[PATCH 18/23] mm/hugetlb: Introduce huge version of special swap pte helpers

From: Peter Xu <peterx@redhat.com>
To: linux-kernel@vger.kernel.org, linux-mm@kvack.org
Cc: "Kirill A . Shutemov" <kirill@shutemov.name>,
	Jerome Glisse <jglisse@redhat.com>,
	Mike Kravetz <mike.kravetz@oracle.com>,
	Matthew Wilcox <willy@infradead.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Axel Rasmussen <axelrasmussen@google.com>,
	Hugh Dickins <hughd@google.com>,
	peterx@redhat.com, Nadav Amit <nadav.amit@gmail.com>,
	Andrea Arcangeli <aarcange@redhat.com>,
	Mike Rapoport <rppt@linux.vnet.ibm.com>
Subject: [PATCH 18/23] mm/hugetlb: Introduce huge version of special swap pte helpers
Date: Mon, 22 Mar 2021 20:49:07 -0400	[thread overview]
Message-ID: <20210323004912.35132-19-peterx@redhat.com> (raw)
In-Reply-To: <20210323004912.35132-1-peterx@redhat.com>

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

Signed-off-by: Peter Xu <peterx@redhat.com>
---
 mm/hugetlb.c | 23 +++++++++++++++++++++--
 1 file changed, 21 insertions(+), 2 deletions(-)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index fd3e87517e10..64e424b03774 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -93,6 +93,25 @@ 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)
 {
 	spin_unlock(&spool->lock);
@@ -3726,7 +3745,7 @@ 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))
@@ -3739,7 +3758,7 @@ 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))
-- 
2.26.2

