immortalwrt-mt798x/target/linux/generic/backport-5.4/020-02-BACKPORT-mm-remove-superfluous-__ClearPageActive.patch

70 lines
2.5 KiB
Diff

From 45e277af28e0517cea1581d4f7f0c48d116314a9 Mon Sep 17 00:00:00 2001
From: Yu Zhao <yuzhao@google.com>
Date: Sat, 18 Jul 2020 01:46:37 -0600
Subject: [PATCH] BACKPORT: 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.
Signed-off-by: Yu Zhao <yuzhao@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Yang Shi <shy828301@gmail.com>
Cc: Alexander Duyck <alexander.h.duyck@linux.intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Huang Ying <ying.huang@intel.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Qian Cai <cai@lca.pw>
Link: http://lkml.kernel.org/r/20200818184704.3625199-2-yuzhao@google.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
(cherry picked from commit 6f4dd8de4835563de9bae797ce1d7a13465a7a7d)
BUG=b:123039911
TEST=Built
Change-Id: I3e50ae28408b2936b1eb72210b3046eac8485701
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/kernel/+/2940109
Tested-by: Yu Zhao <yuzhao@chromium.org>
Reviewed-by: Sonny Rao <sonnyrao@chromium.org>
Commit-Queue: Yu Zhao <yuzhao@chromium.org>
---
mm/memremap.c | 2 --
mm/swap.c | 2 --
2 files changed, 4 deletions(-)
--- a/mm/memremap.c
+++ b/mm/memremap.c
@@ -419,8 +419,6 @@ void __put_devmap_managed_page(struct pa
* holds a reference on the page.
*/
if (count == 1) {
- /* Clear Active bit in case of parallel mark_page_accessed */
- __ClearPageActive(page);
__ClearPageWaiters(page);
mem_cgroup_uncharge(page);
--- a/mm/swap.c
+++ b/mm/swap.c
@@ -829,8 +829,6 @@ 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);