This is not only about chasing a bug. This also about preventing
memory corruption and information leaking that are caused by ref_count
bugs from happening.
So you mean it like a security hardening feature, not just debugging? To me
it's dubious to put security hardening under CONFIG_DEBUG_VM. I think it's
just Fedora that uses DEBUG_VM in general production kernels?
In our (Google) internal kernel, I added another macro:
PAGE_REF_BUG(cond, page) to replace VM_BUG_ON_PAGE() in page_ref.h.
The new macro keeps the asserts always enabled. I was thinking of
adding something like this to the upstream kernel as well, however, I
am worried about performance implications of having extra conditions
in these routines, so I think we would need yet another config which
decouples DEBUG_VM and some security crucial VM asserts. However, to
reduce controversial discussions, I decided not to do this as part of
this series, and perhaps do it as a follow-up work.
Pasha
