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

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Date:	Tue, 24 Feb 2015 10:12:53 -0500
From:	Boris Ostrovsky <boris.ostrovsky@...cle.com>
To:	Juergen Gross <jgross@...e.com>, linux-kernel@...r.kernel.org,
	xen-devel@...ts.xensource.com, konrad.wilk@...cle.com,
	david.vrabel@...rix.com
Subject: Re: [PATCH V2 2/3] xen: scsiback: add LUN of restored domain

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@...cle.com>

>
> Juergen
>
>>
>> -boris
>>
>>
>>>
>>> Signed-off-by: Juergen Gross <jgross@...e.com>
>>> ---
>>>   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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>

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