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 <rientjes@xxxxxxxxxx>
---
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;
--
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