[dm-devel] Re: [PATCH 2.6.19 5/5] fs: freeze_bdev with semaphore not mutex

[Pavel Machek <pavel ucw cz>]

On Fri 2006-11-10 11:57:49, David Chinner wrote:
> On Thu, Nov 09, 2006 at 11:21:46PM +0100, Rafael J. Wysocki wrote:
> > I think we can add a flag to __create_workqueue() that will indicate if
> > this one is to be running with PF_NOFREEZE and a corresponding macro like
> > create_freezable_workqueue() to be used wherever we want the worker thread
> > to freeze (in which case it should be calling try_to_freeze() somewhere).
> > Then, we can teach filesystems to use this macro instead of
> > create_workqueue().
> 
> At what point does the workqueue get frozen? i.e. how does this
> guarantee an unfrozen filesystem will end up in a consistent
> state?

Snapshot is atomic; workqueue will be unfrozen with everyone else, but
as there were no writes in the meantime, there should be no problems.

									Pavel
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