mm: hugetlb: add missing cache flushing in hugetlb_unshare_all_pmds()

Missed calling flush_cache_range() before removing the sharing PMD
entrires, otherwise data consistence issue may be occurred on some
architectures whose caches are strict and require a virtual>physical
translation to exist for a virtual address.  Thus add it.

Now no architectures enabling PMD sharing will be affected, since they do
not have a VIVT cache.  That means this issue can not be happened in
practice so far.

Link: https://lkml.kernel.org/r/47441086affcabb6ecbe403173e9283b0d904b38.1650956489.git.baolin.wang@linux.alibaba.com
Link: https://lkml.kernel.org/r/419b0e777c9e6d1454dcd906e0f5b752a736d335.1650781755.git.baolin.wang@linux.alibaba.com
Fixes: 6dfeaff93be1 ("hugetlb/userfaultfd: unshare all pmds for hugetlbfs when register wp")
Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 4ab62657acda4a35c4b5d9a471a316f6ac5f3dcf..4e017940b26f62e63037a4f7fe237968d2097a20 100644 (file)
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -6886,6 +6886,7 @@ void hugetlb_unshare_all_pmds(struct vm_area_struct *vma)
        if (start >= end)
                return;
 
+       flush_cache_range(vma, start, end);
        /*
         * No need to call adjust_range_if_pmd_sharing_possible(), because
         * we have already done the PUD_SIZE alignment.