[Qemu-devel] [RFC PATCH 00/12] block: Protect block jobs with lock / unlock API

[Fam Zheng <famz@redhat.com>]

This is the partial work to introduce bdrv_lock / bdrv_unlock and use them in
block jobs where exclusive access to a BDS is necessary. It address the same
category of problems as [1] with a different API, as the idea proposed by Paolo
and Kevin.

What's implemented in this series is also very close to [1], i.e. pausing
ioeventfd and NBD server, with a notifier list.

The important missing pieces are converting bdrv_lock/unlock callers to
coroutine, so that they can wait in the bs->lock_queue.  In other words, this
API is not complete without that, because we can't handle the case where two
non-coroutine callers have contention, which is now asserted in bdrv_lock as
practically impossible.

[1]: https://lists.gnu.org/archive/html/qemu-block/2015-05/msg00800.html

Thanks,

Fam


Fam Zheng (12):
  block: Use bdrv_drain to replace uncessary bdrv_drain_all
  block: Introduce bdrv_lock and bdrv_unlock API
  blockdev: Lock BDS during internal snapshot transaction
  blockdev: Lock BDS during external snapshot transaction
  blockdev: Lock BDS during drive-backup transaction
  blockdev: Lock BDS during blockdev-backup transaction
  block-backend: Add blk_add_lock_unlock_notifier
  virtio-blk: Move complete_request to 'ops' structure
  virtio-blk: Don't handle output when backend is locked
  virtio-scsi-dataplane: Add backend lock listener
  nbd-server: Clear "can_read" when backend is locked
  mirror: Protect source between bdrv_drain and bdrv_swap

 block.c                         | 16 +++++++--
 block/block-backend.c           |  6 ++++
 block/io.c                      | 69 ++++++++++++++++++++++++++++++++++++
 block/mirror.c                  | 18 ++++++++--
 block/snapshot.c                |  2 +-
 blockdev.c                      | 17 +++++++--
 hw/block/dataplane/virtio-blk.c | 36 ++++++++++++++++---
 hw/block/virtio-blk.c           | 63 +++++++++++++++++++++++++++++++--
 hw/scsi/virtio-scsi-dataplane.c | 78 ++++++++++++++++++++++++++++++-----------
 hw/scsi/virtio-scsi.c           |  3 ++
 include/block/block.h           | 39 +++++++++++++++++++++
 include/block/block_int.h       |  5 +++
 include/hw/virtio/virtio-blk.h  | 17 +++++++--
 include/hw/virtio/virtio-scsi.h |  3 ++
 include/sysemu/block-backend.h  |  1 +
 migration/block.c               |  2 +-
 nbd.c                           | 21 +++++++++++
 17 files changed, 356 insertions(+), 40 deletions(-)

-- 
2.4.2