From 1b3dee951cf62da27bb9f53a5d5c5386b773d45a Mon Sep 17 00:00:00 2001
From: Alexander Staubo <alex@purefiction.net>
Date: Mon, 21 May 2018 12:10:38 -0400
Subject: [PATCH] When creating ext3/ext4 volume, pass -m0 to mkfs in order to
 disable the super-user-reserved blocks, which otherwise defaults to 5% of the
 entire disk.

Rationale: Reserving a percentage of the volume is generally a neither
useful nor desirable feature for volumes that aren't used as root file
systems for Linux distributions, since the reserved portion becomes
unavailable for non-root users. For containers, the general case is to
use the entire volume for data, without running as root. The case where
one might want reserved blocks enabled is much rarer.
---
 pkg/util/mount/mount_linux.go                | 6 +++++-
 pkg/util/mount/safe_format_and_mount_test.go | 8 ++++----
 2 files changed, 9 insertions(+), 5 deletions(-)

diff --git a/pkg/util/mount/mount_linux.go b/pkg/util/mount/mount_linux.go
index 05bf54dae8e..b5fb1acafae 100644
--- a/pkg/util/mount/mount_linux.go
+++ b/pkg/util/mount/mount_linux.go
@@ -511,7 +511,11 @@ func (mounter *SafeFormatAndMount) formatAndMount(source string, target string,
 			}
 
 			if fstype == "ext4" || fstype == "ext3" {
-				args = []string{"-F", source}
+				args = []string{
+					"-F",  // Force flag
+					"-m0", // Zero blocks reserved for super-user
+					source,
+				}
 			}
 			glog.Infof("Disk %q appears to be unformatted, attempting to format as type: %q with options: %v", source, fstype, args)
 			_, err := mounter.Exec.Run("mkfs."+fstype, args...)
diff --git a/pkg/util/mount/safe_format_and_mount_test.go b/pkg/util/mount/safe_format_and_mount_test.go
index 20bfeb9f624..506126b300b 100644
--- a/pkg/util/mount/safe_format_and_mount_test.go
+++ b/pkg/util/mount/safe_format_and_mount_test.go
@@ -116,7 +116,7 @@ func TestSafeFormatAndMount(t *testing.T) {
 			execScripts: []ExecArgs{
 				{"fsck", []string{"-a", "/dev/foo"}, "", nil},
 				{"blkid", []string{"-p", "-s", "TYPE", "-s", "PTTYPE", "-o", "export", "/dev/foo"}, "", &fakeexec.FakeExitError{Status: 2}},
-				{"mkfs.ext4", []string{"-F", "/dev/foo"}, "", fmt.Errorf("formatting failed")},
+				{"mkfs.ext4", []string{"-F", "-m0", "/dev/foo"}, "", fmt.Errorf("formatting failed")},
 			},
 			expectedError: fmt.Errorf("formatting failed"),
 		},
@@ -127,7 +127,7 @@ func TestSafeFormatAndMount(t *testing.T) {
 			execScripts: []ExecArgs{
 				{"fsck", []string{"-a", "/dev/foo"}, "", nil},
 				{"blkid", []string{"-p", "-s", "TYPE", "-s", "PTTYPE", "-o", "export", "/dev/foo"}, "", &fakeexec.FakeExitError{Status: 2}},
-				{"mkfs.ext4", []string{"-F", "/dev/foo"}, "", nil},
+				{"mkfs.ext4", []string{"-F", "-m0", "/dev/foo"}, "", nil},
 			},
 			expectedError: fmt.Errorf("Still cannot mount"),
 		},
@@ -138,7 +138,7 @@ func TestSafeFormatAndMount(t *testing.T) {
 			execScripts: []ExecArgs{
 				{"fsck", []string{"-a", "/dev/foo"}, "", nil},
 				{"blkid", []string{"-p", "-s", "TYPE", "-s", "PTTYPE", "-o", "export", "/dev/foo"}, "", &fakeexec.FakeExitError{Status: 2}},
-				{"mkfs.ext4", []string{"-F", "/dev/foo"}, "", nil},
+				{"mkfs.ext4", []string{"-F", "-m0", "/dev/foo"}, "", nil},
 			},
 			expectedError: nil,
 		},
@@ -149,7 +149,7 @@ func TestSafeFormatAndMount(t *testing.T) {
 			execScripts: []ExecArgs{
 				{"fsck", []string{"-a", "/dev/foo"}, "", nil},
 				{"blkid", []string{"-p", "-s", "TYPE", "-s", "PTTYPE", "-o", "export", "/dev/foo"}, "", &fakeexec.FakeExitError{Status: 2}},
-				{"mkfs.ext3", []string{"-F", "/dev/foo"}, "", nil},
+				{"mkfs.ext3", []string{"-F", "-m0", "/dev/foo"}, "", nil},
 			},
 			expectedError: nil,
 		},