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Message-ID: <ZUuUVDbiWETJ2OU1@casper.infradead.org>
Date: Wed, 8 Nov 2023 13:59:48 +0000
From: Matthew Wilcox <willy@...radead.org>
To: Kefeng Wang <wangkefeng.wang@...wei.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
linux-kernel@...r.kernel.org, linux-mm@...ck.org,
David Hildenbrand <david@...hat.com>
Subject: Re: [PATCH 1/6] mm: ksm: use more folio api in
ksm_might_need_to_copy()
On Wed, Nov 08, 2023 at 09:40:09AM +0800, Kefeng Wang wrote:
>
>
> On 2023/11/7 22:24, Matthew Wilcox wrote:
> > On Tue, Nov 07, 2023 at 09:52:11PM +0800, Kefeng Wang wrote:
> > > struct page *ksm_might_need_to_copy(struct page *page,
> > > - struct vm_area_struct *vma, unsigned long address)
> > > + struct vm_area_struct *vma, unsigned long addr)
> > > {
> > > struct folio *folio = page_folio(page);
> > > struct anon_vma *anon_vma = folio_anon_vma(folio);
> > > - struct page *new_page;
> > > + struct folio *new_folio;
> > > - if (PageKsm(page)) {
> > > - if (page_stable_node(page) &&
> > > + if (folio_test_ksm(folio)) {
> > > + if (folio_stable_node(folio) &&
> > > !(ksm_run & KSM_RUN_UNMERGE))
> > > return page; /* no need to copy it */
> > > } else if (!anon_vma) {
> > > return page; /* no need to copy it */
> > > - } else if (page->index == linear_page_index(vma, address) &&
> > > + } else if (page->index == linear_page_index(vma, addr) &&
> >
> > Hmm. page->index is going away. What should we do here instead?
>
> Do you mean to replace page->index to folio->index, or kill index from
> struct page?
I'm asking you what we should do.
Tail pages already don't have a valid ->index (or ->mapping).
So presumably we can't see a tail page here today. But will we in future?
Just to remind you, the goal here is:
struct page {
unsigned long memdesc;
};
so folios will be the only thing that have a ->index. I haven't looked
at this code; I know nothing about it. But you're changing it, so you
must have some understanding of it.
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