As described in QubesOS/qubes-issues#3758, a VM may fail to start
if the volume is large. This because the whole volume is read to
ensure it's empty (=all zeros).
This changes limits the check to the first 1 GiB of the private
volume. As additional safety, a scan with blkid is done.
Fixes https://github.com/QubesOS/qubes-issues/issues/3758
(cherry picked from commit 8ff9cbe299)
When trying offline resize2fs, it require running fsck first, which
takes time, especially on large volumes. And in most cases, resize2fs
will notice that no action is needed - after wasting some time on fsck.
To remedy this, use resize2fs in online mode (on mounted filesystem).
And drop fsck call if it fails (filesystem is already mounted
read-write, running fsck isn't good idea).
But do not remove fsck call completely - still call it, but without '-f'
flag, so it run actual check only when really needed (unclean shutdown,
last check far in the past etc).
FixesQubesOS/qubes-issues#979FixesQubesOS/qubes-issues#2583
