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Date: Tue, 29 Jun 2010 17:33:56 -0500
Message-ID: <AANLkTimieV9ybz2XrD29tvz1mogdMA5VHH4lNSwPovoE@mail.gmail.com>
Subject: Re: [PATCH 3/3] Add a pair of system calls to make extended file 
	stats available
From: Steve French <smfrench@gmail.com>
To: Ulrich Drepper <drepper@gmail.com>
Cc: David Howells <dhowells@redhat.com>, viro@zeniv.linux.org.uk,
       jlayton@redhat.com, mcao@us.ibm.com, aneesh.kumar@linux.vnet.ibm.com,
       linux-cifs@vger.kernel.org, linux-fsdevel@vger.kernel.org,
       linux-kernel@vger.kernel.org, samba-technical@lists.samba.org,
       sjayaraman@suse.de, linux-ext4@vger.kernel.org
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On Tue, Jun 29, 2010 at 5:13 PM, Ulrich Drepper <drepper@gmail.com> wrote:
> On Tue, Jun 29, 2010 at 13:03, David Howells <dhowells@redhat.com> wrote:
>> Add a pair of system calls to make extended file stats available, including
>> file creation time, inode version and data version where available through the
>> underlying filesystem:
>
> If you add something like this you might want to integrate another
> extension. ?This has been discussed a long time ago. ?In almost no
> situation all the information is needed. ?Some of the pieces of
> information returned by the syscall might be harder to collect than
> other. ?It makes sense in such a situation to allow the caller to
> specify what she is interested in. ?A bitmask of some sort. ?This was
> brought up by the HPC people with gigantic filesystems.
>
> For this the syscall interface should have a parameter to specify what
> is requested and the stat-like structure should have a field
> specifying what is actually present. ?The latter bitmask must be a
> superset of the former.
>
> Previous discussions centered around reusing the stat data structure
> and somehow make it work. ?But no clean solution was found. ?If a new
> structure is added anyway this could solve the issue.

That makes sense, especially for network file systems.  NFSv4
protocol spec anticipates that:

"With the NFS version 4 protocol, the client is able query what attributes
   the server supports and construct requests with only those supported
   attributes (or a subset thereof)."

and we were talking about something similar for SMB2 Unix Extensions
(posix extensions) at the last plugfest (for SMB2 kernel
client to Samba)
and testing events.
-- 
Thanks,

Steve
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