From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001

From: Michael Chang <mchang@suse.com>

Date: Thu, 11 May 2017 08:56:57 +0000

Subject: [PATCH] Grub not working correctly with btrfs snapshots (bsc#1026511)

---

 grub-core/fs/btrfs.c | 238 +++++++++++++++++++++++++++++++++++++++++++++++++++

 1 file changed, 238 insertions(+)

diff --git a/grub-core/fs/btrfs.c b/grub-core/fs/btrfs.c

index 4a31d39ee..7002ad81b 100644

--- a/grub-core/fs/btrfs.c

+++ b/grub-core/fs/btrfs.c

@@ -2446,6 +2446,238 @@ out:

   return 0;

 }

+static grub_err_t

+grub_btrfs_get_parent_subvol_path (struct grub_btrfs_data *data,

+		grub_uint64_t child_id,

+		const char *child_path,

+		grub_uint64_t *parent_id,

+		char **path_out)

+{

+  grub_uint64_t fs_root = 0;

+  struct grub_btrfs_key key_in = {

+    .object_id = child_id,

+    .type = GRUB_BTRFS_ITEM_TYPE_ROOT_BACKREF,

+    .offset = 0,

+  }, key_out;

+  struct grub_btrfs_root_ref *ref;

+  char *buf;

+  struct grub_btrfs_leaf_descriptor desc;

+  grub_size_t elemsize;

+  grub_disk_addr_t elemaddr;

+  grub_err_t err;

+  char *parent_path;

+

+  *parent_id = 0;

+  *path_out = 0;

+

+  err = lower_bound(data, &key_in, &key_out, data->sblock.root_tree,

+                    &elemaddr, &elemsize, &desc, 0);

+  if (err)

+    return err;

+

+  if (key_out.type != GRUB_BTRFS_ITEM_TYPE_ROOT_BACKREF || elemaddr == 0)

+    next(data, &desc, &elemaddr, &elemsize, &key_out);

+

+  if (key_out.type != GRUB_BTRFS_ITEM_TYPE_ROOT_BACKREF)

+    {

+      free_iterator(&desc);

+      return grub_error(GRUB_ERR_FILE_NOT_FOUND, N_("can't find root backrefs"));

+    }

+

+  buf = grub_malloc(elemsize + 1);

+  if (!buf)

+    {

+      free_iterator(&desc);

+      return grub_errno;

+    }

+

+  err = grub_btrfs_read_logical(data, elemaddr, buf, elemsize, 0);

+  if (err)

+    {

+      grub_free(buf);

+      free_iterator(&desc);

+      return err;

+    }

+

+  buf[elemsize] = 0;

+  ref = (struct grub_btrfs_root_ref *)buf;

+

+  err = get_fs_root(data, data->sblock.root_tree, grub_le_to_cpu64 (key_out.offset),

+                    0, &fs_root);

+  if (err)

+    {

+      grub_free(buf);

+      free_iterator(&desc);

+      return err;

+    }

+

+  find_pathname(data, grub_le_to_cpu64 (ref->dirid), fs_root, ref->name, &parent_path);

+

+  if (child_path)

+    {

+      *path_out = grub_xasprintf ("%s/%s", parent_path, child_path);

+      grub_free (parent_path);

+    }

+  else

+    *path_out = parent_path;

+

+  *parent_id = grub_le_to_cpu64 (key_out.offset);

+

+  grub_free(buf);

+  free_iterator(&desc);

+  return GRUB_ERR_NONE;

+}

+

+static grub_err_t

+grub_btrfs_get_default_subvolume_id (struct grub_btrfs_data *data, grub_uint64_t *id)

+{

+  grub_err_t err;

+  grub_disk_addr_t elemaddr;

+  grub_size_t elemsize;

+  struct grub_btrfs_key key, key_out;

+  struct grub_btrfs_dir_item *direl = NULL;

+  const char *ctoken = "default";

+  grub_size_t ctokenlen = sizeof ("default") - 1;

+

+  *id = 0;

+  key.object_id = data->sblock.root_dir_objectid;

+  key.type = GRUB_BTRFS_ITEM_TYPE_DIR_ITEM;

+  key.offset = grub_cpu_to_le64 (~grub_getcrc32c (1, ctoken, ctokenlen));

+  err = lower_bound (data, &key, &key_out, data->sblock.root_tree, &elemaddr, &elemsize,

+			 NULL, 0);

+  if (err)

+    return err;

+

+  if (key_cmp (&key, &key_out) != 0)

+    return grub_error (GRUB_ERR_FILE_NOT_FOUND, N_("file not found"));

+

+  struct grub_btrfs_dir_item *cdirel;

+  direl = grub_malloc (elemsize + 1);

+  err = grub_btrfs_read_logical (data, elemaddr, direl, elemsize, 0);

+  if (err)

+    {

+      grub_free (direl);

+      return err;

+    }

+  for (cdirel = direl;

+       (grub_uint8_t *) cdirel - (grub_uint8_t *) direl

+       < (grub_ssize_t) elemsize;

+       cdirel = (void *) ((grub_uint8_t *) (direl + 1)

+       + grub_le_to_cpu16 (cdirel->n)

+       + grub_le_to_cpu16 (cdirel->m)))

+    {

+      if (ctokenlen == grub_le_to_cpu16 (cdirel->n)

+        && grub_memcmp (cdirel->name, ctoken, ctokenlen) == 0)

+      break;

+    }

+  if ((grub_uint8_t *) cdirel - (grub_uint8_t *) direl

+      >= (grub_ssize_t) elemsize)

+    {

+      grub_free (direl);

+      err = grub_error (GRUB_ERR_FILE_NOT_FOUND, N_("file not found"));

+      return err;

+    }

+

+  if (cdirel->key.type != GRUB_BTRFS_ITEM_TYPE_ROOT_ITEM)

+    {

+      grub_free (direl);

+      err = grub_error (GRUB_ERR_FILE_NOT_FOUND, N_("file not found"));

+      return err;

+    }

+

+  *id = grub_le_to_cpu64 (cdirel->key.object_id);

+  return GRUB_ERR_NONE;

+}

+

+static grub_err_t

+grub_cmd_btrfs_get_default_subvol (struct grub_extcmd_context *ctxt,

+			     int argc, char **argv)

+{

+  char *devname;

+  grub_device_t dev;

+  struct grub_btrfs_data *data;

+  grub_err_t err;

+  grub_uint64_t id;

+  char *subvol = NULL;

+  grub_uint64_t subvolid = 0;

+  char *varname = NULL;

+  char *output = NULL;

+  int path_only = ctxt->state[1].set;

+  int num_only = ctxt->state[2].set;

+

+  if (ctxt->state[0].set)

+    varname = ctxt->state[0].arg;

+

+  if (argc < 1)

+    return grub_error (GRUB_ERR_BAD_ARGUMENT, "device name required");

+

+  devname = grub_file_get_device_name(argv[0]);

+  if (!devname)

+    return grub_errno;

+

+  dev = grub_device_open (devname);

+  grub_free (devname);

+  if (!dev)

+    return grub_errno;

+

+  data = grub_btrfs_mount(dev);

+  if (!data)

+    {

+      grub_device_close (dev);

+      grub_dprintf ("btrfs", "failed to open fs\n");

+      grub_errno = GRUB_ERR_NONE;

+      return 0;

+    }

+

+  err = grub_btrfs_get_default_subvolume_id (data, &subvolid);

+  if (err)

+    {

+      grub_btrfs_unmount (data);

+      grub_device_close (dev);

+      return err;

+    }

+

+  id = subvolid;

+  while (id != GRUB_BTRFS_ROOT_VOL_OBJECTID)

+    {

+      grub_uint64_t parent_id;

+      char *path_out;

+

+      err = grub_btrfs_get_parent_subvol_path (data, grub_cpu_to_le64 (id), subvol, &parent_id, &path_out);

+      if (err)

+	{

+	  grub_btrfs_unmount (data);

+	  grub_device_close (dev);

+	  return err;

+	}

+

+      if (subvol)

+        grub_free (subvol);

+      subvol = path_out;

+      id = parent_id;

+    }

+

+  if (num_only && path_only)

+      output = grub_xasprintf ("%"PRIuGRUB_UINT64_T" /%s", subvolid, subvol);

+  else if (num_only)

+      output = grub_xasprintf ("%"PRIuGRUB_UINT64_T, subvolid);

+  else

+      output = grub_xasprintf ("/%s", subvol);

+

+  if (varname)

+    grub_env_set(varname, output);

+  else

+    grub_printf ("%s\n", output);

+

+  grub_free (output);

+  grub_free (subvol);

+

+  grub_btrfs_unmount (data);

+  grub_device_close (dev);

+

+  return GRUB_ERR_NONE;

+}

+

 static struct grub_fs grub_btrfs_fs = {

   .name = "btrfs",

   .dir = grub_btrfs_dir,

@@ -2464,6 +2696,7 @@ static struct grub_fs grub_btrfs_fs = {

 static grub_command_t cmd_info;

 static grub_command_t cmd_mount_subvol;

 static grub_extcmd_t cmd_list_subvols;

+static grub_extcmd_t cmd_get_default_subvol;

 static char *

 subvolid_set_env (struct grub_env_var *var __attribute__ ((unused)),

@@ -2534,6 +2767,11 @@ GRUB_MOD_INIT (btrfs)

 					 "[-p|-n] [-o var] DEVICE",

 					 "Print list of BtrFS subvolumes on "

 					 "DEVICE.", options);

+  cmd_get_default_subvol = grub_register_extcmd("btrfs-get-default-subvol",

+					 grub_cmd_btrfs_get_default_subvol, 0,

+					 "[-p|-n] [-o var] DEVICE",

+					 "Print default BtrFS subvolume on "

+					 "DEVICE.", options);

   grub_register_variable_hook ("btrfs_subvol", subvol_get_env,

                                subvol_set_env);

   grub_register_variable_hook ("btrfs_subvolid", subvolid_get_env,