From 80bb1b17b3f596dbd7331cf9cb20a46c8ef9800b Mon Sep 17 00:00:00 2001
From: Michael Chang <mchang@suse.com>
Date: Sat, 22 Aug 2020 02:32:43 +0800
Subject: [PATCH] Unify the check to enable btrfs relative path

This unified the test in grub-install and grub-mkconfig that the path to
default or selected btrfs subvolume/snapshot is used if the root file
system is btrfs and the config has enabled btrfs snapshot booting.

Signed-off-by: Michael Chang <mchang@suse.com>
---
 util/grub-install.c       | 67 +++++++++++++++++++++++++++------------
 util/grub-mkconfig_lib.in |  3 +-
 2 files changed, 48 insertions(+), 22 deletions(-)

--- a/util/grub-install.c
+++ b/util/grub-install.c
@@ -886,6 +886,7 @@
   const char *efi_file = NULL;
   char **grub_devices;
   grub_fs_t grub_fs;
+  grub_fs_t root_fs;
   grub_device_t grub_dev = NULL;
   enum grub_install_plat platform;
   char *grubdir, *device_map;
@@ -898,6 +899,8 @@
   int efidir_is_mac = 0;
   int is_prep = 0;
   const char *pkgdatadir;
+  char *rootdir_path;
+  char **rootdir_devices;
 
   grub_util_host_init (&argc, &argv);
   product_version = xstrdup (PACKAGE_VERSION);
@@ -911,9 +914,6 @@
 
   grub_util_load_config (&config);
 
-  if (config.is_suse_btrfs_snapshot_enabled)
-    use_relative_path_on_btrfs = 1;
-
   if (!bootloader_id && config.grub_distributor)
     {
       char *ptr;
@@ -1064,6 +1064,45 @@
   grub_hostfs_init ();
   grub_host_init ();
 
+  {
+    char *rootdir_grub_devname;
+    grub_device_t rootdir_grub_dev;
+    char *t = grub_util_path_concat (2, "/", rootdir);
+
+    rootdir_path = grub_canonicalize_file_name (t);
+    if (!rootdir_path)
+      grub_util_error (_("failed to get canonical path of `%s'"), t);
+
+    rootdir_devices = grub_guess_root_devices (rootdir_path);
+    if (!rootdir_devices || !rootdir_devices[0])
+      grub_util_error (_("cannot find a device for %s (is /dev mounted?)"),
+		      rootdir_path);
+
+    for (curdev = rootdir_devices; *curdev; curdev++)
+	grub_util_pull_device (*curdev);
+
+    rootdir_grub_devname = grub_util_get_grub_dev (rootdir_devices[0]);
+    if (!rootdir_grub_devname)
+      grub_util_error (_("cannot find a GRUB drive for %s.  Check your device.map"),
+		       rootdir_devices[0]);
+
+    rootdir_grub_dev = grub_device_open (rootdir_grub_devname);
+    if (! rootdir_grub_dev)
+      grub_util_error ("%s", grub_errmsg);
+
+    root_fs = grub_fs_probe (rootdir_grub_dev);
+    if (!root_fs)
+      grub_util_error ("%s", grub_errmsg);
+
+    if (config.is_suse_btrfs_snapshot_enabled
+	&& grub_strncmp(root_fs->name, "btrfs", sizeof ("btrfs") - 1) == 0)
+      use_relative_path_on_btrfs = 1;
+
+    free (t);
+    free (rootdir_grub_devname);
+    grub_device_close (rootdir_grub_dev);
+  }
+
   switch (platform)
     {
     case GRUB_INSTALL_PLATFORM_I386_EFI:
@@ -1478,8 +1517,7 @@
               debug_image);
     }
 
-  if (config.is_suse_btrfs_snapshot_enabled
-      && grub_strncmp(grub_fs->name, "btrfs", sizeof ("btrfs") - 1) == 0)
+  if (use_relative_path_on_btrfs)
     {
       if (!load_cfg_f)
         load_cfg_f = grub_util_fopen (load_cfg, "wb");
@@ -1670,22 +1708,14 @@
 
 #ifdef __linux__
 
-  if (config.is_suse_btrfs_snapshot_enabled
-      && grub_strncmp(grub_fs->name, "btrfs", sizeof ("btrfs") - 1) == 0)
+  if (use_relative_path_on_btrfs)
     {
       char *subvol = NULL;
       char *mount_path = NULL;
       grub_uint64_t subvolid = 0;
-      char **rootdir_devices = NULL;
-      char *t = grub_util_path_concat (2, "/", rootdir);
-      char *rootdir_path = grub_canonicalize_file_name (t);
-
-      if (rootdir_path && grub_util_is_directory (rootdir_path))
-	rootdir_devices = grub_guess_root_devices (rootdir_path);
-
-      if (rootdir_devices && rootdir_devices[0])
-	if (grub_strcmp (rootdir_devices[0], grub_devices[0]) == 0)
-	  subvol = grub_util_get_btrfs_subvol (platdir, &mount_path, &subvolid);
+
+      if (grub_strcmp (rootdir_devices[0], grub_devices[0]) == 0)
+	subvol = grub_util_get_btrfs_subvol (platdir, &mount_path, &subvolid);
 
       if (subvol && mount_path)
 	{
@@ -1709,11 +1739,6 @@
 	    }
 	}
 
-      free (t);
-      free (rootdir_path);
-      for (curdev = rootdir_devices; *curdev; curdev++)
-	free (*curdev);
-      free (rootdir_devices);
       free (subvol);
       free (mount_path);
     }
--- a/util/grub-mkconfig_lib.in
+++ b/util/grub-mkconfig_lib.in
@@ -49,7 +49,8 @@
 
 make_system_path_relative_to_its_root ()
 {
-  if [ "x${SUSE_BTRFS_SNAPSHOT_BOOTING}" = "xtrue" ] ; then
+  if [ "x${SUSE_BTRFS_SNAPSHOT_BOOTING}" = "xtrue" ] &&
+     [ "x${GRUB_FS}" = "xbtrfs" ] ; then
   "${grub_mkrelpath}" -r "$1"
   else
   "${grub_mkrelpath}" "$1"