diff options
| -rw-r--r-- | block/io.c | 23 |
1 files changed, 20 insertions, 3 deletions
diff --git a/block/io.c b/block/io.c index 8706bfa578..a7142e00e8 100644 --- a/block/io.c +++ b/block/io.c @@ -158,7 +158,7 @@ bool bdrv_requests_pending(BlockDriverState *bs) static bool bdrv_drain_recurse(BlockDriverState *bs) { - BdrvChild *child; + BdrvChild *child, *tmp; bool waited; waited = BDRV_POLL_WHILE(bs, atomic_read(&bs->in_flight) > 0); @@ -167,8 +167,25 @@ static bool bdrv_drain_recurse(BlockDriverState *bs) bs->drv->bdrv_drain(bs); } - QLIST_FOREACH(child, &bs->children, next) { - waited |= bdrv_drain_recurse(child->bs); + QLIST_FOREACH_SAFE(child, &bs->children, next, tmp) { + BlockDriverState *bs = child->bs; + bool in_main_loop = + qemu_get_current_aio_context() == qemu_get_aio_context(); + assert(bs->refcnt > 0); + if (in_main_loop) { + /* In case the recursive bdrv_drain_recurse processes a + * block_job_defer_to_main_loop BH and modifies the graph, + * let's hold a reference to bs until we are done. + * + * IOThread doesn't have such a BH, and it is not safe to call + * bdrv_unref without BQL, so skip doing it there. + */ + bdrv_ref(bs); + } + waited |= bdrv_drain_recurse(bs); + if (in_main_loop) { + bdrv_unref(bs); + } } return waited; |