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 06280fc1c99b..32d517a28969 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))
diff --git a/mm/memory.c b/mm/memory.c
index 4742c06b6fa9..6ccc3658df61 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -795,6 +795,11 @@ copy_nonpresent_pte(struct mm_struct *dst_mm, struct mm_struct *src_mm,
 						&src_mm->mmlist);
 			spin_unlock(&mmlist_lock);
 		}
+		/* Mark the swap entry as shared. */
+		if (pte_swp_exclusive(*src_pte)) {
+			pte = pte_swp_clear_exclusive(*src_pte);
+			set_pte_at(src_mm, addr, src_pte, pte);
+		}
 		rss[MM_SWAPENTS]++;
 	} else if (is_migration_entry(entry)) {
 		page = pfn_swap_entry_to_page(entry);
@@ -3567,6 +3572,7 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
 	struct page *page = NULL, *swapcache;
 	struct swap_info_struct *si = NULL;
 	rmap_t rmap_flags = RMAP_NONE;
+	bool exclusive = false;
 	swp_entry_t entry;
 	pte_t pte;
 	int locked;
@@ -3732,6 +3738,46 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
 	BUG_ON(!PageAnon(page) && PageMappedToDisk(page));
 	BUG_ON(PageAnon(page) && PageAnonExclusive(page));
 
+	/*
+	 * Check under PT lock (to protect against concurrent fork() sharing
+	 * the swap entry concurrently) for certainly exclusive pages.
+	 */
+	if (!PageKsm(page)) {
+		/*
+		 * Note that pte_swp_exclusive() == false for architectures
+		 * without __HAVE_ARCH_PTE_SWP_EXCLUSIVE.
+		 */
+		exclusive = pte_swp_exclusive(vmf->orig_pte);
+		if (page != swapcache) {
+			/*
+			 * We have a fresh page that is not exposed to the
+			 * swapcache -> certainly exclusive.
+			 */
+			exclusive = true;
+		} else if (exclusive && PageWriteback(page) &&
+			   !(swp_swap_info(entry)->flags & SWP_STABLE_WRITES)) {
+			/*
+			 * This is tricky: not all swap backends support
+			 * concurrent page modifications while under writeback.
+			 *
+			 * So if we stumble over such a page in the swapcache
+			 * we must not set the page exclusive, otherwise we can
+			 * map it writable without further checks and modify it
+			 * while still under writeback.
+			 *
+			 * For these problematic swap backends, simply drop the
+			 * exclusive marker: this is perfectly fine as we start
+			 * writeback only if we fully unmapped the page and
+			 * there are no unexpected references on the page after
+			 * unmapping succeeded. After fully unmapped, no
+			 * further GUP references (FOLL_GET and FOLL_PIN) can
+			 * appear, so dropping the exclusive marker and mapping
+			 * it only R/O is fine.
+			 */
+			exclusive = false;
+		}
+	}
+
 	/*
 	 * Remove the swap entry and conditionally try to free up the swapcache.
 	 * We're already holding a reference on the page but haven't mapped it
@@ -3746,11 +3792,12 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
 	pte = mk_pte(page, vma->vm_page_prot);
 
 	/*
-	 * Same logic as in do_wp_page(); however, optimize for fresh pages
-	 * that are certainly not shared because we just allocated them without
-	 * exposing them to the swapcache.
+	 * Same logic as in do_wp_page(); however, optimize for pages that are
+	 * certainly not shared either because we just allocated them without
+	 * exposing them to the swapcache or because the swap entry indicates
+	 * exclusivity.
 	 */
-	if (!PageKsm(page) && (page != swapcache || page_count(page) == 1)) {
+	if (!PageKsm(page) && (exclusive || page_count(page) == 1)) {
 		if (vmf->flags & FAULT_FLAG_WRITE) {
 			pte = maybe_mkwrite(pte_mkdirty(pte), vma);
 			vmf->flags &= ~FAULT_FLAG_WRITE;
diff --git a/mm/rmap.c b/mm/rmap.c
index 9d2a7e11e8cc..5b1cafe90a86 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1643,14 +1643,15 @@ static bool try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
 				break;
 			}
 			/*
-			 * Note: We *don't* remember yet if the page was mapped
-			 * exclusively in the swap entry, so swapin code has
-			 * to re-determine that manually and might detect the
-			 * page as possibly shared, for example, if there are
-			 * other references on the page or if the page is under
-			 * writeback. We made sure that there are no GUP pins
-			 * on the page that would rely on it, so for GUP pins
-			 * this is fine.
+			 * Note: We *don't* remember if the page was mapped
+			 * exclusively in the swap pte if the architecture
+			 * doesn't support __HAVE_ARCH_PTE_SWP_EXCLUSIVE. In
+			 * that case, swapin code has to re-determine that
+			 * manually and might detect the page as possibly
+			 * shared, for example, if there are other references on
+			 * the page or if the page is under writeback. We made
+			 * sure that there are no GUP pins on the page that
+			 * would rely on it, so for GUP pins this is fine.
 			 */
 			if (list_empty(&mm->mmlist)) {
 				spin_lock(&mmlist_lock);
@@ -1661,6 +1662,8 @@ static bool try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
 			dec_mm_counter(mm, MM_ANONPAGES);
 			inc_mm_counter(mm, MM_SWAPENTS);
 			swp_pte = swp_entry_to_pte(entry);
+			if (anon_exclusive)
+				swp_pte = pte_swp_mkexclusive(swp_pte);
 			if (pte_soft_dirty(pteval))
 				swp_pte = pte_swp_mksoft_dirty(swp_pte);
 			if (pte_uffd_wp(pteval))
diff --git a/mm/swapfile.c b/mm/swapfile.c
index 493acb967b7a..200a0cd6c5e2 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1804,7 +1804,18 @@ static int unuse_pte(struct vm_area_struct *vma, pmd_t *pmd,
 	inc_mm_counter(vma->vm_mm, MM_ANONPAGES);
 	get_page(page);
 	if (page == swapcache) {
-		page_add_anon_rmap(page, vma, addr, RMAP_NONE);
+		rmap_t rmap_flags = RMAP_NONE;
+
+		/*
+		 * See do_swap_page(): PageWriteback() would be problematic.
+		 * However, we do a wait_on_page_writeback() just before this
+		 * call and have the page locked.
+		 */
+		VM_BUG_ON_PAGE(PageWriteback(page), page);
+		if (pte_swp_exclusive(*pte))
+			rmap_flags |= RMAP_EXCLUSIVE;
+
+		page_add_anon_rmap(page, vma, addr, rmap_flags);
 	} else { /* ksm created a completely new copy */
 		page_add_new_anon_rmap(page, vma, addr);
 		lru_cache_add_inactive_or_unevictable(page, vma);
