On Mon, Jul 1, 2019 at 5:51 PM Henry Burns <henryburns@xxxxxxxxxx> wrote:
>
> __SetPageMovable() expects it's page to be locked, but z3fold.c doesn't
> lock the page. Following zsmalloc.c's example we call trylock_page() and
> unlock_page(). Also makes z3fold_page_migrate() assert that newpage is
> passed in locked, as documentation.
>
> Signed-off-by: Henry Burns <henryburns@xxxxxxxxxx>
> Suggested-by: Vitaly Wool <vitalywool@xxxxxxxxx>
> ---
> Changelog since v1:
> - Added an if statement around WARN_ON(trylock_page(page)) to avoid
> unlocking a page locked by a someone else.
>
> mm/z3fold.c | 6 +++++-
> 1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/mm/z3fold.c b/mm/z3fold.c
> index e174d1549734..6341435b9610 100644
> --- a/mm/z3fold.c
> +++ b/mm/z3fold.c
> @@ -918,7 +918,10 @@ static int z3fold_alloc(struct z3fold_pool *pool, size_t size, gfp_t gfp,
> set_bit(PAGE_HEADLESS, &page->private);
> goto headless;
> }
> - __SetPageMovable(page, pool->inode->i_mapping);
> + if (!WARN_ON(!trylock_page(page))) {
> + __SetPageMovable(page, pool->inode->i_mapping);
> + unlock_page(page);
> + }
Can you please comment why lock_page() is not used here?
> z3fold_page_lock(zhdr);
>
> found:
> @@ -1325,6 +1328,7 @@ static int z3fold_page_migrate(struct address_space *mapping, struct page *newpa
>
> VM_BUG_ON_PAGE(!PageMovable(page), page);
> VM_BUG_ON_PAGE(!PageIsolated(page), page);
> + VM_BUG_ON_PAGE(!PageLocked(newpage), newpage);
>
> zhdr = page_address(page);
> pool = zhdr_to_pool(zhdr);
> --
> 2.22.0.410.gd8fdbe21b5-goog
>
