libceph: Avoid holding the zero page on ceph_msgr_slab_init errors

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 <benoit.canet@nodalink.com>
Reviewed-by: Alex Elder <elder@linaro.org>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

1 files changed, 5 insertions, 5 deletions

diff --git a/net/ceph/messenger.c b/net/ceph/messenger.c
index e3be1d22a247..0f9ea60a8971 100644
--- 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.