110 lines
3.3 KiB
Go
110 lines
3.3 KiB
Go
package overlay
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import (
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"fmt"
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"os"
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"path/filepath"
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"strings"
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"syscall"
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"github.com/opencontainers/runtime-spec/specs-go"
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"github.com/opencontainers/selinux/go-selinux/label"
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"go.podman.io/storage/pkg/unshare"
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)
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// MountWithOptions creates ${contentDir}/merge, where ${contentDir} was
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// presumably created and returned by a call to TempDir(), and either mounts a
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// filesystem there and returns a mounts.Spec which bind-mounts the mountpoint
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// to ${dest}, or returns a mounts.Spec which mounts a filesystem at ${dest}.
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// Options allows the caller to configure a custom workdir and upperdir,
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// indicate whether or not the overlay should be read-only, and provide the
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// graph driver options that we'll search to determine whether or not we should
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// be using a mount helper (i.e., fuse-overlayfs).
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// This API is used by podman.
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func MountWithOptions(contentDir, source, dest string, opts *Options) (mount specs.Mount, Err error) {
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if opts == nil {
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opts = &Options{}
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}
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mergeDir := filepath.Join(contentDir, "merge")
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// Create overlay mount options for rw/ro.
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var overlayOptions string
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if opts.ReadOnly {
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// Read-only overlay mounts require two lower layers.
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lowerTwo := filepath.Join(contentDir, "lower")
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if err := os.Mkdir(lowerTwo, 0o755); err != nil {
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return mount, err
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}
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overlayOptions = fmt.Sprintf("lowerdir=%s:%s,private", escapeColon(source), lowerTwo)
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} else {
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// Read-write overlay mounts want a lower, upper and a work layer.
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workDir := filepath.Join(contentDir, "work")
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upperDir := filepath.Join(contentDir, "upper")
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if opts.WorkDirOptionFragment != "" && opts.UpperDirOptionFragment != "" {
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workDir = opts.WorkDirOptionFragment
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if !filepath.IsAbs(workDir) {
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workDir = filepath.Join(contentDir, workDir)
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}
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upperDir = opts.UpperDirOptionFragment
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if !filepath.IsAbs(upperDir) {
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upperDir = filepath.Join(contentDir, upperDir)
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}
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}
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st, err := os.Stat(source)
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if err != nil {
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return mount, err
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}
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if err := os.Chmod(upperDir, st.Mode()); err != nil {
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return mount, err
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}
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if stat, ok := st.Sys().(*syscall.Stat_t); ok {
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if err := os.Chown(upperDir, int(stat.Uid), int(stat.Gid)); err != nil {
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return mount, err
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}
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}
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overlayOptions = fmt.Sprintf("lowerdir=%s,upperdir=%s,workdir=%s,private", escapeColon(source), upperDir, workDir)
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}
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if opts.MountLabel != "" {
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overlayOptions = overlayOptions + "," + label.FormatMountLabel("", opts.MountLabel)
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}
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mountProgram := findMountProgram(opts.GraphOpts)
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if mountProgram != "" {
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if err := mountWithMountProgram(mountProgram, overlayOptions, mergeDir); err != nil {
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return mount, err
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}
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mount.Source = mergeDir
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mount.Destination = dest
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mount.Type = "bind"
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mount.Options = []string{"bind", "slave"}
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return mount, nil
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}
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if unshare.IsRootless() {
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// If a mount_program is not specified, fallback to try mounting native overlay.
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overlayOptions = fmt.Sprintf("%s,userxattr", overlayOptions)
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}
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mount.Source = mergeDir
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mount.Destination = dest
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mount.Type = "overlay"
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mount.Options = strings.Split(overlayOptions, ",")
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if opts.ForceMount {
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if err := mountNatively(overlayOptions, mergeDir); err != nil {
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return mount, err
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}
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mount.Source = mergeDir
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mount.Destination = dest
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mount.Type = "bind"
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mount.Options = []string{"bind", "slave"}
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return mount, nil
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}
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return mount, nil
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}
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