On 5/11/2022 9:58 PM, Alistair Popple wrote:
Alex Sierra <alex.sierra@xxxxxxx> writes:
[...]
diff --git a/mm/rmap.c b/mm/rmap.c
index fedb82371efe..d57102cd4b43 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1995,7 +1995,8 @@ void try_to_migrate(struct folio *folio, enum ttu_flags flags)
TTU_SYNC)))
return;
- if (folio_is_zone_device(folio) && !folio_is_device_private(folio))
+ if (folio_is_zone_device(folio) &&
+ (!folio_is_device_private(folio) && !folio_is_device_coherent(folio)))
return;
/*
I vaguely recall commenting on this previously, or at least intending
to. In try_to_migrate_one() we have this:
if (folio_is_zone_device(folio)) {
unsigned long pfn = folio_pfn(folio);
swp_entry_t entry;
pte_t swp_pte;
/*
* Store the pfn of the page in a special migration
* pte. do_swap_page() will wait until the migration
* pte is removed and then restart fault handling.
*/
entry = pte_to_swp_entry(pteval);
if (is_writable_device_private_entry(entry))
entry = make_writable_migration_entry(pfn);
else
entry = make_readable_migration_entry(pfn);
swp_pte = swp_entry_to_pte(entry);
The check in try_to_migrate() guarantees that if folio_is_zone_device()
is true this must be a DEVICE_PRIVATE page and it treats it as such by
assuming there is a special device private swap entry there.
Relying on that assumption seems bad, and I have no idea why I didn't
just use is_device_private_page() originally but I think the fix is just
to change this to:
if (folio_is_device_private(folio))
Thanks Alistair. This worked fine. I'll drop patch 4 and update this
patch in the next series version.
Regards,
Alex Sierra
And let DEVICE_COHERENT pages fall through to normal page processing.
- Alistair
