-by: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>

Thanks.


>However, are you sure that the approach taken in vscsi_util.py is the
>right one ?  The set of scsi devices available on a system may change
>over time, so it is not correct to try to build a list at startup.

"startup" which you pointed out is xm create, isn't it?
Or xend start?

If xm create, I think that the xm utility does not affect non-pvscsi 
users.  Non-pvscsi users return at line 702, so the xm utility is not 
called by xm create.

696 def configure_vscsis(config_devs, vals):
697     """Create the config for vscsis (virtual scsi devices).
698     """
699     devidlist = []
700     config_scsi = []
701     if len(vals.vscsi) == 0:
702         return 0
703 
704     scsi_devices = vscsi_util.vscsi_get_scsidevices()
705     for (p_dev, v_dev, backend) in vals.vscsi:
706         (p_hctl, devname) = \
707             vscsi_util.vscsi_get_hctl_and_devname_by(p_dev, scsi_devices)

Best regards,
 Kan

>Also, doing so will slow down startup (including startup time of the
>xm utility) on systems with many scsi devices even when pvscsi is not
>in use, and exposes non-pvscsi users to bugs in the pvscsi system (as
>previously discussed).
>
>Surely there must be some way to do this lookup directly in /sys or
>whereever at the point of use, when we're instructed to pass through a
>specific device ?
>
>Ian.
>
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