On Wed 28-11-18 16:55:25, Yu Zhao wrote:
> Pagetable page doesn't touch page->mapping or have any used field
> that overlaps with it. No need to clear mapping in dtor. In fact,
> doing so might mask problems that otherwise would be detected by
> bad_page().
yes the layour of the structure has changed since Hugh introduced the
pte lock split
> Signed-off-by: Yu Zhao <yuzhao@xxxxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
> ---
> include/linux/mm.h | 11 ++---------
> 1 file changed, 2 insertions(+), 9 deletions(-)
>
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 5411de93a363..7c8f4fc9244e 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -1900,13 +1900,6 @@ static inline bool ptlock_init(struct page *page)
> return true;
> }
>
> -/* Reset page->mapping so free_pages_check won't complain. */
> -static inline void pte_lock_deinit(struct page *page)
> -{
> - page->mapping = NULL;
> - ptlock_free(page);
> -}
> -
> #else /* !USE_SPLIT_PTE_PTLOCKS */
> /*
> * We use mm->page_table_lock to guard all pagetable pages of the mm.
> @@ -1917,7 +1910,7 @@ static inline spinlock_t *pte_lockptr(struct mm_struct *mm, pmd_t *pmd)
> }
> static inline void ptlock_cache_init(void) {}
> static inline bool ptlock_init(struct page *page) { return true; }
> -static inline void pte_lock_deinit(struct page *page) {}
> +static inline void ptlock_free(struct page *page) {}
> #endif /* USE_SPLIT_PTE_PTLOCKS */
>
> static inline void pgtable_init(void)
> @@ -1937,7 +1930,7 @@ static inline bool pgtable_page_ctor(struct page *page)
>
> static inline void pgtable_page_dtor(struct page *page)
> {
> - pte_lock_deinit(page);
> + ptlock_free(page);
> __ClearPageTable(page);
> dec_zone_page_state(page, NR_PAGETABLE);
> }
> --
> 2.20.0.rc1.387.gf8505762e3-goog
>
--
Michal Hocko
SUSE Labs
