147 lines
6.8 KiB
Diff
147 lines
6.8 KiB
Diff
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Mon, 12 Apr 2021 23:56:42 -0700 (PDT)
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Date: Tue, 13 Apr 2021 00:56:18 -0600
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In-Reply-To: <20210413065633.2782273-1-yuzhao@google.com>
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Message-Id: <20210413065633.2782273-2-yuzhao@google.com>
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Subject: [PATCH v2 01/16] include/linux/memcontrol.h: do not warn in
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page_memcg_rcu() if !CONFIG_MEMCG
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From: Yu Zhao <yuzhao@google.com>
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To: linux-mm@kvack.org
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Cc: Alex Shi <alexs@kernel.org>, Andi Kleen <ak@linux.intel.com>,
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Andrew Morton <akpm@linux-foundation.org>,
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Benjamin Manes <ben.manes@gmail.com>,
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Dave Chinner <david@fromorbit.com>,
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Dave Hansen <dave.hansen@linux.intel.com>,
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Hillf Danton <hdanton@sina.com>, Jens Axboe <axboe@kernel.dk>,
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Johannes Weiner <hannes@cmpxchg.org>,
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Jonathan Corbet <corbet@lwn.net>,
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Joonsoo Kim <iamjoonsoo.kim@lge.com>,
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Matthew Wilcox <willy@infradead.org>,
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Mel Gorman <mgorman@suse.de>,
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Miaohe Lin <linmiaohe@huawei.com>,
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Michael Larabel <michael@michaellarabel.com>,
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Michal Hocko <mhocko@suse.com>,
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Michel Lespinasse <michel@lespinasse.org>,
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Rik van Riel <riel@surriel.com>,
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Roman Gushchin <guro@fb.com>,
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Rong Chen <rong.a.chen@intel.com>,
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SeongJae Park <sjpark@amazon.de>,
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Tim Chen <tim.c.chen@linux.intel.com>,
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Vlastimil Babka <vbabka@suse.cz>,
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Yang Shi <shy828301@gmail.com>,
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Ying Huang <ying.huang@intel.com>, Zi Yan <ziy@nvidia.com>,
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linux-kernel@vger.kernel.org, lkp@lists.01.org,
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page-reclaim@google.com, Yu Zhao <yuzhao@google.com>
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List-ID: <linux-kernel.vger.kernel.org>
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Archived-At: <https://lore.kernel.org/lkml/20210413065633.2782273-2-yuzhao@google.com/>
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List-Post: <mailto:linux-kernel@vger.kernel.org>
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page_memcg_rcu() warns on !rcu_read_lock_held() regardless of
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CONFIG_MEMCG. The following code is legit, but it triggers the warning
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when !CONFIG_MEMCG, since lock_page_memcg() and unlock_page_memcg()
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are 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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---
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include/linux/memcontrol.h | 1 -
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1 file changed, 1 deletion(-)
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diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
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index 0c04d39a7967..f13dc02cf277 100644
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--- a/include/linux/memcontrol.h
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+++ b/include/linux/memcontrol.h
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@@ -1077,7 +1077,6 @@ static inline struct mem_cgroup *page_memcg(struct page *page)
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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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--
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2.31.1.295.g9ea45b61b8-goog
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