I think that's fine, but @dfr has the final say.

LGTM!

LGTM!

LGTM!

Just one small change you could make to your commit message:

Just to clarify: the port seems ready to be committed. You might want to open an issue in the upstream repository. They could provide guidance for a workaround or a fix for the nbdfuse case. If that works for you, I can go ahead and commit it.

In D60639#1391347, @hayzam_gmail.com wrote:

In D60639#1391312, @dtxdf wrote:

I've done a quick test with nbdsh, nbdfuse and nbddump. nbdfuse "mounts" the NBD server and the read works fine, but the write seems to be in a loop, even writing a single byte. Everything else works fine.

Thanks for testing. With a TCP, file-backed nbdkit export, I reproduced the loop when appending one byte at EOF. Normal 64 MiB writes passed checksum verification.

I think this comes from upstream nbdfuse_write() returning zero at/past EOF, causing FreeBSD to retry indefinitely (https://gitlab.com/nbdkit/libnbd/-/blob/master/fuse/operations.c#L417-418). The same code exists in tagged 1.24.3 and current master.. Could you share your exact write command to confirm the same case?

My Unix-socket smoke test used these in separate terminals, with a fresh socket path and empty mount directory:

nbdkit -f -U "$socket" memory size=1M
nbdfuse -d -o debug "$mountpoint" --unix "$socket"

I've done a quick test with nbdsh, nbdfuse and nbddump. nbdfuse "mounts" the NBD server and the read works fine, but the write seems to be in a loop, even writing a single byte. Everything else works fine.