Re: Revert "dm mpath: remove unnecessary NVMe branching in favor of scsi_dh checks"

[Mike Snitzer <snitzer@redhat.com>]

On Tue, Mar 13 2018 at  1:10pm -0400,
Bart Van Assche <Bart.VanAssche@wdc.com> wrote:

> On Tue, 2018-03-13 at 13:07 -0400, Mike Snitzer wrote:
> > Just a thought: Maybe dm-4.16 (rc4 based) is missing a blk-mq fix?
> > 
> > Might be worth cherry-picking the 2 topmost commits from dm-4.16 into
> > the linus-based (rc5) tree you reported the original issue against?
> > 
> > (looking at jens' rc5 block pull request, it seems unlikely but...)
> 
> Hello Mike,
> 
> Even if that would be the case, that can't have been the cause of what I
> reported. Before I run any dm tests I merge the block layer, SCSI and RDMA
> changes that are scheduled for the next kernel version into the dm tree.

Well I've rebased dm-4.16 ontop of v4.15-rc5.  If you udate to latest
dm-4.16 and look at the following diff it is pretty clear that these
changes will not compromise dm-mpath's "mq" mode (which you're using):

git diff 8d47e65948ddea4398892946d9e50778a316b397^..e8f74a0f00113d74ac18d6de13096f9e2f95618a -- drivers/md/dm-mpath.c

I see no reason why you'd hit hangs with requests lingering on the requeue_list