vfs: make vfs_mknod break delegations on parent directory

vfs: make vfs_mknod break delegations on parent directory

In order to add directory delegation support, we need to break
delegations on the parent whenever there is going to be a change in the
directory.

Add a new delegated_inode pointer to vfs_mknod() and have the
appropriate callers wait when there is an outstanding delegation. All
other callers just set the pointer to NULL.

Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: NeilBrown <neil@brown.name>
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Link: https://patch.msgid.link/20251111-dir-deleg-ro-v6-11-52f3feebb2f2@kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>