From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Subject: Re: WARNING: CPU: 2 PID: 207 at drivers/nvme/host/core.c:527 nvme_setup_cmd+0x3d3 To: Keith Busch Cc: "linux-block@vger.kernel.org" , Christoph Hellwig , Ming Lei , "linux-nvme@lists.infradead.org" References: <45f93661-da0d-94c5-1740-85242df8776e@kernel.dk> <0872b361-157b-a876-20af-3d7a4ee7ff31@kernel.dk> <20180130203011.GE27205@localhost.localdomain> From: Jens Axboe Message-ID: Date: Tue, 30 Jan 2018 13:32:25 -0700 MIME-Version: 1.0 In-Reply-To: <20180130203011.GE27205@localhost.localdomain> Content-Type: text/plain; charset=utf-8 List-ID: On 1/30/18 1:30 PM, Keith Busch wrote: > 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. blk_mq_make_request() -> blk_mq_sched_bio_merge() -> __blk_mq_sched_bio_merge() -> blk_mq_attempt_merge() -> bio_attempt_discard_merge() Doesn't matter what IO scheduler you use. I don't know if it triggers without a scheduler. I've been running this code continually on the laptop (always do), and haven't seen it before today. -- Jens Axboe