"Roger A. Faulkner" <Roger.Faulkner at sun.com> wrote:
> I'm in agreement with the sentiment expressed here,
> and in fact I made the changes to support the pathconf()
> name _PC_TIMESTAMP_RESOLUTION in all the local file systems.
> ufs returns 1000 and zfs returns 1.
This seems to be correct.
> However, there is a problem with nfs.
> There is no over-the-wire protocol in nfs that can query
> the timestamp resolution of a remote file system.
> nfs's pathconf() issues one query to get a big block
> of attributes from the server and all of these attributes
> are fixed. There is no over-the-wire pathconf() call
> for new, individual _PC_* names.
This seems to be unfortunate. There should be a way to allow to enhance
the nfs protocol to match newer POSIX versions.
How about introducing a new call that sends the related ascii string over
the wire in case that the pathconf() call was not defined at the time the
related nfs version has been defined?
> nfs V3 and V4 both pass nanosecond-resolution time values
> over the wire, and utimensat() and futimens() will set
> nanosecond resolution time stamps on remotely-mounted file
> systems if the remote filesystems are zfs on the server side
This allows you to send nanosecond resolution for timestamps but not to
find out whether a non-identical timestamp on a remote file differs
from the time stamps in a tar archive because it differs or because the
remore resolution is not sufficient.
> But you can't (at least I can't) get the remote file system's
> time stamp resolution by any means other than actually attempting
> a utimensat() on it and examining the result with stat().
> Can you live with pathconf(_PC_TIMESTAMP_RESOLUTION) returning -1
> (with errno == EINVAL) for nfs-mounted files?
This is the way that is documented in POSIX.
J?rg
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js at cs.tu-berlin.de (uni)
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