[PATCH 0/5] blk plug fixes

[Shaohua Li]

These are some block plug related patches. The first 3 are independent and can
apply separately.

For the multiple queue case, I only handled !BLK_MQ_F_DEFER_ISSUE case. The
DEFER_ISSUE is really confusing, I'm not sure what's the correct behavior.

BTW, calling blk_mq_merge_queue_io is confusing too to me. The request will be
dispatched immediately or offload to a workqueue to dispatch. In either case,
the request will be dispatched soon. There is a tiny window there are requests
in the queue and requests can be merged. I thought we can delete the code with
plug merge. And if out of order request merge is important, we really should
add a ELEVATOR_INSERT_SORT_MERGE like mechanism. This makes me more confusing
about BLK_MQ_F_DEFER_ISSUE too.

Thanks,
Shaohua

Jeff Moyer (1):
  blk-mq: fix plugging in blk_sq_make_request

Shaohua Li (4):
  blk: clean up plug
  sched: always use blk_schedule_flush_plug in io_schedule_out
  blk-mq: do limited block plug for multiple queue case
  blk-mq: make plug work for mutiple disks and queues

 block/blk-core.c    |  34 ++++++++-------
 block/blk-mq.c      | 120 ++++++++++++++++++++++++++++++++--------------------
 block/blk.h         |   3 +-
 kernel/sched/core.c |   8 +---
 4 files changed, 98 insertions(+), 67 deletions(-)

-- 
1.8.1

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