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Commit 607f25e5 authored by Lars Ellenberg's avatar Lars Ellenberg Committed by Jens Axboe
Browse files

drbd: fix drbd epoch write count for ahead/behind mode 



The sanity check when receiving P_BARRIER_ACK does expect all write
requests with a given req->epoch to have been either all replicated,
or all not replicated.

Because req->epoch was assigned before calling maybe_pull_ahead(),
this expectation was not met, leading to an off-by-one in the sanity
check, and further to a "Protocol Error".

Fix: move the call to maybe_pull_ahead() a few lines up,
and assign req->epoch only after that.

Signed-off-by: default avatarPhilipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: default avatarLars Ellenberg <lars.ellenberg@linbit.com>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent ef57f9e6

drivers/block/drbd/drbd_req.c

+7 −7
Original line number Diff line number Diff line
@@ -865,8 +865,10 @@ static void maybe_pull_ahead(struct drbd_conf *mdev) 
	bool congested = false;

	enum drbd_on_congestion on_congestion;



	rcu_read_lock();

	nc = rcu_dereference(tconn->net_conf);

	on_congestion = nc ? nc->on_congestion : OC_BLOCK;

	rcu_read_unlock();

	if (on_congestion == OC_BLOCK ||

	    tconn->agreed_pro_version < 96)

		return;
@@ -960,14 +962,8 @@ static int drbd_process_write_request(struct drbd_request *req) 
	struct drbd_conf *mdev = req->w.mdev;

	int remote, send_oos;



	rcu_read_lock();

	remote = drbd_should_do_remote(mdev->state);

	if (remote) {

		maybe_pull_ahead(mdev);

	remote = drbd_should_do_remote(mdev->state);

	}

	send_oos = drbd_should_send_out_of_sync(mdev->state);

	rcu_read_unlock();



	/* Need to replicate writes.  Unless it is an empty flush,

	 * which is better mapped to a DRBD P_BARRIER packet,
@@ -1087,9 +1083,13 @@ static void drbd_send_and_submit(struct drbd_conf *mdev, struct drbd_request *re 
		 * but will re-aquire it before it returns here.

		 * Needs to be before the check on drbd_suspended() */

		complete_conflicting_writes(req);

		/* no more giving up req_lock from now on! */



		/* check for congestion, and potentially stop sending

		 * full data updates, but start sending "dirty bits" only. */

		maybe_pull_ahead(mdev);

	}



	/* no more giving up req_lock from now on! */



	if (drbd_suspended(mdev)) {

		/* push back and retry: */