TOMOYO Linux Cross Reference
Linux/block/blk-mq.c

   // SPDX-License-Identifier: GPL-2.0
   /*
    * Block multiqueue core code
    *
    * Copyright (C) 2013-2014 Jens Axboe
    * Copyright (C) 2013-2014 Christoph Hellwig
    */
   #include <linux/kernel.h>
   #include <linux/module.h>
  #include <linux/backing-dev.h>
  #include <linux/bio.h>
  #include <linux/blkdev.h>
  #include <linux/kmemleak.h>
  #include <linux/mm.h>
  #include <linux/init.h>
  #include <linux/slab.h>
  #include <linux/workqueue.h>
  #include <linux/smp.h>
  #include <linux/llist.h>
  #include <linux/list_sort.h>
  #include <linux/cpu.h>
  #include <linux/cache.h>
  #include <linux/sched/sysctl.h>
  #include <linux/sched/topology.h>
  #include <linux/sched/signal.h>
  #include <linux/delay.h>
  #include <linux/crash_dump.h>
  #include <linux/prefetch.h>
  
  #include <trace/events/block.h>
  
  #include <linux/blk-mq.h>
  #include <linux/t10-pi.h>
  #include "blk.h"
  #include "blk-mq.h"
  #include "blk-mq-debugfs.h"
  #include "blk-mq-tag.h"
  #include "blk-pm.h"
  #include "blk-stat.h"
  #include "blk-mq-sched.h"
  #include "blk-rq-qos.h"
  
  static void blk_mq_poll_stats_start(struct request_queue *q);
  static void blk_mq_poll_stats_fn(struct blk_stat_callback *cb);
  
  static int blk_mq_poll_stats_bkt(const struct request *rq)
  {
          int ddir, sectors, bucket;
  
          ddir = rq_data_dir(rq);
          sectors = blk_rq_stats_sectors(rq);
  
          bucket = ddir + 2 * ilog2(sectors);
  
          if (bucket < 0)
                  return -1;
          else if (bucket >= BLK_MQ_POLL_STATS_BKTS)
                  return ddir + BLK_MQ_POLL_STATS_BKTS - 2;
  
          return bucket;
  }
  
  /*
   * Check if any of the ctx, dispatch list or elevator
   * have pending work in this hardware queue.
   */
  static bool blk_mq_hctx_has_pending(struct blk_mq_hw_ctx *hctx)
  {
          return !list_empty_careful(&hctx->dispatch) ||
                  sbitmap_any_bit_set(&hctx->ctx_map) ||
                          blk_mq_sched_has_work(hctx);
  }
  
  /*
   * Mark this ctx as having pending work in this hardware queue
   */
  static void blk_mq_hctx_mark_pending(struct blk_mq_hw_ctx *hctx,
                                       struct blk_mq_ctx *ctx)
  {
          const int bit = ctx->index_hw[hctx->type];
  
          if (!sbitmap_test_bit(&hctx->ctx_map, bit))
                  sbitmap_set_bit(&hctx->ctx_map, bit);
  }
  
  static void blk_mq_hctx_clear_pending(struct blk_mq_hw_ctx *hctx,
                                        struct blk_mq_ctx *ctx)
  {
          const int bit = ctx->index_hw[hctx->type];
  
          sbitmap_clear_bit(&hctx->ctx_map, bit);
  }
  
  struct mq_inflight {
          struct hd_struct *part;
          unsigned int inflight[2];
  };
  
  static bool blk_mq_check_inflight(struct blk_mq_hw_ctx *hctx,
                                   struct request *rq, void *priv,
                                   bool reserved)
 {
         struct mq_inflight *mi = priv;
 
         if (rq->part == mi->part)
                 mi->inflight[rq_data_dir(rq)]++;
 
         return true;
 }
 
 unsigned int blk_mq_in_flight(struct request_queue *q, struct hd_struct *part)
 {
         struct mq_inflight mi = { .part = part };
 
         blk_mq_queue_tag_busy_iter(q, blk_mq_check_inflight, &mi);
 
         return mi.inflight[0] + mi.inflight[1];
 }
 
 void blk_mq_in_flight_rw(struct request_queue *q, struct hd_struct *part,
                          unsigned int inflight[2])
 {
         struct mq_inflight mi = { .part = part };
 
         blk_mq_queue_tag_busy_iter(q, blk_mq_check_inflight, &mi);
         inflight[0] = mi.inflight[0];
         inflight[1] = mi.inflight[1];
 }
 
 void blk_freeze_queue_start(struct request_queue *q)
 {
         mutex_lock(&q->mq_freeze_lock);
         if (++q->mq_freeze_depth == 1) {
                 percpu_ref_kill(&q->q_usage_counter);
                 mutex_unlock(&q->mq_freeze_lock);
                 if (queue_is_mq(q))
                         blk_mq_run_hw_queues(q, false);
         } else {
                 mutex_unlock(&q->mq_freeze_lock);
         }
 }
 EXPORT_SYMBOL_GPL(blk_freeze_queue_start);
 
 void blk_mq_freeze_queue_wait(struct request_queue *q)
 {
         wait_event(q->mq_freeze_wq, percpu_ref_is_zero(&q->q_usage_counter));
 }
 EXPORT_SYMBOL_GPL(blk_mq_freeze_queue_wait);
 
 int blk_mq_freeze_queue_wait_timeout(struct request_queue *q,
                                      unsigned long timeout)
 {
         return wait_event_timeout(q->mq_freeze_wq,
                                         percpu_ref_is_zero(&q->q_usage_counter),
                                         timeout);
 }
 EXPORT_SYMBOL_GPL(blk_mq_freeze_queue_wait_timeout);
 
 /*
  * Guarantee no request is in use, so we can change any data structure of
  * the queue afterward.
  */
 void blk_freeze_queue(struct request_queue *q)
 {
         /*
          * In the !blk_mq case we are only calling this to kill the
          * q_usage_counter, otherwise this increases the freeze depth
          * and waits for it to return to zero.  For this reason there is
          * no blk_unfreeze_queue(), and blk_freeze_queue() is not
          * exported to drivers as the only user for unfreeze is blk_mq.
          */
         blk_freeze_queue_start(q);
         blk_mq_freeze_queue_wait(q);
 }
 
 void blk_mq_freeze_queue(struct request_queue *q)
 {
         /*
          * ...just an alias to keep freeze and unfreeze actions balanced
          * in the blk_mq_* namespace
          */
         blk_freeze_queue(q);
 }
 EXPORT_SYMBOL_GPL(blk_mq_freeze_queue);
 
 void blk_mq_unfreeze_queue(struct request_queue *q)
 {
         mutex_lock(&q->mq_freeze_lock);
         q->mq_freeze_depth--;
         WARN_ON_ONCE(q->mq_freeze_depth < 0);
         if (!q->mq_freeze_depth) {
                 percpu_ref_resurrect(&q->q_usage_counter);
                 wake_up_all(&q->mq_freeze_wq);
         }
         mutex_unlock(&q->mq_freeze_lock);
 }
 EXPORT_SYMBOL_GPL(blk_mq_unfreeze_queue);
 
 /*
  * FIXME: replace the scsi_internal_device_*block_nowait() calls in the
  * mpt3sas driver such that this function can be removed.
  */
 void blk_mq_quiesce_queue_nowait(struct request_queue *q)
 {
         blk_queue_flag_set(QUEUE_FLAG_QUIESCED, q);
 }
 EXPORT_SYMBOL_GPL(blk_mq_quiesce_queue_nowait);
 
 /**
  * blk_mq_quiesce_queue() - wait until all ongoing dispatches have finished
  * @q: request queue.
  *
  * Note: this function does not prevent that the struct request end_io()
  * callback function is invoked. Once this function is returned, we make
  * sure no dispatch can happen until the queue is unquiesced via
  * blk_mq_unquiesce_queue().
  */
 void blk_mq_quiesce_queue(struct request_queue *q)
 {
         struct blk_mq_hw_ctx *hctx;
         unsigned int i;
         bool rcu = false;
 
         blk_mq_quiesce_queue_nowait(q);
 
         queue_for_each_hw_ctx(q, hctx, i) {
                 if (hctx->flags & BLK_MQ_F_BLOCKING)
                         synchronize_srcu(hctx->srcu);
                 else
                         rcu = true;
         }
         if (rcu)
                 synchronize_rcu();
 }
 EXPORT_SYMBOL_GPL(blk_mq_quiesce_queue);
 
 /*
  * blk_mq_unquiesce_queue() - counterpart of blk_mq_quiesce_queue()
  * @q: request queue.
  *
  * This function recovers queue into the state before quiescing
  * which is done by blk_mq_quiesce_queue.
  */
 void blk_mq_unquiesce_queue(struct request_queue *q)
 {
         blk_queue_flag_clear(QUEUE_FLAG_QUIESCED, q);
 
         /* dispatch requests which are inserted during quiescing */
         blk_mq_run_hw_queues(q, true);
 }
 EXPORT_SYMBOL_GPL(blk_mq_unquiesce_queue);
 
 void blk_mq_wake_waiters(struct request_queue *q)
 {
         struct blk_mq_hw_ctx *hctx;
         unsigned int i;
 
         queue_for_each_hw_ctx(q, hctx, i)
                 if (blk_mq_hw_queue_mapped(hctx))
                         blk_mq_tag_wakeup_all(hctx->tags, true);
 }
 
 /*
  * Only need start/end time stamping if we have iostat or
  * blk stats enabled, or using an IO scheduler.
  */
 static inline bool blk_mq_need_time_stamp(struct request *rq)
 {
         return (rq->rq_flags & (RQF_IO_STAT | RQF_STATS)) || rq->q->elevator;
 }
 
 static struct request *blk_mq_rq_ctx_init(struct blk_mq_alloc_data *data,
                 unsigned int tag, unsigned int op, u64 alloc_time_ns)
 {
         struct blk_mq_tags *tags = blk_mq_tags_from_data(data);
         struct request *rq = tags->static_rqs[tag];
         req_flags_t rq_flags = 0;
 
         if (data->flags & BLK_MQ_REQ_INTERNAL) {
                 rq->tag = -1;
                 rq->internal_tag = tag;
         } else {
                 if (data->hctx->flags & BLK_MQ_F_TAG_SHARED) {
                         rq_flags = RQF_MQ_INFLIGHT;
                         atomic_inc(&data->hctx->nr_active);
                 }
                 rq->tag = tag;
                 rq->internal_tag = -1;
                 data->hctx->tags->rqs[rq->tag] = rq;
         }
 
         /* csd/requeue_work/fifo_time is initialized before use */
         rq->q = data->q;
         rq->mq_ctx = data->ctx;
         rq->mq_hctx = data->hctx;
         rq->rq_flags = rq_flags;
         rq->cmd_flags = op;
         if (data->flags & BLK_MQ_REQ_PREEMPT)
                 rq->rq_flags |= RQF_PREEMPT;
         if (blk_queue_io_stat(data->q))
                 rq->rq_flags |= RQF_IO_STAT;
         INIT_LIST_HEAD(&rq->queuelist);
         INIT_HLIST_NODE(&rq->hash);
         RB_CLEAR_NODE(&rq->rb_node);
         rq->rq_disk = NULL;
         rq->part = NULL;
 #ifdef CONFIG_BLK_RQ_ALLOC_TIME
         rq->alloc_time_ns = alloc_time_ns;
 #endif
         if (blk_mq_need_time_stamp(rq))
                 rq->start_time_ns = ktime_get_ns();
         else
                 rq->start_time_ns = 0;
         rq->io_start_time_ns = 0;
         rq->stats_sectors = 0;
         rq->nr_phys_segments = 0;
 #if defined(CONFIG_BLK_DEV_INTEGRITY)
         rq->nr_integrity_segments = 0;
 #endif
         /* tag was already set */
         rq->extra_len = 0;
         WRITE_ONCE(rq->deadline, 0);
 
         rq->timeout = 0;
 
         rq->end_io = NULL;
         rq->end_io_data = NULL;
 
         data->ctx->rq_dispatched[op_is_sync(op)]++;
         refcount_set(&rq->ref, 1);
         return rq;
 }
 
 static struct request *blk_mq_get_request(struct request_queue *q,
                                           struct bio *bio,
                                           struct blk_mq_alloc_data *data)
 {
         struct elevator_queue *e = q->elevator;
         struct request *rq;
         unsigned int tag;
         bool clear_ctx_on_error = false;
         u64 alloc_time_ns = 0;
 
         blk_queue_enter_live(q);
 
         /* alloc_time includes depth and tag waits */
         if (blk_queue_rq_alloc_time(q))
                 alloc_time_ns = ktime_get_ns();
 
         data->q = q;
         if (likely(!data->ctx)) {
                 data->ctx = blk_mq_get_ctx(q);
                 clear_ctx_on_error = true;
         }
         if (likely(!data->hctx))
                 data->hctx = blk_mq_map_queue(q, data->cmd_flags,
                                                 data->ctx);
         if (data->cmd_flags & REQ_NOWAIT)
                 data->flags |= BLK_MQ_REQ_NOWAIT;
 
         if (e) {
                 data->flags |= BLK_MQ_REQ_INTERNAL;
 
                 /*
                  * Flush requests are special and go directly to the
                  * dispatch list. Don't include reserved tags in the
                  * limiting, as it isn't useful.
                  */
                 if (!op_is_flush(data->cmd_flags) &&
                     e->type->ops.limit_depth &&
                     !(data->flags & BLK_MQ_REQ_RESERVED))
                         e->type->ops.limit_depth(data->cmd_flags, data);
         } else {
                 blk_mq_tag_busy(data->hctx);
         }
 
         tag = blk_mq_get_tag(data);
         if (tag == BLK_MQ_TAG_FAIL) {
                 if (clear_ctx_on_error)
                         data->ctx = NULL;
                 blk_queue_exit(q);
                 return NULL;
         }
 
         rq = blk_mq_rq_ctx_init(data, tag, data->cmd_flags, alloc_time_ns);
         if (!op_is_flush(data->cmd_flags)) {
                 rq->elv.icq = NULL;
                 if (e && e->type->ops.prepare_request) {
                         if (e->type->icq_cache)
                                 blk_mq_sched_assign_ioc(rq);
 
                         e->type->ops.prepare_request(rq, bio);
                         rq->rq_flags |= RQF_ELVPRIV;
                 }
         }
         data->hctx->queued++;
         return rq;
 }
 
 struct request *blk_mq_alloc_request(struct request_queue *q, unsigned int op,
                 blk_mq_req_flags_t flags)
 {
         struct blk_mq_alloc_data alloc_data = { .flags = flags, .cmd_flags = op };
         struct request *rq;
         int ret;
 
         ret = blk_queue_enter(q, flags);
         if (ret)
                 return ERR_PTR(ret);
 
         rq = blk_mq_get_request(q, NULL, &alloc_data);
         blk_queue_exit(q);
 
         if (!rq)
                 return ERR_PTR(-EWOULDBLOCK);
 
         rq->__data_len = 0;
         rq->__sector = (sector_t) -1;
         rq->bio = rq->biotail = NULL;
         return rq;
 }
 EXPORT_SYMBOL(blk_mq_alloc_request);
 
 struct request *blk_mq_alloc_request_hctx(struct request_queue *q,
         unsigned int op, blk_mq_req_flags_t flags, unsigned int hctx_idx)
 {
         struct blk_mq_alloc_data alloc_data = { .flags = flags, .cmd_flags = op };
         struct request *rq;
         unsigned int cpu;
         int ret;
 
         /*
          * If the tag allocator sleeps we could get an allocation for a
          * different hardware context.  No need to complicate the low level
          * allocator for this for the rare use case of a command tied to
          * a specific queue.
          */
         if (WARN_ON_ONCE(!(flags & BLK_MQ_REQ_NOWAIT)))
                 return ERR_PTR(-EINVAL);
 
         if (hctx_idx >= q->nr_hw_queues)
                 return ERR_PTR(-EIO);
 
         ret = blk_queue_enter(q, flags);
         if (ret)
                 return ERR_PTR(ret);
 
         /*
          * Check if the hardware context is actually mapped to anything.
          * If not tell the caller that it should skip this queue.
          */
         alloc_data.hctx = q->queue_hw_ctx[hctx_idx];
         if (!blk_mq_hw_queue_mapped(alloc_data.hctx)) {
                 blk_queue_exit(q);
                 return ERR_PTR(-EXDEV);
         }
         cpu = cpumask_first_and(alloc_data.hctx->cpumask, cpu_online_mask);
         alloc_data.ctx = __blk_mq_get_ctx(q, cpu);
 
         rq = blk_mq_get_request(q, NULL, &alloc_data);
         blk_queue_exit(q);
 
         if (!rq)
                 return ERR_PTR(-EWOULDBLOCK);
 
         return rq;
 }
 EXPORT_SYMBOL_GPL(blk_mq_alloc_request_hctx);
 
 static void __blk_mq_free_request(struct request *rq)
 {
         struct request_queue *q = rq->q;
         struct blk_mq_ctx *ctx = rq->mq_ctx;
         struct blk_mq_hw_ctx *hctx = rq->mq_hctx;
         const int sched_tag = rq->internal_tag;
 
         blk_pm_mark_last_busy(rq);
         rq->mq_hctx = NULL;
         if (rq->tag != -1)
                 blk_mq_put_tag(hctx, hctx->tags, ctx, rq->tag);
         if (sched_tag != -1)
                 blk_mq_put_tag(hctx, hctx->sched_tags, ctx, sched_tag);
         blk_mq_sched_restart(hctx);
         blk_queue_exit(q);
 }
 
 void blk_mq_free_request(struct request *rq)
 {
         struct request_queue *q = rq->q;
         struct elevator_queue *e = q->elevator;
         struct blk_mq_ctx *ctx = rq->mq_ctx;
         struct blk_mq_hw_ctx *hctx = rq->mq_hctx;
 
         if (rq->rq_flags & RQF_ELVPRIV) {
                 if (e && e->type->ops.finish_request)
                         e->type->ops.finish_request(rq);
                 if (rq->elv.icq) {
                         put_io_context(rq->elv.icq->ioc);
                         rq->elv.icq = NULL;
                 }
         }
 
         ctx->rq_completed[rq_is_sync(rq)]++;
         if (rq->rq_flags & RQF_MQ_INFLIGHT)
                 atomic_dec(&hctx->nr_active);
 
         if (unlikely(laptop_mode && !blk_rq_is_passthrough(rq)))
                 laptop_io_completion(q->backing_dev_info);
 
         rq_qos_done(q, rq);
 
         WRITE_ONCE(rq->state, MQ_RQ_IDLE);
         if (refcount_dec_and_test(&rq->ref))
                 __blk_mq_free_request(rq);
 }
 EXPORT_SYMBOL_GPL(blk_mq_free_request);
 
 inline void __blk_mq_end_request(struct request *rq, blk_status_t error)
 {
         u64 now = 0;
 
         if (blk_mq_need_time_stamp(rq))
                 now = ktime_get_ns();
 
         if (rq->rq_flags & RQF_STATS) {
                 blk_mq_poll_stats_start(rq->q);
                 blk_stat_add(rq, now);
         }
 
         if (rq->internal_tag != -1)
                 blk_mq_sched_completed_request(rq, now);
 
         blk_account_io_done(rq, now);
 
         if (rq->end_io) {
                 rq_qos_done(rq->q, rq);
                 rq->end_io(rq, error);
         } else {
                 blk_mq_free_request(rq);
         }
 }
 EXPORT_SYMBOL(__blk_mq_end_request);
 
 void blk_mq_end_request(struct request *rq, blk_status_t error)
 {
         if (blk_update_request(rq, error, blk_rq_bytes(rq)))
                 BUG();
         __blk_mq_end_request(rq, error);
 }
 EXPORT_SYMBOL(blk_mq_end_request);
 
 static void __blk_mq_complete_request_remote(void *data)
 {
         struct request *rq = data;
         struct request_queue *q = rq->q;
 
         q->mq_ops->complete(rq);
 }
 
 static void __blk_mq_complete_request(struct request *rq)
 {
         struct blk_mq_ctx *ctx = rq->mq_ctx;
         struct request_queue *q = rq->q;
         bool shared = false;
         int cpu;
 
         WRITE_ONCE(rq->state, MQ_RQ_COMPLETE);
         /*
          * Most of single queue controllers, there is only one irq vector
          * for handling IO completion, and the only irq's affinity is set
          * as all possible CPUs. On most of ARCHs, this affinity means the
          * irq is handled on one specific CPU.
          *
          * So complete IO reqeust in softirq context in case of single queue
          * for not degrading IO performance by irqsoff latency.
          */
         if (q->nr_hw_queues == 1) {
                 __blk_complete_request(rq);
                 return;
         }
 
         /*
          * For a polled request, always complete locallly, it's pointless
          * to redirect the completion.
          */
         if ((rq->cmd_flags & REQ_HIPRI) ||
             !test_bit(QUEUE_FLAG_SAME_COMP, &q->queue_flags)) {
                 q->mq_ops->complete(rq);
                 return;
         }
 
         cpu = get_cpu();
         if (!test_bit(QUEUE_FLAG_SAME_FORCE, &q->queue_flags))
                 shared = cpus_share_cache(cpu, ctx->cpu);
 
         if (cpu != ctx->cpu && !shared && cpu_online(ctx->cpu)) {
                 rq->csd.func = __blk_mq_complete_request_remote;
                 rq->csd.info = rq;
                 rq->csd.flags = 0;
                 smp_call_function_single_async(ctx->cpu, &rq->csd);
         } else {
                 q->mq_ops->complete(rq);
         }
         put_cpu();
 }
 
 static void hctx_unlock(struct blk_mq_hw_ctx *hctx, int srcu_idx)
         __releases(hctx->srcu)
 {
         if (!(hctx->flags & BLK_MQ_F_BLOCKING))
                 rcu_read_unlock();
         else
                 srcu_read_unlock(hctx->srcu, srcu_idx);
 }
 
 static void hctx_lock(struct blk_mq_hw_ctx *hctx, int *srcu_idx)
         __acquires(hctx->srcu)
 {
         if (!(hctx->flags & BLK_MQ_F_BLOCKING)) {
                 /* shut up gcc false positive */
                 *srcu_idx = 0;
                 rcu_read_lock();
         } else
                 *srcu_idx = srcu_read_lock(hctx->srcu);
 }
 
 /**
  * blk_mq_complete_request - end I/O on a request
  * @rq:         the request being processed
  *
  * Description:
  *      Ends all I/O on a request. It does not handle partial completions.
  *      The actual completion happens out-of-order, through a IPI handler.
  **/
 bool blk_mq_complete_request(struct request *rq)
 {
         if (unlikely(blk_should_fake_timeout(rq->q)))
                 return false;
         __blk_mq_complete_request(rq);
         return true;
 }
 EXPORT_SYMBOL(blk_mq_complete_request);
 
 void blk_mq_start_request(struct request *rq)
 {
         struct request_queue *q = rq->q;
 
         trace_block_rq_issue(q, rq);
 
         if (test_bit(QUEUE_FLAG_STATS, &q->queue_flags)) {
                 rq->io_start_time_ns = ktime_get_ns();
                 rq->stats_sectors = blk_rq_sectors(rq);
                 rq->rq_flags |= RQF_STATS;
                 rq_qos_issue(q, rq);
         }
 
         WARN_ON_ONCE(blk_mq_rq_state(rq) != MQ_RQ_IDLE);
 
         blk_add_timer(rq);
         WRITE_ONCE(rq->state, MQ_RQ_IN_FLIGHT);
 
         if (q->dma_drain_size && blk_rq_bytes(rq)) {
                 /*
                  * Make sure space for the drain appears.  We know we can do
                  * this because max_hw_segments has been adjusted to be one
                  * fewer than the device can handle.
                  */
                 rq->nr_phys_segments++;
         }
 
 #ifdef CONFIG_BLK_DEV_INTEGRITY
         if (blk_integrity_rq(rq) && req_op(rq) == REQ_OP_WRITE)
                 q->integrity.profile->prepare_fn(rq);
 #endif
 }
 EXPORT_SYMBOL(blk_mq_start_request);
 
 static void __blk_mq_requeue_request(struct request *rq)
 {
         struct request_queue *q = rq->q;
 
         blk_mq_put_driver_tag(rq);
 
         trace_block_rq_requeue(q, rq);
         rq_qos_requeue(q, rq);
 
         if (blk_mq_request_started(rq)) {
                 WRITE_ONCE(rq->state, MQ_RQ_IDLE);
                 rq->rq_flags &= ~RQF_TIMED_OUT;
                 if (q->dma_drain_size && blk_rq_bytes(rq))
                         rq->nr_phys_segments--;
         }
 }
 
 void blk_mq_requeue_request(struct request *rq, bool kick_requeue_list)
 {
         __blk_mq_requeue_request(rq);
 
         /* this request will be re-inserted to io scheduler queue */
         blk_mq_sched_requeue_request(rq);
 
         BUG_ON(!list_empty(&rq->queuelist));
         blk_mq_add_to_requeue_list(rq, true, kick_requeue_list);
 }
 EXPORT_SYMBOL(blk_mq_requeue_request);
 
 static void blk_mq_requeue_work(struct work_struct *work)
 {
         struct request_queue *q =
                 container_of(work, struct request_queue, requeue_work.work);
         LIST_HEAD(rq_list);
         struct request *rq, *next;
 
         spin_lock_irq(&q->requeue_lock);
         list_splice_init(&q->requeue_list, &rq_list);
         spin_unlock_irq(&q->requeue_lock);
 
         list_for_each_entry_safe(rq, next, &rq_list, queuelist) {
                 if (!(rq->rq_flags & (RQF_SOFTBARRIER | RQF_DONTPREP)))
                         continue;
 
                 rq->rq_flags &= ~RQF_SOFTBARRIER;
                 list_del_init(&rq->queuelist);
                 /*
                  * If RQF_DONTPREP, rq has contained some driver specific
                  * data, so insert it to hctx dispatch list to avoid any
                  * merge.
                  */
                 if (rq->rq_flags & RQF_DONTPREP)
                         blk_mq_request_bypass_insert(rq, false, false);
                 else
                         blk_mq_sched_insert_request(rq, true, false, false);
         }
 
         while (!list_empty(&rq_list)) {
                 rq = list_entry(rq_list.next, struct request, queuelist);
                 list_del_init(&rq->queuelist);
                 blk_mq_sched_insert_request(rq, false, false, false);
         }
 
         blk_mq_run_hw_queues(q, false);
 }
 
 void blk_mq_add_to_requeue_list(struct request *rq, bool at_head,
                                 bool kick_requeue_list)
 {
         struct request_queue *q = rq->q;
         unsigned long flags;
 
         /*
          * We abuse this flag that is otherwise used by the I/O scheduler to
          * request head insertion from the workqueue.
          */
         BUG_ON(rq->rq_flags & RQF_SOFTBARRIER);
 
         spin_lock_irqsave(&q->requeue_lock, flags);
         if (at_head) {
                 rq->rq_flags |= RQF_SOFTBARRIER;
                 list_add(&rq->queuelist, &q->requeue_list);
         } else {
                 list_add_tail(&rq->queuelist, &q->requeue_list);
         }
         spin_unlock_irqrestore(&q->requeue_lock, flags);
 
         if (kick_requeue_list)
                 blk_mq_kick_requeue_list(q);
 }
 
 void blk_mq_kick_requeue_list(struct request_queue *q)
 {
         kblockd_mod_delayed_work_on(WORK_CPU_UNBOUND, &q->requeue_work, 0);
 }
 EXPORT_SYMBOL(blk_mq_kick_requeue_list);
 
 void blk_mq_delay_kick_requeue_list(struct request_queue *q,
                                     unsigned long msecs)
 {
         kblockd_mod_delayed_work_on(WORK_CPU_UNBOUND, &q->requeue_work,
                                     msecs_to_jiffies(msecs));
 }
 EXPORT_SYMBOL(blk_mq_delay_kick_requeue_list);
 
 struct request *blk_mq_tag_to_rq(struct blk_mq_tags *tags, unsigned int tag)
 {
         if (tag < tags->nr_tags) {
                 prefetch(tags->rqs[tag]);
                 return tags->rqs[tag];
         }
 
         return NULL;
 }
 EXPORT_SYMBOL(blk_mq_tag_to_rq);
 
 static bool blk_mq_rq_inflight(struct blk_mq_hw_ctx *hctx, struct request *rq,
                                void *priv, bool reserved)
 {
         /*
          * If we find a request that is inflight and the queue matches,
          * we know the queue is busy. Return false to stop the iteration.
          */
         if (rq->state == MQ_RQ_IN_FLIGHT && rq->q == hctx->queue) {
                 bool *busy = priv;
 
                 *busy = true;
                 return false;
         }
 
         return true;
 }
 
 bool blk_mq_queue_inflight(struct request_queue *q)
 {
         bool busy = false;
 
         blk_mq_queue_tag_busy_iter(q, blk_mq_rq_inflight, &busy);
         return busy;
 }
 EXPORT_SYMBOL_GPL(blk_mq_queue_inflight);
 
 static void blk_mq_rq_timed_out(struct request *req, bool reserved)
 {
         req->rq_flags |= RQF_TIMED_OUT;
         if (req->q->mq_ops->timeout) {
                 enum blk_eh_timer_return ret;
 
                 ret = req->q->mq_ops->timeout(req, reserved);
                 if (ret == BLK_EH_DONE)
                         return;
                 WARN_ON_ONCE(ret != BLK_EH_RESET_TIMER);
         }
 
         blk_add_timer(req);
 }
 
 static bool blk_mq_req_expired(struct request *rq, unsigned long *next)
 {
         unsigned long deadline;
 
         if (blk_mq_rq_state(rq) != MQ_RQ_IN_FLIGHT)
                 return false;
         if (rq->rq_flags & RQF_TIMED_OUT)
                 return false;
 
         deadline = READ_ONCE(rq->deadline);
         if (time_after_eq(jiffies, deadline))
                 return true;
 
         if (*next == 0)
                 *next = deadline;
         else if (time_after(*next, deadline))
                 *next = deadline;
         return false;
 }
 
 static bool blk_mq_check_expired(struct blk_mq_hw_ctx *hctx,
                 struct request *rq, void *priv, bool reserved)
 {
         unsigned long *next = priv;
 
         /*
          * Just do a quick check if it is expired before locking the request in
          * so we're not unnecessarilly synchronizing across CPUs.
          */
         if (!blk_mq_req_expired(rq, next))
                 return true;
 
         /*
          * We have reason to believe the request may be expired. Take a
          * reference on the request to lock this request lifetime into its
          * currently allocated context to prevent it from being reallocated in
          * the event the completion by-passes this timeout handler.
          *
          * If the reference was already released, then the driver beat the
          * timeout handler to posting a natural completion.
          */
         if (!refcount_inc_not_zero(&rq->ref))
                 return true;
 
         /*
          * The request is now locked and cannot be reallocated underneath the
          * timeout handler's processing. Re-verify this exact request is truly
          * expired; if it is not expired, then the request was completed and
          * reallocated as a new request.
          */
         if (blk_mq_req_expired(rq, next))
                 blk_mq_rq_timed_out(rq, reserved);
 
         if (is_flush_rq(rq, hctx))
                 rq->end_io(rq, 0);
         else if (refcount_dec_and_test(&rq->ref))
                 __blk_mq_free_request(rq);
 
         return true;
 }
 
 static void blk_mq_timeout_work(struct work_struct *work)
 {
         struct request_queue *q =
                 container_of(work, struct request_queue, timeout_work);
         unsigned long next = 0;
         struct blk_mq_hw_ctx *hctx;
         int i;
 
         /* A deadlock might occur if a request is stuck requiring a
          * timeout at the same time a queue freeze is waiting
          * completion, since the timeout code would not be able to
          * acquire the queue reference here.
          *
          * That's why we don't use blk_queue_enter here; instead, we use
          * percpu_ref_tryget directly, because we need to be able to
          * obtain a reference even in the short window between the queue
          * starting to freeze, by dropping the first reference in
          * blk_freeze_queue_start, and the moment the last request is
          * consumed, marked by the instant q_usage_counter reaches
          * zero.
          */
         if (!percpu_ref_tryget(&q->q_usage_counter))
                 return;
 
         blk_mq_queue_tag_busy_iter(q, blk_mq_check_expired, &next);
 
         if (next != 0) {
                 mod_timer(&q->timeout, next);
         } else {
                 /*
                  * Request timeouts are handled as a forward rolling timer. If
                  * we end up here it means that no requests are pending and
                  * also that no request has been pending for a while. Mark
                  * each hctx as idle.
                  */
                 queue_for_each_hw_ctx(q, hctx, i) {
                         /* the hctx may be unmapped, so check it here */
                         if (blk_mq_hw_queue_mapped(hctx))
                                 blk_mq_tag_idle(hctx);
                 }
         }
         blk_queue_exit(q);
 }
 
 struct flush_busy_ctx_data {
         struct blk_mq_hw_ctx *hctx;
         struct list_head *list;
 };
 
 static bool flush_busy_ctx(struct sbitmap *sb, unsigned int bitnr, void *data)
 {
         struct flush_busy_ctx_data *flush_data = data;
         struct blk_mq_hw_ctx *hctx = flush_data->hctx;
         struct blk_mq_ctx *ctx = hctx->ctxs[bitnr];
         enum hctx_type type = hctx->type;
 
         spin_lock(&ctx->lock);
         list_splice_tail_init(&ctx->rq_lists[type], flush_data->list);
         sbitmap_clear_bit(sb, bitnr);
         spin_unlock(&ctx->lock);
         return true;
 }
 
 /*
  * Process software queues that have been marked busy, splicing them
  * to the for-dispatch
  */
 void blk_mq_flush_busy_ctxs(struct blk_mq_hw_ctx *hctx, struct list_head *list)
 {
         struct flush_busy_ctx_data data = {
                 .hctx = hctx,
                 .list = list,
         };
 
         sbitmap_for_each_set(&hctx->ctx_map, flush_busy_ctx, &data);
 }
 EXPORT_SYMBOL_GPL(blk_mq_flush_busy_ctxs);
 
 struct dispatch_rq_data {
         struct blk_mq_hw_ctx *hctx;
         struct request *rq;
 };
 
 static bool dispatch_rq_from_ctx(struct sbitmap *sb, unsigned int bitnr,
                 void *data)
 {
         struct dispatch_rq_data *dispatch_data = data;
         struct blk_mq_hw_ctx *hctx = dispatch_data->hctx;
         struct blk_mq_ctx *ctx = hctx->ctxs[bitnr];
         enum hctx_type type = hctx->type;
 
         spin_lock(&ctx->lock);
         if (!list_empty(&ctx->rq_lists[type])) {
                 dispatch_data->rq = list_entry_rq(ctx->rq_lists[type].next);
                 list_del_init(&dispatch_data->rq->queuelist);
                 if (list_empty(&ctx->rq_lists[type]))
                         sbitmap_clear_bit(sb, bitnr);
         }
         spin_unlock(&ctx->lock);
 
         return !dispatch_data->rq;
 }
 
 struct request *blk_mq_dequeue_from_ctx(struct blk_mq_hw_ctx *hctx,
                                         struct blk_mq_ctx *start)
 {
         unsigned off = start ? start->index_hw[hctx->type] : 0;
         struct dispatch_rq_data data = {
                 .hctx = hctx,
                 .rq   = NULL,
         };
 
         __sbitmap_for_each_set(&hctx->ctx_map, off,
                                dispatch_rq_from_ctx, &data);
 
         return data.rq;
 }
 
 static inline unsigned int queued_to_index(unsigned int queued)
 {
         if (!queued)
                 return 0;
 
         return min(BLK_MQ_MAX_DISPATCH_ORDER - 1, ilog2(queued) + 1);
 }
 
 bool blk_mq_get_driver_tag(struct request *rq)
 {
         struct blk_mq_alloc_data data = {
                 .q = rq->q,
                 .hctx = rq->mq_hctx,
                 .flags = BLK_MQ_REQ_NOWAIT,
                 .cmd_flags = rq->cmd_flags,
         };
         bool shared;
 
         if (rq->tag != -1)
                 return true;
 
         if (blk_mq_tag_is_reserved(data.hctx->sched_tags, rq->internal_tag))
                 data.flags |= BLK_MQ_REQ_RESERVED;
 
         shared = blk_mq_tag_busy(data.hctx);
         rq->tag = blk_mq_get_tag(&data);
         if (rq->tag >= 0) {
                 if (shared) {
                         rq->rq_flags |= RQF_MQ_INFLIGHT;
                         atomic_inc(&data.hctx->nr_active);
                 }
                 data.hctx->tags->rqs[rq->tag] = rq;
         }
 
         return rq->tag != -1;
 }
 
 static int blk_mq_dispatch_wake(wait_queue_entry_t *wait, unsigned mode,
                                 int flags, void *key)
 {
         struct blk_mq_hw_ctx *hctx;
 
         hctx = container_of(wait, struct blk_mq_hw_ctx, dispatch_wait);
 
         spin_lock(&hctx->dispatch_wait_lock);
         if (!list_empty(&wait->entry)) {
                 struct sbitmap_queue *sbq;
 
                 list_del_init(&wait->entry);
                 sbq = &hctx->tags->bitmap_tags;
                 atomic_dec(&sbq->ws_active);
         }
         spin_unlock(&hctx->dispatch_wait_lock);
 
         blk_mq_run_hw_queue(hctx, true);
         return 1;
 }
 
 /*
  * Mark us waiting for a tag. For shared tags, this involves hooking us into
  * the tag wakeups. For non-shared tags, we can simply mark us needing a
  * restart. For both cases, take care to check the condition again after
  * marking us as waiting.
  */
 static bool blk_mq_mark_tag_wait(struct blk_mq_hw_ctx *hctx,
                                  struct request *rq)
 {
         struct sbitmap_queue *sbq = &hctx->tags->bitmap_tags;
         struct wait_queue_head *wq;
         wait_queue_entry_t *wait;
         bool ret;
 
         if (!(hctx->flags & BLK_MQ_F_TAG_SHARED)) {
                 blk_mq_sched_mark_restart_hctx(hctx);
 
                 /*
                  * It's possible that a tag was freed in the window between the
                  * allocation failure and adding the hardware queue to the wait
                  * queue.
                  *
                  * Don't clear RESTART here, someone else could have set it.
                  * At most this will cost an extra queue run.
                  */
                 return blk_mq_get_driver_tag(rq);
         }
 
         wait = &hctx->dispatch_wait;
         if (!list_empty_careful(&wait->entry))
                 return false;
 
         wq = &bt_wait_ptr(sbq, hctx)->wait;
 
         spin_lock_irq(&wq->lock);
         spin_lock(&hctx->dispatch_wait_lock);
         if (!list_empty(&wait->entry)) {
                 spin_unlock(&hctx->dispatch_wait_lock);
                 spin_unlock_irq(&wq->lock);
                 return false;
         }
 
         atomic_inc(&sbq->ws_active);
         wait->flags &= ~WQ_FLAG_EXCLUSIVE;
         __add_wait_queue(wq, wait);
 
         /*
          * It's possible that a tag was freed in the window between the
          * allocation failure and adding the hardware queue to the wait
          * queue.
          */
         ret = blk_mq_get_driver_tag(rq);
         if (!ret) {
                 spin_unlock(&hctx->dispatch_wait_lock);
                 spin_unlock_irq(&wq->lock);
                 return false;
         }
 
         /*
          * We got a tag, remove ourselves from the wait queue to ensure
          * someone else gets the wakeup.
          */
         list_del_init(&wait->entry);
         atomic_dec(&sbq->ws_active);
         spin_unlock(&hctx->dispatch_wait_lock);
         spin_unlock_irq(&wq->lock);
 
         return true;
 }
 
 #define BLK_MQ_DISPATCH_BUSY_EWMA_WEIGHT  8
 #define BLK_MQ_DISPATCH_BUSY_EWMA_FACTOR  4
 /*
  * Update dispatch busy with the Exponential Weighted Moving Average(EWMA):
  * - EWMA is one simple way to compute running average value
  * - weight(7/8 and 1/8) is applied so that it can decrease exponentially
  * - take 4 as factor for avoiding to get too small(0) result, and this
  *   factor doesn't matter because EWMA decreases exponentially
  */
 static void blk_mq_update_dispatch_busy(struct blk_mq_hw_ctx *hctx, bool busy)
 {
         unsigned int ewma;
 
         if (hctx->queue->elevator)
                 return;
 
         ewma = hctx->dispatch_busy;
 
         if (!ewma && !busy)
                 return;
 
         ewma *= BLK_MQ_DISPATCH_BUSY_EWMA_WEIGHT - 1;
         if (busy)
                 ewma += 1 << BLK_MQ_DISPATCH_BUSY_EWMA_FACTOR;
         ewma /= BLK_MQ_DISPATCH_BUSY_EWMA_WEIGHT;
 
         hctx->dispatch_busy = ewma;
 }
 
 #define BLK_MQ_RESOURCE_DELAY   3               /* ms units */
 
 /*
  * Returns true if we did some work AND can potentially do more.
  */
 bool blk_mq_dispatch_rq_list(struct request_queue *q, struct list_head *list,
                              bool got_budget)
 {
         struct blk_mq_hw_ctx *hctx;
         struct request *rq, *nxt;
         bool no_tag = false;
         int errors, queued;
         blk_status_t ret = BLK_STS_OK;
 
         if (list_empty(list))
                 return false;
 
         WARN_ON(!list_is_singular(list) && got_budget);
 
         /*
          * Now process all the entries, sending them to the driver.
          */
         errors = queued = 0;
         do {
                 struct blk_mq_queue_data bd;
 
                 rq = list_first_entry(list, struct request, queuelist);
 
                 hctx = rq->mq_hctx;
                 if (!got_budget && !blk_mq_get_dispatch_budget(hctx))
                         break;
 
                 if (!blk_mq_get_driver_tag(rq)) {
                         /*
                          * The initial allocation attempt failed, so we need to
                          * rerun the hardware queue when a tag is freed. The
                          * waitqueue takes care of that. If the queue is run
                          * before we add this entry back on the dispatch list,
                          * we'll re-run it below.
                          */
                         if (!blk_mq_mark_tag_wait(hctx, rq)) {
                                 blk_mq_put_dispatch_budget(hctx);
                                 /*
                                  * For non-shared tags, the RESTART check
                                  * will suffice.
                                  */
                                 if (hctx->flags & BLK_MQ_F_TAG_SHARED)
                                         no_tag = true;
                                 break;
                         }
                 }
 
                 list_del_init(&rq->queuelist);
 
                 bd.rq = rq;
 
                 /*
                  * Flag last if we have no more requests, or if we have more
                  * but can't assign a driver tag to it.
                  */
                 if (list_empty(list))
                         bd.last = true;
                 else {
                         nxt = list_first_entry(list, struct request, queuelist);
                         bd.last = !blk_mq_get_driver_tag(nxt);
                 }
 
                 ret = q->mq_ops->queue_rq(hctx, &bd);
                 if (ret == BLK_STS_RESOURCE || ret == BLK_STS_DEV_RESOURCE) {
                         /*
                          * If an I/O scheduler has been configured and we got a
                          * driver tag for the next request already, free it
                          * again.
                          */
                         if (!list_empty(list)) {
                                 nxt = list_first_entry(list, struct request, queuelist);
                                 blk_mq_put_driver_tag(nxt);
                         }
                         list_add(&rq->queuelist, list);
                         __blk_mq_requeue_request(rq);
                         break;
                 }
 
                 if (unlikely(ret != BLK_STS_OK)) {
                         errors++;
                         blk_mq_end_request(rq, BLK_STS_IOERR);
                         continue;
                 }
 
                 queued++;
         } while (!list_empty(list));
 
         hctx->dispatched[queued_to_index(queued)]++;
 
         /*
          * Any items that need requeuing? Stuff them into hctx->dispatch,
          * that is where we will continue on next queue run.
          */
         if (!list_empty(list)) {
                 bool needs_restart;
 
                 /*
                  * If we didn't flush the entire list, we could have told
                  * the driver there was more coming, but that turned out to
                  * be a lie.
                  */
                 if (q->mq_ops->commit_rqs)
                         q->mq_ops->commit_rqs(hctx);
 
                 spin_lock(&hctx->lock);
                 list_splice_tail_init(list, &hctx->dispatch);
                 spin_unlock(&hctx->lock);
 
                 /*
                  * If SCHED_RESTART was set by the caller of this function and
                  * it is no longer set that means that it was cleared by another
                  * thread and hence that a queue rerun is needed.
                  *
                  * If 'no_tag' is set, that means that we failed getting
                  * a driver tag with an I/O scheduler attached. If our dispatch
                  * waitqueue is no longer active, ensure that we run the queue
                  * AFTER adding our entries back to the list.
                  *
                  * If no I/O scheduler has been configured it is possible that
                  * the hardware queue got stopped and restarted before requests
                  * were pushed back onto the dispatch list. Rerun the queue to
                  * avoid starvation. Notes:
                  * - blk_mq_run_hw_queue() checks whether or not a queue has
                  *   been stopped before rerunning a queue.
                  * - Some but not all block drivers stop a queue before
                  *   returning BLK_STS_RESOURCE. Two exceptions are scsi-mq
                  *   and dm-rq.
                  *
                  * If driver returns BLK_STS_RESOURCE and SCHED_RESTART
                  * bit is set, run queue after a delay to avoid IO stalls
                  * that could otherwise occur if the queue is idle.
                  */
                 needs_restart = blk_mq_sched_needs_restart(hctx);
                 if (!needs_restart ||
                     (no_tag && list_empty_careful(&hctx->dispatch_wait.entry)))
                         blk_mq_run_hw_queue(hctx, true);
                 else if (needs_restart && (ret == BLK_STS_RESOURCE))
                         blk_mq_delay_run_hw_queue(hctx, BLK_MQ_RESOURCE_DELAY);
 
                 blk_mq_update_dispatch_busy(hctx, true);
                 return false;
         } else
                 blk_mq_update_dispatch_busy(hctx, false);
 
         /*
          * If the host/device is unable to accept more work, inform the
          * caller of that.
          */
         if (ret == BLK_STS_RESOURCE || ret == BLK_STS_DEV_RESOURCE)
                 return false;
 
         return (queued + errors) != 0;
 }
 
 static void __blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx)
 {
         int srcu_idx;
 
         /*
          * We should be running this queue from one of the CPUs that
          * are mapped to it.
          *
          * There are at least two related races now between setting
          * hctx->next_cpu from blk_mq_hctx_next_cpu() and running
          * __blk_mq_run_hw_queue():
          *
          * - hctx->next_cpu is found offline in blk_mq_hctx_next_cpu(),
          *   but later it becomes online, then this warning is harmless
          *   at all
          *
          * - hctx->next_cpu is found online in blk_mq_hctx_next_cpu(),
          *   but later it becomes offline, then the warning can't be
          *   triggered, and we depend on blk-mq timeout handler to
          *   handle dispatched requests to this hctx
          */
         if (!cpumask_test_cpu(raw_smp_processor_id(), hctx->cpumask) &&
                 cpu_online(hctx->next_cpu)) {
                 printk(KERN_WARNING "run queue from wrong CPU %d, hctx %s\n",
                         raw_smp_processor_id(),
                         cpumask_empty(hctx->cpumask) ? "inactive": "active");
                 dump_stack();
         }
 
         /*
          * We can't run the queue inline with ints disabled. Ensure that
          * we catch bad users of this early.
          */
         WARN_ON_ONCE(in_interrupt());
 
         might_sleep_if(hctx->flags & BLK_MQ_F_BLOCKING);
 
         hctx_lock(hctx, &srcu_idx);
         blk_mq_sched_dispatch_requests(hctx);
         hctx_unlock(hctx, srcu_idx);
 }
 
 static inline int blk_mq_first_mapped_cpu(struct blk_mq_hw_ctx *hctx)
 {
         int cpu = cpumask_first_and(hctx->cpumask, cpu_online_mask);
 
         if (cpu >= nr_cpu_ids)
                 cpu = cpumask_first(hctx->cpumask);
         return cpu;
 }
 
 /*
  * It'd be great if the workqueue API had a way to pass
  * in a mask and had some smarts for more clever placement.
  * For now we just round-robin here, switching for every
  * BLK_MQ_CPU_WORK_BATCH queued items.
  */
 static int blk_mq_hctx_next_cpu(struct blk_mq_hw_ctx *hctx)
 {
         bool tried = false;
         int next_cpu = hctx->next_cpu;
 
         if (hctx->queue->nr_hw_queues == 1)
                 return WORK_CPU_UNBOUND;
 
         if (--hctx->next_cpu_batch <= 0) {
 select_cpu:
                 next_cpu = cpumask_next_and(next_cpu, hctx->cpumask,
                                 cpu_online_mask);
                 if (next_cpu >= nr_cpu_ids)
                         next_cpu = blk_mq_first_mapped_cpu(hctx);
                 hctx->next_cpu_batch = BLK_MQ_CPU_WORK_BATCH;
         }
 
         /*
          * Do unbound schedule if we can't find a online CPU for this hctx,
          * and it should only happen in the path of handling CPU DEAD.
          */
         if (!cpu_online(next_cpu)) {
                 if (!tried) {
                         tried = true;
                         goto select_cpu;
                 }
 
                 /*
                  * Make sure to re-select CPU next time once after CPUs
                  * in hctx->cpumask become online again.
                  */
                 hctx->next_cpu = next_cpu;
                 hctx->next_cpu_batch = 1;
                 return WORK_CPU_UNBOUND;
         }
 
         hctx->next_cpu = next_cpu;
         return next_cpu;
 }
 
 static void __blk_mq_delay_run_hw_queue(struct blk_mq_hw_ctx *hctx, bool async,
                                         unsigned long msecs)
 {
         if (unlikely(blk_mq_hctx_stopped(hctx)))
                 return;
 
         if (!async && !(hctx->flags & BLK_MQ_F_BLOCKING)) {
                 int cpu = get_cpu();
                 if (cpumask_test_cpu(cpu, hctx->cpumask)) {
                         __blk_mq_run_hw_queue(hctx);
                         put_cpu();
                         return;
                 }
 
                 put_cpu();
         }
 
         kblockd_mod_delayed_work_on(blk_mq_hctx_next_cpu(hctx), &hctx->run_work,
                                     msecs_to_jiffies(msecs));
 }
 
 void blk_mq_delay_run_hw_queue(struct blk_mq_hw_ctx *hctx, unsigned long msecs)
 {
         __blk_mq_delay_run_hw_queue(hctx, true, msecs);
 }
 EXPORT_SYMBOL(blk_mq_delay_run_hw_queue);
 
 void blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx, bool async)
 {
         int srcu_idx;
         bool need_run;
 
         /*
          * When queue is quiesced, we may be switching io scheduler, or
          * updating nr_hw_queues, or other things, and we can't run queue
          * any more, even __blk_mq_hctx_has_pending() can't be called safely.
          *
          * And queue will be rerun in blk_mq_unquiesce_queue() if it is
          * quiesced.
          */
         hctx_lock(hctx, &srcu_idx);
         need_run = !blk_queue_quiesced(hctx->queue) &&
                 blk_mq_hctx_has_pending(hctx);
         hctx_unlock(hctx, srcu_idx);
 
         if (need_run)
                 __blk_mq_delay_run_hw_queue(hctx, async, 0);
 }
 EXPORT_SYMBOL(blk_mq_run_hw_queue);
 
 void blk_mq_run_hw_queues(struct request_queue *q, bool async)
 {
         struct blk_mq_hw_ctx *hctx;
         int i;
 
         queue_for_each_hw_ctx(q, hctx, i) {
                 if (blk_mq_hctx_stopped(hctx))
                         continue;
 
                 blk_mq_run_hw_queue(hctx, async);
         }
 }
 EXPORT_SYMBOL(blk_mq_run_hw_queues);
 
 /**
  * blk_mq_queue_stopped() - check whether one or more hctxs have been stopped
  * @q: request queue.
  *
  * The caller is responsible for serializing this function against
  * blk_mq_{start,stop}_hw_queue().
  */
 bool blk_mq_queue_stopped(struct request_queue *q)
 {
         struct blk_mq_hw_ctx *hctx;
         int i;
 
         queue_for_each_hw_ctx(q, hctx, i)
                 if (blk_mq_hctx_stopped(hctx))
                         return true;
 
         return false;
 }
 EXPORT_SYMBOL(blk_mq_queue_stopped);
 
 /*
  * This function is often used for pausing .queue_rq() by driver when
  * there isn't enough resource or some conditions aren't satisfied, and
  * BLK_STS_RESOURCE is usually returned.
  *
  * We do not guarantee that dispatch can be drained or blocked
  * after blk_mq_stop_hw_queue() returns. Please use
  * blk_mq_quiesce_queue() for that requirement.
  */
 void blk_mq_stop_hw_queue(struct blk_mq_hw_ctx *hctx)
 {
         cancel_delayed_work(&hctx->run_work);
 
         set_bit(BLK_MQ_S_STOPPED, &hctx->state);
 }
 EXPORT_SYMBOL(blk_mq_stop_hw_queue);
 
 /*
  * This function is often used for pausing .queue_rq() by driver when
  * there isn't enough resource or some conditions aren't satisfied, and
  * BLK_STS_RESOURCE is usually returned.
  *
  * We do not guarantee that dispatch can be drained or blocked
  * after blk_mq_stop_hw_queues() returns. Please use
  * blk_mq_quiesce_queue() for that requirement.
  */
 void blk_mq_stop_hw_queues(struct request_queue *q)
 {
         struct blk_mq_hw_ctx *hctx;
         int i;
 
         queue_for_each_hw_ctx(q, hctx, i)
                 blk_mq_stop_hw_queue(hctx);
 }
 EXPORT_SYMBOL(blk_mq_stop_hw_queues);
 
 void blk_mq_start_hw_queue(struct blk_mq_hw_ctx *hctx)
 {
         clear_bit(BLK_MQ_S_STOPPED, &hctx->state);
 
         blk_mq_run_hw_queue(hctx, false);
 }
 EXPORT_SYMBOL(blk_mq_start_hw_queue);
 
 void blk_mq_start_hw_queues(struct request_queue *q)
 {
         struct blk_mq_hw_ctx *hctx;
         int i;
 
         queue_for_each_hw_ctx(q, hctx, i)
                 blk_mq_start_hw_queue(hctx);
 }
 EXPORT_SYMBOL(blk_mq_start_hw_queues);
 
 void blk_mq_start_stopped_hw_queue(struct blk_mq_hw_ctx *hctx, bool async)
 {
         if (!blk_mq_hctx_stopped(hctx))
                 return;
 
         clear_bit(BLK_MQ_S_STOPPED, &hctx->state);
         blk_mq_run_hw_queue(hctx, async);
 }
 EXPORT_SYMBOL_GPL(blk_mq_start_stopped_hw_queue);
 
 void blk_mq_start_stopped_hw_queues(struct request_queue *q, bool async)
 {
         struct blk_mq_hw_ctx *hctx;
         int i;
 
         queue_for_each_hw_ctx(q, hctx, i)
                 blk_mq_start_stopped_hw_queue(hctx, async);
 }
 EXPORT_SYMBOL(blk_mq_start_stopped_hw_queues);
 
 static void blk_mq_run_work_fn(struct work_struct *work)
 {
         struct blk_mq_hw_ctx *hctx;
 
         hctx = container_of(work, struct blk_mq_hw_ctx, run_work.work);
 
         /*
          * If we are stopped, don't run the queue.
          */
         if (test_bit(BLK_MQ_S_STOPPED, &hctx->state))
                 return;
 
         __blk_mq_run_hw_queue(hctx);
 }
 
 static inline void __blk_mq_insert_req_list(struct blk_mq_hw_ctx *hctx,
                                             struct request *rq,
                                             bool at_head)
 {
         struct blk_mq_ctx *ctx = rq->mq_ctx;
         enum hctx_type type = hctx->type;
 
         lockdep_assert_held(&ctx->lock);
 
         trace_block_rq_insert(hctx->queue, rq);
 
         if (at_head)
                 list_add(&rq->queuelist, &ctx->rq_lists[type]);
         else
                 list_add_tail(&rq->queuelist, &ctx->rq_lists[type]);
 }
 
 void __blk_mq_insert_request(struct blk_mq_hw_ctx *hctx, struct request *rq,
                              bool at_head)
 {
         struct blk_mq_ctx *ctx = rq->mq_ctx;
 
         lockdep_assert_held(&ctx->lock);
 
         __blk_mq_insert_req_list(hctx, rq, at_head);
         blk_mq_hctx_mark_pending(hctx, ctx);
 }
 
 /*
  * Should only be used carefully, when the caller knows we want to
  * bypass a potential IO scheduler on the target device.
  */
 void blk_mq_request_bypass_insert(struct request *rq, bool at_head,
                                   bool run_queue)
 {
         struct blk_mq_hw_ctx *hctx = rq->mq_hctx;
 
         spin_lock(&hctx->lock);
         if (at_head)
                 list_add(&rq->queuelist, &hctx->dispatch);
         else
                 list_add_tail(&rq->queuelist, &hctx->dispatch);
         spin_unlock(&hctx->lock);
 
         if (run_queue)
                 blk_mq_run_hw_queue(hctx, false);
 }
 
 void blk_mq_insert_requests(struct blk_mq_hw_ctx *hctx, struct blk_mq_ctx *ctx,
                             struct list_head *list)
 
 {
         struct request *rq;
         enum hctx_type type = hctx->type;
 
         /*
          * preemption doesn't flush plug list, so it's possible ctx->cpu is
          * offline now
          */
         list_for_each_entry(rq, list, queuelist) {
                 BUG_ON(rq->mq_ctx != ctx);
                 trace_block_rq_insert(hctx->queue, rq);
         }
 
         spin_lock(&ctx->lock);
         list_splice_tail_init(list, &ctx->rq_lists[type]);
         blk_mq_hctx_mark_pending(hctx, ctx);
         spin_unlock(&ctx->lock);
 }
 
 static int plug_rq_cmp(void *priv, struct list_head *a, struct list_head *b)
 {
         struct request *rqa = container_of(a, struct request, queuelist);
         struct request *rqb = container_of(b, struct request, queuelist);
 
         if (rqa->mq_ctx < rqb->mq_ctx)
                 return -1;
         else if (rqa->mq_ctx > rqb->mq_ctx)
                 return 1;
         else if (rqa->mq_hctx < rqb->mq_hctx)
                 return -1;
         else if (rqa->mq_hctx > rqb->mq_hctx)
                 return 1;
 
         return blk_rq_pos(rqa) > blk_rq_pos(rqb);
 }
 
 void blk_mq_flush_plug_list(struct blk_plug *plug, bool from_schedule)
 {
         struct blk_mq_hw_ctx *this_hctx;
         struct blk_mq_ctx *this_ctx;
         struct request_queue *this_q;
         struct request *rq;
         LIST_HEAD(list);
         LIST_HEAD(rq_list);
         unsigned int depth;
 
         list_splice_init(&plug->mq_list, &list);
 
         if (plug->rq_count > 2 && plug->multiple_queues)
                 list_sort(NULL, &list, plug_rq_cmp);
 
         plug->rq_count = 0;
 
         this_q = NULL;
         this_hctx = NULL;
         this_ctx = NULL;
         depth = 0;
 
         while (!list_empty(&list)) {
                 rq = list_entry_rq(list.next);
                 list_del_init(&rq->queuelist);
                 BUG_ON(!rq->q);
                 if (rq->mq_hctx != this_hctx || rq->mq_ctx != this_ctx) {
                         if (this_hctx) {
                                 trace_block_unplug(this_q, depth, !from_schedule);
                                 blk_mq_sched_insert_requests(this_hctx, this_ctx,
                                                                 &rq_list,
                                                                 from_schedule);
                         }
 
                         this_q = rq->q;
                         this_ctx = rq->mq_ctx;
                         this_hctx = rq->mq_hctx;
                         depth = 0;
                 }
 
                 depth++;
                 list_add_tail(&rq->queuelist, &rq_list);
         }
 
         /*
          * If 'this_hctx' is set, we know we have entries to complete
          * on 'rq_list'. Do those.
          */
         if (this_hctx) {
                 trace_block_unplug(this_q, depth, !from_schedule);
                 blk_mq_sched_insert_requests(this_hctx, this_ctx, &rq_list,
                                                 from_schedule);
         }
 }
 
 static void blk_mq_bio_to_request(struct request *rq, struct bio *bio,
                 unsigned int nr_segs)
 {
         if (bio->bi_opf & REQ_RAHEAD)
                 rq->cmd_flags |= REQ_FAILFAST_MASK;
 
         rq->__sector = bio->bi_iter.bi_sector;
         rq->write_hint = bio->bi_write_hint;
         blk_rq_bio_prep(rq, bio, nr_segs);
 
         blk_account_io_start(rq, true);
 }
 
 static blk_status_t __blk_mq_issue_directly(struct blk_mq_hw_ctx *hctx,
                                             struct request *rq,
                                             blk_qc_t *cookie, bool last)
 {
         struct request_queue *q = rq->q;
         struct blk_mq_queue_data bd = {
                 .rq = rq,
                 .last = last,
         };
         blk_qc_t new_cookie;
         blk_status_t ret;
 
         new_cookie = request_to_qc_t(hctx, rq);
 
         /*
          * For OK queue, we are done. For error, caller may kill it.
          * Any other error (busy), just add it to our list as we
          * previously would have done.
          */
         ret = q->mq_ops->queue_rq(hctx, &bd);
         switch (ret) {
         case BLK_STS_OK:
                 blk_mq_update_dispatch_busy(hctx, false);
                 *cookie = new_cookie;
                 break;
         case BLK_STS_RESOURCE:
         case BLK_STS_DEV_RESOURCE:
                 blk_mq_update_dispatch_busy(hctx, true);
                 __blk_mq_requeue_request(rq);
                 break;
         default:
                 blk_mq_update_dispatch_busy(hctx, false);
                 *cookie = BLK_QC_T_NONE;
                 break;
         }
 
         return ret;
 }
 
 static blk_status_t __blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
                                                 struct request *rq,
                                                 blk_qc_t *cookie,
                                                 bool bypass_insert, bool last)
 {
         struct request_queue *q = rq->q;
         bool run_queue = true;
 
         /*
          * RCU or SRCU read lock is needed before checking quiesced flag.
          *
          * When queue is stopped or quiesced, ignore 'bypass_insert' from
          * blk_mq_request_issue_directly(), and return BLK_STS_OK to caller,
          * and avoid driver to try to dispatch again.
          */
         if (blk_mq_hctx_stopped(hctx) || blk_queue_quiesced(q)) {
                 run_queue = false;
                 bypass_insert = false;
                 goto insert;
         }
 
         if (q->elevator && !bypass_insert)
                 goto insert;
 
         if (!blk_mq_get_dispatch_budget(hctx))
                 goto insert;
 
         if (!blk_mq_get_driver_tag(rq)) {
                 blk_mq_put_dispatch_budget(hctx);
                 goto insert;
         }
 
         return __blk_mq_issue_directly(hctx, rq, cookie, last);
 insert:
         if (bypass_insert)
                 return BLK_STS_RESOURCE;
 
         blk_mq_request_bypass_insert(rq, false, run_queue);
         return BLK_STS_OK;
 }
 
 static void blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
                 struct request *rq, blk_qc_t *cookie)
 {
         blk_status_t ret;
         int srcu_idx;
 
         might_sleep_if(hctx->flags & BLK_MQ_F_BLOCKING);
 
         hctx_lock(hctx, &srcu_idx);
 
         ret = __blk_mq_try_issue_directly(hctx, rq, cookie, false, true);
         if (ret == BLK_STS_RESOURCE || ret == BLK_STS_DEV_RESOURCE)
                 blk_mq_request_bypass_insert(rq, false, true);
         else if (ret != BLK_STS_OK)
                 blk_mq_end_request(rq, ret);
 
         hctx_unlock(hctx, srcu_idx);
 }
 
 blk_status_t blk_mq_request_issue_directly(struct request *rq, bool last)
 {
         blk_status_t ret;
         int srcu_idx;
         blk_qc_t unused_cookie;
         struct blk_mq_hw_ctx *hctx = rq->mq_hctx;
 
         hctx_lock(hctx, &srcu_idx);
         ret = __blk_mq_try_issue_directly(hctx, rq, &unused_cookie, true, last);
         hctx_unlock(hctx, srcu_idx);
 
         return ret;
 }
 
 void blk_mq_try_issue_list_directly(struct blk_mq_hw_ctx *hctx,
                 struct list_head *list)
 {
         while (!list_empty(list)) {
                 blk_status_t ret;
                 struct request *rq = list_first_entry(list, struct request,
                                 queuelist);
 
                 list_del_init(&rq->queuelist);
                 ret = blk_mq_request_issue_directly(rq, list_empty(list));
                 if (ret != BLK_STS_OK) {
                         if (ret == BLK_STS_RESOURCE ||
                                         ret == BLK_STS_DEV_RESOURCE) {
                                 blk_mq_request_bypass_insert(rq, false,
                                                         list_empty(list));
                                 break;
                         }
                         blk_mq_end_request(rq, ret);
                 }
         }
 
         /*
          * If we didn't flush the entire list, we could have told
          * the driver there was more coming, but that turned out to
          * be a lie.
          */
         if (!list_empty(list) && hctx->queue->mq_ops->commit_rqs)
                 hctx->queue->mq_ops->commit_rqs(hctx);
 }
 
 static void blk_add_rq_to_plug(struct blk_plug *plug, struct request *rq)
 {
         list_add_tail(&rq->queuelist, &plug->mq_list);
         plug->rq_count++;
         if (!plug->multiple_queues && !list_is_singular(&plug->mq_list)) {
                 struct request *tmp;
 
                 tmp = list_first_entry(&plug->mq_list, struct request,
                                                 queuelist);
                 if (tmp->q != rq->q)
                         plug->multiple_queues = true;
         }
 }
 
 static blk_qc_t blk_mq_make_request(struct request_queue *q, struct bio *bio)
 {
         const int is_sync = op_is_sync(bio->bi_opf);
         const int is_flush_fua = op_is_flush(bio->bi_opf);
         struct blk_mq_alloc_data data = { .flags = 0};
         struct request *rq;
         struct blk_plug *plug;
         struct request *same_queue_rq = NULL;
         unsigned int nr_segs;
         blk_qc_t cookie;
 
         blk_queue_bounce(q, &bio);
         __blk_queue_split(q, &bio, &nr_segs);
 
         if (!bio_integrity_prep(bio))
                 return BLK_QC_T_NONE;
 
         if (!is_flush_fua && !blk_queue_nomerges(q) &&
             blk_attempt_plug_merge(q, bio, nr_segs, &same_queue_rq))
                 return BLK_QC_T_NONE;
 
         if (blk_mq_sched_bio_merge(q, bio, nr_segs))
                 return BLK_QC_T_NONE;
 
         rq_qos_throttle(q, bio);
 
         data.cmd_flags = bio->bi_opf;
         rq = blk_mq_get_request(q, bio, &data);
         if (unlikely(!rq)) {
                 rq_qos_cleanup(q, bio);
                 if (bio->bi_opf & REQ_NOWAIT)
                         bio_wouldblock_error(bio);
                 return BLK_QC_T_NONE;
         }
 
         trace_block_getrq(q, bio, bio->bi_opf);
 
         rq_qos_track(q, rq, bio);
 
         cookie = request_to_qc_t(data.hctx, rq);
 
         blk_mq_bio_to_request(rq, bio, nr_segs);
 
         plug = blk_mq_plug(q, bio);
         if (unlikely(is_flush_fua)) {
                 /* bypass scheduler for flush rq */
                 blk_insert_flush(rq);
                 blk_mq_run_hw_queue(data.hctx, true);
         } else if (plug && (q->nr_hw_queues == 1 || q->mq_ops->commit_rqs ||
                                 !blk_queue_nonrot(q))) {
                 /*
                  * Use plugging if we have a ->commit_rqs() hook as well, as
                  * we know the driver uses bd->last in a smart fashion.
                  *
                  * Use normal plugging if this disk is slow HDD, as sequential
                  * IO may benefit a lot from plug merging.
                  */
                 unsigned int request_count = plug->rq_count;
                 struct request *last = NULL;
 
                 if (!request_count)
                         trace_block_plug(q);
                 else
                         last = list_entry_rq(plug->mq_list.prev);
 
                 if (request_count >= BLK_MAX_REQUEST_COUNT || (last &&
                     blk_rq_bytes(last) >= BLK_PLUG_FLUSH_SIZE)) {
                         blk_flush_plug_list(plug, false);
                         trace_block_plug(q);
                 }
 
                 blk_add_rq_to_plug(plug, rq);
         } else if (q->elevator) {
                 blk_mq_sched_insert_request(rq, false, true, true);
         } else if (plug && !blk_queue_nomerges(q)) {
                 /*
                  * We do limited plugging. If the bio can be merged, do that.
                  * Otherwise the existing request in the plug list will be
                  * issued. So the plug list will have one request at most
                  * The plug list might get flushed before this. If that happens,
                  * the plug list is empty, and same_queue_rq is invalid.
                  */
                 if (list_empty(&plug->mq_list))
                         same_queue_rq = NULL;
                 if (same_queue_rq) {
                         list_del_init(&same_queue_rq->queuelist);
                         plug->rq_count--;
                 }
                 blk_add_rq_to_plug(plug, rq);
                 trace_block_plug(q);
 
                 if (same_queue_rq) {
                         data.hctx = same_queue_rq->mq_hctx;
                         trace_block_unplug(q, 1, true);
                         blk_mq_try_issue_directly(data.hctx, same_queue_rq,
                                         &cookie);
                 }
         } else if ((q->nr_hw_queues > 1 && is_sync) ||
                         !data.hctx->dispatch_busy) {
                 blk_mq_try_issue_directly(data.hctx, rq, &cookie);
         } else {
                 blk_mq_sched_insert_request(rq, false, true, true);
         }
 
         return cookie;
 }
 
 void blk_mq_free_rqs(struct blk_mq_tag_set *set, struct blk_mq_tags *tags,
                      unsigned int hctx_idx)
 {
         struct page *page;
 
         if (tags->rqs && set->ops->exit_request) {
                 int i;
 
                 for (i = 0; i < tags->nr_tags; i++) {
                         struct request *rq = tags->static_rqs[i];
 
                         if (!rq)
                                 continue;
                         set->ops->exit_request(set, rq, hctx_idx);
                         tags->static_rqs[i] = NULL;
                 }
         }
 
         while (!list_empty(&tags->page_list)) {
                 page = list_first_entry(&tags->page_list, struct page, lru);
                 list_del_init(&page->lru);
                 /*
                  * Remove kmemleak object previously allocated in
                  * blk_mq_alloc_rqs().
                  */
                 kmemleak_free(page_address(page));
                 __free_pages(page, page->private);
         }
 }
 
 void blk_mq_free_rq_map(struct blk_mq_tags *tags)
 {
         kfree(tags->rqs);
         tags->rqs = NULL;
         kfree(tags->static_rqs);
         tags->static_rqs = NULL;
 
         blk_mq_free_tags(tags);
 }
 
 struct blk_mq_tags *blk_mq_alloc_rq_map(struct blk_mq_tag_set *set,
                                         unsigned int hctx_idx,
                                         unsigned int nr_tags,
                                         unsigned int reserved_tags)
 {
         struct blk_mq_tags *tags;
         int node;
 
         node = blk_mq_hw_queue_to_node(&set->map[HCTX_TYPE_DEFAULT], hctx_idx);
         if (node == NUMA_NO_NODE)
                 node = set->numa_node;
 
         tags = blk_mq_init_tags(nr_tags, reserved_tags, node,
                                 BLK_MQ_FLAG_TO_ALLOC_POLICY(set->flags));
         if (!tags)
                 return NULL;
 
         tags->rqs = kcalloc_node(nr_tags, sizeof(struct request *),
                                  GFP_NOIO | __GFP_NOWARN | __GFP_NORETRY,
                                  node);
         if (!tags->rqs) {
                 blk_mq_free_tags(tags);
                 return NULL;
         }
 
         tags->static_rqs = kcalloc_node(nr_tags, sizeof(struct request *),
                                         GFP_NOIO | __GFP_NOWARN | __GFP_NORETRY,
                                         node);
         if (!tags->static_rqs) {
                 kfree(tags->rqs);
                 blk_mq_free_tags(tags);
                 return NULL;
         }
 
         return tags;
 }
 
 static size_t order_to_size(unsigned int order)
 {
         return (size_t)PAGE_SIZE << order;
 }
 
 static int blk_mq_init_request(struct blk_mq_tag_set *set, struct request *rq,
                                unsigned int hctx_idx, int node)
 {
         int ret;
 
         if (set->ops->init_request) {
                 ret = set->ops->init_request(set, rq, hctx_idx, node);
                 if (ret)
                         return ret;
         }
 
         WRITE_ONCE(rq->state, MQ_RQ_IDLE);
         return 0;
 }
 
 int blk_mq_alloc_rqs(struct blk_mq_tag_set *set, struct blk_mq_tags *tags,
                      unsigned int hctx_idx, unsigned int depth)
 {
         unsigned int i, j, entries_per_page, max_order = 4;
         size_t rq_size, left;
         int node;
 
         node = blk_mq_hw_queue_to_node(&set->map[HCTX_TYPE_DEFAULT], hctx_idx);
         if (node == NUMA_NO_NODE)
                 node = set->numa_node;
 
         INIT_LIST_HEAD(&tags->page_list);
 
         /*
          * rq_size is the size of the request plus driver payload, rounded
          * to the cacheline size
          */
         rq_size = round_up(sizeof(struct request) + set->cmd_size,
                                 cache_line_size());
         left = rq_size * depth;
 
         for (i = 0; i < depth; ) {
                 int this_order = max_order;
                 struct page *page;
                 int to_do;
                 void *p;
 
                 while (this_order && left < order_to_size(this_order - 1))
                         this_order--;
 
                 do {
                         page = alloc_pages_node(node,
                                 GFP_NOIO | __GFP_NOWARN | __GFP_NORETRY | __GFP_ZERO,
                                 this_order);
                         if (page)
                                 break;
                         if (!this_order--)
                                 break;
                         if (order_to_size(this_order) < rq_size)
                                 break;
                 } while (1);
 
                 if (!page)
                         goto fail;
 
                 page->private = this_order;
                 list_add_tail(&page->lru, &tags->page_list);
 
                 p = page_address(page);
                 /*
                  * Allow kmemleak to scan these pages as they contain pointers
                  * to additional allocations like via ops->init_request().
                  */
                 kmemleak_alloc(p, order_to_size(this_order), 1, GFP_NOIO);
                 entries_per_page = order_to_size(this_order) / rq_size;
                 to_do = min(entries_per_page, depth - i);
                 left -= to_do * rq_size;
                 for (j = 0; j < to_do; j++) {
                         struct request *rq = p;
 
                         tags->static_rqs[i] = rq;
                         if (blk_mq_init_request(set, rq, hctx_idx, node)) {
                                 tags->static_rqs[i] = NULL;
                                 goto fail;
                         }
 
                         p += rq_size;
                         i++;
                 }
         }
         return 0;
 
 fail:
         blk_mq_free_rqs(set, tags, hctx_idx);
         return -ENOMEM;
 }
 
 /*
  * 'cpu' is going away. splice any existing rq_list entries from this
  * software queue to the hw queue dispatch list, and ensure that it
  * gets run.
  */
 static int blk_mq_hctx_notify_dead(unsigned int cpu, struct hlist_node *node)
 {
         struct blk_mq_hw_ctx *hctx;
         struct blk_mq_ctx *ctx;
         LIST_HEAD(tmp);
         enum hctx_type type;
 
         hctx = hlist_entry_safe(node, struct blk_mq_hw_ctx, cpuhp_dead);
         ctx = __blk_mq_get_ctx(hctx->queue, cpu);
         type = hctx->type;
 
         spin_lock(&ctx->lock);
         if (!list_empty(&ctx->rq_lists[type])) {
                 list_splice_init(&ctx->rq_lists[type], &tmp);
                 blk_mq_hctx_clear_pending(hctx, ctx);
         }
         spin_unlock(&ctx->lock);
 
         if (list_empty(&tmp))
                 return 0;
 
         spin_lock(&hctx->lock);
         list_splice_tail_init(&tmp, &hctx->dispatch);
         spin_unlock(&hctx->lock);
 
         blk_mq_run_hw_queue(hctx, true);
         return 0;
 }
 
 static void blk_mq_remove_cpuhp(struct blk_mq_hw_ctx *hctx)
 {
         cpuhp_state_remove_instance_nocalls(CPUHP_BLK_MQ_DEAD,
                                             &hctx->cpuhp_dead);
 }
 
 /* hctx->ctxs will be freed in queue's release handler */
 static void blk_mq_exit_hctx(struct request_queue *q,
                 struct blk_mq_tag_set *set,
                 struct blk_mq_hw_ctx *hctx, unsigned int hctx_idx)
 {
         if (blk_mq_hw_queue_mapped(hctx))
                 blk_mq_tag_idle(hctx);
 
         if (set->ops->exit_request)
                 set->ops->exit_request(set, hctx->fq->flush_rq, hctx_idx);
 
         if (set->ops->exit_hctx)
                 set->ops->exit_hctx(hctx, hctx_idx);
 
         blk_mq_remove_cpuhp(hctx);
 
         spin_lock(&q->unused_hctx_lock);
         list_add(&hctx->hctx_list, &q->unused_hctx_list);
         spin_unlock(&q->unused_hctx_lock);
 }
 
 static void blk_mq_exit_hw_queues(struct request_queue *q,
                 struct blk_mq_tag_set *set, int nr_queue)
 {
         struct blk_mq_hw_ctx *hctx;
         unsigned int i;
 
         queue_for_each_hw_ctx(q, hctx, i) {
                 if (i == nr_queue)
                         break;
                 blk_mq_debugfs_unregister_hctx(hctx);
                 blk_mq_exit_hctx(q, set, hctx, i);
         }
 }
 
 static int blk_mq_hw_ctx_size(struct blk_mq_tag_set *tag_set)
 {
         int hw_ctx_size = sizeof(struct blk_mq_hw_ctx);
 
         BUILD_BUG_ON(ALIGN(offsetof(struct blk_mq_hw_ctx, srcu),
                            __alignof__(struct blk_mq_hw_ctx)) !=
                      sizeof(struct blk_mq_hw_ctx));
 
         if (tag_set->flags & BLK_MQ_F_BLOCKING)
                 hw_ctx_size += sizeof(struct srcu_struct);
 
         return hw_ctx_size;
 }
 
 static int blk_mq_init_hctx(struct request_queue *q,
                 struct blk_mq_tag_set *set,
                 struct blk_mq_hw_ctx *hctx, unsigned hctx_idx)
 {
         hctx->queue_num = hctx_idx;
 
         cpuhp_state_add_instance_nocalls(CPUHP_BLK_MQ_DEAD, &hctx->cpuhp_dead);
 
         hctx->tags = set->tags[hctx_idx];
 
         if (set->ops->init_hctx &&
             set->ops->init_hctx(hctx, set->driver_data, hctx_idx))
                 goto unregister_cpu_notifier;
 
         if (blk_mq_init_request(set, hctx->fq->flush_rq, hctx_idx,
                                 hctx->numa_node))
                 goto exit_hctx;
         return 0;
 
  exit_hctx:
         if (set->ops->exit_hctx)
                 set->ops->exit_hctx(hctx, hctx_idx);
  unregister_cpu_notifier:
         blk_mq_remove_cpuhp(hctx);
         return -1;
 }
 
 static struct blk_mq_hw_ctx *
 blk_mq_alloc_hctx(struct request_queue *q, struct blk_mq_tag_set *set,
                 int node)
 {
         struct blk_mq_hw_ctx *hctx;
         gfp_t gfp = GFP_NOIO | __GFP_NOWARN | __GFP_NORETRY;
 
         hctx = kzalloc_node(blk_mq_hw_ctx_size(set), gfp, node);
         if (!hctx)
                 goto fail_alloc_hctx;
 
         if (!zalloc_cpumask_var_node(&hctx->cpumask, gfp, node))
                 goto free_hctx;
 
         atomic_set(&hctx->nr_active, 0);
         if (node == NUMA_NO_NODE)
                 node = set->numa_node;
         hctx->numa_node = node;
 
         INIT_DELAYED_WORK(&hctx->run_work, blk_mq_run_work_fn);
         spin_lock_init(&hctx->lock);
         INIT_LIST_HEAD(&hctx->dispatch);
         hctx->queue = q;
         hctx->flags = set->flags & ~BLK_MQ_F_TAG_SHARED;
 
         INIT_LIST_HEAD(&hctx->hctx_list);
 
         /*
          * Allocate space for all possible cpus to avoid allocation at
          * runtime
          */
         hctx->ctxs = kmalloc_array_node(nr_cpu_ids, sizeof(void *),
                         gfp, node);
         if (!hctx->ctxs)
                 goto free_cpumask;
 
         if (sbitmap_init_node(&hctx->ctx_map, nr_cpu_ids, ilog2(8),
                                 gfp, node))
                 goto free_ctxs;
         hctx->nr_ctx = 0;
 
         spin_lock_init(&hctx->dispatch_wait_lock);
         init_waitqueue_func_entry(&hctx->dispatch_wait, blk_mq_dispatch_wake);
         INIT_LIST_HEAD(&hctx->dispatch_wait.entry);
 
         hctx->fq = blk_alloc_flush_queue(q, hctx->numa_node, set->cmd_size,
                         gfp);
         if (!hctx->fq)
                 goto free_bitmap;
 
         if (hctx->flags & BLK_MQ_F_BLOCKING)
                 init_srcu_struct(hctx->srcu);
         blk_mq_hctx_kobj_init(hctx);
 
         return hctx;
 
  free_bitmap:
         sbitmap_free(&hctx->ctx_map);
  free_ctxs:
         kfree(hctx->ctxs);
  free_cpumask:
         free_cpumask_var(hctx->cpumask);
  free_hctx:
         kfree(hctx);
  fail_alloc_hctx:
         return NULL;
 }
 
 static void blk_mq_init_cpu_queues(struct request_queue *q,
                                    unsigned int nr_hw_queues)
 {
         struct blk_mq_tag_set *set = q->tag_set;
         unsigned int i, j;
 
         for_each_possible_cpu(i) {
                 struct blk_mq_ctx *__ctx = per_cpu_ptr(q->queue_ctx, i);
                 struct blk_mq_hw_ctx *hctx;
                 int k;
 
                 __ctx->cpu = i;
                 spin_lock_init(&__ctx->lock);
                 for (k = HCTX_TYPE_DEFAULT; k < HCTX_MAX_TYPES; k++)
                         INIT_LIST_HEAD(&__ctx->rq_lists[k]);
 
                 __ctx->queue = q;
 
                 /*
                  * Set local node, IFF we have more than one hw queue. If
                  * not, we remain on the home node of the device
                  */
                 for (j = 0; j < set->nr_maps; j++) {
                         hctx = blk_mq_map_queue_type(q, j, i);
                         if (nr_hw_queues > 1 && hctx->numa_node == NUMA_NO_NODE)
                                 hctx->numa_node = local_memory_node(cpu_to_node(i));
                 }
         }
 }
 
 static bool __blk_mq_alloc_rq_map(struct blk_mq_tag_set *set, int hctx_idx)
 {
         int ret = 0;
 
         set->tags[hctx_idx] = blk_mq_alloc_rq_map(set, hctx_idx,
                                         set->queue_depth, set->reserved_tags);
         if (!set->tags[hctx_idx])
                 return false;
 
         ret = blk_mq_alloc_rqs(set, set->tags[hctx_idx], hctx_idx,
                                 set->queue_depth);
         if (!ret)
                 return true;
 
         blk_mq_free_rq_map(set->tags[hctx_idx]);
         set->tags[hctx_idx] = NULL;
         return false;
 }
 
 static void blk_mq_free_map_and_requests(struct blk_mq_tag_set *set,
                                          unsigned int hctx_idx)
 {
         if (set->tags && set->tags[hctx_idx]) {
                 blk_mq_free_rqs(set, set->tags[hctx_idx], hctx_idx);
                 blk_mq_free_rq_map(set->tags[hctx_idx]);
                 set->tags[hctx_idx] = NULL;
         }
 }
 
 static void blk_mq_map_swqueue(struct request_queue *q)
 {
         unsigned int i, j, hctx_idx;
         struct blk_mq_hw_ctx *hctx;
         struct blk_mq_ctx *ctx;
         struct blk_mq_tag_set *set = q->tag_set;
 
         queue_for_each_hw_ctx(q, hctx, i) {
                 cpumask_clear(hctx->cpumask);
                 hctx->nr_ctx = 0;
                 hctx->dispatch_from = NULL;
         }
 
         /*
          * Map software to hardware queues.
          *
          * If the cpu isn't present, the cpu is mapped to first hctx.
          */
         for_each_possible_cpu(i) {
                 hctx_idx = set->map[HCTX_TYPE_DEFAULT].mq_map[i];
                 /* unmapped hw queue can be remapped after CPU topo changed */
                 if (!set->tags[hctx_idx] &&
                     !__blk_mq_alloc_rq_map(set, hctx_idx)) {
                         /*
                          * If tags initialization fail for some hctx,
                          * that hctx won't be brought online.  In this
                          * case, remap the current ctx to hctx[0] which
                          * is guaranteed to always have tags allocated
                          */
                         set->map[HCTX_TYPE_DEFAULT].mq_map[i] = 0;
                 }
 
                 ctx = per_cpu_ptr(q->queue_ctx, i);
                 for (j = 0; j < set->nr_maps; j++) {
                         if (!set->map[j].nr_queues) {
                                 ctx->hctxs[j] = blk_mq_map_queue_type(q,
                                                 HCTX_TYPE_DEFAULT, i);
                                 continue;
                         }
 
                         hctx = blk_mq_map_queue_type(q, j, i);
                         ctx->hctxs[j] = hctx;
                         /*
                          * If the CPU is already set in the mask, then we've
                          * mapped this one already. This can happen if
                          * devices share queues across queue maps.
                          */
                         if (cpumask_test_cpu(i, hctx->cpumask))
                                 continue;
 
                         cpumask_set_cpu(i, hctx->cpumask);
                         hctx->type = j;
                         ctx->index_hw[hctx->type] = hctx->nr_ctx;
                         hctx->ctxs[hctx->nr_ctx++] = ctx;
 
                         /*
                          * If the nr_ctx type overflows, we have exceeded the
                          * amount of sw queues we can support.
                          */
                         BUG_ON(!hctx->nr_ctx);
                 }
 
                 for (; j < HCTX_MAX_TYPES; j++)
                         ctx->hctxs[j] = blk_mq_map_queue_type(q,
                                         HCTX_TYPE_DEFAULT, i);
         }
 
         queue_for_each_hw_ctx(q, hctx, i) {
                 /*
                  * If no software queues are mapped to this hardware queue,
                  * disable it and free the request entries.
                  */
                 if (!hctx->nr_ctx) {
                         /* Never unmap queue 0.  We need it as a
                          * fallback in case of a new remap fails
                          * allocation
                          */
                         if (i && set->tags[i])
                                 blk_mq_free_map_and_requests(set, i);
 
                         hctx->tags = NULL;
                         continue;
                 }
 
                 hctx->tags = set->tags[i];
                 WARN_ON(!hctx->tags);
 
                 /*
                  * Set the map size to the number of mapped software queues.
                  * This is more accurate and more efficient than looping
                  * over all possibly mapped software queues.
                  */
                 sbitmap_resize(&hctx->ctx_map, hctx->nr_ctx);
 
                 /*
                  * Initialize batch roundrobin counts
                  */
                 hctx->next_cpu = blk_mq_first_mapped_cpu(hctx);
                 hctx->next_cpu_batch = BLK_MQ_CPU_WORK_BATCH;
         }
 }
 
 /*
  * Caller needs to ensure that we're either frozen/quiesced, or that
  * the queue isn't live yet.
  */
 static void queue_set_hctx_shared(struct request_queue *q, bool shared)
 {
         struct blk_mq_hw_ctx *hctx;
         int i;
 
         queue_for_each_hw_ctx(q, hctx, i) {
                 if (shared)
                         hctx->flags |= BLK_MQ_F_TAG_SHARED;
                 else
                         hctx->flags &= ~BLK_MQ_F_TAG_SHARED;
         }
 }
 
 static void blk_mq_update_tag_set_depth(struct blk_mq_tag_set *set,
                                         bool shared)
 {
         struct request_queue *q;
 
         lockdep_assert_held(&set->tag_list_lock);
 
         list_for_each_entry(q, &set->tag_list, tag_set_list) {
                 blk_mq_freeze_queue(q);
                 queue_set_hctx_shared(q, shared);
                 blk_mq_unfreeze_queue(q);
         }
 }
 
 static void blk_mq_del_queue_tag_set(struct request_queue *q)
 {
         struct blk_mq_tag_set *set = q->tag_set;
 
         mutex_lock(&set->tag_list_lock);
         list_del_rcu(&q->tag_set_list);
         if (list_is_singular(&set->tag_list)) {
                 /* just transitioned to unshared */
                 set->flags &= ~BLK_MQ_F_TAG_SHARED;
                 /* update existing queue */
                 blk_mq_update_tag_set_depth(set, false);
         }
         mutex_unlock(&set->tag_list_lock);
         INIT_LIST_HEAD(&q->tag_set_list);
 }
 
 static void blk_mq_add_queue_tag_set(struct blk_mq_tag_set *set,
                                      struct request_queue *q)
 {
         mutex_lock(&set->tag_list_lock);
 
         /*
          * Check to see if we're transitioning to shared (from 1 to 2 queues).
          */
         if (!list_empty(&set->tag_list) &&
             !(set->flags & BLK_MQ_F_TAG_SHARED)) {
                 set->flags |= BLK_MQ_F_TAG_SHARED;
                 /* update existing queue */
                 blk_mq_update_tag_set_depth(set, true);
         }
         if (set->flags & BLK_MQ_F_TAG_SHARED)
                 queue_set_hctx_shared(q, true);
         list_add_tail_rcu(&q->tag_set_list, &set->tag_list);
 
         mutex_unlock(&set->tag_list_lock);
 }
 
 /* All allocations will be freed in release handler of q->mq_kobj */
 static int blk_mq_alloc_ctxs(struct request_queue *q)
 {
         struct blk_mq_ctxs *ctxs;
         int cpu;
 
         ctxs = kzalloc(sizeof(*ctxs), GFP_KERNEL);
         if (!ctxs)
                 return -ENOMEM;
 
         ctxs->queue_ctx = alloc_percpu(struct blk_mq_ctx);
         if (!ctxs->queue_ctx)
                 goto fail;
 
         for_each_possible_cpu(cpu) {
                 struct blk_mq_ctx *ctx = per_cpu_ptr(ctxs->queue_ctx, cpu);
                 ctx->ctxs = ctxs;
         }
 
         q->mq_kobj = &ctxs->kobj;
         q->queue_ctx = ctxs->queue_ctx;
 
         return 0;
  fail:
         kfree(ctxs);
         return -ENOMEM;
 }
 
 /*
  * It is the actual release handler for mq, but we do it from
  * request queue's release handler for avoiding use-after-free
  * and headache because q->mq_kobj shouldn't have been introduced,
  * but we can't group ctx/kctx kobj without it.
  */
 void blk_mq_release(struct request_queue *q)
 {
         struct blk_mq_hw_ctx *hctx, *next;
         int i;
 
         queue_for_each_hw_ctx(q, hctx, i)
                 WARN_ON_ONCE(hctx && list_empty(&hctx->hctx_list));
 
         /* all hctx are in .unused_hctx_list now */
         list_for_each_entry_safe(hctx, next, &q->unused_hctx_list, hctx_list) {
                 list_del_init(&hctx->hctx_list);
                 kobject_put(&hctx->kobj);
         }
 
         kfree(q->queue_hw_ctx);
 
         /*
          * release .mq_kobj and sw queue's kobject now because
          * both share lifetime with request queue.
          */
         blk_mq_sysfs_deinit(q);
 }
 
 struct request_queue *blk_mq_init_queue(struct blk_mq_tag_set *set)
 {
         struct request_queue *uninit_q, *q;
 
         uninit_q = blk_alloc_queue_node(GFP_KERNEL, set->numa_node);
         if (!uninit_q)
                 return ERR_PTR(-ENOMEM);
 
         /*
          * Initialize the queue without an elevator. device_add_disk() will do
          * the initialization.
          */
         q = blk_mq_init_allocated_queue(set, uninit_q, false);
         if (IS_ERR(q))
                 blk_cleanup_queue(uninit_q);
 
         return q;
 }
 EXPORT_SYMBOL(blk_mq_init_queue);
 
 /*
  * Helper for setting up a queue with mq ops, given queue depth, and
  * the passed in mq ops flags.
  */
 struct request_queue *blk_mq_init_sq_queue(struct blk_mq_tag_set *set,
                                            const struct blk_mq_ops *ops,
                                            unsigned int queue_depth,
                                            unsigned int set_flags)
 {
         struct request_queue *q;
         int ret;
 
         memset(set, 0, sizeof(*set));
         set->ops = ops;
         set->nr_hw_queues = 1;
         set->nr_maps = 1;
         set->queue_depth = queue_depth;
         set->numa_node = NUMA_NO_NODE;
         set->flags = set_flags;
 
         ret = blk_mq_alloc_tag_set(set);
         if (ret)
                 return ERR_PTR(ret);
 
         q = blk_mq_init_queue(set);
         if (IS_ERR(q)) {
                 blk_mq_free_tag_set(set);
                 return q;
         }
 
         return q;
 }
 EXPORT_SYMBOL(blk_mq_init_sq_queue);
 
 static struct blk_mq_hw_ctx *blk_mq_alloc_and_init_hctx(
                 struct blk_mq_tag_set *set, struct request_queue *q,
                 int hctx_idx, int node)
 {
         struct blk_mq_hw_ctx *hctx = NULL, *tmp;
 
         /* reuse dead hctx first */
         spin_lock(&q->unused_hctx_lock);
         list_for_each_entry(tmp, &q->unused_hctx_list, hctx_list) {
                 if (tmp->numa_node == node) {
                         hctx = tmp;
                         break;
                 }
         }
         if (hctx)
                 list_del_init(&hctx->hctx_list);
         spin_unlock(&q->unused_hctx_lock);
 
         if (!hctx)
                 hctx = blk_mq_alloc_hctx(q, set, node);
         if (!hctx)
                 goto fail;
 
         if (blk_mq_init_hctx(q, set, hctx, hctx_idx))
                 goto free_hctx;
 
         return hctx;
 
  free_hctx:
         kobject_put(&hctx->kobj);
  fail:
         return NULL;
 }
 
 static void blk_mq_realloc_hw_ctxs(struct blk_mq_tag_set *set,
                                                 struct request_queue *q)
 {
         int i, j, end;
         struct blk_mq_hw_ctx **hctxs = q->queue_hw_ctx;
 
         if (q->nr_hw_queues < set->nr_hw_queues) {
                 struct blk_mq_hw_ctx **new_hctxs;
 
                 new_hctxs = kcalloc_node(set->nr_hw_queues,
                                        sizeof(*new_hctxs), GFP_KERNEL,
                                        set->numa_node);
                 if (!new_hctxs)
                         return;
                 if (hctxs)
                         memcpy(new_hctxs, hctxs, q->nr_hw_queues *
                                sizeof(*hctxs));
                 q->queue_hw_ctx = new_hctxs;
                 kfree(hctxs);
                 hctxs = new_hctxs;
         }
 
         /* protect against switching io scheduler  */
         mutex_lock(&q->sysfs_lock);
         for (i = 0; i < set->nr_hw_queues; i++) {
                 int node;
                 struct blk_mq_hw_ctx *hctx;
 
                 node = blk_mq_hw_queue_to_node(&set->map[HCTX_TYPE_DEFAULT], i);
                 /*
                  * If the hw queue has been mapped to another numa node,
                  * we need to realloc the hctx. If allocation fails, fallback
                  * to use the previous one.
                  */
                 if (hctxs[i] && (hctxs[i]->numa_node == node))
                         continue;
 
                 hctx = blk_mq_alloc_and_init_hctx(set, q, i, node);
                 if (hctx) {
                         if (hctxs[i])
                                 blk_mq_exit_hctx(q, set, hctxs[i], i);
                         hctxs[i] = hctx;
                 } else {
                         if (hctxs[i])
                                 pr_warn("Allocate new hctx on node %d fails,\
                                                 fallback to previous one on node %d\n",
                                                 node, hctxs[i]->numa_node);
                         else
                                 break;
                 }
         }
         /*
          * Increasing nr_hw_queues fails. Free the newly allocated
          * hctxs and keep the previous q->nr_hw_queues.
          */
         if (i != set->nr_hw_queues) {
                 j = q->nr_hw_queues;
                 end = i;
         } else {
                 j = i;
                 end = q->nr_hw_queues;
                 q->nr_hw_queues = set->nr_hw_queues;
         }
 
         for (; j < end; j++) {
                 struct blk_mq_hw_ctx *hctx = hctxs[j];
 
                 if (hctx) {
                         if (hctx->tags)
                                 blk_mq_free_map_and_requests(set, j);
                         blk_mq_exit_hctx(q, set, hctx, j);
                         hctxs[j] = NULL;
                 }
         }
         mutex_unlock(&q->sysfs_lock);
 }
 
 struct request_queue *blk_mq_init_allocated_queue(struct blk_mq_tag_set *set,
                                                   struct request_queue *q,
                                                   bool elevator_init)
 {
         /* mark the queue as mq asap */
         q->mq_ops = set->ops;
 
         q->poll_cb = blk_stat_alloc_callback(blk_mq_poll_stats_fn,
                                              blk_mq_poll_stats_bkt,
                                              BLK_MQ_POLL_STATS_BKTS, q);
         if (!q->poll_cb)
                 goto err_exit;
 
         if (blk_mq_alloc_ctxs(q))
                 goto err_poll;
 
         /* init q->mq_kobj and sw queues' kobjects */
         blk_mq_sysfs_init(q);
 
         INIT_LIST_HEAD(&q->unused_hctx_list);
         spin_lock_init(&q->unused_hctx_lock);
 
         blk_mq_realloc_hw_ctxs(set, q);
         if (!q->nr_hw_queues)
                 goto err_hctxs;
 
         INIT_WORK(&q->timeout_work, blk_mq_timeout_work);
         blk_queue_rq_timeout(q, set->timeout ? set->timeout : 30 * HZ);
 
         q->tag_set = set;
 
         q->queue_flags |= QUEUE_FLAG_MQ_DEFAULT;
         if (set->nr_maps > HCTX_TYPE_POLL &&
             set->map[HCTX_TYPE_POLL].nr_queues)
                 blk_queue_flag_set(QUEUE_FLAG_POLL, q);
 
         q->sg_reserved_size = INT_MAX;
 
         INIT_DELAYED_WORK(&q->requeue_work, blk_mq_requeue_work);
         INIT_LIST_HEAD(&q->requeue_list);
         spin_lock_init(&q->requeue_lock);
 
         blk_queue_make_request(q, blk_mq_make_request);
 
         /*
          * Do this after blk_queue_make_request() overrides it...
          */
         q->nr_requests = set->queue_depth;
 
         /*
          * Default to classic polling
          */
         q->poll_nsec = BLK_MQ_POLL_CLASSIC;
 
         blk_mq_init_cpu_queues(q, set->nr_hw_queues);
         blk_mq_add_queue_tag_set(set, q);
         blk_mq_map_swqueue(q);
 
         if (elevator_init)
                 elevator_init_mq(q);
 
         return q;
 
 err_hctxs:
         kfree(q->queue_hw_ctx);
         q->nr_hw_queues = 0;
         blk_mq_sysfs_deinit(q);
 err_poll:
         blk_stat_free_callback(q->poll_cb);
         q->poll_cb = NULL;
 err_exit:
         q->mq_ops = NULL;
         return ERR_PTR(-ENOMEM);
 }
 EXPORT_SYMBOL(blk_mq_init_allocated_queue);
 
 /* tags can _not_ be used after returning from blk_mq_exit_queue */
 void blk_mq_exit_queue(struct request_queue *q)
 {
         struct blk_mq_tag_set   *set = q->tag_set;
 
         blk_mq_del_queue_tag_set(q);
         blk_mq_exit_hw_queues(q, set, set->nr_hw_queues);
 }
 
 static int __blk_mq_alloc_rq_maps(struct blk_mq_tag_set *set)
 {
         int i;
 
         for (i = 0; i < set->nr_hw_queues; i++)
                 if (!__blk_mq_alloc_rq_map(set, i))
                         goto out_unwind;
 
         return 0;
 
 out_unwind:
         while (--i >= 0)
                 blk_mq_free_rq_map(set->tags[i]);
 
         return -ENOMEM;
 }
 
 /*
  * Allocate the request maps associated with this tag_set. Note that this
  * may reduce the depth asked for, if memory is tight. set->queue_depth
  * will be updated to reflect the allocated depth.
  */
 static int blk_mq_alloc_rq_maps(struct blk_mq_tag_set *set)
 {
         unsigned int depth;
         int err;
 
         depth = set->queue_depth;
         do {
                 err = __blk_mq_alloc_rq_maps(set);
                 if (!err)
                         break;
 
                 set->queue_depth >>= 1;
                 if (set->queue_depth < set->reserved_tags + BLK_MQ_TAG_MIN) {
                         err = -ENOMEM;
                         break;
                 }
         } while (set->queue_depth);
 
         if (!set->queue_depth || err) {
                 pr_err("blk-mq: failed to allocate request map\n");
                 return -ENOMEM;
         }
 
         if (depth != set->queue_depth)
                 pr_info("blk-mq: reduced tag depth (%u -> %u)\n",
                                                 depth, set->queue_depth);
 
         return 0;
 }
 
 static int blk_mq_update_queue_map(struct blk_mq_tag_set *set)
 {
         /*
          * blk_mq_map_queues() and multiple .map_queues() implementations
          * expect that set->map[HCTX_TYPE_DEFAULT].nr_queues is set to the
          * number of hardware queues.
          */
         if (set->nr_maps == 1)
                 set->map[HCTX_TYPE_DEFAULT].nr_queues = set->nr_hw_queues;
 
         if (set->ops->map_queues && !is_kdump_kernel()) {
                 int i;
 
                 /*
                  * transport .map_queues is usually done in the following
                  * way:
                  *
                  * for (queue = 0; queue < set->nr_hw_queues; queue++) {
                  *      mask = get_cpu_mask(queue)
                  *      for_each_cpu(cpu, mask)
                  *              set->map[x].mq_map[cpu] = queue;
                  * }
                  *
                  * When we need to remap, the table has to be cleared for
                  * killing stale mapping since one CPU may not be mapped
                  * to any hw queue.
                  */
                 for (i = 0; i < set->nr_maps; i++)
                         blk_mq_clear_mq_map(&set->map[i]);
 
                 return set->ops->map_queues(set);
         } else {
                 BUG_ON(set->nr_maps > 1);
                 return blk_mq_map_queues(&set->map[HCTX_TYPE_DEFAULT]);
         }
 }
 
 static int blk_mq_realloc_tag_set_tags(struct blk_mq_tag_set *set,
                                   int cur_nr_hw_queues, int new_nr_hw_queues)
 {
         struct blk_mq_tags **new_tags;
 
         if (cur_nr_hw_queues >= new_nr_hw_queues)
                 return 0;
 
         new_tags = kcalloc_node(new_nr_hw_queues, sizeof(struct blk_mq_tags *),
                                 GFP_KERNEL, set->numa_node);
         if (!new_tags)
                 return -ENOMEM;
 
         if (set->tags)
                 memcpy(new_tags, set->tags, cur_nr_hw_queues *
                        sizeof(*set->tags));
         kfree(set->tags);
         set->tags = new_tags;
         set->nr_hw_queues = new_nr_hw_queues;
 
         return 0;
 }
 
 /*
  * Alloc a tag set to be associated with one or more request queues.
  * May fail with EINVAL for various error conditions. May adjust the
  * requested depth down, if it's too large. In that case, the set
  * value will be stored in set->queue_depth.
  */
 int blk_mq_alloc_tag_set(struct blk_mq_tag_set *set)
 {
         int i, ret;
 
         BUILD_BUG_ON(BLK_MQ_MAX_DEPTH > 1 << BLK_MQ_UNIQUE_TAG_BITS);
 
         if (!set->nr_hw_queues)
                 return -EINVAL;
         if (!set->queue_depth)
                 return -EINVAL;
         if (set->queue_depth < set->reserved_tags + BLK_MQ_TAG_MIN)
                 return -EINVAL;
 
         if (!set->ops->queue_rq)
                 return -EINVAL;
 
         if (!set->ops->get_budget ^ !set->ops->put_budget)
                 return -EINVAL;
 
         if (set->queue_depth > BLK_MQ_MAX_DEPTH) {
                 pr_info("blk-mq: reduced tag depth to %u\n",
                         BLK_MQ_MAX_DEPTH);
                 set->queue_depth = BLK_MQ_MAX_DEPTH;
         }
 
         if (!set->nr_maps)
                 set->nr_maps = 1;
         else if (set->nr_maps > HCTX_MAX_TYPES)
                 return -EINVAL;
 
         /*
          * If a crashdump is active, then we are potentially in a very
          * memory constrained environment. Limit us to 1 queue and
          * 64 tags to prevent using too much memory.
          */
         if (is_kdump_kernel()) {
                 set->nr_hw_queues = 1;
                 set->nr_maps = 1;
                 set->queue_depth = min(64U, set->queue_depth);
         }
         /*
          * There is no use for more h/w queues than cpus if we just have
          * a single map
          */
         if (set->nr_maps == 1 && set->nr_hw_queues > nr_cpu_ids)
                 set->nr_hw_queues = nr_cpu_ids;
 
         if (blk_mq_realloc_tag_set_tags(set, 0, set->nr_hw_queues) < 0)
                 return -ENOMEM;
 
         ret = -ENOMEM;
         for (i = 0; i < set->nr_maps; i++) {
                 set->map[i].mq_map = kcalloc_node(nr_cpu_ids,
                                                   sizeof(set->map[i].mq_map[0]),
                                                   GFP_KERNEL, set->numa_node);
                 if (!set->map[i].mq_map)
                         goto out_free_mq_map;
                 set->map[i].nr_queues = is_kdump_kernel() ? 1 : set->nr_hw_queues;
         }
 
         ret = blk_mq_update_queue_map(set);
         if (ret)
                 goto out_free_mq_map;
 
         ret = blk_mq_alloc_rq_maps(set);
         if (ret)
                 goto out_free_mq_map;
 
         mutex_init(&set->tag_list_lock);
         INIT_LIST_HEAD(&set->tag_list);
 
         return 0;
 
 out_free_mq_map:
         for (i = 0; i < set->nr_maps; i++) {
                 kfree(set->map[i].mq_map);
                 set->map[i].mq_map = NULL;
         }
         kfree(set->tags);
         set->tags = NULL;
         return ret;
 }
 EXPORT_SYMBOL(blk_mq_alloc_tag_set);
 
 void blk_mq_free_tag_set(struct blk_mq_tag_set *set)
 {
         int i, j;
 
         for (i = 0; i < set->nr_hw_queues; i++)
                 blk_mq_free_map_and_requests(set, i);
 
         for (j = 0; j < set->nr_maps; j++) {
                 kfree(set->map[j].mq_map);
                 set->map[j].mq_map = NULL;
         }
 
         kfree(set->tags);
         set->tags = NULL;
 }
 EXPORT_SYMBOL(blk_mq_free_tag_set);
 
 int blk_mq_update_nr_requests(struct request_queue *q, unsigned int nr)
 {
         struct blk_mq_tag_set *set = q->tag_set;
         struct blk_mq_hw_ctx *hctx;
         int i, ret;
 
         if (!set)
                 return -EINVAL;
 
         if (q->nr_requests == nr)
                 return 0;
 
         blk_mq_freeze_queue(q);
         blk_mq_quiesce_queue(q);
 
         ret = 0;
         queue_for_each_hw_ctx(q, hctx, i) {
                 if (!hctx->tags)
                         continue;
                 /*
                  * If we're using an MQ scheduler, just update the scheduler
                  * queue depth. This is similar to what the old code would do.
                  */
                 if (!hctx->sched_tags) {
                         ret = blk_mq_tag_update_depth(hctx, &hctx->tags, nr,
                                                         false);
                 } else {
                         ret = blk_mq_tag_update_depth(hctx, &hctx->sched_tags,
                                                         nr, true);
                 }
                 if (ret)
                         break;
                 if (q->elevator && q->elevator->type->ops.depth_updated)
                         q->elevator->type->ops.depth_updated(hctx);
         }
 
         if (!ret)
                 q->nr_requests = nr;
 
         blk_mq_unquiesce_queue(q);
         blk_mq_unfreeze_queue(q);
 
         return ret;
 }
 
 /*
  * request_queue and elevator_type pair.
  * It is just used by __blk_mq_update_nr_hw_queues to cache
  * the elevator_type associated with a request_queue.
  */
 struct blk_mq_qe_pair {
         struct list_head node;
         struct request_queue *q;
         struct elevator_type *type;
 };
 
 /*
  * Cache the elevator_type in qe pair list and switch the
  * io scheduler to 'none'
  */
 static bool blk_mq_elv_switch_none(struct list_head *head,
                 struct request_queue *q)
 {
         struct blk_mq_qe_pair *qe;
 
         if (!q->elevator)
                 return true;
 
         qe = kmalloc(sizeof(*qe), GFP_NOIO | __GFP_NOWARN | __GFP_NORETRY);
         if (!qe)
                 return false;
 
         INIT_LIST_HEAD(&qe->node);
         qe->q = q;
         qe->type = q->elevator->type;
         list_add(&qe->node, head);
 
         mutex_lock(&q->sysfs_lock);
         /*
          * After elevator_switch_mq, the previous elevator_queue will be
          * released by elevator_release. The reference of the io scheduler
          * module get by elevator_get will also be put. So we need to get
          * a reference of the io scheduler module here to prevent it to be
          * removed.
          */
         __module_get(qe->type->elevator_owner);
         elevator_switch_mq(q, NULL);
         mutex_unlock(&q->sysfs_lock);
 
         return true;
 }
 
 static void blk_mq_elv_switch_back(struct list_head *head,
                 struct request_queue *q)
 {
         struct blk_mq_qe_pair *qe;
         struct elevator_type *t = NULL;
 
         list_for_each_entry(qe, head, node)
                 if (qe->q == q) {
                         t = qe->type;
                         break;
                 }
 
         if (!t)
                 return;
 
         list_del(&qe->node);
         kfree(qe);
 
         mutex_lock(&q->sysfs_lock);
         elevator_switch_mq(q, t);
         mutex_unlock(&q->sysfs_lock);
 }
 
 static void __blk_mq_update_nr_hw_queues(struct blk_mq_tag_set *set,
                                                         int nr_hw_queues)
 {
         struct request_queue *q;
         LIST_HEAD(head);
         int prev_nr_hw_queues;
 
         lockdep_assert_held(&set->tag_list_lock);
 
         if (set->nr_maps == 1 && nr_hw_queues > nr_cpu_ids)
                 nr_hw_queues = nr_cpu_ids;
         if (nr_hw_queues < 1 || nr_hw_queues == set->nr_hw_queues)
                 return;
 
         list_for_each_entry(q, &set->tag_list, tag_set_list)
                 blk_mq_freeze_queue(q);
         /*
          * Switch IO scheduler to 'none', cleaning up the data associated
          * with the previous scheduler. We will switch back once we are done
          * updating the new sw to hw queue mappings.
          */
         list_for_each_entry(q, &set->tag_list, tag_set_list)
                 if (!blk_mq_elv_switch_none(&head, q))
                         goto switch_back;
 
         list_for_each_entry(q, &set->tag_list, tag_set_list) {
                 blk_mq_debugfs_unregister_hctxs(q);
                 blk_mq_sysfs_unregister(q);
         }
 
         if (blk_mq_realloc_tag_set_tags(set, set->nr_hw_queues, nr_hw_queues) <
             0)
                 goto reregister;
 
         prev_nr_hw_queues = set->nr_hw_queues;
         set->nr_hw_queues = nr_hw_queues;
         blk_mq_update_queue_map(set);
 fallback:
         list_for_each_entry(q, &set->tag_list, tag_set_list) {
                 blk_mq_realloc_hw_ctxs(set, q);
                 if (q->nr_hw_queues != set->nr_hw_queues) {
                         pr_warn("Increasing nr_hw_queues to %d fails, fallback to %d\n",
                                         nr_hw_queues, prev_nr_hw_queues);
                         set->nr_hw_queues = prev_nr_hw_queues;
                         blk_mq_map_queues(&set->map[HCTX_TYPE_DEFAULT]);
                         goto fallback;
                 }
                 blk_mq_map_swqueue(q);
         }
 
 reregister:
         list_for_each_entry(q, &set->tag_list, tag_set_list) {
                 blk_mq_sysfs_register(q);
                 blk_mq_debugfs_register_hctxs(q);
         }
 
 switch_back:
         list_for_each_entry(q, &set->tag_list, tag_set_list)
                 blk_mq_elv_switch_back(&head, q);
 
         list_for_each_entry(q, &set->tag_list, tag_set_list)
                 blk_mq_unfreeze_queue(q);
 }
 
 void blk_mq_update_nr_hw_queues(struct blk_mq_tag_set *set, int nr_hw_queues)
 {
         mutex_lock(&set->tag_list_lock);
         __blk_mq_update_nr_hw_queues(set, nr_hw_queues);
         mutex_unlock(&set->tag_list_lock);
 }
 EXPORT_SYMBOL_GPL(blk_mq_update_nr_hw_queues);
 
 /* Enable polling stats and return whether they were already enabled. */
 static bool blk_poll_stats_enable(struct request_queue *q)
 {
         if (test_bit(QUEUE_FLAG_POLL_STATS, &q->queue_flags) ||
             blk_queue_flag_test_and_set(QUEUE_FLAG_POLL_STATS, q))
                 return true;
         blk_stat_add_callback(q, q->poll_cb);
         return false;
 }
 
 static void blk_mq_poll_stats_start(struct request_queue *q)
 {
         /*
          * We don't arm the callback if polling stats are not enabled or the
          * callback is already active.
          */
         if (!test_bit(QUEUE_FLAG_POLL_STATS, &q->queue_flags) ||
             blk_stat_is_active(q->poll_cb))
                 return;
 
         blk_stat_activate_msecs(q->poll_cb, 100);
 }
 
 static void blk_mq_poll_stats_fn(struct blk_stat_callback *cb)
 {
         struct request_queue *q = cb->data;
         int bucket;
 
         for (bucket = 0; bucket < BLK_MQ_POLL_STATS_BKTS; bucket++) {
                 if (cb->stat[bucket].nr_samples)
                         q->poll_stat[bucket] = cb->stat[bucket];
         }
 }
 
 static unsigned long blk_mq_poll_nsecs(struct request_queue *q,
                                        struct blk_mq_hw_ctx *hctx,
                                        struct request *rq)
 {
         unsigned long ret = 0;
         int bucket;
 
         /*
          * If stats collection isn't on, don't sleep but turn it on for
          * future users
          */
         if (!blk_poll_stats_enable(q))
                 return 0;
 
         /*
          * As an optimistic guess, use half of the mean service time
          * for this type of request. We can (and should) make this smarter.
          * For instance, if the completion latencies are tight, we can
          * get closer than just half the mean. This is especially
          * important on devices where the completion latencies are longer
          * than ~10 usec. We do use the stats for the relevant IO size
          * if available which does lead to better estimates.
          */
         bucket = blk_mq_poll_stats_bkt(rq);
         if (bucket < 0)
                 return ret;
 
         if (q->poll_stat[bucket].nr_samples)
                 ret = (q->poll_stat[bucket].mean + 1) / 2;
 
         return ret;
 }
 
 static bool blk_mq_poll_hybrid_sleep(struct request_queue *q,
                                      struct blk_mq_hw_ctx *hctx,
                                      struct request *rq)
 {
         struct hrtimer_sleeper hs;
         enum hrtimer_mode mode;
         unsigned int nsecs;
         ktime_t kt;
 
         if (rq->rq_flags & RQF_MQ_POLL_SLEPT)
                 return false;
 
         /*
          * If we get here, hybrid polling is enabled. Hence poll_nsec can be:
          *
          *  0:  use half of prev avg
          * >0:  use this specific value
          */
         if (q->poll_nsec > 0)
                 nsecs = q->poll_nsec;
         else
                 nsecs = blk_mq_poll_nsecs(q, hctx, rq);
 
         if (!nsecs)
                 return false;
 
         rq->rq_flags |= RQF_MQ_POLL_SLEPT;
 
         /*
          * This will be replaced with the stats tracking code, using
          * 'avg_completion_time / 2' as the pre-sleep target.
          */
         kt = nsecs;
 
         mode = HRTIMER_MODE_REL;
         hrtimer_init_sleeper_on_stack(&hs, CLOCK_MONOTONIC, mode);
         hrtimer_set_expires(&hs.timer, kt);
 
         do {
                 if (blk_mq_rq_state(rq) == MQ_RQ_COMPLETE)
                         break;
                 set_current_state(TASK_UNINTERRUPTIBLE);
                 hrtimer_sleeper_start_expires(&hs, mode);
                 if (hs.task)
                         io_schedule();
                 hrtimer_cancel(&hs.timer);
                 mode = HRTIMER_MODE_ABS;
         } while (hs.task && !signal_pending(current));
 
         __set_current_state(TASK_RUNNING);
         destroy_hrtimer_on_stack(&hs.timer);
         return true;
 }
 
 static bool blk_mq_poll_hybrid(struct request_queue *q,
                                struct blk_mq_hw_ctx *hctx, blk_qc_t cookie)
 {
         struct request *rq;
 
         if (q->poll_nsec == BLK_MQ_POLL_CLASSIC)
                 return false;
 
         if (!blk_qc_t_is_internal(cookie))
                 rq = blk_mq_tag_to_rq(hctx->tags, blk_qc_t_to_tag(cookie));
         else {
                 rq = blk_mq_tag_to_rq(hctx->sched_tags, blk_qc_t_to_tag(cookie));
                 /*
                  * With scheduling, if the request has completed, we'll
                  * get a NULL return here, as we clear the sched tag when
                  * that happens. The request still remains valid, like always,
                  * so we should be safe with just the NULL check.
                  */
                 if (!rq)
                         return false;
         }
 
         return blk_mq_poll_hybrid_sleep(q, hctx, rq);
 }
 
 /**
  * blk_poll - poll for IO completions
  * @q:  the queue
  * @cookie: cookie passed back at IO submission time
  * @spin: whether to spin for completions
  *
  * Description:
  *    Poll for completions on the passed in queue. Returns number of
  *    completed entries found. If @spin is true, then blk_poll will continue
  *    looping until at least one completion is found, unless the task is
  *    otherwise marked running (or we need to reschedule).
  */
 int blk_poll(struct request_queue *q, blk_qc_t cookie, bool spin)
 {
         struct blk_mq_hw_ctx *hctx;
         long state;
 
         if (!blk_qc_t_valid(cookie) ||
             !test_bit(QUEUE_FLAG_POLL, &q->queue_flags))
                 return 0;
 
         if (current->plug)
                 blk_flush_plug_list(current->plug, false);
 
         hctx = q->queue_hw_ctx[blk_qc_t_to_queue_num(cookie)];
 
         /*
          * If we sleep, have the caller restart the poll loop to reset
          * the state. Like for the other success return cases, the
          * caller is responsible for checking if the IO completed. If
          * the IO isn't complete, we'll get called again and will go
          * straight to the busy poll loop.
          */
         if (blk_mq_poll_hybrid(q, hctx, cookie))
                 return 1;
 
         hctx->poll_considered++;
 
         state = current->state;
         do {
                 int ret;
 
                 hctx->poll_invoked++;
 
                 ret = q->mq_ops->poll(hctx);
                 if (ret > 0) {
                         hctx->poll_success++;
                         __set_current_state(TASK_RUNNING);
                         return ret;
                 }
 
                 if (signal_pending_state(state, current))
                         __set_current_state(TASK_RUNNING);
 
                 if (current->state == TASK_RUNNING)
                         return 1;
                 if (ret < 0 || !spin)
                         break;
                 cpu_relax();
         } while (!need_resched());
 
         __set_current_state(TASK_RUNNING);
         return 0;
 }
 EXPORT_SYMBOL_GPL(blk_poll);
 
 unsigned int blk_mq_rq_cpu(struct request *rq)
 {
         return rq->mq_ctx->cpu;
 }
 EXPORT_SYMBOL(blk_mq_rq_cpu);
 
 static int __init blk_mq_init(void)
 {
         cpuhp_setup_state_multi(CPUHP_BLK_MQ_DEAD, "block/mq:dead", NULL,
                                 blk_mq_hctx_notify_dead);
         return 0;
 }
 subsys_initcall(blk_mq_init);