Re: [PATCH] Btrfs: Intialize btrfs_root->highest_objectid when loading tree root and subvolume roots

[Chandan Rajendra <chandan@linux.vnet.ibm.com>]

On Tuesday 05 Jan 2016 13:12:34 David Sterba wrote:
> Sorry for not answering that. As you're going to resend it, please
> use EOVERFLOW in the btrfs_init_fs_root. We should not hit the overflow
> error in the mount path.
Right. Now I understand that.

David, Replacing the following code snippet instances (in both open_ctree()
and btrfs_init_fs_root()) ...

        if (unlikely(root->highest_objectid >= BTRFS_LAST_FREE_OBJECTID)) {
                mutex_unlock(&root->objectid_mutex);
                ret = -EOVERFLOW;
                goto free_root_dev;
        }

with ....

     ASSERT(tree_root->highest_objectid <= BTRFS_LAST_FREE_OBJECTID);

is probably a better option?

The validation of root->highest_objectid must have been done by
btrfs_find_free_objectid() when creating the subvolume. If the parent
subvolume already has an objectid with BTRFS_LAST_FREE_OBJECTID as the value,
btrfs_find_free_objectid() would return with an error and hence we should
never have subvolumes containing other subvolumes with objectid greater than
BTRFS_LAST_FREE_OBJECTID.

-- 
chandan