NFSv4: Fix an rcu lock leak

The intention in the original patch was to release the lock when
we put the inode, however something got screwed up.

Reported-by: Jason Yan <yanaijie@huawei.com>
Fixes: 7b410d9ce460f ("pNFS: Delay getting the layout header in..")
Cc: stable@vger.kernel.org # v4.10+
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>

fs/nfs/callback_proc.c

@@ -131,10 +131,11 @@ restart:
 			if (!inode)
 				continue;
 			if (!nfs_sb_active(inode->i_sb)) {
-				rcu_read_lock();
+				rcu_read_unlock();
 				spin_unlock(&clp->cl_lock);
 				iput(inode);
 				spin_lock(&clp->cl_lock);
+				rcu_read_lock();
 				goto restart;
 			}
 			return inode;
@@ -170,10 +171,11 @@ restart:
 			if (!inode)
 				continue;
 			if (!nfs_sb_active(inode->i_sb)) {
-				rcu_read_lock();
+				rcu_read_unlock();
 				spin_unlock(&clp->cl_lock);
 				iput(inode);
 				spin_lock(&clp->cl_lock);
+				rcu_read_lock();
 				goto restart;
 			}
 			return inode;