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Re: Queue upcall locking (was: [dm-devel] [RFC][PATCH] fix dm_any_congested() to properly sync up with suspend code path)
- From: Alasdair G Kergon <agk redhat com>
- To: Christoph Hellwig <hch infradead org>
- Cc: axboe kernel dk, dm-devel <dm-devel redhat com>, Mikulas Patocka <mpatocka redhat com>, linux-kernel vger kernel org
- Subject: Re: Queue upcall locking (was: [dm-devel] [RFC][PATCH] fix dm_any_congested() to properly sync up with suspend code path)
- Date: Mon, 10 Nov 2008 14:27:15 +0000
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
--
agk redhat com
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