V2:
* Fix grub2-install --root-directory does not work for /boot/grub2/<arch> on
  separate btrfs subvolume (boo#1098420) 

v3:
* Fix executable stack on which function trampoline is constructed to support
  closure (nested function). The closure sematic is replaced.

--- a/grub-core/fs/btrfs.c
+++ b/grub-core/fs/btrfs.c
@@ -44,6 +44,7 @@
 #include <grub/command.h>
 #include <grub/env.h>
 #include <grub/extcmd.h>
+#include <grub/list.h>
 
 GRUB_MOD_LICENSE ("GPLv3+");
 
@@ -266,6 +267,12 @@
 grub_btrfs_read_logical (struct grub_btrfs_data *data,
 			 grub_disk_addr_t addr, void *buf, grub_size_t size,
 			 int recursion_depth);
+static grub_err_t
+get_root (struct grub_btrfs_data *data, struct grub_btrfs_key *key,
+	  grub_uint64_t *tree, grub_uint8_t *type);
+
+grub_uint64_t
+find_mtab_subvol_tree (const char *path, char **path_in_subvol);
 
 static grub_err_t
 read_sblock (grub_disk_t disk, struct grub_btrfs_superblock *sb)
@@ -1302,9 +1309,26 @@
   grub_err_t err;
   grub_uint64_t tree = 0;
   grub_uint8_t type;
+  grub_uint64_t saved_tree;
   struct grub_btrfs_key key;
 
+  if (path[0] == '\0')
+    {
+      data->fs_tree = 0;
+      return GRUB_ERR_NONE;
+    }
+
+  err = get_root (data, &key, &tree, &type);
+  if (err)
+    return err;
+
+  saved_tree = data->fs_tree;
+  data->fs_tree = tree;
+
   err = find_path (data, path, &key, &tree, &type);
+
+  data->fs_tree = saved_tree;
+
   if (err)
       return grub_error(GRUB_ERR_FILE_NOT_FOUND, "couldn't locate %s\n", path);
 
@@ -2321,11 +2345,20 @@
   grub_uint64_t tree;
   grub_uint8_t type;
   grub_size_t est_size = 0;
+  char *new_path = NULL;
 
   if (!data)
     return grub_errno;
 
-  err = find_path (data, path, &key_in, &tree, &type);
+  tree = find_mtab_subvol_tree (path, &new_path);
+
+  if (tree)
+    data->fs_tree = tree;
+
+  err = find_path (data, new_path ? new_path : path, &key_in, &tree, &type);
+  if (new_path)
+    grub_free (new_path);
+
   if (err)
     {
       grub_btrfs_unmount (data);
@@ -2452,11 +2485,21 @@
   struct grub_btrfs_inode inode;
   grub_uint8_t type;
   struct grub_btrfs_key key_in;
+  grub_uint64_t tree;
+  char *new_path = NULL;
 
   if (!data)
     return grub_errno;
 
-  err = find_path (data, name, &key_in, &data->tree, &type);
+  tree = find_mtab_subvol_tree (name, &new_path);
+
+  if (tree)
+    data->fs_tree = tree;
+
+  err = find_path (data, new_path ? new_path : name, &key_in, &data->tree, &type);
+  if (new_path)
+    grub_free (new_path);
+
   if (err)
     {
       grub_btrfs_unmount (data);
@@ -2691,6 +2734,150 @@
   return 0;
 }
 
+struct grub_btrfs_mtab
+{
+  struct grub_btrfs_mtab *next;
+  struct grub_btrfs_mtab **prev;
+  char *path;
+  char *subvol;
+  grub_uint64_t tree;
+};
+
+typedef struct grub_btrfs_mtab* grub_btrfs_mtab_t;
+
+static struct grub_btrfs_mtab *btrfs_mtab;
+
+#define FOR_GRUB_MTAB(var) FOR_LIST_ELEMENTS (var, btrfs_mtab)
+#define FOR_GRUB_MTAB_SAFE(var, next) FOR_LIST_ELEMENTS_SAFE((var), (next), btrfs_mtab)
+
+static void
+add_mountpoint (const char *path, const char *subvol, grub_uint64_t tree)
+{
+  grub_btrfs_mtab_t m = grub_malloc (sizeof (*m));
+
+  m->path = grub_strdup (path);
+  m->subvol = grub_strdup (subvol);
+  m->tree = tree;
+  grub_list_push (GRUB_AS_LIST_P (&btrfs_mtab), GRUB_AS_LIST (m));
+}
+
+static grub_err_t
+grub_cmd_btrfs_mount_subvol (grub_command_t cmd __attribute__ ((unused)), int argc,
+		     char **argv)
+{
+  char *devname, *dirname, *subvol;
+  struct grub_btrfs_key key_in;
+  grub_uint8_t type;
+  grub_uint64_t tree;
+  grub_uint64_t saved_tree;
+  grub_err_t err;
+  struct grub_btrfs_data *data = NULL;
+  grub_device_t dev = NULL;
+
+  if (argc < 3)
+    return grub_error (GRUB_ERR_BAD_ARGUMENT, "required <dev> <dir> and <subvol>");
+
+  devname = grub_file_get_device_name(argv[0]);
+  dev = grub_device_open (devname);
+  grub_free (devname);
+
+  if (!dev)
+    {
+      err = grub_errno;
+      goto err_out;
+    }
+
+  dirname = argv[1];
+  subvol = argv[2];
+
+  data = grub_btrfs_mount (dev);
+  if (!data)
+    {
+      err = grub_errno;
+      goto err_out;
+    }
+
+  err = find_path (data, dirname, &key_in, &tree, &type);
+  if (err)
+    goto err_out;
+
+  if (type !=  GRUB_BTRFS_DIR_ITEM_TYPE_DIRECTORY)
+    {
+      err = grub_error (GRUB_ERR_BAD_FILE_TYPE, N_("not a directory"));
+      goto err_out;
+    }
+
+  err = get_root (data, &key_in, &tree, &type);
+
+  if (err)
+    goto err_out;
+
+  saved_tree = data->fs_tree;
+  data->fs_tree = tree;
+  err = find_path (data, subvol, &key_in, &tree, &type);
+  data->fs_tree = saved_tree;
+
+  if (err)
+    goto err_out;
+
+  if (key_in.object_id != grub_cpu_to_le64_compile_time (GRUB_BTRFS_OBJECT_ID_CHUNK) || tree == 0)
+    {
+      err = grub_error (GRUB_ERR_BAD_FILE_TYPE, "%s: not a subvolume\n", subvol);
+      goto err_out;
+    }
+
+  grub_btrfs_unmount (data);
+  grub_device_close (dev);
+  add_mountpoint (dirname, subvol, tree);
+
+  return GRUB_ERR_NONE;
+
+err_out:
+
+  if (data)
+    grub_btrfs_unmount (data);
+
+  if (dev)
+    grub_device_close (dev);
+
+  return err;
+}
+
+grub_uint64_t
+find_mtab_subvol_tree (const char *path, char **path_in_subvol)
+{
+  grub_btrfs_mtab_t m, cm;
+  grub_uint64_t tree;
+
+  if (!path || !path_in_subvol)
+    return 0;
+
+  *path_in_subvol = NULL;
+  tree = 0;
+  cm = NULL;
+
+  FOR_GRUB_MTAB (m)
+    {
+      if (grub_strncmp (path, m->path, grub_strlen (m->path)) == 0)
+	{
+	  if (!cm)
+	    cm = m;
+	  else
+	    if (grub_strcmp (m->path, cm->path) > 0)
+	      cm = m;
+	}
+    }
+
+  if (cm)
+    {
+      const char *s = path + grub_strlen (cm->path);
+      *path_in_subvol = (s[0] == '\0') ? grub_strdup ("/") : grub_strdup (s);
+      tree = cm->tree;
+    }
+
+  return tree;
+}
+
 static grub_err_t
 get_fs_root(struct grub_btrfs_data *data, grub_uint64_t tree,
             grub_uint64_t objectid, grub_uint64_t offset,
@@ -2903,6 +3090,7 @@
 };
 
 static grub_command_t cmd_info;
+static grub_command_t cmd_mount_subvol;
 static grub_extcmd_t cmd_list_subvols;
 
 static char *
@@ -2966,6 +3154,9 @@
   cmd_info = grub_register_command("btrfs-info", grub_cmd_btrfs_info,
 				   "DEVICE",
 				   "Print BtrFS info about DEVICE.");
+  cmd_mount_subvol = grub_register_command("btrfs-mount-subvol", grub_cmd_btrfs_mount_subvol,
+				   "DEVICE DIRECTORY SUBVOL",
+				   "Set btrfs DEVICE the DIRECTORY a mountpoint of SUBVOL.");
   cmd_list_subvols = grub_register_extcmd("btrfs-list-subvols",
 					 grub_cmd_btrfs_list_subvols, 0,
 					 "[-p|-n] [-o var] DEVICE",
--- a/grub-core/osdep/linux/getroot.c
+++ b/grub-core/osdep/linux/getroot.c
@@ -103,6 +103,14 @@
   grub_uint32_t unused[9];
 };
 
+struct btrfs_ioctl_search_header {
+  grub_uint64_t transid;
+  grub_uint64_t objectid;
+  grub_uint64_t offset;
+  grub_uint32_t type;
+  grub_uint32_t len;
+};
+
 struct btrfs_ioctl_search_args {
   struct btrfs_ioctl_search_key key;
   grub_uint64_t buf[(4096 - sizeof(struct btrfs_ioctl_search_key))
@@ -375,6 +383,109 @@
 
 int use_relative_path_on_btrfs = 0;
 
+static char *
+get_btrfs_subvol (const char *path)
+{
+  struct btrfs_ioctl_ino_lookup_args args;
+  grub_uint64_t tree_id;
+  int fd = -1;
+  char *ret = NULL;
+
+  fd = open (path, O_RDONLY);
+
+  if (fd < 0)
+    return NULL;
+
+  memset (&args, 0, sizeof(args));
+  args.objectid = GRUB_BTRFS_TREE_ROOT_OBJECTID;
+
+  if (ioctl (fd, BTRFS_IOC_INO_LOOKUP, &args) < 0)
+    goto error;
+
+  tree_id = args.treeid;
+
+  while (tree_id != GRUB_BTRFS_ROOT_VOL_OBJECTID)
+    {
+      struct btrfs_ioctl_search_args sargs;
+      struct grub_btrfs_root_backref *br;
+      struct btrfs_ioctl_search_header *search_header;
+      char *old;
+      grub_uint16_t len;
+      grub_uint64_t inode_id;
+
+      memset (&sargs, 0, sizeof(sargs));
+
+      sargs.key.tree_id = 1;
+      sargs.key.min_objectid = tree_id;
+      sargs.key.max_objectid = tree_id;
+
+      sargs.key.min_offset = 0;
+      sargs.key.max_offset = ~0ULL;
+      sargs.key.min_transid = 0;
+      sargs.key.max_transid = ~0ULL;
+      sargs.key.min_type = GRUB_BTRFS_ITEM_TYPE_ROOT_BACKREF;
+      sargs.key.max_type = GRUB_BTRFS_ITEM_TYPE_ROOT_BACKREF;
+
+      sargs.key.nr_items = 1;
+
+      if (ioctl (fd, BTRFS_IOC_TREE_SEARCH, &sargs) < 0)
+	goto error;
+
+      if (sargs.key.nr_items == 0)
+	goto error;
+
+      search_header = (struct btrfs_ioctl_search_header *)sargs.buf;
+      br = (struct grub_btrfs_root_backref *) (search_header + 1);
+
+      len = grub_le_to_cpu16 (br->n);
+      inode_id = grub_le_to_cpu64 (br->inode_id);
+      tree_id = search_header->offset;
+
+      old = ret;
+      ret = malloc (len + 1);
+      memcpy (ret, br->name, len);
+      ret[len] = '\0';
+
+      if (inode_id != GRUB_BTRFS_TREE_ROOT_OBJECTID)
+	{
+	  char *s;
+
+	  memset(&args, 0, sizeof(args));
+	  args.treeid = search_header->offset;
+	  args.objectid = inode_id;
+
+	  if (ioctl (fd, BTRFS_IOC_INO_LOOKUP, &args) < 0)
+	    goto error;
+
+	  s = xasprintf ("%s%s", args.name, ret);
+	  free (ret);
+	  ret = s;
+	}
+
+      if (old)
+	{
+	  char *s = xasprintf ("%s/%s", ret, old);
+	  free (ret);
+	  free (old);
+	  ret = s;
+	}
+    }
+
+  close (fd);
+  return ret;
+
+error:
+
+  if (fd >= 0)
+    close (fd);
+  if (ret)
+    free (ret);
+
+  return NULL;
+}
+
+static char *grub_btrfs_mount_path;
+
 char **
 grub_find_root_devices_from_mountinfo (const char *dir, char **relroot)
 {
@@ -516,12 +627,17 @@
       else if (grub_strcmp (entries[i].fstype, "btrfs") == 0)
 	{
 	  ret = grub_find_root_devices_from_btrfs (dir);
-	  fs_prefix = get_btrfs_fs_prefix (entries[i].enc_path);
 	  if (use_relative_path_on_btrfs)
 	    {
-	      if (fs_prefix)
-	        free (fs_prefix);
 	      fs_prefix = xstrdup ("/");
+
+	      if (grub_btrfs_mount_path)
+		grub_free (grub_btrfs_mount_path);
+	      grub_btrfs_mount_path = grub_strdup (entries[i].enc_path);
+	    }
+	  else
+	    {
+	      fs_prefix = get_btrfs_fs_prefix (entries[i].enc_path);
 	    }
 	}
       else if (!retry && grub_strcmp (entries[i].fstype, "autofs") == 0)
@@ -1202,6 +1318,24 @@
   return grub_dev;
 }
 
+
+char *
+grub_util_get_btrfs_subvol (const char *path, char **mount_path)
+{
+  if (mount_path)
+    *mount_path = NULL;
+
+  grub_free (grub_find_root_devices_from_mountinfo (path, NULL));
+
+  if (!grub_btrfs_mount_path)
+    return NULL;
+
+  if (mount_path)
+    *mount_path = grub_strdup (grub_btrfs_mount_path);
+
+  return get_btrfs_subvol (grub_btrfs_mount_path);
+}
+
 char *
 grub_make_system_path_relative_to_its_root_os (const char *path)
 {
--- a/util/grub-install.c
+++ b/util/grub-install.c
@@ -1645,6 +1645,58 @@
       prefix_drive = xasprintf ("(%s)", grub_drives[0]);
     }
 
+#ifdef __linux__
+
+  if (config.is_suse_btrfs_snapshot_enabled
+      && grub_strncmp(grub_fs->name, "btrfs", sizeof ("btrfs") - 1) == 0)
+    {
+      char *subvol = NULL;
+      char *mount_path = NULL;
+      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);
+
+      if (subvol && mount_path)
+	{
+	  char *def_subvol;
+
+	  def_subvol = grub_util_get_btrfs_subvol (rootdir_path, NULL);
+
+	  if (def_subvol)
+	    {
+	      char *rootdir_mount_path = NULL;
+	      if (!load_cfg_f)
+		load_cfg_f = grub_util_fopen (load_cfg, "wb");
+	      have_load_cfg = 1;
+
+	      if (grub_strncmp (rootdir_path, mount_path, grub_strlen (rootdir_path)) == 0)
+		rootdir_mount_path = grub_util_path_concat (2, "/", mount_path + grub_strlen (rootdir_path));
+
+	      if (grub_strcmp (subvol, def_subvol) != 0 && rootdir_mount_path)
+		fprintf (load_cfg_f, "btrfs-mount-subvol ($root) %s %s\n", rootdir_mount_path, subvol);
+	      free (rootdir_mount_path);
+	      free (def_subvol);
+	    }
+	}
+
+      free (t);
+      free (rootdir_path);
+      for (curdev = rootdir_devices; *curdev; curdev++)
+	free (*curdev);
+      free (rootdir_devices);
+      free (subvol);
+      free (mount_path);
+    }
+
+#endif
+
   char mkimage_target[200];
   const char *core_name = NULL;
 
--- a/include/grub/emu/getroot.h
+++ b/include/grub/emu/getroot.h
@@ -53,6 +53,11 @@
 grub_find_root_devices_from_mountinfo (const char *dir, char **relroot);
 #endif
 
+#ifdef __linux__
+char *
+grub_util_get_btrfs_subvol (const char *path, char **mount_path);
+#endif
+
 /* Devmapper functions provided by getroot_devmapper.c.  */
 void
 grub_util_pull_devmapper (const char *os_dev);