diff --git a/nixos/modules/system/boot/loader/grub/grub.nix b/nixos/modules/system/boot/loader/grub/grub.nix
index 81f94e8639d9d..f1a352867016b 100644
--- a/nixos/modules/system/boot/loader/grub/grub.nix
+++ b/nixos/modules/system/boot/loader/grub/grub.nix
@@ -90,7 +90,7 @@ let
         timeoutStyle
       ;
       path = with pkgs; makeBinPath (
-        [ coreutils gnused gnugrep findutils diffutils btrfs-progs util-linux mdadm ]
+        [ coreutils gnused gnugrep findutils diffutils util-linux mdadm ]
         ++ optional cfg.efiSupport efibootmgr
         ++ optionals cfg.useOSProber [ busybox os-prober ]);
       font = lib.optionalString (cfg.font != null) (
@@ -730,7 +730,6 @@ in
           install-grub-pl = pkgs.substituteAll {
             src = ./install-grub.pl;
             utillinux = pkgs.util-linux;
-            btrfsprogs = pkgs.btrfs-progs;
             inherit (config.system.nixos) distroName;
           };
           perl = pkgs.perl.withPackages (p: with p; [
diff --git a/nixos/modules/system/boot/loader/grub/install-grub.pl b/nixos/modules/system/boot/loader/grub/install-grub.pl
index 6f0f62546a018..71a9c5e1cff02 100644
--- a/nixos/modules/system/boot/loader/grub/install-grub.pl
+++ b/nixos/modules/system/boot/loader/grub/install-grub.pl
@@ -110,59 +110,20 @@ sub runCommand {
 # Discover information about the location of the bootPath
 struct(Fs => {
     device => '$',
+    root => '$',
     type => '$',
     mount => '$',
 });
-sub PathInMount {
-    my ($path, $mount) = @_;
-    my @splitMount = split /\//, $mount;
-    my @splitPath = split /\//, $path;
-    if ($#splitPath < $#splitMount) {
-        return 0;
-    }
-    for (my $i = 0; $i <= $#splitMount; $i++) {
-        if ($splitMount[$i] ne $splitPath[$i]) {
-            return 0;
-        }
-    }
-    return 1;
-}
 
 # Figure out what filesystem is used for the directory with init/initrd/kernel files
 sub GetFs {
     my ($dir) = @_;
-    my $bestFs = Fs->new(device => "", type => "", mount => "");
-    foreach my $fs (read_file("/proc/self/mountinfo")) {
-        chomp $fs;
-        my @fields = split / /, $fs;
-        my $mountPoint = $fields[4];
-        my @mountOptions = split /,/, $fields[5];
-
-        # Skip the optional fields.
-        my $n = 6; $n++ while $fields[$n] ne "-"; $n++;
-        my $fsType = $fields[$n];
-        my $device = $fields[$n + 1];
-        my @superOptions = split /,/, $fields[$n + 2];
-
-        # Skip the bind-mount on /nix/store.
-        next if $mountPoint eq "/nix/store" && (grep { $_ eq "rw" } @superOptions);
-        # Skip mount point generated by systemd-efi-boot-generator?
-        next if $fsType eq "autofs";
-
-        # Ensure this matches the intended directory
-        next unless PathInMount($dir, $mountPoint);
-
-        # Is it better than our current match?
-        if (length($mountPoint) > length($bestFs->mount)) {
-
-            # -d performs a stat, which can hang forever on network file systems,
-            # so we only make this call last, when it's likely that this is the mount point we need.
-            next unless -d $mountPoint;
-
-            $bestFs = Fs->new(device => $device, type => $fsType, mount => $mountPoint);
-        }
+    my ($status, @pathInfo) = runCommand("@utillinux@/bin/findmnt", "-n", "-u", "-v", "-o", "SOURCE,FSROOT,FSTYPE,TARGET", "-T", @{[$dir]});
+    if ($status != 0 || @pathInfo != 1) {
+        die "Failed to get file system (returned $status) for @{[$dir]}";
     }
-    return $bestFs;
+    my @fields = split /\s+/, $pathInfo[0];
+    return Fs->new(device => $fields[0], root => $fields[1], type => $fields[2], mount => $fields[3]);
 }
 struct (Grub => {
     path => '$',
@@ -172,10 +133,7 @@ sub GetFs {
 sub GrubFs {
     my ($dir) = @_;
     my $fs = GetFs($dir);
-    my $path = substr($dir, length($fs->mount));
-    if (substr($path, 0, 1) ne "/") {
-        $path = "/$path";
-    }
+    my $path = File::Spec->catdir($fs->root, substr($dir, length($fs->mount)));
     my $search = "";
 
     # ZFS is completely separate logic as zpools are always identified by a label
@@ -217,30 +175,6 @@ sub GrubFs {
             }
             $search .= $matches[0];
         }
-
-        # BTRFS is a special case in that we need to fix the referenced path based on subvolumes
-        if ($fs->type eq 'btrfs') {
-            my ($status, @id_info) = runCommand("@btrfsprogs@/bin/btrfs", "subvol", "show", @{[$fs->mount]});
-            if ($status != 0) {
-                die "Failed to retrieve subvolume info for @{[$fs->mount]}\n";
-            }
-            my @ids = join("\n", @id_info) =~ m/^(?!\/\n).*Subvolume ID:[ \t\n]*([0-9]+)/s;
-            if ($#ids > 0) {
-                die "Btrfs subvol name for @{[$fs->device]} listed multiple times in mount\n"
-            } elsif ($#ids == 0) {
-                my ($status, @path_info) = runCommand("@btrfsprogs@/bin/btrfs", "subvol", "list", @{[$fs->mount]});
-                if ($status != 0) {
-                    die "Failed to find @{[$fs->mount]} subvolume id from btrfs\n";
-                }
-                my @paths = join("", @path_info) =~ m/ID $ids[0] [^\n]* path ([^\n]*)/;
-                if ($#paths > 0) {
-                    die "Btrfs returned multiple paths for a single subvolume id, mountpoint @{[$fs->mount]}\n";
-                } elsif ($#paths != 0) {
-                    die "Btrfs did not return a path for the subvolume at @{[$fs->mount]}\n";
-                }
-                $path = "/$paths[0]$path";
-            }
-        }
     }
     if (not $search eq "") {
         $search = "search --set=drive$driveid " . $search;