Size zram the way Fedora does

zram-size = min(ram, 8192) is Fedora's default since F34, where
zram-fraction=1.0 with max-zram-size=8192 has run on desktops for five
years. The previous min(ram / 2, 8192) halved that on every machine
below 16G with nothing behind the fraction; at 16G and above the two
already agree.

A changed size only reaches a running device on the next boot, so the
migration resizes an empty device now and asks for a reboot otherwise.
It asks the generator what the config evaluates to rather than
repeating the expression here, and does neither when the device already
matches.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

test/shell.d/zram-resize-test.sh

@@ -0,0 +1,109 @@
+#!/bin/bash
+
+source "$(dirname "${BASH_SOURCE[0]}")/base-test.sh"
+
+require_command /usr/lib/systemd/system-generators/zram-generator
+
+migration=$(grep -rl 'Resize zram to match the shipped config' "$ROOT/migrations" | head -n 1 || true)
+[[ -n $migration ]] || fail "zram resize migration exists"
+
+TMPDIR=$(mktemp -d)
+trap 'rm -rf "$TMPDIR"' EXIT
+
+# The migration shells out to sudo, systemctl and omarchy-state. Stub all three
+# so the test never touches the real system, and record what each run did.
+stub_bin="$TMPDIR/bin"
+mkdir -p "$stub_bin"
+
+cat >"$stub_bin/sudo" <<'STUB'
+#!/bin/bash
+exec "$@"
+STUB
+
+cat >"$stub_bin/systemctl" <<'STUB'
+#!/bin/bash
+echo "systemctl $*" >>"$ACTIONS"
+[[ ${SYSTEMCTL_FAIL:-0} == 1 ]] && exit 1
+exit 0
+STUB
+
+cat >"$stub_bin/omarchy-state" <<'STUB'
+#!/bin/bash
+echo "omarchy-state $*" >>"$ACTIONS"
+STUB
+
+chmod +x "$stub_bin/sudo" "$stub_bin/systemctl" "$stub_bin/omarchy-state"
+
+# ZRAM_GENERATOR_ROOT redirects both the config search and /proc/meminfo, so the
+# migration's own generator call resolves against this fixture instead of the
+# host. 16G of RAM against the shipped config is a 8192MB device.
+gen_root="$TMPDIR/genroot"
+mkdir -p "$gen_root/usr/lib/systemd/zram-generator.conf.d" "$gen_root/proc"
+cp "$ROOT/default/systemd/zram-generator.conf.d/90-omarchy.conf" \
+  "$gen_root/usr/lib/systemd/zram-generator.conf.d/"
+printf 'MemTotal:       %d kB\n' $((16 * 1024 * 1024)) >"$gen_root/proc/meminfo"
+
+desired_bytes=$((8192 * 1024 * 1024))
+
+# omarchy-migrate runs each migration with `bash -euo pipefail` and stops the
+# whole chain on a non-zero exit, so match that invocation exactly.
+run_migration() {
+  local disksize="$1" used="$2" fail_reload="${3:-0}"
+
+  printf '%s' "$disksize" >"$TMPDIR/disksize"
+  printf 'Filename\tType\tSize\tUsed\tPriority\n' >"$TMPDIR/swaps"
+  [[ -n $used ]] &&
+    printf '/dev/zram0 partition 8388604 %s 100\n' "$used" >>"$TMPDIR/swaps"
+
+  : >"$TMPDIR/actions"
+
+  PATH="$stub_bin:$PATH" \
+    ACTIONS="$TMPDIR/actions" \
+    SYSTEMCTL_FAIL="$fail_reload" \
+    ZRAM_GENERATOR_ROOT="$gen_root" \
+    OMARCHY_ZRAM_DISKSIZE="$TMPDIR/disksize" \
+    OMARCHY_SWAPS="$TMPDIR/swaps" \
+    bash -euo pipefail "$migration" >/dev/null ||
+    fail "migration exits clean (disksize=$disksize used=$used reload_fail=$fail_reload)"
+}
+
+did() { grep -qF "$1" "$TMPDIR/actions"; }
+
+# Already the size the config asks for: the device is correct however it got
+# there, so the migration must not restart it or ask for a reboot.
+run_migration "$desired_bytes" 4193612
+[[ -s $TMPDIR/actions ]] && fail "correctly sized device is left alone" \
+  "expected no privileged calls, got: $(cat "$TMPDIR/actions")"
+pass "correctly sized device is left alone"
+pass "correctly sized device asks for no reboot"
+
+# Right size but still in use, and the reload never even happens.
+run_migration "$desired_bytes" 0
+did "systemctl restart" && fail "correctly sized empty device is left alone"
+pass "correctly sized empty device is left alone"
+
+# Wrong size and empty: safe to resize now.
+run_migration $((4096 * 1024 * 1024)) 0
+did "systemctl restart dev-zram0.swap" || fail "empty device is restarted"
+did "omarchy-state set reboot-required" && fail "empty device asks for no reboot"
+pass "empty device is restarted"
+pass "empty device asks for no reboot"
+
+# Wrong size with pages stored: resizing would fault them all back in, so defer.
+run_migration $((4096 * 1024 * 1024)) 4193612
+did "systemctl restart" && fail "device in use is not restarted"
+did "omarchy-state set reboot-required" || fail "device in use asks for a reboot"
+pass "device in use is not restarted"
+pass "device in use asks for a reboot"
+
+# No zram device at all reads as empty, and the restart brings it up.
+run_migration "" ""
+did "systemctl restart dev-zram0.swap" || fail "absent device is created"
+pass "absent device is created"
+
+# A failed daemon-reload must fall back to asking for a reboot.
+run_migration $((4096 * 1024 * 1024)) 0 1
+did "systemctl restart" && fail "failed reload does not restart"
+did "omarchy-state set reboot-required" || fail "failed reload asks for a reboot"
+pass "failed reload does not restart"
+pass "failed reload asks for a reboot"