gfs2_glock_cb
void gfs2_glock_cb(struct gfs2_glock *gl, unsigned int state);
gfs2_glock_cb(gl, LM_ST_UNLOCKED);
gfs2_glock_cb(gl, LM_ST_DEFERRED);
gfs2_glock_cb(gl, LM_ST_SHARED);
gfs2_glock_cb(gl, LM_ST_UNLOCKED);
gfs2_glock_cb(gl, glmode);