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[PATCH 12/19] drbd: don't block forever in disconnect during resync if fencing=r-a-stonith

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From	Philipp Reisner <philipp.reisner@linbit.com>
Newsgroups	linux.kernel
Subject	[PATCH 12/19] drbd: don't block forever in disconnect during resync if fencing=r-a-stonith
Date	Tue, 04 Aug 2015 15:00:04 +0200
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From: Lars Ellenberg <lars.ellenberg@linbit.com>

Disconnect should wait for pending bitmap IO.
But if that bitmap IO is not happening, because it is waiting for
pending application IO, and there is no progress, because the fencing
policy suspended application IO because of the disconnect,
then we deadlock.

The bitmap writeout in this case does not care for concurrent
application IO, so there is no point waiting for it.

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
---
 drivers/block/drbd/drbd_main.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/block/drbd/drbd_main.c b/drivers/block/drbd/drbd_main.c
index fea97fe..d26ddb6 100644
--- a/drivers/block/drbd/drbd_main.c
+++ b/drivers/block/drbd/drbd_main.c
@@ -3564,7 +3564,9 @@ void drbd_queue_bitmap_io(struct drbd_device *device,
 
 	spin_lock_irq(&device->resource->req_lock);
 	set_bit(BITMAP_IO, &device->flags);
-	if (atomic_read(&device->ap_bio_cnt) == 0) {
+	/* don't wait for pending application IO if the caller indicates that
+	 * application IO does not conflict anyways. */
+	if (flags == BM_LOCKED_CHANGE_ALLOWED || atomic_read(&device->ap_bio_cnt) == 0) {
 		if (!test_and_set_bit(BITMAP_IO_QUEUED, &device->flags))
 			drbd_queue_work(&first_peer_device(device)->connection->sender_work,
 					&device->bm_io_work.w);
-- 
1.9.1

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[PATCH 12/19] drbd: don't block forever in disconnect during resync if fencing=r-a-stonith Philipp Reisner <philipp.reisner@linbit.com> - 2015-08-04 15:00 +0200

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