fs/btrfs/root.c

   1 // SPDX-License-Identifier: GPL-2.0+
   2 /*
   3  * BTRFS filesystem implementation for U-Boot
   4  *
   5  * 2017 Marek Behun, CZ.NIC, marek.behun@nic.cz
   6  */
   7
   8 #include "btrfs.h"
   9
  10 static void read_root_item(struct btrfs_path *p, struct btrfs_root_item *item)
  11 {
  12         u32 len;
  13         int reset = 0;
  14
  15         len = btrfs_path_item_size(p);
  16         memcpy(item, btrfs_path_item_ptr(p, struct btrfs_root_item), len);
  17         btrfs_root_item_to_cpu(item);
  18
  19         if (len < sizeof(*item))
  20                 reset = 1;
  21         if (!reset && item->generation != item->generation_v2) {
  22                 if (item->generation_v2 != 0)
  23                         printf("%s: generation != generation_v2 in root item",
  24                                __func__);
  25                 reset = 1;
  26         }
  27         if (reset) {
  28                 memset(&item->generation_v2, 0,
  29                        sizeof(*item) - offsetof(struct btrfs_root_item,
  30                                                 generation_v2));
  31         }
  32 }
  33
  34 int btrfs_find_root(u64 objectid, struct btrfs_root *root,
  35                     struct btrfs_root_item *root_item)
  36 {
  37         struct btrfs_path path;
  38         struct btrfs_root_item my_root_item;
  39
  40         if (!btrfs_search_tree_key_type(&btrfs_info.tree_root, objectid,
  41                                         BTRFS_ROOT_ITEM_KEY, &path))
  42                 return -1;
  43
  44         if (!root_item)
  45                 root_item = &my_root_item;
  46         read_root_item(&path, root_item);
  47
  48         if (root) {
  49                 root->objectid = objectid;
  50                 root->bytenr = root_item->bytenr;
  51                 root->root_dirid = root_item->root_dirid;
  52         }
  53
  54         btrfs_free_path(&path);
  55         return 0;
  56 }
  57
  58 u64 btrfs_lookup_root_ref(u64 subvolid, struct btrfs_root_ref *refp, char *name)
  59 {
  60         struct btrfs_path path;
  61         struct btrfs_key *key;
  62         struct btrfs_root_ref *ref;
  63         u64 res = -1ULL;
  64
  65         key = btrfs_search_tree_key_type(&btrfs_info.tree_root, subvolid,
  66                                                BTRFS_ROOT_BACKREF_KEY, &path);
  67
  68         if (!key)
  69                 return -1ULL;
  70
  71         ref = btrfs_path_item_ptr(&path, struct btrfs_root_ref);
  72         btrfs_root_ref_to_cpu(ref);
  73
  74         if (refp)
  75                 *refp = *ref;
  76
  77         if (name) {
  78                 if (ref->name_len > BTRFS_VOL_NAME_MAX) {
  79                         printf("%s: volume name too long: %u\n", __func__,
  80                                ref->name_len);
  81                         goto out;
  82                 }
  83
  84                 memcpy(name, ref + 1, ref->name_len);
  85         }
  86
  87         res = key->offset;
  88 out:
  89         btrfs_free_path(&path);
  90         return res;
  91 }
  92