github.com/xdlianrong208/docker-ce-comments@v17.12.1-ce-rc2+incompatible/components/engine/layer/mounted_layer.go (about)

     1  package layer
     2  
     3  import (
     4  	"io"
     5  
     6  	"github.com/docker/docker/pkg/archive"
     7  	"github.com/docker/docker/pkg/containerfs"
     8  )
     9  
    10  type mountedLayer struct {
    11  	name       string
    12  	mountID    string
    13  	initID     string
    14  	parent     *roLayer
    15  	path       string
    16  	layerStore *layerStore
    17  
    18  	references map[RWLayer]*referencedRWLayer
    19  }
    20  
    21  func (ml *mountedLayer) cacheParent() string {
    22  	if ml.initID != "" {
    23  		return ml.initID
    24  	}
    25  	if ml.parent != nil {
    26  		return ml.parent.cacheID
    27  	}
    28  	return ""
    29  }
    30  
    31  func (ml *mountedLayer) TarStream() (io.ReadCloser, error) {
    32  	return ml.layerStore.driver.Diff(ml.mountID, ml.cacheParent())
    33  }
    34  
    35  func (ml *mountedLayer) Name() string {
    36  	return ml.name
    37  }
    38  
    39  func (ml *mountedLayer) Parent() Layer {
    40  	if ml.parent != nil {
    41  		return ml.parent
    42  	}
    43  
    44  	// Return a nil interface instead of an interface wrapping a nil
    45  	// pointer.
    46  	return nil
    47  }
    48  
    49  func (ml *mountedLayer) Size() (int64, error) {
    50  	return ml.layerStore.driver.DiffSize(ml.mountID, ml.cacheParent())
    51  }
    52  
    53  func (ml *mountedLayer) Changes() ([]archive.Change, error) {
    54  	return ml.layerStore.driver.Changes(ml.mountID, ml.cacheParent())
    55  }
    56  
    57  func (ml *mountedLayer) Metadata() (map[string]string, error) {
    58  	return ml.layerStore.driver.GetMetadata(ml.mountID)
    59  }
    60  
    61  func (ml *mountedLayer) getReference() RWLayer {
    62  	ref := &referencedRWLayer{
    63  		mountedLayer: ml,
    64  	}
    65  	ml.references[ref] = ref
    66  
    67  	return ref
    68  }
    69  
    70  func (ml *mountedLayer) hasReferences() bool {
    71  	return len(ml.references) > 0
    72  }
    73  
    74  func (ml *mountedLayer) deleteReference(ref RWLayer) error {
    75  	if _, ok := ml.references[ref]; !ok {
    76  		return ErrLayerNotRetained
    77  	}
    78  	delete(ml.references, ref)
    79  	return nil
    80  }
    81  
    82  func (ml *mountedLayer) retakeReference(r RWLayer) {
    83  	if ref, ok := r.(*referencedRWLayer); ok {
    84  		ml.references[ref] = ref
    85  	}
    86  }
    87  
    88  type referencedRWLayer struct {
    89  	*mountedLayer
    90  }
    91  
    92  func (rl *referencedRWLayer) Mount(mountLabel string) (containerfs.ContainerFS, error) {
    93  	return rl.layerStore.driver.Get(rl.mountedLayer.mountID, mountLabel)
    94  }
    95  
    96  // Unmount decrements the activity count and unmounts the underlying layer
    97  // Callers should only call `Unmount` once per call to `Mount`, even on error.
    98  func (rl *referencedRWLayer) Unmount() error {
    99  	return rl.layerStore.driver.Put(rl.mountedLayer.mountID)
   100  }