Re: [PATCH] backing dev unplugging

Miquel van Smoorenburg
2004-03-10T21:43:31Z

In article <20040310210207.GL15087@suse.de>,
Jens Axboe <axboe@suse.de> wrote:
>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.

With the latest patches from Joe it would be more like

map = dm_get_table(md);
if (map) {
dm_table_unplug_all(map);
dm_table_put(map);
}

No lock ranking issues, you just get a refcounted map (table, really).

Mike.