mm, thp: Do not make page table dirty unconditionally in touch_p[mu]d() Currently, we unconditionally make page table dirty in touch_pmd(). It may result in false-positive can_follow_write_pmd(). We may avoid the situation, if we would only make the page table entry dirty if caller asks for write access -- FOLL_WRITE. Upstream commit a8f97366452ed491d13cf1e44241bc0b5740b1f0 fixed this issue.
