linux-kernel - Re: [PATCH] Ext4: Make file creation time, i_version and i

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Message-Id: <19AAF9AA-2445-4C73-808B-4AD9C5C7E769@dilger.ca>
Date:	Mon, 28 Jun 2010 13:08:41 -0600
From:	Andreas Dilger <adilger@...ger.ca>
To:	David Howells <dhowells@...hat.com>
Cc:	viro@...IV.linux.org.uk, smfrench@...il.com, jlayton@...hat.com,
	mcao@...ibm.com, aneesh.kumar@...ux.vnet.ibm.com,
	linux-cifs@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org, samba-technical@...ts.samba.org,
	sjayaraman@...e.de, linux-ext4@...r.kernel.org
Subject: Re: [PATCH] Ext4: Make file creation time, i_version and i_generation available by xattrs

On 2010-06-28, at 10:26, David Howells wrote:
> Make the file creation time, inode data version number and inode generation
> number available on Ext4 by as xattrs named:
> 
> 	file.crtime
> 	file.i_generation
> 	file.i_version (directories only for ext4)

Some minor nits:
- I'd prefer calling these "file.generation" and "file.version".
  I don't think there is value in the "i_" prefix adds anything,
  and it seems more like an internal detail to me
- why not expose the ".version" field for regular files?  It seems
  that all of them are applicable for all file types.
- it would be good to not introduce a new xattr namespace, since
  tools like tar (even the RHEL-patched one) will not backup and
  restore these namespaces.  Using "trusted." would allow them to
  be backed up and restored using existing xattr-patched GNU tar
  by root, but wouldn't allow them to be modified by regular users.
  I think this is important for proper backup/restore of a filesystem,
  but can have correctness implications and shouldn't be accessible
  to regular users.

> file.crtime=0x53ba244c000000000000000000000000

Is this a binary (host-endian) struct timespec?

> file.i_generation=0x0000000000000000

This seems odd, i_generation should never be zero, AFAIK.

Cheers, Andreas





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