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[Qemu-devel] [RFC PATCH 3/4] virtio-blk: Use aio_set_io_event_notifier i
From: |
Fam Zheng |
Subject: |
[Qemu-devel] [RFC PATCH 3/4] virtio-blk: Use aio_set_io_event_notifier in dataplane |
Date: |
Wed, 27 May 2015 15:19:05 +0800 |
Currently the host notifier is checked by all aio_poll, which is not
safe. For example, in a qmp transaction that takes snapshots or starts
drive-backup on multiple dataplane disks, the atomicity could be broken:
There could be one or more bdrv_drain_all() calls in each transaction
opeartion, which will unconditinally calls one or more aio_poll on the
AioContext:
qmp transaction
backup A prepare
...
bdrv_drain_all()
aio_poll(A)
aio_poll(B)
aio_poll(C)
...
...
backup B prepare
...
bdrv_drain_all()
aio_poll(A)
aio_poll(B)
-> aio_poll(C)
...
snapshot C prepare
...
bdrv_drain_all()
aio_poll(A)
aio_poll(B)
aio_poll(C)
...
If the aio_poll(C) in the middle receives a new virtio-blk request from
ioeventfd, a new request will be submitted to C, then snapshot C is
inconsistent.
To avoid that, use aio_set_io_event_notifier so the behavior is the same
as in main loop.
Signed-off-by: Fam Zheng <address@hidden>
---
hw/block/dataplane/virtio-blk.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/hw/block/dataplane/virtio-blk.c b/hw/block/dataplane/virtio-blk.c
index 3db139b..027c5c5 100644
--- a/hw/block/dataplane/virtio-blk.c
+++ b/hw/block/dataplane/virtio-blk.c
@@ -283,7 +283,7 @@ void virtio_blk_data_plane_start(VirtIOBlockDataPlane *s)
/* Get this show started by hooking up our callbacks */
aio_context_acquire(s->ctx);
- aio_set_event_notifier(s->ctx, &s->host_notifier, handle_notify);
+ aio_set_io_event_notifier(s->ctx, &s->host_notifier, handle_notify);
aio_context_release(s->ctx);
return;
@@ -319,7 +319,7 @@ void virtio_blk_data_plane_stop(VirtIOBlockDataPlane *s)
aio_context_acquire(s->ctx);
/* Stop notifications for new requests from guest */
- aio_set_event_notifier(s->ctx, &s->host_notifier, NULL);
+ aio_set_io_event_notifier(s->ctx, &s->host_notifier, NULL);
/* Drain and switch bs back to the QEMU main loop */
blk_set_aio_context(s->conf->conf.blk, qemu_get_aio_context());
--
2.4.1
- [Qemu-devel] [RFC PATCH 0/4] aio: Don't poll ioeventfd in nested aio_poll(), Fam Zheng, 2015/05/27
- [Qemu-devel] [RFC PATCH 1/4] aio-posix: Introduce aio_set_io_event_notifier, Fam Zheng, 2015/05/27
- [Qemu-devel] [RFC PATCH 2/4] aio-win32: Implement aio_set_io_event_notifier, Fam Zheng, 2015/05/27
- [Qemu-devel] [RFC PATCH 3/4] virtio-blk: Use aio_set_io_event_notifier in dataplane,
Fam Zheng <=
- [Qemu-devel] [RFC PATCH 4/4] virtio-scsi-dataplane: User aio_set_io_event_notifier, Fam Zheng, 2015/05/27
- Re: [Qemu-devel] [RFC PATCH 0/4] aio: Don't poll ioeventfd in nested aio_poll(), Paolo Bonzini, 2015/05/27
- Re: [Qemu-devel] [RFC PATCH 0/4] aio: Don't poll ioeventfd in nested aio_poll(), Fam Zheng, 2015/05/27
- Re: [Qemu-devel] [RFC PATCH 0/4] aio: Don't poll ioeventfd in nested aio_poll(), Paolo Bonzini, 2015/05/28
- Re: [Qemu-devel] [RFC PATCH 0/4] aio: Don't poll ioeventfd in nested aio_poll(), Fam Zheng, 2015/05/28
- Re: [Qemu-devel] [RFC PATCH 0/4] aio: Don't poll ioeventfd in nested aio_poll(), Paolo Bonzini, 2015/05/28
- Re: [Qemu-devel] [RFC PATCH 0/4] aio: Don't poll ioeventfd in nested aio_poll(), Fam Zheng, 2015/05/28
- Re: [Qemu-devel] [RFC PATCH 0/4] aio: Don't poll ioeventfd in nested aio_poll(), Paolo Bonzini, 2015/05/28
- Re: [Qemu-devel] [RFC PATCH 0/4] aio: Don't poll ioeventfd in nested aio_poll(), Fam Zheng, 2015/05/28