The patch titled
Subject: mm: remove superfluous __ClearPageActive()
has been added to the -mm tree. Its filename is
mm-remove-superfluous-__clearpageactive.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-remove-superfluous-__clearpageactive.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-remove-superfluous-__clearpageactive.patch
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------------------------------------------------------
From: Yu Zhao <yuzhao@xxxxxxxxxx>
Subject: mm: remove superfluous __ClearPageActive()
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 doesn't call SetPageActive()
on a page that doesn't have any reference left. Therefore, the race is
impossible 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.
Link: http://lkml.kernel.org/r/20200818184704.3625199-2-yuzhao@xxxxxxxxxx
Signed-off-by: Yu Zhao <yuzhao@xxxxxxxxxx>
Cc: Alexander Duyck <alexander.h.duyck@xxxxxxxxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Huang Ying <ying.huang@xxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Nicholas Piggin <npiggin@xxxxxxxxx>
Cc: Qian Cai <cai@xxxxxx>
Cc: Yang Shi <yang.shi@xxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/memremap.c | 2 --
mm/swap.c | 2 --
2 files changed, 4 deletions(-)
--- a/mm/memremap.c~mm-remove-superfluous-__clearpageactive
+++ a/mm/memremap.c
@@ -471,8 +471,6 @@ void free_devmap_managed_page(struct pag
return;
}
- /* Clear Active bit in case of parallel mark_page_accessed */
- __ClearPageActive(page);
__ClearPageWaiters(page);
mem_cgroup_uncharge(page);
--- a/mm/swap.c~mm-remove-superfluous-__clearpageactive
+++ a/mm/swap.c
@@ -900,8 +900,6 @@ void release_pages(struct page **pages,
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);
_
Patches currently in -mm which might be from yuzhao@xxxxxxxxxx are
mm-remove-activate_page-from-unuse_pte.patch
mm-remove-superfluous-__clearpageactive.patch
mm-remove-superfluous-__clearpagewaiters.patch
