From 4e9bbf6653c17823bae3a4b7ce596ba3542ec745 Mon Sep 17 00:00:00 2001 From: Jinke Han Date: Wed, 20 Jul 2022 17:36:16 +0800 Subject: [PATCH] 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-iocost.c | 20 +++++++++++++------- block/blk-iolatency.c | 18 +++++++++++------- block/blk-rq-qos.h | 11 ++++++++++- block/blk-wbt.c | 12 +++++++++++- 4 files changed, 45 insertions(+), 16 deletions(-) diff --git a/block/blk-iocost.c b/block/blk-iocost.c index b7082f2aed9c6..7936e5f5821c7 100644 --- a/block/blk-iocost.c +++ b/block/blk-iocost.c @@ -2886,15 +2886,21 @@ static int blk_iocost_init(struct request_queue *q) * called before policy activation completion, can't assume that the * target bio has an iocg associated and need to test for NULL iocg. */ - rq_qos_add(q, rqos); + ret = rq_qos_add(q, rqos); + if (ret) + goto err_free_ioc; + ret = blkcg_activate_policy(q, &blkcg_policy_iocost); - if (ret) { - rq_qos_del(q, rqos); - free_percpu(ioc->pcpu_stat); - kfree(ioc); - return ret; - } + if (ret) + goto err_del_qos; return 0; + +err_del_qos: + rq_qos_del(q, rqos); +err_free_ioc: + free_percpu(ioc->pcpu_stat); + kfree(ioc); + return ret; } static struct blkcg_policy_data *ioc_cpd_alloc(gfp_t gfp) diff --git a/block/blk-iolatency.c b/block/blk-iolatency.c index 79745c6d8e15f..e285152345a20 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) diff --git a/block/blk-rq-qos.h b/block/blk-rq-qos.h index 0e46052b018a4..08b856570ad10 100644 --- a/block/blk-rq-qos.h +++ b/block/blk-rq-qos.h @@ -86,7 +86,7 @@ static inline void rq_wait_init(struct rq_wait *rq_wait) init_waitqueue_head(&rq_wait->wait); } -static inline void rq_qos_add(struct request_queue *q, struct rq_qos *rqos) +static inline int rq_qos_add(struct request_queue *q, struct rq_qos *rqos) { /* * No IO can be in-flight when adding rqos, so freeze queue, which @@ -98,6 +98,8 @@ static inline void rq_qos_add(struct request_queue *q, struct rq_qos *rqos) blk_mq_freeze_queue(q); spin_lock_irq(&q->queue_lock); + if (rq_qos_id(q, rqos->id)) + goto ebusy; rqos->next = q->rq_qos; q->rq_qos = rqos; spin_unlock_irq(&q->queue_lock); @@ -109,6 +111,13 @@ static inline void rq_qos_add(struct request_queue *q, struct rq_qos *rqos) blk_mq_debugfs_register_rqos(rqos); mutex_unlock(&q->debugfs_mutex); } + + return 0; +ebusy: + spin_unlock_irq(&q->queue_lock); + blk_mq_unfreeze_queue(q); + return -EBUSY; + } static inline void rq_qos_del(struct request_queue *q, struct rq_qos *rqos) diff --git a/block/blk-wbt.c b/block/blk-wbt.c index f2e4bf1dca47a..a9982000b667e 100644 --- a/block/blk-wbt.c +++ b/block/blk-wbt.c @@ -820,6 +820,7 @@ int wbt_init(struct request_queue *q) { struct rq_wb *rwb; int i; + int ret; rwb = kzalloc(sizeof(*rwb), GFP_KERNEL); if (!rwb) @@ -846,7 +847,10 @@ int wbt_init(struct request_queue *q) /* * Assign rwb and add the stats callback. */ - rq_qos_add(q, &rwb->rqos); + ret = rq_qos_add(q, &rwb->rqos); + if (ret) + goto err_free; + blk_stat_add_callback(q, rwb->cb); rwb->min_lat_nsec = wbt_default_latency_nsec(q); @@ -855,4 +859,10 @@ int wbt_init(struct request_queue *q) wbt_set_write_cache(q, test_bit(QUEUE_FLAG_WC, &q->queue_flags)); return 0; + +err_free: + blk_stat_free_callback(rwb->cb); + kfree(rwb); + return ret; + } -- 2.39.5