[PATCH v5 10/13] mm: Add helpers to create device private entries from struct pages

Jordan Niethe
2026-01-30T11:12:34Z

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
v2:
- Add flag param
v3:
- No change
---
include/linux/swapops.h | 24 ++++++++++++++++++++++++
mm/huge_memory.c | 14 ++++++--------
mm/migrate.c | 6 ++----
mm/migrate_device.c | 12 ++++--------
4 files changed, 36 insertions(+), 20 deletions(-)

diff --git a/include/linux/swapops.h b/include/linux/swapops.h
index 8b39983792ea..080e27da6b47 100644
--- a/include/linux/swapops.h
+++ b/include/linux/swapops.h
@@ -138,11 +138,23 @@ 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,
+ pgoff_t flags)
+{
+ return swp_entry(SWP_DEVICE_READ, page_to_pfn(page) | flags);
+}
+
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,
+ pgoff_t flags)
+{
+ return swp_entry(SWP_DEVICE_WRITE, page_to_pfn(page) | flags);
+}
+
static inline swp_entry_t make_device_exclusive_entry(pgoff_t offset)
{
return swp_entry(SWP_DEVICE_EXCLUSIVE, offset);
@@ -169,11 +181,23 @@ 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,
+ pgoff_t flags)
+{
+ 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,
+ pgoff_t flags)
+{
+ 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 e3a448cdb34d..03f1f13bb24c 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -3219,11 +3219,11 @@ 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, 0);
else
- swp_entry = make_readable_device_private_entry(
- page_to_pfn(page + i));
+ swp_entry = make_readable_device_private_entry_from_page(
+ page + i, 0);
/*
* Young and dirty bits are not progated via swp_entry
*/
@@ -4950,11 +4950,9 @@ 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, 0);
else
- entry = make_readable_device_private_entry(
- page_to_pfn(new));
+ entry = make_readable_device_private_entry_from_page(new, 0);
pmde = swp_entry_to_pmd(entry);

if (pmd_swp_soft_dirty(*pvmw->pmd))
diff --git a/mm/migrate.c b/mm/migrate.c
index 4688b9e38cd2..24e3ebbab1e1 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, 0);
else
- entry = make_readable_device_private_entry(
- page_to_pfn(new));
+ entry = make_readable_device_private_entry_from_page(new, 0);
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 c876526ac6a3..0ca6f78df0e2 100644
--- a/mm/migrate_device.c
+++ b/mm/migrate_device.c
@@ -836,11 +836,9 @@ 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, 0);
else
- swp_entry = make_readable_device_private_entry(
- page_to_pfn(page));
+ swp_entry = make_readable_device_private_entry_from_page(page, 0);
entry = swp_entry_to_pmd(swp_entry);
} else {
if (folio_is_zone_device(folio) &&
@@ -1033,11 +1031,9 @@ 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, 0);
else
- swp_entry = make_readable_device_private_entry(
- page_to_pfn(page));
+ swp_entry = make_readable_device_private_entry_from_page(page, 0);
entry = swp_entry_to_pte(swp_entry);
} else {
if (folio_is_zone_device(folio) &&
--
2.34.1