linux-kernel - Re: [PATCH] mm/swapfile.c: introduce function alloc_swap_scan

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Message-Id: <20250806153146.ee1ee22dc8f6381ff5a6d882@linux-foundation.org>
Date: Wed, 6 Aug 2025 15:31:46 -0700
From: Andrew Morton <akpm@...ux-foundation.org>
To: Chris Li <chrisl@...nel.org>
Cc: Kemeng Shi <shikemeng@...weicloud.com>, Kairui Song
 <kasong@...cent.com>, Nhat Pham <nphamcs@...il.com>, Baoquan He
 <bhe@...hat.com>, Barry Song <baohua@...nel.org>, "Huang, Ying"
 <ying.huang@...ux.alibaba.com>, linux-mm@...ck.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm/swapfile.c: introduce function
 alloc_swap_scan_list()

On Wed, 06 Aug 2025 10:34:45 -0700 Chris Li <chrisl@...nel.org> wrote:

> This the alloc_swap_scan_list() will scan the whole list or the first
> cluster.
> 
> This reduces the repeat patterns of isolating a cluster then scanning
> that cluster. As a result, cluster_alloc_swap_entry() is shorter and shallower.
> 
> No functional change.
> ...
>
> ---
>  mm/swapfile.c | 86 ++++++++++++++++++++++++++++++++---------------------------
>  1 file changed, 47 insertions(+), 39 deletions(-)

A nice little patch.

> diff --git a/mm/swapfile.c b/mm/swapfile.c
> index 4a0cf4fb348d..fcb1e57d8108 100644
> --- a/mm/swapfile.c
> +++ b/mm/swapfile.c
> @@ -820,6 +820,29 @@ static unsigned int alloc_swap_scan_cluster(struct swap_info_struct *si,
>  	return found;
>  }
>  
> +static unsigned int alloc_swap_scan_list(struct swap_info_struct *si,
> +					 struct list_head *list,
> +					 unsigned int order,
> +					 unsigned char usage,
> +					 bool scan_all)
> +{
> +	int found = SWAP_ENTRY_INVALID;

but this function returns an unsigned int

> +
> +	do {
> +		struct swap_cluster_info *ci = isolate_lock_cluster(si, list);
> +		unsigned long offset;
> +
> +		if (!ci)
> +			break;
> +		offset = cluster_offset(si, ci);
> +		found = alloc_swap_scan_cluster(si, ci, offset, order, usage);

so does that one

> +		if (found)
> +			return found;

`break' here.  To avoid multiple return points and for consistency.

> +	} while (scan_all);
> +
> +	return found;
> +}
> +
>  static void swap_reclaim_full_clusters(struct swap_info_struct *si, bool force)
>  {
>  	long to_scan = 1;