next: x86: clang: mm/khugepaged.c:1428:45: error: variable 'pmd' is uninitialized when used here

next: x86: clang: mm/khugepaged.c:1428:45: error: variable 'pmd' is uninitialized when used here

[Naresh Kamboju]

LKFT CI system noticed clang-15 build failures on x86_64 and i386.

Reported-by: Linux Kernel Functional Testing <lkft@linaro.org>

make --silent --keep-going --jobs=8
O=/home/tuxbuild/.cache/tuxmake/builds/1/build LLVM=1 LLVM_IAS=1
ARCH=x86_64 SRCARCH=x86 CROSS_COMPILE=x86_64-linux-gnu-
'HOSTCC=sccache clang' 'CC=sccache clang'
mm/khugepaged.c:1428:45: error: variable 'pmd' is uninitialized when
used here [-Werror,-Wuninitialized]
        page_table_check_pte_clear_range(mm, addr, pmd);
                                                   ^~~
mm/khugepaged.c:1415:2: note: variable 'pmd' is declared here
        pmd_t pmd;
        ^
1 error generated.
make[3]: *** [scripts/Makefile.build:252: mm/khugepaged.o] Error 1

steps to reproduce:
------------------
# To install tuxmake on your system globally:
# sudo pip3 install -U tuxmake
#
# See https://docs.tuxmake.org/ for complete documentation.
# Original tuxmake command with fragments listed below.
# tuxmake --runtime podman --target-arch x86_64 --toolchain clang-15
--kconfig defconfig --kconfig-add
https://raw.githubusercontent.com/Linaro/meta-lkft/kirkstone/meta/recipes-kernel/linux/files/lkft.config
--kconfig-add https://raw.githubusercontent.com/Linaro/meta-lkft/kirkstone/meta/recipes-kernel/linux/files/lkft-crypto.config
--kconfig-add https://raw.githubusercontent.com/Linaro/meta-lkft/kirkstone/meta/recipes-kernel/linux/files/distro-overrides.config
--kconfig-add https://raw.githubusercontent.com/Linaro/meta-lkft/kirkstone/meta/recipes-kernel/linux/files/systemd.config
--kconfig-add https://raw.githubusercontent.com/Linaro/meta-lkft/kirkstone/meta/recipes-kernel/linux/files/virtio.config
--kconfig-add CONFIG_IGB=y --kconfig-add
CONFIG_UNWINDER_FRAME_POINTER=y LLVM=1 LLVM_IAS=1


Build results compare:
https://qa-reports.linaro.org/lkft/linux-next-master-sanity/build/next-20221124/testrun/13170041/suite/build/test/clang-lkftconfig/history/

Build log link,
https://builds.tuxbuild.com/2Hz2wymTKCJRrwkDTV5zeM4SkJ0/

--
Linaro LKFT
https://lkft.linaro.org

Re: next: x86: clang: mm/khugepaged.c:1428:45: error: variable 'pmd' is uninitialized when used here

[Andrew Morton]

On Thu, 24 Nov 2022 21:07:48 +0530 Naresh Kamboju <naresh.kamboju@linaro.org> wrote:

> LKFT CI system noticed clang-15 build failures on x86_64 and i386.
> 
> Reported-by: Linux Kernel Functional Testing <lkft@linaro.org>
> 
> make --silent --keep-going --jobs=8
> O=/home/tuxbuild/.cache/tuxmake/builds/1/build LLVM=1 LLVM_IAS=1
> ARCH=x86_64 SRCARCH=x86 CROSS_COMPILE=x86_64-linux-gnu-
> 'HOSTCC=sccache clang' 'CC=sccache clang'
> mm/khugepaged.c:1428:45: error: variable 'pmd' is uninitialized when
> used here [-Werror,-Wuninitialized]
>         page_table_check_pte_clear_range(mm, addr, pmd);
>                                                    ^~~
> mm/khugepaged.c:1415:2: note: variable 'pmd' is declared here
>         pmd_t pmd;
>         ^

Thanks.  Due to "mm/khugepaged: fix GUP-fast interaction by freeing
ptes via mmu_gather".

Jann, I'll just do this for now:

--- a/mm/khugepaged.c~mm-khugepaged-fix-gup-fast-interaction-by-freeing-ptes-via-mmu_gather-fix
+++ a/mm/khugepaged.c
@@ -1431,7 +1431,6 @@ static void collapse_and_free_pmd(struct
 	 */
 	if (vma->anon_vma)
 		lockdep_assert_held_write(&vma->anon_vma->root->rwsem);
-	page_table_check_pte_clear_range(mm, addr, pmd);
 
 	tlb_gather_mmu(&tlb, mm);
 	pmd = READ_ONCE(*pmdp);
_

please check.