Re: [PATCH v5 14/19] mm, swap: cleanup swap entry management workflow

[Chris Mason <clm@meta.com>]

On Sat, 20 Dec 2025 03:43:43 +0800 Kairui Song <ryncsn@gmail.com> wrote:

Hi everyone,

I ran mm-new through the AI review prompts, and this one was flagged:

> diff --git a/kernel/power/swap.c b/kernel/power/swap.c
> index 8050e51828351..036489d3b01a9 100644
> --- a/kernel/power/swap.c
> +++ b/kernel/power/swap.c

[ ... ]

> @@ -186,6 +186,7 @@ sector_t alloc_swapdev_block(int swap)
>
>  void free_all_swap_pages(int swap)
>  {
> +	unsigned long offset;
>  	struct rb_node *node;
>
>  	/*
> @@ -197,8 +198,9 @@ void free_all_swap_pages(int swap)
>
>  		ext = rb_entry(node, struct swsusp_extent, node);
>  		rb_erase(node, &swsusp_extents);
> -		swap_free_nr(swp_entry(swap, ext->start),
> -			     ext->end - ext->start + 1);
> +
> +		for (offset = ext->start; offset < ext->end; offset++)
> +			swap_free_hibernation_slot(swp_entry(swap, offset));
                                           ^^^^^^^^^^^

Is this loop missing the final slot at ext->end?

The old code freed (ext->end - ext->start + 1) entries, which is the
inclusive range [ext->start, ext->end]. Looking at swsusp_extents_insert(),
when a single slot is inserted it sets ext->start = ext->end = offset, and
merging extends the range by incrementing ext->end or decrementing
ext->start. This means ext->end is inclusive.

The new loop uses "offset < ext->end" which iterates [ext->start, ext->end),
missing the slot at ext->end. Should this be "offset <= ext->end" instead?