diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c
index 5acf2cfbad2..ee2078b906f 100644
--- a/contrib/pg_visibility/pg_visibility.c
+++ b/contrib/pg_visibility/pg_visibility.c
@@ -429,7 +429,7 @@ pg_truncate_visibility_map(PG_FUNCTION_ARGS)
 	}
 
 	if (BlockNumberIsValid(block))
-		smgrtruncate(RelationGetSmgr(rel), &fork, 1, &old_block, &block);
+		smgrtruncate2(RelationGetSmgr(rel), &fork, 1, &old_block, &block);
 
 	END_CRIT_SECTION();
 	MyProc->delayChkpt = false;
diff --git a/src/backend/catalog/storage.c b/src/backend/catalog/storage.c
index 7550fc1accf..8ef485d84ae 100644
--- a/src/backend/catalog/storage.c
+++ b/src/backend/catalog/storage.c
@@ -409,7 +409,7 @@ RelationTruncate(Relation rel, BlockNumber nblocks)
 	 * longer exist after truncation is complete, and then truncate the
 	 * corresponding files on disk.
 	 */
-	smgrtruncate(RelationGetSmgr(rel), forks, nforks, old_blocks, blocks);
+	smgrtruncate2(RelationGetSmgr(rel), forks, nforks, old_blocks, blocks);
 
 	END_CRIT_SECTION();
 
@@ -1070,7 +1070,7 @@ smgr_redo(XLogReaderState *record)
 		if (nforks > 0)
 		{
 			START_CRIT_SECTION();
-			smgrtruncate(reln, forks, nforks, old_blocks, blocks);
+			smgrtruncate2(reln, forks, nforks, old_blocks, blocks);
 			END_CRIT_SECTION();
 		}
 
diff --git a/src/backend/storage/smgr/smgr.c b/src/backend/storage/smgr/smgr.c
index fc0516c1eb0..d33db9c4b38 100644
--- a/src/backend/storage/smgr/smgr.c
+++ b/src/backend/storage/smgr/smgr.c
@@ -544,6 +544,26 @@ smgrnblocks(SMgrRelation reln, ForkNumber forknum)
  *	smgrtruncate() -- Truncate the given forks of supplied relation to
  *					  each specified numbers of blocks
  *
+ * Backward-compatible version of smgrtruncate2() for the benefit of external
+ * callers.  This version isn't used in PostgreSQL core code, and can't be
+ * used in a critical section.
+ */
+void
+smgrtruncate(SMgrRelation reln, ForkNumber *forknum, int nforks,
+			 BlockNumber *nblocks)
+{
+	BlockNumber old_nblocks[MAX_FORKNUM + 1];
+
+	for (int i = 0; i < nforks; ++i)
+		old_nblocks[i] = smgrnblocks(reln, forknum[i]);
+
+	return smgrtruncate2(reln, forknum, nforks, old_nblocks, nblocks);
+}
+
+/*
+ * smgrtruncate2() -- Truncate the given forks of supplied relation to
+ *					  each specified numbers of blocks
+ *
  * The truncation is done immediately, so this can't be rolled back.
  *
  * The caller must hold AccessExclusiveLock on the relation, to ensure that
@@ -555,8 +575,8 @@ smgrnblocks(SMgrRelation reln, ForkNumber forknum)
  * to this relation should be called in between.
  */
 void
-smgrtruncate(SMgrRelation reln, ForkNumber *forknum, int nforks,
-			 BlockNumber *old_nblocks, BlockNumber *nblocks)
+smgrtruncate2(SMgrRelation reln, ForkNumber *forknum, int nforks,
+			  BlockNumber *old_nblocks, BlockNumber *nblocks)
 {
 	int			i;
 
diff --git a/src/include/storage/smgr.h b/src/include/storage/smgr.h
index 147ec330f80..92020305e54 100644
--- a/src/include/storage/smgr.h
+++ b/src/include/storage/smgr.h
@@ -102,8 +102,10 @@ extern void smgrwriteback(SMgrRelation reln, ForkNumber forknum,
 						  BlockNumber blocknum, BlockNumber nblocks);
 extern BlockNumber smgrnblocks(SMgrRelation reln, ForkNumber forknum);
 extern void smgrtruncate(SMgrRelation reln, ForkNumber *forknum, int nforks,
-						 BlockNumber *old_nblocks,
 						 BlockNumber *nblocks);
+extern void smgrtruncate2(SMgrRelation reln, ForkNumber *forknum, int nforks,
+						  BlockNumber *old_nblocks,
+						  BlockNumber *nblocks);
 extern void smgrimmedsync(SMgrRelation reln, ForkNumber forknum);
 extern void AtEOXact_SMgr(void);