ZFS and mem management

[Pavlo]

zpool get all disk1
NAME   PROPERTY       VALUE       SOURCE
disk1  size           7.21T       -
disk1  capacity       71%         -
disk1  altroot        -           default
disk1  health         DEGRADED    -
disk1  guid           4448512342659541304  default
disk1  version        28          default
disk1  bootfs         -           default
disk1  delegation     on          default
disk1  autoreplace    off         default
disk1  cachefile      -           default
disk1  failmode       continue    local
disk1  listsnapshots  off         default
disk1  autoexpand     off         default
disk1  dedupditto     0           default
disk1  dedupratio     1.00x       -
disk1  free           2.09T       -
disk1  allocated      5.12T       -
disk1  readonly       off         -
disk1  comment        -           default

Nope, it doesn't scan .zfs/snapshot directory. Please ignore health,
that's just test machine.

Also the problem seems to be not about reading/writing, rather about
using mmap(). I just couldn't find better mailing list for my issue...