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

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Message-ID: <54EC14F9.5010409@suse.com>
Date:	Tue, 24 Feb 2015 07:06:49 +0100
From:	Juergen Gross <jgross@...e.com>
To:	Boris Ostrovsky <boris.ostrovsky@...cle.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 02/18/2015 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.

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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