package overlay

import "gvisor.dev/gvisor/pkg/sentry/fsimpl/overlay"

Package overlay provides an overlay filesystem implementation, which synthesizes a filesystem by composing one or more immutable filesystems ("lower layers") with an optional mutable filesystem ("upper layer").

Lock order:

directoryFD.mu / regularFileFD.mu
	filesystem.renameMu
		dentry.dirMu
	    dentry.copyMu
	      filesystem.devMu
	      *** "memmap.Mappable/MappingIdentity locks" below this point
	      dentry.mapsMu
	        *** "memmap.Mappable locks taken by Translate" below this point
	        dentry.dataMu
	      filesystem.ancestryMu

Locking dentry.dirMu in multiple dentries requires that parent dentries are locked before child dentries, and that filesystem.renameMu is locked to stabilize this relationship.

Index ¶

• Constants
• func CreateWhiteout(ctx context.Context, vfsObj *vfs.VirtualFilesystem, creds *auth.Credentials, pop *vfs.PathOperation) error
• type FilesystemOptions
• type FilesystemType
• func (fstype FilesystemType) GetFilesystem(ctx context.Context, vfsObj *vfs.VirtualFilesystem, creds *auth.Credentials, source string, opts vfs.GetFilesystemOptions) (*vfs.Filesystem, *vfs.Dentry, error)
• func (FilesystemType) Name() string
• func (FilesystemType) Release(ctx context.Context)

Constants ¶

const Name = "overlay"

Name is the default filesystem name.

Functions ¶

func CreateWhiteout ¶

func CreateWhiteout(ctx context.Context, vfsObj *vfs.VirtualFilesystem, creds *auth.Credentials, pop *vfs.PathOperation) error

CreateWhiteout creates a whiteout at pop. Whiteouts are created with character devices with device ID = 0.

Preconditions: pop's parent directory has been copied up.

Types ¶

type FilesystemOptions ¶

type FilesystemOptions struct {

	// If UpperRoot.Ok(), it is the root of the writable upper layer of the
	// overlay.
	UpperRoot vfs.VirtualDentry

	// LowerRoots contains the roots of the immutable lower layers of the
	// overlay. LowerRoots is immutable.
	LowerRoots []vfs.VirtualDentry
}

FilesystemOptions may be passed as vfs.GetFilesystemOptions.InternalData to FilesystemType.GetFilesystem.

+stateify savable

type FilesystemType ¶

type FilesystemType struct{}

FilesystemType implements vfs.FilesystemType.

+stateify savable

func (FilesystemType) GetFilesystem ¶

func (fstype FilesystemType) GetFilesystem(ctx context.Context, vfsObj *vfs.VirtualFilesystem, creds *auth.Credentials, source string, opts vfs.GetFilesystemOptions) (*vfs.Filesystem, *vfs.Dentry, error)

GetFilesystem implements vfs.FilesystemType.GetFilesystem.

func (FilesystemType) Name ¶

func (FilesystemType) Name() string

Name implements vfs.FilesystemType.Name.

func (FilesystemType) Release ¶

func (FilesystemType) Release(ctx context.Context)

Release implements FilesystemType.Release.

Source Files ¶

copy_up.go directory.go filesystem.go overlay.go regular_file.go save_restore.go