[PATCH 06/11] VFS: unify old_mnt_idmap and new_mnt_idmap in renamedata

[Al Viro]

On Tue, Aug 12, 2025 at 12:25:09PM +1000, NeilBrown wrote:
> A rename can only rename with a single mount.  Callers of vfs_rename()
> must and do ensure this is the case.
> 
> So there is no point in having two mnt_idmaps in renamedata as they are
> always the same.  Only of of them is passed to ->rename in any case.
> 
> This patch replaces both with a single "mnt_idmap" and changes all
> callers.

Looks sane and IMO should be reordered in front of the queue.