David Chinner wrote:
> On Thu, Dec 07, 2006 at 01:17:32PM -0500, Geir A. Myrestrand wrote:
>>> Geir A. Myrestrand wrote:
>>>
>>>> However, I run into issues with xfs_freeze as it often locks up when I 
>>>> try to freeze a file system where there is I/O activity. Sometimes it 
>>>> happen on the first xfs_freeze invocation to freeze the file system, 
>>>> other times I have to unfreeze and then it happens on the second time I 
>>>> freeze. xfs_freeze never returns when this happens.
>>>>
>>>> Looks like xfs_io get stuck --see partial output from `ps auxf`:
>>>>
>>>> strace -ff -o freeze.txt xfs_freeze -f /mnt/xfs
>>>>  \_ /bin/sh -f /usr/sbin/xfs_freeze -f /mnt/xfs
>>>>      \_ /usr/sbin/xfs_io -r -p xfs_freeze -x -c freeze /mnt/xfs
>>>>
>>>> Anyone else encountering this issue?
> 
> Yes, and I fixed it about a 2 weeks ago. It's an ABBA deadlock between
> lookup of multiple, already dirty, metadata buffers and synchronous buftarg
> flushing (that occurs when trying to freeze a filesystem)
> 
> <sigh>

That is awesome news, mate!  :-)

> The problem is that during a freeze, the filesystem may
> still be doing stuff - like flushing delalloc data buffers -
> in the background and hence we can be trying to lock buffers
> that were on the delwri list at the same time.  Hence we can
> get ABBA deadlocks between threads doing allocation and the
> buftarg flush (freeze) thread.

That sounds like an accurate description of my test environment. I bet 
this is the issue...

> Fix it by skipping locked (and pinned) buffers as we traverse the
> delwri buffer list.

Good to know that you're one step ahead!

> And the diff was:
> 
> http://oss.sgi.com/cgi-bin/cvsweb.cgi/linux-2.6-xfs/fs/xfs/linux-2.6/xfs_buf.c.diff?r1=1.229;r2=1.230

Excellent. I will try this tomorrow (it's late in the evening here in 
New York now). I'll let you know how it works out.

Thanks!


-- 

Geir A. Myrestrand