Re: [PATCH 2/5] dm-mpath: return DM_MAPIO_REQUEUE in case of rq allocation failure

[Bart Van Assche <Bart.VanAssche@wdc.com>]

On Fri, 2017-09-15 at 16:06 -0400, Mike Snitzer wrote:
> The problem is that multipath_clone_and_map() is now treated as common
> code (thanks to both blk-mq and old .request_fn now enjoying the use of
> blk_get_request) BUT: Ming please understand that this code is used by
> old .request_fn too.  So it would seem that the use of
> DM_MAPIO_DELAY_REQUEUE vs DM_MAPIO_REQUEUE needs to be based on dm-sq vs
> dm-mq.

Hello Mike,

My proposal is to leave out patches 1 and 2 entirely. Since the SCSI core
calls blk_mq_run_hw_queues() anyway after a request has finished it is not
clear to me what the motivation was behind the development of patches 1 and
2 in this series. If the goal was to rerun a queue after a request has
finished I think the same approach should be taken for dm as for the SCSI
core, namely to run the queue from inside the end_io callback.

Bart.