diff --git a/src/backend/storage/smgr/md.c b/src/backend/storage/smgr/md.c
index 82442db..5dae6d4 100644
--- a/src/backend/storage/smgr/md.c
+++ b/src/backend/storage/smgr/md.c
@@ -516,18 +516,10 @@ mdclose(SMgrRelation reln, ForkNumber forknum)
 	{
 		MdfdVec    *v = &reln->md_seg_fds[forknum][nopensegs - 1];
 
-		/* if not closed already */
-		if (v->mdfd_vfd >= 0)
-		{
-			FileClose(v->mdfd_vfd);
-			v->mdfd_vfd = -1;
-		}
-
+		FileClose(v->mdfd_vfd);
+		_fdvec_resize(reln, forknum, nopensegs - 1);
 		nopensegs--;
 	}
-
-	/* resize just once, avoids pointless reallocations */
-	_fdvec_resize(reln, forknum, 0);
 }
 
 /*
@@ -1047,13 +1039,15 @@ _fdvec_resize(SMgrRelation reln,
 		reln->md_seg_fds[forknum] =
 			MemoryContextAlloc(MdCxt, sizeof(MdfdVec) * nseg);
 	}
-	else
+	else if (nseg > reln->md_num_open_segs[forknum])
 	{
 		/*
 		 * It doesn't seem worthwhile complicating the code by having a more
 		 * aggressive growth strategy here; the number of segments doesn't
 		 * grow that fast, and the memory context internally will sometimes
-		 * avoid doing an actual reallocation.
+		 * avoid doing an actual reallocation.  Likewise, since the number of
+		 * segments doesn't shrink that fast, don't shrink at all.  During
+		 * mdclose(), we'll pfree the array at nseg==0.
 		 */
 		reln->md_seg_fds[forknum] =
 			repalloc(reln->md_seg_fds[forknum],