Create a mirrored pool named foo
Create a pool named bar, and create a zvol on it
Remove one of foo's disks
In one terminal, do "zpool status foo" in a while loop
In another terminal, do "zpool online foo <removed disk's guid>" in a while loop
Verify that no deadlocks result after a few minutes, then kill both loops
Try to create a zpool on bar's zvol. It should fail.
Do "sysctl vfs.zfs.vol.recursive=1".
Try to create a zpool on bar's zvol. It should succeed.