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58 lines
1.8 KiB
Diff
58 lines
1.8 KiB
Diff
From 5e63b5c96495b43418b56abc29abf15438fdd2fd Mon Sep 17 00:00:00 2001
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From: Yu Zhao <yuzhao@google.com>
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Date: Tue, 29 Sep 2020 14:54:14 -0600
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Subject: [PATCH] BACKPORT: FROMLIST: include/linux/mm.h: do not warn in
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page_memcg_rcu() if !CONFIG_MEMCG
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page_memcg_rcu() warns on !rcu_read_lock_held() regardless of
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CONFIG_MEMCG. The following legit code trips the warning when
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!CONFIG_MEMCG, since lock_page_memcg() and unlock_page_memcg() are
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empty for this config.
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memcg = lock_page_memcg(page1)
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(rcu_read_lock() if CONFIG_MEMCG=y)
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do something to page1
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if (page_memcg_rcu(page2) == memcg)
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do something to page2 too as it cannot be migrated away from the
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memcg either.
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unlock_page_memcg(page1)
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(rcu_read_unlock() if CONFIG_MEMCG=y)
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Locking/unlocking rcu consistently for both configs is rigorous but it
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also forces unnecessary locking upon users who have no interest in
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CONFIG_MEMCG.
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This patch removes the assertion for !CONFIG_MEMCG, because
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page_memcg_rcu() has a few callers and there are no concerns regarding
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their correctness at the moment.
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Signed-off-by: Yu Zhao <yuzhao@google.com>
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Tested-by: Konstantin Kharlamov <Hi-Angel@yandex.ru>
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(am from https://lore.kernel.org/patchwork/patch/1432176/)
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BUG=b:123039911
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TEST=Built
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Change-Id: I0d3d8d5cfc69827d2214641d689480cded0557e2
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Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/kernel/+/2951282
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Reviewed-by: Yu Zhao <yuzhao@chromium.org>
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Commit-Queue: Yu Zhao <yuzhao@chromium.org>
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Tested-by: Yu Zhao <yuzhao@chromium.org>
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---
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include/linux/mm.h | 1 -
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1 file changed, 1 deletion(-)
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--- a/include/linux/mm.h
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+++ b/include/linux/mm.h
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@@ -1329,7 +1329,6 @@ static inline struct mem_cgroup *page_me
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}
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static inline struct mem_cgroup *page_memcg_rcu(struct page *page)
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{
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- WARN_ON_ONCE(!rcu_read_lock_held());
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return NULL;
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}
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#endif
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