On 08.09.25 02:04, Balbir Singh wrote:
subject:
"mm/rmap: rmap and migration support for device-private PMD entries"
Add device-private THP support to reverse mapping infrastructure,
enabling proper handling during migration and walk operations.
The key changes are:
- add_migration_pmd()/remove_migration_pmd(): Handle device-private
entries during folio migration and splitting
- page_vma_mapped_walk(): Recognize device-private THP entries during
VMA traversal operations
This change supports folio splitting and migration operations on
device-private entries.
Cc: Andrew Morton <a...@linux-foundation.org>
Cc: David Hildenbrand <da...@redhat.com>
Cc: Zi Yan <z...@nvidia.com>
Cc: Joshua Hahn <joshua.hah...@gmail.com>
Cc: Rakie Kim <rakie....@sk.com>
Cc: Byungchul Park <byungc...@sk.com>
Cc: Gregory Price <gou...@gourry.net>
Cc: Ying Huang <ying.hu...@linux.alibaba.com>
Cc: Alistair Popple <apop...@nvidia.com>
Cc: Oscar Salvador <osalva...@suse.de>
Cc: Lorenzo Stoakes <lorenzo.stoa...@oracle.com>
Cc: Baolin Wang <baolin.w...@linux.alibaba.com>
Cc: "Liam R. Howlett" <liam.howl...@oracle.com>
Cc: Nico Pache <npa...@redhat.com>
Cc: Ryan Roberts <ryan.robe...@arm.com>
Cc: Dev Jain <dev.j...@arm.com>
Cc: Barry Song <bao...@kernel.org>
Cc: Lyude Paul <ly...@redhat.com>
Cc: Danilo Krummrich <d...@kernel.org>
Cc: David Airlie <airl...@gmail.com>
Cc: Simona Vetter <sim...@ffwll.ch>
Cc: Ralph Campbell <rcampb...@nvidia.com>
Cc: Mika Penttilä <mpent...@redhat.com>
Cc: Matthew Brost <matthew.br...@intel.com>
Cc: Francois Dugast <francois.dug...@intel.com>
Signed-off-by: Balbir Singh <balb...@nvidia.com>
---
[...]
+++ b/mm/page_vma_mapped.c
@@ -250,12 +250,11 @@ bool page_vma_mapped_walk(struct page_vma_mapped_walk
*pvmw)
pvmw->ptl = pmd_lock(mm, pvmw->pmd);
pmde = *pvmw->pmd;
if (!pmd_present(pmde)) {
- swp_entry_t entry;
+ swp_entry_t entry = pmd_to_swp_entry(pmde);
if (!thp_migration_supported() ||
!(pvmw->flags & PVMW_MIGRATION))
return not_found(pvmw);
- entry = pmd_to_swp_entry(pmde);
if (!is_migration_entry(entry) ||
!check_pmd(swp_offset_pfn(entry), pvmw))
return not_found(pvmw);
Why this change? Looks unrelated.
@@ -277,6 +276,15 @@ bool page_vma_mapped_walk(struct page_vma_mapped_walk
*pvmw)
* cannot return prematurely, while zap_huge_pmd() has
* cleared *pmd but not decremented compound_mapcount().
Reminder to self: cleanup compound_mapcount() leftovers
*/
+ swp_entry_t entry;
+
+ entry = pmd_to_swp_entry(pmde);
swp_entry_t entry = pmd_to_swp_entry(pmde);
+
+ if (is_device_private_entry(entry)) {
+ pvmw->ptl = pmd_lock(mm, pvmw->pmd);
+ return true;
+ }
+
if ((pvmw->flags & PVMW_SYNC) &&
thp_vma_suitable_order(vma, pvmw->address,
PMD_ORDER) &&
diff --git a/mm/rmap.c b/mm/rmap.c
index 236ceff5b276..6de1baf7a4f1 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1063,8 +1063,10 @@ static int page_vma_mkclean_one(struct
page_vma_mapped_walk *pvmw)
} else {
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
pmd_t *pmd = pvmw->pmd;
- pmd_t entry;
+ pmd_t entry = pmdp_get(pmd);
+ if (!pmd_present(entry))
+ continue;
if (!pmd_dirty(*pmd) && !pmd_write(*pmd))
continue;
If you just did a pmdp_get() you should use it in these functions as
well. If not (cleanup later), do a straight *pmd like the others.
Apart from that nothing jumped at me.
--
Cheers
David / dhildenb
