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// Copyright (c) 2018-2020, Sylabs Inc. All rights reserved.
// This software is licensed under a 3-clause BSD license. Please consult the
// LICENSE.md file distributed with the sources of this project regarding your
// rights to use or distribute this software.
package overlay
import (
"fmt"
"path/filepath"
"strings"
"syscall"
"github.com/sylabs/singularity/v4/internal/pkg/util/fs/layout"
"github.com/sylabs/singularity/v4/internal/pkg/util/fs/mount"
"github.com/sylabs/singularity/v4/pkg/sylog"
)
const (
lowerDir = "/overlay-lowerdir"
)
// Overlay layer manager
type Overlay struct {
session *layout.Session
lowerDirs []string
upperDir string
workDir string
}
// New creates and returns an overlay layer manager
func New() *Overlay {
return &Overlay{}
}
// Add adds required directory in session layout
func (o *Overlay) Add(session *layout.Session, system *mount.System) error {
o.session = session
if err := o.session.AddDir(lowerDir); err != nil {
return err
}
if o.lowerDirs == nil {
o.lowerDirs = make([]string, 0)
}
path, _ := o.session.GetPath(lowerDir)
o.lowerDirs = append(o.lowerDirs, path)
return system.RunBeforeTag(mount.LayerTag, o.createOverlay)
}
// Dir returns absolute overlay directory within session
func (o *Overlay) Dir() string {
return lowerDir
}
func (o *Overlay) createOverlay(system *mount.System) error {
flags := uintptr(syscall.MS_NODEV)
o.lowerDirs = append(o.lowerDirs, o.session.RootFsPath())
lowerdir := strings.Join(o.lowerDirs, ":")
err := system.Points.AddOverlay(mount.LayerTag, o.session.FinalPath(), flags, lowerdir, o.upperDir, o.workDir)
if err != nil {
return err
}
points := system.Points.GetByTag(mount.RootfsTag)
if len(points) <= 0 {
return fmt.Errorf("no root fs image found")
}
return o.createLayer(points[0].Destination, system)
}
// AddLowerDir adds a lower directory to overlay mount
func (o *Overlay) AddLowerDir(path string) error {
o.lowerDirs = append([]string{path}, o.lowerDirs...)
return nil
}
// SetUpperDir sets upper directory to overlay mount
func (o *Overlay) SetUpperDir(path string) error {
if o.upperDir != "" {
return fmt.Errorf("upper directory was already set")
}
o.upperDir = path
return nil
}
// GetUpperDir returns upper directory path
func (o *Overlay) GetUpperDir() string {
return o.upperDir
}
// SetWorkDir sets work directory to overlay mount
func (o *Overlay) SetWorkDir(path string) error {
if o.workDir != "" {
return fmt.Errorf("upper directory was already set")
}
o.workDir = path
return nil
}
// GetWorkDir returns work directory path
func (o *Overlay) GetWorkDir() string {
return o.workDir
}
// createLayer creates overlay layer based on content of root filesystem
// given by rootFsPath
func (o *Overlay) createLayer(rootFsPath string, system *mount.System) error {
sessionDir := o.session.Path()
if sessionDir == "" {
return fmt.Errorf("can't determine session path")
}
for _, tag := range mount.GetTagList() {
for _, point := range system.Points.GetByTag(tag) {
flags, _ := mount.ConvertOptions(point.Options)
if flags&syscall.MS_REMOUNT != 0 {
continue
}
if strings.HasPrefix(point.Destination, sessionDir) {
continue
}
// get rid of symlinks and resolve the path within the
// rootfs path to not have false positive while creating
// the layer with calls below
dest := o.session.VFS.EvalRelative(point.Destination, rootFsPath)
// now we are (almost) sure that we will get path information
// for a path in the rootfs path and we would create the right
// destination in the layer
_, err := o.session.VFS.Stat(filepath.Join(rootFsPath, dest))
if err == nil {
continue
}
dest = filepath.Join(lowerDir, dest)
if _, err := o.session.GetPath(dest); err == nil {
continue
}
if point.Type != "" {
if err := o.session.AddDir(dest); err != nil {
return err
}
continue
}
fi, err := o.session.VFS.Stat(point.Source)
if err != nil {
sylog.Warningf("skipping mount of %s: %s", point.Source, err)
continue
}
// don't exist create it in overlay
if fi.IsDir() {
if err := o.session.AddDir(dest); err != nil {
return err
}
} else {
if err := o.session.AddFile(dest, nil); err != nil {
return err
}
}
}
}
return o.session.Update()
}
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