linux-kernel - Re: [PATCH] z3fold: avoid modifying HEADLESS page and minor cleanup

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Date:	Fri, 27 May 2016 14:37:21 -0400
From:	Dan Streetman <ddstreet@...e.org>
To:	Vitaly Wool <vitalywool@...il.com>
Cc:	Linux-MM <linux-mm@...ck.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Seth Jennings <sjenning@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] z3fold: avoid modifying HEADLESS page and minor cleanup

On Fri, May 27, 2016 at 12:06 PM, Vitaly Wool <vitalywool@...il.com> wrote:
> This patch fixes erroneous z3fold header access in a HEADLESS page
> in reclaim function, and changes one remaining direct
> handle-to-buddy conversion to use the appropriate helper.
>
> Signed-off-by: Vitaly Wool <vitalywool@...il.com>

Reviewed-by: Dan Streetman <ddstreet@...e.org>

> ---
>  mm/z3fold.c | 24 ++++++++++++++----------
>  1 file changed, 14 insertions(+), 10 deletions(-)
>
> diff --git a/mm/z3fold.c b/mm/z3fold.c
> index 34917d5..8f9e89c 100644
> --- a/mm/z3fold.c
> +++ b/mm/z3fold.c
> @@ -412,7 +412,7 @@ static void z3fold_free(struct z3fold_pool *pool,
> unsigned long handle)
>                 /* HEADLESS page stored */
>                 bud = HEADLESS;
>         } else {
> -               bud = (handle - zhdr->first_num) & BUDDY_MASK;
> +               bud = handle_to_buddy(handle);
>                 switch (bud) {
>                 case FIRST:
> @@ -572,15 +572,19 @@ next:
>                         pool->pages_nr--;
>                         spin_unlock(&pool->lock);
>                         return 0;
> -               } else if (zhdr->first_chunks != 0 &&
> -                          zhdr->last_chunks != 0 && zhdr->middle_chunks !=
> 0) {
> -                       /* Full, add to buddied list */
> -                       list_add(&zhdr->buddy, &pool->buddied);
> -               } else if (!test_bit(PAGE_HEADLESS, &page->private)) {
> -                       z3fold_compact_page(zhdr);
> -                       /* add to unbuddied list */
> -                       freechunks = num_free_chunks(zhdr);
> -                       list_add(&zhdr->buddy,
> &pool->unbuddied[freechunks]);
> +               }  else if (!test_bit(PAGE_HEADLESS, &page->private)) {
> +                       if (zhdr->first_chunks != 0 &&
> +                           zhdr->last_chunks != 0 &&
> +                           zhdr->middle_chunks != 0) {
> +                               /* Full, add to buddied list */
> +                               list_add(&zhdr->buddy, &pool->buddied);
> +                       } else {
> +                               z3fold_compact_page(zhdr);
> +                               /* add to unbuddied list */
> +                               freechunks = num_free_chunks(zhdr);
> +                               list_add(&zhdr->buddy,
> +                                        &pool->unbuddied[freechunks]);
> +                       }
>                 }
>                 /* add to beginning of LRU */
> --
> 2.5.0
>