[PATCH 4/4] mm/rmap: try_to_migrate() skip zone_device !device_private

Hugh Dickins
2021-07-07T20:13:41Z

I know nothing about zone_device pages and !device_private pages; but
if try_to_migrate_one() will do nothing for them, then it's better that
try_to_migrate() filter them first, than trawl through all their vmas.

Signed-off-by: Hugh Dickins <hughd@google.com>
---
mm/rmap.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/mm/rmap.c b/mm/rmap.c
index 1235368f0628..795f9d5f8386 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1703,9 +1703,6 @@ static bool try_to_migrate_one(struct page *page, struct vm_area_struct *vma,
struct mmu_notifier_range range;
enum ttu_flags flags = (enum ttu_flags)(long)arg;

- if (is_zone_device_page(page) && !is_device_private_page(page))
- return true;
-
/*
* When racing against e.g. zap_pte_range() on another cpu,
* in between its ptep_get_and_clear_full() and page_remove_rmap(),
@@ -1944,6 +1941,9 @@ void try_to_migrate(struct page *page, enum ttu_flags flags)
TTU_SYNC)))
return;

+ if (is_zone_device_page(page) && !is_device_private_page(page))
+ return;
+
/*
* During exec, a temporary VMA is setup and later moved.
* The VMA is moved under the anon_vma lock but not the
--
2.26.2