lvm.go

/*
Copyright 2018 Google Inc.

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 main

import (
	"bufio"
	"bytes"
	"errors"
	"fmt"
	"os/exec"
	"strconv"
	"strings"
)

type lvResizer string // /dev/mapper/debianvg-root

func (r lvResizer) String() string { return fmt.Sprintf("LVM LV %s", string(r)) }

type lvState struct {
	dev        string // 0th element in lvdisplay -c
	vg         string // 1
	numSectors int64  // 6
}

func (r lvResizer) state() (s lvState, err error) {
	s.dev = string(r)
	// # lvdisplay -c /dev/mapper/debvg-root
	//   /dev/debvg/root:debvg:3:1:-1:1:8434778112:1029636:-1:0:-1:254:0
	outb, err := exec.Command("lvdisplay", "-c", s.dev).Output()
	if err != nil {
		return s, fmt.Errorf("running lvdisplay -c %s: %v", s.dev, execErrDetail(err))
	}
	f := strings.Split(strings.TrimSpace(string(outb)), ":")
	if len(f) < 13 {
		return s, fmt.Errorf("too few expected fields in lvdisplay -c %s output: %q", s.dev, outb)
	}
	s.vg = f[1]
	s.numSectors, err = strconv.ParseInt(f[6], 10, 64)
	if err != nil {
		return s, fmt.Errorf("bogus field at index 6 in lvdisplay -c %s output: %q: %v", s.dev, outb, err)
	}
	return s, nil
}

func (r lvResizer) DepResizer() (Resizer, error) {
	lvs, err := r.state()
	if err != nil {
		return nil, err
	}

	out, err := exec.Command("pvdisplay", "-c").Output()
	if err != nil {
		return nil, fmt.Errorf("running pvdisplay -c: %v", execErrDetail(err))
	}
	bs := bufio.NewScanner(bytes.NewReader(out))
	for bs.Scan() {
		f := strings.Split(strings.TrimSpace(bs.Text()), ":")
		if len(f) < 2 || f[1] != lvs.vg {
			continue
		}
		dev := f[0]
		// TODO: support LVs with more than one PV. But that's
		// not a problem I have with cloudy things. So skip
		// for now. Probably change the DepResizer method to
		// return []Resizer.
		return pvResizer(dev), nil
	}
	return nil, nil
}

func (r lvResizer) State() (string, error) {
	lvs, err := r.state()
	if err != nil {
		return "", err
	}
	return fmt.Sprintf("sectors=%d", lvs.numSectors), nil
}

func (r lvResizer) Resize() error {
	lvDev := string(r)
	if *dry {
		fmt.Printf("[dry-run] would've run lvextend -l +100%%FREE %s", lvDev)
		return nil
	}
	_, err := exec.Command("lvextend", "-l", "+100%FREE", lvDev).Output()
	if err != nil {
		ee, ok := err.(*exec.ExitError)
		if ok && strings.Contains(string(ee.Stderr), "matches existing size") {
			return nil
		}
		var extraMsg string
		if ok && len(ee.Stderr) > 0 {
			extraMsg = fmt.Sprintf("; stderr=%s", ee.Stderr)
		}
		return fmt.Errorf("lvextend on %s: %v%s", lvDev, err, extraMsg)
	}
	return nil
}

type pvResizer string // "/dev/sda3" or potentially a whole disk e.g. "/dev/sdb"

func (r pvResizer) String() string { return fmt.Sprintf("LVM PV %s", string(r)) }

func (r pvResizer) State() (string, error) {
	dev := string(r)
	out, err := exec.Command("pvdisplay", "-c", dev).Output()
	if err != nil {
		return "", errors.New(execErrDetail(err))
	}
	f := strings.Split(strings.TrimSpace(string(out)), ":")
	if len(f) < 3 {
		return "", fmt.Errorf("bogus pvdisplay -c %s output: %q", dev, out)
	}
	return fmt.Sprintf("sectors=%v", f[2]), nil
}

func (r pvResizer) Resize() error {
	dev := string(r)
	if *dry {
		fmt.Printf("[dry-run] would've run pvresize %v", dev)
		return nil
	}
	out, err := exec.Command("pvresize", dev).CombinedOutput()
	if err != nil {
		return fmt.Errorf("pvresize %s: %v, %s", dev, err, out)
	}
	return nil
}

func (r pvResizer) DepResizer() (Resizer, error) {
	dev := string(r)
	if devEndsInNumber(dev) {
		return partitionResizer(dev), nil
	}
	return nil, nil
}