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Commit 7c342512 authored by Aneesh Kumar K.V's avatar Aneesh Kumar K.V Committed by Linus Torvalds
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mm/THP: use pmd_populate() to update the pmd with pgtable_t pointer 



We should not use set_pmd_at to update pmd_t with pgtable_t pointer.
set_pmd_at is used to set pmd with huge pte entries and architectures
like ppc64, clear few flags from the pte when saving a new entry.
Without this change we observe bad pte errors like below on ppc64 with
THP enabled.

  BUG: Bad page map in process ld mm=0xc000001ee39f4780 pte:7fc3f37848000001 pmd:c000001ec0000000

Signed-off-by: default avatarAneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Reviewed-by: default avatarAndrea Arcangeli <aarcange@redhat.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 7450231f

mm/huge_memory.c

+6 −1
Original line number Diff line number Diff line
@@ -2325,7 +2325,12 @@ static void collapse_huge_page(struct mm_struct *mm, 
		pte_unmap(pte);

		spin_lock(&mm->page_table_lock);

		BUG_ON(!pmd_none(*pmd));

		set_pmd_at(mm, address, pmd, _pmd);

		/*

		 * We can only use set_pmd_at when establishing

		 * hugepmds and never for establishing regular pmds that

		 * points to regular pagetables. Use pmd_populate for that

		 */

		pmd_populate(mm, pmd, pmd_pgtable(_pmd));

		spin_unlock(&mm->page_table_lock);

		anon_vma_unlock_write(vma->anon_vma);

		goto out;