Re: cgroup and FALLOC_FL_PUNCH_HOLE: WARNING: CPU: 13 PID: 2438 at mm/page_counter.c:57 page_counter_uncharge+0x4b/0x5

[Mike Kravetz]

On 10/20/20 6:38 AM, David Hildenbrand wrote:
> 
> I'm bisecting the warning right now. Looks like it was introduced in v5.7.

I found the following bugs in the cgroup reservation accounting.  The ones
in region_del are pretty obvious as the number of pages to uncharge would
always be zero.  The one on alloc_huge_page needs racing code to expose.

With these fixes, my testing is showing consistent/correct results for
hugetlb reservation cgroup accounting.

It would be good if Mina (at least) would look these over.  Would also
be interesting to know if these fixes address the bug seen with the qemu
use case.

I'm still doing more testing and code inspection to look for other issues.