On Mon, Mar 20, 2017 at 10:26 PM, Fam Zheng <f...@redhat.com> wrote: > On Fri, 03/17 09:55, Ed Swierk wrote: >> I'm running into the same problem taking an external snapshot with a >> virtio-blk drive with iothread, so it's not specific to virtio-scsi. >> Run a Linux guest on qemu master >> >> qemu-system-x86_64 -nographic -enable-kvm -monitor >> telnet:0.0.0.0:1234,server,nowait -m 1024 -object >> iothread,id=iothread1 -drive file=/x/drive.qcow2,if=none,id=drive0 >> -device virtio-blk-pci,iothread=iothread1,drive=drive0 >> >> Then in the monitor >> >> snapshot_blkdev drive0 /x/snap1.qcow2 >> >> qemu bombs with >> >> qemu-system-x86_64: /x/qemu/include/block/aio.h:457: >> aio_enable_external: Assertion `ctx->external_disable_cnt > 0' failed. >> >> whereas without the iothread the assertion failure does not occur. > > > Can you test this one? > > --- > > > diff --git a/blockdev.c b/blockdev.c > index c5b2c2c..4c217d5 100644 > --- a/blockdev.c > +++ b/blockdev.c > @@ -1772,6 +1772,8 @@ static void external_snapshot_prepare(BlkActionState > *common, > return; > } > > + bdrv_set_aio_context(state->new_bs, state->aio_context); > + > /* This removes our old bs and adds the new bs. This is an operation that > * can fail, so we need to do it in .prepare; undoing it for abort is > * always possible. */ > @@ -1789,8 +1791,6 @@ static void external_snapshot_commit(BlkActionState > *common) > ExternalSnapshotState *state = > DO_UPCAST(ExternalSnapshotState, common, > common); > > - bdrv_set_aio_context(state->new_bs, state->aio_context); > - > /* We don't need (or want) to use the transactional > * bdrv_reopen_multiple() across all the entries at once, because we > * don't want to abort all of them if one of them fails the reopen */
With this change, a different assertion fails on running snapshot_blkdev: qemu-system-x86_64: /x/qemu/block/io.c:164: bdrv_drain_recurse: Assertion `qemu_get_current_aio_context() == qemu_get_aio_context()' failed. --Ed
