Don't count '@' for dataset namelen if not a snapshot. This
fixes making a pool unimportable when the dataset namelen
is 255.
Add test file for zfs create name length 255.
Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Chunwei Chen <david.chen@osnexus.com>
Closes#5432Closes#5456
a806cb6a89