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

[Alasdair G Kergon]

On Mon, Nov 10, 2008 at 08:54:01AM -0500, Christoph Hellwig wrote:
> On Mon, Nov 10, 2008 at 08:11:51AM -0500, Mikulas Patocka wrote:
> > For upstream Linux developers: you are holding a spinlock and calling 
> > bdi*_congested functions that can take indefinite amount of time (there 
> > are even users reporting having 50 disks in one logical volume or so). I 
> > think it would be good to move these calls out of spinlocks.
> Umm, they shouldn't block that long, as that completely defeats their
> purpose.  

Indeed - the blocking was a bug for which there's a patch, but that doesn't
deal with how the function should be operating in the first place.

- If one device is found to be congested, why bother checking the remaining
devices?

- If the device is suspended, the response should be that it is congested, I'd
have thought.

Alasdair
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