Like teaching zap, mprotect, rmap walks .... code separately.
I'm, sure you'll find a way to break this down so I don't walk out of a
review with an headake ;)
:) I had smaller chunks earlier, but then ran into don't add the change unless
you
use the change problem
It's perfectly reasonable to have something like
mm/huge_memory: teach copy_huge_pmd() about huge device-private entries
mm/huge_memory: support splitting device-private folios
...
etc :)
[...]
Careful: There is is_readable_exclusive_migration_entry(). So don't
change the !is_readable_migration_entry(entry) to
is_writable_migration_entry(entry)(),
because it's wrong.
Ack, I assume you are referring to potential prot_none entries?
readable_exclusive are used to maintain the PageAnonExclusive bit right
now for migration entries. So it's not realted to prot_none.
[...]
- WARN_ONCE(1, "Non present huge pmd without pmd migration
enabled!");
+
+ if (!thp_migration_supported())
+ WARN_ONCE(1, "Non present huge pmd without pmd migration
enabled!");
+
+ if (is_pmd_device_private_entry(orig_pmd)) {
+ folio_remove_rmap_pmd(folio, &folio->page, vma);
+ WARN_ON_ONCE(folio_mapcount(folio) < 0);
Can we jsut move that into the folio_is_device_private() check below.
The check you mean?
The whole thing like
if (...) {
folio_remove_rmap_pmd(folio, &folio->page, vma);
WARN_ON_ONCE(folio_mapcount(folio) < 0);
folio_put(folio)
}
[...]
Why do we have to flush? pmd_clear() might be sufficient? In the PTE case we
use pte_clear().
Without the flush, other entities will not see the cleared pmd and isn't the
pte_clear() only
when should_defer_flush() is true?
It's a non-present page entry, so there should be no TLB entry to flush.
[...]
pmde = pmd_mksoft_dirty(pmde);
if (is_writable_migration_entry(entry))
diff --git a/mm/migrate_device.c b/mm/migrate_device.c
index e05e14d6eacd..0ed337f94fcd 100644
--- a/mm/migrate_device.c
+++ b/mm/migrate_device.c
@@ -136,6 +136,8 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp,
* page table entry. Other special swap entries are not
* migratable, and we ignore regular swapped page.
*/
+ struct folio *folio;
+
entry = pte_to_swp_entry(pte);
if (!is_device_private_entry(entry))
goto next;
@@ -147,6 +149,51 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp,
pgmap->owner != migrate->pgmap_owner)
goto next;
+ folio = page_folio(page);
+ if (folio_test_large(folio)) {
+ struct folio *new_folio;
+ struct folio *new_fault_folio = NULL;
+
+ /*
+ * The reason for finding pmd present with a
+ * device private pte and a large folio for the
+ * pte is partial unmaps. Split the folio now
+ * for the migration to be handled correctly
+ */
There are also other cases, like any VMA splits. Not sure if that makes a
difference,
the folio is PTE mapped.
Ack, I can clarify that the folio is just pte mapped or remove the comment
Sounds good.
--
Cheers
David / dhildenb
