On Tue, Feb 23, 2016 at 06:45:05PM +0530, Anshuman Khandual wrote: > Not able to understand the first code block of follow_page_mask > function. follow_huge_addr function is expected to find the page > struct for the given address if it turns out to be a HugeTLB page > but then when it finds the page we bug on if it had been called > with FOLL_GET flag. > > page = follow_huge_addr(mm, address, flags & FOLL_WRITE); > if (!IS_ERR(page)) { > BUG_ON(flags & FOLL_GET); > return page; > } > > do_move_page_to_node_array calls follow_page with FOLL_GET which > in turn calls follow_page_mask with FOLL_GET. On POWER, the > function follow_huge_addr is defined and does not return -EINVAL > like the generic one. It returns the page struct if its a HugeTLB > page. Just curious to know what is the purpose behind the BUG_ON.
I would guess requesting pin on non-reclaimable page is considered useless, meaning suspicius behavior. BUG_ON() is overkill, I think. WARN_ON_ONCE() would make it. Not that this follow_huge_addr() on Power is not reachable via do_move_page_to_node_array(), because the vma is !vma_is_migratable(). -- Kirill A. Shutemov _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev