linux-kernel - Re: [PATCH 10/23] afs: switch to use uuid_t and uuid

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Date:   Thu, 25 May 2017 15:00:27 +0200
From:   Christoph Hellwig <hch@....de>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     Christoph Hellwig <hch@....de>,
        Amir Goldstein <amir73il@...il.com>,
        linux-fsdevel@...r.kernel.org, Shaohua Li <shli@...nel.org>,
        Dan Williams <dan.j.williams@...el.com>,
        David Howells <dhowells@...hat.com>,
        Steven Whitehouse <swhiteho@...hat.com>,
        Mimi Zohar <zohar@...ux.vnet.ibm.com>,
        linux-xfs@...r.kernel.org, linux-raid@...r.kernel.org,
        linux-nvdimm@...ts.01.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 10/23] afs: switch to use uuid_t and uuid_gen

On Tue, May 23, 2017 at 04:11:39PM +0300, Andy Shevchenko wrote:
> Since we introduced a union it's possible that we might access the
> member which wasn't last modified one. So, my comment is to give an
> attention on such possibility and avoid if there is an aliasing
> happened.

We do for AFS (and XFS for fs fsid).  My preference would be to
not have the v1 struct defintion but instead provide a few
helpers in uuid.h that use get_unaligned_be* if needed:

	uuid_v1_time_low()
	uuid_v1_time_mid()
	uuid_v1_time_time_hi_and_version()..

>From his previously reply it seems like Dave doesn't like that idea
too much, in which case I suspect moving struct uuid_v1 back into
afs and living with cast in it is the way to go.