linux-kernel - Re: [PATCH 12/15] mm/swap: fix the obsolete comment for SWP_TYPE

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Date:   Thu, 12 May 2022 15:41:24 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Miaohe Lin <linmiaohe@...wei.com>, akpm@...ux-foundation.org
Cc:     willy@...radead.org, vbabka@...e.cz, dhowells@...hat.com,
        neilb@...e.de, apopple@...dia.com, surenb@...gle.com,
        peterx@...hat.com, naoya.horiguchi@....com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 12/15] mm/swap: fix the obsolete comment for
 SWP_TYPE_SHIFT

On 09.05.22 15:14, Miaohe Lin wrote:
> Since commit 3159f943aafd ("xarray: Replace exceptional entries"), there
> is only one bit of 'type' can be shifted up. Update the corresponding
> comment.
> 
> Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>
> ---
>  include/linux/swapops.h | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/include/linux/swapops.h b/include/linux/swapops.h
> index 7db424e2dcb1..bb7afd03a324 100644
> --- a/include/linux/swapops.h
> +++ b/include/linux/swapops.h
> @@ -13,10 +13,10 @@
>   * get good packing density in that tree, so the index should be dense in
>   * the low-order bits.
>   *
> - * We arrange the `type' and `offset' fields so that `type' is at the seven
> + * We arrange the `type' and `offset' fields so that `type' is at the six
>   * high-order bits of the swp_entry_t and `offset' is right-aligned in the
>   * remaining bits.  Although `type' itself needs only five bits, we allow for
> - * shmem/tmpfs to shift it all up a further two bits: see swp_to_radix_entry().
> + * shmem/tmpfs to shift it all up a further one bit: see swp_to_radix_entry().

Actually, the shift magic is in xa_mk_value() :)

Reviewed-by: David Hildenbrand <david@...hat.com>

-- 
Thanks,

David / dhildenb