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Fixing releaseableLayer handling of layer streams and mounts.

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releaseableLayer includes automatic handling for creating a read/write layer and mounting it on a call to Mount(), but then does not correspondingly unmount the layer before trying to delete it, which will fail for some graphdrivers. Commit on a releaseable layer also leaks the tarstream for the layer. To fix this, the stream close is deferred in Commit and releaseRWLayer now correctly handles unmounting the layer before trying to delete it.  In addition, the changes include better error handling in Release() to make sure that errors are returned to the caller for failures on read/write layers instead of being ignored.# Please enter the commit message for your changes. Lines starting

Signed-off-by: Stefan Wernli <swernli@ntdev.microsoft.com>
This commit is contained in:
Stefan Wernli 2017-07-19 14:35:23 -07:00
parent 4ac4c8ef4b
commit 1d457999c4
1 changed files with 33 additions and 3 deletions
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36
daemon/build.go
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@ -27,6 +27,7 @@ type releaseableLayer struct {
func (rl *releaseableLayer) Mount() (string, error) {
var err error
var mountPath string
var chainID layer.ChainID
if rl.roLayer != nil {
chainID = rl.roLayer.ChainID()
@ -38,7 +39,19 @@ func (rl *releaseableLayer) Mount() (string, error) {
return "", errors.Wrap(err, "failed to create rwlayer")
}
return rl.rwLayer.Mount("")
mountPath, err = rl.rwLayer.Mount("")
if err != nil {
// Clean up the layer if we fail to mount it here.
metadata, err := rl.layerStore.ReleaseRWLayer(rl.rwLayer)
layer.LogReleaseMetadata(metadata)
if err != nil {
logrus.Errorf("Failed to release RWLayer: %s", err)
}
rl.rwLayer = nil
return "", err
}
return mountPath, nil
}
func (rl *releaseableLayer) Commit(platform string) (builder.ReleaseableLayer, error) {
@ -51,6 +64,7 @@ func (rl *releaseableLayer) Commit(platform string) (builder.ReleaseableLayer, e
if err != nil {
return nil, err
}
defer stream.Close()
newLayer, err := rl.layerStore.Register(stream, chainID, layer.Platform(platform))
if err != nil {
@ -75,20 +89,32 @@ func (rl *releaseableLayer) Release() error {
if rl.released {
return nil
}
if err := rl.releaseRWLayer(); err != nil {
// Best effort attempt at releasing read-only layer before returning original error.
rl.releaseROLayer()
return err
}
if err := rl.releaseROLayer(); err != nil {
return err
}
rl.released = true
rl.releaseRWLayer()
return rl.releaseROLayer()
return nil
}
func (rl *releaseableLayer) releaseRWLayer() error {
if rl.rwLayer == nil {
return nil
}
if err := rl.rwLayer.Unmount(); err != nil {
logrus.Errorf("Failed to unmount RWLayer: %s", err)
return err
}
metadata, err := rl.layerStore.ReleaseRWLayer(rl.rwLayer)
layer.LogReleaseMetadata(metadata)
if err != nil {
logrus.Errorf("Failed to release RWLayer: %s", err)
}
rl.rwLayer = nil
return err
}
@ -98,6 +124,10 @@ func (rl *releaseableLayer) releaseROLayer() error {
}
metadata, err := rl.layerStore.Release(rl.roLayer)
layer.LogReleaseMetadata(metadata)
if err != nil {
logrus.Errorf("Failed to release ROLayer: %s", err)
}
rl.roLayer = nil
return err
}