On 8/15/24 1:13 AM, Matthew Wilcox wrote: > On Tue, Jul 30, 2024 at 02:46:54PM +0800, alexs@xxxxxxxxxx wrote: >> We have struct ptdesc for page table descriptor a year ago, but it >> has no much usages in kernel, while pgtable_t is used widely. > > Hum, I thought I responded to this to point out the problem, but > I don't see the response anywhere, so I'll try again. > >> The pgtable_t is typedefed as 'pte_t *' in sparc, s390, powerpc and m68k >> except SUN3, others archs are all same as 'struct page *'. > > And there's a very good reason for that. On s390 and powerpc (I cannot > speak to the sparc/m68k), each page table is (potentially) smaller > than PAGE_SIZE. So we cannot do what your patch purports to do, as > we would not know whether we're referring to the first or subsequent > page tables contained within a page. >> Maybe at some point in the distant future we'll be able to allocate > a ptdesc per page table instead of per page allocated for use by page > tables. But we cannot do that yet. Got it. Thanks a lot for the info!
