ceph: fix null pointer dereference in send_mds_reconnect()
ceph: fix null pointer dereference in send_mds_reconnect()

sb->s_root can be null when umounting

Signed-off-by: Yan, Zheng <5a3288024fcad83740d827e0862f4c1e6f28e7bf@redhat.com>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs