[dm-devel] blk-mq DM changes for 3.20 [was: Re: blk-mq request allocation stalls]

[Jens Axboe]

On 01/27/2015 11:42 AM, Mike Snitzer wrote:
> Hey Jens,
>
> I _think_ we've resolved the issues Bart raised for request-based DM's
> support for blk-mq devices (anything remaining seems specific to iSER's
> blk-mq support which is in development).  Though Keith did have that one
> additional patch for that block scatter gather attribute that we still
> need to review closer.
>
> Anyway, I think what we have is a solid start and see no reason to hold
> these changes back further.  So I've rebased the 'dm-for-3.20' branch of
> linux-dm.git ontop of 3.19-rc6 and reordered the required block changes
> to be at the front of the series, see:
> https://git.kernel.org/cgit/linux/kernel/git/device-mapper/linux-dm.git/log/?h=dm-for-3.20
>
> (these changes have been in Linux next for a month, via linux-dm.git
> 'for-next')
>
> With your OK, I'd be happy to carry the required block changes and
> ultimately request Linus pull them for 3.20 (I can backfill your Acks if
> you approve).  BUT I also have no problem with you picking up the block
> changes to submit via your block tree (I'd just have to rebase ontop of
> your 3.20 branch once you pull them in).

I'd prefer to take these prep patches through the block tree. Only one I 
don't really like is this one:

https://git.kernel.org/cgit/linux/kernel/git/device-mapper/linux-dm.git/commit/?h=dm-for-3.20&id=23556c2461407495099d1eb20b0de43432dc727d

I prefer keeping the alloc path as lean as possible, normal allocs 
always initialize ->bio since they need to associate a bio with it. Do
you have the oops trace from this one? Just curious if we can get rid of 
it, depending on how deep in the caller this is.

-- 
Jens Axboe