Re: bd_mount_mutex -> bd_mount_sem (was Re: xfs_file_ioctl / xfs_freeze: BUG: warning at kernel/mutex-debug.c:80/debug_mutex_unlock())

[Eric Sandeen <sandeen@sandeen.net>]

Andrew Morton wrote:
> On Mon, 08 Jan 2007 21:12:40 -0600
> Eric Sandeen <sandeen@sandeen.net> wrote:
> 
>> Andrew Morton wrote:
>>> On Tue, 9 Jan 2007 10:47:28 +1100
>>> David Chinner <dgc@sgi.com> wrote:
>>>
>>>> On Mon, Jan 08, 2007 at 10:40:54AM -0600, Eric Sandeen wrote:
>>>>> Sami Farin wrote:
>>>>>> On Mon, Jan 08, 2007 at 08:37:34 +1100, David Chinner wrote:
>>>>>> ...
>>>>>>>> fstab was there just fine after -u.
>>>>>>> Oh, that still hasn't been fixed?
>>>>>> Looked like it =)
>>>>> Hm, it was proposed upstream a while ago:
>>>>>
>>>>> http://lkml.org/lkml/2006/9/27/137
>>>>>
>>>>> I guess it got lost?
>>>> Seems like it. Andrew, did this ever get queued for merge?
>>> Seems not.  I think people were hoping that various nasties in there
>>> would go away.  We return to userspace with a kernel lock held??
>> Is a semaphore any worse than the current mutex in this respect?  At 
>> least unlocking from another thread doesn't violate semaphore rules.  :)
> 
> I assume that if we weren't returning to userspace with a lock held, this
> mutex problem would simply go away.
> 

Well nobody's asserting that the filesystem must always be locked & 
unlocked by the same thread, are they?  That'd be a strange rule to 
enforce upon the userspace doing the filesystem management wouldn't it? 
  Or am I thinking about this wrong...

-Eric