linux-kernel - Re: [Xen-devel] [PATCH] xen-blkfront: emit KOBJ

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Date:   Wed, 05 Jul 2017 06:53:25 -0600
From:   "Jan Beulich" <JBeulich@...e.com>
To:     "Vincent Legout" <vincent.legout@...di.net>
Cc:     "Roger Pau Monné" <roger.pau@...rix.com>,
        <xen-devel@...ts.xenproject.org>,
        "Boris Ostrovsky" <boris.ostrovsky@...cle.com>,
        "Juergen Gross" <jgross@...e.com>, <linux-kernel@...r.kernel.org>
Subject: Re: [Xen-devel] [PATCH] xen-blkfront: emit KOBJ_OFFLINE uevent
 when detaching device

>>> On 05.07.17 at 14:37, <vincent.legout@...di.net> wrote:
> On Wed, Jul 05, 2017 at 02:17:24AM -0600, Jan Beulich wrote :
>> >>> On 05.07.17 at 10:08, <vincent.legout@...di.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?

Jan