linux-kernel - Re: [PATCH] 9p: disconnect channel when PCI device is removed

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Message-ID: <87ehrodjt6.fsf@skywalker.in.ibm.com>
Date:	Mon, 16 Apr 2012 16:29:01 +0530
From:	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
To:	Sasha Levin <levinsasha928@...il.com>
Cc:	davem@...emloft.net, ericvh@...il.com, jvrao@...ux.vnet.ibm.com,
	rusty@...tcorp.com.au, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, davej@...hat.com
Subject: Re: [PATCH] 9p: disconnect channel when PCI device is removed

Sasha Levin <levinsasha928@...il.com> writes:

> On Sun, Apr 15, 2012 at 2:27 PM, Aneesh Kumar K.V
> <aneesh.kumar@...ux.vnet.ibm.com> wrote:
>> Sasha Levin <levinsasha928@...il.com> writes:
>>
>>> When a virtio_9p pci device is being removed, we should close down any
>>> active channels and free up resources, we're not supposed to BUG() if there's
>>> still an open channel since it's a valid case when removing the PCI device.
>>>
>>> Otherwise, removing the PCI device with an open channel would cause the
>>> following BUG():
>>>
>> ...
>>
>>> diff --git a/net/9p/trans_virtio.c b/net/9p/trans_virtio.c
>>> index 3d43206..5af18d1 100644
>>> --- a/net/9p/trans_virtio.c
>>> +++ b/net/9p/trans_virtio.c
>>> @@ -615,7 +615,8 @@ static void p9_virtio_remove(struct virtio_device *vdev)
>>>  {
>>>       struct virtio_chan *chan = vdev->priv;
>>>
>>> -     BUG_ON(chan->inuse);
>>> +     if (chan->inuse)
>>> +             p9_virtio_close(chan->client);
>>>       vdev->config->del_vqs(vdev);
>>>
>>>       mutex_lock(&virtio_9p_lock);
>>
>> But an umount should have resulted in p9_virtio_close ? How are you
>> removing the device ? Are you removing the device with file system
>> mounted  ?. In that case may be we should return EBUSY ?
>
> I signal the underlying PCI device to remove (echo 1 >
> /sys/devices/pci0000\:00/[...]/remove), we can't really prevent that
> thing so we must clean up ourselves.

What does that mean for the mounted file system ? What would happen to
the pending fs operations in that case ?

-aneesh

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