Use a smaller filesize on systems that have a default 4KB pagesize.
This is because mkfs.btrfs uses the default system pagesize as blocksize
when creating a device, so if the pagesize is larger, then the file needs
to be larger as well. This larger filesize is needed specifically for
systems where 64KB is default, such as ppc64le.
Signed-off-by: Christopher Jones <tophj@linux.vnet.ibm.com>
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