[PATCH mm-unstable v1] mm/mglru: make memcg_lru->lock irq safe

[Yu Zhao]

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.

This problem only affects memcg v1.

Reported-by: syzbot+87c490fd2be656269b6a@xxxxxxxxxxxxxxxxxxxxxxxxx
Closes: https://syzkaller.appspot.com/bug?extid=87c490fd2be656269b6a
Fixes: e4dde56cd208 ("mm: multi-gen LRU: per-node lru_gen_folio lists")
Signed-off-by: Yu Zhao <yuzhao@xxxxxxxxxx>
---
 mm/vmscan.c | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 45d17c7cc555..27f90896f789 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -4759,10 +4759,11 @@ 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));
 
@@ -4797,7 +4798,7 @@ 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)
@@ -4810,7 +4811,7 @@ 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));
 
@@ -4821,7 +4822,7 @@ 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);
 	}
 }
 
@@ -4845,7 +4846,7 @@ 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));
 
@@ -4857,7 +4858,7 @@ 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);
 	}
 }
 
-- 
2.41.0.185.g7c58973941-goog