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 won't be able to support 256 KiB base pages, which is acceptable. Teach Kconfig to handle that cleanly using a new CONFIG_HAVE_ZSMALLOC. 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> --- drivers/block/zram/Kconfig | 1 + include/linux/page-flags.h | 3 +++ mm/Kconfig | 10 ++++++++-- mm/zsmalloc.c | 29 +++++++++++++++++++++++++---- 4 files changed, 37 insertions(+), 6 deletions(-) diff --git a/drivers/block/zram/Kconfig b/drivers/block/zram/Kconfig index 6aea609b795c2..40e035468de22 100644 --- a/drivers/block/zram/Kconfig +++ b/drivers/block/zram/Kconfig @@ -2,6 +2,7 @@ config ZRAM tristate "Compressed RAM block device support" depends on BLOCK && SYSFS && MMU + depends on HAVE_ZSMALLOC select ZSMALLOC help Creates virtual block devices called /dev/zramX (X = 0, 1, ...). diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h index f060db808102c..3afcbfbb379ea 100644 --- a/include/linux/page-flags.h +++ b/include/linux/page-flags.h @@ -957,6 +957,7 @@ PAGEFLAG_FALSE(HasHWPoisoned, has_hwpoisoned) #define PG_guard 0x08000000 #define PG_hugetlb 0x04008000 #define PG_slab 0x02000000 +#define PG_zsmalloc 0x01000000 #define PAGE_MAPCOUNT_RESERVE (~0x0000ffff) #define PageType(page, flag) \ @@ -1072,6 +1073,8 @@ 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 b4cb45255a541..67dc18c94448d 100644 --- a/mm/Kconfig +++ b/mm/Kconfig @@ -128,7 +128,7 @@ config ZSWAP_COMPRESSOR_DEFAULT choice prompt "Default allocator" depends on ZSWAP - default ZSWAP_ZPOOL_DEFAULT_ZSMALLOC if MMU + default ZSWAP_ZPOOL_DEFAULT_ZSMALLOC if HAVE_ZSMALLOC default ZSWAP_ZPOOL_DEFAULT_ZBUD help Selects the default allocator for the compressed cache for @@ -154,6 +154,7 @@ config ZSWAP_ZPOOL_DEFAULT_Z3FOLD config ZSWAP_ZPOOL_DEFAULT_ZSMALLOC bool "zsmalloc" + depends on HAVE_ZSMALLOC select ZSMALLOC help Use the zsmalloc allocator as the default allocator. @@ -186,10 +187,15 @@ config Z3FOLD page. It is a ZBUD derivative so the simplicity and determinism are still there. +config HAVE_ZSMALLOC + def_bool y + depends on MMU + depends on PAGE_SIZE_LESS_THAN_256KB # we want <= 64 KiB + config ZSMALLOC tristate prompt "N:1 compression allocator (zsmalloc)" if ZSWAP - depends on MMU + depends on HAVE_ZSMALLOC 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 a2a5866473bb8..44e0171d60036 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 +451,28 @@ static inline struct page *get_first_page(struct zspage *zspage) return first_page; } +#define FIRST_OBJ_PAGE_TYPE_MASK 0xffff + +static inline void reset_first_obj_offset(struct page *page) +{ + VM_WARN_ON_ONCE(!PageZsmalloc(page)); + page->page_type |= FIRST_OBJ_PAGE_TYPE_MASK; +} + static inline unsigned int get_first_obj_offset(struct page *page) { - return page->page_type; + VM_WARN_ON_ONCE(!PageZsmalloc(page)); + return page->page_type & FIRST_OBJ_PAGE_TYPE_MASK; } static inline void set_first_obj_offset(struct page *page, unsigned int offset) { - page->page_type = offset; + /* With 16 bit available, we can support offsets into 64 KiB pages. */ + BUILD_BUG_ON(PAGE_SIZE > SZ_64K); + VM_WARN_ON_ONCE(!PageZsmalloc(page)); + VM_WARN_ON_ONCE(offset & ~FIRST_OBJ_PAGE_TYPE_MASK); + page->page_type &= ~FIRST_OBJ_PAGE_TYPE_MASK; + page->page_type |= offset & FIRST_OBJ_PAGE_TYPE_MASK; } static inline unsigned int get_freeobj(struct zspage *zspage) @@ -791,8 +806,9 @@ static void reset_page(struct page *page) __ClearPageMovable(page); ClearPagePrivate(page); set_page_private(page, 0); - page_mapcount_reset(page); page->index = 0; + reset_first_obj_offset(page); + __ClearPageZsmalloc(page); } static int trylock_zspage(struct zspage *zspage) @@ -965,11 +981,13 @@ static struct zspage *alloc_zspage(struct zs_pool *pool, if (!page) { while (--i >= 0) { dec_zone_page_state(pages[i], NR_ZSPAGES); + __ClearPageZsmalloc(pages[i]); __free_page(pages[i]); } cache_free_zspage(pool, zspage); return NULL; } + __SetPageZsmalloc(page); inc_zone_page_state(page, NR_ZSPAGES); pages[i] = page; @@ -1754,6 +1772,9 @@ static int zs_page_migrate(struct page *newpage, struct page *page, VM_BUG_ON_PAGE(!PageIsolated(page), page); + /* We're committed, tell the world that this is a Zsmalloc page. */ + __SetPageZsmalloc(newpage); + /* The page is locked, so this pointer must remain valid */ zspage = get_zspage(page); pool = zspage->pool; -- 2.45.1
