[Libguestfs] nbdkit: Could not read L1 table when reading exported qcow2

[Han Han]

Hello, I face a problem on the nbdkit server:

Version-Release number of selected component (if applicable):
nbdkit-v1.9.1
qemu-utils-2.12+dfsg-3+b1

How reproducible:
100%

Steps:
1. Create a qcow2 file
# qemu-img create disk 1G -f qcow2

2. Export the qcow2 file then try to read it via nbd url
# nbdkit file file=disk -e raw -v
nbdkit: debug: TLS disabled: could not load TLS certificates
nbdkit: debug: registering plugin
/usr/local/lib/nbdkit/plugins/nbdkit-file-plugin.so
nbdkit: debug: registered plugin
/usr/local/lib/nbdkit/plugins/nbdkit-file-plugin.so (name file)
nbdkit: debug: file: load
nbdkit: debug: file: config key=file, value=/tmp/disk
nbdkit: debug: file: config_complete
nbdkit: debug: bound to IP address <any>:10809 (2 socket(s))
nbdkit: debug: forked into background (new pid = 32524)

3. Try to read the file via nbd:
# qemu-img info
nbd://localhost/raw

qemu-img: Could not open 'nbd://localhost/raw': Could not read L1 table:
Invalid argument

Logs from nbdkit:
nbdkit: debug: file: open readonly=0
nbdkit: file[1]: debug: newstyle negotiation: flags: global 0x3
nbdkit: file[1]: debug: newstyle negotiation: client flags: 0x3
nbdkit: file[1]: debug: newstyle negotiation: NBD_OPT_GO: client requested
export 'raw' (ignored)
nbdkit: file[1]: debug: get_size
nbdkit: file[1]: debug: can_write
nbdkit: file[1]: debug: can_zero
nbdkit: file[1]: debug: can_write
nbdkit: file[1]: debug: can_trim
nbdkit: file[1]: debug: can_fua
nbdkit: file[1]: debug: can_flush
nbdkit: file[1]: debug: is_rotational
nbdkit: file[1]: debug: newstyle negotiation: flags: export 0x6d
nbdkit: file[1]: debug: newstyle negotiation: NBD_OPT_GO: ignoring
NBD_INFO_* request 3
nbdkit: file[1]: debug: handshake complete, processing requests with 16
threads
nbdkit: debug: starting worker thread file.0
nbdkit: debug: starting worker thread file.1
nbdkit: debug: starting worker thread file.3
nbdkit: debug: starting worker thread file.2
nbdkit: debug: starting worker thread file.4
nbdkit: debug: starting worker thread file.5
nbdkit: debug: starting worker thread file.7
nbdkit: debug: starting worker thread file.6
nbdkit: debug: starting worker thread file.8
nbdkit: debug: starting worker thread file.9
nbdkit: debug: starting worker thread file.10
nbdkit: debug: starting worker thread file.11
nbdkit: debug: starting worker thread file.12
nbdkit: debug: starting worker thread file.13
nbdkit: debug: starting worker thread file.14
nbdkit: debug: starting worker thread file.15
nbdkit: file.1: debug: pread count=512 offset=0
nbdkit: file.0: debug: pread count=512 offset=0
nbdkit: file.3: debug: sending error reply: Invalid argument
nbdkit: file.4: debug: client sent disconnect command, closing connection
nbdkit: file.4: debug: exiting worker thread file.4
nbdkit: file.2: debug: exiting worker thread file.2
nbdkit: file.7: debug: exiting worker thread file.7
nbdkit: file.5: debug: exiting worker thread file.5
nbdkit: file.6: debug: exiting worker thread file.6
nbdkit: file.8: debug: exiting worker thread file.8
nbdkit: file.9: debug: exiting worker thread file.9
nbdkit: file.10: debug: exiting worker thread file.10
nbdkit: file.11: debug: exiting worker thread file.11
nbdkit: file.12: debug: exiting worker thread file.12
nbdkit: file.0: debug: exiting worker thread file.0
nbdkit: file.14: debug: exiting worker thread file.14
nbdkit: file.15: debug: exiting worker thread file.15
nbdkit: file.1: debug: exiting worker thread file.1
nbdkit: file.13: debug: exiting worker thread file.13
nbdkit: file.3: debug: exiting worker thread file.3
nbdkit: file[1]: debug: close


Could you please check if it is a bug from nbdkit? Thanks
-- 
Best regards,
-----------------------------------
Han Han
Quality Engineer
Redhat.

Email: hhan at redhat.com
Phone: +861065339333
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