[PATCH 6.4 725/800] mm/mglru: make memcg_lru->lock irq safe

Greg Kroah-Hartman
2023-07-16T20:28:14Z

From: Yu Zhao <yuzhao@google.com>

commit 814bc1de03ea4361101408e63a68e4b82aef22cb upstream.

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: e4dde56cd208 ("mm: multi-gen LRU: per-node lru_gen_folio lists")
Signed-off-by: Yu Zhao <yuzhao@google.com>
Reported-by: syzbot+87c490fd2be656269b6a@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=87c490fd2be656269b6a
Reviewed-by: Yosry Ahmed <yosryahmed@google.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
mm/vmscan.c | 13 +++++++------
1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 5bf98d0a22c9..6114a1fc6c68 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -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);
}
}

--
2.41.0