On Fri, Jul 26, 2019 at 03:47:02PM -0700, Linus Torvalds wrote:
> Of course, then later on, commit 20284ab7427f ("switch mount_capable()
> to fs_context") drops that argument entirely, and hardcodes the
> decision to look at fc->global.
>
> But that fc->global decision wasn't there originally, and is incorrect
> since it breaks existing users.
>
> What gets much more confusing about this is that the two different
> users then moved around. The sget_userns() case got moved to
> legacy_get_tree(), and then joined together in vfs_get_tree(), and
> then split and moved out to do_new_mount() and vfs_fsconfig_locked().
>
> And that "joined together into vfs_get_tree()" must be wrong, because
> the two cases used two different namespace rules. The sget_userns()
> case *did* have that "global" flag check, while the sget_fc() did not.
>
> Messy. Al?
Digging through that mess... It's my fuckup, and we obviously need to
restore the old behaviour, but I really hope to manage that with
checks _not_ in superblock allocator ;-/
