restore: Preserve timestamps to the nanosecond

[jilles]

Summary

It appears that sbin/restore already knows the full-resolution timestamps,
so the only thing to do is to stop converting the timespecs to timevals
and use futimens() and utimensat().

Test Plan

Dump and restore a small UFS image with a few file types in it.

[jhb]

Looks fine to me. I only have one tangential question: have you thought about making convenience wrappers in libc for utimens() and lutimens() that would call utimensat() with the respective flags?

[jilles]

In D2020#3, @jhb wrote:

Looks fine to me.

Thanks.

I only have one tangential question: have you thought about making convenience wrappers in libc for utimens() and lutimens() that would call utimensat() with the respective flags?

I don't think the benefit (fewer parameters to functions) is worth the cost (more functions, non-standard functions) here. Also, utilities like touch actually benefit from the flag parameter, since it replaces multiple function pointers (stat/lstat and utimes/lutimes) with one flag variable (0/AT_SYMLINK_NOFOLLOW).

[jilles]

Closed by commit rS279986 (authored by @jilles).