Thanks for the report.
I'm having trouble figuring out why this ever worked. I must be
missing something.
I can only reproduce a hang when calling reboot when a sync is needed.
I dirty a file and then
reboot -f -n
This will always have blocked except between the commit that you
mention and an earlier commit which broke something which that commit
was fixing.
This is because the reboot calls do_md_stop while holding the mddev
lock, and do_md_stop calls invalidate_partition. If this finds any dirty
data to flush, the writeout will (most likely) need to mark the
superblock as dirty first, which cannot happen while the mddev lock is
held. So we get a deadlock.
The call to invalidate_partition should not be needed in any case except a
reboot, and in that case you really don't want it (if you wanted to
sync, you would have done that first).
So I plan to remove it. With it gone I cannot reproduce a hang. If
you can, I would love to hear about it.
Thanks,
NeilBrown
diff --git a/drivers/md/md.c b/drivers/md/md.c
index 8cfadc5..4790c83 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -3841,8 +3841,6 @@ static int do_md_stop(mddev_t * mddev, int mode, int is_open)
del_timer_sync(&mddev->safemode_timer);
- invalidate_partition(disk, 0);
-
switch(mode) {
case 1: /* readonly */
err = -ENXIO;
--
