Check page checksums for all pages of remote delta backup

src/data.c

@@ -266,14 +266,22 @@ read_page_from_file(pgFile *file, BlockNumber blknum,
 	}
 
 	/* Verify checksum */
-	if (current.checksum_version && read_len == BLCKSZ)
+	if (current.checksum_version)
 	{
+		BlockNumber blkno = file->segno * RELSEG_SIZE + blknum;
+		uint16 page_crc = read_len == BLCKSZ
+			? pg_checksum_page(page, blkno)
+			/*
+			 * Recompute Cpage checksum calculated by agent with blkno=0
+			 * pg_checksum_page is calculating it in this way:
+			 * (((checksum ^ blkno) % 65535) + 1)
+			 */
+			: (uint16)(((*(uint16*)((PageHeader)page)->pd_linp - 1) ^ blkno) + 1);
 		/*
 		 * If checksum is wrong, sleep a bit and then try again
 		 * several times. If it didn't help, throw error
 		 */
-		if (pg_checksum_page(page, file->segno * RELSEG_SIZE + blknum)
+		if (page_crc != ((PageHeader) page)->pd_checksum)
-			!= ((PageHeader) page)->pd_checksum)
 		{
 			elog(WARNING, "File: %s blknum %u have wrong checksum, try again",
 						   file->path, blknum);

src/pg_probackup.c

@@ -338,8 +338,13 @@ main(int argc, char *argv[])
 	}
 	canonicalize_path(backup_path);
 
+	MyLocation = IsSshProtocol()
+		? backup_subcmd == ARCHIVE_PUSH_CMD
+		   ? FIO_DB_HOST : FIO_BACKUP_HOST
+		: FIO_LOCAL_HOST;
+
 	/* Ensure that backup_path is a path to a directory */
-	rc = stat(backup_path, &stat_buf);
+	rc = fio_stat(backup_path, &stat_buf, true, FIO_BACKUP_HOST);
 	if (rc != -1 && !S_ISDIR(stat_buf.st_mode))
 		elog(ERROR, "-B, --backup-path must be a path to directory");
 
@@ -356,11 +361,6 @@ main(int argc, char *argv[])
 			elog(ERROR, "required parameter not specified: --instance");
 	}
 
-	MyLocation = IsSshProtocol()
-		? backup_subcmd == ARCHIVE_PUSH_CMD
-		   ? FIO_DB_HOST : FIO_BACKUP_HOST
-		: FIO_LOCAL_HOST;
-
 	/*
 	 * If --instance option was passed, construct paths for backup data and
 	 * xlog files of this backup instance.
@@ -378,7 +378,7 @@ main(int argc, char *argv[])
 		 */
 		if (backup_subcmd != INIT_CMD && backup_subcmd != ADD_INSTANCE_CMD)
 		{
-			if (access(backup_instance_path, F_OK) != 0)
+			if (fio_access(backup_instance_path, F_OK, FIO_BACKUP_HOST) != 0)
 				elog(ERROR, "Instance '%s' does not exist in this backup catalog",
 							instance_name);
 		}

src/utils/file.c

@@ -4,6 +4,7 @@
 #include <sys/stat.h>
 
 #include "pg_probackup.h"
+#include "storage/checksum.h"
 #include "file.h"
 
 #define PRINTF_BUF_SIZE  1024
@@ -884,9 +885,12 @@ void fio_communicate(int in, int out)
 				? PageXLogRecPtrGet(((PageHeader)buf)->pd_lsn) < horizon_lsn /* For non-delta backup horizon_lsn == 0, so this condition is always false */
 				  ? sizeof(PageHeaderData) : BLCKSZ
 				: 0;
-			IO_CHECK(fio_write_all(out, &hdr, sizeof(hdr)),  sizeof(hdr));
+			if (hdr.size == sizeof(PageHeaderData))
+				/* calculate checksum without XOR-ing with block number to compare it with page CRC at master */
+				*(int16*)((PageHeader)buf)->pd_linp = pg_checksum_page(buf, 0);
+			IO_CHECK(fio_write_all(out, &hdr, sizeof(hdr)), sizeof(hdr));
 			if (hdr.size != 0)
-				IO_CHECK(fio_write_all(out, buf, hdr.size),  hdr.size);
+				IO_CHECK(fio_write_all(out, buf, hdr.size), hdr.size);
 			break;
 		  case FIO_FSTAT: /* Get information about opened file */
 			hdr.size = sizeof(st);

src/utils/remote.c

@@ -52,12 +52,12 @@ static int split_options(int argc, char* argv[], int max_options, char* options)
 }
 
 static int child_pid;
-
+#if 0
 static void kill_child(void)
 {
 	kill(child_pid, SIGTERM);
 }
-
+#endif
 
 bool launch_agent(void)
 {