From: Zi Yan <ziy@xxxxxxxxxx> Subject: mm/compaction: stop isolation if too many pages are isolated and we have pages to migrate In isolate_migratepages_block, if we have too many isolated pages and nr_migratepages is not zero, we should try to migrate what we have without wasting time on isolating. In theory it's possible that multiple parallel compactions will cause too_many_isolated() to become true even if each has isolated less than COMPACT_CLUSTER_MAX, and loop forever in the while loop. Bailing immediately prevents that. [vbabka@xxxxxxx: changelog addition] Link: https://lkml.kernel.org/r/20201030183809.3616803-2-zi.yan@xxxxxxxx Fixes: 1da2f328fa64 (“mm,thp,compaction,cma: allow THP migration for CMA allocations”) Signed-off-by: Zi Yan <ziy@xxxxxxxxxx> Suggested-by: Vlastimil Babka <vbabka@xxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx> Cc: Michal Hocko <mhocko@xxxxxxxxxx> Cc: Rik van Riel <riel@xxxxxxxxxxx> Cc: Yang Shi <shy828301@xxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/compaction.c | 4 ++++ 1 file changed, 4 insertions(+) --- a/mm/compaction.c~mm-compaction-stop-isolation-if-too-many-pages-are-isolated-and-we-have-pages-to-migrate +++ a/mm/compaction.c @@ -817,6 +817,10 @@ isolate_migratepages_block(struct compac * delay for some time until fewer pages are isolated */ while (unlikely(too_many_isolated(pgdat))) { + /* stop isolation if there are still pages not migrated */ + if (cc->nr_migratepages) + return 0; + /* async migration should just abort */ if (cc->mode == MIGRATE_ASYNC) return 0; _
