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: 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>

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 5bf98d0a22c9a7107b76040b49fccd6aec353128..6114a1fc6c688a8cb5600f79508c356986f2c2ea 100644 (file)
--- 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);
        }
 }