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

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Message-Id: <20221124113317.37ca142d58b5e7efecd1facf@linux-foundation.org>
Date:   Thu, 24 Nov 2022 11:33:17 -0800
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Naresh Kamboju <naresh.kamboju@...aro.org>
Cc:     Linux-Next Mailing List <linux-next@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>, llvm@...ts.linux.dev,
        regressions@...ts.linux.dev, lkft-triage@...ts.linaro.org,
        vishal.moola@...il.com, Matthew Wilcox <willy@...radead.org>,
        Jann Horn <jannh@...gle.com>
Subject: Re: next: x86: clang: mm/khugepaged.c:1428:45: error: variable
 'pmd' is uninitialized when used here

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

> LKFT CI system noticed clang-15 build failures on x86_64 and i386.
> 
> Reported-by: Linux Kernel Functional Testing <lkft@...aro.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.