On Thu, May 23, 2024 at 04:55:44PM +0200, David Hildenbrand wrote: > On 22.05.24 23:03, David Hildenbrand wrote: > > Let's clean it up: use a proper page type and store our data (offset > > into a page) in the lower 16 bit as documented. > > > > We'll have to restrict ourselves to <= 64KB base page size (so the offset > > fits into 16 bit), which sounds reasonable. Unfortunately, we don't have > > any space to store it elsewhere for now. > > > > Based on this, we should do a proper "struct zsdesc" conversion, as > > proposed in [1]. > > > > This removes the last _mapcount/page_type offender. > > > > [1] https://lore.kernel.org/all/20231130101242.2590384-1-42.hyeyoo@xxxxxxxxx/ > > > > Cc: Hyeonggon Yoo <42.hyeyoo@xxxxxxxxx> > > Signed-off-by: David Hildenbrand <david@xxxxxxxxxx> > > --- > > include/linux/page-flags.h | 3 +++ > > mm/Kconfig | 1 + > > mm/zsmalloc.c | 23 +++++++++++++++++++---- > > 3 files changed, 23 insertions(+), 4 deletions(-) > > > > diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h > > index ed9ac4b5233d..ccaf16656de9 100644 > > --- a/include/linux/page-flags.h > > +++ b/include/linux/page-flags.h > > @@ -959,6 +959,7 @@ PAGEFLAG_FALSE(HasHWPoisoned, has_hwpoisoned) > > #define PG_guard 0x00080000 > > #define PG_hugetlb 0x00100800 > > #define PG_slab 0x00200000 > > +#define PG_zsmalloc 0x00400000 > > #define PageType(page, flag) \ > > ((page->page_type & (PAGE_TYPE_BASE | flag)) == PAGE_TYPE_BASE) > > @@ -1073,6 +1074,8 @@ FOLIO_TYPE_OPS(hugetlb, hugetlb) > > FOLIO_TEST_FLAG_FALSE(hugetlb) > > #endif > > +PAGE_TYPE_OPS(Zsmalloc, zsmalloc, zsmalloc) > > + > > /** > > * PageHuge - Determine if the page belongs to hugetlbfs > > * @page: The page to test. > > diff --git a/mm/Kconfig b/mm/Kconfig > > index b4cb45255a54..0371d79b1b75 100644 > > --- a/mm/Kconfig > > +++ b/mm/Kconfig > > @@ -190,6 +190,7 @@ config ZSMALLOC > > tristate > > prompt "N:1 compression allocator (zsmalloc)" if ZSWAP > > depends on MMU > > + depends on PAGE_SIZE_LESS_THAN_256KB # we want <= 64KB > > help > > zsmalloc is a slab-based memory allocator designed to store > > pages of various compression levels efficiently. It achieves > > diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c > > index b42d3545ca85..6f0032e06242 100644 > > --- a/mm/zsmalloc.c > > +++ b/mm/zsmalloc.c > > @@ -20,7 +20,8 @@ > > * page->index: links together all component pages of a zspage > > * For the huge page, this is always 0, so we use this field > > * to store handle. > > - * page->page_type: first object offset in a subpage of zspage > > + * page->page_type: PG_zsmalloc, lower 16 bit locate the first object > > + * offset in a subpage of a zspage > > * > > * Usage of struct page flags: > > * PG_private: identifies the first component page > > @@ -450,14 +451,22 @@ static inline struct page *get_first_page(struct zspage *zspage) > > return first_page; > > } > > +static inline void reset_first_obj_offset(struct page *page) > > +{ > > + page->page_type |= 0xffff; > > +} > > + > > static inline unsigned int get_first_obj_offset(struct page *page) > > { > > - return page->page_type; > > + return page->page_type & 0xffff; > > } > > static inline void set_first_obj_offset(struct page *page, unsigned int offset) > > { > > - page->page_type = offset; > > + BUILD_BUG_ON(PAGE_SIZE & ~0xffff); > > Buildbot is correctly complaining with PAGE_SIZE=64KiB. > > We must check BUILD_BUG_ON((PAGE_SIZE -1) & ~0xffff); Won't BUILD_BUG_ON(PAGE_SIZE > SZ_64K) be clearer? > -- > Cheers, > > David / dhildenb > > -- Sincerely yours, Mike.
