Re: [RFC][PATCH] xfs: extended timestamp range

[Dave Chinner <david@fromorbit.com>]

On Mon, Nov 18, 2019 at 06:52:39AM +0200, Amir Goldstein wrote:
> > >
> > > I wonder if your version has struct xfs_dinode_v3 or it could avoid it.
> > > There is a benefit in terms of code complexity and test coverage
> > > to keep the only difference between inode versions in the on-disk
> > > parsers, while reading into the same struct, the same way as
> > > old inode versions are read into struct xfs_dinode.
> > >
> > > Oh well, I can wait for tomorrow to see the polished version :-)
> >
> > Well now we noticed that Arnd also changed the disk quota structure
> > format too, so that'll slow things down as we try to figure out how to
> > reconcile 34-bit inode seconds vs. 40-bit quota timer seconds.
> >
> > (Or whatever happens with that)
> >
> 
> Sigh. FWIW, I liked Arnd's 40-bit inode time patch because it
> keeps the patch LoC for this conversion minimal.

We can extend the quota warning range without changing the on-disk
structures, and with much less code than changing the on-disk
structures.

We only need a ~500 year range for the warning expiry timestamp, and
we don't really care about fine grained resolution of the timer
expiry.

We've already got a 70 year range with the signed second counter. So
let's just redefine the timeout value on disk to use units of 10s
instead of 1s when the bigtime superblock feature bit is set. ANd
now we have our >500 year range requirement.

That shouldn't need much more than 5-10 lines of new code
translating the units when we read/write them from/to disk....

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com