[Trusty][Saucy][Raring][Quantal][Precise][PATCH 1/1] (no-up) overlayfs: add OVERLAYFS_SUPER_MAGIC to include/uapi/linux/magic.h

[Andy Whitcroft]

On Tue, Nov 05, 2013 at 10:20:44AM -0500, Joseph Salisbury wrote:
> On 11/05/2013 08:42 AM, Andy Whitcroft wrote:
> > On Mon, Nov 04, 2013 at 02:44:46PM -0500, Joseph Salisbury wrote:
> >> On 11/04/2013 12:54 PM, Andy Whitcroft wrote:
> >>> On Mon, Nov 04, 2013 at 12:30:01PM -0500, Joseph Salisbury wrote:
> >>>> On 11/04/2013 12:08 PM, Stefan Bader wrote:
> >>>>> On 04.11.2013 17:44, Joseph Salisbury wrote:
> >>>>>> BugLink: http://bugs.launchpad.net/bugs/1247769
> >>>>>>
> >>>>>> Signed-off-by: Joseph Salisbury <joseph.salisbury at canonical.com>
> >>>>>> ---
> >>>>>>  include/uapi/linux/magic.h |    1 +
> >>>>>>  1 file changed, 1 insertion(+)
> >>>>>>
> >>>>>> diff --git a/include/uapi/linux/magic.h b/include/uapi/linux/magic.h
> >>>>>> index 2944278..7993c79 100644
> >>>>>> --- a/include/uapi/linux/magic.h
> >>>>>> +++ b/include/uapi/linux/magic.h
> >>>>>> @@ -31,6 +31,7 @@
> >>>>>>  #define PSTOREFS_MAGIC		0x6165676C
> >>>>>>  #define EFIVARFS_MAGIC		0xde5e81e4
> >>>>>>  #define HOSTFS_SUPER_MAGIC	0x00c0ffee
> >>>>>> +#define OVERLAYFS_SUPER_MAGIC	0x794c764f
> >>>>>>  
> >>>>>>  #define MINIX_SUPER_MAGIC	0x137F		/* minix v1 fs, 14 char names */
> >>>>>>  #define MINIX_SUPER_MAGIC2	0x138F		/* minix v1 fs, 30 char names */
> >>>>>>
> >>>>> I wished the bug report would be helpful in a way to say which other piece of sw
> >>>>> would like that define in magic.h.
> >>>>> It probably works as band-aid but I wonder whether it would be cleaner to remove
> >>>>> the define from fs/overlayfs/super.c and include magic.h instead (to have only
> >>>>> one define and in the same place)
> >>>>>
> >>>>> -Stefan
> >>>>>
> >>>>>
> >>>>>
> >>>> Thanks for the feedback, Stefan.
> >>>>
> >>>> I can rework the patch to also remove the define from
> >>>> fs/overlayfs/super.c if that is best.  I'll also ask for additional
> >>>> info, in the bug report, to identify which other sw would like the
> >>>> define in magic.h.
> >>> I would like to know why this would be no-up as well.  If overlayfs is
> >>> not following a standard (and I am taking your word that this is so, not
> >>> confirming it) then it should be going upstream me thinks.
> >>>
> >>> -apw
> >> I added no-op because I didn't see an overlayfs directory in the
> >> mainline linux ~/fs tree. 
> > Well yes, this isn't Linus' upstream, but there is an upstream, Mikos
> > something who looks after it.  We should send it to him still.
> >
> > -apw
> 
> Thanks, Andy.  I'll remove the no-up and send the patch to Mikos. 
> 
> James responded in the bug report[0] as to why this is needed.  Due to
> another bug, they are changing Upstart tests to detect a /tmp overlalyfs
> filesystem and display a warning.
> 
> Do you think it's best to remove the define from ~fs/overlayfs/super.c
> and include it in magic.h instead?  If so, I'll make that change and
> re-send the patch.
> 
> [0] https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1247769/comments/5

If that is where they are normally it seems sensible to me.

-apw