[walproposer] [contrib/zenith] [refer neondatabase#395] Do no align s…

…art replication position in wal_proppser to segment boundary

contrib/zenith/pagestore_smgr.c

@@ -21,6 +21,7 @@
 #include "storage/relfilenode.h"
 #include "storage/smgr.h"
 #include "access/xlogdefs.h"
+#include "postmaster/interrupt.h"
 #include "storage/bufmgr.h"
 #include "fmgr.h"
 #include "miscadmin.h"
@@ -243,6 +244,9 @@ zenith_wallog_page(SMgrRelation reln, ForkNumber forknum, BlockNumber blocknum,
 {
 	XLogRecPtr lsn = PageGetLSN(buffer);
 
+	if (ShutdownRequestPending)
+		return;
+
 	/*
 	 * If the page was not WAL-logged before eviction then we can lose its modification.
 	 * PD_WAL_LOGGED bit is used to mark pages which are wal-logged.