Commit 814bc1de authored by Yu Zhao's avatar Yu Zhao Committed by Andrew Morton
Browse files

mm/mglru: make memcg_lru->lock irq safe 

lru_gen_rotate_memcg() can happen in softirq if memory.soft_limit_in_bytes
is set.  This requires memcg_lru->lock to be irq safe.  Lockdep warns on
this.

This problem only affects memcg v1.

Link: https://lkml.kernel.org/r/20230619193821.2710944-1-yuzhao@google.com


Fixes: e4dde56c ("mm: multi-gen LRU: per-node lru_gen_folio lists")
Signed-off-by: default avatarYu Zhao <yuzhao@google.com>
Reported-by: default avatar <syzbot+87c490fd2be656269b6a@syzkaller.appspotmail.com>
Closes: https://syzkaller.appspot.com/bug?extid=87c490fd2be656269b6a


Reviewed-by: default avatarYosry Ahmed <yosryahmed@google.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 0518dbe9

mm/vmscan.c

+7 −6
Original line number Diff line number Diff line
@@ -4728,10 +4728,11 @@ static void lru_gen_rotate_memcg(struct lruvec *lruvec, int op) 
{

	int seg;

	int old, new;

	unsigned long flags;

	int bin = get_random_u32_below(MEMCG_NR_BINS);

	struct pglist_data *pgdat = lruvec_pgdat(lruvec);



	spin_lock(&pgdat->memcg_lru.lock);

	spin_lock_irqsave(&pgdat->memcg_lru.lock, flags);



	VM_WARN_ON_ONCE(hlist_nulls_unhashed(&lruvec->lrugen.list));
@@ -4766,7 +4767,7 @@ static void lru_gen_rotate_memcg(struct lruvec *lruvec, int op) 
	if (!pgdat->memcg_lru.nr_memcgs[old] && old == get_memcg_gen(pgdat->memcg_lru.seq))

		WRITE_ONCE(pgdat->memcg_lru.seq, pgdat->memcg_lru.seq + 1);



	spin_unlock(&pgdat->memcg_lru.lock);

	spin_unlock_irqrestore(&pgdat->memcg_lru.lock, flags);

}



void lru_gen_online_memcg(struct mem_cgroup *memcg)
@@ -4779,7 +4780,7 @@ void lru_gen_online_memcg(struct mem_cgroup *memcg) 
		struct pglist_data *pgdat = NODE_DATA(nid);

		struct lruvec *lruvec = get_lruvec(memcg, nid);



		spin_lock(&pgdat->memcg_lru.lock);

		spin_lock_irq(&pgdat->memcg_lru.lock);



		VM_WARN_ON_ONCE(!hlist_nulls_unhashed(&lruvec->lrugen.list));
@@ -4790,7 +4791,7 @@ void lru_gen_online_memcg(struct mem_cgroup *memcg) 


		lruvec->lrugen.gen = gen;



		spin_unlock(&pgdat->memcg_lru.lock);

		spin_unlock_irq(&pgdat->memcg_lru.lock);

	}

}
@@ -4814,7 +4815,7 @@ void lru_gen_release_memcg(struct mem_cgroup *memcg) 
		struct pglist_data *pgdat = NODE_DATA(nid);

		struct lruvec *lruvec = get_lruvec(memcg, nid);



		spin_lock(&pgdat->memcg_lru.lock);

		spin_lock_irq(&pgdat->memcg_lru.lock);



		VM_WARN_ON_ONCE(hlist_nulls_unhashed(&lruvec->lrugen.list));
@@ -4826,7 +4827,7 @@ void lru_gen_release_memcg(struct mem_cgroup *memcg) 
		if (!pgdat->memcg_lru.nr_memcgs[gen] && gen == get_memcg_gen(pgdat->memcg_lru.seq))

			WRITE_ONCE(pgdat->memcg_lru.seq, pgdat->memcg_lru.seq + 1);



		spin_unlock(&pgdat->memcg_lru.lock);

		spin_unlock_irq(&pgdat->memcg_lru.lock);

	}

}