empty_dir_linux.go

//go:build linux
// +build linux

/*
Copyright 2015 The Kubernetes Authors.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package emptydir

import (
	"fmt"
	"strings"

	"golang.org/x/sys/unix"
	"k8s.io/apimachinery/pkg/api/resource"
	"k8s.io/klog/v2"
	"k8s.io/mount-utils"

	"k8s.io/api/core/v1"
)

// Defined by Linux - the type number for tmpfs mounts.
const (
	linuxTmpfsMagic     = 0x01021994
	linuxHugetlbfsMagic = 0x958458f6
)

// realMountDetector implements mountDetector in terms of syscalls.
type realMountDetector struct {
	mounter mount.Interface
}

// getPageSize obtains page size from the 'pagesize' mount option of the
// mounted volume
func getPageSize(path string, mounter mount.Interface) (*resource.Quantity, error) {
	// Get mount point data for the path
	mountPoints, err := mounter.List()
	if err != nil {
		return nil, fmt.Errorf("error listing mount points: %v", err)
	}
	// Find mount point for the path
	mountPoint, err := func(mps []mount.MountPoint, mpPath string) (*mount.MountPoint, error) {
		for _, mp := range mps {
			if mp.Path == mpPath {
				return &mp, nil
			}
		}
		return nil, fmt.Errorf("mount point for %s not found", mpPath)
	}(mountPoints, path)
	if err != nil {
		return nil, err
	}
	// Get page size from the 'pagesize' option value
	for _, opt := range mountPoint.Opts {
		opt = strings.TrimSpace(opt)
		prefix := "pagesize="
		if strings.HasPrefix(opt, prefix) {
			// NOTE: Adding suffix 'i' as result should be comparable with a medium size.
			// pagesize mount option is specified without a suffix,
			// e.g. pagesize=2M or pagesize=1024M for x86 CPUs
			trimmedOpt := strings.TrimPrefix(opt, prefix)
			if !strings.HasSuffix(trimmedOpt, "i") {
				trimmedOpt = trimmedOpt + "i"
			}
			pageSize, err := resource.ParseQuantity(trimmedOpt)
			if err != nil {
				return nil, fmt.Errorf("error getting page size from '%s' mount option: %v", opt, err)
			}
			return &pageSize, nil
		}
	}
	return nil, fmt.Errorf("no pagesize option specified for %s mount", mountPoint.Path)
}

func (m *realMountDetector) GetMountMedium(path string, requestedMedium v1.StorageMedium) (v1.StorageMedium, bool, *resource.Quantity, error) {
	klog.V(5).Infof("Determining mount medium of %v", path)
	notMnt, err := m.mounter.IsLikelyNotMountPoint(path)
	if err != nil {
		return v1.StorageMediumDefault, false, nil, fmt.Errorf("IsLikelyNotMountPoint(%q): %v", path, err)
	}

	buf := unix.Statfs_t{}
	if err := unix.Statfs(path, &buf); err != nil {
		return v1.StorageMediumDefault, false, nil, fmt.Errorf("statfs(%q): %v", path, err)
	}

	klog.V(3).Infof("Statfs_t of %v: %+v", path, buf)

	if buf.Type == linuxTmpfsMagic {
		return v1.StorageMediumMemory, !notMnt, nil, nil
	} else if int64(buf.Type) == linuxHugetlbfsMagic {
		// Skip page size detection if requested medium doesn't have size specified
		if requestedMedium == v1.StorageMediumHugePages {
			return v1.StorageMediumHugePages, !notMnt, nil, nil
		}
		// Get page size for the volume mount
		pageSize, err := getPageSize(path, m.mounter)
		if err != nil {
			return v1.StorageMediumHugePages, !notMnt, nil, err
		}
		return v1.StorageMediumHugePages, !notMnt, pageSize, nil
	}
	return v1.StorageMediumDefault, !notMnt, nil, nil
}