linux-kernel - Re: [PATCH] xen-blkback: Switch to closed state after releasing the backing device

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Message-ID: <20180905162801.GB26705@gavran.carpriv.carnet.hr>
Date:   Wed, 5 Sep 2018 18:28:01 +0200
From:   Valentin Vidic <Valentin.Vidic@...Net.hr>
To:     Roger Pau Monné <roger.pau@...rix.com>
Cc:     Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        Jens Axboe <axboe@...nel.dk>, xen-devel@...ts.xenproject.org,
        linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org, drbd-user@...ts.linbit.com
Subject: Re: [PATCH] xen-blkback: Switch to closed state after releasing the
 backing device

On Wed, Sep 05, 2018 at 01:35:15PM +0200, Valentin Vidic wrote:
> > AFAICT, this will cause the backend to never switch to 'Closed' state
> > until the toolstack sets online to 0, which is not good IMO.
> > 
> > If for example a frontend decides to close a device, the backend will
> > stay in state 'Closing' until the toolstack actually removes the disk
> > by setting online to 0.
> > 
> > This will prevent resetting blk connections, as blkback will refuse to
> > switch to state XenbusStateInitWait unless it's at XenbusStateClosed
> > (see the XenbusStateInitialising case in frontend_changed), which will
> > never be reached with your patch.

Would it be possible to call xen_vbd_free before the state change?

        case XenbusStateClosed:
                xen_blkif_disconnect(be->blkif);
                xen_vbd_free(&be->blkif->vbd);
                xenbus_switch_state(dev, XenbusStateClosed);

-- 
Valentin