mkfs.ext4 on nbd gets stuck

Question

I am trying to mkfs ext4 filesystem on /dev/nbd0 (I am on Ubuntu) I do not get any error msg and the command just gets stuck sudo mkfs.ext4 /dev/nbd0

I am using this BUSE code from github: https://github.com/acozzette/BUSE/blob/master/README.md into my own program.

I checked dmesg and I see this error:

[ 3775.418801] block nbd2: Possible stuck request 000000000e9ecebd: control (read@0,1024B). Runtime 3240 seconds

but it doesn't say why is it stuck.

Any clues would be great. Thanks!

Answer 1

I found the problem! the read and write functions where not complete and I was not sending the reply back to the NBD client server and so it was getting stuck trying to read/write while building the file system on the block device.