ceph: flush msgr_wq during mds_client shutdown

The release method for mds connections uses a backpointer to the
mds_client, so we need to flush the workqueue of any pending work (and
ceph_connection references) prior to freeing the mds_client.  This fixes
an oops easily triggered under UML by

 while true ; do mount ... ; umount ... ; done

Also fix an outdated comment: the flush in ceph_destroy_client only flushes
OSD connections out.  This bug is basically an artifact of the ceph ->
ceph+libceph conversion.

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

2 files changed, 8 insertions, 2 deletions

diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c
index a1ee8fa3a8e..f60b07b0feb 100644
--- a/fs/ceph/mds_client.c
+++ b/fs/ceph/mds_client.c
@@ -3215,9 +3215,15 @@ void ceph_mdsc_destroy(struct ceph_fs_client *fsc)
 {
         struct ceph_mds_client *mdsc = fsc->mdsc;
 
+        dout("mdsc_destroy %p\n", mdsc);
         ceph_mdsc_stop(mdsc);
+
+        /* flush out any connection work with references to us */
+        ceph_msgr_flush();
+
         fsc->mdsc = NULL;
         kfree(mdsc);
+        dout("mdsc_destroy %p done\n", mdsc);
 }
 
 
diff --git a/net/ceph/ceph_common.c b/net/ceph/ceph_common.c
index 95f96ab94bb..9bbb356b12e 100644
--- a/net/ceph/ceph_common.c
+++ b/net/ceph/ceph_common.c
@@ -394,8 +394,8 @@ void ceph_destroy_client(struct ceph_client *client)
         ceph_osdc_stop(&client->osdc);
 
         /*
-         * make sure mds and osd connections close out before destroying
-         * the auth module, which is needed to free those connections'
+         * make sure osd connections close out before destroying the
+         * auth module, which is needed to free those connections'
          * ceph_authorizers.
          */
         ceph_msgr_flush();