NFS: Fix use after free in write error path

Signed-off-by: Fred Isaman <fred.isaman@gmail.com>
Fixes: 0bcbf039f6b2b ("nfs: handle request add failure properly")
Cc: stable@vger.kernel.org # v4.5+
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
diff --git a/fs/nfs/write.c b/fs/nfs/write.c
index bdfe5a7..e0bccbe 100644
--- a/fs/nfs/write.c
+++ b/fs/nfs/write.c
@@ -561,9 +561,9 @@
 {
 	nfs_unlock_request(req);
 	nfs_end_page_writeback(req);
-	nfs_release_request(req);
 	generic_error_remove_page(page_file_mapping(req->wb_page),
 				  req->wb_page);
+	nfs_release_request(req);
 }
 
 /*