From: Andreas Dilger <adilger@sun.com>
Subject: Re: [PATCH 1/3] ext4: add EXT4_IOC_GETCRTIME ioctl
Date: Mon, 18 Aug 2008 02:01:58 -0700
Message-ID: <20080818090158.GJ3040@webber.adilger.int>
References: <48996A33.3010507@cn.fujitsu.com> <20080810022643.GC14756@mit.edu>
 <48A8D98B.9020701@cn.fujitsu.com> <20080818023656.GA20338@mit.edu>
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Cc: Li Zefan <lizf@cn.fujitsu.com>, linux-ext4@vger.kernel.org
To: Theodore Tso <tytso@mit.edu>
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On Aug 17, 2008  22:36 -0400, Theodore Ts'o wrote:
> That's the quick and dirty fast answer, yes.  The long-term (but one
> which involves much more work) is to define a new struct
> kernel<->glibc stat interface (we already have 5 or so :-) to extend
> it include st_crtime, and then try to get glibc to use the magic of
> ELF symbol versioning so there is a new struct stat as defined in
> /usr/include, and a new stat(2) call defined in glibc, which returns
> the new struct stat which include st_crtime.  This also means we have
> to define proper semantics for what happens if a filesystem doesn't
> support st_crtime.

In the meantime, I'd think it preferable to use a virtual-xattr to get
this information from the kernel instead of an ioctl.  That way a shell
script can extract it with getfattr, and it is no harder to do from a
C program using getxattr().

I'd propose something like "system.creation_time" for the xattr name,
but I'll leave it up to people who care to propose better names.

Cheers, Andreas
--
Andreas Dilger
Sr. Staff Engineer, Lustre Group
Sun Microsystems of Canada, Inc.