On 04/18/2011 11:19 AM, hch@xxxxxxxxxxxxx wrote:
Btw, I really start to wonder if the request level is the right place
to do this on-stack plugging. Wouldn't it be better to just plug
bios in the on-stack queue? That way we could also stop doing the
special case merging when adding to the plug list, and leave all the
merging / I/O schedule logic in the __make_request path. Probably
not .39 material, but worth a prototype?
Also what this dicussion brought up is that the block layer data
structures are highly confusing. Using a small subset of the
request_queue also for make_request based driver just doesn't make
sense. It seems like we should try to migrate the required state
to struct gendisk, and submit I/O through a block_device_ops.submit
method, leaving the request_queue as an internal abstraction for
the request based drivers.
Good point.
It would also help us we the device-mapper redesign agk and myself
discussed at LSF. Having a block_device_ops.submit function would
allow us remap the actual request queue generically; and we would
even be able to address more than one request queue, which sounds
awfully similar to what Jens is trying to do ...
Cheers,
Hannes
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Dr. Hannes Reinecke zSeries & Storage
hare@xxxxxxx +49 911 74053 688
SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: Markus Rex, HRB 16746 (AG Nürnberg)
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