compaction_suitable() requires a useful cc->alloc_flags, otherwise the results of compact_zone() can be indeterminate. Kcompactd currently checks compaction_suitable() itself with alloc_flags == 0, but passes an uninitialized value from the stack to compact_zone(), which does its own check.
The same is true for compact_node() when explicitly triggering full node compaction. Properly initialize cc.alloc_flags on the stack. Signed-off-by: David Rientjes <[email protected]> --- mm/compaction.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/mm/compaction.c b/mm/compaction.c --- a/mm/compaction.c +++ b/mm/compaction.c @@ -1792,9 +1792,9 @@ static void compact_node(int nid) { pg_data_t *pgdat = NODE_DATA(nid); int zoneid; - struct zone *zone; struct compact_control cc = { .order = -1, + .alloc_flags = 0, .total_migrate_scanned = 0, .total_free_scanned = 0, .mode = MIGRATE_SYNC, @@ -1805,6 +1805,7 @@ static void compact_node(int nid) for (zoneid = 0; zoneid < MAX_NR_ZONES; zoneid++) { + struct zone *zone; zone = &pgdat->node_zones[zoneid]; if (!populated_zone(zone)) @@ -1923,6 +1924,7 @@ static void kcompactd_do_work(pg_data_t *pgdat) struct zone *zone; struct compact_control cc = { .order = pgdat->kcompactd_max_order, + .alloc_flags = 0, .total_migrate_scanned = 0, .total_free_scanned = 0, .classzone_idx = pgdat->kcompactd_classzone_idx, @@ -1945,8 +1947,8 @@ static void kcompactd_do_work(pg_data_t *pgdat) if (compaction_deferred(zone, cc.order)) continue; - if (compaction_suitable(zone, cc.order, 0, zoneid) != - COMPACT_CONTINUE) + if (compaction_suitable(zone, cc.order, cc.alloc_flags, + zoneid) != COMPACT_CONTINUE) continue; cc.nr_freepages = 0;
