[Libguestfs] nbdkit: cow.c:591: cow_extents: Assertion `count > 0' failed.

Just noting this because I don't have time to look into it at the moment. I suspect (but don't have any evidence for) that this might be an issue in the cacheextents filter. nbdkit-1.27.2-1.fc35.x86_64 libnbd-1.9.2-1.fc35.x86_64 nbdkit is running against a web server with this command line: nbdkit --exit-with-parent --foreground --newstyle \ --pidfile /run/user/1000/v2vnbdkit.MHmNIZ/nbdkit1.pid \ --unix /tmp/v2v.wxXvoj/in0 \ --threads 16 \ --selinux-label system_u:object_r:svirt_socket_t:s0 \ -D nbdkit.backend.datapath=0 \ --exportname / --verbose \ --filter cow \ --filter cacheextents \ --filter retry \ curl timeout=2000 \ cookie-script=/tmp/v2vcse4d3ca.sh \ cookie-script-renew=1500 \ sslverify=false \ url=https://[redacted] nbdinfo --map command failed: $ nbdinfo --map nbd+unix:///?socket=in0 nbdinfo: nbd_block_status: block-status: command failed: Transport endpoint is not connected Looking at the nbdkit log: nbdkit: debug: accepted connection nbdkit: curl[7]: debug: cow: preconnect nbdkit: curl[7]: debug: cacheextents: preconnect nbdkit: curl[7]: debug: retry: preconnect nbdkit: curl[7]: debug: curl: preconnect nbdkit: curl[7]: debug: newstyle negotiation: flags: global 0x3 nbdkit: curl[7]: debug: newstyle negotiation: client flags: 0x3 nbdkit: curl[7]: debug: newstyle negotiation: NBD_OPT_STRUCTURED_REPLY: client requested structured replies nbdkit: curl[7]: debug: newstyle negotiation: NBD_OPT_SET_META_CONTEXT: client requested export '' nbdkit: curl[7]: debug: newstyle negotiation: NBD_OPT_SET_META_CONTEXT: set count: 1 nbdkit: curl[7]: debug: newstyle negotiation: NBD_OPT_SET_META_CONTEXT: set base:allocation nbdkit: curl[7]: debug: newstyle negotiation: NBD_OPT_SET_META_CONTEXT: replying with base:allocation id 1 nbdkit: curl[7]: debug: newstyle negotiation: NBD_OPT_SET_META_CONTEXT: reply complete nbdkit: curl[7]: debug: newstyle negotiation: NBD_OPT_GO: client requested export '' nbdkit: curl[7]: debug: cow: open readonly=0 exportname="" tls=0 nbdkit: curl[7]: debug: cow: default_export readonly=0 tls=0 nbdkit: curl[7]: debug: cacheextents: default_export readonly=0 tls=0 nbdkit: curl[7]: debug: retry: default_export readonly=0 tls=0 nbdkit: curl[7]: debug: curl: default_export readonly=0 tls=0 nbdkit: curl[7]: debug: cacheextents: open readonly=1 exportname="" tls=0 nbdkit: curl[7]: debug: cacheextents: default_export readonly=1 tls=0 nbdkit: curl[7]: debug: retry: open readonly=1 exportname="" tls=0 nbdkit: curl[7]: debug: retry: default_export readonly=1 tls=0 nbdkit: curl[7]: debug: curl: open readonly=1 exportname="" tls=0 nbdkit: curl[7]: debug: curl: default_export readonly=1 tls=0 nbdkit: curl[7]: debug: content length: 12884901888 nbdkit: curl[7]: debug: accept range supported (for HTTP/HTTPS) nbdkit: curl[7]: debug: curl: open returned handle 0x7ff9840012b0 nbdkit: curl[7]: debug: retry: open returned handle 0x7ff98400c370 nbdkit: curl[7]: debug: cacheextents: open returned handle 0x7ff992ffd4c0 nbdkit: curl[7]: debug: cow: open returned handle 0x7ff992ffd4c0 nbdkit: curl[7]: debug: curl: prepare readonly=1 nbdkit: curl[7]: debug: retry: prepare readonly=1 nbdkit: curl[7]: debug: cacheextents: prepare readonly=1 nbdkit: curl[7]: debug: cow: prepare readonly=0 nbdkit: curl[7]: debug: cacheextents: get_size nbdkit: curl[7]: debug: retry: get_size nbdkit: curl[7]: debug: curl: get_size nbdkit: curl[7]: debug: cow: underlying file size: 12884901888 nbdkit: curl[7]: debug: bitmap resized to 786432 bytes nbdkit: curl[7]: debug: cow: get_size nbdkit: curl[7]: debug: cow: underlying file size: 12884901888 nbdkit: curl[7]: debug: bitmap resized to 786432 bytes nbdkit: curl[7]: debug: cow: can_write nbdkit: curl[7]: debug: cow: can_zero nbdkit: curl[7]: debug: cacheextents: can_zero nbdkit: curl[7]: debug: cow: can_fast_zero nbdkit: curl[7]: debug: cow: can_trim nbdkit: curl[7]: debug: cow: can_fua nbdkit: curl[7]: debug: cow: can_flush nbdkit: curl[7]: debug: cow: is_rotational nbdkit: curl[7]: debug: cacheextents: is_rotational nbdkit: curl[7]: debug: retry: is_rotational nbdkit: curl[7]: debug: curl: is_rotational nbdkit: curl[7]: debug: cow: can_multi_conn nbdkit: curl[7]: debug: cow: can_cache nbdkit: curl[7]: debug: cacheextents: can_cache nbdkit: curl[7]: debug: retry: can_cache nbdkit: curl[7]: debug: curl: can_cache nbdkit: curl[7]: debug: cow: can_extents nbdkit: curl[7]: debug: newstyle negotiation: flags: export 0x5ad nbdkit: curl[7]: debug: newstyle negotiation: NBD_OPT_GO: ignoring NBD_INFO_* request 3 (NBD_INFO_BLOCK_SIZE) nbdkit: curl[7]: debug: handshake complete, processing requests serially nbdkit: curl[7]: debug: cacheextents: can_extents nbdkit: curl[7]: debug: retry: can_extents nbdkit: curl[7]: debug: curl: can_extents nbdkit: cow.c:591: cow_extents: Assertion `count > 0' failed. Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones Read my programming and virtualization blog: http://rwmj.wordpress.com virt-p2v converts physical machines to virtual machines. Boot with a live CD or over the network (PXE) and turn machines into KVM guests. http://libguestfs.org/virt-v2v