Re: [PATCH] Revert "mm, swap: avoid redundant swap device pinning"

[Kairui Song <ryncsn@gmail.com>]

On Mon, Nov 10, 2025 at 7:37 PM Kairui Song <ryncsn@gmail.com> wrote:
> diff --git a/mm/swap_state.c b/mm/swap_state.c
> index 3f85a1c4cfd9..4cca4865627f 100644
> --- a/mm/swap_state.c
> +++ b/mm/swap_state.c
> @@ -747,6 +747,7 @@ static struct folio
> *swap_vma_readahead(swp_entry_t targ_entry, gfp_t gfp_mask,
>
>         blk_start_plug(&plug);
>         for (addr = start; addr < end; ilx++, addr += PAGE_SIZE) {
> +               struct swap_info_struct *si = NULL;
>                 leaf_entry_t entry;
>
>                 if (!pte++) {
> @@ -761,8 +762,12 @@ static struct folio
> *swap_vma_readahead(swp_entry_t targ_entry, gfp_t gfp_mask,
>                         continue;
>                 pte_unmap(pte);
>                 pte = NULL;
> +               if (swp_type(entry) != swp_type(targ_entry))
> +                       si = get_swap_device(entry);

Oops I missed a NULL check here.


>                 folio = __read_swap_cache_async(entry, gfp_mask, mpol, ilx,
>                                                 &page_allocated, false);
> +               if (si)
> +                       put_swap_device(si);
>                 if (!folio)
>                         continue;
>                 if (page_allocated) {
>
> I'll post a patch if it looks ok.