addendum to baa33ae4eaa4477b60af7c434c0ddd1d182c1ae7
The race:
drbd_md_sync()
if (!test_and_clear_bit(MD_DIRTY, &mdev->flags))
return;
==> RACE with drbd_md_mark_dirty() rearming the timer.
del_timer(&mdev->md_sync_timer);
Fixed by moving the del_timer before the test_and_clear_bit.
Additionally only rearm the timer in drbd_md_mark_dirty, if MD_DIRTY was
not already set, reduce the grace period from five to one second, and
add an ifdef'ed debuging aid to find code paths missing an explicit
drbd_md_sync, if any, as those are the only relevant ones for this race.
Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
ee15b03816