update root partition size for multidisk layout

archinstall/lib/interactions/disk_conf.py

@@ -2,7 +2,7 @@
 
 from pathlib import Path
 from typing import Any, TYPE_CHECKING
-from typing import Optional, List, Tuple
+from typing import Optional, List
 
 from .. import disk
 from ..disk.device_model import BtrfsMountOption
@@ -372,7 +372,7 @@ def suggest_multi_disk_layout(
 	# https://www.reddit.com/r/btrfs/comments/9us4hr/what_is_your_btrfs_partitionsubvolumes_scheme/
 	min_home_partition_size = disk.Size(40, disk.Unit.GiB, disk.SectorSize.default())
 	# rough estimate taking in to account user desktops etc. TODO: Catch user packages to detect size?
-	desired_root_partition_size = disk.Size(20, disk.Unit.GiB, disk.SectorSize.default())
+	min_root_partition_size = disk.Size(20, disk.Unit.GiB, disk.SectorSize.default())
 	mount_options = []
 
 	if not filesystem_type:
@@ -382,20 +382,25 @@ def suggest_multi_disk_layout(
 	possible_devices = list(filter(lambda x: x.device_info.total_size >= min_home_partition_size, devices))
 	home_device = max(possible_devices, key=lambda d: d.device_info.total_size) if possible_devices else None
 
-	# find proper device for /root
-	devices_delta = {}
-	for device in devices:
-		if device is not home_device:
-			delta = device.device_info.total_size - desired_root_partition_size
-			devices_delta[device] = delta
-
-	sorted_delta: List[Tuple[disk.BDevice, Any]] = sorted(devices_delta.items(), key=lambda x: x[1])
-	root_device: Optional[disk.BDevice] = sorted_delta[0][0]
+	# find proper device for /root (size >= min_root_size and not home)
+	root_possible_devices: list[disk.BDevice] = [
+		device
+		for device in devices
+		if device.device_info.total_size >= min_root_partition_size
+		and device is not home_device
+	]
+
+	# we take the smallest disk >= min_root_size
+	root_device: Optional[disk.BDevice] = (
+		min(root_possible_devices, key=lambda d: d.device_info.total_size)
+		if possible_devices
+		else None
+	)
 
 	if home_device is None or root_device is None:
 		text = _('The selected drives do not have the minimum capacity required for an automatic suggestion\n')
 		text += _('Minimum capacity for /home partition: {}GiB\n').format(min_home_partition_size.format_size(disk.Unit.GiB))
-		text += _('Minimum capacity for Arch Linux partition: {}GiB').format(desired_root_partition_size.format_size(disk.Unit.GiB))
+		text += _('Minimum capacity for Arch Linux partition: {}GiB').format(min_root_partition_size.format_size(disk.Unit.GiB))
 		Menu(str(text), [str(_('Continue'))], skip=False).run()
 		return []
 
@@ -423,8 +428,12 @@ def suggest_multi_disk_layout(
 	boot_partition = _boot_partition(root_device_sector_size, using_gpt)
 	root_device_modification.add_partition(boot_partition)
 
+	# add root partition to the root device
 	root_start = boot_partition.start + boot_partition.length
-	root_length = root_device.device_info.total_size - root_start
+	available_space = root_device.device_info.total_size - root_start
+	root_length = process_root_partition_size(
+		available_space=available_space, sector_size=root_device.device_info.sector_size
+	)
 
 	if using_gpt:
 		root_length -= root_align_buffer