Hi!

On Sun, Apr 01, 2018 at 05:27:21PM +0200, Magnus Hagander wrote:
> It might be a micro-optimisation, but ISTM that we shouldn't do the
> basename(palloc(fn)) in is_heap_file() unless we actually need it -- so not
> at the top of the function. (And surely "." and ".." should not occur here?
> I think that's a result of copy/paste from the online checksum patch?
> 
> We also do exactly the same basename(palloc(fn)) in sendFile().  Can we
> find a way to reuse that duplication? Perhaps we want to split it into the
> two pieces already out in sendFile() and pass it in as separate parameters?

I've done the latter now, although it looks a bit weird that the second
argument data is a subset of the first.  I couldn't find another way to
not have it done twice, though.

> If not then this second one should at least only be done inside the if
> (verify_checksums).

We can't have both, as we need to call the is_heap_file() function in
order to determine whether we should verify the checksums. 
 
> There is a bigger problem next to that though -- I believe  basename() does
> not exist on Win32. I haven't tested it, but there is zero documentation of
> it existing, which usually indicates it doesn't. That's the part that
> definitely needs to get fixed.
> 
> I think you need to look into the functionality in port/path.c, in
> particular last_dir_separator()?

Thanks for the pointer, I've used that now; I mentioned before that
basename() might be a portability hazard, but couldn't find a good
substitute myself.

V6 of the patch is attached.


Michael

-- 
Michael Banck
Projektleiter / Senior Berater
Tel.: +49 2166 9901-171
Fax:  +49 2166 9901-100
Email: michael.ba...@credativ.de

credativ GmbH, HRB Mönchengladbach 12080
USt-ID-Nummer: DE204566209
Trompeterallee 108, 41189 Mönchengladbach
Geschäftsführung: Dr. Michael Meskes, Jörg Folz, Sascha Heuer
diff --git a/doc/src/sgml/protocol.sgml b/doc/src/sgml/protocol.sgml
index 8c488506fa..b94dd4ac65 100644
--- a/doc/src/sgml/protocol.sgml
+++ b/doc/src/sgml/protocol.sgml
@@ -2382,7 +2382,7 @@ The commands accepted in replication mode are:
   </varlistentry>
 
   <varlistentry>
-    <term><literal>BASE_BACKUP</literal> [ <literal>LABEL</literal> <replaceable>'label'</replaceable> ] [ <literal>PROGRESS</literal> ] [ <literal>FAST</literal> ] [ <literal>WAL</literal> ] [ <literal>NOWAIT</literal> ] [ <literal>MAX_RATE</literal> <replaceable>rate</replaceable> ] [ <literal>TABLESPACE_MAP</literal> ]
+    <term><literal>BASE_BACKUP</literal> [ <literal>LABEL</literal> <replaceable>'label'</replaceable> ] [ <literal>PROGRESS</literal> ] [ <literal>FAST</literal> ] [ <literal>WAL</literal> ] [ <literal>NOWAIT</literal> ] [ <literal>MAX_RATE</literal> <replaceable>rate</replaceable> ] [ <literal>TABLESPACE_MAP</literal> ] [ <literal>NOVERIFY_CHECKSUMS</literal> ]
      <indexterm><primary>BASE_BACKUP</primary></indexterm>
     </term>
     <listitem>
@@ -2481,6 +2481,17 @@ The commands accepted in replication mode are:
          </para>
         </listitem>
        </varlistentry>
+
+       <varlistentry>
+        <term><literal>NOVERIFY_CHECKSUMS</literal></term>
+        <listitem>
+         <para>
+          By default, checksums are verified during a base backup if they are
+          enabled. Specifying <literal>NOVERIFY_CHECKSUMS</literal> disables
+          this verification.
+         </para>
+        </listitem>
+       </varlistentry>
       </variablelist>
      </para>
      <para>
diff --git a/doc/src/sgml/ref/pg_basebackup.sgml b/doc/src/sgml/ref/pg_basebackup.sgml
index e8921b1bb4..95045669c9 100644
--- a/doc/src/sgml/ref/pg_basebackup.sgml
+++ b/doc/src/sgml/ref/pg_basebackup.sgml
@@ -506,6 +506,22 @@ PostgreSQL documentation
       </listitem>
      </varlistentry>
 
+     <varlistentry>
+      <term><option>-k</option></term>
+      <term><option>--no-verify-checksums</option></term>
+      <listitem>
+       <para>
+        Disables verification of checksums, if they are enabled on the server
+        the base backup is taken from. 
+       </para>
+       <para>
+        By default, checksums are verified and checksum failures will result in
+        a non-zero exit status. However, the base backup will not be removed in
+        this case, as if the <literal>--no-clean</literal> option was used.
+       </para>
+      </listitem>
+     </varlistentry>
+
      <varlistentry>
       <term><option>-v</option></term>
       <term><option>--verbose</option></term>
diff --git a/src/backend/replication/basebackup.c b/src/backend/replication/basebackup.c
index 516eea57f8..3c1fd620ae 100644
--- a/src/backend/replication/basebackup.c
+++ b/src/backend/replication/basebackup.c
@@ -16,6 +16,7 @@
 #include <unistd.h>
 #include <time.h>
 
+#include "access/xlog.h"
 #include "access/xlog_internal.h"	/* for pg_start/stop_backup */
 #include "catalog/catalog.h"
 #include "catalog/pg_type.h"
@@ -31,6 +32,8 @@
 #include "replication/basebackup.h"
 #include "replication/walsender.h"
 #include "replication/walsender_private.h"
+#include "storage/bufpage.h"
+#include "storage/checksum.h"
 #include "storage/dsm_impl.h"
 #include "storage/fd.h"
 #include "storage/ipc.h"
@@ -99,6 +102,15 @@ static TimeOffset elapsed_min_unit;
 /* The last check of the transfer rate. */
 static TimestampTz throttled_last;
 
+/* The starting XLOG position of the base backup. */
+static XLogRecPtr startptr;
+
+/* Total number of checksum failures during base backup. */
+static int64 total_checksum_failures;
+
+/* Do not verify checksums. */
+static bool noverify_checksums = false;
+
 /*
  * The contents of these directories are removed or recreated during server
  * start so they are not included in backups.  The directories themselves are
@@ -194,7 +206,6 @@ base_backup_cleanup(int code, Datum arg)
 static void
 perform_base_backup(basebackup_options *opt)
 {
-	XLogRecPtr	startptr;
 	TimeLineID	starttli;
 	XLogRecPtr	endptr;
 	TimeLineID	endtli;
@@ -210,6 +221,8 @@ perform_base_backup(basebackup_options *opt)
 	labelfile = makeStringInfo();
 	tblspc_map_file = makeStringInfo();
 
+	total_checksum_failures = 0;
+
 	startptr = do_pg_start_backup(opt->label, opt->fastcheckpoint, &starttli,
 								  labelfile, &tablespaces,
 								  tblspc_map_file,
@@ -568,6 +581,17 @@ perform_base_backup(basebackup_options *opt)
 		pq_putemptymessage('c');
 	}
 	SendXlogRecPtrResult(endptr, endtli);
+
+	if (total_checksum_failures)
+	{
+		if (total_checksum_failures > 1)
+			ereport(WARNING,
+				(errmsg("%ld total checksum verification failures", total_checksum_failures)));
+		ereport(ERROR,
+			(errcode(ERRCODE_DATA_CORRUPTED),
+			errmsg("checksum verification failure during base backup")));
+	}
+
 }
 
 /*
@@ -597,6 +621,7 @@ parse_basebackup_options(List *options, basebackup_options *opt)
 	bool		o_wal = false;
 	bool		o_maxrate = false;
 	bool		o_tablespace_map = false;
+	bool		o_noverify_checksums = false;
 
 	MemSet(opt, 0, sizeof(*opt));
 	foreach(lopt, options)
@@ -676,6 +701,15 @@ parse_basebackup_options(List *options, basebackup_options *opt)
 			opt->sendtblspcmapfile = true;
 			o_tablespace_map = true;
 		}
+		else if (strcmp(defel->defname, "noverify_checksums") == 0)
+		{
+			if (o_noverify_checksums)
+				ereport(ERROR,
+						(errcode(ERRCODE_SYNTAX_ERROR),
+						 errmsg("duplicate option \"%s\"", defel->defname)));
+			noverify_checksums = true;
+			o_noverify_checksums = true;
+		}
 		else
 			elog(ERROR, "option \"%s\" not recognized",
 				 defel->defname);
@@ -1257,6 +1291,40 @@ sendDir(const char *path, int basepathlen, bool sizeonly, List *tablespaces,
 	return size;
 }
 
+static const char *no_heap_files[] = {
+	"pg_control",
+	"pg_filenode.map",
+	"pg_internal.init",
+	"PG_VERSION",
+	NULL,
+};
+
+static bool
+is_heap_file(const char *pn, const char *fn)
+{
+	const char **f;
+
+	/* Skip current and parent directory */
+	if (strcmp(pn, ".") == 0 ||
+		strcmp(pn, "..") == 0)
+		return false;
+
+	/* Check that the file is in a tablespace */
+	if (strncmp(pn, "./global/", 9) == 0 ||
+		strncmp(pn, "./base/", 7) == 0 ||
+		strncmp(pn, "/", 1) == 0)
+	{
+		/* Compare file against no_heap_files skiplist */
+		for (f = no_heap_files; *f; f++)
+			if (strcmp(*f, fn) == 0)
+				return false;
+
+		return true;
+	}
+	else
+		return false;
+}
+
 /*****
  * Functions for handling tar file format
  *
@@ -1277,10 +1345,21 @@ sendFile(const char *readfilename, const char *tarfilename, struct stat *statbuf
 		 bool missing_ok)
 {
 	FILE	   *fp;
+	BlockNumber blkno = 0;
+	bool		block_retry = false;
 	char		buf[TAR_SEND_SIZE];
+	uint16		checksum;
+	int			checksum_failures = 0;
 	size_t		cnt;
+	char	   *filename;
+	int			i;
 	pgoff_t		len = 0;
+	char	   *page;
 	size_t		pad;
+	PageHeader  phdr;
+	int			segmentno = 0;
+	char	   *segmentpath;
+	bool		verify_checksum = false;
 
 	fp = AllocateFile(readfilename, "rb");
 	if (fp == NULL)
@@ -1294,8 +1373,143 @@ sendFile(const char *readfilename, const char *tarfilename, struct stat *statbuf
 
 	_tarWriteHeader(tarfilename, NULL, statbuf, false);
 
+	/*
+	 * Filename (excluding path).  As last_dir_separator() includes
+	 * the last directory separator, we chop that off by incrementing the
+	 * pointer.
+	 */
+	filename = last_dir_separator(pstrdup(readfilename)) + 1;
+
+	/*
+	 * Verify checksums only when checksums are enabled, and the file to
+	 * send is either in one of the default tablespaces (`./global' or
+	 * `./base'), or in an external tablespace with an absolute pathname
+	 * (starting with `/') and is not in the list of non-heap files to be
+	 * skipped.
+	 */
+	if (!noverify_checksums && DataChecksumsEnabled() &&
+		is_heap_file(readfilename, filename))
+	{
+		verify_checksum = true;
+
+		/*
+		 * Cut off at the segment boundary (".") to get the segment number in order
+		 * to mix it into the checksum.
+		 */
+		segmentpath = strstr(filename, ".");
+		if (verify_checksum && segmentpath != NULL)
+		{
+			*segmentpath++ = '\0';
+			segmentno = atoi(segmentpath);
+			if (segmentno == 0)
+				ereport(ERROR,
+						(errmsg("invalid segment number %d in filen \"%s\"",
+						segmentno, filename)));
+		}
+	}
+
 	while ((cnt = fread(buf, 1, Min(sizeof(buf), statbuf->st_size - len), fp)) > 0)
 	{
+		if (verify_checksum)
+		{
+			/*
+			 * The checksums are verified at block level, so we iterate over
+			 * the buffer in chunks of BLCKSZ, after making sure that
+			 * TAR_SEND_SIZE/buf is divisible by BLCKSZ and we read
+			 * a multiple of BLCKSZ bytes.
+			 */
+			Assert(TAR_SEND_SIZE % BLCKSZ == 0);
+			if (cnt % BLCKSZ != 0)
+			{
+				ereport(WARNING,
+						(errmsg("cannot verify checksum in file \"%s\", block "
+								"%d: read buffer size %d and page size %d "
+								"differ",
+								readfilename, blkno, (int)cnt, BLCKSZ)));
+				verify_checksum = false;
+				continue;
+			}
+			for (i = 0; i < cnt / BLCKSZ; i++)
+			{
+				page = buf + BLCKSZ * i;
+				/*
+				 * Only check pages which have not been modified since the
+				 * start of the base backup. Otherwise, they might have been
+				 * written only halfway and the checksum would not be valid.
+				 * However, replaying WAL would reinstate the correct page in
+				 * this case.
+				 */
+				if (PageGetLSN(page) < startptr)
+				{
+					checksum = pg_checksum_page((char *) page, blkno + segmentno*RELSEG_SIZE);
+					phdr = (PageHeader) page;
+					if (phdr->pd_checksum != checksum)
+					{
+						/*
+						 * Retry the block on the first failure.  It's possible
+						 * that we read the first 4K page of the block just
+						 * before postgres updated the entire block so it ends
+						 * up looking torn to us.  We only need to retry once
+						 * because the LSN should be updated to something we can
+						 * ignore on the next pass.  If the error happens again
+						 * then it is a true validation failure.
+						 */
+						if (block_retry == false)
+						{
+							/* Reread the failed block */
+							if (fseek(fp, -(cnt - BLCKSZ * i), SEEK_CUR) == -1)
+							{
+								ereport(ERROR,
+										(errcode_for_file_access(),
+										 errmsg("could not fseek in file \"%s\": %m",
+										 readfilename)));
+							}
+
+							if (fread(buf + BLCKSZ * i, 1, BLCKSZ, fp) != BLCKSZ)
+							{
+								ereport(ERROR,
+										(errcode_for_file_access(),
+										 errmsg("could not reread block %d of file \"%s\": %m",
+										 blkno, readfilename)));
+							}
+
+							if (fseek(fp, cnt - BLCKSZ * i - BLCKSZ, SEEK_CUR) == -1)
+							{
+								ereport(ERROR,
+										(errcode_for_file_access(),
+										 errmsg("could not fseek in file \"%s\": %m",
+										 readfilename)));
+							}
+
+							/* Set flag so we know a retry was attempted */
+							block_retry = true;
+
+							/* Reset loop to validate the block again */
+							i--;
+							continue;
+						}
+
+						checksum_failures++;
+
+						if (checksum_failures <= 5)
+							ereport(WARNING,
+									(errmsg("checksum verification failed in "
+											"file \"%s\", block %d: calculated "
+											"%X but expected %X",
+											readfilename, blkno, checksum,
+											phdr->pd_checksum)));
+						if (checksum_failures == 5)
+							ereport(WARNING,
+									(errmsg("further checksum verification "
+											"failures in file \"%s\" will not "
+											"be reported", readfilename)));
+					}
+				}
+				block_retry = false;
+				blkno++;
+			}
+		}
+
 		/* Send the chunk as a CopyData message */
 		if (pq_putmessage('d', buf, cnt))
 			ereport(ERROR,
@@ -1313,6 +1527,7 @@ sendFile(const char *readfilename, const char *tarfilename, struct stat *statbuf
 			 */
 			break;
 		}
+
 	}
 
 	/* If the file was truncated while we were sending it, pad it with zeros */
@@ -1341,6 +1556,13 @@ sendFile(const char *readfilename, const char *tarfilename, struct stat *statbuf
 
 	FreeFile(fp);
 
+	if (checksum_failures > 1) {
+		ereport(WARNING,
+				(errmsg("file \"%s\" has a total of %d checksum verification "
+						"failures", readfilename, checksum_failures)));
+	}
+	total_checksum_failures += checksum_failures;
+
 	return true;
 }
 
diff --git a/src/backend/replication/repl_gram.y b/src/backend/replication/repl_gram.y
index beb2c2877b..843a878ff3 100644
--- a/src/backend/replication/repl_gram.y
+++ b/src/backend/replication/repl_gram.y
@@ -77,6 +77,7 @@ static SQLCmd *make_sqlcmd(void);
 %token K_MAX_RATE
 %token K_WAL
 %token K_TABLESPACE_MAP
+%token K_NOVERIFY_CHECKSUMS
 %token K_TIMELINE
 %token K_PHYSICAL
 %token K_LOGICAL
@@ -154,7 +155,7 @@ var_name:	IDENT	{ $$ = $1; }
 
 /*
  * BASE_BACKUP [LABEL '<label>'] [PROGRESS] [FAST] [WAL] [NOWAIT]
- * [MAX_RATE %d] [TABLESPACE_MAP]
+ * [MAX_RATE %d] [TABLESPACE_MAP] [NOVERIFY_CHECKSUMS]
  */
 base_backup:
 			K_BASE_BACKUP base_backup_opt_list
@@ -208,6 +209,11 @@ base_backup_opt:
 				  $$ = makeDefElem("tablespace_map",
 								   (Node *)makeInteger(true), -1);
 				}
+			| K_NOVERIFY_CHECKSUMS
+				{
+				  $$ = makeDefElem("noverify_checksums",
+								   (Node *)makeInteger(true), -1);
+				}
 			;
 
 create_replication_slot:
diff --git a/src/backend/replication/repl_scanner.l b/src/backend/replication/repl_scanner.l
index fb48241e48..7bb501f594 100644
--- a/src/backend/replication/repl_scanner.l
+++ b/src/backend/replication/repl_scanner.l
@@ -92,6 +92,7 @@ PROGRESS			{ return K_PROGRESS; }
 MAX_RATE		{ return K_MAX_RATE; }
 WAL			{ return K_WAL; }
 TABLESPACE_MAP			{ return K_TABLESPACE_MAP; }
+NOVERIFY_CHECKSUMS	{ return K_NOVERIFY_CHECKSUMS; }
 TIMELINE			{ return K_TIMELINE; }
 START_REPLICATION	{ return K_START_REPLICATION; }
 CREATE_REPLICATION_SLOT		{ return K_CREATE_REPLICATION_SLOT; }
diff --git a/src/bin/pg_basebackup/pg_basebackup.c b/src/bin/pg_basebackup/pg_basebackup.c
index 1b32592063..39013ff7e0 100644
--- a/src/bin/pg_basebackup/pg_basebackup.c
+++ b/src/bin/pg_basebackup/pg_basebackup.c
@@ -39,6 +39,7 @@
 #include "replication/basebackup.h"
 #include "streamutil.h"
 
+#define ERRCODE_DATA_CORRUPTED	"XX001"
 
 typedef struct TablespaceListCell
 {
@@ -81,6 +82,7 @@ static char *xlog_dir = NULL;
 static char format = 'p';		/* p(lain)/t(ar) */
 static char *label = "pg_basebackup base backup";
 static bool noclean = false;
+static bool checksum_failure = false;
 static bool showprogress = false;
 static int	verbose = 0;
 static int	compresslevel = 0;
@@ -95,6 +97,7 @@ static char *replication_slot = NULL;
 static bool temp_replication_slot = true;
 static bool create_slot = false;
 static bool no_slot = false;
+static bool verify_checksums = true;
 
 static bool success = false;
 static bool made_new_pgdata = false;
@@ -155,7 +158,7 @@ cleanup_directories_atexit(void)
 	if (success || in_log_streamer)
 		return;
 
-	if (!noclean)
+	if (!noclean && !checksum_failure)
 	{
 		if (made_new_pgdata)
 		{
@@ -195,7 +198,7 @@ cleanup_directories_atexit(void)
 	}
 	else
 	{
-		if (made_new_pgdata || found_existing_pgdata)
+		if ((made_new_pgdata || found_existing_pgdata) && !checksum_failure)
 			fprintf(stderr,
 					_("%s: data directory \"%s\" not removed at user's request\n"),
 					progname, basedir);
@@ -206,7 +209,7 @@ cleanup_directories_atexit(void)
 					progname, xlog_dir);
 	}
 
-	if (made_tablespace_dirs || found_tablespace_dirs)
+	if ((made_tablespace_dirs || found_tablespace_dirs) && !checksum_failure)
 		fprintf(stderr,
 				_("%s: changes to tablespace directories will not be undone\n"),
 				progname);
@@ -360,6 +363,8 @@ usage(void)
 	printf(_("  -P, --progress         show progress information\n"));
 	printf(_("  -S, --slot=SLOTNAME    replication slot to use\n"));
 	printf(_("      --no-slot          prevent creation of temporary replication slot\n"));
+	printf(_("  -k, --no-verify-checksums\n"
+			 "                         do not verify checksums\n"));
 	printf(_("  -v, --verbose          output verbose messages\n"));
 	printf(_("  -V, --version          output version information, then exit\n"));
 	printf(_("  -?, --help             show this help, then exit\n"));
@@ -1808,14 +1813,15 @@ BaseBackup(void)
 	}
 
 	basebkp =
-		psprintf("BASE_BACKUP LABEL '%s' %s %s %s %s %s %s",
+		psprintf("BASE_BACKUP LABEL '%s' %s %s %s %s %s %s %s",
 				 escaped_label,
 				 showprogress ? "PROGRESS" : "",
 				 includewal == FETCH_WAL ? "WAL" : "",
 				 fastcheckpoint ? "FAST" : "",
 				 includewal == NO_WAL ? "" : "NOWAIT",
 				 maxrate_clause ? maxrate_clause : "",
-				 format == 't' ? "TABLESPACE_MAP" : "");
+				 format == 't' ? "TABLESPACE_MAP" : "",
+				 verify_checksums ? "" : "NOVERIFY_CHECKSUMS");
 
 	if (PQsendQuery(conn, basebkp) == 0)
 	{
@@ -1970,8 +1976,17 @@ BaseBackup(void)
 	res = PQgetResult(conn);
 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
 	{
-		fprintf(stderr, _("%s: final receive failed: %s"),
-				progname, PQerrorMessage(conn));
+		const char *sqlstate = PQresultErrorField(res, PG_DIAG_SQLSTATE);
+		if (sqlstate &&
+			strcmp(sqlstate, ERRCODE_DATA_CORRUPTED) == 0)
+		{
+			fprintf(stderr, _("%s: checksum error occured\n"),
+					progname);
+			checksum_failure = true;
+		} else {
+			fprintf(stderr, _("%s: final receive failed: %s"),
+					progname, PQerrorMessage(conn));
+		}
 		disconnect_and_exit(1);
 	}
 
@@ -2140,6 +2155,7 @@ main(int argc, char **argv)
 		{"progress", no_argument, NULL, 'P'},
 		{"waldir", required_argument, NULL, 1},
 		{"no-slot", no_argument, NULL, 2},
+		{"no-verify-checksums", no_argument, NULL, 'k'},
 		{NULL, 0, NULL, 0}
 	};
 	int			c;
@@ -2166,7 +2182,7 @@ main(int argc, char **argv)
 
 	atexit(cleanup_directories_atexit);
 
-	while ((c = getopt_long(argc, argv, "CD:F:r:RS:T:X:l:nNzZ:d:c:h:p:U:s:wWvP",
+	while ((c = getopt_long(argc, argv, "CD:F:r:RS:T:X:l:nNzZ:d:c:h:p:U:s:wWkvP",
 							long_options, &option_index)) != -1)
 	{
 		switch (c)
@@ -2308,6 +2324,9 @@ main(int argc, char **argv)
 			case 'P':
 				showprogress = true;
 				break;
+			case 'k':
+				verify_checksums = false;
+				break;
 			default:
 
 				/*
diff --git a/src/bin/pg_basebackup/t/010_pg_basebackup.pl b/src/bin/pg_basebackup/t/010_pg_basebackup.pl
index 32d21ce644..3162cdcd01 100644
--- a/src/bin/pg_basebackup/t/010_pg_basebackup.pl
+++ b/src/bin/pg_basebackup/t/010_pg_basebackup.pl
@@ -5,7 +5,7 @@ use Config;
 use File::Basename qw(basename dirname);
 use PostgresNode;
 use TestLib;
-use Test::More tests => 93;
+use Test::More tests => 104;
 
 program_help_ok('pg_basebackup');
 program_version_ok('pg_basebackup');
@@ -16,7 +16,7 @@ my $tempdir = TestLib::tempdir;
 my $node = get_new_node('main');
 
 # Initialize node without replication settings
-$node->init;
+$node->init(extra => [ '--data-checksums' ]);
 $node->start;
 my $pgdata = $node->data_dir;
 
@@ -402,3 +402,61 @@ like(
 	slurp_file("$tempdir/backupxs_sl_R/recovery.conf"),
 	qr/^primary_slot_name = 'slot1'\n/m,
 	'recovery.conf sets primary_slot_name');
+
+my $checksum = $node->safe_psql('postgres', 'SHOW data_checksums;');
+is($checksum, 'on', 'checksums are enabled');
+
+# get relfilenodes of relations to corrupt
+my $pg_class = $node->safe_psql('postgres',
+	q{SELECT pg_relation_filepath('pg_class')}
+);
+my $pg_index = $node->safe_psql('postgres',
+	q{SELECT pg_relation_filepath('pg_index')}
+);
+
+# induce corruption
+open $file, '+<', "$pgdata/$pg_class";
+seek($file, 4000, 0);
+syswrite($file, '\0\0\0\0\0\0\0\0\0');
+close $file;
+
+$node->command_checks_all([ 'pg_basebackup', '-D', "$tempdir/backup_corrupt"],
+	1,
+	[qr{^$}],
+	[qr/^WARNING.*checksum verification failed/s],
+	'pg_basebackup reports checksum mismatch'
+);
+
+# induce further corruption in 5 more blocks
+open $file, '+<', "$pgdata/$pg_class";
+my @offsets = (12192, 20384, 28576, 36768, 44960);
+foreach my $offset (@offsets) {
+  seek($file, $offset, 0);
+  syswrite($file, '\0\0\0\0\0\0\0\0\0');
+}
+close $file;
+
+$node->command_checks_all([ 'pg_basebackup', '-D', "$tempdir/backup_corrupt2"],
+        1,
+        [qr{^$}],
+        [qr/^WARNING.*further.*failures.*will.not.be.reported/s],
+        'pg_basebackup does not report more than 5 checksum mismatches'
+);
+
+# induce corruption in a second file
+open $file, '+<', "$pgdata/$pg_index";
+seek($file, 4000, 0);
+syswrite($file, '\0\0\0\0\0\0\0\0\0');
+close $file;
+
+$node->command_checks_all([ 'pg_basebackup', '-D', "$tempdir/backup_corrupt3"],
+        1,
+        [qr{^$}],
+        [qr/^WARNING.*7 total checksum verification failures/s],
+        'pg_basebackup correctly report the total number of checksum mismatches'
+);
+
+# do not verify checksums, should return ok
+$node->command_ok(
+	[   'pg_basebackup', '-D', "$tempdir/backup_corrupt4", '-k' ],
+	'pg_basebackup with -k does not report checksum mismatch');

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