[Libguestfs] [libnbd PATCH 4/4] copy: Ignore extents if we encountered earlier error

In practice, the nbd extents callback will only be called once per nbd_aio_block_status, because we have only requested exactly one metacontext id, and because compliant servers send only one reply chunk per id. In theory, a server could reply first with an error chunk (perhaps meaning "I'm unable to get status beyond offset X") followed by an extent chunk ("but here's what I was able to get") while still being compliant. And a non-compliant server can send unexpected chunks, just to try and confuse us. Right now, it would take a custom NBD server to actually trigger any scenario where *error would ever be non-zero on entry to next_extent() (nbdkit does not have that much power). So while *error ever being non-zero is unlikely, our easiest course is to handle it the same way we would for a server sending us an unexpected id: ignore the rest of the extent callback. The later completion callback will handle the overall command failing. --- copy/nbd-ops.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/copy/nbd-ops.c b/copy/nbd-ops.c index dfc62f20..ab30badd 100644 --- a/copy/nbd-ops.c +++ b/copy/nbd-ops.c @@ -1,5 +1,5 @@ /* NBD client library in userspace. - * Copyright (C) 2020 Red Hat Inc. + * Copyright (C) 2020-2022 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 @@ -337,7 +337,7 @@ add_extent (void *vp, const char *metacontext, extent_list *ret = vp; size_t i; - if (strcmp (metacontext, "base:allocation") != 0) + if (strcmp (metacontext, "base:allocation") != 0 || *error) return 0; for (i = 0; i < nr_entries; i += 2) { -- 2.34.1