Re: [PATCH] mm/rmap: use huge_ptep_get() in try_to_unmap_one()

[Dev Jain]

On 25/06/26 11:15 am, kernel test robot wrote:
> Hi Dev,
> 
> 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/Dev-Jain/mm-rmap-use-huge_ptep_get-in-try_to_unmap_one/20260625-123050
> base:   https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-everything
> patch link:    https://lore.kernel.org/r/20260625042853.2752898-1-dev.jain%40arm.com
> patch subject: [PATCH] mm/rmap: use huge_ptep_get() in try_to_unmap_one()
> config: hexagon-allnoconfig (https://download.01.org/0day-ci/archive/20260625/202606251341.jfIr1D7m-lkp@xxxxxxxxx/config)
> compiler: clang version 23.0.0git (https://github.com/llvm/llvm-project 6cc609bb250b21b47fc7d394b4019101e9983597)
> reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260625/202606251341.jfIr1D7m-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/202606251341.jfIr1D7m-lkp@xxxxxxxxx/
> 
> All errors (new ones prefixed by >>):
> 
>>> mm/rmap.c:2100:13: error: call to undeclared function 'huge_ptep_get'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
>     2100 |                         pteval = huge_ptep_get(mm, address, pvmw.pte);
>          |                                  ^
>>> mm/rmap.c:2100:11: error: assigning to 'pte_t' from incompatible type 'int'
>     2100 |                         pteval = huge_ptep_get(mm, address, pvmw.pte);
>          |                                ^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>    2 errors generated.

Weird that I need a stub. This should do:

diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index 2abaf99321e90..4661f88eee55b 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -1261,6 +1261,16 @@ static inline void hugetlb_count_sub(long l, struct mm_struct *mm)
 {
 }

+static inline pte_t huge_ptep_get(struct mm_struct *mm, unsigned long addr,
+				  pte_t *ptep)
+{
+#ifdef CONFIG_MMU
+	return ptep_get(ptep);
+#else
+	return *ptep;
+#endif
+}
+
 static inline pte_t huge_ptep_clear_flush(struct vm_area_struct *vma,
 					  unsigned long addr, pte_t *ptep)
 {
diff --git a/mm/rmap.c b/mm/rmap.c
index 1c77d5dc06e9f..aa8a254efaecc 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -2095,11 +2095,16 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma,
 		/* Unexpected PMD-mapped THP? */
 		VM_BUG_ON_FOLIO(!pvmw.pte, folio);

-		/*
-		 * Handle PFN swap PTEs, such as device-exclusive ones, that
-		 * actually map pages.
-		 */
-		pteval = ptep_get(pvmw.pte);
+		address = pvmw.address;
+		if (folio_test_hugetlb(folio)) {
+			pteval = huge_ptep_get(mm, address, pvmw.pte);
+		} else {
+			/*
+			 * Handle PFN swap PTEs, such as device-exclusive ones,
+			 * that actually map pages.
+			 */
+			pteval = ptep_get(pvmw.pte);
+		}
 		if (likely(pte_present(pteval))) {
 			pfn = pte_pfn(pteval);
 		} else {
@@ -2110,7 +2115,6 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma,
 		}

 		subpage = folio_page(folio, pfn - folio_pfn(folio));
-		address = pvmw.address;
 		anon_exclusive = folio_test_anon(folio) &&
 				 PageAnonExclusive(subpage);