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Also fix an outdated comment: the flush in ceph_destroy_client only flushes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>

1 files changed, 6 insertions, 0 deletions

diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c
index a1ee8fa3a8e7..f60b07b0feb0 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);
 }