linux-kernel - Re: [PATCH 5/4] update ksm userspace interfaces

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Message-ID: <49D5EE1F.4060009@redhat.com>
Date:	Fri, 03 Apr 2009 13:08:15 +0200
From:	Gerd Hoffmann <kraxel@...hat.com>
To:	Izik Eidus <ieidus@...hat.com>
CC:	Chris Wright <chrisw@...hat.com>,
	Anthony Liguori <anthony@...emonkey.ws>,
	Andrea Arcangeli <aarcange@...hat.com>,
	linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
	linux-mm@...ck.org, avi@...hat.com, riel@...hat.com,
	jeremy@...p.org, mtosatti@...hat.com, hugh@...itas.com,
	corbet@....net, yaniv@...hat.com, dmonakhov@...nvz.org
Subject: Re: [PATCH 5/4] update ksm userspace interfaces

Izik Eidus wrote:
> Gerd Hoffmann wrote:
>> Did you test whenever it really cleans up in case you "kill -9 qemu"?
>>
>> I recently did something simliar with the result that the extra
>> reference hold on mm_struct prevented the process memory from being
>> zapped ...
>>
>> cheers,
>>   Gerd
>>   
> Did you use mmput() after you called get_task_mm() ???
> get_task_mm() do nothing beside atomic_inc(&mm->mm_users);

mmput() call was in ->release() callback, ->release() in turn never was
called because the kernel didn't zap the mappings because of the
reference ...

The driver *also* created mappings which ksmctl doesn't, so it could be
you don't run into this issue.

cheers,
  Gerd
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