Re: [PATCH 20/27] mm, vmscan: Update classzone_idx if buffer_heads_over_limit

[Vlastimil Babka]

On 06/09/2016 08:04 PM, Mel Gorman wrote:
> If buffer heads are over the limit then the direct reclaim gfp_mask
> is promoted to __GFP_HIGHMEM so that lowmem is indirectly freed. With
> node-based reclaim, it is also required that the classzone_idx be updated
> or the pages will be skipped.
>
> Signed-off-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>

Acked-by: Vlastimil Babka <vbabka@xxxxxxx>

> ---
>  mm/vmscan.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 3edf941e9965..7a2d69612231 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -2547,8 +2547,10 @@ static void shrink_zones(struct zonelist *zonelist, struct scan_control *sc,
>  	 * highmem pages could be pinning lowmem pages storing buffer_heads
>  	 */
>  	orig_mask = sc->gfp_mask;
> -	if (buffer_heads_over_limit)
> +	if (buffer_heads_over_limit) {
>  		sc->gfp_mask |= __GFP_HIGHMEM;
> +		classzone_idx = gfp_zone(sc->gfp_mask);
> +	}
>
>  	for_each_zone_zonelist_nodemask(zone, z, zonelist,
>  					gfp_zone(sc->gfp_mask), sc->nodemask) {