Re: [Xen-devel] [PATCH V2 2/3] xen: scsiback: add LUN of restored domain

[Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>]

On 02/24/2015 01:06 AM, Juergen Gross wrote:
> On 02/18/2015 06:02 PM, Boris Ostrovsky wrote:
> > On 02/17/2015 02:02 AM, Juergen Gross wrote:
> > > When a xen domain is being restored the LUN state of a pvscsi device
> > > is "Connected" and not "Initialising" as in case of attaching a new
> > > pvscsi LUN.
> > >
> > > This must be taken into account when adding a new pvscsi device for
> > > a domain as otherwise the pvscsi LUN won't be connected to the
> > > SCSI target associated with it.
> >
> > scsiback_do_add_lun() is being called from scsiback_frontend_changed()
> > which eventually sets the state to Connected. Is the added test of
> > 'try' an optimization or is it needed for correctness?
> It's needed for correctness. In case of resume the translation entry
> will be already existing, thus scsiback_add_translation_entry() will
> return a value unequal to zero. We don't want to set the device state
> to "Closed" in this case.

Right, I understand that. I thought that after you

        xenbus_printf(XBT_NIL, info->dev->nodename, state,
                    "%d", XenbusStateClosed);

in scsiback_do_add_lun() you'd eventually

        xenbus_switch_state(dev, XenbusStateConnected);

in scsiback_frontend_changed().

What I didn't realize was that this switch would only happen if 
dev->state is not XenbusStateConnected, which it still will be, even 
after xenbus_printf(XenbusStateClosed).
So

Reviewed-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>

> Juergen
>
> > -boris
> >
> >
> > > Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
> > > ---
> > >   drivers/xen/xen-scsiback.c | 19 ++++++++++++++-----
> > >   1 file changed, 14 insertions(+), 5 deletions(-)
> > >
> > > diff --git a/drivers/xen/xen-scsiback.c b/drivers/xen/xen-scsiback.c
> > > index 9faca6a..9d60176 100644
> > > --- a/drivers/xen/xen-scsiback.c
> > > +++ b/drivers/xen/xen-scsiback.c
> > > @@ -992,7 +992,7 @@ found:
> > >   }
> > >
> > >   static void scsiback_do_add_lun(struct vscsibk_info *info, const
> > > char *state,
> > > -                char *phy, struct ids_tuple *vir)
> > > +                char *phy, struct ids_tuple *vir, int try)
> > >   {
> > >       if (!scsiback_add_translation_entry(info, phy, vir)) {
> > >           if (xenbus_printf(XBT_NIL, info->dev->nodename, state,
> > > @@ -1000,7 +1000,7 @@ static void scsiback_do_add_lun(struct
> > > vscsibk_info *info, const char *state,
> > >               pr_err("xen-pvscsi: xenbus_printf error %s\n", state);
> > >               scsiback_del_translation_entry(info, vir);
> > >           }
> > > -    } else {
> > > +    } else if (!try) {
> > >           xenbus_printf(XBT_NIL, info->dev->nodename, state,
> > >                     "%d", XenbusStateClosed);
> > >       }
> > > @@ -1060,10 +1060,19 @@ static void scsiback_do_1lun_hotplug(struct
> > > vscsibk_info *info, int op,
> > >
> > >       switch (op) {
> > >       case VSCSIBACK_OP_ADD_OR_DEL_LUN:
> > > -        if (device_state == XenbusStateInitialising)
> > > -            scsiback_do_add_lun(info, state, phy, &vir);
> > > -        if (device_state == XenbusStateClosing)
> > > +        switch (device_state) {
> > > +        case XenbusStateInitialising:
> > > +            scsiback_do_add_lun(info, state, phy, &vir, 0);
> > > +            break;
> > > +        case XenbusStateConnected:
> > > +            scsiback_do_add_lun(info, state, phy, &vir, 1);
> > > +            break;
> > > +        case XenbusStateClosing:
> > >               scsiback_do_del_lun(info, state, &vir);
> > > +            break;
> > > +        default:
> > > +            break;
> > > +        }
> > >           break;
> > >
> > >       case VSCSIBACK_OP_UPDATEDEV_STATE:
> > --
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