Messages in this thread | | | From | Linus Torvalds <> | Date | Fri, 25 Sep 2020 18:15:37 -0700 | Subject | Re: [PATCH 1/5] mm: Introduce mm_struct.has_pinned |
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On Fri, Sep 25, 2020 at 5:41 PM Jason Gunthorpe <jgg@ziepe.ca> wrote: > > I don't completely grok the consequences of the anon_vma check. We > can exclude file backed mappings as they are broken for pinning > anyhow, so what is left that could be MAP_PRIVATE of a non-anon_vma?
It really shouldn't ever happen.
The only way a COW vma can have a NULL anon_vma should be if it has no pages mapped at all.
Technically I think it could happen if you only ever mapped the special zero page in there (but that shouldn't then get to the "vm_normal_page()").
> Otherwise, I do prefer Peter's version because of the GFP_KERNEL. To > touch on your other email..
Yeah, no, I just hadn't seen a new version, so I started getting antsy and that's when I decided to see what a minimal patch looks like.
I think that over the weekend I'll do Peter's version but with the "page_mapcount() == 1" check, because I'm starting to like that better than the mm->has_pinned.
Comments on that plan?
Linus
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