Below kernel vm bug can be triggered by tcpdump which mmaped a lot of pages with GFP_COMP flag.
[Mon May 25 05:29:33 2015] page:ffffea0015414000 count:66 mapcount:1 mapping: (null) index:0x0
[Mon May 25 05:29:33 2015] flags: 0x20047580004000(head)
[Mon May 25 05:29:33 2015] page dumped because: VM_BUG_ON_PAGE(compound_order(page) && !PageTransHuge(page))
[Mon May 25 05:29:33 2015] ------------[ cut here ]------------
[Mon May 25 05:29:33 2015] kernel BUG at mm/migrate.c:1661!
[Mon May 25 05:29:33 2015] invalid opcode: 0000 [#1] SMP
The fix is simply disallow migrate mmaped compound pages, return 0 instead of
report vm bug.
---
mm/migrate.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/mm/migrate.c b/mm/migrate.c
index f53838f..839adef 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -1606,7 +1606,8 @@ static int numamigrate_isolate_page(pg_data_t *pgdat, struct page *page)
{
int page_lru;
- VM_BUG_ON_PAGE(compound_order(page) && !PageTransHuge(page), page);
+ if (compound_order(page) && !PageTransHuge(page))
+ return 0;
/* Avoid migrating to a node that is nearly full */
if (!migrate_balanced_pgdat(pgdat, 1UL << compound_order(page)))
--
1.9.1