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 XD8RDd+U C3Z2bIUJf3YQKhvD9Y1IBm2OBURK4qt5FCaGYMlXDuVn/A2zQK30gQ7k440plTvtmkKlt/s0qC6o3WGs/yj7yhl0fg6Yk9b14+CCP84WyF/1Nygs= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 12/7/22 4:38 PM, John Hubbard wrote: > On 12/7/22 14:37, Sidhartha Kumar wrote: >> Document hugetlb's use of a zero compound order so support for zero >> orders is not removed from folio_set_compound_order(). >> >> Signed-off-by: Sidhartha Kumar >> Suggested-by: Mike Kravetz >> Suggested-by: Muchun Song >> --- >> This can be folded into f2b67a51d0ef6871d4fb0c3e8199f278112bd108 >> mm: add folio dtor and order setter functions >> >>   include/linux/mm.h | 7 +++++++ >>   1 file changed, 7 insertions(+) >> >> diff --git a/include/linux/mm.h b/include/linux/mm.h >> index 443d496949a8..cd8508d728f1 100644 >> --- a/include/linux/mm.h >> +++ b/include/linux/mm.h >> @@ -999,9 +999,16 @@ static inline void set_compound_order(struct page >> *page, unsigned int order) >>   #endif >>   } >> +/* >> + * folio_set_compound_order is generally passed a non-zero order to >> + * initialize a large folio.  However, hugetlb code abuses this by >> + * passing in zero when 'dissolving' a large folio. >> + */ > > Wouldn't it be better to instead just create a new function for that > case, such as: > >     dissolve_large_folio() > Prior to the folio conversion, the helper function __destroy_compound_gigantic_page() did: set_compound_order(page, 0); #ifdef CONFIG_64BIT page[1].compound_nr = 0; #endif as part of dissolving the page. My goal for this patch was to create a function that would encapsulate that segment of code with a single call of folio_set_compound_order(folio, 0). set_compound_order() does not set compound_nr to 0 when 0 is passed in to the order argument so explicitly setting it is required. I don't think a separate dissolve_large_folio() function for the hugetlb case is needed as __destroy_compound_gigantic_folio() is pretty concise as it is. > ? > >>   static inline void folio_set_compound_order(struct folio *folio, >>           unsigned int order) >>   { >> +    VM_BUG_ON_FOLIO(!folio_test_large(folio), folio); >> + >>       folio->_folio_order = order; >>   #ifdef CONFIG_64BIT >>       folio->_folio_nr_pages = order ? 1U << order : 0; > > thanks,