128 lines
3.0 KiB
Go
128 lines
3.0 KiB
Go
// +build linux
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/*
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Copyright 2014 Google Inc. All rights reserved.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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package mount
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import (
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"bufio"
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"fmt"
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"hash/adler32"
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"io"
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"os"
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"strconv"
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"strings"
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"syscall"
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"github.com/golang/glog"
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)
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const FlagBind = syscall.MS_BIND
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const FlagReadOnly = syscall.MS_RDONLY
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type Mounter struct{}
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// Wraps syscall.Mount()
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func (mounter *Mounter) Mount(source string, target string, fstype string, flags uintptr, data string) error {
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glog.V(5).Infof("Mounting %s %s %s %d %s", source, target, fstype, flags, data)
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return syscall.Mount(source, target, fstype, flags, data)
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}
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// Wraps syscall.Unmount()
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func (mounter *Mounter) Unmount(target string, flags int) error {
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return syscall.Unmount(target, flags)
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}
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// How many times to retry for a consistent read of /proc/mounts.
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const maxListTries = 3
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func (*Mounter) List() ([]MountPoint, error) {
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hash1, err := readProcMounts(nil)
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if err != nil {
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return nil, err
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}
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for i := 0; i < maxListTries; i++ {
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mps := []MountPoint{}
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hash2, err := readProcMounts(&mps)
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if err != nil {
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return nil, err
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}
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if hash1 == hash2 {
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// Success
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return mps, nil
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}
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hash1 = hash2
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}
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return nil, fmt.Errorf("failed to get a consistent snapshot of /proc/mounts after %d tries", maxListTries)
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}
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// As per the fstab man page.
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const expectedNumFieldsPerLine = 6
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// Read /proc/mounts and produces a hash of the contents. If the out argument
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// is not nil, this fills it with MountPoint structs.
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func readProcMounts(out *[]MountPoint) (uint32, error) {
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file, err := os.Open("/proc/mounts")
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if err != nil {
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return 0, err
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}
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defer file.Close()
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return readProcMountsFrom(file, out)
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}
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func readProcMountsFrom(file io.Reader, out *[]MountPoint) (uint32, error) {
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hash := adler32.New()
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scanner := bufio.NewReader(file)
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for {
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line, err := scanner.ReadString('\n')
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if err == io.EOF {
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break
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}
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fields := strings.Fields(line)
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if len(fields) != expectedNumFieldsPerLine {
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return 0, fmt.Errorf("wrong number of fields (expected %d, got %d): %s", expectedNumFieldsPerLine, len(fields), line)
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}
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fmt.Fprintf(hash, "%s", line)
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if out != nil {
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mp := MountPoint{
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Device: fields[0],
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Path: fields[1],
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Type: fields[2],
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Opts: strings.Split(fields[3], ","),
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}
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freq, err := strconv.Atoi(fields[4])
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if err != nil {
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return 0, err
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}
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mp.Freq = freq
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pass, err := strconv.Atoi(fields[5])
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if err != nil {
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return 0, err
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}
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mp.Pass = pass
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*out = append(*out, mp)
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}
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}
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return hash.Sum32(), nil
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}
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