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Subject[PATCH 2/3] mm: remove superfluous __ClearPageActive()
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To activate a page, mark_page_accessed() always holds a reference
on it. It either gets a new reference when adding a page to
lru_pvecs.activate_page or reuses an existing one it previously
got when it added a page to lru_pvecs.lru_add. So it can't call
SetPageActive() on a page that doesn't have any reference left.
Therefore, the race is impossible, not these days (I didn't brother
to dig into its history).

For other paths, namely reclaim and migration, a reference count is
always held while calling SetPageActive() on a page.

SetPageSlabPfmemalloc() also uses SetPageActive(), but it's irrelevant
to LRU pages.

Signed-off-by: Yu Zhao <yuzhao@google.com>
---
mm/memremap.c | 2 --
mm/swap.c | 2 --
2 files changed, 4 deletions(-)

diff --git a/mm/memremap.c b/mm/memremap.c
index 03e38b7a38f1..3a06eb91cb59 100644
--- a/mm/memremap.c
+++ b/mm/memremap.c
@@ -451,8 +451,6 @@ void free_devmap_managed_page(struct page *page)
return;
}

- /* Clear Active bit in case of parallel mark_page_accessed */
- __ClearPageActive(page);
__ClearPageWaiters(page);

mem_cgroup_uncharge(page);
diff --git a/mm/swap.c b/mm/swap.c
index de257c0a89b1..1f223a02549d 100644
--- a/mm/swap.c
+++ b/mm/swap.c
@@ -898,8 +898,6 @@ void release_pages(struct page **pages, int nr)
del_page_from_lru_list(page, lruvec, page_off_lru(page));
}

- /* Clear Active bit in case of parallel mark_page_accessed */
- __ClearPageActive(page);
__ClearPageWaiters(page);

list_add(&page->lru, &pages_to_free);
--
2.28.0.236.gb10cc79966-goog
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