Revert "Revert "Merge pull request #2449 from wkennington/master.grub""

This reverts commit 94205f5f21c4d9942bb4205c06229438051b6853.

Conflicts:
	nixos/modules/system/boot/loader/grub/install-grub.pl

1 files changed, 21 insertions, 0 deletions

diff --git a/nixos/modules/installer/tools/nixos-generate-config.pl b/nixos/modules/installer/tools/nixos-generate-config.pl
index 66a8152a3a6..73dd87cef5c 100644
--- a/nixos/modules/installer/tools/nixos-generate-config.pl
+++ b/nixos/modules/installer/tools/nixos-generate-config.pl
@@ -20,6 +20,13 @@ sub uniq {
     return @res;
 }
 
+sub runCommand {
+    my ($cmd) = @_;
+    open FILE, "$cmd 2>/dev/null |" or die "Failed to execute: $cmd\n";
+    my @ret = <FILE>;
+    close FILE;
+    return ($?, @ret);
+}
 
 # Process the command line.
 my $outDir = "/etc/nixos";
@@ -337,6 +344,20 @@ EOF
         }
     }
 
+    # Is this a btrfs filesystem?
+    if ($fsType eq "btrfs") {
+        my ($status, @info) = runCommand("btrfs subvol show $rootDir$mountPoint");
+        if ($status != 0) {
+            die "Failed to retreive subvolume info for $mountPoint";
+        }
+        my @subvols = join("", @info) =~ m/Name:[ \t\n]*([^ \t\n]*)/;
+        if ($#subvols > 0) {
+            die "Btrfs subvol name for $mountPoint listed multiple times in mount\n"
+        } elsif ($#subvols == 0) {
+            push @extraOptions, "subvol=$subvols[0]";
+        }
+    }
+
     # Emit the filesystem.
     $fileSystems .= <<EOF;
   fileSystems.\"$mountPoint\" =