Re: [Libguestfs] [libnbd PATCH] opt_go: Tolerate unplanned server death

While debugging some experimental nbdkit code that was triggering an assertion failure in nbdkit, I noticed a secondary failure of nbdsh also dying from an assertion: libnbd: debug: nbdsh: nbd_opt_go: transition: NEWSTYLE.OPT_GO.SEND -> DEAD libnbd: debug: nbdsh: nbd_opt_go: option queued, ignoring state machine failure nbdsh: opt.c:86: nbd_unlocked_opt_go: Assertion `nbd_internal_is_state_negotiating (get_next_state (h))' failed. Although my trigger was from non-production nbdkit code, libnbd should never die from an assertion failure merely because a server disappeared at the wrong moment during an incomplete reply to NBD_OPT_GO or NBD_OPT_INFO. Fixes: bbf1c51392 (api: Give aio_opt_go a completion callback) --- lib/opt.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/lib/opt.c b/lib/opt.c index 2317b72..e5802f4 100644 --- a/lib/opt.c +++ b/lib/opt.c @@ -1,5 +1,5 @@ /* NBD client library in userspace - * Copyright (C) 2020 Red Hat Inc. + * Copyright (C) 2020-2021 Red Hat Inc. * * This library is free software; you can redistribute it and/or * modify it under the terms of the GNU Lesser General Public @@ -83,7 +83,8 @@ nbd_unlocked_opt_go (struct nbd_handle *h) r = wait_for_option (h); if (r == 0 && err) { - assert (nbd_internal_is_state_negotiating (get_next_state (h))); + assert (nbd_internal_is_state_negotiating (get_next_state (h)) || + nbd_internal_is_state_dead (get_next_state (h))); set_error (err, "server replied with error to opt_go request"); return -1; } @@ -105,7 +106,8 @@ nbd_unlocked_opt_info (struct nbd_handle *h) r = wait_for_option (h); if (r == 0 && err) { - assert (nbd_internal_is_state_negotiating (get_next_state (h))); + assert (nbd_internal_is_state_negotiating (get_next_state (h)) || + nbd_internal_is_state_dead (get_next_state (h))); set_error (err, "server replied with error to opt_info request"); return -1;