Re: [Libguestfs] nbdkit & qemu 2.12: qemu-img: Protocol error: simple reply when structured reply chunk was expected

On Sat, Mar 23, 2019 at 06:57:14AM -0500, Eric Blake wrote: > And what workaround would that be? Looking at the qemu patch, the > problem is that qemu asked for "base:allocation" and nbdkit replied with > 0 contexts. The workaround would either be to reply with > NBD_REP_ERR_UNSUP (the behavior before NBD_OPT_SET_META_CONTEXT was > added), or to implement "base:allocation" (even if we implement the > poor-man's version that always reports that the entire image is data, > for all requests, without any feedback from the plugins). The former > feels odd, but the latter seems oddly appealing as progress towards our > end goal (kind of how our initial implementation of NBD_CMD_WRITE_ZEROES > was always advertised even before we finished wiring up plug support). A good point here is what happens with the block-status branch[1]. Let's see: $ ./nbdkit memory size=64M --run '/home/rjones/d/qemu/qemu-img convert $nbd /var/tmp/out' qemu-img: Payload too large nbdkit: memory.1: error: write reply: NBD_CMD_BLOCK_STATUS: Broken pipe Oh dear. I believe this is actually a bug in the block status code so let's see if I can narrow this down first ...