* Jeff Layton:

To do this we'd need 2 64-bit fields in the on-disk and in-memory 
superblocks for ext4, xfs and btrfs. On the first mount after a crash,
the filesystem would need to bump s_version_max by the significant
increment (2^40 bits or whatever). On a "clean" mount, it wouldn't need
to do that.

Would there be a way to ensure that the new s_version_max value has made
it to disk? Bumping it by a large value and hoping for the best might be
ok for most cases, but there are always outliers, so it might be
worthwhile to make an i_version increment wait on that if necessary. 

How common are unclean shutdowns in practice?  Do ex64/XFS/btrfs keep
counters in the superblocks for journal replays that can be read easily?

Several useful i_version applications could be negatively impacted by
frequent i_version invalidation.

Thanks,
Florian