As per the thin provisioning docs for creating the pool:
$data_block_size gives the smallest unit of disk space that can be
allocated at a time expressed in units of 512-byte sectors.
$data_block_size must be between 128 (64KB) and 2097152 (1GB) and a
multiple of 128 (64KB). $data_block_size cannot be changed after the
thin-pool is created. People primarily interested in thin provisioning
may want to use a value such as 1024 (512KB). People doing lots of
snapshotting may want a smaller value such as 128 (64KB).
The switch from 512 (which we used before) to 128 (recommended above
for lots of snapshoting) means a simple container creation (based on the
mattdm/fedora:f19 image) adds 1 MB of diskspace rather than 3.6.
This seems more in tune with how docker is typically used.
Upstream-commit: 8abcc8e713fdf6229d65dec23e6e104f8040d704
Component: engine
This separates out the DeviceSet logic a bit better from the raw
device mapper operations.
devicemapper: Serialize addess to the devicemapper deviceset
This code is not safe to run in multiple threads at the same time,
and neither is libdevmapper.
DeviceMapper: Move deactivate into UnmountDevice
This way the deactivate is atomic wrt othe device mapper operations
and will not fail with EBUSY if someone else starts a devicemapper
operation inbetween unmount and deactivate.
devmapper: Fix loopback mounting regression
Some changes were added to attach_loop_device which added
a perror() in a place that caused it to override errno so that
a later errno != EBUSY failed. This fixes that and cleans up
the error reporting a bit.
devmapper: Build on old kernels without LOOP_CTL_GET_FREE define
Upstream-commit: c77697a45ca615f66351a7363e93c3903e92553f
Component: engine
Typo in the loop-control code made it always fall back to the
old method of opening loopback devices.
Upstream-commit: cc28829429f5f11da287ecb75ee5b3e5f05d31ad
Component: engine
