linux-kernel - Re: [PATCH v3 5/6] mm/zswap: cleanup zswap_writeback

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Date: Tue, 19 Dec 2023 04:50:23 -0800
From: Chris Li <chrisl@...nel.org>
To: Chengming Zhou <zhouchengming@...edance.com>
Cc: Seth Jennings <sjenning@...hat.com>, Yosry Ahmed <yosryahmed@...gle.com>, 
	Vitaly Wool <vitaly.wool@...sulko.com>, Dan Streetman <ddstreet@...e.org>, 
	Johannes Weiner <hannes@...xchg.org>, Andrew Morton <akpm@...ux-foundation.org>, 
	Nhat Pham <nphamcs@...il.com>, linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH v3 5/6] mm/zswap: cleanup zswap_writeback_entry()

Acked-by: Chris Li <chrisl@...nel.org> (Google)

I also thing this one can fold into patch 3. Too trivial to be a separate patch.
Your call.

Chris

On Mon, Dec 18, 2023 at 3:50 AM Chengming Zhou
<zhouchengming@...edance.com> wrote:
>
> Also after the common decompress part goes to __zswap_load(), we can
> cleanup the zswap_writeback_entry() a little.
>
> Reviewed-by: Yosry Ahmed <yosryahmed@...gle.com>
> Reviewed-by: Nhat Pham <nphamcs@...il.com>
> Signed-off-by: Chengming Zhou <zhouchengming@...edance.com>
> ---
>  mm/zswap.c | 25 +++++++++----------------
>  1 file changed, 9 insertions(+), 16 deletions(-)
>
> diff --git a/mm/zswap.c b/mm/zswap.c
> index 86886276cb81..2c349fd88904 100644
> --- a/mm/zswap.c
> +++ b/mm/zswap.c
> @@ -1443,7 +1443,6 @@ 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 = {
>                 .sync_mode = WB_SYNC_NONE,
>         };
> @@ -1453,15 +1452,18 @@ static int zswap_writeback_entry(struct zswap_entry *entry,
>         page = __read_swap_cache_async(swpentry, GFP_KERNEL, mpol,
>                                 NO_INTERLEAVE_INDEX, &page_was_allocated, true);
>         if (!page) {
> -               ret = -ENOMEM;
> -               goto 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.
> +                */
> +               return -ENOMEM;
>         }
>
>         /* Found an existing page, we raced with load/swapin */
>         if (!page_was_allocated) {
>                 put_page(page);
> -               ret = -EEXIST;
> -               goto fail;
> +               return -EEXIST;
>         }
>
>         /*
> @@ -1475,8 +1477,7 @@ static int zswap_writeback_entry(struct zswap_entry *entry,
>         if (zswap_rb_search(&tree->rbroot, swp_offset(entry->swpentry)) != entry) {
>                 spin_unlock(&tree->lock);
>                 delete_from_swap_cache(page_folio(page));
> -               ret = -ENOMEM;
> -               goto fail;
> +               return -ENOMEM;
>         }
>         spin_unlock(&tree->lock);
>
> @@ -1497,15 +1498,7 @@ static int zswap_writeback_entry(struct zswap_entry *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.
> -        */
> -       return ret;
> +       return 0;
>  }
>
>  static int zswap_is_page_same_filled(void *ptr, unsigned long *value)
>
> --
> b4 0.10.1