On Sun, Jan 31, 2016 at 11:22:09PM +1100, Matthew Wilcox wrote:
> We allocate a pgtable but do not attach it to anything if the PMD is in
> a DAX VMA, causing it to leak.
>
> We certainly try to not free pgtables associated with the huge zero page
> if the zero page is in a DAX VMA, so I think this is the right solution.
> This needs to be properly audited.
>
> Signed-off-by: Matthew Wilcox <matthew.r.wilcox@xxxxxxxxx>
> ---
> mm/huge_memory.c | 17 ++++++++++-------
> 1 file changed, 10 insertions(+), 7 deletions(-)
>
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index 4b9f2cb..1632e02 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -889,7 +889,8 @@ static bool set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm,
> return false;
> entry = mk_pmd(zero_page, vma->vm_page_prot);
> entry = pmd_mkhuge(entry);
> - pgtable_trans_huge_deposit(mm, pmd, pgtable);
> + if (pgtable)
> + pgtable_trans_huge_deposit(mm, pmd, pgtable);
> set_pmd_at(mm, haddr, pmd, entry);
> atomic_long_inc(&mm->nr_ptes);
> return true;
> @@ -1176,13 +1177,15 @@ int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
> spinlock_t *dst_ptl, *src_ptl;
> struct page *src_page;
> pmd_t pmd;
> - pgtable_t pgtable;
> + pgtable_t pgtable = NULL;
> int ret;
>
> - ret = -ENOMEM;
> - pgtable = pte_alloc_one(dst_mm, addr);
> - if (unlikely(!pgtable))
> - goto out;
> + if (!vma_is_dax(vma)) {
> + ret = -ENOMEM;
> + pgtable = pte_alloc_one(dst_mm, addr);
> + if (unlikely(!pgtable))
> + goto out;
> + }
>
> dst_ptl = pmd_lock(dst_mm, dst_pmd);
> src_ptl = pmd_lockptr(src_mm, src_pmd);
> @@ -1213,7 +1216,7 @@ int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
> goto out_unlock;
> }
>
> - if (pmd_trans_huge(pmd)) {
> + if (!vma_is_dax(vma)) {
Why? It looks equivalent in this situation, no?
Otherwise:
Acked-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
> /* thp accounting separate from pmd_devmap accounting */
> src_page = pmd_page(pmd);
> VM_BUG_ON_PAGE(!PageHead(src_page), src_page);
> --
> 2.7.0.rc3
>
> --
> To unsubscribe, send a message with 'unsubscribe linux-mm' in
> the body to majordomo@xxxxxxxxx. For more info on Linux MM,
> see: http://www.linux-mm.org/ .
> Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
--
Kirill A. Shutemov
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@xxxxxxxxx. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>