#!/bin/bash

if ! test "$BASH_VERSION"; then echo "error: shell is not bash" >&2; exit 1; fi
shopt -s inherit_errexit 2>/dev/null ||: # ignore fail in bash < 4.4
set -eE -o pipefail
trap 'echo "$0:$LINENO:error: \"$BASH_COMMAND\" exit status: $?, PIPESTATUS: ${PIPESTATUS[*]}" >&2' ERR

[[ $EUID == 0 ]] || exec sudo -E "${BASH_SOURCE[0]}" "$@"


# todo: we should make this be a service which sets the /sys/ value
# before the mount target or something like that, because if you hot
# plug a drive in, its ata number will change on reboot, meaning you
# have to remember to run this again and then reboot again.

# example from t8 kernel
# Sep 01 14:35:01 watson kernel: ata7.00: status: { DRDY }
# Sep 01 14:35:01 watson kernel: ata7.00: failed command: WRITE FPDMA QUEUED
# Sep 01 14:35:01 watson kernel: ata7.00: cmd 61/08:c0:b8:bf:ff/00:00:01:00:00/40 tag 24 ncq 4096 out


# https://wiki.archlinux.org/index.php/Solid_state_drive#Resolving_NCQ_errors
# evo-870 doesnt get along well with d16.
# Dmesg gives us an ata number we could disable specifically on the command line, but I've had that number change on me between oses, so reenabling ncq

debug=false
if [[ $1 == debug ]]; then
  debug=true
fi

upgrub=true
if [[ $1 == no-upgrub ]]; then
  upgrub=false
fi

regex='^.*-part[0-9]*$'
for path in /dev/disk/by-id/ata-Samsung_SSD_870*; do
  if [[ ! $path =~ $regex ]]; then
    byid=$path
    break
  fi
done

if [[ ! -e $byid ]]; then
  if $debug; then echo "samsung 870 not plugged in or not found"; fi
  exit 0
fi

dev=$(readlink $byid)
if [[ ! $dev ]]; then
  exit 1
fi

dev=${dev##*/}

depth=$(cat /sys/block/$dev/device/queue_depth)
if [[ $depth != 0 ]]; then
  if grep -qF libata.force=noncq /proc/cmdline; then
    echo $0: warning, cant change queue_depth due to globally disabled ncq
  else
    if $debug; then
      echo "updating to 1 if not: cat /sys/block/$dev/device/queue_depth"
      cat /sys/block/$dev/device/queue_depth
    fi
    echo 1 >/sys/block/$dev/device/queue_depth
  fi
fi

sys=$(readlink /sys/block/$dev)
ata=${sys#*/*/*/*/ata}
ata=${ata%%/*}

arg=libata.force=${ata}.00:noncq

if ! grep "^GRUB_CMDLINE_LINUX_DEFAULT=.*[\" ]${arg//./\\.}[\" ]" /etc/default/grub; then
  sed -ri "s/([\" ])libata.force=[^ ]+ */\1/g;s/^GRUB_CMDLINE_LINUX_DEFAULT=\"(.*)/GRUB_CMDLINE_LINUX_DEFAULT=\"$arg \1/" /etc/default/grub
  if $upgrub; then
    echo "$0: warning: grub updated. you may want to reboot"
    if type -P update-grub2 &>/dev/null; then
      update-grub2
    else
      update-grub
    fi
  fi
fi