On Tue 13-04-21 14:19:03, Mike Kravetz wrote: > On 4/13/21 6:23 AM, Michal Hocko wrote: > > On Tue 13-04-21 12:47:43, Oscar Salvador wrote: [...] > > Or do we need it for giga pages which are not allocated by the page > > allocator? If yes then moving it to prep_compound_gigantic_page would be > > better. > > I am pretty sure dynamically allocated giga pages have page->Private > cleared as well. It is not obvious, but the alloc_contig_range code > used to put together giga pages will end up calling isolate_freepages_range > that will call split_map_pages and then post_alloc_hook for each MAX_ORDER > block. Thanks for saving me from crawling that code. > As mentioned, this is not obvious and I would hate to rely on this > behavior not changing. Thinking about it some more, having some (page granularity) allocator not clearing page private would be a serious problem for anybody relying on its state. So I am not sure this can change. > > So should we just drop it here? > > The only place where page->private may not be initialized is when we do > allocations at boot time from memblock. In this case, we will add the > pages to the free list via put_page/free_huge_page so the appropriate > flags will be cleared before anyone notices. Pages allocated by the bootmem should be pre initialized from the boot, no? > I'm wondering if we should just do a set_page_private(page, 0) here in > prep_new_huge_page since we now use that field for flags. Or, is that > overkill? I would rather not duplicate the work done by underlying allocators. I do not think other users of the allocator want to do the same so why should hugetlb be any different. -- Michal Hocko SUSE Labs
