Re: [PATCH v7 mm-new 01/10] mm: thp: remove disabled task from khugepaged_mm_slot

Lance Yang <lance.yang@xxxxxxxxx> · Thu, 11 Sep 2025 10:12:48 +0800

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;
 }

Cheers,
Lance







