Add a method to find the Btrfs default_subvol

src/modules/FileSystems.rb

@@ -31,6 +31,7 @@
 # $Id$
 require "storage"
 require "yast"
+require "yast2/execute"
 
 module Yast
   class FileSystemsClass < Module
@@ -46,6 +47,7 @@ def main
       Yast.import "Encoding"
       Yast.import "Stage"
       Yast.import "StorageInit"
+      Yast.import "ProductFeatures"
 
       @conv_fs = {
         "def_sym" => :unknown,
@@ -2054,6 +2056,47 @@ def default_subvol
       @default_subvol
     end
 
+    # Try to find the default subvolume name in the target system
+    #
+    # * Root partition takes precedence
+    # * Not supported: more than 1 Btrfs filesystems, one using
+    #   a '@' default subvolume and the other using ''. In that case,
+    #   default_subvolume is set to product's default.
+    #
+    # @return [String,nil] Default subvolume from the target system
+    def default_subvol_from_filesystem
+      parts = Storage.GetTargetMap.map { |_k, d| d.fetch("partitions")  }.flatten.compact
+      btrfs_parts = parts.select { |p| p["used_fs"] == :btrfs }
+      default_subvol_names = btrfs_parts.reduce({}) do |memo, part|
+        memo[part["mount"]] = btrfs_subvol_name_for(part) unless part["mount"].nil?
+        memo
+      end
+
+      # Root takes precedence
+      return default_subvol_names["/"] if default_subvol_names.has_key?("/")
+
+      # If all has the same default subvolume name
+      found_names = default_subvol_names.values.uniq
+      return found_names.first if found_names.size == 1
+
+      # If there are different values, fallback to product's default
+      default_subvol_from_product
+    end
+
+    # Default subvol name from product
+    #
+    # @return [String] Default subvolume name
+    def default_subvol_from_product
+      ProductFeatures.GetStringFeature("partitioning", "btrfs_default_subvolume")
+    end
+
+    protected
+
+    def btrfs_subvol_name_for(partition)
+      ret = Yast::Execute.on_target("btrfs", "subvol", "list", partition["mount"], stdout: :capture)
+      ret.split("\n").first =~ /.+ @\z/ ? "@" : ""
+    end
+
     publish :variable => :conv_fs, :type => "map <string, any>"
     publish :variable => :possible_root_fs, :type => "const list <symbol>"
     publish :function => :system_m_points, :type => "list <string> ()"

test/filesystems_test.rb

@@ -0,0 +1,64 @@
+#!/usr/bin/env rspec
+
+require_relative "spec_helper"
+
+Yast.import "FileSystems"
+Yast.import "Storage"
+
+describe Yast::FileSystems do
+  subject { Yast::FileSystems }
+
+  describe "#default_subvol_from_filesystem" do
+    let(:target_map) { YAML.load_file(File.join(FIXTURES_PATH, "subvolumes.yml")) }
+    let(:btrfs_list) { File.read(File.join(FIXTURES_PATH, "btrfs_list.out")) }
+    let(:btrfs_list_no_at) { File.read(File.join(FIXTURES_PATH, "btrfs_list_no_at.out")) }
+    let(:default_subvol) { "@" }
+
+    before do
+      allow(Yast::Storage).to receive(:GetTargetMap).and_return(target_map)
+      allow(Yast::ProductFeatures).to receive(:GetStringFeature)
+        .with("partitioning", "btrfs_default_subvolume").and_return(default_subvol)
+    end
+
+    context "when root partition uses the default subvolume name (@)" do
+      let(:btrfs_list) { File.read(File.join(FIXTURES_PATH, "btrfs_list.out")) }
+
+      it "returns the default subvolume name" do
+        allow(Yast::Execute).to receive(:on_target).with("btrfs", "subvol", "list", "/", anything)
+          .and_return(btrfs_list)
+        allow(Yast::Execute).to receive(:on_target).with("btrfs", "subvol", "list", "/srv", anything)
+          .and_return(btrfs_list_no_at)
+        expect(subject.default_subvol_from_filesystem).to eq(default_subvol)
+      end
+    end
+
+    context "when root partitions does not use the default subvolume name (@)" do
+      before do
+        allow(Yast::Execute).to receive(:on_target).with("btrfs", "subvol", "list", "/", anything)
+          .and_return(btrfs_list_no_at)
+      end
+
+      context "but all partitions uses the same subvolume name" do
+        before do
+          allow(Yast::Execute).to receive(:on_target).with("btrfs", "subvol", "list", "/srv", anything)
+            .and_return(btrfs_list_no_at)
+        end
+
+        it "returns the used name ('' in this case)" do
+          expect(subject.default_subvol_from_filesystem).to eq("")
+        end
+      end
+
+      context "and partitions uses different subvolume names" do
+        before do
+          allow(Yast::Execute).to receive(:on_target).with("btrfs", "subvol", "list", "/srv", anything)
+            .and_return(btrfs_list)
+        end
+
+        it "returns the distribution default" do
+          expect(subject.default_subvol_from_filesystem).to eq("")
+        end
+      end
+    end
+  end
+end

test/fixtures/btrfs_list.out

@@ -0,0 +1,28 @@
+ID 257 gen 34 top level 5 path @
+ID 258 gen 51 top level 257 path @/.snapshots
+ID 259 gen 88 top level 258 path @/.snapshots/1/snapshot
+ID 260 gen 44 top level 257 path @/boot/grub2/i386-pc
+ID 261 gen 15 top level 257 path @/boot/grub2/x86_64-efi
+ID 262 gen 44 top level 257 path @/home
+ID 263 gen 51 top level 257 path @/opt
+ID 264 gen 50 top level 257 path @/srv
+ID 265 gen 88 top level 257 path @/tmp
+ID 266 gen 64 top level 257 path @/usr/local
+ID 267 gen 38 top level 257 path @/var/crash
+ID 268 gen 22 top level 257 path @/var/lib/mailman
+ID 269 gen 88 top level 257 path @/var/lib/named
+ID 270 gen 24 top level 257 path @/var/lib/pgsql
+ID 271 gen 88 top level 257 path @/var/log
+ID 272 gen 38 top level 257 path @/var/opt
+ID 273 gen 84 top level 257 path @/var/spool
+ID 274 gen 51 top level 257 path @/var/tmp
+ID 275 gen 30 top level 257 path @/mysubvol
+ID 276 gen 47 top level 275 path @/mysubvol/mysubsubvol
+ID 277 gen 32 top level 257 path @/myothersubvol
+ID 278 gen 47 top level 277 path @/myothersubvol/myothersubsubvol
+ID 279 gen 33 top level 257 path @/nocow
+ID 280 gen 35 top level 257 path @/myvol
+ID 282 gen 40 top level 259 path var/lib/machines
+ID 283 gen 48 top level 258 path @/.snapshots/2/snapshot
+ID 284 gen 49 top level 258 path @/.snapshots/3/snapshot
+ID 285 gen 50 top level 258 path @/.snapshots/4/snapshot

test/fixtures/btrfs_list_no_at.out

@@ -0,0 +1,27 @@
+ID 257 gen 48 top level 5 path .snapshots
+ID 258 gen 92 top level 257 path .snapshots/1/snapshot
+ID 259 gen 41 top level 5 path boot/grub2/i386-pc
+ID 260 gen 12 top level 5 path boot/grub2/x86_64-efi
+ID 261 gen 41 top level 5 path home
+ID 262 gen 49 top level 5 path opt
+ID 263 gen 47 top level 5 path srv
+ID 264 gen 91 top level 5 path tmp
+ID 265 gen 61 top level 5 path usr/local
+ID 266 gen 35 top level 5 path var/crash
+ID 267 gen 19 top level 5 path var/lib/mailman
+ID 268 gen 89 top level 5 path var/lib/named
+ID 269 gen 21 top level 5 path var/lib/pgsql
+ID 270 gen 90 top level 5 path var/log
+ID 271 gen 35 top level 5 path var/opt
+ID 272 gen 91 top level 5 path var/spool
+ID 273 gen 48 top level 5 path var/tmp
+ID 274 gen 27 top level 5 path mysubvol
+ID 275 gen 44 top level 274 path mysubvol/mysubsubvol
+ID 276 gen 29 top level 5 path @/myothersubvol
+ID 277 gen 44 top level 276 path @/myothersubvol/myothersubsubvol
+ID 278 gen 30 top level 5 path nocow
+ID 279 gen 32 top level 5 path myvol
+ID 281 gen 37 top level 258 path var/lib/machines
+ID 282 gen 45 top level 257 path .snapshots/2/snapshot
+ID 283 gen 46 top level 257 path .snapshots/3/snapshot
+ID 284 gen 47 top level 257 path .snapshots/4/snapshot

test/fixtures/subvolumes.yml

@@ -0,0 +1,185 @@
+---
+"/dev/vda":
+  unique: KSbE.Fxp0d3BezAE
+  bus: None
+  device: "/dev/vda"
+  bios_id: '0x80'
+  driver: virtio-pci
+  driver_module: virtio_pci
+  partitions:
+  - device: "/dev/vda1"
+    name: vda1
+    used_by:
+    - type: :UB_BTRFS
+      device: 8e6e04a4-758f-4d43-bab8-6b3dca3d31e2
+    used_by_type: :UB_BTRFS
+    used_by_device: 8e6e04a4-758f-4d43-bab8-6b3dca3d31e2
+    size_k: 13925376
+    used_fs: :btrfs
+    detected_fs: :btrfs
+    fstopt: defaults
+    nr: 2
+    fsid: 131
+    fstype: Linux native
+    region:
+    - 93
+    - 1734
+    type: :primary
+    boot: true
+    subvol:
+    - name: "@"
+    - name: "@/.snapshots"
+    - name: "@/.snapshots/1/snapshot"
+    - name: "@/home"
+    - name: "@/var/log"
+    - name: "@/var/lib/pgsql"
+    - name: "@/myvol"
+      nocow: true
+    - name: "@/.snapshots/1/snapshot/var/lib/machines"
+    - name: "@/.snapshots/2/snapshot"
+    - name: "@/.snapshots/3/snapshot"
+    - name: "@/.snapshots/4/snapshot"
+    uuid: 8e6e04a4-758f-4d43-bab8-6b3dca3d31e2
+    mount: "/"
+    mountby: :uuid
+  size_k: 14680064
+  cyl_size: 8225280
+  cyl_count: 1827
+  sector_size: 512
+  label: msdos
+  name: vda
+  max_logical: 255
+  max_primary: 4
+  type: :CT_DISK
+  transport: :unknown
+  used_by_type: :UB_NONE
+  used_by_device: ''
+  dasd_format: 0
+  dasd_type: 0
+"/dev/vdb":
+  unique: KSbE.Fxp0d3BezAE
+  bus: None
+  device: "/dev/vdb"
+  bios_id: '0x80'
+  driver: virtio-pci
+  driver_module: virtio_pci
+  partitions:
+  - device: "/dev/vdb1"
+    name: vdb1
+    used_by_type: :UB_NONE
+    used_by_device: ''
+    size_k: 753664
+    used_fs: :swap
+    detected_fs: :swap
+    mount: swap
+    mountby: :uuid
+    fstopt: defaults
+    uuid: 3fc06e37-d6b6-4411-baf3-2920cdf19fa4
+    nr: 1
+    fsid: 130
+    fstype: Linux swap
+    region:
+    - 0
+    - 94
+    type: :primary
+  - device: "/dev/vdb2"
+    name: vdb2
+    used_by:
+    - type: :UB_BTRFS
+      device: 862e2cbf-0501-48a1-85a3-142bfe3ab51b
+    used_by_type: :UB_BTRFS
+    used_by_device: 862e2cbf-0501-48a1-85a3-142bfe3ab51b
+    size_k: 13925376
+    used_fs: :btrfs
+    detected_fs: :btrfs
+    fstopt: defaults
+    nr: 2
+    fsid: 131
+    fstype: Linux native
+    region:
+    - 93
+    - 1734
+    type: :primary
+    boot: true
+    subvol:
+    - name: shared
+    - name: www
+    uuid: 862e2cbf-0501-48a1-85a3-142bfe3ab51b
+    mount: "/srv"
+    mountby: :uuid
+  size_k: 14680064
+  cyl_size: 8225280
+  cyl_count: 1827
+  sector_size: 512
+  label: msdos
+  name: vdb
+  max_logical: 255
+  max_primary: 4
+  type: :CT_DISK
+  transport: :unknown
+  used_by_type: :UB_NONE
+  used_by_device: ''
+  dasd_format: 0
+  dasd_type: 0
+"/dev/btrfs":
+  device: "/dev/btrfs"
+  name: btrfs
+  used_by_type: :UB_NONE
+  used_by_device: ''
+  type: :CT_BTRFS
+  partitions: []
+"/dev/tmpfs":
+  device: "/dev/tmpfs"
+  name: tmpfs
+  used_by_type: :UB_NONE
+  used_by_device: ''
+  type: :CT_TMPFS
+  partitions:
+  - device: tmpfs
+    name: none
+    used_by_type: :UB_NONE
+    used_by_device: ''
+    size_k: 233312
+    used_fs: :tmpfs
+    detected_fs: :tmpfs
+    mount: "/dev/shm"
+    mountby: :uuid
+    ignore_fstab: true
+    type: :tmpfs
+    fstype: TMPFS
+  - device: tmpfs
+    name: none
+    used_by_type: :UB_NONE
+    used_by_device: ''
+    size_k: 233312
+    used_fs: :tmpfs
+    detected_fs: :tmpfs
+    mount: "/run"
+    mountby: :uuid
+    ignore_fstab: true
+    type: :tmpfs
+    fstype: TMPFS
+  - device: tmpfs
+    name: none
+    used_by_type: :UB_NONE
+    used_by_device: ''
+    size_k: 233312
+    used_fs: :tmpfs
+    detected_fs: :tmpfs
+    mount: "/sys/fs/cgroup"
+    mountby: :uuid
+    ignore_fstab: true
+    type: :tmpfs
+    fstype: TMPFS
+  - device: tmpfs
+    name: none
+    used_by_type: :UB_NONE
+    used_by_device: ''
+    size_k: 46664
+    used_fs: :tmpfs
+    detected_fs: :tmpfs
+    mount: "/run/user/0"
+    mountby: :uuid
+    ignore_fstab: true
+    type: :tmpfs
+    fstype: TMPFS