RBD schedules the request completion code (qemu_rbd_finish_bh()) to run in the BDS's AioContext. The intent seems to be to run it in the same context that the original request coroutine ran in, i.e. the thread on whose stack the RBDTask object exists (see qemu_rbd_start_co()).
However, with multiqueue, that thread is not necessarily the same as the BDS's AioContext. Instead, we need to remember the actual AioContext and schedule the completion BH there. Buglink: https://issues.redhat.com/browse/RHEL-67115 Reported-by: Junyao Zhao <junz...@redhat.com> Signed-off-by: Hanna Czenczek <hre...@redhat.com> --- I think I could also drop RBDTask.ctx and just use `qemu_coroutine_get_aio_context(RBDTask.co)` instead, but this is the version of the patch that was tested and confirmed to fix the issue (I don't have a local reproducer), so I thought I'll post this first. --- block/rbd.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) diff --git a/block/rbd.c b/block/rbd.c index af984fb7db..9d4e0817e0 100644 --- a/block/rbd.c +++ b/block/rbd.c @@ -102,7 +102,7 @@ typedef struct BDRVRBDState { } BDRVRBDState; typedef struct RBDTask { - BlockDriverState *bs; + AioContext *ctx; Coroutine *co; bool complete; int64_t ret; @@ -1269,8 +1269,7 @@ static void qemu_rbd_completion_cb(rbd_completion_t c, RBDTask *task) { task->ret = rbd_aio_get_return_value(c); rbd_aio_release(c); - aio_bh_schedule_oneshot(bdrv_get_aio_context(task->bs), - qemu_rbd_finish_bh, task); + aio_bh_schedule_oneshot(task->ctx, qemu_rbd_finish_bh, task); } static int coroutine_fn qemu_rbd_start_co(BlockDriverState *bs, @@ -1281,7 +1280,10 @@ static int coroutine_fn qemu_rbd_start_co(BlockDriverState *bs, RBDAIOCmd cmd) { BDRVRBDState *s = bs->opaque; - RBDTask task = { .bs = bs, .co = qemu_coroutine_self() }; + RBDTask task = { + .ctx = qemu_get_current_aio_context(), + .co = qemu_coroutine_self(), + }; rbd_completion_t c; int r; -- 2.48.1
