On 6/7/24 10:29 PM, Stephen Brennan wrote: > Changing PG_slab from a page flag to a page type in commit 46df8e73a4a3 > ("mm: free up PG_slab") in has the unintended consequence of removing > the PG_slab constant from kernel debuginfo. The commit does add the > value to the vmcoreinfo note, which allows debuggers to find the value > without hardcoding it. However it's most flexible to continue > representing the constant with an enum. To that end, convert the page > type fields into an enum. Debuggers will now be able to detect that > PG_slab's type has changed from enum pageflags to enum pagetype. > > Fixes: 46df8e73a4a3 ("mm: free up PG_slab") > > Signed-off-by: Stephen Brennan <stephen.s.brennan@xxxxxxxxxx> Acked-by: Vlastimil Babka <vbabka@xxxxxxx> > --- > v3 -> v4: rename to enum pagetype, avoiding conflict in f2fs.h and matching > the name of enum pageflags > v2 -> v3: rebase on mm-unstable > v1 -> v2: include PAGE_TYPE_BASE and PAGE_MAPCOUNT_RESERVE > > include/linux/page-flags.h | 31 +++++++++++++++++-------------- > 1 file changed, 17 insertions(+), 14 deletions(-) > > diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h > index f04fea86324d9..32722c6e8397b 100644 > --- a/include/linux/page-flags.h > +++ b/include/linux/page-flags.h > @@ -945,20 +945,23 @@ PAGEFLAG_FALSE(HasHWPoisoned, has_hwpoisoned) > * mistaken for a page type value. > */ > > -#define PAGE_TYPE_BASE 0x80000000 > -/* > - * Reserve 0xffff0000 - 0xfffffffe to catch _mapcount underflows and > - * allow owners that set a type to reuse the lower 16 bit for their own > - * purposes. > - */ > -#define PG_buddy 0x40000000 > -#define PG_offline 0x20000000 > -#define PG_table 0x10000000 > -#define PG_guard 0x08000000 > -#define PG_hugetlb 0x04000000 > -#define PG_slab 0x02000000 > -#define PG_zsmalloc 0x01000000 > -#define PAGE_MAPCOUNT_RESERVE (~0x0000ffff) > +enum pagetype { > + /* > + * Reserve 0xffff0000 - 0xfffffffe to catch _mapcount underflows and > + * allow owners that set a type to reuse the lower 16 bit for their own > + * purposes. > + */ > + PG_buddy = 0x40000000, > + PG_offline = 0x20000000, > + PG_table = 0x10000000, > + PG_guard = 0x08000000, > + PG_hugetlb = 0x04000000, > + PG_slab = 0x02000000, > + PG_zsmalloc = 0x01000000, > + > + PAGE_TYPE_BASE = 0x80000000, > + PAGE_MAPCOUNT_RESERVE = ~0x0000ffff, > +}; > > #define PageType(page, flag) \ > ((page->page_type & (PAGE_TYPE_BASE | flag)) == PAGE_TYPE_BASE)