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119 lines
3.0 KiB
Go
119 lines
3.0 KiB
Go
//go:build linux
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// +build linux
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/*
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Copyright The containerd Authors.
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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 loopback
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import (
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"bytes"
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"errors"
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"fmt"
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"os"
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"os/exec"
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"strings"
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"syscall"
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"github.com/containerd/log"
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)
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// New creates a loopback device
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func New(size int64) (*Loopback, error) {
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// create temporary file for the disk image
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file, err := os.CreateTemp("", "containerd-test-loopback")
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if err != nil {
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return nil, fmt.Errorf("could not create temporary file for loopback: %w", err)
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}
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if err := file.Truncate(size); err != nil {
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file.Close()
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os.Remove(file.Name())
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return nil, fmt.Errorf("failed to resize temp file: %w", err)
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}
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file.Close()
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// create device
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losetup := exec.Command("losetup", "--find", "--show", file.Name())
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var stdout, stderr bytes.Buffer
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losetup.Stdout = &stdout
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losetup.Stderr = &stderr
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if err := losetup.Run(); err != nil {
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os.Remove(file.Name())
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return nil, fmt.Errorf("loopback setup failed (%v): stdout=%q, stderr=%q: %w", losetup.Args, stdout.String(), stderr.String(), err)
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}
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deviceName := strings.TrimSpace(stdout.String())
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log.L.Debugf("Created loop device %s (using %s)", deviceName, file.Name())
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cleanup := func() error {
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// detach device
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log.L.Debugf("Removing loop device %s", deviceName)
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losetup := exec.Command("losetup", "--detach", deviceName)
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if out, err := losetup.CombinedOutput(); err != nil {
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return fmt.Errorf("Could not remove loop device %s (%v): %q: %w", deviceName, losetup.Args, string(out), err)
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}
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// remove file
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log.L.Debugf("Removing temporary file %s", file.Name())
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return os.Remove(file.Name())
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}
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l := Loopback{
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File: file.Name(),
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Device: deviceName,
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close: cleanup,
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}
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return &l, nil
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}
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// Loopback device
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type Loopback struct {
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// File is the underlying sparse file
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File string
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// Device is /dev/loopX
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Device string
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close func() error
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}
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// SoftSize returns st_size
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func (l *Loopback) SoftSize() (int64, error) {
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st, err := os.Stat(l.File)
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if err != nil {
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return 0, err
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}
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return st.Size(), nil
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}
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// HardSize returns st_blocks * 512; see stat(2)
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func (l *Loopback) HardSize() (int64, error) {
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st, err := os.Stat(l.File)
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if err != nil {
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return 0, err
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}
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st2, ok := st.Sys().(*syscall.Stat_t)
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if !ok {
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return 0, errors.New("st.Sys() is not a *syscall.Stat_t")
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}
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// NOTE: st_blocks has nothing to do with st_blksize; see stat(2)
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return st2.Blocks * 512, nil
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}
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// Close detaches the device and removes the underlying file
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func (l *Loopback) Close() error {
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return l.close()
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}
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