mm/memcg: remove rcu locking for lock_page_lruvec function series
lock_page_lruvec() and its variants used rcu_read_lock() with the intention of safeguarding against the mem_cgroup being destroyed concurrently; but so long as they are called under the specified conditions (as they are), there is no way for the page's mem_cgroup to be destroyed. Delete the unnecessary rcu_read_lock() and _unlock(). Hugh Dickins polished the commit log. Thanks a lot! Link: https://lkml.kernel.org/r/1608614453-10739-2-git-send-email-alex.shi@linux.alibaba.com 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: Michal Hocko <mhocko@kernel.org> Cc: Vladimir Davydov <vdavydov.dev@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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@ -1357,10 +1357,8 @@ struct lruvec *lock_page_lruvec(struct page *page)
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struct lruvec *lruvec;
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struct pglist_data *pgdat = page_pgdat(page);
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rcu_read_lock();
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lruvec = mem_cgroup_page_lruvec(page, pgdat);
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spin_lock(&lruvec->lru_lock);
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rcu_read_unlock();
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lruvec_memcg_debug(lruvec, page);
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@ -1372,10 +1370,8 @@ struct lruvec *lock_page_lruvec_irq(struct page *page)
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struct lruvec *lruvec;
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struct pglist_data *pgdat = page_pgdat(page);
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rcu_read_lock();
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lruvec = mem_cgroup_page_lruvec(page, pgdat);
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spin_lock_irq(&lruvec->lru_lock);
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rcu_read_unlock();
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lruvec_memcg_debug(lruvec, page);
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@ -1387,10 +1383,8 @@ struct lruvec *lock_page_lruvec_irqsave(struct page *page, unsigned long *flags)
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struct lruvec *lruvec;
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struct pglist_data *pgdat = page_pgdat(page);
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rcu_read_lock();
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lruvec = mem_cgroup_page_lruvec(page, pgdat);
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spin_lock_irqsave(&lruvec->lru_lock, *flags);
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rcu_read_unlock();
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lruvec_memcg_debug(lruvec, page);
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