RDS: Do not call set_page_dirty() with irqs off

set_page_dirty() unconditionally re-enables interrupts, so
if we call it with irqs off, they will be on after the call,
and that's bad. This patch moves the call after we've re-enabled
interrupts in send_drop_to(), so it's safe.

Also, add BUG_ONs to let us know if we ever do call set_page_dirty
with interrupts off.

Signed-off-by: Andy Grover <andy.grover@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/rds/rdma.c b/net/rds/rdma.c
index 4c64daa..61b359d 100644
--- a/net/rds/rdma.c
+++ b/net/rds/rdma.c
@@ -438,8 +438,10 @@
 		/* Mark page dirty if it was possibly modified, which
 		 * is the case for a RDMA_READ which copies from remote
 		 * to local memory */
-		if (!ro->r_write)
+		if (!ro->r_write) {
+			BUG_ON(in_interrupt());
 			set_page_dirty(page);
+		}
 		put_page(page);
 	}