From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Fri, 7 Sep 2018 00:03:25 +0200 From: Valentin Vidic To: Roger Pau =?iso-8859-1?Q?Monn=E9?= Cc: Konrad Rzeszutek Wilk , Jens Axboe , xen-devel@lists.xenproject.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, drbd-user@lists.linbit.com Message-ID: <20180906220325.GY26705@gavran.carpriv.carnet.hr> References: <20180829065214.23546-1-Valentin.Vidic@CARNet.hr> <20180905103649.edugijsjx4v2fbxd@mac.bytemobile.com> <20180905162756.GA26705@gavran.carpriv.carnet.hr> <20180906161421.ba35p6qx5rvktjos@mac.bytemobile.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 In-Reply-To: <20180906161421.ba35p6qx5rvktjos@mac.bytemobile.com> Subject: Re: [PATCH] xen-blkback: Switch to closed state after releasing the backing device List-ID: On Thu, Sep 06, 2018 at 06:14:21PM +0200, Roger Pau Monn� wrote: > On Wed, Sep 05, 2018 at 06:27:56PM +0200, Valentin Vidic wrote: > > On Wed, Sep 05, 2018 at 12:36:49PM +0200, Roger Pau Monn� wrote: > > > On Wed, Aug 29, 2018 at 08:52:14AM +0200, Valentin Vidic wrote: > > > > Switching to closed state earlier can cause the block-drbd > > > > script to fail with 'Device is held open by someone': > > > > > > > > root: /etc/xen/scripts/block-drbd: remove XENBUS_PATH=backend/vbd/6/51712 > > > > kernel: [ 2222.278235] block drbd6: State change failed: Device is held open by someone > > > > kernel: [ 2222.278304] block drbd6: state = { cs:Connected ro:Primary/Secondary ds:UpToDate/UpToDate r----- } > > > > kernel: [ 2222.278340] block drbd6: wanted = { cs:Connected ro:Secondary/Secondary ds:UpToDate/UpToDate r----- } > > > > root: /etc/xen/scripts/block-drbd: Writing backend/vbd/6/51712/hotplug-error /etc/xen/scripts/block-drbd failed; error detected. backend/vbd/6/51712/hotplug-status error to xenstore. > > > > root: /etc/xen/scripts/block-drbd: /etc/xen/scripts/block-drbd failed; error detected. > > > > > > > > Signed-off-by: Valentin Vidic > > > > Cc: stable@vger.kernel.org > > > > --- > > > > drivers/block/xen-blkback/xenbus.c | 2 +- > > > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > > > > > diff --git a/drivers/block/xen-blkback/xenbus.c b/drivers/block/xen-blkback/xenbus.c > > > > index a4bc74e72c39..43bddc996709 100644 > > > > --- a/drivers/block/xen-blkback/xenbus.c > > > > +++ b/drivers/block/xen-blkback/xenbus.c > > > > @@ -323,6 +323,7 @@ static void xen_blkif_free(struct xen_blkif *blkif) > > > > { > > > > WARN_ON(xen_blkif_disconnect(blkif)); > > > > xen_vbd_free(&blkif->vbd); > > > > + xenbus_switch_state(blkif->be->dev, XenbusStateClosed); > > > > kfree(blkif->be->mode); > > > > kfree(blkif->be); > > > > > > > > @@ -814,7 +815,6 @@ static void frontend_changed(struct xenbus_device *dev, > > > > > > > > case XenbusStateClosed: > > > > xen_blkif_disconnect(be->blkif); > > > > - xenbus_switch_state(dev, XenbusStateClosed); > > > > if (xenbus_dev_is_online(dev)) > > > > break; > > > > > > 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. > > > > Ok, is it possible to test this somehow? > > Yes, you can try booting a PV guest with pvgrub, that will cause > pvgrub to open a blk connection, then close it and afterwards the OS > kernel will start a new connection. Indeed the boot hangs after pvgrub loads the kernel and initrd, so it seems this does not work as expected. -- Valentin