[PATCH 1/2] nvme: fix race between removing and reseting failure

[Jens Axboe]

On 05/16/2017 07:27 PM, Ming Lei wrote:
> When one NVMe PCI device is being resetted and found reset failue,
> nvme_remove_dead_ctrl() is called to handle the failure: blk-mq hw queues
> are put into stopped first, then schedule .remove_work to release the driver.
> 
> Unfortunately if the driver is being released via sysfs store
> just before the .remove_work is run, del_gendisk() from
> nvme_remove() may hang forever because hw queues are stopped and
> the submitted writeback IOs from fsync_bdev() can't be completed at all.
> 
> This patch fixes the following issue[1][2] by moving nvme_kill_queues()
> into nvme_remove_dead_ctrl() to avoid the issue because nvme_remove()
> flushs .reset_work, and this way is reasonable and safe because
> nvme_dev_disable() has started to suspend queues and canceled requests
> already.
> 
> [1] test script
> 	fio -filename=$NVME_DISK -iodepth=1 -thread -rw=randwrite -ioengine=psync \
> 	    -bssplit=5k/10:9k/10:13k/10:17k/10:21k/10:25k/10:29k/10:33k/10:37k/10:41k/10 \
> 	    -bs_unaligned -runtime=1200 -size=-group_reporting -name=mytest -numjobs=60
> 
> 	sleep 35
> 	echo 1 > $SYSFS_NVME_PCI_PATH/rescan
> 	echo 1 > $SYSFS_NVME_PCI_PATH/reset
> 	echo 1 > $SYSFS_NVME_PCI_PATH/remove
> 	echo 1 > /sys/bus/pci/rescan

The patch looks good to me. But since you have a nice reproducer, how about
turning that into a blktests [1] test case?

[1] https://github.com/osandov/blktests

-- 
Jens Axboe