Re: Queue upcall locking (was: [dm-devel] [RFC][PATCH] fixdm_any_congested() to properly sync up with suspend code path)

[Christoph Hellwig]

On Mon, Nov 10, 2008 at 09:40:18AM -0500, Mikulas Patocka wrote:
> > - If the device is suspended, the response should be that it is 
> > congested, I'd have thought.
> 
> Yes, but these congestion upcalls are used only for optimization and the 
> device is suspended for so small time, that it doesn't matter if we 
> optimize io acces in small moment or not.

We use device congested to not block pdflush on a device that can't
currently accept I/O.  For a suspended device congested is always
correct, pdflush will just come back a little later and in the mean time
write out stuff that doesn't delay it.

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