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-rw-r--r--include/linux/pgtable.h29
-rw-r--r--include/linux/swapops.h2
2 files changed, 31 insertions, 0 deletions
diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
index f4f4077b97aa..53750224e176 100644
--- a/include/linux/pgtable.h
+++ b/include/linux/pgtable.h
@@ -1003,6 +1003,35 @@ static inline pgprot_t pgprot_modify(pgprot_t oldprot, pgprot_t newprot)
#define arch_start_context_switch(prev) do {} while (0)
#endif
+/*
+ * When replacing an anonymous page by a real (!non) swap entry, we clear
+ * PG_anon_exclusive from the page and instead remember whether the flag was
+ * set in the swp pte. During fork(), we have to mark the entry as !exclusive
+ * (possibly shared). On swapin, we use that information to restore
+ * PG_anon_exclusive, which is very helpful in cases where we might have
+ * additional (e.g., FOLL_GET) references on a page and wouldn't be able to
+ * detect exclusivity.
+ *
+ * These functions don't apply to non-swap entries (e.g., migration, hwpoison,
+ * ...).
+ */
+#ifndef __HAVE_ARCH_PTE_SWP_EXCLUSIVE
+static inline pte_t pte_swp_mkexclusive(pte_t pte)
+{
+ return pte;
+}
+
+static inline int pte_swp_exclusive(pte_t pte)
+{
+ return false;
+}
+
+static inline pte_t pte_swp_clear_exclusive(pte_t pte)
+{
+ return pte;
+}
+#endif
+
#ifdef CONFIG_HAVE_ARCH_SOFT_DIRTY
#ifndef CONFIG_ARCH_ENABLE_THP_MIGRATION
static inline pmd_t pmd_swp_mksoft_dirty(pmd_t pmd)
diff --git a/include/linux/swapops.h b/include/linux/swapops.h
index e476a8fed537..d1b728904d4e 100644
--- a/include/linux/swapops.h
+++ b/include/linux/swapops.h
@@ -26,6 +26,8 @@
/* Clear all flags but only keep swp_entry_t related information */
static inline pte_t pte_swp_clear_flags(pte_t pte)
{
+ if (pte_swp_exclusive(pte))
+ pte = pte_swp_clear_exclusive(pte);
if (pte_swp_soft_dirty(pte))
pte = pte_swp_clear_soft_dirty(pte);
if (pte_swp_uffd_wp(pte))