Re: Infiniate systemd loop when power off the machine with multiple MD RAIDs

[Song Liu <song@kernel.org>]

On Mon, Aug 21, 2023 at 8:51 PM Guoqing Jiang <guoqing.jiang@linux.dev> wrote:
>
>
>
> On 8/18/23 16:16, Mariusz Tkaczyk wrote:
> > On Wed, 16 Aug 2023 16:37:26 +0700
> > Bagas Sanjaya<bagasdotme@gmail.com>  wrote:
> >
> >> Hi,
> >>
> >> I notice a regression report on Bugzilla [1]. Quoting from it:
> >>
> >>> It needs to build at least 2 different RAIDs(eg. RAID0 and RAID10, RAID5
> >>> and RAID10) and then you will see below error repeatly(need to use serial
> >>> console to see it)
> >>>
> >>> [ 205.360738] systemd-shutdown[1]: Stopping MD devices.
> >>> [ 205.366384] systemd-shutdown[1]: sd-device-enumerator: Scan all dirs
> >>> [ 205.373327] systemd-shutdown[1]: sd-device-enumerator: Scanning /sys/bus
> >>> [ 205.380427] systemd-shutdown[1]: sd-device-enumerator: Scanning /sys/class
> >>> [ 205.388257] systemd-shutdown[1]: Stopping MD /dev/md127 (9:127).
> >>> [ 205.394880] systemd-shutdown[1]: Failed to sync MD block device
> >>> /dev/md127, ignoring: Input/output error [ 205.404975] md: md127 stopped.
> >>> [ 205.470491] systemd-shutdown[1]: Stopping MD /dev/md126 (9:126).
> >>> [ 205.770179] md: md126: resync interrupted.
> >>> [ 205.776258] md126: detected capacity change from 1900396544 to 0
> >>> [ 205.783349] md: md126 stopped.
> >>> [ 205.862258] systemd-shutdown[1]: Stopping MD /dev/md125 (9:125).
> >>> [ 205.862435] md: md126 stopped.
> >>> [ 205.868376] systemd-shutdown[1]: Failed to sync MD block device
> >>> /dev/md125, ignoring: Input/output error [ 205.872845] block device
> >>> autoloading is deprecated and will be removed. [ 205.880955] md: md125
> >>> stopped. [ 205.934349] systemd-shutdown[1]: Stopping MD /dev/md124p2
> >>> (259:7). [ 205.947707] systemd-shutdown[1]: Could not stop MD /dev/md124p2:
> >>> Device or resource busy [ 205.957004] systemd-shutdown[1]: Stopping MD
> >>> /dev/md124p1 (259:6). [ 205.964177] systemd-shutdown[1]: Could not stop MD
> >>> /dev/md124p1: Device or resource busy [ 205.973155] systemd-shutdown[1]:
> >>> Stopping MD /dev/md124 (9:124). [ 205.979789] systemd-shutdown[1]: Could
> >>> not stop MD /dev/md124: Device or resource busy [ 205.988475]
> >>> systemd-shutdown[1]: Not all MD devices stopped, 4 left.
> >> See Bugzilla for the full thread and attached full journalctl log.
> >>
> >> Anyway, I'm adding this regression to be tracked by regzbot:
> >>
> >> #regzbot introduced: 12a6caf273240a
> >> https://bugzilla.kernel.org/show_bug.cgi?id=217798  #regzbot title: systemd
> >> shutdown hang on machine with different RAID levels
> >>
> >> Thanks.
> >>
> >> [1]:https://bugzilla.kernel.org/show_bug.cgi?id=217798
> >>
> > Hello,
> > The issue is reproducible with IMSM metadata too, around 20% of reboot hangs. I
> > will try to raise the priority in the bug because it is valid high- the
> > base functionality of the system is affected.
>
> Since it it reproducible from your side, is it possible to turn the
> reproduce steps into a test case
> given the importance?
>
> I guess If all arrays are set with MD_DELETED flag, then reboot might
> hang, not sure whether
> below (maybe need to flush wq as well  before list_del) helps or not,
> just FYI.
>
> @@ -9566,8 +9566,10 @@ static int md_notify_reboot(struct notifier_block
> *this,
>
>          spin_lock(&all_mddevs_lock);
>          list_for_each_entry_safe(mddev, n, &all_mddevs, all_mddevs) {
> -               if (!mddev_get(mddev))
> +               if (!mddev_get(mddev)) {
> +                       list_del(&mddev->all_mddevs);
>                          continue;
> +               }

I am still not able to reproduce this, probably due to differences in the
timing. Maybe we only need something like:

diff --git i/drivers/md/md.c w/drivers/md/md.c
index 5c3c19b8d509..ebb529b0faf8 100644
--- i/drivers/md/md.c
+++ w/drivers/md/md.c
@@ -9619,8 +9619,10 @@ static int md_notify_reboot(struct notifier_block *this,

        spin_lock(&all_mddevs_lock);
        list_for_each_entry_safe(mddev, n, &all_mddevs, all_mddevs) {
-               if (!mddev_get(mddev))
+               if (!mddev_get(mddev)) {
+                       need_delay = 1;
                        continue;
+               }
                spin_unlock(&all_mddevs_lock);
                if (mddev_trylock(mddev)) {
                        if (mddev->pers)


Thanks,
Song