Relabel BTRFS Content on container Creation
Relabel BTRFS Content on container Creation

This change will allow us to run SELinux in a container with
BTRFS back end.  We continue to work on fixing the kernel/BTRFS
but this change will allow SELinux Security separation on BTRFS.

It basically relabels the content on container creation.

Just relabling -init directory in BTRFS use case. Everything looks like it
works. I don't believe tar/achive stores the SELinux labels, so we are good
as far as docker commit.

Tested Speed on startup with BTRFS on top of loopback directory. BTRFS
not on loopback should get even better perfomance on startup time.  The
more inodes inside of the container image will increase the relabel time.

This patch will give people who care more about security the option of
runnin BTRFS with SELinux.  Those who don't want to take the slow down
can disable SELinux either in individual containers or for all containers
by continuing to disable SELinux in the daemon.

Without relabel:

> time docker run --security-opt label:disable fedora echo test
test

real    0m0.918s
user    0m0.009s
sys    0m0.026s

With Relabel

test

real    0m1.942s
user    0m0.007s
sys    0m0.030s

Signed-off-by: Dan Walsh <7800de746fd39599bc46177380ea6aede7e31e16@redhat.com>

Signed-off-by: Dan Walsh <7800de746fd39599bc46177380ea6aede7e31e16@redhat.com>

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