On Wed, Sep 10, 2025 at 10:28:30PM -0400, Zi Yan wrote: > On 10 Sep 2025, at 22:12, Lance Yang wrote: > > > Hi Yafang, > > > > On 2025/9/11 01:27, kernel test robot wrote: > >> Hi Yafang, > >> > >> kernel test robot noticed the following build errors: > >> > >> [auto build test ERROR on akpm-mm/mm-everything] > >> > >> url: https://github.com/intel-lab-lkp/linux/commits/Yafang-Shao/mm-thp-remove-disabled-task-from-khugepaged_mm_slot/20250910-144850 > >> base: https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-everything > >> patch link: https://lore.kernel.org/r/20250910024447.64788-2-laoar.shao%40gmail.com > >> patch subject: [PATCH v7 mm-new 01/10] mm: thp: remove disabled task from khugepaged_mm_slot > >> config: x86_64-allnoconfig (https://download.01.org/0day-ci/archive/20250911/202509110109.PSgSHb31-lkp@xxxxxxxxx/config) > >> compiler: clang version 20.1.8 (https://github.com/llvm/llvm-project 87f0227cb60147a26a1eeb4fb06e3b505e9c7261) > >> reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250911/202509110109.PSgSHb31-lkp@xxxxxxxxx/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@xxxxxxxxx> > >> | Closes: https://lore.kernel.org/oe-kbuild-all/202509110109.PSgSHb31-lkp@xxxxxxxxx/ > >> > >> All errors (new ones prefixed by >>): > >> > >>>> kernel/sys.c:2500:6: error: call to undeclared function 'hugepage_pmd_enabled'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration] > >> 2500 | hugepage_pmd_enabled()) > >> | ^ > >>>> kernel/sys.c:2501:3: error: call to undeclared function '__khugepaged_enter'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration] > >> 2501 | __khugepaged_enter(mm); > >> | ^ > >> 2 errors generated. > > > > Oops, seems like hugepage_pmd_enabled() and __khugepaged_enter() are only > > available when CONFIG_TRANSPARENT_HUGEPAGE is enabled ;) > > > >> > >> > >> vim +/hugepage_pmd_enabled +2500 kernel/sys.c > >> > >> 2471 > >> 2472 static int prctl_set_thp_disable(bool thp_disable, unsigned long flags, > >> 2473 unsigned long arg4, unsigned long arg5) > >> 2474 { > >> 2475 struct mm_struct *mm = current->mm; > >> 2476 > >> 2477 if (arg4 || arg5) > >> 2478 return -EINVAL; > >> 2479 > >> 2480 /* Flags are only allowed when disabling. */ > >> 2481 if ((!thp_disable && flags) || (flags & ~PR_THP_DISABLE_EXCEPT_ADVISED)) > >> 2482 return -EINVAL; > >> 2483 if (mmap_write_lock_killable(current->mm)) > >> 2484 return -EINTR; > >> 2485 if (thp_disable) { > >> 2486 if (flags & PR_THP_DISABLE_EXCEPT_ADVISED) { > >> 2487 mm_flags_clear(MMF_DISABLE_THP_COMPLETELY, mm); > >> 2488 mm_flags_set(MMF_DISABLE_THP_EXCEPT_ADVISED, mm); > >> 2489 } else { > >> 2490 mm_flags_set(MMF_DISABLE_THP_COMPLETELY, mm); > >> 2491 mm_flags_clear(MMF_DISABLE_THP_EXCEPT_ADVISED, mm); > >> 2492 } > >> 2493 } else { > >> 2494 mm_flags_clear(MMF_DISABLE_THP_COMPLETELY, mm); > >> 2495 mm_flags_clear(MMF_DISABLE_THP_EXCEPT_ADVISED, mm); > >> 2496 } > >> 2497 > >> 2498 if (!mm_flags_test(MMF_DISABLE_THP_COMPLETELY, mm) && > >> 2499 !mm_flags_test(MMF_VM_HUGEPAGE, mm) && > >>> 2500 hugepage_pmd_enabled()) > >>> 2501 __khugepaged_enter(mm); > >> 2502 mmap_write_unlock(current->mm); > >> 2503 return 0; > >> 2504 } > >> 2505 > > > > So, let's wrap the new logic in an #ifdef CONFIG_TRANSPARENT_HUGEPAGE block. > > > > diff --git a/kernel/sys.c b/kernel/sys.c > > index a1c1e8007f2d..c8600e017933 100644 > > --- a/kernel/sys.c > > +++ b/kernel/sys.c > > @@ -2495,10 +2495,13 @@ static int prctl_set_thp_disable(bool thp_disable, unsigned long flags, > > mm_flags_clear(MMF_DISABLE_THP_EXCEPT_ADVISED, mm); > > } > > > > +#ifdef CONFIG_TRANSPARENT_HUGEPAGE > > if (!mm_flags_test(MMF_DISABLE_THP_COMPLETELY, mm) && > > !mm_flags_test(MMF_VM_HUGEPAGE, mm) && > > hugepage_pmd_enabled()) > > __khugepaged_enter(mm); > > +#endif > > + > > mmap_write_unlock(current->mm); > > return 0; > > } > > Or in the header file, > > #ifdef CONFIG_TRANSPARENT_HUGEPAGE > ... > #else > bool hugepage_pmd_enabled() > { > return false; > } > > int __khugepaged_enter(struct mm_struct *mm) > { > return 0; > } It seems we have a convention of just not implementing things here if they're necessarily used in core code paths (and _with my suggested change_) it's _just_ khugepaged that's invoking them). Anyway with my suggestion we can fix this entirely with: #ifdef CONFIG_TRANSPARENT_HUGEPAGE void khugepaged_enter_mm(struct mm_struct *mm); #else void khugepaged_enter_mm(struct mm_struct *mm) { } #endif Cheers, Lorenzo > #endif > > Best Regards, > Yan, Zi
