ceph: fix use after free on mds __unregister_request

There was a use after free in __unregister_request that would trigger
whenever the request map held the last reference.  This appears to have
triggered an oops during 'umount -f' when requests are being torn down.

Signed-off-by: Sage Weil <sage@newdream.net>

1 files changed, 2 insertions, 1 deletions

diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c
index 5268d404963c..5c7920be6420 100644
--- a/fs/ceph/mds_client.c
+++ b/fs/ceph/mds_client.c
@@ -532,7 +532,6 @@ static void __unregister_request(struct ceph_mds_client *mdsc,
         dout("__unregister_request %p tid %lld\n", req, req->r_tid);
         rb_erase(&req->r_node, &mdsc->request_tree);
         RB_CLEAR_NODE(&req->r_node);
-        ceph_mdsc_put_request(req);
 
         if (req->r_unsafe_dir) {
                 struct ceph_inode_info *ci = ceph_inode(req->r_unsafe_dir);
@@ -541,6 +540,8 @@ static void __unregister_request(struct ceph_mds_client *mdsc,
                 list_del_init(&req->r_unsafe_dir_item);
                 spin_unlock(&ci->i_unsafe_lock);
         }
+
+        ceph_mdsc_put_request(req);
 }
 
 /*