Messages in this thread | | | Date | Tue, 30 Apr 2024 09:36:05 -0400 | From | Peter Xu <> | Subject | Re: [PATCH v1] selftests: mm: gup_longterm: test unsharing logic when R/O pinning |
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On Tue, Apr 30, 2024 at 03:15:08PM +0200, David Hildenbrand wrote: > In our FOLL_LONGTERM tests, we prefault the page tables for the GUP-fast > test cases to be able to find a PTE and exercise the "longterm pinning > allowed" logic on the GUP-fast path where possible. > > For now, we always prefault the page tables writable, resulting in PTEs > that are writable. > > Let's cover more cases to also test if our unsharing logic works as > expected (and is able to make progress when there is nothing to unshare) > by mprotect'ing the range R/O when R/O-pinning, so we don't get PTEs > that are writable. > > This change would have found an issue introduced by commit a12083d721d7 > ("mm/gup: handle hugepd for follow_page()"), whereby R/O pinning was not > able to make progress in all cases, because unsharing logic was not > provided with the VMA to decide at some point that long-term R/O pinning > a !anon page is fine. > > Cc: Andrew Morton <akpm@linux-foundation.org> > Cc: Shuah Khan <shuah@kernel.org> > Cc: Peter Xu <peterx@redhat.com> > Signed-off-by: David Hildenbrand <david@redhat.com>
Acked-by: Peter Xu <peterx@redhat.com>
Thanks,
-- Peter Xu
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