linux-kernel - Re: [RFC][PATCH 0/6] Enhanced file stat system call

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Message-ID: <CACyXjPw-dY4o4O_ZXzeb9R-akmE-r1uAQ7Sd-dGYegkG932yqw@mail.gmail.com>
Date:	Fri, 13 May 2016 07:28:29 -0700
From:	Richard Sharpe <realrichardsharpe@...il.com>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	Steve French <smfrench@...il.com>,
	David Howells <dhowells@...hat.com>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	linux-afs@...r.kernel.org,
	"linux-nfs@...r.kernel.org" <linux-nfs@...r.kernel.org>,
	samba-technical <samba-technical@...ts.samba.org>,
	LKML <linux-kernel@...r.kernel.org>,
	"linux-ext4@...r.kernel.org" <linux-ext4@...r.kernel.org>,
	Deepa Dinamani <deepa.kernel@...il.com>
Subject: Re: [RFC][PATCH 0/6] Enhanced file stat system call

On Mon, May 9, 2016 at 6:09 AM, Arnd Bergmann <arnd@...db.de> wrote:
> On Thursday 05 May 2016 21:00:18 Steve French wrote:
>> On Thu, May 5, 2016 at 5:54 PM, Steve French <smfrench@...il.com> wrote:
>> > On Wed, May 4, 2016 at 8:46 AM, Arnd Bergmann <arnd@...db.de> wrote:
>> >> On Friday 29 April 2016 13:57:36 David Howells wrote:
>> >>> struct statx *buffer);
>> >>>
>> >>> This is an enhanced file stat function that provides a number of useful
>> >>> features, in summary:
>> >>>
>> >>> (1) More information: creation time, data version number, inode
>> >>> generation
>> >>> number and flags. A subset of these is available through a number of
>> >>> filesystems (such as CIFS, NFS, AFS, Ext4 and BTRFS).
>> >>>
>> >>
>> >> I have a question about birthtime/creationtime: As we are gaining a way
>> >> to read this, should we also provide a way to update it using a new
>> >> variant
>> >> of the utimensat syscall in order to have 'cp -a' create an identical
>> >> copy,
>> >> or is the idea that this is defined as the time that is particular copy
>> >> of the inode was created?
>> >>
>> >> I've discussed this with Deepa in the past, as she is driving the
>> >> convertion of the inode timestamps to timespec64 now, and we will
>> >> need a new version of utimensat for her work as well. I can see good
>> >> reasons either way (allowing updates of btime or disallowing them).
>> >
>> It would help interop with Windows (and presumably Mac) if birth time can be
>> updated
>
> Ok, thanks. That is certainly a good reason in favor.
>
> If nothing else comes up, I guess we can prepare a patch for a new
> utimensat variant to do this and wait for more comments on that.
>
>         Arnd

Isn't there also a strong case for a setattr call that allows us to
atomically set a collection of attributes from userspace?

It would seem that network file systems (the clients) could use such features.

-- 
Regards,
Richard Sharpe
(何以解憂？唯有杜康。--曹操)