From: Yu Kuai blkcg_print_one_stat() will be called for each blkg: - access blkg->iostat, which is freed from rcu callback blkg_free_workfn(); - access policy data from pd_stat_fn(), which is frred from pd_free_fn(), while pd_free_fn() can be called by removing blkcg or deactivating policy; The blkcg->lock can make sure iterated blkgs are still online, and both blkg->iostat and policy data for activated policy won't be freed. Prepare to convert protecting blkgs from request_queue with mutex. Signed-off-by: Yu Kuai --- block/blk-cgroup.c | 9 +++------ 1 file changed, 3 insertions(+), 6 deletions(-) diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c index f93de34fe87d..0f6039d468a6 100644 --- a/block/blk-cgroup.c +++ b/block/blk-cgroup.c @@ -1242,13 +1242,10 @@ static int blkcg_print_stat(struct seq_file *sf, void *v) else css_rstat_flush(&blkcg->css); - rcu_read_lock(); - hlist_for_each_entry_rcu(blkg, &blkcg->blkg_list, blkcg_node) { - spin_lock_irq(&blkg->q->queue_lock); + guard(spinlock)(&blkcg->lock); + hlist_for_each_entry(blkg, &blkcg->blkg_list, blkcg_node) blkcg_print_one_stat(blkg, sf); - spin_unlock_irq(&blkg->q->queue_lock); - } - rcu_read_unlock(); + return 0; } -- 2.51.0