From nobody Wed Dec 17 09:13:14 2025 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 63D0A17F386 for ; Mon, 27 May 2024 14:15:12 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1716819314; cv=none; b=G5Se/ZGjxZtN8X95tz3EcWFkZHt7h9qfEBjmtayBCAh3v8/B+sNTWfQn3vrBDjh4eIzs8JAqMwmvv8Bp1G+tuNGzWcSrYPHpxj6e8cLKObp0DivcL/u9632rAtVCSkbINVrUj0eKogW1XwSVZQzSKsuELS1C3Ok5leBMMnmLyOU= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1716819314; c=relaxed/simple; bh=LQnr2dWxWaO0mTPKpQ9V8ob7MlbBRQUqTcfaSvQlt5c=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=lzn11UL7PZRUXVCwmJ7iG0pcHsj2ijItu2nLrgVNMZlto5Tyc7BL6G3suGCPTYXHuN1K6YKKwdKFbg2vL4g/HrXS7GYVqjeKGRS8dYLSIqDST/JHRQ3TswoxOtWIu9WGdFiW9dbk+0YgCxDwXXYCsFl04wdm653lvmSXG7KZVWg= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=PyEpytCb; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="PyEpytCb" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1716819311; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=NhkUSgtSn3vBcIMl6XAMgZKK8WplKXeQveOWeM1SVs0=; b=PyEpytCbg9WhvrbOU2KxODy5+KGJkJgp6u7Ve1ExskwccC97ZBMbPC1XcZqyqLnWTt0nqQ dXJtmQwF+KJAmmsE/3OdtKI+cYiPOBiKX5bRS9QwwPoKTdl3Yt/MMva1kT6pi2VO4nhcZE p6UWwZab4V5H6Ucm35QnMoQYyJlgDFU= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-215-HIw6c0EOM4SYxgQQgxJgVA-1; Mon, 27 May 2024 10:15:07 -0400 X-MC-Unique: HIw6c0EOM4SYxgQQgxJgVA-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.rdu2.redhat.com [10.11.54.7]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 52CBA185A780; Mon, 27 May 2024 14:15:07 +0000 (UTC) Received: from t490s.redhat.com (unknown [10.39.192.209]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 58D411C00A8E; Mon, 27 May 2024 14:15:04 +0000 (UTC) From: David Hildenbrand To: linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org, David Hildenbrand , Andrew Morton , "Matthew Wilcox (Oracle)" , Mike Rapoport , Minchan Kim , Sergey Senozhatsky , Hyeonggon Yoo <42.hyeyoo@gmail.com> Subject: [PATCH v1 3/6] mm/zsmalloc: use a proper page type Date: Mon, 27 May 2024 16:14:51 +0200 Message-ID: <20240527141454.113132-4-david@redhat.com> In-Reply-To: <20240527141454.113132-1-david@redhat.com> References: <20240527141454.113132-1-david@redhat.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.7 Content-Type: text/plain; charset="utf-8" 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@gmail.co= m/ Cc: Hyeonggon Yoo <42.hyeyoo@gmail.com> Signed-off-by: David Hildenbrand --- 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 7b29cce60ab2..39c04419bf87 100644 --- a/drivers/block/zram/Kconfig +++ b/drivers/block/zram/Kconfig @@ -3,6 +3,7 @@ config ZRAM tristate "Compressed RAM block device support" depends on BLOCK && SYSFS && MMU depends on CRYPTO_LZO || CRYPTO_ZSTD || CRYPTO_LZ4 || CRYPTO_LZ4HC || CRY= PTO_842 + depends on HAVE_ZSMALLOC select ZSMALLOC help Creates virtual block devices called /dev/zramX (X =3D 0, 1, ...). diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h index b43e380ffa0b..36d9ded4462d 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 0x00080000 #define PG_hugetlb 0x00100800 #define PG_slab 0x00200000 +#define PG_zsmalloc 0x00400000 =20 #define PageType(page, flag) \ ((page->page_type & (PAGE_TYPE_BASE | flag)) =3D=3D PAGE_TYPE_BASE) @@ -1071,6 +1072,8 @@ FOLIO_TYPE_OPS(hugetlb, hugetlb) FOLIO_TEST_FLAG_FALSE(hugetlb) #endif =20 +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..67dc18c94448 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 =20 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. =20 +config HAVE_ZSMALLOC + def_bool y + depends on MMU + depends on PAGE_SIZE_LESS_THAN_256KB # we want <=3D 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 b42d3545ca85..1a6af454520e 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 zspa= ge *zspage) return first_page; } =20 +#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 |=3D 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; } =20 static inline void set_first_obj_offset(struct page *page, unsigned int of= fset) { - page->page_type =3D 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 &=3D ~FIRST_OBJ_PAGE_TYPE_MASK; + page->page_type |=3D offset & FIRST_OBJ_PAGE_TYPE_MASK; } =20 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 =3D 0; + reset_first_obj_offset(page); + __ClearPageZsmalloc(page); } =20 static int trylock_zspage(struct zspage *zspage) @@ -965,11 +981,13 @@ static struct zspage *alloc_zspage(struct zs_pool *po= ol, if (!page) { while (--i >=3D 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); =20 inc_zone_page_state(page, NR_ZSPAGES); pages[i] =3D page; @@ -1762,6 +1780,9 @@ static int zs_page_migrate(struct page *newpage, stru= ct page *page, =20 VM_BUG_ON_PAGE(!PageIsolated(page), page); =20 + /* 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 =3D get_zspage(page); pool =3D zspage->pool; --=20 2.45.1