linux-kernel - Re: [PATCH net 1/2] vhost: use mutex_lock_nested() in vhost_dev_lock

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Message-Id: <20180124.165555.720252378850390746.davem@davemloft.net>
Date:   Wed, 24 Jan 2018 16:55:55 -0500 (EST)
From:   David Miller <davem@...emloft.net>
To:     mst@...hat.com
Cc:     jasowang@...hat.com, linux-kernel@...r.kernel.org,
        virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org
Subject: Re: [PATCH net 1/2] vhost: use mutex_lock_nested() in
 vhost_dev_lock_vqs()

From: "Michael S. Tsirkin" <mst@...hat.com>
Date: Wed, 24 Jan 2018 23:46:19 +0200

> On Wed, Jan 24, 2018 at 04:38:30PM -0500, David Miller wrote:
>> From: Jason Wang <jasowang@...hat.com>
>> Date: Tue, 23 Jan 2018 17:27:25 +0800
>> 
>> > We used to call mutex_lock() in vhost_dev_lock_vqs() which tries to
>> > hold mutexes of all virtqueues. This may confuse lockdep to report a
>> > possible deadlock because of trying to hold locks belong to same
>> > class. Switch to use mutex_lock_nested() to avoid false positive.
>> > 
>> > Fixes: 6b1e6cc7855b0 ("vhost: new device IOTLB API")
>> > Reported-by: syzbot+dbb7c1161485e61b0241@...kaller.appspotmail.com
>> > Signed-off-by: Jason Wang <jasowang@...hat.com>
>> 
>> Michael, I see you ACK'd this, meaning that you're OK with these two
>> fixes going via my net tree?
>> 
>> Thanks.
> 
> Yes - this seems to be what Jason wanted (judging by the net
> tag in the subject) and I'm fine with it.
> Thanks a lot.

Great, not a problem, done.