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-rw-r--r--mm/compaction.c12
1 files changed, 10 insertions, 2 deletions
diff --git a/mm/compaction.c b/mm/compaction.c
index bbf41ee99142..658c009d60cc 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -1392,11 +1392,19 @@ static enum compact_result __compaction_suitable(struct zone *zone, int order,
/*
* Watermarks for order-0 must be met for compaction to be able to
- * isolate free pages for migration targets.
+ * isolate free pages for migration targets. This means that the
+ * watermark and alloc_flags have to match, or be more pessimistic than
+ * the check in __isolate_free_page(). We don't use the direct
+ * compactor's alloc_flags, as they are not relevant for freepage
+ * isolation. We however do use the direct compactor's classzone_idx to
+ * skip over zones where lowmem reserves would prevent allocation even
+ * if compaction succeeds.
+ * ALLOC_CMA is used, as pages in CMA pageblocks are considered
+ * suitable migration targets
*/
watermark = low_wmark_pages(zone) + compact_gap(order);
if (!__zone_watermark_ok(zone, 0, watermark, classzone_idx,
- alloc_flags, wmark_target))
+ ALLOC_CMA, wmark_target))
return COMPACT_SKIPPED;
/*