[dm-devel] [PATCH 5/5] dm-mpath: convert to request-based

[Alasdair G Kergon]

On Tue, Jun 02, 2009 at 04:03:25PM +0900, Kiyoshi Ueda wrote:
> This patch converts dm-multipath target to request-based from bio-based.
 
How much effort would it be to retain the old mpath implementation
in parallel?

I'm rather concerned that we're losing some useful functionality in
2.6.31 with this patch - stacking over bio-based devices (test beds use
this and it's helpful for debugging), barrier support - and supporting
both would make it easier for people to compare the two implementations
and stick to the old one if in their particular circumstances it worked
better.

Perhaps, dm-mpath could just register two targets (like snapshot does),
one bio-based, and one rq-based, sharing most of the functions with
wrappers to indicate which is which where necessary?

Alasdair