+ mm-list_lru-remove-holding-lru-lock.patch added to -mm tree

The patch titled
     Subject: mm: list_lru: remove holding lru lock
has been added to the -mm tree.  Its filename is
     mm-list_lru-remove-holding-lru-lock.patch

This patch should soon appear at
    https://ozlabs.org/~akpm/mmots/broken-out/mm-list_lru-remove-holding-lru-lock.patch
and later at
    https://ozlabs.org/~akpm/mmotm/broken-out/mm-list_lru-remove-holding-lru-lock.patch

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------------------------------------------------------
From: Muchun Song <redacted>
Subject: mm: list_lru: remove holding lru lock

Since commit e5bc3af7734f ("rcu: Consolidate PREEMPT and !PREEMPT
synchronize_rcu()"), the critical section of spin lock can serve as an
RCU read-side critical section which already allows readers that hold
nlru->lock to avoid taking rcu lock.  So just remove holding lock.

Link: https://lkml.kernel.org/r/20211025124534.56345-1-songmuchun@bytedance.com
Signed-off-by: Muchun Song <redacted>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Roman Gushchin <redacted>
Cc: Shakeel Butt <redacted>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/list_lru.c |   11 -----------
 1 file changed, 11 deletions(-)

--- a/mm/list_lru.c~mm-list_lru-remove-holding-lru-lock
+++ a/mm/list_lru.c

@@ -398,18 +398,7 @@ static int memcg_update_list_lru_node(st
 	}
 
 	memcpy(&new->lru, &old->lru, flex_array_size(new, lru, old_size));
-
-	/*
-	 * The locking below allows readers that hold nlru->lock avoid taking
-	 * rcu_read_lock (see list_lru_from_memcg_idx).
-	 *
-	 * Since list_lru_{add,del} may be called under an IRQ-safe lock,
-	 * we have to use IRQ-safe primitives here to avoid deadlock.
-	 */
-	spin_lock_irq(&nlru->lock);
 	rcu_assign_pointer(nlru->memcg_lrus, new);
-	spin_unlock_irq(&nlru->lock);
-
 	kvfree_rcu(old, rcu);
 	return 0;
 }

_

Patches currently in -mm which might be from songmuchun@bytedance.com are

mm-list_lru-remove-holding-lru-lock.patch
mm-list_lru-fix-the-return-value-of-list_lru_count_one.patch
mm-memcontrol-remove-kmemcg_id-reparenting.patch
mm-memcontrol-remove-the-kmem-states.patch