[PATCH 5/8] mm/vmscan: Use PG_dropbehind instead of PG_reclaim

[David Hildenbrand]

On 13.01.25 10:34, Kirill A. Shutemov wrote:
> The recently introduced PG_dropbehind allows for freeing folios
> immediately after writeback. Unlike PG_reclaim, it does not need vmscan
> to be involved to get the folio freed.
> 
> Instead of using folio_set_reclaim(), use folio_set_dropbehind() in
> pageout().
> 
> It is safe to leave PG_dropbehind on the folio if, for some reason
> (bug?), the folio is not in a writeback state after ->writepage().
> In these cases, the kernel had to clear PG_reclaim as it shared a page
> flag bit with PG_readahead.
> 
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov at linux.intel.com>
> ---
>   mm/vmscan.c | 9 +++------
>   1 file changed, 3 insertions(+), 6 deletions(-)
> 
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index a099876fa029..d15f80333d6b 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -692,19 +692,16 @@ static pageout_t pageout(struct folio *folio, struct address_space *mapping,
>   		if (shmem_mapping(mapping) && folio_test_large(folio))
>   			wbc.list = folio_list;
>   
> -		folio_set_reclaim(folio);
> +		folio_set_dropbehind(folio);
> +
>   		res = mapping->a_ops->writepage(&folio->page, &wbc);
>   		if (res < 0)
>   			handle_write_error(mapping, folio, res);
>   		if (res == AOP_WRITEPAGE_ACTIVATE) {
> -			folio_clear_reclaim(folio);
> +			folio_clear_dropbehind(folio);
>   			return PAGE_ACTIVATE;
>   		}
>   
> -		if (!folio_test_writeback(folio)) {
> -			/* synchronous write or broken a_ops? */
> -			folio_clear_reclaim(folio);
> -		}
>   		trace_mm_vmscan_write_folio(folio);
>   		node_stat_add_folio(folio, NR_VMSCAN_WRITE);
>   		return PAGE_SUCCESS;

Acked-by: David Hildenbrand <david at redhat.com>

-- 
Cheers,

David / dhildenb