On Mon, Aug 08, 2016 at 10:48:45AM -0700, Linus Torvalds wrote: ... > > [ 43.477693] BUG: Bad page state in process S05containers pfn:1ff02a3 > > [ 43.484417] page:ffffea007fc0a8c0 count:0 mapcount:-511 mapping: (null) index:0x0 > > [ 43.492737] flags: 0x1000000000000000() > > [ 43.496602] page dumped because: nonzero mapcount > > Hmm. The _mapcount field is a union with other fields, but that number > doesn't make sense for any of the other fields. > > So it's almost certainly related to "PAGE_KMEMCG_MAPCOUNT_VALUE". So Yes, it is - my bad. The thing is I set/clear PAGE_KMEMCG_MAPCOUNT_VALUE for pages allocated with __GFP_ACCOUNT iff memcg_kmem_enabled() is true (see __alloc_pages_nodemask and free_pages_prepare), while the latter gets disabled when the last cgroup gets destroyed. So if you do mkdir /sys/fs/cgroup/memory/test # run something in the root cgroup that allocates pages with # __GFP_ACCOUNT, e.g. a program using pipe rmdir /sys/fs/cgroup/memory/test Then, if there are no other memory cgroups, you'll see the bug. Sorry about that :-( Obviously, the PageKmemcg flag should only be set for pages that are actually accounted to a non-root kmemcg and hence pin memcg_kmem_enabled static key. I'll fix that. Thanks, Vladimir -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>