The fact that the bs->aio_context is changing can confuse the dataplane iothread, because of the now fine granularity aio context lock. bdrv_drain should rather be a bdrv_drained_begin/end pair, but since bs->aio_context is changing, we can just use aio_disable_external and bdrv_parent_drained_begin.
Reported-by: Ed Swierk <eswi...@skyportsystems.com> Signed-off-by: Fam Zheng <f...@redhat.com> Acked-by: Stefan Hajnoczi <stefa...@redhat.com> Reviewed-by: Stefan Hajnoczi <stefa...@redhat.com> Reviewed-by: Kevin Wolf <kw...@redhat.com> --- block.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/block.c b/block.c index b8a3011..a995a8e 100644 --- a/block.c +++ b/block.c @@ -4396,11 +4396,12 @@ void bdrv_attach_aio_context(BlockDriverState *bs, void bdrv_set_aio_context(BlockDriverState *bs, AioContext *new_context) { - AioContext *ctx; + AioContext *ctx = bdrv_get_aio_context(bs); + aio_disable_external(ctx); + bdrv_parent_drained_begin(bs); bdrv_drain(bs); /* ensure there are no in-flight requests */ - ctx = bdrv_get_aio_context(bs); while (aio_poll(ctx, false)) { /* wait for all bottom halves to execute */ } @@ -4412,6 +4413,8 @@ void bdrv_set_aio_context(BlockDriverState *bs, AioContext *new_context) */ aio_context_acquire(new_context); bdrv_attach_aio_context(bs, new_context); + bdrv_parent_drained_end(bs); + aio_enable_external(ctx); aio_context_release(new_context); } -- 2.9.3