Date: Fri, 7 Jul 2017 09:10:53 +0100
From: Roger Pau =?iso-8859-1?Q?Monn=E9?= <roger.pau@citrix.com>
To: Vincent Legout <vincent.legout@gandi.net>
CC: Jan Beulich <JBeulich@suse.com>, <xen-devel@lists.xenproject.org>,
        Boris Ostrovsky <boris.ostrovsky@oracle.com>,
        Juergen Gross <jgross@suse.com>, <linux-kernel@vger.kernel.org>
Subject: Re: [Xen-devel] [PATCH] xen-blkfront: emit KOBJ_OFFLINE uevent when
 detaching device
Message-ID: <20170707081053.s6pocjgz3ibkkyjg@dhcp-3-128.uk.xensource.com>
References: <20170704114823.pvk6323gfebioikl@bres.gandi.net>
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 <20170705080804.j6lptyhmjguhdj47@bres.gandi.net>
 <595CBCB40200007800168A16@prv-mh.provo.novell.com>
 <20170705123715.exc4qyllpxatxpnj@bres.gandi.net>
 <595CFD650200007800168BF1@prv-mh.provo.novell.com>
 <20170705133000.ugnbckhul4xevzk5@bres.gandi.net>
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On Wed, Jul 05, 2017 at 03:30:00PM +0200, Vincent Legout wrote:
> On Wed, Jul 05, 2017 at 06:53:25AM -0600, Jan Beulich wrote :
> > >>> On 05.07.17 at 14:37, <vincent.legout@gandi.net> wrote:
> > > On Wed, Jul 05, 2017 at 02:17:24AM -0600, Jan Beulich wrote :
> > >> >>> On 05.07.17 at 10:08, <vincent.legout@gandi.net> wrote:
> > >> > Without the patch, blkif_release and xlvbd_release_gendisk are never
> > >> > called, and no call to blk_unregister_queue is made.
> > >> 
> > >> But isn't that what needs to be fixed then? The device should be
> > >> removed once its last user goes away (which would be at the time
> > >> the umount is eventually done aiui).
> > > 
> > > You mean that block-detach should fail if the device is still mounted?
> > > or find a way to wait until all the users are gone?
> > > 
> > > I don't say that's not what should be done, but that's not what I get.
> > > The device is removed after a block-detach, even if still mounted. So
> > > the system is left in an unstable state without the patch.
> > 
> > Unstable? I'd expect subsequent I/O to fail for that device, yes, but
> > that's still a stable system. Are you observing anything else?
> 
> Yes, that's what I meant by unstable, nothing else. Sorry for the
> confusion.

IMHO, this should behave in the same exact way as hot-unplugging a USB
drive that's mounted, can you confirm that's correct?

Roger.