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[Qemu-devel] [PATCH v2 00/11] block: allow blockjobs to coexist with dat

From: Stefan Hajnoczi
Subject: [Qemu-devel] [PATCH v2 00/11] block: allow blockjobs to coexist with dataplane
Date: Tue, 21 Oct 2014 12:03:49 +0100

 * Protect block_job_defer_to_main_loop_bh() against AioContext change [Max]
 * Drop unnecessary if (buf) around qemu_vfree(buf) [Max]

Almost all the infrastructure is in place to make blockjobs safe for use with

  * Op blockers all us to exclude commands that could conflict with a blockjob
    or dataplane.

  * AioContext acquire/release allows threads to temporarily access a
    BlockDriverState that is running in another thread.

This series introduces a few additional helpers:

  * block_job_defer_to_main_loop() which allows blockjobs to run their
    completion code in the QEMU main loop.  This is necessary because some
    operations are not safe outside the QEMU global mutex.

  * bdrv_drain() which can be used in limited cases to wait for in-flight
    requests to complete (as opposed to the global bdrv_drain_all() function).

The approach taken in this series is to convert the blockdev.c monitor command
so it acquires the BlockDriverState's AioContext.  Normally only 1 AioContext
is involved at a time but the mirror job's to_replace argument can involve a
second AioContext.

Then the block job code itself is converted to defer main loop code using


  $ qemu-system-x86_64 -enable-kvm -m 1024 \
        -drive if=none,id=drive0,file=test.img \
        -object iothread,iothread0 \
        -device virtio-blk-pci,drive=drive0,iothread=iothread0
  (qemu) drive_mirror drive0 test2.img

Stefan Hajnoczi (11):
  block: acquire AioContext in generic blockjob QMP commands
  blockdev: acquire AioContext in do_qmp_query_block_jobs_one()
  blockdev: acquire AioContext in blockdev_mark_auto_del()
  blockdev: add note that block_job_cb() must be thread-safe
  blockjob: add block_job_defer_to_main_loop()
  block: add bdrv_drain()
  block: let backup blockjob run in BDS AioContext
  block: let stream blockjob run in BDS AioContext
  block: let mirror blockjob run in BDS AioContext
  block: let commit blockjob run in BDS AioContext
  block: declare blockjobs and dataplane friends!

 block.c                         |  49 +++++++++--
 block/backup.c                  |  21 ++++-
 block/commit.c                  |  70 ++++++++++------
 block/mirror.c                  |  85 +++++++++++++------
 block/stream.c                  |  50 +++++++----
 blockdev.c                      | 179 +++++++++++++++++++++++++++++-----------
 blockjob.c                      |  46 +++++++++++
 hw/block/dataplane/virtio-blk.c |   5 ++
 include/block/block.h           |   1 +
 include/block/blockjob.h        |  19 +++++
 10 files changed, 402 insertions(+), 123 deletions(-)


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