linux-kernel - [PATCH v3 21/27] mm/hugetlb: Introduce huge version of special swap pte helpers

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Message-Id: <20210527202324.32104-1-peterx@redhat.com>
Date:   Thu, 27 May 2021 16:23:24 -0400
From:   Peter Xu <peterx@...hat.com>
To:     linux-kernel@...r.kernel.org, linux-mm@...ck.org
Cc:     Mike Rapoport <rppt@...ux.vnet.ibm.com>, peterx@...hat.com,
        Andrew Morton <akpm@...ux-foundation.org>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Jerome Glisse <jglisse@...hat.com>,
        Miaohe Lin <linmiaohe@...wei.com>,
        Nadav Amit <nadav.amit@...il.com>,
        Hugh Dickins <hughd@...gle.com>,
        Matthew Wilcox <willy@...radead.org>,
        Jason Gunthorpe <jgg@...pe.ca>,
        "Kirill A . Shutemov" <kirill@...temov.name>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Axel Rasmussen <axelrasmussen@...gle.com>
Subject: [PATCH v3 21/27] mm/hugetlb: Introduce huge version of special swap pte helpers

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@...cle.com>
Signed-off-by: Peter Xu <peterx@...hat.com>
---
 mm/hugetlb.c | 24 ++++++++++++++++++++++--
 1 file changed, 22 insertions(+), 2 deletions(-)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index b101c3af3ab5..c64dfd0a9883 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -133,6 +133,26 @@ 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)
 {
@@ -4061,7 +4081,7 @@ 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))
@@ -4074,7 +4094,7 @@ 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