From: Lars Ellenberg <lars.ellenberg@linbit.com>
Date: Fri, 3 Sep 2010 08:00:09 +0000 (+0200)
Subject: drbd: fix race on meta-data update, addendum
X-Git-Tag: v2.6.37-rc1~167^2~32
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=ee15b038164fcf19b798021762dee3cf5cbc6433;p=pandora-kernel.git

drbd: fix race on meta-data update, addendum

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>
---

Reading git-diff-tree failed