Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752561AbdLEHxN (ORCPT ); Tue, 5 Dec 2017 02:53:13 -0500 Received: from mx1.redhat.com ([209.132.183.28]:39728 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752272AbdLEHxL (ORCPT ); Tue, 5 Dec 2017 02:53:11 -0500 From: Ming Lei To: Jens Axboe , linux-block@vger.kernel.org, Christoph Hellwig , linux-scsi@vger.kernel.org, "Martin K . Petersen" , "James E . J . Bottomley" Cc: Bart Van Assche , linux-kernel@vger.kernel.org, Hannes Reinecke , =?UTF-8?q?Holger=20Hoffst=C3=A4tte?= , Ming Lei Subject: [PATCH] SCSI: run queue if SCSI device queue isn't ready and queue is idle Date: Tue, 5 Dec 2017 15:52:56 +0800 Message-Id: <20171205075256.10319-1-ming.lei@redhat.com> X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.29]); Tue, 05 Dec 2017 07:53:11 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2228 Lines: 57 Before commit 0df21c86bdbf ("scsi: implement .get_budget and .put_budget for blk-mq"), we run queue after 3ms if queue is idle and SCSI device queue isn't ready, which is done in handling BLK_STS_RESOURCE. After commit 0df21c86bdbf is introduced, queue won't be run any more under this situation. IO hang is observed when timeout happened, and this patch fixes the IO hang issue by running queue after delay in scsi_dev_queue_ready, just like non-mq. This issue can be triggered by the following script[1]. There is another issue which can be covered by running idle queue: when .get_budget() is called on request coming from hctx->dispatch_list, if one request just completes during .get_budget(), we can't depend on SCSI's restart to make progress any more. This patch fixes the race too. With this patch, we basically recover to previous behaviour(before commit 0df21c86bdbf) of handling idle queue when running out of resource. [1] script for test/verify SCSI timeout rmmod scsi_debug modprobe scsi_debug max_queue=1 DEVICE=`ls -d /sys/bus/pseudo/drivers/scsi_debug/adapter*/host*/target*/*/block/* | head -1 | xargs basename` DISK_DIR=`ls -d /sys/block/$DEVICE/device/scsi_disk/*` echo "using scsi device $DEVICE" echo "-1" >/sys/bus/pseudo/drivers/scsi_debug/every_nth echo "temporary write through" >$DISK_DIR/cache_type echo "128" >/sys/bus/pseudo/drivers/scsi_debug/opts echo none > /sys/block/$DEVICE/queue/scheduler dd if=/dev/$DEVICE of=/dev/null bs=1M iflag=direct count=1 & sleep 5 echo "0" >/sys/bus/pseudo/drivers/scsi_debug/opts wait echo "SUCCESS" Fixes: 0df21c86bdbf ("scsi: implement .get_budget and .put_budget for blk-mq") Signed-off-by: Ming Lei --- drivers/scsi/scsi_lib.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c index db9556662e27..1816dd8259b3 100644 --- a/drivers/scsi/scsi_lib.c +++ b/drivers/scsi/scsi_lib.c @@ -1967,6 +1967,8 @@ static bool scsi_mq_get_budget(struct blk_mq_hw_ctx *hctx) out_put_device: put_device(&sdev->sdev_gendev); out: + if (atomic_read(&sdev->device_busy) == 0 && !scsi_device_blocked(sdev)) + blk_mq_delay_run_hw_queue(hctx, SCSI_QUEUE_DELAY); return false; } -- 2.9.5