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SubjectRe: BUG: scheduling while atomic: cron/668/0x10c9a0c0 (was: Re: mm, page_alloc: avoid looking up the first zone in a zonelist twice)
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On 05/30/2016 05:56 PM, Mel Gorman wrote:
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index dba8cfd0b2d6..f2c1e47adc11 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -3232,6 +3232,9 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order,
> * allocations are system rather than user orientated
> */
> ac->zonelist = node_zonelist(numa_node_id(), gfp_mask);
> + ac->preferred_zoneref = first_zones_zonelist(ac->zonelist,
> + ac->high_zoneidx, ac->nodemask);
> + ac->classzone_idx = zonelist_zone_idx(ac->preferred_zoneref);
> page = get_page_from_freelist(gfp_mask, order,
> ALLOC_NO_WATERMARKS, ac);
> if (page)
>

Even if that didn't help for this report, I think it's needed too
(except the classzone_idx which doesn't exist anymore?).

And I think the following as well. (the changed comment could be also
just deleted).


diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index f8f3bfc435ee..0a8d8e2bf331 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3808,7 +3808,7 @@ __alloc_pages_nodemask(gfp_t gfp_mask, unsigned
int order,
/* Dirty zone balancing only done in the fast path */
ac.spread_dirty_pages = (gfp_mask & __GFP_WRITE);

- /* The preferred zone is used for statistics later */
+ /* The preferred zone is crucial for get_page_from_freelist */
ac.preferred_zoneref = first_zones_zonelist(ac.zonelist,
ac.high_zoneidx, ac.nodemask);
if (!ac.preferred_zoneref) {
@@ -3832,8 +3832,11 @@ __alloc_pages_nodemask(gfp_t gfp_mask, unsigned
int order,
* Restore the original nodemask if it was potentially replaced with
* &cpuset_current_mems_allowed to optimize the fast-path attempt.
*/
- if (cpusets_enabled())
+ if (cpusets_enabled()) {
ac.nodemask = nodemask;
+ ac.preferred_zoneref = first_zones_zonelist(ac.zonelist,
+ ac.high_zoneidx, ac.nodemask);
+ }
page = __alloc_pages_slowpath(alloc_mask, order, &ac);

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