By 2.6.36, they had taken away the owner field in the struct attribute
defined in include/linux/sysfs.h.  There are some relevant changelog
excerpts below.

commit 6fd69dc578fa0b1bbc3aad70ae3af9a137211707
Author: Guenter Roeck <guenter.roeck@ericsson.com>
Date:   Wed Jul 28 22:09:26 2010 -0700

    sysfs: Remove owner field from sysfs struct attribute
    
    Signed-off-by: Guenter Roeck <guenter.roeck@ericsson.com>
    Acked-by: Tejun Heo <tj@kernel.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/include/linux/sysfs.h b/include/linux/sysfs.h
...
commit 01e8ef11bc1a74e65678ed55795f59266d4add01
Author: Parag Warudkar <parag.lkml@gmail.com>
Date:   Sat Oct 18 20:28:50 2008 -0700

    x86: sysfs: kill owner field from attribute
    
    Tejun's commit 7b595756ec1f49e0049a9e01a1298d53a7faaa15 made sysfs
    attribute->owner unnecessary.  But the field was left in the structure to
    ease the merge.  It's been over a year since that change and it is now
    time to start killing attribute->owner along with its users - one arch at
    a time!
    
    This patch is attempt #1 to get rid of attribute->owner only for
    CONFIG_X86_64 or CONFIG_X86_32 .  We will deal with other arches later on
    as and when possible - avr32 will be the next since that is something I
    can test.  Compile (make allyesconfig / make allmodconfig / custom config)
    and boot tested.
    
    akpm: the idea is that we put the declaration of sttribute.owner inside
    `#ifndef CONFIG_X86'.  But that proved to be too ambitious for now because
    new usages kept on turning up in subsystem trees.
...
commit 7b595756ec1f49e0049a9e01a1298d53a7faaa15
Author: Tejun Heo <htejun@gmail.com>
Date:   Thu Jun 14 03:45:17 2007 +0900

    sysfs: kill unnecessary attribute->owner
    
    sysfs is now completely out of driver/module lifetime game.  After
    deletion, a sysfs node doesn't access anything outside sysfs proper,
    so there's no reason to hold onto the attribute owners.  Note that
    often the wrong modules were accounted for as owners leading to
    accessing removed modules.
    
    This patch kills now unnecessary attribute->owner.  Note that with
    this change, userland holding a sysfs node does not prevent the
    backing module from being unloaded.
    
    For more info regarding lifetime rule cleanup, please read the
    following message.
    
      http://article.gmane.org/gmane.linux.kernel/510293
    
    (tweaked by Greg to not delete the field just yet, to make it easier to
    merge things properly.)