[EXT4 set 4][PATCH 1/5] i_version:64 bit inode version

[Andrew Morton]

On Tue, 10 Jul 2007 22:09:08 -0400 Mingming Cao <cmm at us.ibm.com> wrote:

> David Chinneer pointed that we need to journal the version number
> updates together with the operations that causes the change of the inode
> version number, in order to survive server crashes so clients won't see
> the counter go backwards.
> 
> So increment i_version in fs code is probably the place to ensure the
> inode version changes are stored to disk. It's seems update the ext4
> inode version in every ext4_mark_inode_dirty() is the easiest way.

That still makes us dependent upon _something_ changing the inode.  For
overwrites the only something is mtime.

If we don't want to have a peculiar dependency upon s_time_gran=1e9 (and
I don't think we do) then I guess we'll need new code in or around
file_update_time() to do this.