pg_upgrade: Convert old visibility map format to new format.

Commit a892234f830e832110f63fc0a2afce2fb21d1584 added a second bit per
page to the visibility map, but pg_upgrade has been unaware of it up
until now.  Therefore, a pg_upgrade from an earlier major release of
PostgreSQL to any commit preceding this one and following the one
mentioned above would result in invalid visibility map contents on the
new cluster, very possibly leading to data corruption.  This plugs
that hole.

Masahiko Sawada, reviewed by Jeff Janes, Bruce Momjian, Simon Riggs,
Michael Paquier, Andres Freund, me, and others.

1 files changed, 37 insertions, 11 deletions

diff --git a/src/bin/pg_upgrade/relfilenode.c b/src/bin/pg_upgrade/relfilenode.c
index b20f073ef7..0c1a8220bb 100644
--- a/src/bin/pg_upgrade/relfilenode.c
+++ b/src/bin/pg_upgrade/relfilenode.c
@@ -11,12 +11,13 @@
 
 #include "pg_upgrade.h"
 
+#include <sys/stat.h>
 #include "catalog/pg_class.h"
 #include "access/transam.h"
 
 
 static void transfer_single_new_db(FileNameMap *maps, int size, char *old_tablespace);
-static void transfer_relfile(FileNameMap *map, const char *suffix);
+static void transfer_relfile(FileNameMap *map, const char *suffix, bool vm_must_add_frozenbit);
 
 
 /*
@@ -132,6 +133,7 @@ transfer_single_new_db(FileNameMap *maps, int size, char *old_tablespace)
 {
 	int			mapnum;
 	bool		vm_crashsafe_match = true;
+	bool		vm_must_add_frozenbit = false;
 
 	/*
 	 * Do the old and new cluster disagree on the crash-safetiness of the vm
@@ -141,13 +143,20 @@ transfer_single_new_db(FileNameMap *maps, int size, char *old_tablespace)
 		new_cluster.controldata.cat_ver >= VISIBILITY_MAP_CRASHSAFE_CAT_VER)
 		vm_crashsafe_match = false;
 
+	/*
+	 * Do we need to rewrite visibilitymap?
+	 */
+	if (old_cluster.controldata.cat_ver < VISIBILITY_MAP_FROZEN_BIT_CAT_VER &&
+		new_cluster.controldata.cat_ver >= VISIBILITY_MAP_FROZEN_BIT_CAT_VER)
+		vm_must_add_frozenbit = true;
+
 	for (mapnum = 0; mapnum < size; mapnum++)
 	{
 		if (old_tablespace == NULL ||
 			strcmp(maps[mapnum].old_tablespace, old_tablespace) == 0)
 		{
 			/* transfer primary file */
-			transfer_relfile(&maps[mapnum], "");
+			transfer_relfile(&maps[mapnum], "", vm_must_add_frozenbit);
 
 			/* fsm/vm files added in PG 8.4 */
 			if (GET_MAJOR_VERSION(old_cluster.major_version) >= 804)
@@ -155,9 +164,9 @@ transfer_single_new_db(FileNameMap *maps, int size, char *old_tablespace)
 				/*
 				 * Copy/link any fsm and vm files, if they exist
 				 */
-				transfer_relfile(&maps[mapnum], "_fsm");
+				transfer_relfile(&maps[mapnum], "_fsm", vm_must_add_frozenbit);
 				if (vm_crashsafe_match)
-					transfer_relfile(&maps[mapnum], "_vm");
+					transfer_relfile(&maps[mapnum], "_vm", vm_must_add_frozenbit);
 			}
 		}
 	}
@@ -167,17 +176,19 @@ transfer_single_new_db(FileNameMap *maps, int size, char *old_tablespace)
 /*
  * transfer_relfile()
  *
- * Copy or link file from old cluster to new one.
+ * Copy or link file from old cluster to new one.  If vm_must_add_frozenbit
+ * is true, visibility map forks are converted and rewritten, even in link
+ * mode.
  */
 static void
-transfer_relfile(FileNameMap *map, const char *type_suffix)
+transfer_relfile(FileNameMap *map, const char *type_suffix, bool vm_must_add_frozenbit)
 {
 	const char *msg;
 	char		old_file[MAXPGPATH];
 	char		new_file[MAXPGPATH];
-	int			fd;
 	int			segno;
 	char		extent_suffix[65];
+	struct stat statbuf;
 
 	/*
 	 * Now copy/link any related segments as well. Remember, PG breaks large
@@ -210,7 +221,7 @@ transfer_relfile(FileNameMap *map, const char *type_suffix)
 		if (type_suffix[0] != '\0' || segno != 0)
 		{
 			/* Did file open fail? */
-			if ((fd = open(old_file, O_RDONLY, 0)) == -1)
+			if (stat(old_file, &statbuf) != 0)
 			{
 				/* File does not exist?  That's OK, just return */
 				if (errno == ENOENT)
@@ -220,7 +231,10 @@ transfer_relfile(FileNameMap *map, const char *type_suffix)
 							 map->nspname, map->relname, old_file, new_file,
 							 getErrorText());
 			}
-			close(fd);
+
+			/* If file is empty, just return */
+			if (statbuf.st_size == 0)
+				return;
 		}
 
 		unlink(new_file);
@@ -232,7 +246,13 @@ transfer_relfile(FileNameMap *map, const char *type_suffix)
 		{
 			pg_log(PG_VERBOSE, "copying \"%s\" to \"%s\"\n", old_file, new_file);
 
-			if ((msg = copyFile(old_file, new_file, true)) != NULL)
+			/* Rewrite visibility map if needed */
+			if (vm_must_add_frozenbit && (strcmp(type_suffix, "_vm") == 0))
+				msg = rewriteVisibilityMap(old_file, new_file, true);
+			else
+				msg = copyFile(old_file, new_file, true);
+
+			if (msg)
 				pg_fatal("error while copying relation \"%s.%s\" (\"%s\" to \"%s\"): %s\n",
 						 map->nspname, map->relname, old_file, new_file, msg);
 		}
@@ -240,7 +260,13 @@ transfer_relfile(FileNameMap *map, const char *type_suffix)
 		{
 			pg_log(PG_VERBOSE, "linking \"%s\" to \"%s\"\n", old_file, new_file);
 
-			if ((msg = linkFile(old_file, new_file)) != NULL)
+			/* Rewrite visibility map if needed */
+			if (vm_must_add_frozenbit && (strcmp(type_suffix, "_vm") == 0))
+				msg = rewriteVisibilityMap(old_file, new_file, true);
+			else
+				msg = linkFile(old_file, new_file);
+
+			if (msg)
 				pg_fatal("error while creating link for relation \"%s.%s\" (\"%s\" to \"%s\"): %s\n",
 						 map->nspname, map->relname, old_file, new_file, msg);
 		}