On Tue, Feb 16, 2016 at 05:24:44PM +0100, Gerald Schaefer wrote:

On Mon, 15 Feb 2016 23:35:26 +0200
"Kirill A. Shutemov" [off-list ref] wrote:

quoted

Is there any chance that I'll be able to trigger the bug using QEMU?
Does anybody have an QEMU image I can use?

I have no image, but trying to reproduce this under virtualization may
help to trigger this also on other architectures. After ruling out IPI
vs. fast_gup I do not really see why this should be arch-specific, and
it wouldn't be the first time that we hit subtle races first on s390, due
to our virtualized environment (my test case is make -j20 with 10 CPUs and
4GB of memory, no swap).

Could you post your kernel config?

It would be nice also to check if disabling split_huge_page() would make
any difference:

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index a75081ca31cf..26d2b7b21021 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c

@@ -3364,6 +3364,8 @@ int split_huge_page_to_list(struct page *page, struct list_head *list)
 	bool mlocked;
 	unsigned long flags;
 
+	return -EBUSY;
+
 	VM_BUG_ON_PAGE(is_huge_zero_page(page), page);
 	VM_BUG_ON_PAGE(!PageAnon(page), page);
 	VM_BUG_ON_PAGE(!PageLocked(page), page);

-- 
 Kirill A. Shutemov