[PATCH v1 5/8] mm: Add helpers to create device private entries from struct pages

[Jordan Niethe <jniethe@nvidia.com>]

To create a new device private entry for a given struct page, that page
is first converted to its pfn, before passing the pfn to
make_writable_device_private_entry() (and friends).

A future change will remove device private pages from the physical
address space. This will mean that device private pages no longer have a
pfn and must be handled separately.

Prepare for this with a new set of helpers:

- make_readable_device_private_entry_from_page()
- make_writable_device_private_entry_from_page()

These helpers take a struct page as parameter instead of a pfn. This
will allow more flexibility for handling the swap offset field
differently for device private pages.

Signed-off-by: Jordan Niethe <jniethe@nvidia.com>
---
v1:
  - New to series
---
 include/linux/swapops.h | 20 ++++++++++++++++++++
 mm/huge_memory.c        | 14 ++++++--------
 mm/memory.c             |  4 ++--
 mm/migrate.c            |  6 ++----
 mm/migrate_device.c     | 12 ++++--------
 5 files changed, 34 insertions(+), 22 deletions(-)

diff --git a/include/linux/swapops.h b/include/linux/swapops.h
index 2bd01f97b4f0..ddf2763d69e9 100644
--- a/include/linux/swapops.h
+++ b/include/linux/swapops.h
@@ -138,11 +138,21 @@ static inline swp_entry_t make_readable_device_private_entry(pgoff_t offset)
 	return swp_entry(SWP_DEVICE_READ, offset);
 }
 
+static inline swp_entry_t make_readable_device_private_entry_from_page(struct page *page)
+{
+	return swp_entry(SWP_DEVICE_READ, page_to_pfn(page));
+}
+
 static inline swp_entry_t make_writable_device_private_entry(pgoff_t offset)
 {
 	return swp_entry(SWP_DEVICE_WRITE, offset);
 }
 
+static inline swp_entry_t make_writable_device_private_entry_from_page(struct page *page)
+{
+	return swp_entry(SWP_DEVICE_WRITE, page_to_pfn(page));
+}
+
 static inline swp_entry_t make_device_exclusive_entry(pgoff_t offset)
 {
 	return swp_entry(SWP_DEVICE_EXCLUSIVE, offset);
@@ -191,11 +201,21 @@ static inline swp_entry_t make_readable_device_private_entry(pgoff_t offset)
 	return swp_entry(0, 0);
 }
 
+static inline swp_entry_t make_readable_device_private_entry_from_page(struct page *page)
+{
+	return swp_entry(0, 0);
+}
+
 static inline swp_entry_t make_writable_device_private_entry(pgoff_t offset)
 {
 	return swp_entry(0, 0);
 }
 
+static inline swp_entry_t make_writable_device_private_entry_from_page(struct page *page)
+{
+	return swp_entry(0, 0);
+}
+
 static inline swp_entry_t make_device_exclusive_entry(pgoff_t offset)
 {
 	return swp_entry(0, 0);
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index bbfe5e87884a..31ea473cbcbd 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -3225,11 +3225,11 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
 			 * is false.
 			 */
 			if (write)
-				swp_entry = make_writable_device_private_entry(
-							page_to_pfn(page + i));
+				swp_entry = make_writable_device_private_entry_from_page(
+							page + i);
 			else
-				swp_entry = make_readable_device_private_entry(
-							page_to_pfn(page + i));
+				swp_entry = make_readable_device_private_entry_from_page(
+							page + i);
 			/*
 			 * Young and dirty bits are not progated via swp_entry
 			 */
@@ -4956,11 +4956,9 @@ void remove_migration_pmd(struct page_vma_mapped_walk *pvmw, struct page *new)
 		swp_entry_t entry;
 
 		if (pmd_write(pmde))
-			entry = make_writable_device_private_entry(
-							page_to_pfn(new));
+			entry = make_writable_device_private_entry_from_page(new);
 		else
-			entry = make_readable_device_private_entry(
-							page_to_pfn(new));
+			entry = make_readable_device_private_entry_from_page(new);
 		pmde = swp_entry_to_pmd(entry);
 
 		if (pmd_swp_soft_dirty(*pvmw->pmd))
diff --git a/mm/memory.c b/mm/memory.c
index 8e5e305bc2dc..076d7acb7267 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1005,8 +1005,8 @@ copy_nonpresent_pte(struct mm_struct *dst_mm, struct mm_struct *src_mm,
 		 */
 		if (softleaf_is_device_private_write(entry) &&
 		    is_cow_mapping(vm_flags)) {
-			entry = make_readable_device_private_entry(
-							swp_offset(entry));
+			entry = make_readable_device_private_entry
+							(swp_offset(entry));
 			pte = swp_entry_to_pte(entry);
 			if (pte_swp_uffd_wp(orig_pte))
 				pte = pte_swp_mkuffd_wp(pte);
diff --git a/mm/migrate.c b/mm/migrate.c
index 5169f9717f60..9ec9bcd37882 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -399,11 +399,9 @@ static bool remove_migration_pte(struct folio *folio,
 
 		if (unlikely(is_device_private_page(new))) {
 			if (pte_write(pte))
-				entry = make_writable_device_private_entry(
-							page_to_pfn(new));
+				entry = make_writable_device_private_entry_from_page(new);
 			else
-				entry = make_readable_device_private_entry(
-							page_to_pfn(new));
+				entry = make_readable_device_private_entry_from_page(new);
 			pte = softleaf_to_pte(entry);
 			if (pte_swp_soft_dirty(old_pte))
 				pte = pte_swp_mksoft_dirty(pte);
diff --git a/mm/migrate_device.c b/mm/migrate_device.c
index 7eef21d63364..5cc58a5876a0 100644
--- a/mm/migrate_device.c
+++ b/mm/migrate_device.c
@@ -842,11 +842,9 @@ static int migrate_vma_insert_huge_pmd_page(struct migrate_vma *migrate,
 		swp_entry_t swp_entry;
 
 		if (vma->vm_flags & VM_WRITE)
-			swp_entry = make_writable_device_private_entry(
-						page_to_pfn(page));
+			swp_entry = make_writable_device_private_entry_from_page(page);
 		else
-			swp_entry = make_readable_device_private_entry(
-						page_to_pfn(page));
+			swp_entry = make_readable_device_private_entry_from_page(page);
 		entry = swp_entry_to_pmd(swp_entry);
 	} else {
 		if (folio_is_zone_device(folio) &&
@@ -1039,11 +1037,9 @@ static void migrate_vma_insert_page(struct migrate_vma *migrate,
 		swp_entry_t swp_entry;
 
 		if (vma->vm_flags & VM_WRITE)
-			swp_entry = make_writable_device_private_entry(
-						page_to_pfn(page));
+			swp_entry = make_writable_device_private_entry_from_page(page);
 		else
-			swp_entry = make_readable_device_private_entry(
-						page_to_pfn(page));
+			swp_entry = make_readable_device_private_entry_from_page(page);
 		entry = swp_entry_to_pte(swp_entry);
 	} else {
 		if (folio_is_zone_device(folio) &&
-- 
2.34.1