gfs2: Don't forget to complete delayed withdraw

Commit fffe9bee14 ("gfs2: Delay withdraw from atomic context")
switched from gfs2_withdraw() to gfs2_withdraw_delayed() in
gfs2_ail_error(), but failed to then check if a delayed withdraw had
occurred.  Fix that by adding the missing check in __gfs2_ail_flush(),
where the spin locks are already dropped and a withdraw is possible.

Fixes: fffe9bee14 ("gfs2: Delay withdraw from atomic context")
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>

fs/gfs2/glops.c

@@ -82,6 +82,9 @@ static void __gfs2_ail_flush(struct gfs2_glock *gl, bool fsync,
 	GLOCK_BUG_ON(gl, !fsync && atomic_read(&gl->gl_ail_count));
 	spin_unlock(&sdp->sd_ail_lock);
 	gfs2_log_unlock(sdp);
+
+	if (gfs2_withdrawing(sdp))
+		gfs2_withdraw(sdp);
 }