From mboxrd@z Thu Jan  1 00:00:00 1970
From: Mike Snitzer <snitzer@redhat.com>
Subject: Re: blk-mq request allocation stalls
Date: Mon, 12 Jan 2015 14:11:39 -0500
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To: Keith Busch <keith.busch@intel.com>
Cc: Jens Axboe <axboe@kernel.dk>, Bart Van Assche <bart.vanassche@sandisk.com>, device-mapper development <dm-devel@redhat.com>, Jun'ichi Nomura <j-nomura@ce.jp.nec.com>, Christoph Hellwig <hch@infradead.org>
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On Mon, Jan 12 2015 at  1:35pm -0500,
Keith Busch <keith.busch@intel.com> wrote:

> On Mon, 12 Jan 2015, Keith Busch wrote:
> >Oh, let's look at "__blk_rq_prep_clone". dm calls that after
> >blk_get_request() for the blk-mq based multipath types and overrides the
> >destinations cmd_flags with the source's even though the source was not
> >allocated from a blk-mq based queue, much less a shared tag.
> 
> Untested patch. This will also preserve the failfast cmd_flag dm-mpath
> set after allocating.

Ah, good point.  The failfast flag would get cleared with the patch I
just proposed (unless REQ_FAILFAST_TRANSPORT was added to
REQ_PRESERVE_CLONE_MASK).

Anyway, I'm happy to see this implemented however you guys think is
best.  I think I like Keith's patch better than mine.