From: Kevin Wolf Date: Mon, 22 Jul 2019 17:44:27 +0200 Subject: mirror: Keep mirror_top_bs drained after dropping permissions Git-commit: d2da5e288a2e71e82866c8fdefd41b5727300124 mirror_top_bs is currently implicitly drained through its connection to the source or the target node. However, the drain section for target_bs ends early after moving mirror_top_bs from src to target_bs, so that requests can already be restarted while mirror_top_bs is still present in the chain, but has dropped all permissions and therefore runs into an assertion failure like this: qemu-system-x86_64: block/io.c:1634: bdrv_co_write_req_prepare: Assertion `child->perm & BLK_PERM_WRITE' failed. Keep mirror_top_bs drained until all graph changes have completed. Cc: qemu-stable@nongnu.org Signed-off-by: Kevin Wolf Reviewed-by: Max Reitz Signed-off-by: Bruce Rogers --- block/mirror.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/block/mirror.c b/block/mirror.c index 9f5c59ece1df391babc4461f63cb..642d6570cc97e1239b119a46c457 100644 --- a/block/mirror.c +++ b/block/mirror.c @@ -656,7 +656,10 @@ static int mirror_exit_common(Job *job) s->target = NULL; /* We don't access the source any more. Dropping any WRITE/RESIZE is - * required before it could become a backing file of target_bs. */ + * required before it could become a backing file of target_bs. Not having + * these permissions any more means that we can't allow any new requests on + * mirror_top_bs from now on, so keep it drained. */ + bdrv_drained_begin(mirror_top_bs); bs_opaque->stop = true; bdrv_child_refresh_perms(mirror_top_bs, mirror_top_bs->backing, &error_abort); @@ -724,6 +727,7 @@ static int mirror_exit_common(Job *job) bs_opaque->job = NULL; bdrv_drained_end(src); + bdrv_drained_end(mirror_top_bs); s->in_drain = false; bdrv_unref(mirror_top_bs); bdrv_unref(src);