Re: [PATCH v2] mm: khugepaged: Fix kernel BUG in hpage_collapse_scan_file

[Andrew Morton]

Circling back to this fix...

The BUG() is obviously real.  We're unsure that Ivan's fix is the best
one.  We haven't identified a Fixes:, and as this report is against the 6.2
kernel, a cc:stable will be needed.

According to the sysbot bisection
(https://syzkaller.appspot.com/bug?id=7d6bb3760e026ece7524500fe44fb024a0e959fc),
this is present in linux-5.19, so it might predate Zach's
58ac9a8993a13ebc changes.  But that bisection claim might be
misleading.

And Zach is offline for a few months.  So can people please take a look
and see if we can get this wrapped up?

Matthew, the assertion failure is in the

	VM_BUG_ON(index != xas.xa_index);

which was added in 77da9389b9d5f, so perhaps you could take a look?

Thanks.