ext4 - getting at birth time (file create time) and getting/setting nanosecond time stamps and utime

Sunil Mushran sunil.mushran at oracle.com
Tue Oct 20 15:23:45 MDT 2009

Steve French wrote:
> On Tue, Oct 20, 2009 at 3:59 PM, Sunil Mushran <sunil.mushran at oracle.com> wrote:
>> Steve French wrote:
>>> So, are we ready for Mingming or one of the ext4 developers to propose
>>> a patch for this via xattrs (I can do a similar one for cifs).
>>> Sounds like various have said:
>>> 1) xattrs instead of ioctl
>>> 2) get of create time allowed by default, but set of create time limited
>>> But for the second part of this - how should we set nanosecond
>>> timestamps for the others (or in Samba's case, rounded to 100
>>> nanoseconds for DCE time) ... a millisecond granularity for utimes is
>>> a very long time these days.
>> What's wrong with stat(2)? AFAIK, it supports nanoseconds.
> An earlier post from Mingming IIRC noted that utimes does not support
> setting nanosecond timestamps (e.g. write time).
> "The function utime() allows specification of time stamps with a
> resolution of 1 second. ... The function utimes() is similar, but the
> times argument allows a reso lution of 1 microsecond for the
> timestamps. "   1 millisecond is not sufficient, and as a result Samba
> has to store duplicate time stamps (in Samba specific xattrs) which we
> would like to avoid wherever possible

If you are trying to update it, you can use utimensat(2).

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