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device.go
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device.go
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// tcmu is a package that connects to the TCM in Userspace kernel module, a part of the LIO stack. It provides the
// ability to emulate a SCSI storage device in pure Go.
package tcmu
import (
"fmt"
"io/ioutil"
"os"
"path"
"path/filepath"
"strconv"
"strings"
"syscall"
"time"
"golang.org/x/sys/unix"
"github.com/sirupsen/logrus"
)
const (
configDirFmt = "/sys/kernel/config/target/core/user_%d"
scsiDir = "/sys/kernel/config/target/loopback"
)
type Device struct {
scsi *SCSIHandler
devPath string
hbaDir string
deviceName string
uioFd int
mapsize uint64
mmap []byte
cmdChan chan *SCSICmd
respChan chan SCSIResponse
cmdTail uint32
}
// WWN provides two WWNs, one for the device itself and one for the loopback
// device created for the kernel.
type WWN interface {
DeviceID() string
NexusID() string
}
func (d *Device) GetDevConfig() string {
return fmt.Sprintf("go-tcmu//%s", d.scsi.VolumeName)
}
func (d *Device) Sizes() DataSizes {
return d.scsi.DataSizes
}
// OpenTCMUDevice creates the virtual device based on the details in the SCSIHandler, eventually creating a device under devPath (eg, "/dev") with the file name scsi.VolumeName.
// The returned Device represents the open device connection to the kernel, and must be closed.
func OpenTCMUDevice(devPath string, scsi *SCSIHandler) (*Device, error) {
d := &Device{
scsi: scsi,
devPath: devPath,
uioFd: -1,
hbaDir: fmt.Sprintf(configDirFmt, scsi.HBA),
}
err := d.Close()
if err != nil {
return nil, err
}
if err := d.preEnableTcmu(); err != nil {
return nil, err
}
if err := d.start(); err != nil {
return nil, err
}
return d, d.postEnableTcmu()
}
func (d *Device) Close() error {
err := d.teardown()
if err != nil {
return err
}
if d.uioFd != -1 {
unix.Close(d.uioFd)
}
return nil
}
func (d *Device) preEnableTcmu() error {
err := writeLines(path.Join(d.hbaDir, d.scsi.VolumeName, "control"), []string{
fmt.Sprintf("dev_size=%d", d.scsi.DataSizes.VolumeSize),
fmt.Sprintf("dev_config=%s", d.GetDevConfig()),
fmt.Sprintf("hw_block_size=%d", d.scsi.DataSizes.BlockSize),
"async=1",
})
if err != nil {
return err
}
return writeLines(path.Join(d.hbaDir, d.scsi.VolumeName, "enable"), []string{
"1",
})
}
func (d *Device) getSCSIPrefixAndWnn() (string, string) {
return path.Join(scsiDir, d.scsi.WWN.DeviceID(), "tpgt_1"), d.scsi.WWN.NexusID()
}
func (d *Device) getLunPath(prefix string) string {
return path.Join(prefix, "lun", fmt.Sprintf("lun_%d", d.scsi.LUN))
}
func (d *Device) postEnableTcmu() error {
prefix, nexusWnn := d.getSCSIPrefixAndWnn()
err := writeLines(path.Join(prefix, "nexus"), []string{
nexusWnn,
})
if err != nil {
return err
}
lunPath := d.getLunPath(prefix)
logrus.Debugf("Creating directory: %s", lunPath)
if err := os.MkdirAll(lunPath, 0755); err != nil && !os.IsExist(err) {
return err
}
logrus.Debugf("Linking: %s => %s", path.Join(lunPath, d.scsi.VolumeName), path.Join(d.hbaDir, d.scsi.VolumeName))
if err := os.Symlink(path.Join(d.hbaDir, d.scsi.VolumeName), path.Join(lunPath, d.scsi.VolumeName)); err != nil {
return err
}
return d.createDevEntry()
}
func (d *Device) createDevEntry() error {
os.MkdirAll(d.devPath, 0755)
dev := filepath.Join(d.devPath, d.scsi.VolumeName)
if _, err := os.Stat(dev); err == nil {
return fmt.Errorf("Device %s already exists, can not create", dev)
}
tgt, _ := d.getSCSIPrefixAndWnn()
address, err := ioutil.ReadFile(path.Join(tgt, "address"))
if err != nil {
return err
}
found := false
matches := []string{}
path := fmt.Sprintf("/sys/bus/scsi/devices/%s*/block/*/dev", strings.TrimSpace(string(address)))
for i := 0; i < 30; i++ {
var err error
matches, err = filepath.Glob(path)
if len(matches) > 0 && err == nil {
found = true
break
}
logrus.Debugf("Waiting for %s", path)
time.Sleep(1 * time.Second)
}
if !found {
return fmt.Errorf("Failed to find %s", path)
}
if len(matches) == 0 {
return fmt.Errorf("Failed to find %s", path)
}
if len(matches) > 1 {
return fmt.Errorf("Too many matches for %s, found %d", path, len(matches))
}
majorMinor, err := ioutil.ReadFile(matches[0])
if err != nil {
return err
}
parts := strings.Split(strings.TrimSpace(string(majorMinor)), ":")
if len(parts) != 2 {
return fmt.Errorf("Invalid major:minor string %s", string(majorMinor))
}
major, err := strconv.Atoi(parts[0])
if err != nil {
return err
}
minor, err := strconv.Atoi(parts[1])
if err != nil {
return err
}
logrus.Debugf("Creating device %s %d:%d", dev, major, minor)
return mknod(dev, major, minor)
}
func mknod(device string, major, minor int) error {
var fileMode os.FileMode = 0600
fileMode |= syscall.S_IFBLK
dev := int((major << 8) | (minor & 0xff) | ((minor & 0xfff00) << 12))
return syscall.Mknod(device, uint32(fileMode), dev)
}
func writeLines(target string, lines []string) error {
dir := path.Dir(target)
if stat, err := os.Stat(dir); os.IsNotExist(err) {
logrus.Debugf("Creating directory: %s", dir)
if err := os.MkdirAll(dir, 0755); err != nil {
return err
}
} else if !stat.IsDir() {
return fmt.Errorf("%s is not a directory", dir)
}
for _, line := range lines {
content := []byte(line + "\n")
logrus.Debugf("Setting %s: %s", target, line)
if err := ioutil.WriteFile(target, content, 0755); err != nil {
logrus.Errorf("Failed to write %s to %s: %v", line, target, err)
return err
}
}
return nil
}
func (d *Device) start() (err error) {
err = d.findDevice()
if err != nil {
return
}
d.cmdChan = make(chan *SCSICmd, 5)
d.respChan = make(chan SCSIResponse, 5)
go d.beginPoll()
d.scsi.DevReady(d.cmdChan, d.respChan)
return
}
func (d *Device) findDevice() error {
err := filepath.Walk("/dev", func(path string, i os.FileInfo, err error) error {
if err != nil {
return err
}
if i.IsDir() && path != "/dev" {
return filepath.SkipDir
}
if !strings.HasPrefix(i.Name(), "uio") {
return nil
}
sysfile := fmt.Sprintf("/sys/class/uio/%s/name", i.Name())
bytes, err := ioutil.ReadFile(sysfile)
if err != nil {
return err
}
split := strings.SplitN(strings.TrimRight(string(bytes), "\n"), "/", 4)
if split[0] != "tcm-user" {
// Not a TCM device
logrus.Debugf("%s is not a tcm-user device", i.Name())
return nil
}
if split[3] != d.GetDevConfig() {
// Not a TCM device
logrus.Debugf("%s is not our tcm-user device", i.Name())
return nil
}
err = d.openDevice(split[1], split[2], i.Name())
if err != nil {
return err
}
return filepath.SkipDir
})
if err == filepath.SkipDir {
return nil
}
return err
}
func (d *Device) openDevice(user string, vol string, uio string) error {
var err error
d.deviceName = vol
//d.uioFd, err = syscall.Open(fmt.Sprintf("/dev/%s", uio), syscall.O_RDWR|syscall.O_NONBLOCK|syscall.O_CLOEXEC, 0600)
d.uioFd, err = syscall.Open(fmt.Sprintf("/dev/%s", uio), syscall.O_RDWR|syscall.O_CLOEXEC, 0600)
if err != nil {
return err
}
bytes, err := ioutil.ReadFile(fmt.Sprintf("/sys/class/uio/%s/maps/map0/size", uio))
if err != nil {
return err
}
d.mapsize, err = strconv.ParseUint(strings.TrimRight(string(bytes), "\n"), 0, 64)
if err != nil {
return err
}
d.mmap, err = syscall.Mmap(d.uioFd, 0, int(d.mapsize), syscall.PROT_READ|syscall.PROT_WRITE, syscall.MAP_SHARED)
d.cmdTail = d.mbCmdTail()
d.debugPrintMb()
return err
}
func (d *Device) debugPrintMb() {
logrus.Debugf("Got a TCMU mailbox, version: %d\n", d.mbVersion())
logrus.Debugf("mapsize: %d\n", d.mapsize)
logrus.Debugf("mbFlags: %d\n", d.mbFlags())
logrus.Debugf("mbCmdrOffset: %d\n", d.mbCmdrOffset())
logrus.Debugf("mbCmdrSize: %d\n", d.mbCmdrSize())
logrus.Debugf("mbCmdHead: %d\n", d.mbCmdHead())
logrus.Debugf("mbCmdTail: %d\n", d.mbCmdTail())
}
func (d *Device) teardown() error {
dev := filepath.Join(d.devPath, d.scsi.VolumeName)
tpgtPath, _ := d.getSCSIPrefixAndWnn()
lunPath := d.getLunPath(tpgtPath)
/*
We're removing:
/sys/kernel/config/target/loopback/naa.<id>/tpgt_1/lun/lun_0/<volume name>
/sys/kernel/config/target/loopback/naa.<id>/tpgt_1/lun/lun_0
/sys/kernel/config/target/loopback/naa.<id>/tpgt_1
/sys/kernel/config/target/loopback/naa.<id>
/sys/kernel/config/target/core/user_42/<volume name>
*/
pathsToRemove := []string{
path.Join(lunPath, d.scsi.VolumeName),
lunPath,
tpgtPath,
path.Dir(tpgtPath),
path.Join(d.hbaDir, d.scsi.VolumeName),
}
for _, p := range pathsToRemove {
err := remove(p)
if err != nil {
return err
}
}
// Should be cleaned up automatically, but if it isn't remove it
if _, err := os.Stat(dev); err == nil {
err := remove(dev)
if err != nil {
return err
}
}
return nil
}
func removeAsync(path string, done chan<- error) {
logrus.Debugf("Removing: %s", path)
if err := os.Remove(path); err != nil && !os.IsNotExist(err) {
logrus.Errorf("Unable to remove: %v", path)
done <- err
}
logrus.Debugf("Removed: %s", path)
done <- nil
}
func remove(path string) error {
done := make(chan error)
go removeAsync(path, done)
select {
case err := <-done:
return err
case <-time.After(30 * time.Second):
return fmt.Errorf("Timeout trying to delete %s.", path)
}
}