Re: [Xen-devel] [PATCH for-4.5] pygrub: Fix regression from c/s d1b93ea, attempt 2

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Tue, 2014-12-02 at 02:43 +0000, Andrew Cooper wrote:
> On 01/12/2014 20:30, Konrad Rzeszutek Wilk wrote:
> > On Fri, Nov 28, 2014 at 11:31:24AM +0000, Ian Campbell wrote:
> >> On Tue, 2014-11-25 at 11:11 -0500, Boris Ostrovsky wrote:
> >>> c/s d1b93ea causes substantial functional regressions in pygrub's ability 
> >>> to
> >>> parse bootloader configuration files.
> >>>
> >>> c/s d1b93ea itself changed an an interface which previously used 
> >>> exclusively
> >>> integers, to using strings in the case of a grub configuration with 
> >>> explicit
> >>> default set, along with changing the code calling the interface to 
> >>> require a
> >>> string.  The default value for "default" remained as an integer.
> >>>
> >>> As a result, any Extlinux or Lilo configuration (which drives this 
> >>> interface
> >>> exclusively with integers), or Grub configuration which doesn't explicitly
> >>> declare a default will die with an AttributeError when attempting to call
> >>> "self.cf.default.isdigit()" where "default" is an integer.
> >>>
> >>> Sadly, this AttributeError gets swallowed by the blanket ignore in the 
> >>> loop
> >>> which searches partitions for valid bootloader configurations, causing the
> >>> issue to be reported as "Unable to find partition containing kernel"
> >>>
> >>> We should explicitly check type of "default" in image_index() and process 
> >>> it
> >>> appropriately.
> >>>
> >>> Reported-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> >>> Signed-off-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
> >> Acked-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
> >>
> >> In general I would prefer the first line of the commit message to be a
> >> short description of the actual functional change and not a reference to
> >> fixing some other commit, which is basically meaningless to anyone
> >> reading the log even now, nevermind in six months. I think I'm going to
> >> start picking up on this more frequently from now on.
> >>
> >> CCing Konrad for RM input. I'm much less worried about corner cases etc
> >> wrt the freeze etc than I was with the larger fix proposed earlier.
> > I am bit lost. I thought Andrew NACKed this?
> 
> I didn't, as I am not in a position to.  I have not tested the result,
> but believe it is sufficient to fix the exact error at hand.  If the
> maintainers think it is the best solution then so be it, but I am still
> of the opinion that it is is still a hack upon a hack.

At this point in a freeze I'm much happier with:

 tools/pygrub/src/pygrub |    4 +++-
 1 files changed, 3 insertions(+), 1 deletions(-)

than
 tools/pygrub/src/ExtLinuxConf.py |    6 +++---
 tools/pygrub/src/GrubConf.py     |    7 ++-----
 tools/pygrub/src/LiloConf.py     |    6 +++---
 3 files changed, 8 insertions(+), 11 deletions(-)

Plus Boris' patch is far easier to reason about in isolation in a
dynamically/duck typed language.

Ian.


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