On 10/6/21 16:58, Matthew Wilcox wrote: > David expressed some unease about the lack of typesafety in patches > 1 & 2 of the page->slab conversion [1], and I'll admit to not being > particularly a fan of passing around an unsigned long. That crystallised > in a discussion with Kent [2] about how to lock a page when you don't know > its type (solution: every memory descriptor type starts with a > pgflags_t) > > So this patch is a step towards typesafety for pgflags_lock() by > changing the type of page->flags from a bare unsigned long to a > struct encapsulating an unsigned long. A few users can already benefit > from passing around a pgflags_t, but most just append '.f' to get at > the unsigned long. Also, most of them only do it for logging/tracing. > > [1] https://lore.kernel.org/linux-mm/02a055cd-19d6-6e1d-59bb-e9e5f9f1da5b@xxxxxxxxxx/ > [2] https://lore.kernel.org/linux-mm/YVyQpPuwIGFSSEQ8@xxxxxxxxxxxxxxxxxxxx/ > ... > diff --git a/mm/debug.c b/mm/debug.c > index fae0f81ad831..48af9829aee9 100644 > --- a/mm/debug.c > +++ b/mm/debug.c > @@ -162,7 +162,7 @@ static void __dump_page(struct page *page) > out_mapping: > BUILD_BUG_ON(ARRAY_SIZE(pageflag_names) != __NR_PAGEFLAGS + 1); > > - pr_warn("%sflags: %#lx(%pGp)%s\n", type, head->flags, &head->flags, > + pr_warn("%sflags: %#lx(%pGp)%s\n", type, head->flags.f, &head->flags.f, The %pGp case (here and elsewhere) could perhaps take the new type, no? Would need to change format_page_flags() and flags_string() in lib/vsprintf.c
