Re: [RFC PATCH V3 31/43] rv64ilp32_abi: maple_tree: Use BITS_PER_LONG instead of CONFIG_64BIT

Guo Ren
2025-03-27T12:47:31Z

On Wed, Mar 26, 2025 at 3:10 AM Liam R. Howlett <Liam.Howlett@oracle.com> wrote:
>
> * guoren@kernel.org <guoren@kernel.org> [250325 08:24]:
> > From: "Guo Ren (Alibaba DAMO Academy)" <guoren@kernel.org>
> >
> > The Maple tree algorithm uses ulong type for each element. The
> > number of slots is based on BITS_PER_LONG for RV64ILP32 ABI, so
> > use BITS_PER_LONG instead of CONFIG_64BIT.
> >
> > Signed-off-by: Guo Ren (Alibaba DAMO Academy) <guoren@kernel.org>
> > ---
> > include/linux/maple_tree.h | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/include/linux/maple_tree.h b/include/linux/maple_tree.h
> > index cbbcd18d4186..ff6265b6468b 100644
> > --- a/include/linux/maple_tree.h
> > +++ b/include/linux/maple_tree.h
> > @@ -24,7 +24,7 @@
> > *
> > * Nodes in the tree point to their parent unless bit 0 is set.
> > */
> > -#if defined(CONFIG_64BIT) || defined(BUILD_VDSO32_64)
> > +#if (BITS_PER_LONG == 64) || defined(BUILD_VDSO32_64)
>
> This will break my userspace testing, if you do not update the testing as
> well. This can be found in tools/testing/radix-tree. Please also look
> at the Makefile as well since it will generate a build flag for the
> userspace.
I think you are talking about the following:
============================================================
../shared/shared.mk:
ifndef LONG_BIT
LONG_BIT := $(shell getconf LONG_BIT)
endif

generated/bit-length.h: FORCE
@mkdir -p generated
@if ! grep -qws CONFIG_$(LONG_BIT)BIT generated/bit-length.h; then \
echo "Generating $@"; \
echo "#define CONFIG_$(LONG_BIT)BIT 1" > $@; \
echo "#define CONFIG_PHYS_ADDR_T_$(LONG_BIT)BIT 1" >> $@; \
fi

$ grep CONFIG_64BIT * -r -A 2
generated/bit-length.h:#define CONFIG_64BIT 1
generated/bit-length.h-#define CONFIG_PHYS_ADDR_T_64BIT 1
--
maple.c:#if defined(CONFIG_64BIT)
maple.c-static noinline void __init check_erase2_testset(struct maple_tree *mt,
maple.c- const unsigned long *set, unsigned long size)
--
maple.c:#if CONFIG_64BIT
maple.c- MT_BUG_ON(mt, data_end != mas_data_end(&mas));
maple.c-#endif
--
maple.c:#if CONFIG_64BIT
maple.c- MT_BUG_ON(mt, data_end - 2 != mas_data_end(&mas));
maple.c-#endif
--
maple.c:#if CONFIG_64BIT
maple.c- MT_BUG_ON(mt, data_end - 4 != mas_data_end(&mas));
maple.c-#endif
--
maple.c:#if defined(CONFIG_64BIT)
maple.c- /* Captures from VMs that found previous errors */
maple.c- mt_init_flags(&tree, 0);
============================================================

First, we don't introduce rv64ilp32-abi user space, which means these
testing codes can't run on rv64ilp32-abi userspace currently. So, the
problem you mentioned doesn't exist.

Second, CONFIG_32BIT is determined by LONG_BIT, so there's no issue in
maple.c with future rv64ilp32-abi userspace.
That means rv64ilp32-abi userspace would use CONFIG_32BIT to test
radix-tree. It's okay.

>
> This raises other concerns as the code is found with a grep command, so
> I'm not sure why it was missed and if anything else is missed?
>
> If you consider this email to be the (unasked) question about what to do
> here, then please CC me, the maintainer of the files including the one
> you are updating here.
>
> Thank you,
> Liam
>

--
Best Regards
Guo Ren