The function ufs_disk_close has no failure points.
The function ufs_disk_fillout may fail for any of the reasons ufs_disk_fillout_blank might, as well as for any reason sbread(3) might.
The ufs_disk_fillout_blank may fail and set errno for any of the errors specified for the library functions open(2), strdup(3). Additionally, it may follow the libufs(3) error methodologies in situations where no device could be found to open.
The function ufs_disk_write may fail and set errno for any of the errors specified for the library functions open(2) and stat(2). Namely, it will fail if the disk in question may not be written to.
open(2), getfsfile(3), libufs(3), sbread(3)