Re: nanosecond file timestamp resolution in filesystems, GNU make, etc.

[Andi Kleen <ak@suse.de>]

Paul Eggert <eggert@twinsun.com> writes:
> 
> > Another way would be to round on flush, but that also has some problems :-
> 
> Rounding is even worse.  GNU Make assumes truncation, i.e. it assumes
> that a timestamp is truncated (floored, actually) when it is stored on
> a non-nanosecond-aware filesystem.

That is what my patchkit does currently, so I guess it should work fine.

> 
> > In my current patchkit I just chose to truncate because that was the 
> > easiest and the other more complicated solutions didn't offer any 
> > compeling advantage.
> 
> Can't you truncate/floor to filesystem timestamp resolution
> immediately, i.e., before the inode is flushed?  That would address
> the problems that I see.

That would complicate the timestamp management in the kernel considerably.
I'm not sure if I want to do that, probably not.

-Andi