[Libguestfs] [nbdkit PATCH] server: Correct logic when filter fails .prepare

If .prepare fails, we do not want to call .finalize (similar to how if .open fails, we do not want to call .close). However, the logic in backend_finalize was checking on the wrong condition ('was the connection opened' rather than 'was the connection prepared'), which led to an assertion failure. Simple reproducer: $ nbdkit -U - -f --filter cache --run 'qemu-io -r -c quit $nbd' sh - <<\EOF nbdkit: sh[1]: error: /tmp/nbdkitshYvAQbz/inline-script.sh: oops nbdkit: backend.c:206: backend_finalize: Assertion `h->state & HANDLE_CONNECTED' failed. qemu-io: can't open device nbd:unix:/tmp/nbdkit60FUTw/socket: Failed to read option reply: Unexpected end-of-file before all bytes were read nbdkit: nbdkit command was killed by signal 6 With this patch, the command now fails gracefully: nbdkit: sh[1]: error: /tmp/nbdkitshie18Lp/inline-script.sh: oops qemu-io: can't open device nbd:unix:/tmp/nbdkitqvAOlr/socket: Requested export not available Fixes: ffa98c8d Signed-off-by: Eric Blake <eblake(a)redhat.com&gt; --- Pushing this to master and stable-1.16 server/backend.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-) diff --git a/server/backend.c b/server/backend.c index 8bfa8525..753f5cca 100644 --- a/server/backend.c +++ b/server/backend.c @@ -221,15 +221,13 @@ backend_finalize (struct backend *b) if (h->state & HANDLE_FAILED) return -1; - if (h->handle) { - assert (h->state & HANDLE_CONNECTED); + assert (h->state & HANDLE_OPEN); + if (h->state & HANDLE_CONNECTED) { if (b->finalize (b, h->handle) == -1) { h->state |= HANDLE_FAILED; return -1; } } - else - assert (! (h->state & HANDLE_CONNECTED)); if (b->i) return backend_finalize (b->next); -- 2.24.1