Hello Mel Gorman,
This is a semi-automatic email about new static checker warnings.
The patch 5e1f0f098b46: "mm, compaction: capture a page under direct
compaction" from Mar 5, 2019, leads to the following Smatch complaint:
mm/compaction.c:2321 compact_zone_order()
error: we previously assumed 'capture' could be null (see line 2313)
mm/compaction.c
2288 static enum compact_result compact_zone_order(struct zone *zone, int order,
2289 gfp_t gfp_mask, enum compact_priority prio,
2290 unsigned int alloc_flags, int classzone_idx,
2291 struct page **capture)
^^^^^^^
2292 {
2293 enum compact_result ret;
2294 struct compact_control cc = {
2295 .order = order,
2296 .search_order = order,
2297 .gfp_mask = gfp_mask,
2298 .zone = zone,
2299 .mode = (prio == COMPACT_PRIO_ASYNC) ?
2300 MIGRATE_ASYNC : MIGRATE_SYNC_LIGHT,
2301 .alloc_flags = alloc_flags,
2302 .classzone_idx = classzone_idx,
2303 .direct_compaction = true,
2304 .whole_zone = (prio == MIN_COMPACT_PRIORITY),
2305 .ignore_skip_hint = (prio == MIN_COMPACT_PRIORITY),
2306 .ignore_block_suitable = (prio == MIN_COMPACT_PRIORITY)
2307 };
2308 struct capture_control capc = {
2309 .cc = &cc,
2310 .page = NULL,
2311 };
2312
2313 if (capture)
^^^^^^^
Check for NULL
2314 current->capture_control = &capc;
2315
2316 ret = compact_zone(&cc, &capc);
2317
2318 VM_BUG_ON(!list_empty(&cc.freepages));
2319 VM_BUG_ON(!list_empty(&cc.migratepages));
2320
2321 *capture = capc.page;
^^^^^^^^
Unchecked dereference.
2322 current->capture_control = NULL;
2323
regards,
dan carpenter
