See
https://github.com/QubesOS/qubes-core-agent-linux/pull/146#discussion_r238080117
for details; but tl;dr:
* Journal size is 64M
* Inode table is 256 bytes * 643376 inodes allocated = ~157M
* Reserved GDT blocks take up 1024 blocks * 4096 byte block size = 4M
* Fixed-size parts of the filesystem probably take up another MB or
two
These actually adds up to more than the 222M number used in this
commit. But it seems _about_ right, so just Ship It(tm).
This reverts commit 8000e76d43, because
as @marmarek pointed out, the original was correct and I totally
misread. The check in question is checking whether to _abort_, not
whether to continue. So we want to check if the block device size is
_less_ than the filesystem + margin, not more.
ReopensQubesOS/qubes-issues#4553
If xvda is not partitioned, checking size of device mounted as root dev
doesn't detect xvda resize - it will have the new size, while the fs on
it not. Change to checking actual filesystem size.
Also, improve log message to include the size.
FixesQubesOS/qubes-issues#4274
