On Wed, Sep 27, 2017 at 03:12:47AM +0000, Bart Van Assche wrote: > On Tue, 2017-09-26 at 22:59 +0800, Ming Lei wrote: > > On Tue, Sep 26, 2017 at 02:42:07PM +0000, Bart Van Assche wrote: > > > On Tue, 2017-09-26 at 19:17 +0800, Ming Lei wrote: > > > > Just test this patch a bit and the following failure of freezing task > > > > is triggered during suspend: [ ... ] > > > > > > What kernel version did you start from and which patches were applied on > > > top of > > > that kernel? Only patch 1/7 or all seven patches? What storage > > > configuration did > > > > It is v4.14-rc1+, and top commit is 8d93c7a43157, with all your 7 patches > > applied. > > > > > you use in your test and what command(s) did you use to trigger suspend? > > > > Follows my pm test script: > > > > #!/bin/sh > > > > echo check > /sys/block/md127/md/sync_action > > > > mkfs.ext4 -F /dev/md127 > > > > mount /dev/md0 /mnt/data > > > > dd if=/dev/zero of=/mnt/data/d1.img bs=4k count=128k& > > > > echo 9 > /proc/sys/kernel/printk > > echo devices > /sys/power/pm_test > > echo mem > /sys/power/state > > > > wait > > umount /mnt/data > > > > Storage setting: > > > > sudo mdadm --create /dev/md/test /dev/sda /dev/sdb --level=1 > > --raid-devices=2 > > both /dev/sda and /dev/sdb are virtio-scsi. > > Thanks for the detailed reply. I have been able to reproduce the freeze > failure > you reported. The output of SysRq-t learned me that the md reboot notifier was > waiting for the frozen md sync thread and that this caused the freeze > failure. So > I have started testing the patch below instead of the patch at the start of > this > e-mail thread:
OK, thanks for figuring out the reason. With current linus tree, SCSI I/O is prevented from being dispatch to device during suspend by SCSI quiesce, and will be dispatched again in resume. With Safe SCSI quiesce[1], any underlying IO request will stop at blk_queue_enter() during suspend, and restart from there during resume. For other non-SCSI driver, their .suspend/.resume often handles I/O in similar way, for example, NVMe queue will be frozen in .suspend, and unfreeze in .resume. So could you explain a bit which kind of bug this patch fixes? [1] https://marc.info/?l=linux-block&m=150649136519281&w=2 -- Ming
