[dm-devel] [PATCHv2 0/4] blk-mq support for dm multipath

[Hannes Reinecke]

On 10/28/2014 07:13 PM, Keith Busch wrote:
> No comments this time. Did I totally botch this in the wrong direction,
> or was the timing bad with the linux con/plumbers that week?
> 
Basically the latter. We (ie hch and myself) discussed this briefly at
LPC, and thought it'd be the right step in the right direction.

'Real' multipath support w/ blk-mq would need some more thought, though.
What we've been discussing was to redo the entire I/O submission path:
a) pass down I/O _without_ cloning on the current path
b) clone the request _for retry_ only.
with b) covering retry on a different path and partial I/O submission
on the current path.
That would have the benefit doing away with the current request/bio
cloning. Plus we could even model things like 'preferred' path.

Now we only need someone to implement this ...

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		      zSeries & Storage
hare at suse.de			      +49 911 74053 688
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