mount_linux.go

// +build linux

/*
Copyright 2014 The Kubernetes Authors All rights reserved.

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 mount

import (
	"bufio"
	"fmt"
	"hash/adler32"
	"io"
	"os"
	"os/exec"
	"strconv"
	"strings"
	"syscall"

	"github.com/golang/glog"
	utilExec "k8s.io/kubernetes/pkg/util/exec"
)

const (
	// How many times to retry for a consistent read of /proc/mounts.
	maxListTries = 3
	// Number of fields per line in /proc/mounts as per the fstab man page.
	expectedNumFieldsPerLine = 6
	// Location of the mount file to use
	procMountsPath = "/proc/mounts"
)

const (
	// 'fsck' found errors and corrected them
	fsckErrorsCorrected = 1
	// 'fsck' found errors but exited without correcting them
	fsckErrorsUncorrected = 4
)

// Mounter provides the default implementation of mount.Interface
// for the linux platform.  This implementation assumes that the
// kubelet is running in the host's root mount namespace.
type Mounter struct{}

var _ = Interface(&Mounter{})

// Mount mounts source to target as fstype with given options. 'source' and 'fstype' must
// be an emtpy string in case it's not required, e.g. for remount, or for auto filesystem
// type, where kernel handles fs type for you. The mount 'options' is a list of options,
// currently come from mount(8), e.g. "ro", "remount", "bind", etc. If no more option is
// required, call Mount with an empty string list or nil.
func (mounter *Mounter) Mount(source string, target string, fstype string, options []string) error {
	bind, bindRemountOpts := isBind(options)

	if bind {
		err := doMount(source, target, fstype, []string{"bind"})
		if err != nil {
			return err
		}
		return doMount(source, target, fstype, bindRemountOpts)
	} else {
		return doMount(source, target, fstype, options)
	}
}

// isBind detects whether a bind mount is being requested and makes the remount options to
// use in case of bind mount, due to the fact that bind mount doesn't respect mount options.
// The list equals:
//   options - 'bind' + 'remount' (no duplicate)
func isBind(options []string) (bool, []string) {
	bindRemountOpts := []string{"remount"}
	bind := false

	if len(options) != 0 {
		for _, option := range options {
			switch option {
			case "bind":
				bind = true
				break
			case "remount":
				break
			default:
				bindRemountOpts = append(bindRemountOpts, option)
			}
		}
	}

	return bind, bindRemountOpts
}

// doMount runs the mount command.
func doMount(source string, target string, fstype string, options []string) error {
	glog.V(5).Infof("Mounting %s %s %s %v", source, target, fstype, options)
	mountArgs := makeMountArgs(source, target, fstype, options)
	command := exec.Command("mount", mountArgs...)
	output, err := command.CombinedOutput()
	if err != nil {
		return fmt.Errorf("Mount failed: %v\nMounting arguments: %s %s %s %v\nOutput: %s\n",
			err, source, target, fstype, options, string(output))
	}
	return err
}

// makeMountArgs makes the arguments to the mount(8) command.
func makeMountArgs(source, target, fstype string, options []string) []string {
	// Build mount command as follows:
	//   mount [-t $fstype] [-o $options] [$source] $target
	mountArgs := []string{}
	if len(fstype) > 0 {
		mountArgs = append(mountArgs, "-t", fstype)
	}
	if len(options) > 0 {
		mountArgs = append(mountArgs, "-o", strings.Join(options, ","))
	}
	if len(source) > 0 {
		mountArgs = append(mountArgs, source)
	}
	mountArgs = append(mountArgs, target)

	return mountArgs
}

// Unmount unmounts the target.
func (mounter *Mounter) Unmount(target string) error {
	glog.V(5).Infof("Unmounting %s", target)
	command := exec.Command("umount", target)
	output, err := command.CombinedOutput()
	if err != nil {
		return fmt.Errorf("Unmount failed: %v\nUnmounting arguments: %s\nOutput: %s\n", err, target, string(output))
	}
	return nil
}

// List returns a list of all mounted filesystems.
func (*Mounter) List() ([]MountPoint, error) {
	return listProcMounts(procMountsPath)
}

// IsLikelyNotMountPoint determines if a directory is not a mountpoint.
// It is fast but not necessarily ALWAYS correct. If the path is in fact
// a bind mount from one part of a mount to another it will not be detected.
// mkdir /tmp/a /tmp/b; mount --bin /tmp/a /tmp/b; IsLikelyNotMountPoint("/tmp/b")
// will return true. When in fact /tmp/b is a mount point. If this situation
// if of interest to you, don't use this function...
func (mounter *Mounter) IsLikelyNotMountPoint(file string) (bool, error) {
	stat, err := os.Stat(file)
	if err != nil {
		return true, err
	}
	rootStat, err := os.Lstat(file + "/..")
	if err != nil {
		return true, err
	}
	// If the directory has a different device as parent, then it is a mountpoint.
	if stat.Sys().(*syscall.Stat_t).Dev != rootStat.Sys().(*syscall.Stat_t).Dev {
		return false, nil
	}

	return true, nil
}

func listProcMounts(mountFilePath string) ([]MountPoint, error) {
	hash1, err := readProcMounts(mountFilePath, nil)
	if err != nil {
		return nil, err
	}

	for i := 0; i < maxListTries; i++ {
		mps := []MountPoint{}
		hash2, err := readProcMounts(mountFilePath, &mps)
		if err != nil {
			return nil, err
		}
		if hash1 == hash2 {
			// Success
			return mps, nil
		}
		hash1 = hash2
	}
	return nil, fmt.Errorf("failed to get a consistent snapshot of %v after %d tries", mountFilePath, maxListTries)
}

// readProcMounts reads the given mountFilePath (normally /proc/mounts) and produces a hash
// of the contents.  If the out argument is not nil, this fills it with MountPoint structs.
func readProcMounts(mountFilePath string, out *[]MountPoint) (uint32, error) {
	file, err := os.Open(mountFilePath)
	if err != nil {
		return 0, err
	}
	defer file.Close()
	return readProcMountsFrom(file, out)
}

func readProcMountsFrom(file io.Reader, out *[]MountPoint) (uint32, error) {
	hash := adler32.New()
	scanner := bufio.NewReader(file)
	for {
		line, err := scanner.ReadString('\n')
		if err == io.EOF {
			break
		}
		fields := strings.Fields(line)
		if len(fields) != expectedNumFieldsPerLine {
			return 0, fmt.Errorf("wrong number of fields (expected %d, got %d): %s", expectedNumFieldsPerLine, len(fields), line)
		}

		fmt.Fprintf(hash, "%s", line)

		if out != nil {
			mp := MountPoint{
				Device: fields[0],
				Path:   fields[1],
				Type:   fields[2],
				Opts:   strings.Split(fields[3], ","),
			}

			freq, err := strconv.Atoi(fields[4])
			if err != nil {
				return 0, err
			}
			mp.Freq = freq

			pass, err := strconv.Atoi(fields[5])
			if err != nil {
				return 0, err
			}
			mp.Pass = pass

			*out = append(*out, mp)
		}
	}
	return hash.Sum32(), nil
}

// formatAndMount uses unix utils to format and mount the given disk
func (mounter *SafeFormatAndMount) formatAndMount(source string, target string, fstype string, options []string) error {
	options = append(options, "defaults")

	// Run fsck on the disk to fix repairable issues
	args := []string{"-a", source}
	cmd := mounter.Runner.Command("fsck", args...)
	out, err := cmd.CombinedOutput()
	if err != nil {
		ee, isExitError := err.(utilExec.ExitError)
		switch {
		case err == utilExec.ErrExecutableNotFound:
			glog.Warningf("'fsck' not found on system; continuing mount without running 'fsck'.")
		case isExitError && ee.ExitStatus() == fsckErrorsCorrected:
			glog.Infof("Device %s has errors which were corrected by fsck.", source)
		case isExitError && ee.ExitStatus() == fsckErrorsUncorrected:
			return fmt.Errorf("'fsck' found errors on device %s but could not correct them: %s.", source, string(out))
		case isExitError && ee.ExitStatus() > fsckErrorsUncorrected:
			glog.Infof("`fsck` error %s", string(out))
		}
	}

	// Try to mount the disk
	err = mounter.Interface.Mount(source, target, fstype, options)
	if err != nil {
		// It is possible that this disk is not formatted. Double check using diskLooksUnformatted
		notFormatted, err := mounter.diskLooksUnformatted(source)
		if err == nil && notFormatted {
			args = []string{source}
			// Disk is unformatted so format it.
			// Use 'ext4' as the default
			if len(fstype) == 0 {
				fstype = "ext4"
			}
			if fstype == "ext4" || fstype == "ext3" {
				args = []string{"-E", "lazy_itable_init=0,lazy_journal_init=0", "-F", source}
			}
			cmd := mounter.Runner.Command("mkfs."+fstype, args...)
			_, err := cmd.CombinedOutput()
			if err == nil {
				// the disk has been formatted successfully try to mount it again.
				return mounter.Interface.Mount(source, target, fstype, options)
			}
			return err
		}
	}
	return err
}

// diskLooksUnformatted uses 'lsblk' to see if the given disk is unformated
func (mounter *SafeFormatAndMount) diskLooksUnformatted(disk string) (bool, error) {
	args := []string{"-nd", "-o", "FSTYPE", disk}
	cmd := mounter.Runner.Command("lsblk", args...)
	dataOut, err := cmd.CombinedOutput()
	output := strings.TrimSpace(string(dataOut))

	// TODO (#13212): check if this disk has partitions and return false, and
	// an error if so.

	if err != nil {
		return false, err
	}

	return output == "", nil
}