diff --git i/src/include/storage/bufmgr.h w/src/include/storage/bufmgr.h
index 6ab00daa2ea..e5788309c86 100644
--- i/src/include/storage/bufmgr.h
+++ w/src/include/storage/bufmgr.h
@@ -223,6 +223,7 @@ extern void DropRelationBuffers(struct SMgrRelationData *smgr_reln,
 extern void DropRelationsAllBuffers(struct SMgrRelationData **smgr_reln,
 									int nlocators);
 extern void DropDatabaseBuffers(Oid dbid);
+extern void LimitAdditionalPins(uint32 *additional_pins);
 
 #define RelationGetNumberOfBlocks(reln) \
 	RelationGetNumberOfBlocksInFork(reln, MAIN_FORKNUM)
diff --git i/src/backend/access/transam/xloginsert.c w/src/backend/access/transam/xloginsert.c
index e2a5a3d13ba..2189fc9f71f 100644
--- i/src/backend/access/transam/xloginsert.c
+++ w/src/backend/access/transam/xloginsert.c
@@ -1268,8 +1268,8 @@ log_newpage_range(Relation rel, ForkNumber forknum,
 
 	/*
 	 * Iterate over all the pages in the range. They are collected into
-	 * batches of XLR_MAX_BLOCK_ID pages, and a single WAL-record is written
-	 * for each batch.
+	 * batches of up to XLR_MAX_BLOCK_ID pages, and a single WAL-record is
+	 * written for each batch.
 	 */
 	XLogEnsureRecordSpace(XLR_MAX_BLOCK_ID - 1, 0);
 
@@ -1278,14 +1278,18 @@ log_newpage_range(Relation rel, ForkNumber forknum,
 	{
 		Buffer		bufpack[XLR_MAX_BLOCK_ID];
 		XLogRecPtr	recptr;
-		int			nbufs;
+		uint32		limit = XLR_MAX_BLOCK_ID;
+		int		nbufs;
 		int			i;
 
 		CHECK_FOR_INTERRUPTS();
 
+		/* avoid running out pinnable buffers */
+		LimitAdditionalPins(&limit);
+
 		/* Collect a batch of blocks. */
 		nbufs = 0;
-		while (nbufs < XLR_MAX_BLOCK_ID && blkno < endblk)
+		while (nbufs < limit && blkno < endblk)
 		{
 			Buffer		buf = ReadBufferExtended(rel, forknum, blkno,
 												 RBM_NORMAL, NULL);
diff --git i/src/backend/storage/buffer/bufmgr.c w/src/backend/storage/buffer/bufmgr.c
index 7778dde3e57..31c75d6240e 100644
--- i/src/backend/storage/buffer/bufmgr.c
+++ w/src/backend/storage/buffer/bufmgr.c
@@ -1742,7 +1742,7 @@ again:
  * pessimistic, but outside of toy-sized shared_buffers it should allow
  * sufficient pins.
  */
-static void
+void
 LimitAdditionalPins(uint32 *additional_pins)
 {
 	uint32		max_backends;
diff --git i/src/test/modules/test_misc/t/004_io_direct.pl w/src/test/modules/test_misc/t/004_io_direct.pl
index f5bf0b11e4e..5791c2ab7bd 100644
--- i/src/test/modules/test_misc/t/004_io_direct.pl
+++ w/src/test/modules/test_misc/t/004_io_direct.pl
@@ -22,7 +22,7 @@ $node->init;
 $node->append_conf(
 	'postgresql.conf', qq{
 io_direct = 'data,wal,wal_init'
-shared_buffers = '256kB' # tiny to force I/O
+shared_buffers = '16' # tiny to force I/O
 });
 $node->start;