Re: [PATCH] fs: allow do_renameat2() over bind mounts of the same filesystem.

[Al Viro]

On Fri, Aug 28, 2020 at 10:40:35PM +0200, Florian Margaine wrote:
> There's currently this seemingly unnecessary limitation that rename()
> cannot work over bind mounts of the same filesystem,

... is absolutely deliberate - that's how you set a boundary in the
tree, preventing both links and renames across it.

Incidentally, doing that would have fun effects for anyone with current
directory inside the subtree you'd moved - try and see.