On 19-Oct-09, at 11:17, Steve French wrote:
A new version of the format for Samba server related file system
extended attributes is expected in the next version of Samba so the
topic of create time and nanosecond timestamps for Linux has come up
again. Since some file systems don't support storing create time
(birth time), and none support updating create time, or for that
matter for storing any nanosecond timestamps at all (a millisecond
seems like a much longer time today than when the stat structure was
defined), and dos attributes, Samba server stores these in extended
attributes, which is awkward on those file systems which store
(different) versions of these on disk.
I had proposed in the past that these file attributes be exposed to
userspace as virtual xattrs, e.g. user.cr_time returning a struct
timespec, but the data is stored internal to the filesystem in whatever
format is most efficient for it. We only strictly need user.crtime
for this, but I wouldn't object to exporting other inode attributes in
this way (e.g. user.mtime, user.atime, etc).
I believe that nanosecond timestamps ARE supported with newer
filesystems
using stat(). There is the utimensat() system call, which takes a
timespec
parameter, so it looks to be suitable for setting nanosecond timestamps
from userspace. I don't know if glibc() supports this, but I do see it
in the kernel.
As for _updating_ create time, isn't that sort of defeating the purpose
of create time?
Cheers, Andreas
--
Andreas Dilger
Sr. Staff Engineer, Lustre Group
Sun Microsystems of Canada, Inc.
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