fixing rebase bug

src/backend/storage/smgr/md.c

@@ -1299,6 +1299,7 @@ mdregistersync(SMgrRelation reln, ForkNumber forknum)
 {
 	int			segno;
 	int			min_inactive_seg;
+	MdSMgrRelation mdreln = (MdSMgrRelation) reln;
 
 	/*
 	 * NOTE: mdnblocks makes sure we have opened all active segments, so that
@@ -1306,7 +1307,7 @@ mdregistersync(SMgrRelation reln, ForkNumber forknum)
 	 */
 	mdnblocks(reln, forknum);
 
-	min_inactive_seg = segno = reln->md_num_open_segs[forknum];
+	min_inactive_seg = segno = mdreln->md_num_open_segs[forknum];
 
 	/*
 	 * Temporarily open inactive segments, then close them after sync.  There
@@ -1314,20 +1315,20 @@ mdregistersync(SMgrRelation reln, ForkNumber forknum)
 	 * harmless.  We don't bother to clean them up and take a risk of further
 	 * trouble.  The next mdclose() will soon close them.
 	 */
-	while (_mdfd_openseg(reln, forknum, segno, 0) != NULL)
+	while (_mdfd_openseg(mdreln, forknum, segno, 0) != NULL)
 		segno++;
 
 	while (segno > 0)
 	{
-		MdfdVec    *v = &reln->md_seg_fds[forknum][segno - 1];
+		MdfdVec    *v = &mdreln->md_seg_fds[forknum][segno - 1];
 
-		register_dirty_segment(reln, forknum, v);
+		register_dirty_segment(mdreln, forknum, v);
 
 		/* Close inactive segments immediately */
 		if (segno > min_inactive_seg)
 		{
 			FileClose(v->mdfd_vfd);
-			_fdvec_resize(reln, forknum, segno - 1);
+			_fdvec_resize(mdreln, forknum, segno - 1);
 		}
 
 		segno--;