From 14a6e2eb7df5c7897c15b109cba29ab0c4a791b6 Mon Sep 17 00:00:00 2001 From: Jinke Han Date: Wed, 20 Jul 2022 17:36:16 +0800 Subject: block: don't allow the same type rq_qos add more than once In our test of iocost, we encountered some list add/del corruptions of inner_walk list in ioc_timer_fn. The reason can be described as follows: cpu 0 cpu 1 ioc_qos_write ioc_qos_write ioc = q_to_ioc(queue); if (!ioc) { ioc = kzalloc(); ioc = q_to_ioc(queue); if (!ioc) { ioc = kzalloc(); ... rq_qos_add(q, rqos); } ... rq_qos_add(q, rqos); ... } When the io.cost.qos file is written by two cpus concurrently, rq_qos may be added to one disk twice. In that case, there will be two iocs enabled and running on one disk. They own different iocgs on their active list. In the ioc_timer_fn function, because of the iocgs from two iocs have the same root iocg, the root iocg's walk_list may be overwritten by each other and this leads to list add/del corruptions in building or destroying the inner_walk list. And so far, the blk-rq-qos framework works in case that one instance for one type rq_qos per queue by default. This patch make this explicit and also fix the crash above. Signed-off-by: Jinke Han Reviewed-by: Muchun Song Acked-by: Tejun Heo Cc: Link: https://lore.kernel.org/r/20220720093616.70584-1-hanjinke.666@bytedance.com Signed-off-by: Jens Axboe --- block/blk-iolatency.c | 18 +++++++++++------- 1 file changed, 11 insertions(+), 7 deletions(-) (limited to 'block/blk-iolatency.c') diff --git a/block/blk-iolatency.c b/block/blk-iolatency.c index 79745c6d8e15..e285152345a2 100644 --- a/block/blk-iolatency.c +++ b/block/blk-iolatency.c @@ -771,19 +771,23 @@ int blk_iolatency_init(struct request_queue *q) rqos->ops = &blkcg_iolatency_ops; rqos->q = q; - rq_qos_add(q, rqos); - + ret = rq_qos_add(q, rqos); + if (ret) + goto err_free; ret = blkcg_activate_policy(q, &blkcg_policy_iolatency); - if (ret) { - rq_qos_del(q, rqos); - kfree(blkiolat); - return ret; - } + if (ret) + goto err_qos_del; timer_setup(&blkiolat->timer, blkiolatency_timer_fn, 0); INIT_WORK(&blkiolat->enable_work, blkiolatency_enable_work_fn); return 0; + +err_qos_del: + rq_qos_del(q, rqos); +err_free: + kfree(blkiolat); + return ret; } static void iolatency_set_min_lat_nsec(struct blkcg_gq *blkg, u64 val) -- cgit