v2:
- Do not rely on BlockBackend request queuing, implement .drained_begin/end()
instead in xen-block, virtio-blk, and virtio-scsi [Paolo]
- Add qdev_is_realized() API [Philippe]
- Add patch to avoid AioContext lock around blk_exp_ref/unref() [Paolo]
- Add patch to call .drained_begin/end() from main loop thread to simplify
callback implementations
The aio_disable_external() API temporarily suspends file descriptor monitoring
in the event loop. The block layer uses this to prevent new I/O requests being
submitted from the guest and elsewhere between bdrv_drained_begin() and
bdrv_drained_end().
While the block layer still needs to prevent new I/O requests in drained
sections, the aio_disable_external() API can be replaced with
.drained_begin/end/poll() callbacks that have been added to BdrvChildClass and
BlockDevOps.
This newer .bdrained_begin/end/poll() approach is attractive because it works
without specifying a specific AioContext. The block layer is moving towards
multi-queue and that means multiple AioContexts may be processing I/O
simultaneously.
The aio_disable_external() was always somewhat hacky. It suspends all file
descriptors that were registered with is_external=true, even if they have
nothing to do with the BlockDriverState graph nodes that are being drained.
It's better to solve a block layer problem in the block layer than to have an
odd event loop API solution.
The approach in this patch series is to implement BlockDevOps
.drained_begin/end() callbacks that temporarily stop file descriptor handlers.
This ensures that new I/O requests are not submitted in drained sections.
The first two virtio-scsi patches were already sent as a separate series. I
included them because they are necessary in order to fully remove
aio_disable_external().
Based-on: 087bc644b7634436ca9d52fe58ba9234e2bef026 (kevin/block-next)
Stefan Hajnoczi (16):
hw/qdev: introduce qdev_is_realized() helper
virtio-scsi: avoid race between unplug and transport event
virtio-scsi: stop using aio_disable_external() during unplug
block/export: only acquire AioContext once for
vhost_user_server_stop()
util/vhost-user-server: rename refcount to in_flight counter
block/export: wait for vhost-user-blk requests when draining
block/export: stop using is_external in vhost-user-blk server
hw/xen: do not use aio_set_fd_handler(is_external=true) in
xen_xenstore
block: add blk_in_drain() API
block: drain from main loop thread in bdrv_co_yield_to_drain()
xen-block: implement BlockDevOps->drained_begin()
hw/xen: do not set is_external=true on evtchn fds
block/export: rewrite vduse-blk drain code
block/export: don't require AioContext lock around blk_exp_ref/unref()
block/fuse: do not set is_external=true on FUSE fd
virtio: make it possible to detach host notifier from any thread
hw/block/dataplane/xen-block.h | 2 +
include/block/export.h | 2 +
include/hw/qdev-core.h | 17 ++-
include/qemu/vhost-user-server.h | 8 +-
include/sysemu/block-backend-common.h | 25 ++--
include/sysemu/block-backend-global-state.h | 1 +
block/block-backend.c | 7 ++
block/export/export.c | 13 +-
block/export/fuse.c | 58 ++++++++-
block/export/vduse-blk.c | 128 ++++++++++++++------
block/export/vhost-user-blk-server.c | 73 +++++++----
block/io.c | 3 +-
hw/block/dataplane/virtio-blk.c | 2 +
hw/block/dataplane/xen-block.c | 42 +++++--
hw/block/xen-block.c | 24 +++-
hw/i386/kvm/xen_xenstore.c | 2 +-
hw/scsi/scsi-bus.c | 6 +-
hw/scsi/scsi-disk.c | 1 +
hw/scsi/virtio-scsi-dataplane.c | 9 ++
hw/scsi/virtio-scsi.c | 21 ++--
hw/xen/xen-bus.c | 11 +-
util/vhost-user-server.c | 37 +++---
22 files changed, 348 insertions(+), 144 deletions(-)
--
2.39.2