On Sat, Mar 7, 2015 at 10:33 AM, Linus Torvalds
[off-list ref] wrote:

            Completely untested, but that "just
or in the new protection bits" is what pnf_pte() does just a few lines
above this.

Hmm. Looking at this, we do *not* want to set _PAGE_ACCESSED when we
turn a page into PROT_NONE or mark it for numa faulting. Nor do we
want to set it for mprotect for random pages that we haven't actually
accessed, just changed the protections for.

So my patch was obviously wrong, and I should feel bad for suggesting
it. I'm a moron, and my expectations that "pte_modify()" would just
take the accessed bit from the vm_page_prot field was stupid and
wrong.

Mel's patch is the right thing to do.

                                Linus