130 lines
6.0 KiB
Diff
130 lines
6.0 KiB
Diff
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Fri, 12 Mar 2021 23:57:57 -0800 (PST)
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Date: Sat, 13 Mar 2021 00:57:34 -0700
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In-Reply-To: <20210313075747.3781593-1-yuzhao@google.com>
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Message-Id: <20210313075747.3781593-2-yuzhao@google.com>
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Subject: [PATCH v1 01/14] 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 <alex.shi@linux.alibaba.com>,
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Andrew Morton <akpm@linux-foundation.org>,
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Dave Hansen <dave.hansen@linux.intel.com>,
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Hillf Danton <hdanton@sina.com>,
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Johannes Weiner <hannes@cmpxchg.org>,
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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>, Michal Hocko <mhocko@suse.com>,
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Roman Gushchin <guro@fb.com>, Vlastimil Babka <vbabka@suse.cz>,
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Wei Yang <richard.weiyang@linux.alibaba.com>,
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Yang Shi <shy828301@gmail.com>,
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Ying Huang <ying.huang@intel.com>,
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linux-kernel@vger.kernel.org, page-reclaim@google.com,
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Yu Zhao <yuzhao@google.com>
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Content-Type: text/plain; charset="UTF-8"
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Precedence: bulk
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List-ID: <linux-kernel.vger.kernel.org>
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Archived-At: <https://lore.kernel.org/lkml/20210313075747.3781593-2-yuzhao@google.com/>
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List-Archive: <https://lore.kernel.org/lkml/>
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List-Post: <mailto:linux-kernel@vger.kernel.org>
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We want to make sure the rcu lock is held while using
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page_memcg_rcu(). But having a WARN_ON_ONCE() in page_memcg_rcu() when
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!CONFIG_MEMCG is superfluous because of the following legit use case:
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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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This patch removes the WARN_ON_ONCE() from page_memcg_rcu() for the
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!CONFIG_MEMCG case.
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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 e6dc793d587d..f325aeb4b4e8 100644
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--- a/include/linux/memcontrol.h
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+++ b/include/linux/memcontrol.h
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@@ -1079,7 +1079,6 @@ 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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2.31.0.rc2.261.g7f71774620-goog
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