Re: [PATCH RFC 2/9] timekeeping: new interfaces for multigrain timestamp handing

[Christian Brauner]

> Back to your earlier point though:
> 
> Is a global offset really a non-starter? I can see about doing something
> per-superblock, but ktime_get_mg_coarse_ts64 should be roughly as cheap
> as ktime_get_coarse_ts64. I don't see the downside there for the non-
> multigrain filesystems to call that.

I have to say that this doesn't excite me. This whole thing feels a bit
hackish. I think that a change version is the way more sane way to go.

> 
> On another note: maybe I need to put this behind a Kconfig option
> initially too?

So can we for a second consider not introducing fine-grained timestamps
at all. We let NFSv3 live with the cache problem it's been living with
forever.

And for NFSv4 we actually do introduce a proper i_version for all
filesystems that matter to it.

What filesystems exactly don't expose a proper i_version and what does
prevent them from adding one or fixing it?