On 07/20/2015 04:21 PM, Kirill A. Shutemov wrote:
> We're going to use migration entries instead of compound_lock() to
> stabilize page refcounts. Setup and remove migration entries require
> page to be locked.
>
> Some of split_huge_page() callers already have the page locked. Let's
> require everybody to lock the page before calling split_huge_page().
>
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
> Tested-by: Sasha Levin <sasha.levin@xxxxxxxxxx>
> Tested-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxxxxxxx>
> Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
Acked-by: Jerome Marchand <jmarchan@xxxxxxxxxx>
> ---
> mm/memory-failure.c | 10 ++++++++--
> mm/migrate.c | 8 ++++++--
> 2 files changed, 14 insertions(+), 4 deletions(-)
>
> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
> index ef33ccf37224..f32a607d1aa3 100644
> --- a/mm/memory-failure.c
> +++ b/mm/memory-failure.c
> @@ -1143,15 +1143,18 @@ int memory_failure(unsigned long pfn, int trapno, int flags)
> put_page(hpage);
> return -EBUSY;
> }
> + lock_page(hpage);
> if (unlikely(split_huge_page(hpage))) {
> pr_err("MCE: %#lx: thp split failed\n", pfn);
> if (TestClearPageHWPoison(p))
> atomic_long_sub(nr_pages, &num_poisoned_pages);
> + unlock_page(hpage);
> put_page(p);
> if (p != hpage)
> put_page(hpage);
> return -EBUSY;
> }
> + unlock_page(hpage);
> VM_BUG_ON_PAGE(!page_count(p), p);
> hpage = compound_head(p);
> }
> @@ -1714,10 +1717,13 @@ int soft_offline_page(struct page *page, int flags)
> return -EBUSY;
> }
> if (!PageHuge(page) && PageTransHuge(hpage)) {
> - if (PageAnon(hpage) && unlikely(split_huge_page(hpage))) {
> + lock_page(page);
> + ret = split_huge_page(hpage);
> + unlock_page(page);
> + if (unlikely(ret)) {
> pr_info("soft offline: %#lx: failed to split THP\n",
> pfn);
> - return -EBUSY;
> + return ret;
> }
> }
>
> diff --git a/mm/migrate.c b/mm/migrate.c
> index 67970faf544d..a9dbfd356e9d 100644
> --- a/mm/migrate.c
> +++ b/mm/migrate.c
> @@ -933,9 +933,13 @@ static ICE_noinline int unmap_and_move(new_page_t get_new_page,
> goto out;
> }
>
> - if (unlikely(PageTransHuge(page)))
> - if (unlikely(split_huge_page(page)))
> + if (unlikely(PageTransHuge(page))) {
> + lock_page(page);
> + rc = split_huge_page(page);
> + unlock_page(page);
> + if (rc)
> goto out;
> + }
>
> rc = __unmap_and_move(page, newpage, force, mode);
>
>
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