4.12-stable review patch. If anyone has any objections, please let me know.
------------------ From: Christoph Hellwig <h...@lst.de> commit 4b855ad37194f7bdbb200ce7a1c7051fecb56a08 upstream. Currently we only create hctx for online CPUs, which can lead to a lot of churn due to frequent soft offline / online operations. Instead allocate one for each present CPU to avoid this and dramatically simplify the code. Signed-off-by: Christoph Hellwig <h...@lst.de> Reviewed-by: Jens Axboe <ax...@kernel.dk> Cc: Keith Busch <keith.bu...@intel.com> Cc: linux-bl...@vger.kernel.org Cc: linux-n...@lists.infradead.org Link: http://lkml.kernel.org/r/20170626102058.10200-3-...@lst.de Signed-off-by: Thomas Gleixner <t...@linutronix.de> Cc: Oleksandr Natalenko <oleksa...@natalenko.name> Cc: Mike Galbraith <efa...@gmx.de> Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org> --- block/blk-mq.c | 120 ++++----------------------------------------- block/blk-mq.h | 5 - include/linux/cpuhotplug.h | 1 3 files changed, 11 insertions(+), 115 deletions(-) --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -37,9 +37,6 @@ #include "blk-wbt.h" #include "blk-mq-sched.h" -static DEFINE_MUTEX(all_q_mutex); -static LIST_HEAD(all_q_list); - static void blk_mq_poll_stats_start(struct request_queue *q); static void blk_mq_poll_stats_fn(struct blk_stat_callback *cb); static void __blk_mq_stop_hw_queues(struct request_queue *q, bool sync); @@ -1975,8 +1972,8 @@ static void blk_mq_init_cpu_queues(struc INIT_LIST_HEAD(&__ctx->rq_list); __ctx->queue = q; - /* If the cpu isn't online, the cpu is mapped to first hctx */ - if (!cpu_online(i)) + /* If the cpu isn't present, the cpu is mapped to first hctx */ + if (!cpu_present(i)) continue; hctx = blk_mq_map_queue(q, i); @@ -2019,8 +2016,7 @@ static void blk_mq_free_map_and_requests } } -static void blk_mq_map_swqueue(struct request_queue *q, - const struct cpumask *online_mask) +static void blk_mq_map_swqueue(struct request_queue *q) { unsigned int i, hctx_idx; struct blk_mq_hw_ctx *hctx; @@ -2038,13 +2034,11 @@ static void blk_mq_map_swqueue(struct re } /* - * Map software to hardware queues + * Map software to hardware queues. + * + * If the cpu isn't present, the cpu is mapped to first hctx. */ - for_each_possible_cpu(i) { - /* If the cpu isn't online, the cpu is mapped to first hctx */ - if (!cpumask_test_cpu(i, online_mask)) - continue; - + for_each_present_cpu(i) { hctx_idx = q->mq_map[i]; /* unmapped hw queue can be remapped after CPU topo changed */ if (!set->tags[hctx_idx] && @@ -2340,16 +2334,8 @@ struct request_queue *blk_mq_init_alloca blk_queue_softirq_done(q, set->ops->complete); blk_mq_init_cpu_queues(q, set->nr_hw_queues); - - get_online_cpus(); - mutex_lock(&all_q_mutex); - - list_add_tail(&q->all_q_node, &all_q_list); blk_mq_add_queue_tag_set(set, q); - blk_mq_map_swqueue(q, cpu_online_mask); - - mutex_unlock(&all_q_mutex); - put_online_cpus(); + blk_mq_map_swqueue(q); if (!(set->flags & BLK_MQ_F_NO_SCHED)) { int ret; @@ -2375,18 +2361,12 @@ void blk_mq_free_queue(struct request_qu { struct blk_mq_tag_set *set = q->tag_set; - mutex_lock(&all_q_mutex); - list_del_init(&q->all_q_node); - mutex_unlock(&all_q_mutex); - blk_mq_del_queue_tag_set(q); - blk_mq_exit_hw_queues(q, set, set->nr_hw_queues); } /* Basically redo blk_mq_init_queue with queue frozen */ -static void blk_mq_queue_reinit(struct request_queue *q, - const struct cpumask *online_mask) +static void blk_mq_queue_reinit(struct request_queue *q) { WARN_ON_ONCE(!atomic_read(&q->mq_freeze_depth)); @@ -2399,76 +2379,12 @@ static void blk_mq_queue_reinit(struct r * involves free and re-allocate memory, worthy doing?) */ - blk_mq_map_swqueue(q, online_mask); + blk_mq_map_swqueue(q); blk_mq_sysfs_register(q); blk_mq_debugfs_register_hctxs(q); } -/* - * New online cpumask which is going to be set in this hotplug event. - * Declare this cpumasks as global as cpu-hotplug operation is invoked - * one-by-one and dynamically allocating this could result in a failure. - */ -static struct cpumask cpuhp_online_new; - -static void blk_mq_queue_reinit_work(void) -{ - struct request_queue *q; - - mutex_lock(&all_q_mutex); - /* - * We need to freeze and reinit all existing queues. Freezing - * involves synchronous wait for an RCU grace period and doing it - * one by one may take a long time. Start freezing all queues in - * one swoop and then wait for the completions so that freezing can - * take place in parallel. - */ - list_for_each_entry(q, &all_q_list, all_q_node) - blk_freeze_queue_start(q); - list_for_each_entry(q, &all_q_list, all_q_node) - blk_mq_freeze_queue_wait(q); - - list_for_each_entry(q, &all_q_list, all_q_node) - blk_mq_queue_reinit(q, &cpuhp_online_new); - - list_for_each_entry(q, &all_q_list, all_q_node) - blk_mq_unfreeze_queue(q); - - mutex_unlock(&all_q_mutex); -} - -static int blk_mq_queue_reinit_dead(unsigned int cpu) -{ - cpumask_copy(&cpuhp_online_new, cpu_online_mask); - blk_mq_queue_reinit_work(); - return 0; -} - -/* - * Before hotadded cpu starts handling requests, new mappings must be - * established. Otherwise, these requests in hw queue might never be - * dispatched. - * - * For example, there is a single hw queue (hctx) and two CPU queues (ctx0 - * for CPU0, and ctx1 for CPU1). - * - * Now CPU1 is just onlined and a request is inserted into ctx1->rq_list - * and set bit0 in pending bitmap as ctx1->index_hw is still zero. - * - * And then while running hw queue, blk_mq_flush_busy_ctxs() finds bit0 is set - * in pending bitmap and tries to retrieve requests in hctx->ctxs[0]->rq_list. - * But htx->ctxs[0] is a pointer to ctx0, so the request in ctx1->rq_list is - * ignored. - */ -static int blk_mq_queue_reinit_prepare(unsigned int cpu) -{ - cpumask_copy(&cpuhp_online_new, cpu_online_mask); - cpumask_set_cpu(cpu, &cpuhp_online_new); - blk_mq_queue_reinit_work(); - return 0; -} - static int __blk_mq_alloc_rq_maps(struct blk_mq_tag_set *set) { int i; @@ -2679,7 +2595,7 @@ static void __blk_mq_update_nr_hw_queues blk_mq_update_queue_map(set); list_for_each_entry(q, &set->tag_list, tag_set_list) { blk_mq_realloc_hw_ctxs(set, q); - blk_mq_queue_reinit(q, cpu_online_mask); + blk_mq_queue_reinit(q); } list_for_each_entry(q, &set->tag_list, tag_set_list) @@ -2895,24 +2811,10 @@ bool blk_mq_poll(struct request_queue *q } EXPORT_SYMBOL_GPL(blk_mq_poll); -void blk_mq_disable_hotplug(void) -{ - mutex_lock(&all_q_mutex); -} - -void blk_mq_enable_hotplug(void) -{ - mutex_unlock(&all_q_mutex); -} - static int __init blk_mq_init(void) { cpuhp_setup_state_multi(CPUHP_BLK_MQ_DEAD, "block/mq:dead", NULL, blk_mq_hctx_notify_dead); - - cpuhp_setup_state_nocalls(CPUHP_BLK_MQ_PREPARE, "block/mq:prepare", - blk_mq_queue_reinit_prepare, - blk_mq_queue_reinit_dead); return 0; } subsys_initcall(blk_mq_init); --- a/block/blk-mq.h +++ b/block/blk-mq.h @@ -56,11 +56,6 @@ void __blk_mq_insert_request(struct blk_ bool at_head); void blk_mq_insert_requests(struct blk_mq_hw_ctx *hctx, struct blk_mq_ctx *ctx, struct list_head *list); -/* - * CPU hotplug helpers - */ -void blk_mq_enable_hotplug(void); -void blk_mq_disable_hotplug(void); /* * CPU -> queue mappings --- a/include/linux/cpuhotplug.h +++ b/include/linux/cpuhotplug.h @@ -58,7 +58,6 @@ enum cpuhp_state { CPUHP_XEN_EVTCHN_PREPARE, CPUHP_ARM_SHMOBILE_SCU_PREPARE, CPUHP_SH_SH3X_PREPARE, - CPUHP_BLK_MQ_PREPARE, CPUHP_NET_FLOW_PREPARE, CPUHP_TOPOLOGY_PREPARE, CPUHP_NET_IUCV_PREPARE,
