Re: [linux-next:master 7701/8232] mm/huge_memory.c:2735:31: warning: variable 'page' is uninitialized when used here

[Lance Yang <ioworker0@gmail.com>]

On Wed, Jun 26, 2024 at 5:52 AM Andrew Morton <akpm@linux-foundation.org> wrote:
>
> On Wed, 26 Jun 2024 05:39:54 +0800 kernel test robot <lkp@intel.com> wrote:
>
> > tree:   https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master
> > head:   0fc4bfab2cd45f9acb86c4f04b5191e114e901ed
> > commit: 4627108658d68fad359600dbe667b88b501cee71 [7701/8232] mm/vmscan: avoid split lazyfree THP during shrink_folio_list()
> > config: x86_64-rhel-8.3-rust (https://download.01.org/0day-ci/archive/20240626/202406260514.SLhNM9kQ-lkp@intel.com/config)
> > compiler: clang version 18.1.5 (https://github.com/llvm/llvm-project 617a15a9eac96088ae5e9134248d8236e34b91b1)
> > reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20240626/202406260514.SLhNM9kQ-lkp@intel.com/reproduce)
> >
> > If you fix the issue in a separate patch/commit (i.e. not just a new version of
> > the same patch/commit), kindly add following tags
> > | Reported-by: kernel test robot <lkp@intel.com>
> > | Closes: https://lore.kernel.org/oe-kbuild-all/202406260514.SLhNM9kQ-lkp@intel.com/
> >
> > All warnings (new ones prefixed by >>):
> >
> > >> mm/huge_memory.c:2735:31: warning: variable 'page' is uninitialized when used here [-Wuninitialized]
> >     2735 |         folio_remove_rmap_pmd(folio, page, vma);
> >          |                                      ^~~~
> >    mm/huge_memory.c:2699:19: note: initialize the variable 'page' to silence this warning
> >     2699 |         struct page *page;
> >          |                          ^
> >          |                           = NULL
> >    1 warning generated.
> >
> >
>
> um yes.
> https://lore.kernel.org/all/20240622100057.3352-1-ioworker0@gmail.com/T/#u
> removed the initialization.

My bad. I could have done better :(

>
> I'll do this, because I'm about to push a tree out:
>
> --- a/mm/huge_memory.c~hack
> +++ a/mm/huge_memory.c
> @@ -2697,7 +2697,6 @@ static bool __discard_anon_folio_pmd_loc
>         struct mm_struct *mm = vma->vm_mm;
>         int ref_count, map_count;
>         pmd_t orig_pmd = *pmdp;
> -       struct page *page;
>
>         if (folio_test_dirty(folio) || pmd_dirty(orig_pmd))
>                 return false;
> @@ -2733,7 +2732,7 @@ static bool __discard_anon_folio_pmd_loc
>                 return false;
>         }
>
> -       folio_remove_rmap_pmd(folio, page, vma);
> +       folio_remove_rmap_pmd(folio, pmd_page(orig_pmd), vma);

Thanks a lot for jumping in!
Lance

>         zap_deposited_table(mm, pmdp);
>         add_mm_counter(mm, MM_ANONPAGES, -HPAGE_PMD_NR);
>         if (vma->vm_flags & VM_LOCKED)
> _
>