drbd: move invalidating the whole bitmap out of after_state ch()

To avoid other state change requests, after passing through
sanitize_state(), to be mistaken for an invalidate,
move the "set all bits as out-of-sync" into the invalidate path.

Make invalidate and invalidate-remote behave consistently wrt.
current connection state (need either an established replication link,
or really be disconnected). Also mention that in the documentation.

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>
diff --git a/drivers/block/drbd/drbd_nl.c b/drivers/block/drbd/drbd_nl.c
index 42fda4a..c49bda7 100644
--- a/drivers/block/drbd/drbd_nl.c
+++ b/drivers/block/drbd/drbd_nl.c
@@ -2448,19 +2448,23 @@
 
 	retcode = _drbd_request_state(mdev, NS(conn, C_STARTING_SYNC_T), CS_ORDERED);
 
-	if (retcode < SS_SUCCESS && retcode != SS_NEED_CONNECTION)
-		retcode = drbd_request_state(mdev, NS(conn, C_STARTING_SYNC_T));
-
-	while (retcode == SS_NEED_CONNECTION) {
-		spin_lock_irq(&mdev->tconn->req_lock);
-		if (mdev->state.conn < C_CONNECTED)
-			retcode = _drbd_set_state(_NS(mdev, disk, D_INCONSISTENT), CS_VERBOSE, NULL);
-		spin_unlock_irq(&mdev->tconn->req_lock);
-
-		if (retcode != SS_NEED_CONNECTION)
-			break;
-
-		retcode = drbd_request_state(mdev, NS(conn, C_STARTING_SYNC_T));
+	/* If that did not work, try again,
+	 * but log failures this time (implicit CS_VERBOSE).
+	 *
+	 * If we happen to be C_STANDALONE R_SECONDARY,
+	 * just change to D_INCONSISTENT, and set all bits in the bitmap.
+	 * Otherwise, we just fail, to avoid races with the resync handshake.
+	 */
+	if (retcode < SS_SUCCESS) {
+		if (mdev->state.conn == C_STANDALONE && mdev->state.role == R_SECONDARY) {
+			retcode = drbd_request_state(mdev, NS(disk, D_INCONSISTENT));
+			if (retcode >= SS_SUCCESS) {
+				if (drbd_bitmap_io(mdev, &drbd_bmio_set_n_write,
+					"set_n_write from invalidate", BM_LOCKED_MASK))
+					retcode = ERR_IO_MD_DISK;
+			}
+		} else
+			retcode = drbd_request_state(mdev, NS(conn, C_STARTING_SYNC_T));
 	}
 	drbd_resume_io(mdev);
 
@@ -2517,9 +2521,9 @@
 
 	retcode = _drbd_request_state(mdev, NS(conn, C_STARTING_SYNC_S), CS_ORDERED);
 	if (retcode < SS_SUCCESS) {
-		if (retcode == SS_NEED_CONNECTION && mdev->state.role == R_PRIMARY) {
-			/* The peer will get a resync upon connect anyways.
-			 * Just make that into a full resync. */
+		if (mdev->state.conn == C_STANDALONE && mdev->state.role == R_PRIMARY) {
+			/* The peer will get a resync upon connect anyways. Just make that
+			   into a full resync. */
 			retcode = drbd_request_state(mdev, NS(pdsk, D_INCONSISTENT));
 			if (retcode >= SS_SUCCESS) {
 				if (drbd_bitmap_io(mdev, &drbd_bmio_set_susp_al,