Re: [RFC/PATCH bpf-next] bpf: Fix d_path test after last fs update

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On Wed, Aug 30, 2023 at 12:04 PM Jiri Olsa <olsajiri@xxxxxxxxx> wrote:
>
> On Wed, Aug 30, 2023 at 02:35:49PM -0400, Song Liu wrote:
> > On Wed, Aug 30, 2023 at 9:27 AM Jiri Olsa <olsajiri@xxxxxxxxx> wrote:
> > >
> > > On Wed, Aug 30, 2023 at 11:35:02AM +0200, Jiri Olsa wrote:
> > > > Recent commit [1] broken d_path test, because now filp_close is not
> > > > called directly from sys_close, but eventually later when the file
> > > > is finally released.
> > > >
> > > > I can't see any other solution than to hook filp_flush function and
> > > > that also means we need to add it to btf_allowlist_d_path list, so
> > > > it can use the d_path helper.
> > > >
> > > > But it's probably not very stable because filp_flush is static so it
> > > > could be potentially inlined.
> > >
> > > looks like llvm makes it inlined (from CI)
> > >
> > >   Error: #68/1 d_path/basic
> > >   libbpf: prog 'prog_close': failed to find kernel BTF type ID of 'filp_flush': -3
> > >
> > > jirka
> >
> > I played with it for a bit, but haven't got a good solution. Maybe we should
> > just remove the test for close()?
>
> I was thinking the same.. also we have some example with filp_close in bpftrace
> docs, I think we'll need to add some note with explanation in there

Maybe use __x64_sys_close in the test and recommend bpftrace scripts
to do the same?





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