gfs2: Do proper error checking for go_sync family of glops functions

Before this patch, function do_xmote would try to sync out the glock
dirty data by calling the appropriate glops function XXX_go_sync()
but it did not check for a good return code. If the sync was not
possible due to an io error or whatever, do_xmote would continue on
and call go_inval and release the glock to other cluster nodes.
When those nodes go to replay the journal, they may already be holding
glocks for the journal records that should have been synced, but were
not due to the ignored error.

This patch introduces proper error code checking to the go_sync
family of glops functions.

Signed-off-by: Bob Peterson <rpeterso@redhat.com>
Reviewed-by: Andreas Gruenbacher <agruenba@redhat.com>
diff --git a/fs/gfs2/incore.h b/fs/gfs2/incore.h
index 8cd564b..04549a8 100644
--- a/fs/gfs2/incore.h
+++ b/fs/gfs2/incore.h
@@ -234,7 +234,7 @@ struct lm_lockname {
 
 
 struct gfs2_glock_operations {
-	void (*go_sync) (struct gfs2_glock *gl);
+	int (*go_sync) (struct gfs2_glock *gl);
 	int (*go_xmote_bh) (struct gfs2_glock *gl, struct gfs2_holder *gh);
 	void (*go_inval) (struct gfs2_glock *gl, int flags);
 	int (*go_demote_ok) (const struct gfs2_glock *gl);