[PATCH v5 20/26] mm/hugetlb: Introduce huge version of special swap pte helpers

Peter Xu
2021-07-15T20:17:14Z

This is to let hugetlbfs be prepared to also recognize swap special ptes just
like uffd-wp special swap ptes.

Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
---
mm/hugetlb.c | 24 ++++++++++++++++++++++--
1 file changed, 22 insertions(+), 2 deletions(-)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 4edb3ee885ea..517ee30f272c 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -95,6 +95,26 @@ static inline bool subpool_is_free(struct hugepage_subpool *spool)
return true;
}

+/*
+ * These are sister versions of is_swap_pte() and pte_has_swap_entry(). We
+ * need standalone ones because huge_pte_none() is handled differently from
+ * pte_none(). For more information, please refer to comments above
+ * is_swap_pte() and pte_has_swap_entry().
+ *
+ * Here we directly reuse the pte level of swap special ptes, for example, the
+ * pte_swp_uffd_wp_special(). It just stands for a huge page rather than a
+ * small page for hugetlbfs pages.
+ */
+static inline bool is_huge_swap_pte(pte_t pte)
+{
+ return !huge_pte_none(pte) && !pte_present(pte);
+}
+
+static inline bool huge_pte_has_swap_entry(pte_t pte)
+{
+ return is_huge_swap_pte(pte) && !is_swap_special_pte(pte);
+}
+
static inline void unlock_or_release_subpool(struct hugepage_subpool *spool,
unsigned long irq_flags)
{
@@ -4138,7 +4158,7 @@ bool is_hugetlb_entry_migration(pte_t pte)
{
swp_entry_t swp;

- if (huge_pte_none(pte) || pte_present(pte))
+ if (!huge_pte_has_swap_entry(pte))
return false;
swp = pte_to_swp_entry(pte);
if (is_migration_entry(swp))
@@ -4151,7 +4171,7 @@ static bool is_hugetlb_entry_hwpoisoned(pte_t pte)
{
swp_entry_t swp;

- if (huge_pte_none(pte) || pte_present(pte))
+ if (!huge_pte_has_swap_entry(pte))
return false;
swp = pte_to_swp_entry(pte);
if (is_hwpoison_entry(swp))
--
2.31.1