Re: [RFC] Ext3 nanosecond timestamps in big inodes

[Andi Kleen <ak@muc.de>]

Andreas Gruenbacher <agruen@suse.de> writes:

> this is a spin-off of an old patch by Alex Tomas <alex@clusterfs.com>:
> Alex originally had nanosecond timestamps in his original patch; here is
> a rejuvenated version. Please tell me what you think. Alex also added a
> create timestamp in his original patch. Do we actually need that?
>
> Nanoseconds consume 30 bits in the 32-bit fields. The remaining two bits 
> currently are zeroed out implicitly. We could later use them remaining two 
> bits for years beyond 2038.

Looks good. Just two suggestions:

- Provide an mount option to turn it off because there may be
performance regressions in some workload because inodes will be
flushed more often.
[I actually considered doing this generally at the VFS level
when doing the s_time_gran patch, but it needed some more changes
that I didn't want to do at that time. Doing it in the FS as
interim solution would be fine too]

- Use the 2 bits for additionals years right now on 64bit
hosts. No need to keep the y2038 issue around longer than necessary.

-Andi