images: Pass context to commit related operations
**- What I did**
Context plumbing in preparation for implementing `docker commit` for containerd image store integration (will come soon).


daemon/images/image_commit.go
package images // import "github.com/docker/docker/daemon/images"

import (
	"encoding/json"
	"io"

	"github.com/docker/docker/api/types/backend"
	"github.com/docker/docker/image"
	"github.com/docker/docker/layer"
	"github.com/docker/docker/pkg/ioutils"
	"github.com/pkg/errors"
)

// CommitImage creates a new image from a commit config
func (i *ImageService) CommitImage(c backend.CommitConfig) (image.ID, error) {
	rwTar, err := exportContainerRw(i.layerStore, c.ContainerID, c.ContainerMountLabel)
	if err != nil {
		return "", err
	}
	defer func() {
		if rwTar != nil {
			rwTar.Close()
		}
	}()

	var parent *image.Image
	if c.ParentImageID == "" {
		parent = new(image.Image)
		parent.RootFS = image.NewRootFS()
	} else {
		parent, err = i.imageStore.Get(image.ID(c.ParentImageID))
		if err != nil {
			return "", err
		}
	}

	l, err := i.layerStore.Register(rwTar, parent.RootFS.ChainID())
	if err != nil {
		return "", err
	}
	defer layer.ReleaseAndLog(i.layerStore, l)

	cc := image.ChildConfig{
		ContainerID:     c.ContainerID,
		Author:          c.Author,
		Comment:         c.Comment,
		ContainerConfig: c.ContainerConfig,
		Config:          c.Config,
		DiffID:          l.DiffID(),
	}
	config, err := json.Marshal(image.NewChildImage(parent, cc, c.ContainerOS))
	if err != nil {
		return "", err
	}

	id, err := i.imageStore.Create(config)
	if err != nil {
		return "", err
	}

	if c.ParentImageID != "" {
		if err := i.imageStore.SetParent(id, image.ID(c.ParentImageID)); err != nil {
			return "", err
		}
	}
	return id, nil
}

func exportContainerRw(layerStore layer.Store, id, mountLabel string) (arch io.ReadCloser, err error) {
	rwlayer, err := layerStore.GetRWLayer(id)
	if err != nil {
		return nil, err
	}
	defer func() {
		if err != nil {
			layerStore.ReleaseRWLayer(rwlayer)
		}
	}()

	// TODO: this mount call is not necessary as we assume that TarStream() should
	// mount the layer if needed. But the Diff() function for windows requests that
	// the layer should be mounted when calling it. So we reserve this mount call
	// until windows driver can implement Diff() interface correctly.
	_, err = rwlayer.Mount(mountLabel)
	if err != nil {
		return nil, err
	}

	archive, err := rwlayer.TarStream()
	if err != nil {
		rwlayer.Unmount()
		return nil, err
	}
	return ioutils.NewReadCloserWrapper(archive, func() error {
			archive.Close()
			err = rwlayer.Unmount()
			layerStore.ReleaseRWLayer(rwlayer)
			return err
		}),
		nil
}

// CommitBuildStep is used by the builder to create an image for each step in
// the build.
//
// This method is different from CreateImageFromContainer:
//   - it doesn't attempt to validate container state
//   - it doesn't send a commit action to metrics
//   - it doesn't log a container commit event
//
// This is a temporary shim. Should be removed when builder stops using commit.
func (i *ImageService) CommitBuildStep(c backend.CommitConfig) (image.ID, error) {
	ctr := i.containers.Get(c.ContainerID)
	if ctr == nil {
		// TODO: use typed error
		return "", errors.Errorf("container not found: %s", c.ContainerID)
	}
	c.ContainerMountLabel = ctr.MountLabel
	c.ContainerOS = ctr.OS
	c.ParentImageID = string(ctr.ImageID)
	return i.CommitImage(c)
}

package images // import "github.com/docker/docker/daemon/images"

import (
	"context"
	"encoding/json"
	"io"

	"github.com/docker/docker/api/types/backend"
	"github.com/docker/docker/image"
	"github.com/docker/docker/layer"
	"github.com/docker/docker/pkg/ioutils"
	"github.com/pkg/errors"
)

// CommitImage creates a new image from a commit config
func (i *ImageService) CommitImage(ctx context.Context, c backend.CommitConfig) (image.ID, error) {
	if err := ctx.Err(); err != nil {
		return "", err
	}

	rwTar, err := exportContainerRw(i.layerStore, c.ContainerID, c.ContainerMountLabel)
	if err != nil {
		return "", err
	}
	defer func() {
		if rwTar != nil {
			rwTar.Close()
		}
	}()

	var parent *image.Image
	if c.ParentImageID == "" {
		parent = new(image.Image)
		parent.RootFS = image.NewRootFS()
	} else {
		parent, err = i.imageStore.Get(image.ID(c.ParentImageID))
		if err != nil {
			return "", err
		}
	}

	l, err := i.layerStore.Register(rwTar, parent.RootFS.ChainID())
	if err != nil {
		return "", err
	}
	defer layer.ReleaseAndLog(i.layerStore, l)

	cc := image.ChildConfig{
		ContainerID:     c.ContainerID,
		Author:          c.Author,
		Comment:         c.Comment,
		ContainerConfig: c.ContainerConfig,
		Config:          c.Config,
		DiffID:          l.DiffID(),
	}
	config, err := json.Marshal(image.NewChildImage(parent, cc, c.ContainerOS))
	if err != nil {
		return "", err
	}

	id, err := i.imageStore.Create(config)
	if err != nil {
		return "", err
	}

	if c.ParentImageID != "" {
		if err := i.imageStore.SetParent(id, image.ID(c.ParentImageID)); err != nil {
			return "", err
		}
	}
	return id, nil
}

func exportContainerRw(layerStore layer.Store, id, mountLabel string) (arch io.ReadCloser, err error) {
	rwlayer, err := layerStore.GetRWLayer(id)
	if err != nil {
		return nil, err
	}
	defer func() {
		if err != nil {
			layerStore.ReleaseRWLayer(rwlayer)
		}
	}()

	// TODO: this mount call is not necessary as we assume that TarStream() should
	// mount the layer if needed. But the Diff() function for windows requests that
	// the layer should be mounted when calling it. So we reserve this mount call
	// until windows driver can implement Diff() interface correctly.
	_, err = rwlayer.Mount(mountLabel)
	if err != nil {
		return nil, err
	}

	archive, err := rwlayer.TarStream()
	if err != nil {
		rwlayer.Unmount()
		return nil, err
	}
	return ioutils.NewReadCloserWrapper(archive, func() error {
			archive.Close()
			err = rwlayer.Unmount()
			layerStore.ReleaseRWLayer(rwlayer)
			return err
		}),
		nil
}

// CommitBuildStep is used by the builder to create an image for each step in
// the build.
//
// This method is different from CreateImageFromContainer:
//   - it doesn't attempt to validate container state
//   - it doesn't send a commit action to metrics
//   - it doesn't log a container commit event
//
// This is a temporary shim. Should be removed when builder stops using commit.
func (i *ImageService) CommitBuildStep(ctx context.Context, c backend.CommitConfig) (image.ID, error) {
	ctr := i.containers.Get(c.ContainerID)
	if ctr == nil {
		// TODO: use typed error
		return "", errors.Errorf("container not found: %s", c.ContainerID)
	}
	c.ContainerMountLabel = ctr.MountLabel
	c.ContainerOS = ctr.OS
	c.ParentImageID = string(ctr.ImageID)
	return i.CommitImage(ctx, c)
}

For others reviewing; looks like there's probably no need to pass the context further down here (or at least, not in the current implementation); https://github.com/moby/moby/blob/219ced474d8bcb9cbd399a6ab6ec17f178fe3306/container/memory_store.go#L29-L35