• ret_from_fork
  • kthread
    • worker_thread
      • process_one_work
        • blk_mq_requeue_work
          • blk_mq_run_hw_queues
            • blk_mq_run_hw_queue
              • blk_mq_sched_dispatch_requests
                • __blk_mq_sched_dispatch_requests
                  • blk_mq_dispatch_rq_list
                    • virtio_queue_rq
• vfs_fsync
  • ext4_sync_file
    • file_write_and_wait_range
      • __filemap_fdatawrite_range
        • filemap_fdatawrite_wbc
          • filemap_fdatawrite_wbc
            • do_writepages
              • ext4_writepages
                • ext4_do_writepages
                  • blk_finish_plug
                    • blk_finish_plug
                      • __blk_flush_plug
                        • blk_mq_flush_plug_list
                          • __blk_mq_flush_plug_list
                            • __blk_mq_flush_plug_list
                              • virtio_queue_rqs

                                flush

blk_mq_kick_requeue_list 总是如下的路径:

• journal_submit_commit_record
  • submit_bh
    • submit_bh_wbc
      • submit_bio_noacct
        • submit_bio_noacct_nocheck
          • __submit_bio_noacct_mq
            • blk_mq_submit_bio
              • blk_insert_flush
                • blk_kick_flush
                  • blk_mq_kick_requeue_list

freeze

例如，如果想要删除一个盘，最后会因为 ref count 不为 0

echo 1 > /sys/block/sda/device/delete

➜  nvme0n1 cat /proc/4837/stack
[<0>] blk_mq_freeze_queue_wait+0x96/0xd0
[<0>] del_gendisk+0x257/0x390
[<0>] sd_remove+0x2f/0x60
[<0>] device_release_driver_internal+0x19f/0x200
[<0>] bus_remove_device+0xc4/0x100
[<0>] device_del+0x15c/0x490
[<0>] __scsi_remove_device+0x12a/0x180
[<0>] sdev_store_delete+0x6a/0xd0
[<0>] kernfs_fop_write_iter+0x10c/0x1f0
[<0>] vfs_write+0x24a/0x440
[<0>] ksys_write+0x6f/0xf0
[<0>] do_syscall_64+0x3b/0x90
[<0>] entry_SYSCALL_64_after_hwframe+0x6e/0xd8

• ret_from_fork
  • kernel_init
    • kernel_init_freeable
      • do_basic_setup
        • do_initcalls
          • do_initcall_level
            • do_one_initcall
              • loop_init
                • loop_add
                  • __blk_mq_alloc_disk
                    • __alloc_disk_node
                      • blkcg_init_disk
                        • blk_ioprio_init
                          • blkcg_activate_policy
                            • blk_mq_freeze_queue

init

• nvme_alloc_admin_tag_set
  • blk_mq_init_queue
    • blk_mq_init_queue_data
      • blk_mq_init_allocated_queue 来分配的
        • INIT_WORK(&q->timeout_work, blk_mq_timeout_work);
        • INIT_DELAYED_WORK(&q->requeue_work, blk_mq_requeue_work);

blk_mq_dispatch_rq_list

和 __blk_mq_issue_directly 是唯二调用 blk_mq_ops::queue_rq 的地方

blk_mq_dispatch_rq_list 是来自于 scheduler 的

@[
    blk_mq_dispatch_rq_list+5
    __blk_mq_sched_dispatch_requests+301
    blk_mq_sched_dispatch_requests+57
    __blk_mq_run_hw_queue+115
    process_one_work+482
    worker_thread+84
    kthread+218
    ret_from_fork+41
]: 57
@[
    blk_mq_dispatch_rq_list+5
    __blk_mq_sched_dispatch_requests+171
    blk_mq_sched_dispatch_requests+57
    __blk_mq_run_hw_queue+115
    blk_mq_run_hw_queues+105
    blk_mq_requeue_work+340
    process_one_work+482
    worker_thread+84
    kthread+218
    ret_from_fork+41
]: 92

有趣的路径，当 echo check > /sys/block/md2/md/sync_action 的时候产生的

  virtio_queue_rq
  blk_mq_request_issue_directly
  blk_mq_try_issue_list_directly
  blk_mq_flush_plug_list
  blk_add_rq_to_plug
  blk_mq_submit_bio
  submit_bio_noacct_nocheck
  raid1_sync_request
  md_do_sync
  md_thread
  kthread
  ret_from_fork
  ret_from_fork_asm
    406

  virtio_queue_rq
  blk_mq_dispatch_rq_list
  __blk_mq_sched_dispatch_requests
  blk_mq_sched_dispatch_requests
  blk_mq_run_work_fn
  process_scheduled_works
  worker_thread
  kthread
  ret_from_fork
  ret_from_fork_asm
    109222

获取 tags

• block_read_full_folio
  • submit_bh
    • submit_bio_noacct_nocheck
      • __submit_bio_noacct_mq
        • __submit_bio
          • blk_mq_submit_bio
            • blk_mq_get_new_requests
              • __blk_mq_alloc_requests
                • blk_mq_get_tag
                  • __blk_mq_get_tag
                    • __sbitmap_queue_get
                      • sbitmap_get
                        • __sbitmap_get
                          • sbitmap_find_bit
                            • sbitmap_find_bit_in_word
                              • __sbitmap_get_word

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