Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.35 as permitted sender) client-ip=23.128.96.35;
MIME-Version: 1.0
References: <20231213-zswap-dstmem-v1-0-896763369d04@bytedance.com> <20231213-zswap-dstmem-v1-5-896763369d04@bytedance.com>
In-Reply-To: <20231213-zswap-dstmem-v1-5-896763369d04@bytedance.com>
From:   Yosry Ahmed <yosryahmed@google.com>
Date:   Wed, 13 Dec 2023 17:02:25 -0800
Message-ID: <CAJD7tkb5cKopA-Lfvtsn7sqgqjRf2kyaMwZhhp6SkveNEwArGw@mail.gmail.com>
Subject: Re: [PATCH 5/5] mm/zswap: cleanup zswap_reclaim_entry()
To:     Chengming Zhou <zhouchengming@bytedance.com>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Nhat Pham <nphamcs@gmail.com>, Chris Li <chriscli@google.com>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Seth Jennings <sjenning@redhat.com>,
        Dan Streetman <ddstreet@ieee.org>,
        Vitaly Wool <vitaly.wool@konsulko.com>,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
Precedence: bulk

On Tue, Dec 12, 2023 at 8:18=E2=80=AFPM Chengming Zhou
<zhouchengming@bytedance.com> wrote:
>
> Also after the common decompress part goes to __zswap_load(), we can
> cleanup the zswap_reclaim_entry() a little.

I think you mean zswap_writeback_entry(), same for the commit title.

>
> Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
> ---
>  mm/zswap.c | 23 +++++------------------
>  1 file changed, 5 insertions(+), 18 deletions(-)
>
> diff --git a/mm/zswap.c b/mm/zswap.c
> index 0476e1c553c2..9c709368a0e6 100644
> --- a/mm/zswap.c
> +++ b/mm/zswap.c
> @@ -1449,7 +1449,6 @@ static int zswap_writeback_entry(struct zswap_entry=
 *entry,
>         struct page *page;
>         struct mempolicy *mpol;
>         bool page_was_allocated;
> -       int ret;
>         struct writeback_control wbc =3D {
>                 .sync_mode =3D WB_SYNC_NONE,
>         };
> @@ -1458,16 +1457,13 @@ static int zswap_writeback_entry(struct zswap_ent=
ry *entry,
>         mpol =3D get_task_policy(current);
>         page =3D __read_swap_cache_async(swpentry, GFP_KERNEL, mpol,
>                                 NO_INTERLEAVE_INDEX, &page_was_allocated,=
 true);
> -       if (!page) {
> -               ret =3D -ENOMEM;
> -               goto fail;
> -       }
> +       if (!page)
> +               return -ENOMEM;
>
>         /* Found an existing page, we raced with load/swapin */
>         if (!page_was_allocated) {
>                 put_page(page);
> -               ret =3D -EEXIST;
> -               goto fail;
> +               return -EEXIST;
>         }
>
>         /*
> @@ -1481,8 +1477,7 @@ static int zswap_writeback_entry(struct zswap_entry=
 *entry,
>         if (zswap_rb_search(&tree->rbroot, swp_offset(entry->swpentry)) !=
=3D entry) {
>                 spin_unlock(&tree->lock);
>                 delete_from_swap_cache(page_folio(page));
> -               ret =3D -ENOMEM;
> -               goto fail;
> +               return -ENOMEM;
>         }
>         spin_unlock(&tree->lock);
>
> @@ -1503,15 +1498,7 @@ static int zswap_writeback_entry(struct zswap_entr=
y *entry,
>         __swap_writepage(page, &wbc);
>         put_page(page);
>
> -       return ret;
> -
> -fail:
> -       /*
> -        * If we get here because the page is already in swapcache, a
> -        * load may be happening concurrently. It is safe and okay to
> -        * not free the entry. It is also okay to return !0.
> -        */

This comment should be moved above the failure check of
__read_swap_cache_async() above, not completely removed. With that:

Reviewed-by: Yosry Ahmed <yosryahmed@google.com>

Feel free to squash this patch into the one creating __zswap_load() or
leaving it as-is.