btrfs: tree-checker: Refactor root key check into separate function

ROOT_ITEM key check itself is not as simple as single line check, and
will be reused for both ROOT_ITEM and DIR_ITEM/DIR_INDEX location key
check, so refactor such check into check_root_key().

Also since we are here, fix a comment error about ROOT_ITEM offset,
which is transid of snapshot creation, not some "older kernel behavior".

Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/tree-checker.c b/fs/btrfs/tree-checker.c
index 285c362b31219a415786faefc6ffe6541cec82af..9fc438be4bd9364cf8b41c47f952a2659f30e1ac 100644 (file)
--- a/fs/btrfs/tree-checker.c
+++ b/fs/btrfs/tree-checker.c
@@ -428,6 +428,49 @@ static int check_inode_key(struct extent_buffer *leaf, struct btrfs_key *key,
        return 0;
 }
 
+static int check_root_key(struct extent_buffer *leaf, struct btrfs_key *key,
+                         int slot)
+{
+       struct btrfs_key item_key;
+       bool is_root_item;
+
+       btrfs_item_key_to_cpu(leaf, &item_key, slot);
+       is_root_item = (item_key.type == BTRFS_ROOT_ITEM_KEY);
+
+       /* No such tree id */
+       if (key->objectid == 0) {
+               if (is_root_item)
+                       generic_err(leaf, slot, "invalid root id 0");
+               else
+                       dir_item_err(leaf, slot,
+                                    "invalid location key root id 0");
+               return -EUCLEAN;
+       }
+
+       /* DIR_ITEM/INDEX/INODE_REF is not allowed to point to non-fs trees */
+       if (!is_fstree(key->objectid) && !is_root_item) {
+               dir_item_err(leaf, slot,
+               "invalid location key objectid, have %llu expect [%llu, %llu]",
+                               key->objectid, BTRFS_FIRST_FREE_OBJECTID,
+                               BTRFS_LAST_FREE_OBJECTID);
+               return -EUCLEAN;
+       }
+
+       /*
+        * ROOT_ITEM with non-zero offset means this is a snapshot, created at
+        * @offset transid.
+        * Furthermore, for location key in DIR_ITEM, its offset is always -1.
+        *
+        * So here we only check offset for reloc tree whose key->offset must
+        * be a valid tree.
+        */
+       if (key->objectid == BTRFS_TREE_RELOC_OBJECTID && key->offset == 0) {
+               generic_err(leaf, slot, "invalid root id 0 for reloc tree");
+               return -EUCLEAN;
+       }
+       return 0;
+}
+
 static int check_dir_item(struct extent_buffer *leaf,
                          struct btrfs_key *key, struct btrfs_key *prev_key,
                          int slot)
@@ -978,22 +1021,11 @@ static int check_root_item(struct extent_buffer *leaf, struct btrfs_key *key,
        struct btrfs_root_item ri;
        const u64 valid_root_flags = BTRFS_ROOT_SUBVOL_RDONLY |
                                     BTRFS_ROOT_SUBVOL_DEAD;
+       int ret;
 
-       /* No such tree id */
-       if (key->objectid == 0) {
-               generic_err(leaf, slot, "invalid root id 0");
-               return -EUCLEAN;
-       }
-
-       /*
-        * Some older kernel may create ROOT_ITEM with non-zero offset, so here
-        * we only check offset for reloc tree whose key->offset must be a
-        * valid tree.
-        */
-       if (key->objectid == BTRFS_TREE_RELOC_OBJECTID && key->offset == 0) {
-               generic_err(leaf, slot, "invalid root id 0 for reloc tree");
-               return -EUCLEAN;
-       }
+       ret = check_root_key(leaf, key, slot);
+       if (ret < 0)
+               return ret;
 
        if (btrfs_item_size_nr(leaf, slot) != sizeof(ri)) {
                generic_err(leaf, slot,