Messages in this thread | | | Date | Mon, 29 Apr 2024 14:22:53 +0200 | Subject | Re: [PATCH v1] fs/proc/task_mmu: Fix uffd-wp confusion in pagemap_scan_pmd_entry() | From | David Hildenbrand <> |
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On 29.04.24 13:41, Ryan Roberts wrote: > pagemap_scan_pmd_entry() checks if uffd-wp is set on each pte to avoid > unnecessary if set. However it was previously checking with > `pte_uffd_wp(ptep_get(pte))` without first confirming that the pte was > present. It is only valid to call pte_uffd_wp() for present ptes. For > swap ptes, pte_swp_uffd_wp() must be called because the uffd-wp bit may > be kept in a different position, depending on the arch. > > This was leading to test failures in the pagemap_ioctl mm selftest, when > bringing up uffd-wp support on arm64 due to incorrectly interpretting > the uffd-wp status of migration entries. > > Let's fix this by using the correct check based on pte_present(). While > we are at it, let's pass the pte to make_uffd_wp_pte() to avoid the > pointless extra ptep_get() which can't be optimized out due to > READ_ONCE() on many arches. > > Closes: https://lore.kernel.org/linux-arm-kernel/ZiuyGXt0XWwRgFh9@x1n/ > Fixes: 12f6b01a0bcb ("fs/proc/task_mmu: add fast paths to get/clear PAGE_IS_WRITTEN flag") > Signed-off-by: Ryan Roberts <ryan.roberts@arm.com> > ---
Acked-by: David Hildenbrand <david@redhat.com>
-- Cheers,
David / dhildenb
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