From: Eric Sandeen <sandeen@redhat.com>
Subject: Re: freeze_bdev hangs
Date: Fri, 05 Oct 2012 12:33:26 -0500
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Cc: linux-ext4@vger.kernel.org
To: Prashant Shah <pshah.mumbai@gmail.com>
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On 10/5/12 6:58 AM, Prashant Shah wrote:
> Hi,
> 
> I am writing a filter driver for ext3 in which it replaces the block
> device request queue 'make_request_fn' with the driver custom
> function. Calling freeze_bdev() or freeze_super() before replacing the
> 'make_request_fn' hangs the kernel. What am I doing wrong ? Will this
> method work ?

I haven't looked at your custom code, but freeze has changed a bit lately,
and "hangs" is a very vague description

For starters I'd try a sysrq-w when the system "hangs" and see where things
are at, that would offer you some clues.

-Eric