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k8s_utils.go
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k8s_utils.go
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// Copyright 2017 The Kubernetes Authors.
// Copyright 2018 NetApp, Inc. All Rights Reserved.
package utils
import (
"bytes"
"fmt"
"io/ioutil"
"path/filepath"
"strconv"
"strings"
"os"
"syscall"
log "github.com/sirupsen/logrus"
)
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"
)
// This represents a single line in /proc/mounts or /etc/fstab.
type MountPoint struct {
Device string
Path string
Type string
Opts []string
Freq int
Pass int
}
// IsLikelyNotMountPoint determines if a directory is not a mountpoint.
func IsLikelyNotMountPoint(mountpoint string) (bool, error) {
stat, err := os.Stat(mountpoint)
if err != nil {
return true, err
}
rootStat, err := os.Lstat(filepath.Dir(strings.TrimSuffix(mountpoint, "/")))
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 GetDeviceNameFromMount(mountpath string) (string, int, error) {
fields := log.Fields{"mountpath": mountpath}
log.WithFields(fields).Debug(">>>> k8s_utils.GetDeviceNameFromMount")
defer log.WithFields(fields).Debug("<<<< k8s_utils.GetDeviceNameFromMount")
mps, err := listProcMounts(procMountsPath)
if err != nil {
return "", 0, err
}
// Find the device name.
// FIXME if multiple devices mounted on the same mount path, only the first one is returned
device := ""
// If mountPath is symlink, need get its target path.
slTarget, err := filepath.EvalSymlinks(mountpath)
if err != nil {
slTarget = mountpath
}
for i := range mps {
if mps[i].Path == slTarget {
device = mps[i].Device
break
}
}
// Find all references to the device.
refCount := 0
for i := range mps {
if mps[i].Device == device {
refCount++
}
}
log.WithFields(log.Fields{
"mountpath": mountpath,
"device": device,
"refCount": refCount,
}).Debug("Found device from mountpath.")
return device, refCount, nil
}
func listProcMounts(mountFilePath string) ([]MountPoint, error) {
content, err := ConsistentRead(mountFilePath, maxListTries)
if err != nil {
return nil, err
}
return parseProcMounts(content)
}
func parseProcMounts(content []byte) ([]MountPoint, error) {
out := make([]MountPoint, 0)
lines := strings.Split(string(content), "\n")
for _, line := range lines {
if line == "" {
// the last split() item is empty string following the last \n
continue
}
fields := strings.Fields(line)
if len(fields) != expectedNumFieldsPerLine {
return nil, fmt.Errorf("wrong number of fields (expected %d, got %d): %s", expectedNumFieldsPerLine, len(fields), line)
}
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 nil, err
}
mp.Freq = freq
pass, err := strconv.Atoi(fields[5])
if err != nil {
return nil, err
}
mp.Pass = pass
out = append(out, mp)
}
return out, nil
}
// ConsistentRead repeatedly reads a file until it gets the same content twice.
// This is useful when reading files in /proc that are larger than page size
// and kernel may modify them between individual read() syscalls.
func ConsistentRead(filename string, attempts int) ([]byte, error) {
oldContent, err := ioutil.ReadFile(filename)
if err != nil {
return nil, err
}
for i := 0; i < attempts; i++ {
newContent, err := ioutil.ReadFile(filename)
if err != nil {
return nil, err
}
if bytes.Compare(oldContent, newContent) == 0 {
return newContent, nil
}
// Files are different, continue reading
oldContent = newContent
}
return nil, fmt.Errorf("could not get consistent content of %s after %d attempts", filename, attempts)
}