Messages in this thread | | | Date | Wed, 10 Mar 2004 22:02:07 +0100 | From | Jens Axboe <> | Subject | Re: [PATCH] backing dev unplugging |
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On Wed, Mar 10 2004, Andrew Morton wrote: > Jens Axboe <axboe@suse.de> wrote: > > > > Here's a first cut at killing global plugging of block devices to reduce > > the nasty contention blk_plug_lock caused. > > Shouldn't we take read_lock(&md->map_lock) in dm_table_unplug_all()?
Ugh yes, we certainly should.
> If so, what are the lock ranking issues here? The queue lock is not > held yet, so it seems pretty simple?
As far as I can tell, it's pretty straight forward. The unplug_fn() will grab the queue lock for 'ordinary' devices, for dm on dm you'd nest the maplock inside each other (which should be quite alright, as far as I can tell, without pulling any nasty tricks).
-- Jens Axboe
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