generic/375: test both regular file and directory

generic/375 previously only tested SGID being cleared on a regular
file. It should test SGID being cleared on a directory too. Though
this is not required by POSIX, it is the Linux behavior.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Reviewed-by: Eryu Guan <eguan@redhat.com>
Signed-off-by: Eryu Guan <eguan@redhat.com>

tests/generic/375

@@ -52,10 +52,23 @@ _require_runas
 _require_acls
 
 cd $TEST_DIR
+
+# try with both regular file and directory
+for filetype in regular dir; do
+
+	case $filetype in
+	regular)
 		testfile=testfile.$seq
 		rm -f $testfile
-
 		touch $testfile
+		;;
+	*)
+		testfile=testdir.$seq
+		rm -rf $testfile
+		mkdir $testfile
+		;;
+	esac
+
 	chown 100:100 $testfile
 
 	echo '*** SGID should remain set (twice)'
@@ -76,6 +89,7 @@ stat -c %A $testfile
 
 	echo '*** Expected failure'
 	_runas -u 101 -g 101 -- chmod 2777 $testfile
+done
 
 status=0
 exit

tests/generic/375.out

@@ -7,3 +7,11 @@ QA output created by 375
 -rwxrwxrwx
 *** Expected failure
 chmod: changing permissions of 'testfile.375': Operation not permitted
+*** SGID should remain set (twice)
+drwxrwsrwx
+drwxrwsrwx
+*** SGID should be cleared (twice)
+drwxrwxrwx
+drwxrwxrwx
+*** Expected failure
+chmod: changing permissions of 'testdir.375': Operation not permitted