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Merged
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Jan 25, 2025
Merged

pkg/overlay: cleanups #5927

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53 changes: 30 additions & 23 deletions pkg/overlay/overlay.go
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Original file line number Diff line number Diff line change
Expand Up @@ -17,9 +17,7 @@ import (
"github.com/sirupsen/logrus"
)

// Options type holds various configuration options for overlay
// MountWithOptions accepts following type so it is easier to specify
// more verbose configuration for overlay mount.
// Options for MountWithOptions().
type Options struct {
// The Upper directory is normally writable layer in an overlay mount.
// Note!! : Following API does not handles escaping or validates correctness of the values
Expand All @@ -41,13 +39,13 @@ type Options struct {
// TODO: Should we address above comment and handle escaping of metacharacters like
// `comma`, `backslash` ,`colon` and any other special characters
WorkDirOptionFragment string
// Graph options relayed from podman, will be responsible for choosing mount program
// Graph options being used by the caller, will be searched when choosing mount program
GraphOpts []string
// Mark if following overlay is read only
ReadOnly bool
// RootUID is not used yet but keeping it here for legacy reasons.
// Deprecated: RootUID is not used
RootUID int
// RootGID is not used yet but keeping it here for legacy reasons.
// Deprecated: RootGID is not used
RootGID int
// Force overlay mounting and return a bind mount, rather than
// attempting to optimize by having the runtime actually mount and
Expand All @@ -57,7 +55,10 @@ type Options struct {
MountLabel string
}

// TempDir generates an overlay Temp directory in the container content
// TempDir generates a uniquely-named directory under ${containerDir}/overlay
// which can be used as a parent directory for the upper and working
// directories for an overlay mount, creates "upper" and "work" directories
// beneath it, and then returns the path of the new directory.
func TempDir(containerDir string, rootUID, rootGID int) (string, error) {
contentDir := filepath.Join(containerDir, "overlay")
if err := idtools.MkdirAllAs(contentDir, 0o700, rootUID, rootGID); err != nil {
Expand All @@ -69,7 +70,7 @@ func TempDir(containerDir string, rootUID, rootGID int) (string, error) {
return "", fmt.Errorf("failed to create the overlay tmpdir in %s directory: %w", contentDir, err)
}

return generateOverlayStructure(contentDir, rootUID, rootGID)
return contentDir, generateOverlayStructure(contentDir, rootUID, rootGID)
}

// GenerateStructure generates an overlay directory structure for container content
Expand All @@ -79,25 +80,24 @@ func GenerateStructure(containerDir, containerID, name string, rootUID, rootGID
return "", fmt.Errorf("failed to create the overlay %s directory: %w", contentDir, err)
}

return generateOverlayStructure(contentDir, rootUID, rootGID)
return contentDir, generateOverlayStructure(contentDir, rootUID, rootGID)
}

// generateOverlayStructure generates upper, work and merge directory structure for overlay directory
func generateOverlayStructure(containerDir string, rootUID, rootGID int) (string, error) {
// generateOverlayStructure generates upper, work and merge directories under the specified directory
func generateOverlayStructure(containerDir string, rootUID, rootGID int) error {
upperDir := filepath.Join(containerDir, "upper")
workDir := filepath.Join(containerDir, "work")
if err := idtools.MkdirAllAs(upperDir, 0o700, rootUID, rootGID); err != nil {
return "", fmt.Errorf("failed to create the overlay %s directory: %w", upperDir, err)
return fmt.Errorf("creating overlay upper directory %s: %w", upperDir, err)
}
if err := idtools.MkdirAllAs(workDir, 0o700, rootUID, rootGID); err != nil {
return "", fmt.Errorf("failed to create the overlay %s directory: %w", workDir, err)
return fmt.Errorf("creating overlay work directory %s: %w", workDir, err)
}
mergeDir := filepath.Join(containerDir, "merge")
if err := idtools.MkdirAllAs(mergeDir, 0o700, rootUID, rootGID); err != nil {
return "", fmt.Errorf("failed to create the overlay %s directory: %w", mergeDir, err)
return fmt.Errorf("creating overlay merge directory %s: %w", mergeDir, err)
}

return containerDir, nil
return nil
}

// Mount creates a subdir of the contentDir based on the source directory
Expand Down Expand Up @@ -140,8 +140,8 @@ func findMountProgram(graphOptions []string) string {
return ""
}

// mountWithMountProgram mount an overlay at mergeDir using the specified mount program
// and overlay options.
// mountWithMountProgram mounts an overlay at mergeDir using the specified
// mount program and overlay options.
func mountWithMountProgram(mountProgram, overlayOptions, mergeDir string) error {
cmd := exec.Command(mountProgram, "-o", overlayOptions, mergeDir)

Expand All @@ -162,8 +162,9 @@ func escapeColon(source string) string {
return strings.ReplaceAll(source, ":", "\\:")
}

// RemoveTemp removes temporary mountpoint and all content from its parent
// directory
// RemoveTemp unmounts a filesystem mounted at ${contentDir}/merge, and then
// removes ${contentDir}, which is typically a path returned by TempDir(),
// along with any contents it might still have.
func RemoveTemp(contentDir string) error {
if err := Unmount(contentDir); err != nil {
return err
Expand All @@ -172,7 +173,9 @@ func RemoveTemp(contentDir string) error {
return os.RemoveAll(contentDir)
}

// Unmount the overlay mountpoint
// Unmount the overlay mountpoint at ${contentDir}/merge, where ${contentDir}
// is typically a path returned by TempDir(). The mountpoint itself is left
// unmodified.
func Unmount(contentDir string) error {
mergeDir := filepath.Join(contentDir, "merge")

Expand All @@ -198,6 +201,8 @@ func Unmount(contentDir string) error {
return nil
}

// recreate removes a directory tree and then recreates the top of that tree
// with the same mode and ownership.
func recreate(contentDir string) error {
st, err := system.Stat(contentDir)
if err != nil {
Expand Down Expand Up @@ -228,8 +233,10 @@ func CleanupMount(contentDir string) (Err error) {
return nil
}

// CleanupContent removes all temporary mountpoint and all content from
// directory
// CleanupContent removes every temporary mountpoint created under
// ${containerDir}/overlay as a result of however many calls to TempDir(),
// roughly equivalent to calling RemoveTemp() for each of the directories whose
// paths it returned, and then removes ${containerDir} itself.
func CleanupContent(containerDir string) (Err error) {
contentDir := filepath.Join(containerDir, "overlay")

Expand Down
10 changes: 5 additions & 5 deletions pkg/overlay/overlay_freebsd.go
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Original file line number Diff line number Diff line change
Expand Up @@ -12,11 +12,11 @@ import (
"github.com/opencontainers/runtime-spec/specs-go"
)

// MountWithOptions creates a subdir of the contentDir based on the source directory
// from the source system. It then mounts up the source directory on to the
// generated mount point and returns the mount point to the caller.
// But allows api to set custom workdir, upperdir and other overlay options
// Following API is being used by podman at the moment
// MountWithOptions returns a specs.Mount which makes the contents of ${source}
// visible at ${dest} in the container.
// Options allows the caller to configure whether or not the mount should be
// read-only.
// This API is used by podman.
func MountWithOptions(contentDir, source, dest string, opts *Options) (mount specs.Mount, Err error) {
if opts == nil {
opts = &Options{}
Expand Down
24 changes: 17 additions & 7 deletions pkg/overlay/overlay_linux.go
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Original file line number Diff line number Diff line change
Expand Up @@ -12,11 +12,15 @@ import (
"github.com/opencontainers/selinux/go-selinux/label"
)

// MountWithOptions creates a subdir of the contentDir based on the source directory
// from the source system. It then mounts up the source directory on to the
// generated mount point and returns the mount point to the caller.
// But allows api to set custom workdir, upperdir and other overlay options
// Following API is being used by podman at the moment
// MountWithOptions creates ${contentDir}/merge, where ${contentDir} was
// presumably created and returned by a call to TempDir(), and either mounts a
// filesystem there and returns a mounts.Spec which bind-mounts the mountpoint
// to ${dest}, or returns a mounts.Spec which mounts a filesystem at ${dest}.
// Options allows the caller to configure a custom workdir and upperdir,
// indicate whether or not the overlay should be read-only, and provide the
// graph driver options that we'll search to determine whether or not we should
// be using a mount helper (i.e., fuse-overlayfs).
// This API is used by podman.
func MountWithOptions(contentDir, source, dest string, opts *Options) (mount specs.Mount, Err error) {
if opts == nil {
opts = &Options{}
Expand All @@ -26,7 +30,7 @@ func MountWithOptions(contentDir, source, dest string, opts *Options) (mount spe
// Create overlay mount options for rw/ro.
var overlayOptions string
if opts.ReadOnly {
// Read-only overlay mounts require two lower layer.
// Read-only overlay mounts require two lower layers.
lowerTwo := filepath.Join(contentDir, "lower")
if err := os.Mkdir(lowerTwo, 0o755); err != nil {
return mount, err
Expand All @@ -39,7 +43,13 @@ func MountWithOptions(contentDir, source, dest string, opts *Options) (mount spe

if opts.WorkDirOptionFragment != "" && opts.UpperDirOptionFragment != "" {
workDir = opts.WorkDirOptionFragment
if !filepath.IsAbs(workDir) {
workDir = filepath.Join(contentDir, workDir)
}
upperDir = opts.UpperDirOptionFragment
if !filepath.IsAbs(upperDir) {
upperDir = filepath.Join(contentDir, upperDir)
}
}

st, err := os.Stat(source)
Expand Down Expand Up @@ -74,7 +84,7 @@ func MountWithOptions(contentDir, source, dest string, opts *Options) (mount spe
}

if unshare.IsRootless() {
/* If a mount_program is not specified, fallback to try mounting native overlay. */
// If a mount_program is not specified, fallback to try mounting native overlay.
overlayOptions = fmt.Sprintf("%s,userxattr", overlayOptions)
}

Expand Down