Commit ad7df764 authored Sep 04, 2020 by Alistair Popple Committed by Linus Torvalds Sep 05, 2020

mm/rmap: fixup copying of soft dirty and uffd ptes



During memory migration a pte is temporarily replaced with a migration
swap pte.  Some pte bits from the existing mapping such as the soft-dirty
and uffd write-protect bits are preserved by copying these to the
temporary migration swap pte.

However these bits are not stored at the same location for swap and
non-swap ptes.  Therefore testing these bits requires using the
appropriate helper function for the given pte type.

Unfortunately several code locations were found where the wrong helper
function is being used to test soft_dirty and uffd_wp bits which leads to
them getting incorrectly set or cleared during page-migration.

Fix these by using the correct tests based on pte type.

Fixes: a5430dda ("mm/migrate: support un-addressable ZONE_DEVICE page in migration")
Fixes: 8c3328f1 ("mm/migrate: migrate_vma() unmap page from vma while collecting pages")
Fixes: f45ec5ff ("userfaultfd: wp: support swap and page migration")
Signed-off-by: Alistair Popple <alistair@popple.id.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Peter Xu <peterx@redhat.com>
Cc: Jérôme Glisse <jglisse@redhat.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Ralph Campbell <rcampbell@nvidia.com>
Cc: Alistair Popple <alistair@popple.id.au>
Cc: <stable@vger.kernel.org>
Link: https://lkml.kernel.org/r/20200825064232.10023-2-alistair@popple.id.au


Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent ebdf8321

mm/migrate.c

+11 −4

Original line number	Diff line number	Diff line
		@@ -2427,10 +2427,17 @@ again:
		entry = make_migration_entry(page, mpfn &
		MIGRATE_PFN_WRITE);
		swp_pte = swp_entry_to_pte(entry);
		if (pte_present(pte)) {
		if (pte_soft_dirty(pte))
		swp_pte = pte_swp_mksoft_dirty(swp_pte);
		if (pte_uffd_wp(pte))
		swp_pte = pte_swp_mkuffd_wp(swp_pte);
		} else {
		if (pte_swp_soft_dirty(pte))
		swp_pte = pte_swp_mksoft_dirty(swp_pte);
		if (pte_swp_uffd_wp(pte))
		swp_pte = pte_swp_mkuffd_wp(swp_pte);
		}
		set_pte_at(mm, addr, ptep, swp_pte);

		/*

mm/rmap.c

+7 −2

Original line number	Diff line number	Diff line
		@@ -1511,9 +1511,14 @@ static bool try_to_unmap_one(struct page page, struct vm_area_struct vma,
		*/
		entry = make_migration_entry(page, 0);
		swp_pte = swp_entry_to_pte(entry);
		if (pte_soft_dirty(pteval))

		/*
		* pteval maps a zone device page and is therefore
		* a swap pte.
		*/
		if (pte_swp_soft_dirty(pteval))
		swp_pte = pte_swp_mksoft_dirty(swp_pte);
		if (pte_uffd_wp(pteval))
		if (pte_swp_uffd_wp(pteval))
		swp_pte = pte_swp_mkuffd_wp(swp_pte);
		set_pte_at(mm, pvmw.address, pvmw.pte, swp_pte);
		/*

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