hch's native NVMe multipathing [was: Re: [PATCH 1/2] Don't blacklist nvme]

[Mike Snitzer]

On Thu, Feb 16 2017 at 12:00am -0500,
Bart Van Assche <bart.vanassche at sandisk.com> wrote:

> On 02/15/17 18:53, Mike Snitzer wrote:
> >Nobody has interest in Linux multipathing becoming fragmented.
> >
> >If every transport implemented their own multipathing the end-user would
> >be amazingly screwed trying to keep track of all the
> >quirks/configuration/management of each.
> >
> >Not saying multipath-tools is great, nor that DM multipath is god's
> >gift.  But substantiating _why_ you need this "native NVMe
> >multipathing" would go a really long way to justifying your effort.
> >
> >For starters, how about you show just how much better than DM multipath
> >this native NVMe multipathing performs?  NOTE: it'd imply you put effort
> >to making DM multipath work with NVMe.. if you've sat on that code too
> >that'd be amazingly unfortunate/frustrating.
> 
> Another question is what your attitude is towards dm-mpath changes?
> Last time I posted a series of patches that significantly clean up
> and improve readability of the dm-mpath code you refused to take these upstream.

Weird.  I did push back on those changes initially (just felt like
churn) but I ultimately did take them:

$ git log --oneline --author=bart drivers/md/dm-mpath.c
6599c84 dm mpath: do not modify *__clone if blk_mq_alloc_request() fails
4813577 dm mpath: change return type of pg_init_all_paths() from int to void
9f4c3f8 dm: convert wait loops to use autoremove_wake_function()

Did I miss any?

But to be 100% clear, I'm very appreciative of any DM mpath (and
request-based DM core) changes.  I'll review them with a critical eye
but if they hold up they get included.

Mike