drbd: Starting with protocol 96 we can allow app-IO while receiving the bitmap

* C_STARTING_SYNC_S, C_STARTING_SYNC_T In these states the bitmap gets
  written to disk. Locking out of app-IO is done by using the
  drbd_queue_bitmap_io() and drbd_bitmap_io() functions these days.
  It is no longer necessary to lock out app-IO based on the connection
  state.
  App-IO that may come in after the BITMAP_IO flag got cleared before the
  state transition to C_SYNC_(SOURCE|TARGET) does not get mirrored, sets
  a bit in the local bitmap, that is already set, therefore changes nothing.

* C_WF_BITMAP_S In this state we send updates (P_OUT_OF_SYNC packets).
  With that we make sure they have the same number of bits when going
  into the C_SYNC_(SOURCE|TARGET) connection state.

* C_UNCONNECTED: The receiver starts, no need to lock out IO.

* C_DISCONNECTING: in drbd_disconnect() we had a wait_event()
  to wait until ap_bio_cnt reaches 0. Removed that.

* C_TIMEOUT, C_BROKEN_PIPE, C_NETWORK_FAILURE
  C_PROTOCOL_ERROR, C_TEAR_DOWN: Same as C_DISCONNECTING

* C_WF_REPORT_PARAMS: IO still possible since that is still
  like C_WF_CONNECTION.

And we do not need to send barriers in C_WF_BITMAP_S connection state.

Allow concurrent accesses to the bitmap when receiving the bitmap.
Everything gets ORed anyways.

A drbd_free_tl_hash() is in after_state_chg_work(). At that point
all the work items of the last connections must have been processed.

Introduced a call to drbd_free_tl_hash() into drbd_free_mdev()
for paranoia reasons.

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>

1 files changed, 12 insertions, 7 deletions

diff --git a/drivers/block/drbd/drbd_int.h b/drivers/block/drbd/drbd_int.h
index 9a944604939f..38bbaba8bd89 100644
--- a/drivers/block/drbd/drbd_int.h
+++ b/drivers/block/drbd/drbd_int.h
@@ -2213,8 +2213,9 @@ static inline int drbd_get_max_buffers(struct drbd_conf *mdev)
 	return mxb;
 }
 
-static inline int drbd_state_is_stable(union drbd_state s)
+static inline int drbd_state_is_stable(struct drbd_conf *mdev)
 {
+	union drbd_state s = mdev->state;
 
 	/* DO NOT add a default clause, we want the compiler to warn us
 	 * for any newly introduced state we may have forgotten to add here */
@@ -2233,11 +2234,7 @@ static inline int drbd_state_is_stable(union drbd_state s)
 	case C_PAUSED_SYNC_T:
 	case C_AHEAD:
 	case C_BEHIND:
-		/* maybe stable, look at the disk state */
-		break;
-
-	/* no new io accepted during tansitional states
-	 * like handshake or teardown */
+		/* transitional states, IO allowed */
 	case C_DISCONNECTING:
 	case C_UNCONNECTED:
 	case C_TIMEOUT:
@@ -2248,7 +2245,15 @@ static inline int drbd_state_is_stable(union drbd_state s)
 	case C_WF_REPORT_PARAMS:
 	case C_STARTING_SYNC_S:
 	case C_STARTING_SYNC_T:
+		break;
+
+		/* Allow IO in BM exchange states with new protocols */
 	case C_WF_BITMAP_S:
+		if (mdev->agreed_pro_version < 96)
+			return 0;
+		break;
+
+		/* no new io accepted in these states */
 	case C_WF_BITMAP_T:
 	case C_WF_SYNC_UUID:
 	case C_MASK:
@@ -2297,7 +2302,7 @@ static inline int __inc_ap_bio_cond(struct drbd_conf *mdev)
 	 * to start during "stable" states. */
 
 	/* no new io accepted when attaching or detaching the disk */
-	if (!drbd_state_is_stable(mdev->state))
+	if (!drbd_state_is_stable(mdev))
 		return 0;
 
 	/* since some older kernels don't have atomic_add_unless,