<minc...@kernel.org> writes:
[snip]

> diff --git a/mm/swap_state.c b/mm/swap_state.c
> index 39ae7cfad90f..c56cce64b2c3 100644
> --- a/mm/swap_state.c
> +++ b/mm/swap_state.c
> @@ -332,32 +332,38 @@ struct page *lookup_swap_cache(swp_entry_t entry, 
> struct vm_area_struct *vma,
>                              unsigned long addr)
>  {
>       struct page *page;
> -     unsigned long ra_info;
> -     int win, hits, readahead;
>  
>       page = find_get_page(swap_address_space(entry), swp_offset(entry));
>  
>       INC_CACHE_INFO(find_total);
>       if (page) {
> +             bool vma_ra = swap_use_vma_readahead();
> +             bool readahead = TestClearPageReadahead(page);
> +

TestClearPageReadahead() cannot be called for compound page.  As in

PAGEFLAG(Readahead, reclaim, PF_NO_COMPOUND)
        TESTCLEARFLAG(Readahead, reclaim, PF_NO_COMPOUND)

>               INC_CACHE_INFO(find_success);
>               if (unlikely(PageTransCompound(page)))
>                       return page;
> -             readahead = TestClearPageReadahead(page);

So we can only call it here after checking whether page is compound.

Best Regards,
Huang, Ying

> -             if (vma) {
> -                     ra_info = GET_SWAP_RA_VAL(vma);
> -                     win = SWAP_RA_WIN(ra_info);
> -                     hits = SWAP_RA_HITS(ra_info);
> +
> +             if (vma && vma_ra) {
> +                     unsigned long ra_val;
> +                     int win, hits;
> +
> +                     ra_val = GET_SWAP_RA_VAL(vma);
> +                     win = SWAP_RA_WIN(ra_val);
> +                     hits = SWAP_RA_HITS(ra_val);
>                       if (readahead)
>                               hits = min_t(int, hits + 1, SWAP_RA_HITS_MAX);
>                       atomic_long_set(&vma->swap_readahead_info,
>                                       SWAP_RA_VAL(addr, win, hits));
>               }
> +
>               if (readahead) {
>                       count_vm_event(SWAP_RA_HIT);
> -                     if (!vma)
> +                     if (!vma || !vma_ra)
>                               atomic_inc(&swapin_readahead_hits);
>               }
>       }
> +
>       return page;
>  }
>

[snip]

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