On Sun, Jun 13, 2021 at 02:36:13PM +0530, Aneesh Kumar K.V wrote: > IIUC the reason why we do have pmd_pgtable() is that pgtable_t type > is arch dependent. On some architecture it is pte_t * and on the other > struct page *. The reason being highmem and level 4 page table can > be located in highmem.
That is ahistorical. See 2f569afd9ced9ebec9a6eb3dbf6f83429be0a7b4 -- we have pgtable_t for the benefit of s390's crazy sub-page page table sizes. Also, please stop numbering page tables upside down. PTEs are first level, not fourth.
