Messages in this thread | ![/](/images/icornerl.gif) | | Subject | Re: [PATCH 2/2] mm: soft_dirty: userfaultfd: introduce wrprotect_tlb_flush_pending | From | John Hubbard <> | Date | Thu, 7 Jan 2021 14:37:35 -0800 |
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On 1/7/21 2:24 PM, Linus Torvalds wrote: > On Thu, Jan 7, 2021 at 2:20 PM Linus Torvalds > <torvalds@linux-foundation.org> wrote: >> >> Hmm, add a check for the page being PageAnon(), perhaps? >> >> If it's a shared vma, then the page can be pinned shared with multiple >> mappings, I agree. > > Or check the vma directly for whether it's a COW vma. That's probably > a more obvious test, but would have to be done outside of > page_maybe_dma_pinned(). > > For example, in copy_present_page(), we've already done that COW-vma > test, so if we want to strengthen just _that_ test, then it would be > sufficient to just add a > > /* This cannot be a pinned page if it has more than one mapping */ > if (page_mappings(page) != 1) > return 1; > > to copy_present_page() along with the existing page_maybe_dma_pinned() test. > > No? > > Linus
That approach makes me a lot happier, yes. Because it doesn't add constraints to the RDMA cases, but still does what we need here.
thanks, -- John Hubbard NVIDIA
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