On Tue, May 22, 2018 at 01:48:38PM -0700, Andrew Morton wrote: > -ENOCOMMENT ;) > > --- a/mm/util.c~mm-distinguish-vmalloc-pages-fix-fix > +++ a/mm/util.c > @@ -512,6 +512,8 @@ struct address_space *page_mapping(struc > mapping = page->mapping; > if ((unsigned long)mapping & PAGE_MAPPING_ANON) > return NULL; > + > + /* Don't trip over a vmalloc page's MAPPING_VMalloc cookie */ > if ((unsigned long)mapping < PAGE_SIZE) > return NULL; > > It's a bit sad to put even more stuff into page_mapping() just for > page_types diddling. Is this really justified? How many people will > use it, and get significant benefit from it? We could leave page->mapping NULL for vmalloc pages. We just need to find a spot where we can put a unique identifier. The first word of the union looks like a string candidate; bit 0 is already reserved for PageTail. The other users are list_head.prev, a struct page *, and struct dev_pagemap *, so that should work out OK. If you want to just drop this patch, I'd be OK with that. I can always submit it to you again next merge window.
