When zfs_domount fails zsb will be freed, and its caller
mount_nodev/get_sb_nodev will do deactivate_locked_super and calls into
zfs_preumount.
In order to make sure we don't touch any nonexistent stuff, we must make sure
s_fs_info is NULL in the fail path so zfs_preumount can easily check that.
Signed-off-by: Chunwei Chen <david.chen@osnexus.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#4867
Issue #4854
be88e733a6