This makes the device mapper not zero out blocks allocated on the
thinp device. This is safe in our use case, as we access the device
via a filesystem that doesn't leak any uninitialized data to userspace.
This partially helps with https://github.com/dotcloud/docker/issues/3280
and should generally improve preformance on the devicemapper backend.
Docker-DCO-1.1-Signed-off-by: Alexander Larsson <alexl@redhat.com> (github: alexlarsson)
Upstream-commit: 695719b29a6311a56faae0c6ed3c985b7a75add0
Component: engine
This works around the fact that deleting a device in a thin pool
doesn't discard the free space. Unfortunately even this is not perfect,
as it seems discards are respected only for blocks that has never been
shared in the thin device code. However, this has been fixed in the
upstream kernel device-mapper tree:
http://git.kernel.org/cgit/linux/kernel/git/device-mapper/linux-dm.git/commit/?h=for-next&id=0ab1c92ff748b745c1ed7cde31bb37ad2c5f901a
When this hits the kernel I belive this will fully return space
for removed images/containers to the host FS. For now it only
helps partially (which is better than nothing).
Docker-DCO-1.1-Signed-off-by: Alexander Larsson <alexl@redhat.com> (github: alexlarsson)
Upstream-commit: 93e120e7d67313086d8bdecbcb57ea68958f91e4
Component: engine
