+ mm-memcg-remove-rcu-locking-for-lock_page_lruvec-function-series.patch added to -mm tree

+ mm-memcg-remove-rcu-locking-for-lock_page_lruvec-function-series.patch added to -mm tree

[akpm]

The patch titled
     Subject: mm/memcg: remove rcu locking for lock_page_lruvec function series
has been added to the -mm tree.  Its filename is
     mm-memcg-remove-rcu-locking-for-lock_page_lruvec-function-series.patch

This patch should soon appear at
    https://ozlabs.org/~akpm/mmots/broken-out/mm-memcg-remove-rcu-locking-for-lock_page_lruvec-function-series.patch
and later at
    https://ozlabs.org/~akpm/mmotm/broken-out/mm-memcg-remove-rcu-locking-for-lock_page_lruvec-function-series.patch

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------------------------------------------------------
From: Alex Shi <alex.shi@linux.alibaba.com>
Subject: 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>
---

 mm/memcontrol.c |    6 ------
 1 file changed, 6 deletions(-)

--- a/mm/memcontrol.c~mm-memcg-remove-rcu-locking-for-lock_page_lruvec-function-series
+++ a/mm/memcontrol.c
@@ -1357,10 +1357,8 @@ struct lruvec *lock_page_lruvec(struct p
 	struct lruvec *lruvec;
 	struct pglist_data *pgdat = page_pgdat(page);
 
-	rcu_read_lock();
 	lruvec = mem_cgroup_page_lruvec(page, pgdat);
 	spin_lock(&lruvec->lru_lock);
-	rcu_read_unlock();
 
 	lruvec_memcg_debug(lruvec, page);
 
@@ -1372,10 +1370,8 @@ struct lruvec *lock_page_lruvec_irq(stru
 	struct lruvec *lruvec;
 	struct pglist_data *pgdat = page_pgdat(page);
 
-	rcu_read_lock();
 	lruvec = mem_cgroup_page_lruvec(page, pgdat);
 	spin_lock_irq(&lruvec->lru_lock);
-	rcu_read_unlock();
 
 	lruvec_memcg_debug(lruvec, page);
 
@@ -1387,10 +1383,8 @@ struct lruvec *lock_page_lruvec_irqsave(
 	struct lruvec *lruvec;
 	struct pglist_data *pgdat = page_pgdat(page);
 
-	rcu_read_lock();
 	lruvec = mem_cgroup_page_lruvec(page, pgdat);
 	spin_lock_irqsave(&lruvec->lru_lock, *flags);
-	rcu_read_unlock();
 
 	lruvec_memcg_debug(lruvec, page);
 
_

Patches currently in -mm which might be from alex.shi@linux.alibaba.com are

mm-memcg-revise-the-using-condition-of-lock_page_lruvec-function-series.patch
mm-memcg-remove-rcu-locking-for-lock_page_lruvec-function-series.patch
mm-vmscan-__isolate_lru_page_prepare-clean-up.patch
mm-compaction-remove-rcu_read_lock-during-page-compaction.patch