Re: New NFSv4.2 attribute |FATTR4_TMPFILE| (sort of opposite of |FATTR4_OFFLINE|) ?

[Chuck Lever III <chuck.lever@oracle.com>]

> On Jul 23, 2024, at 9:16 AM, Roland Mainz <roland.mainz@nrubsig.org> wrote:
> 
> The Win32 API has |FILE_ATTRIBUTE_TEMPORARY| (see
> https://learn.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-createfilea)
> to optimise for short-lived/small temporary files - would it be useful
> to reflect that in the NFSv4.2 protocol via a |FATTR4_TMPFILE|
> attribute (sort of the opposite of |FATTR4_OFFLINE|, such a
> |FATTR4_TMPFILE| should be ignored by HSM, and flushing to stable
> storage should be relaxed/delayed as long as possible) ?

Well, I might start with the client side. The client could
avoid flushing data back to the server in this case, and
the server (and protocol) wouldn't have to know about the
file's temporary status.

I'm not aware of a system call API on POSIX NFS clients
that might enable them to use such a protocol feature.
One idea might be to use fadvise(2)... ? So because this
might be a feature only for clients that support the
CreateFileA API, prototyping it on such clients might be
a good place to demonstrate value.


--
Chuck Lever