Currently rq-qos debugfs entries are created from rq_qos_add(), while rq_qos_add() can be called while queue is still frozen. This can deadlock because creating new entries can trigger fs reclaim. Fix this problem by delaying creating rq-qos debugfs entries after queue is unfrozen. - For wbt, 1) it can be initialized by default, fix it by calling new helper after wbt_init() from wbt_enable_default; 2) it can be initialized by sysfs, fix it by calling new helper after queue is unfrozen from queue_wb_lat_store(). - For iocost and iolatency, they can only be initialized by blkcg configuration, however, they don't have debugfs entries for now, hence they are not handled yet. Signed-off-by: Yu Kuai --- block/blk-rq-qos.c | 7 ------- block/blk-wbt.c | 10 +++++++++- 2 files changed, 9 insertions(+), 8 deletions(-) diff --git a/block/blk-rq-qos.c b/block/blk-rq-qos.c index 654478dfbc20..d7ce99ce2e80 100644 --- a/block/blk-rq-qos.c +++ b/block/blk-rq-qos.c @@ -347,13 +347,6 @@ int rq_qos_add(struct rq_qos *rqos, struct gendisk *disk, enum rq_qos_id id, blk_queue_flag_set(QUEUE_FLAG_QOS_ENABLED, q); blk_mq_unfreeze_queue(q, memflags); - - if (rqos->ops->debugfs_attrs) { - mutex_lock(&q->debugfs_mutex); - blk_mq_debugfs_register_rqos(rqos); - mutex_unlock(&q->debugfs_mutex); - } - return 0; ebusy: blk_mq_unfreeze_queue(q, memflags); diff --git a/block/blk-wbt.c b/block/blk-wbt.c index 3777255b99ad..c471d11b756f 100644 --- a/block/blk-wbt.c +++ b/block/blk-wbt.c @@ -758,8 +758,12 @@ void wbt_enable_default(struct gendisk *disk) if (queue_is_mq(q) && enable) { struct rq_wb *rwb = wbt_alloc(); - if (rwb) + if (rwb) { wbt_init(disk, rwb); + mutex_lock(&q->debugfs_mutex); + blk_mq_debugfs_register_rq_qos(q); + mutex_unlock(&q->debugfs_mutex); + } } } EXPORT_SYMBOL_GPL(wbt_enable_default); @@ -999,5 +1003,9 @@ int wbt_set_lat(struct gendisk *disk, s64 val) blk_mq_unquiesce_queue(q); out: blk_mq_unfreeze_queue(q, memflags); + mutex_lock(&q->debugfs_mutex); + blk_mq_debugfs_register_rq_qos(q); + mutex_unlock(&q->debugfs_mutex); + return ret; } -- 2.51.0