Re: [PATCH 1/3] mm: pgtable: correct the wrong comment about ptdesc->__page_flags

From: Vishal Moola <vishal.moola@gmail.com>
To: Qi Zheng <zhengqi.arch@bytedance.com>
Cc: akpm@linux-foundation.org, hughd@google.com, david@redhat.com,
	rppt@kernel.org, willy@infradead.org, muchun.song@linux.dev,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/3] mm: pgtable: correct the wrong comment about ptdesc->__page_flags
Date: Tue, 26 Mar 2024 12:12:41 -0700	[thread overview]
Message-ID: <ZgMeKa3ee7oHrkq5@fedora> (raw)
In-Reply-To: <cc42d5915fd98fd802f920de243f535efcfe01db.1709541697.git.zhengqi.arch@bytedance.com>

On Mon, Mar 04, 2024 at 07:07:18PM +0800, Qi Zheng wrote:
> The commit 32cc0b7c9d50 ("powerpc: add pte_free_defer() for pgtables
> sharing page") introduced the use of PageActive flag to page table
> fragments tracking, so the ptdesc->__page_flags is not unused, so
> correct the wrong comment.

Thanks for catching this!

In regards to naming, we're trying to prefix unused variables with
__underscores so I'd prefer to see the __ eliminated from the
ptdesc->page_flags field here as well. This doesn't warrant a fix
as it is already in 6.9-rc1, but is something to keep in
mind for the future. Aside from that, LGTM.

Reviewed-by: Vishal Moola (Oracle) <vishal.moola@gmail.com>
> Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com>
> ---
>  include/linux/mm_types.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
> index a7223ba3ea1e..5ea77969daae 100644
> --- a/include/linux/mm_types.h
> +++ b/include/linux/mm_types.h
> @@ -419,7 +419,7 @@ FOLIO_MATCH(compound_head, _head_2a);
>  
>  /**
>   * struct ptdesc -    Memory descriptor for page tables.
> - * @__page_flags:     Same as page flags. Unused for page tables.
> + * @__page_flags:     Same as page flags. Powerpc only.
>   * @pt_rcu_head:      For freeing page table pages.
>   * @pt_list:          List of used page tables. Used for s390 and x86.
>   * @_pt_pad_1:        Padding that aliases with page's compound head.
> -- 
> 2.30.2
> 