Messages in this thread | | | Date | Sun, 14 Mar 2004 22:09:08 +0100 | From | Jens Axboe <> | Subject | Re: [PATCH] per-backing dev unplugging #2 |
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On Sun, Mar 14 2004, Andrew Morton wrote: > Jens Axboe <axboe@suse.de> wrote: > > > > > I reproduced on 2.6.4-mm1 + backing dev, but 2.6.4-mm1 alone ran fine. > > > To make a long story short, the swap address space and backing dev don't > > > define an unplug_io_fn. I was able to reproduce quickly with a swap > > > heavy workload. The patch below should fix the oops, but probably isn't > > > correct solution since no queues will get unplugged while waiting on > > > swap pages. > > > > Duh of course, that's pretty silly actually. So the question is if we > > want to keep assigning a dummy unplug_io_fn (default_backing_dev already > > has it), or just keep the check. I propose to check like Chris added, > > and just kill the default_unplug_io_fn() from readahead.c > > > > I'd be inclined to leave that as-is actually. I'll run with Chris's patch > temporarily, but we need a real unplug function for swapper_space. Which > will leave default_backing_dev_info unique.
We were just discussing this on irc, btw. :-)
> I'll do swap_unplug_io_fn(). swap implements a poor-man's raid0. What are > the locking rules for the unplug function btw? It can sleep, yes?
There are no locking rules for bdi->unplug_io_fn(). You can sleep if the caller can sleep.
-- Jens Axboe
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