[LTP] [PATCH v2 1/1] nfsstat01: Update client RPC calls for kernel 6.9

[NeilBrown]

On Tue, 27 Aug 2024, Martin Doucha wrote:
> On 23. 08. 24 23:59, NeilBrown wrote:
> > On Fri, 23 Aug 2024, Petr Vorel wrote:
> >> We discussed in v1 how to fix tests.  Neil suggested to fix the test the way so
> >> that it works on all kernels. As I note [1]
> >>
> >> 1) either we give up on checking the new functionality still works (if we
> >> fallback to old behavior)
> > 
> > I don't understand.  What exactly do you mean by "the new
> > functionality".
> > As I understand it there is no new functionality.  All there was was and
> > information leak between network namespaces, and we stopped the leak.
> > Do you consider that to be new functionality?
> 
> The new functionality is that the patches add a new file to network 
> namespaces: /proc/net/rpc/nfs. This file did not exist outside the root 
> network namespace at least on some of the kernels where we still need to 
> run this test. So the question is: How aggressively do we want to 
> enforce backporting of these NFS patches into distros with older kernels?

Thanks for explaining that.  I had assumed that the the file was always
visible from all name spaces, but before the fix every namespace saw the
same file.  Clearly I was wrong.

> 
> We have 3 options how to fix the test depending on the answer:
> 1) Don't enforce at all. We'll check whether /proc/net/rpc/nfs exists in 
> the client namespace and read it only if it does. Otherwise we'll fall 
> back on the global file.
> 2) Enforce aggressively. We'll hardcode a minimal kernel version into 
> the test (e.g. v5.4) and if the procfile doesn't exist on any newer 
> kernel, it's a bug.
> 3) Enforce on new kernels only. We'll set a hard requirement for kernel 
> v6.9+ as in option 2) and check for existence of the procfile on any 
> older kernels as in option 1).

I think there are two totally separate questions here.
1/ How to fix the existing test to work on new and old kernels.  The
  existing test checked that the rpc count increased when NFS traffic
  happened.  I think 1 is the correct fix.  I don't think the test
  should check kernel version.

2/ We have discovered a bug and want to add a test to guard against
  regression.  This should be a new test.  That test can simply check if
  the given file exist in a non-init namespace.  I have no particular
  opinion about testing kernel versions.  A credible approach would be
  to choose the oldest kernel which it still maintained at the time that
  that bug was discovered.  Or maybe create a list of kernel versions
  where were maintained at that time and only run the test on versions
  in that list, or after the last in the list.

I really think there is value in having two different tests because we
are testing two different things.

Thanks,
NeilBrown


> 
> -- 
> Martin Doucha   mdoucha@suse.cz
> SW Quality Engineer
> SUSE LINUX, s.r.o.
> CORSO IIa
> Krizikova 148/34
> 186 00 Prague 8
> Czech Republic
> 
>