Switch block CIM snapshotter and diff plugin init checks from
IsBlockCimSupported() to IsBlockCimWriteSupported() to allow plugins
to load when the CimWriter.dll is available, even on OS builds
without native block CIM support.
Signed-off-by: Maksim An <maksiman@microsoft.com>
This change updates an incorrect default config value for the block CIM
snapshotter. The `ntfsFormat` should always be false for the block CIM
snapshotter. If the scratch needs to be formatted with NTFS, a format
option named `WithNTFSFormat` can be provided.
Signed-off-by: Amit Barve <ambarve@microsoft.com>
Add new snapshotter & differ plugins that can leverage the block CIM layer writers to
store pulled/imported images in the block CIM format.
Signed-off-by: Amit Barve <ambarve@microsoft.com>
Adds a new diff plugin that can import image layers in the block CIM format using the new
block CIM layer writer added in hcsshim repo.
This commit also makes another important change in the way a diff is applied when using
CimFS based layer writers. Currently, the diff plugins call archive.Apply to apply a diff
and pass a function (that can actually apply the diff) as an argument (via
archive.ApplyOptions). This allows the callers to call archive.Apply with either a custom
applier function or if the caller doesn't pass such a function archive.Apply uses the
default naive diff applier.
However, there is drawback to this approach. The applier function passed to the
`archive.Apply` call needs to follow a specific signature. This signature expects it that
all parent layers are represented as an array of strings. In cases like CimFS, we can't
easily represent a set of layers as strings (unless we encode extra data in those strings
in a hacky way). To get around this problem, the diff plugins for CimFS based layers, skip
the archive.Apply call and directly call the layer writer instead.
Signed-off-by: Amit Barve <ambarve@microsoft.com>
hcsshim recently [updated](microsoft/hcsshim@1d406d0) the interface of APIs that are used
for importing OCI layers. It now expects that the CimFS snapshotter mounts contain the
full cim paths for parent layers. This change updates the cimfs differ & snapshotter to
use that new interface.
Signed-off-by: Amit Barve <ambarve@microsoft.com>
CimFS layers don't need to create a new scratch VHD per image. The scratch VHDs used with CimFS are empty so
we can just create one base VHD and one differencing VHD and copy it for every scratch snapshot.
(Note that UVM VHDs are still unique per image because the VHD information is embedded in the UVM BCD during
import)
Signed-off-by: Amit Barve <ambarve@microsoft.com>
Sebastiaan van Stijn