[PATCH 3.9-stable ]drbd: fix for deadlock when using automatic split-brain-recovery

[Jonghwan Choi <jhbird.choi@samsung.com>]

This patch looks like it should be in the 3.9-stable tree, should we apply
it?

------------------

From: "Philipp Reisner <philipp.reisner@linbit.com>"

commit 7c689e63a847316c1b2500f86891b0a574ce7e69 upstream

With an automatic after split-brain recovery policy of
"after-sb-1pri call-pri-lost-after-sb",
when trying to drbd_set_role() to R_SECONDARY,
we run into a deadlock.

This was first recognized and supposedly fixed by
2009-06-10 "Fixed a deadlock when using automatic split brain recovery when
both nodes are"
replacing drbd_set_role() with drbd_change_state() in that code-path,
but the first hunk of that patch forgets to remove the drbd_set_role().

We apparently only ever tested the "two primaries" case.

Cc: <stable@vger.kernel.org> # 3.9.x: ef57f9e6: drbd: Fix build error
Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Jonghwan Choi <jhbird.choi@samsung.com>
---
 drivers/block/drbd/drbd_receiver.c |    1 -
 1 file changed, 1 deletion(-)

diff --git a/drivers/block/drbd/drbd_receiver.c
b/drivers/block/drbd/drbd_receiver.c
index a9eccfc..5105f43 100644
--- a/drivers/block/drbd/drbd_receiver.c
+++ b/drivers/block/drbd/drbd_receiver.c
@@ -2661,7 +2661,6 @@ static int drbd_asb_recover_1p(struct drbd_conf *mdev)
__must_hold(local)
 		if (hg == -1 && mdev->state.role == R_PRIMARY) {
 			enum drbd_state_rv rv2;
 
-			drbd_set_role(mdev, R_SECONDARY, 0);
 			 /* drbd_change_state() does not sleep while in
SS_IN_TRANSIENT_STATE,
 			  * we might be here in C_WF_REPORT_PARAMS which is
transient.
 			  * we do not need to wait for the after state
change work either. */
-- 
1.7.9.5