From: Alex Shi <alex.shi@linux.alibaba.com>
To: hughd@google.com
Cc: Johannes Weiner <hannes@cmpxchg.org>,
Andrew Morton <akpm@linux-foundation.org>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: [PATCH v2 3/3] mm/compaction: remove rcu_read_lock during page compaction
Date: Tue, 22 Dec 2020 13:20:53 +0800 [thread overview]
Message-ID: <1608614453-10739-3-git-send-email-alex.shi@linux.alibaba.com> (raw)
In-Reply-To: <1608614453-10739-1-git-send-email-alex.shi@linux.alibaba.com>
isolate_migratepages_block() used rcu_read_lock() with the intention
of safeguarding against the mem_cgroup being destroyed concurrently;
but its TestClearPageLRU already protects against that. Delete the
unnecessary rcu_read_lock() and _unlock().
Hugh Dickin' helped on commit log polishing, Thanks!
Signed-off-by: Alex Shi <alex.shi@linux.alibaba.com>
Acked-by: Hugh Dickins <hughd@google.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-mm@kvack.org
Cc: linux-kernel@vger.kernel.org
---
mm/compaction.c | 5 +----
1 file changed, 1 insertion(+), 4 deletions(-)
diff --git a/mm/compaction.c b/mm/compaction.c
index 8049d3530812..02af220fb992 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -995,7 +995,6 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
if (!TestClearPageLRU(page))
goto isolate_fail_put;
- rcu_read_lock();
lruvec = mem_cgroup_page_lruvec(page, pgdat);
/* If we already hold the lock, we can skip some rechecking */
@@ -1005,7 +1004,6 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
compact_lock_irqsave(&lruvec->lru_lock, &flags, cc);
locked = lruvec;
- rcu_read_unlock();
lruvec_memcg_debug(lruvec, page);
@@ -1026,8 +1024,7 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
SetPageLRU(page);
goto isolate_fail_put;
}
- } else
- rcu_read_unlock();
+ }
/* The whole page is taken off the LRU; skip the tail pages. */
if (PageCompound(page))
--
2.29.GIT
prev parent reply other threads:[~2020-12-22 5:23 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-22 5:20 [PATCH v2 1/3] mm/memcg: revise the using condition of lock_page_lruvec function series Alex Shi
2020-12-22 5:20 ` [PATCH v2 2/3] mm/memcg: remove rcu locking for " Alex Shi
2020-12-22 8:00 ` Alex Shi
2020-12-22 5:20 ` Alex Shi [this message]
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