[PATCH] mm: teach mincore_hugetlb about pte markers

James Houghton
2023-03-02T22:24:22Z

By checking huge_pte_none(), we incorrectly classify PTE markers as
"present". Instead, check huge_pte_none_mostly(), classifying PTE
markers the same as if the PTE were completely blank.

PTE markers, unlike other kinds of swap entries, don't reference any
physical page and don't indicate that a physical page was mapped
previously. As such, treat them as non-present for the sake of
mincore().

Fixes: 5c041f5d1f23 ("mm: teach core mm about pte markers")
Signed-off-by: James Houghton <jthoughton@google.com>
---
mm/mincore.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/mincore.c b/mm/mincore.c
index cd69b9db0081..d359650b0f75 100644
--- a/mm/mincore.c
+++ b/mm/mincore.c
@@ -33,7 +33,7 @@ static int mincore_hugetlb(pte_t *pte, unsigned long hmask, unsigned long addr,
* Hugepages under user process are always in RAM and never
* swapped out, but theoretically it needs to be checked.
*/
- present = pte && !huge_pte_none(huge_ptep_get(pte));
+ present = pte && !huge_pte_none_mostly(huge_ptep_get(pte));
for (; addr != end; vec++, addr += PAGE_SIZE)
*vec = present;
walk->private = vec;
--
2.40.0.rc0.216.gc4246ad0f0-goog