Messages in this thread | | | Date | Fri, 16 Dec 2022 15:10:41 -0800 | Subject | Re: [PATCH mm-unstable] mm: move folio_set_compound_order() to mm/internal.h | From | Sidhartha Kumar <> |
| |
On 12/16/22 2:56 PM, John Hubbard wrote: > On 12/16/22 14:27, Andrew Morton wrote: >> On Tue, 13 Dec 2022 13:20:53 -0800 Sidhartha Kumar >> <sidhartha.kumar@oracle.com> wrote: >> >>> folio_set_compound_order() is moved to an mm-internal location so >>> external >>> folio users cannot misuse this function. Change the name of the function >>> to folio_set_order() and use WARN_ON_ONCE() rather than BUG_ON. Also, >>> handle the case if a non-large folio is passed and add clarifying >>> comments >>> to the function. >>> >> >> This differs from the version I previously merged: >> >> --- >> a/mm/internal.h~mm-move-folio_set_compound_order-to-mm-internalh-update >> +++ a/mm/internal.h >> @@ -384,8 +384,10 @@ int split_free_page(struct page *free_pa >> */ >> static inline void folio_set_order(struct folio *folio, unsigned int >> order) >> { >> - if (WARN_ON_ONCE(!folio_test_large(folio))) >> + if (!folio_test_large(folio)) { >> + WARN_ON_ONCE(order); >> return; >> + } > > I think that's out of date? > > We eventually settled on the version that is (as of this a few minutes > ago) already in mm-unstable (commit fdea060a130d: "mm: move > folio_set_compound_order() to mm/internal.h"), which has it like this: > Hi Andrew, yes this version that is already in mm-unstable represents the v2 of this patch which is what we agreed on. I think the patch mm-move-folio_set_compound_order-to-mm-internalh-update with description "alter the folio_set_order() warning" which was just added to mm-unstable should be removed as our discussion lead us away from that version.
> if (WARN_ON_ONCE(!folio_test_large(folio))) > return; > >> folio->_folio_order = order; >> #ifdef CONFIG_64BIT >> >> Makes sense. But wouldn't >> >> if (WARN_ON_ONCE(order && !folio_test_large(folio))) >> >> be clearer? > That's a little narrower of a check. But maybe that's desirable. Could
Ya I think it would helpful to have a wider catch for the warn as any user calling folio_set_order() with a non-large folio should be aware as they could misuse the folio later on even if they passed in a 0 order because order itself would be an OOB access.
Thanks, Sidhartha Kumar > someone (Mike, Muchun, Sidhartha) comment on which behavior is > preferable, please? I think I'm a little dizzy at this point. :) > > > thanks,
| |