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| author | Peter Xu <peterx@redhat.com> | 2022-05-13 06:22:53 +0300 |
|---|---|---|
| committer | Andrew Morton <akpm@linux-foundation.org> | 2022-05-13 17:20:10 +0300 |
| commit | 019c2d8b959c9c18b04572f9c26c46be9f5df093 (patch) | |
| tree | c59e0f09273766e3af38f5ba5d2c62d1e6b43bc2 /mm | |
| parent | fe2567eb552194e5b7a3c61bed5574658f859a11 (diff) | |
| download | linux-019c2d8b959c9c18b04572f9c26c46be9f5df093.tar.xz | |
mm/shmem: allows file-back mem to be uffd wr-protected on thps
We don't have "huge" version of pte markers, instead when necessary we
split the thp.
However split the thp is not enough, because file-backed thp is handled
totally differently comparing to anonymous thps: rather than doing a real
split, the thp pmd will simply got cleared in __split_huge_pmd_locked().
That is not enough if e.g. when there is a thp covers range [0, 2M) but
we want to wr-protect small page resides in [4K, 8K) range, because after
__split_huge_pmd() returns, there will be a none pmd, and
change_pmd_range() will just skip it right after the split.
Here we leverage the previously introduced change_pmd_prepare() macro so
that we'll populate the pmd with a pgtable page after the pmd split (in
which process the pmd will be cleared for cases like shmem). Then
change_pte_range() will do all the rest for us by installing the uffd-wp
pte marker at any none pte that we'd like to wr-protect.
Link: https://lkml.kernel.org/r/20220405014852.14413-1-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: "Kirill A . Shutemov" <kirill@shutemov.name>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Nadav Amit <nadav.amit@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'mm')
| -rw-r--r-- | mm/mprotect.c | 9 |
1 files changed, 8 insertions, 1 deletions
diff --git a/mm/mprotect.c b/mm/mprotect.c index 763409e62ef6..cccad7974b3b 100644 --- a/mm/mprotect.c +++ b/mm/mprotect.c @@ -338,8 +338,15 @@ static inline unsigned long change_pmd_range(struct mmu_gather *tlb, } if (is_swap_pmd(*pmd) || pmd_trans_huge(*pmd) || pmd_devmap(*pmd)) { - if (next - addr != HPAGE_PMD_SIZE) { + if ((next - addr != HPAGE_PMD_SIZE) || + uffd_wp_protect_file(vma, cp_flags)) { __split_huge_pmd(vma, pmd, addr, false, NULL); + /* + * For file-backed, the pmd could have been + * cleared; make sure pmd populated if + * necessary, then fall-through to pte level. + */ + change_pmd_prepare(vma, pmd, cp_flags); } else { /* * change_huge_pmd() does not defer TLB flushes, |