This implements the new Put() operation such that
Get()/Put() maintains a refcount for each ID, mounting
only on first Get() and unmounting on the last Get().
This means we avoid littering the system with lots of mounts
and active devicemapper devices and free resources related
to them.
Docker-DCO-1.1-Signed-off-by: Alexander Larsson <alexl@redhat.com> (github: alexlarsson)
asdfljk
This makes all users of Put() have a corresponding call
to Get() which means we will be able to track whether
any particular ID is in use and if not unmount it.
Docker-DCO-1.1-Signed-off-by: Alexander Larsson <alexl@redhat.com> (github: alexlarsson)
This moves Driver.Size() to Differ.DiffSize(), removing the empty
implementations in devmapper and dummy, and renaming the one in aufs.
Then we fall back to a container.Changes() implementation in the non-aufs
case.
We place the actual image/containers in the "rootfs" directory, which
allows us to have other data in the toplevel directory in the mount.
For starters, this means the "lost+found" directory from mkfs will
not always be in your container/image.
Secondly, we can create a file "id" in the toplevel dir which is not
visible from the container. This is useful because it allows us to map
back from the device fs to the container if something goes wrong with
the devicemapper metadata.
