diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c
index adeb9512a70..ad0f2a109a6 100644
--- a/contrib/pg_visibility/pg_visibility.c
+++ b/contrib/pg_visibility/pg_visibility.c
@@ -421,7 +421,7 @@ 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->delayChkptFlags &= ~(DELAY_CHKPT_START | DELAY_CHKPT_COMPLETE);
diff --git a/src/backend/catalog/storage.c b/src/backend/catalog/storage.c
index e42c79f05b9..53ebf093285 100644
--- a/src/backend/catalog/storage.c
+++ b/src/backend/catalog/storage.c
@@ -418,7 +418,7 @@ 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();
 
@@ -1059,7 +1059,7 @@ 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 e6cc0f1a224..67ec3b55983 100644
--- a/src/backend/storage/smgr/smgr.c
+++ b/src/backend/storage/smgr/smgr.c
@@ -692,6 +692,26 @@ smgrnblocks_cached(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
@@ -703,8 +723,8 @@ smgrnblocks_cached(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 3f07099201d..55fce3fa04a 100644
--- a/src/include/storage/smgr.h
+++ b/src/include/storage/smgr.h
@@ -151,8 +151,10 @@ extern void smgrwriteback(SMgrRelation reln, ForkNumber forknum,
 extern BlockNumber smgrnblocks(SMgrRelation reln, ForkNumber forknum);
 extern BlockNumber smgrnblocks_cached(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 smgrregistersync(SMgrRelation reln, ForkNumber forknum);
 extern void AtEOXact_SMgr(void);