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



On Fri 2006-11-17 10:23:49, David Chinner wrote:
> On Sun, Nov 12, 2006 at 11:43:05PM +0100, Rafael J. Wysocki wrote:
> > On Sunday, 12 November 2006 23:30, David Chinner wrote:
> > > And how does freezing them at that point in time guarantee consistent
> > > filesystem state?
> > 
> > If the work queues are frozen, there won't be any fs-related activity _after_
> > we create the suspend image. 
> 
> fs-related activity before or after the suspend image is captured is
> not a problem - it's fs-related activity _during_ the suspend that
> is an issue here. If we have async I/O completing during the suspend
> image capture, we've got problems....

fs-related activity _after_ image is captured definitely is a problem
-- it breaks swsusp invariants.

During image capture, any fs-related activity is not possible, as we
are running interrupts disabled, DMA disabled.
								Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html


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