libceph: Avoid holding the zero page on ceph_msgr_slab_init errors

benoit-canet · idryomov · commit d920ff6fc7c1 · 2015-09-08T23:14:28.000+03:00
ceph_msgr_slab_init may fail due to a temporary ENOMEM.

Delay a bit the initialization of zero_page in ceph_msgr_init and
reorder its cleanup in _ceph_msgr_exit so it's done in reverse
order of setup.

BUG_ON() will not suffer to be postponed in case it is triggered.

Signed-off-by: Benoît Canet &lt;benoit.canet@nodalink.com&gt;
Reviewed-by: Alex Elder &lt;elder@linaro.org&gt;
Signed-off-by: Ilya Dryomov &lt;idryomov@gmail.com&gt;
diff --git a/net/ceph/messenger.c b/net/ceph/messenger.c
@@ -276,22 +276,22 @@ static void _ceph_msgr_exit(void)
 		ceph_msgr_wq = NULL;
 	}
 
-	ceph_msgr_slab_exit();
-
 	BUG_ON(zero_page == NULL);
 	page_cache_release(zero_page);
 	zero_page = NULL;
+
+	ceph_msgr_slab_exit();
 }
 
 int ceph_msgr_init(void)
 {
+	if (ceph_msgr_slab_init())
+		return -ENOMEM;
+
 	BUG_ON(zero_page != NULL);
 	zero_page = ZERO_PAGE(0);
 	page_cache_get(zero_page);
 
-	if (ceph_msgr_slab_init())
-		return -ENOMEM;
-
 	/*
 	 * The number of active work items is limited by the number of
 	 * connections, so leave @max_active at default.
