[PBCKP-336] Fix segno calculation.

It were lost during fork-name detection fix at eaf3b14 .
And since there were no basic test for this, it were not detected.

Author: funny-falcon

src/dir.c

@@ -1786,13 +1786,16 @@ is_forkname(char *name, size_t *pos, const char *forkname)
 }
 
 #define OIDCHARS 10
+#define MAXSEGNO (((uint64_t)1<<32)/RELSEG_SIZE-1)
+#define SEGNOCHARS 5 /* when BLCKSZ == (1<<15) */
 
 /* Set forkName if possible */
 bool
 set_forkname(pgFile *file)
 {
 	size_t i = 0;
 	uint64_t oid = 0; /* use 64bit to not check for overflow in a loop */
+	uint64_t segno = 0;
 
 	/* pretend it is not relation file */
 	file->relOid = 0;
@@ -1823,8 +1826,15 @@ set_forkname(pgFile *file)
 	/* /^\d+(_(vm|fsm|init|ptrack))?\.\d+$/ */
 	if (file->name[i] == '.' && isdigit(file->name[i+1]))
 	{
+		size_t start = i+1;
 		for (i++; isdigit(file->name[i]); i++)
-			;
+		{
+			if (i == start && file->name[i] == '0')
+				return false;
+			segno = segno * 10 + file->name[i] - '0';
+		}
+		if (i - start > SEGNOCHARS || segno > MAXSEGNO)
+			return false;
 	}
 
 	/* CFS "fork name" */
@@ -1843,6 +1853,7 @@ set_forkname(pgFile *file)
 	}
 
 	file->relOid = oid;
+	file->segno = segno;
 	file->is_datafile = file->forkName == none;
 	return true;
 }

tests/backup.py

@@ -13,6 +13,38 @@
 
 class BackupTest(ProbackupTest, unittest.TestCase):
 
+    def test_basic_full_backup(self):
+        """
+        Just test full backup with at least two segments
+        """
+        fname = self.id().split('.')[3]
+        node = self.make_simple_node(
+            base_dir=os.path.join(module_name, fname, 'node'),
+            initdb_params=['--data-checksums'],
+            # we need to write a lot. Lets speedup a bit.
+            pg_options={"fsync": "off", "synchronous_commit": "off"})
+
+        backup_dir = os.path.join(self.tmp_path, module_name, fname, 'backup')
+        self.init_pb(backup_dir)
+        self.add_instance(backup_dir, 'node', node)
+        self.set_archiving(backup_dir, 'node', node)
+        node.slow_start()
+
+        # Fill with data
+        # Have to use scale=100 to create second segment.
+        node.pgbench_init(scale=100, no_vacuum=True)
+
+        # FULL
+        backup_id = self.backup_node(backup_dir, 'node', node)
+
+        out = self.validate_pb(backup_dir, 'node', backup_id)
+        self.assertIn(
+            "INFO: Backup {0} is valid".format(backup_id),
+            out)
+
+        # Clean after yourself
+        self.del_test_dir(module_name, fname)
+
     # @unittest.skip("skip")
     # @unittest.expectedFailure
     # PGPRO-707