complete FC matching: rescan, create multipath.conf, etc

gistfile1.txt

package main

import (
	"fmt"
	"io/ioutil"
	"os"
	"path/filepath"
	"strings"
)

func rescan() {
	scsi_path := "/sys/class/scsi_host/"
	if dirs, err := ioutil.ReadDir(scsi_path); err == nil {
		for _, f := range dirs {
			name := scsi_path + f.Name() + "/scan"
			data := []byte("- - -")
			ioutil.WriteFile(name, data, 0666)
		}
	}
}

func findDM(disk string) string {
	sys_path := "/sys/block/"
	if dirs, err := ioutil.ReadDir(sys_path); err == nil {
		for _, f := range dirs {
			name := f.Name()
			if strings.HasPrefix(name, "dm-") {
				if _, err1 := os.Lstat(sys_path + name + "/slaves/" + disk); err1 == nil {
					return "/dev/" + name
				}
			}
		}
	}
	return ""
}

func createDMConf(path string) {
	if _, err := os.Lstat(path); err != nil {
		data := []byte(`defaults {
	find_multipaths yes
	user_friendly_names yes
}


blacklist {
}
`)
		ioutil.WriteFile(path, data, 0664)
	}
}

func findDisk(wwn, lun string) (string, string) {
	fc_path := "-fc-0x" + wwn + "-lun-" + lun
	dev_path := "/dev/disk/by-path/"
	if dirs, err := ioutil.ReadDir(dev_path); err == nil {
		for _, f := range dirs {
			name := f.Name()
			if strings.Contains(name, fc_path) {
				if disk, err1 := filepath.EvalSymlinks(dev_path + name); err1 == nil {
					arr := strings.Split(disk, "/")
					l := len(arr) - 1
					dev := arr[l]
					dm := findDM(dev)

					return disk, dm
				}

			}
		}
	}
	return "", ""
}

func main() {
	if len(os.Args) < 3 {
		fmt.Fprintf(os.Stdout, "usage: %s wwn lun_number\n", os.Args[0])
		os.Exit(1)
	}
	wwn := os.Args[1]
	lun := os.Args[2]
	createDMConf("/etc/multipath.conf")
	rescan()
	disk, dm := findDisk(wwn, lun)
	fmt.Fprintf(os.Stdout, "disk is %s, dm is %s\n", disk, dm)
}