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Re: [PATCH 0/6] Extended file stat system call
- From: "Myklebust, Trond" <Trond dot Myklebust at netapp dot com>
- To: Roland McGrath <roland at hack dot frob dot com>
- Cc: David Howells <dhowells at redhat dot com>, Steve French <smfrench at gmail dot com>, "linux-fsdevel at vger dot kernel dot org" <linux-fsdevel at vger dot kernel dot org>, "linux-nfs at vger dot kernel dot org" <linux-nfs at vger dot kernel dot org>, "linux-cifs at vger dot kernel dot org" <linux-cifs at vger dot kernel dot org>, "samba-technical at lists dot samba dot org" <samba-technical at lists dot samba dot org>, "linux-ext4 at vger dot kernel dot org" <linux-ext4 at vger dot kernel dot org>, "wine-devel at winehq dot org" <wine-devel at winehq dot org>, "kfm-devel at kde dot org"<kfm-devel at kde dot org>, "nautilus-list at gnome dot org" <nautilus-list at gnome dot org>, "linux-api at vger dot kernel dot org" <linux-api at vger dot kernel dot org>, "libc-alpha at sourceware dot org" <libc-alpha at sourceware dot org>
- Date: Fri, 27 Apr 2012 00:33:06 +0000
- Subject: Re: [PATCH 0/6] Extended file stat system call
- References: <1335460011.9701.30.camel@lade.trondhjem.org> <20120419140558.17272.74360.stgit@warthog.procyon.org.uk> <CAH2r5ms4WQV3DnTvqNN=2N71Cj8UHwj8Z6+RHXgrAOv6mSoyQg@mail.gmail.com> <20656.1335450358@redhat.com> <CAH2r5mv1Lijdwk5zsQwYJr4Etb6fhrRyNXm-iFCQX+HecboGrQ@mail.gmail.com> <1335453958.9701.10.camel@lade.trondhjem.org> <CAH2r5mt5af-_hxBRKK72iD5Gr99bo91ec78Rov8EGVEx8=21mA@mail.gmail.com> <1335459642.9701.27.camel@lade.trondhjem.org> <CAH2r5mvmCfLrxRHje6Wx5X84zxPEHwRMUJGsjvWBujMu7w841w@mail.gmail.com> <10104.1335477476@redhat.com> <20120426220552.D98D62C0D3@topped-with-meat.com>
On Thu, 2012-04-26 at 15:05 -0700, Roland McGrath wrote:
> > What if the xstat() and struct xstat eventually becomes what userspace
> > uses as stat() (as a wrapper) and struct stat (if such a thing is
> > possible with glibc versioning)?
>
> It's certainly possible with symbol versioning, though it seems much more
> likely that we'd stick with the existing struct stat and stat* interfaces
> and only have the implementation using statx underneath (e.g. for new
> machines or kernel ABIs where the kernel stops providing any calls except
> for statxat), at least for the foreseeable future.
>
> > Do older programs that think they're using stat() and don't know about
> > the extra fields available expect to see a useful value in st_ino?
>
> POSIX requires that st_ino have a useful value for the standard *stat calls.
Yes, but we're talking about non-POSIX filesystems here. If the
filesystem doesn't have a useful value for st_ino, then the usual way of
dealing with those POSIX requirements is to fake up values. The question
then becomes whether or not we care if it is the kernel or userland that
fakes up those values.
--
Trond Myklebust
Linux NFS client maintainer
NetApp
Trond.Myklebust@netapp.com
www.netapp.com