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Date: Tue, 30 Jan 2018 13:30:11 -0700
From: Keith Busch <keith.busch@intel.com>
To: Jens Axboe <axboe@kernel.dk>
Cc: "linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
	Christoph Hellwig <hch@lst.de>, Ming Lei <ming.lei@redhat.com>,
	"linux-nvme@lists.infradead.org" <linux-nvme@lists.infradead.org>
Subject: Re: WARNING: CPU: 2 PID: 207 at drivers/nvme/host/core.c:527
 nvme_setup_cmd+0x3d3
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 <0872b361-157b-a876-20af-3d7a4ee7ff31@kernel.dk>
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On Tue, Jan 30, 2018 at 08:57:49AM -0700, Jens Axboe wrote:
> 
> Looking at the disassembly, 'n' is 2 and 'segments' is 0xffff.

Is this still a problem if you don't use an IO scheduler? With deadline,
I'm not finding any path to bio_attempt_discard_merge which is where the
nr_phys_segments is supposed to get it set to 2. Not sure how it could
becmoe 0xffff, though.