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SubjectRe: [PATCH 1/2] mm/vmscan: restore sc->gfp_mask after promoting it to __GFP_HIGHMEM
On 02/12/2014 09:39 PM, Weijie Yang wrote:

> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -2298,14 +2298,17 @@ static bool shrink_zones(struct zonelist *zonelist, struct scan_control *sc)
> unsigned long nr_soft_reclaimed;
> unsigned long nr_soft_scanned;
> bool aborted_reclaim = false;
> + bool promoted_mask = false;
>
> /*
> * If the number of buffer_heads in the machine exceeds the maximum
> * allowed level, force direct reclaim to scan the highmem zone as
> * highmem pages could be pinning lowmem pages storing buffer_heads
> */
> - if (buffer_heads_over_limit)
> + if (buffer_heads_over_limit) {

It took me a minute to figure out why you are doing things this way,
so maybe this could use a comment, or maybe it could be done in a
simpler way, by simply saving and restoring the original mask?

orig_mask = sc->gfp_mask;

> + promoted_mask = !(sc->gfp_mask & __GFP_HIGHMEM);
> sc->gfp_mask |= __GFP_HIGHMEM;
> + }
>
> for_each_zone_zonelist_nodemask(zone, z, zonelist,
> gfp_zone(sc->gfp_mask), sc->nodemask) {
> @@ -2354,6 +2357,9 @@ static bool shrink_zones(struct zonelist *zonelist, struct scan_control *sc)
> shrink_zone(zone, sc);
> }
>
> + if (promoted_mask)
sc->gfp_mask = orig_mask;

> + sc->gfp_mask &= ~__GFP_HIGHMEM;
> +
> return aborted_reclaim;
> }
>
>


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