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ublk2-multishot - Coggle Diagram

- - - - one API for select buffer
        
        use existing provided buffer interface
      - another is for completing & posting CQE
      - how to trigger re-submission
      - iterator is maintained by driver
        
        is it really needed?
        
        not needed actually
  - - - it is async
        
        similar with timeout multishot
  - - - pick up the top priority one
        
        return marked fcmd
    - - continue to post CQE from other fcmd if the top one is done
    - - can't be avoided
        
        TW side lock isn't needed if there is just one inflight fcmd
        
        multi writer vs. single reader
      - kfifo supports multi-writers vs. single reader
        
        reader needn't lock
  - - - which lock
        
        quue lock
        
        fcmd lock
      - return marked fcmd
- - - - yes, it is fcmd
      - triggered during canceling
      - happened during cancel
  - - - solved
  - - - client process is saturated
        
        queue_rq() side change takes extra cpu
        
        replace kfifo with rq list?
      - kublk just takes 90%
- - - - deliver ublk io command tag to ublk server only
- - - - cancel multishot commands
      - aborting requests
      - kill ublk server process
  - - - anytime it is fetched to ublk server, one COMMIT_CMS is taken for completing this IO
        
        looks addressed naturally
        
        buffer is auto-registered
        
        in the multishot FETCH uring_cmd context
    - - buf_idx is provided beforehand
        
        every io_uring has to create one sparse buffer table which size is same with ubq_depth
        
        queue wide uniqueue buffer index has to be provided
        
        easy
- - - - ring_buf for FETCH
      - fixed buffer for COMMIT
      - per ublk-thread
    - - qid
      - buf_idx
      - op
    - - support single pthread first
      - cover two FETCH commands
        
        if inflight nr_fetch is less than 2, issue one
    - - PREP_IO_CMDS
      - COMMIT_IO_CMDS
      - FETCH_IO_CMDS