From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752182AbdLEG5D (ORCPT ); Tue, 5 Dec 2017 01:57:03 -0500 Received: from mx1.redhat.com ([209.132.183.28]:42646 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751112AbdLEG5A (ORCPT ); Tue, 5 Dec 2017 01:57:00 -0500 Date: Tue, 5 Dec 2017 14:56:42 +0800 From: Ming Lei To: Holger =?iso-8859-1?Q?Hoffst=E4tte?= Cc: linux-block@vger.kernel.org, linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] SCSI: delay run queue if device is blocked in scsi_dev_queue_ready() Message-ID: <20171205065641.GC9989@ming.t460p> References: <20171202163150.1273-1-ming.lei@redhat.com> <1512400159.23838.1.camel@wdc.com> <20171204224507.GB6888@ming.t460p> <20171205051624.GB9989@ming.t460p> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20171205051624.GB9989@ming.t460p> User-Agent: Mutt/1.9.1 (2017-09-22) X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.29]); Tue, 05 Dec 2017 06:57:00 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Dec 05, 2017 at 01:16:24PM +0800, Ming Lei wrote: > On Mon, Dec 04, 2017 at 11:48:07PM +0000, Holger Hoffstätte wrote: > > On Tue, 05 Dec 2017 06:45:08 +0800, Ming Lei wrote: > > > > > On Mon, Dec 04, 2017 at 03:09:20PM +0000, Bart Van Assche wrote: > > >> On Sun, 2017-12-03 at 00:31 +0800, Ming Lei wrote: > > >> > Fixes: 0df21c86bdbf ("scsi: implement .get_budget and .put_budget for blk-mq") > > >> > > >> It might be safer to revert commit 0df21c86bdbf instead of trying to fix all > > >> issues introduced by that commit for kernel version v4.15 ... > > > > > > What are all issues in v4.15-rc? Up to now, it is the only issue reported, > > > and can be fixed by this simple patch, which one can be thought as cleanup > > > too. > > > > Even with this patch I've encountered at least one hang that > > seemed related. I'm using most of block/scsi-4.15 on top of 4.14 and > > the hang in question was on a rotating disk. It could be solved by activating > > a different scheduler on the hanging device; all hanging sync/df processes got > > unstuck and all was fine again, which leads me to believe that there is at least > > one more rare condition where delaying requests (as done in the budget patch) > > leads to a hang. > > > > This happened with mq-deadline which I was testing specifically to avoid > > any BFQ-related side effects. > > OK, this looks a new report. > > Without any log, we can't make any progress, and even we can't guess > what the issue is related with. > > Could you post your dmesg log(include the hang process stack trace)? And > dump the debugfs log by the following script when this hang happens? > > http://people.redhat.com/minlei/tests/tools/dump-blk-info > > BTW, you just need to pass the disk name to the script, such as: /dev/sda. Thinking of the issue further, this patch only covers case of scsi_set_blocked(), but don't consider the case in which .get_budget() is called inside blk_mq_dispatch_rq_list() for request coming from hctx->dispatch_list. If .get_budget() is called in both blk_mq_do_dispatch_sched() and blk_mq_do_dispatch_ctx(), we don't need to run queue if the queue is idle. But if it is called from blk_mq_dispatch_rq_list() for request coming from hctx->dispatch_list, we have to run queue if queue is idle, as before. So please ignore this patch, and will submit V2 for cover both cases. Thanks, Ming