From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 5058B411FBE for ; Fri, 9 Oct 2026 05:59:42 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791525584; cv=none; b=f6Ic3bCofGTpONUKP3S+hblnJfsAd7hFa2uck8n16XC9+EfdX76Bg0l7R4EK0ZtgP8dznXNE3XRWloi/QNof73AWIA4PfqTAiwoPqLkbZDyOW22y1QwhwAom2VLjDfdw++LiDCj1K8QyqwrpisgjrxV5jV3y+IrYWZshIjJa9A0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791525584; c=relaxed/simple; bh=cwLDZy1s1Fqks/B891p55J1UPoBpAoySVWjkJNoAR2A=; h=Date:To:From:Subject:Message-Id; b=EtxF/PQcfE1TJn6+UKVQYi0+rnovAplj/IbpQr8YF8PEL5MqqfO7ZB1fMLa+8iXToXykt7KxEqyOWq9L4/GTYhdX0l3qD542QGKzPeXGqgjCX/oRHf0ChUPUNDyUWiUxdubueVsVZiFNZCZxWTwwtxjQ+8lHyAV4/lwLTR8X0Ig= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=EkzqkwZh; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="EkzqkwZh" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2779E1F00898; Fri, 9 Oct 2026 05:59:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=korg; t=1791525582; bh=ESUJPTzhtrqfHU5lFtSLEXEsTG+n6VJl0yUU1vNBnPk=; h=Date:To:From:Subject; b=EkzqkwZh9vo90qKbwPcokrN5uK2/0TrLZdYy7bc+m+e0tb9TBIW2rpqRLkvrrMDTu bNGBZQ2EQUTXMLAFGNNZqBurEDxxE6sEH8jJMKNlLu9uAWyI/BVsI1WCSarqRmcUe7 QAaAsJyKxQ5Ya7MlWw/QPQ9VJCwpy26zRpdt3jkw= Date: Thu, 08 Oct 2026 22:59:41 -0700 To: mm-commits@vger.kernel.org,yuanchu@google.com,ying.huang@linux.alibaba.com,willy@infradead.org,weixugc@google.com,vbabka@kernel.org,usama.arif@linux.dev,surenb@google.com,shakeel.butt@linux.dev,ryan.roberts@arm.com,rppt@kernel.org,rostedt@goodmis.org,rakie.kim@sk.com,qi.zheng@linux.dev,nico.pache@linux.dev,mhocko@suse.com,mhiramat@kernel.org,matthew.brost@intel.com,mathieu.desnoyers@efficios.com,ljs@kernel.org,liam@infradead.org,lance.yang@linux.dev,kasong@tencent.com,joshua.hahnjy@gmail.com,jack@suse.cz,hannes@cmpxchg.org,gourry@gourry.net,dev.jain@arm.com,david@kernel.org,byungchul@sk.com,baolin.wang@linux.alibaba.com,baohua@kernel.org,axelrasmussen@google.com,apopple@nvidia.com,ziy@nvidia.com,akpm@linux-foundation.org From: Andrew Morton Subject: [merged mm-stable] mm-page-flags-check-page-folio-private-instead-of-pg_private.patch removed from -mm tree Message-Id: <20261009055942.2779E1F00898@smtp.kernel.org> Precedence: bulk X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The quilt patch titled Subject: mm/page-flags: check page/folio->private instead of PG_private has been removed from the -mm tree. Its filename was mm-page-flags-check-page-folio-private-instead-of-pg_private.patch This patch was dropped because it was merged into the mm-stable branch of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm ------------------------------------------------------ From: Zi Yan Subject: mm/page-flags: check page/folio->private instead of PG_private Date: Sun, 20 Sep 2026 22:28:06 -0400 After the changes of the prior commits, page/folio->private != NULL is now equivalent to checking PG_private. Stop checking PG_private on pages and folios and use page/folio->private instead, except swapcache and hugetlb folios, because the former uses a field (swp_entry_t swap) overlapping with ->private and the latter sets its flags in ->private. Exclude swapcache and hugetlb when the code is meant to check PG_private only. PG_swapcache and folio->swap.val cannot be set/clear as a whole, so excluding swapcache with folio_test_swapcache() is not reliable. Instead, use folio_test_swapbacked(), since PG_swapbacked is stable when a folio is added to/removed from swapcache. Add a helper, folio_has_attached_private(), for this check. folio_test_private() and PagePrivate() now read folio/page->private plainly instead of an atomic read of PG_private bit, so KCSAN complains about possible data races. Annotate them with data_race(). folio_expected_ref_count() can be called without the folio lock, so annotate folio->mapping with data_race() while at it. folio_set/clear_private() and Set/ClearPagePrivate() become no-ops. PG_private is no longer checked at page free time. They will be removed in an upcoming commit. Remove KPF_PRIVATE since PG_private is no longer used. Link: https://lore.kernel.org/20260920-remove-pg_private-v5-10-bb68b6a21869@nvidia.com Signed-off-by: Zi Yan Signed-off-by: Andrew Morton Acked-by: David Hildenbrand (Arm) Assisted-by: LLM Cc: Steven Rostedt Cc: Masami Hiramatsu Cc: Lorenzo Stoakes Cc: "Matthew Wilcox (Oracle)" Cc: Jan Kara Cc: Johannes Weiner Cc: "Liam R. Howlett" Cc: Vlastimil Babka Cc: Mike Rapoport Cc: Suren Baghdasaryan Cc: Michal Hocko Cc: Mathieu Desnoyers Cc: Baolin Wang Cc: Nico Pache Cc: Ryan Roberts Cc: Dev Jain Cc: Barry Song Cc: Lance Yang Cc: Usama Arif Cc: Matthew Brost Cc: Joshua Hahn Cc: Rakie Kim Cc: Byungchul Park Cc: Gregory Price Cc: Ying Huang Cc: Alistair Popple Cc: Qi Zheng Cc: Shakeel Butt Cc: Kairui Song Cc: Axel Rasmussen Cc: Yuanchu Xie Cc: Wei Xu --- fs/proc/page.c | 1 include/linux/kernel-page-flags.h | 1 include/linux/mm.h | 19 +++++---- include/linux/page-flags.h | 57 +++++++++++++++++++++++++--- include/trace/events/pagemap.h | 2 mm/huge_memory.c | 2 mm/migrate.c | 2 mm/page-writeback.c | 2 mm/vmscan.c | 2 tools/mm/page-types.c | 2 10 files changed, 68 insertions(+), 22 deletions(-) --- a/fs/proc/page.c~mm-page-flags-check-page-folio-private-instead-of-pg_private +++ a/fs/proc/page.c @@ -232,7 +232,6 @@ u64 stable_page_flags(const struct page u |= kpf_copy_bit(k, KPF_RESERVED, PG_reserved); u |= kpf_copy_bit(k, KPF_OWNER_2, PG_owner_2); - u |= kpf_copy_bit(k, KPF_PRIVATE, PG_private); u |= kpf_copy_bit(k, KPF_PRIVATE_2, PG_private_2); u |= kpf_copy_bit(k, KPF_OWNER_PRIVATE, PG_owner_priv_1); u |= kpf_copy_bit(k, KPF_ARCH, PG_arch_1); --- a/include/linux/kernel-page-flags.h~mm-page-flags-check-page-folio-private-instead-of-pg_private +++ a/include/linux/kernel-page-flags.h @@ -11,7 +11,6 @@ #define KPF_RESERVED 32 #define KPF_MLOCKED 33 #define KPF_OWNER_2 34 -#define KPF_PRIVATE 35 #define KPF_PRIVATE_2 36 #define KPF_OWNER_PRIVATE 37 #define KPF_ARCH 38 --- a/include/linux/mm.h~mm-page-flags-check-page-folio-private-instead-of-pg_private +++ a/include/linux/mm.h @@ -3005,9 +3005,9 @@ static inline bool folio_maybe_mapped_sh * @folio: the folio * * Calculate the expected folio refcount, taking references from the pagecache, - * swapcache, PG_private and page table mappings into account. Useful in - * combination with folio_ref_count() to detect unexpected references (e.g., - * GUP or other temporary references). + * swapcache, private data (folio->private != NULL) and page table mappings into + * account. Useful in combination with folio_ref_count() to detect unexpected + * references (e.g., GUP or other temporary references). * * Does currently not consider references from the LRU cache. If the folio * was isolated from the LRU (which is the case during migration or split), @@ -3045,10 +3045,15 @@ static inline int folio_expected_ref_cou ref_count += folio_test_swapcache(folio) << order; if (!folio_test_anon(folio)) { - /* One reference per page from the pagecache. */ - ref_count += !!folio->mapping << order; - /* One reference from PG_private. */ - ref_count += folio_test_private(folio); + /* + * One reference per page from the pagecache. + * Use data_race() since folio might not be locked. + */ + ref_count += !!data_race(folio->mapping) << order; + /* + * One reference from filesystem private data. + */ + ref_count += folio_has_attached_private(folio); } /* One reference per page table mapping. */ --- a/include/linux/page-flags.h~mm-page-flags-check-page-folio-private-instead-of-pg_private +++ a/include/linux/page-flags.h @@ -575,9 +575,31 @@ FOLIO_FLAG(swapbacked, FOLIO_HEAD_PAGE) /* * Private page markings that may be used by the filesystem that owns the page * for its own purposes. - * - PG_private and PG_private_2 cause release_folio() and co to be invoked + * - folio->private and PG_private_2 cause release_folio() and co to be invoked */ -PAGEFLAG(Private, private, PF_ANY) + +static __always_inline bool folio_test_private(const struct folio *folio) +{ + /* + * data_race() is added for readers without holding the folio lock. + * Only the NULL/non-NULL answer is used and both are valid while + * private is being attached or detached, so the race is benign. + */ + return data_race(folio->private); +} + +static __always_inline int PagePrivate(const struct page *page) +{ + /* See folio_test_private() for data_race() use */ + return !!data_race(page->private); +} + +/* no-ops during transition */ +static __always_inline void folio_set_private(struct folio *folio) { } +static __always_inline void folio_clear_private(struct folio *folio) { } +static __always_inline void SetPagePrivate(struct page *page) { } +static __always_inline void ClearPagePrivate(struct page *page) { } + FOLIO_FLAG(private_2, FOLIO_HEAD_PAGE) /* owner_2 can be set on tail pages for anon memory */ @@ -1169,7 +1191,7 @@ static __always_inline void __ClearPageA */ #define PAGE_FLAGS_CHECK_AT_FREE \ (1UL << PG_lru | 1UL << PG_locked | \ - 1UL << PG_private | 1UL << PG_private_2 | \ + 1UL << PG_private_2 | \ 1UL << PG_writeback | 1UL << PG_reserved | \ 1UL << PG_active | \ 1UL << PG_unevictable | __PG_MLOCKED | LRU_GEN_MASK) @@ -1193,8 +1215,31 @@ static __always_inline void __ClearPageA (0xffUL /* order */ | 1UL << PG_has_hwpoisoned | \ 1UL << PG_large_rmappable | 1UL << PG_partially_mapped) -#define PAGE_FLAGS_PRIVATE \ - (1UL << PG_private | 1UL << PG_private_2) +/** + * folio_has_attached_private - check if the folio has private data attached + * @folio: The folio to check. + * + * Use this in code that may encounter swapcache or hugetlb folios but only + * wants to detect attached private data. + * + * Return: true if the folio has private data attached. + */ +static inline bool folio_has_attached_private(const struct folio *folio) +{ + /* + * Swapcache stores swp_entry_t in folio->swap, a union with + * folio->private, and hugetlb stores its own flags in folio->private; + * both are excluded. + * + * NOTE: For swapcache, folio->swap.val PG_swapcache are not set as + * a whole, so folio_test_swapcache() is not reliable to exclude + * swapcache. Use folio_test_swapbacked() instead, since it remains set + * when a folio is added to/removed from swapcache. + */ + + return folio_test_private(folio) && !folio_test_swapbacked(folio) && + !folio_test_hugetlb(folio); +} /** * folio_has_private - Determine if folio has private stuff * @folio: The folio to be checked @@ -1204,7 +1249,7 @@ static __always_inline void __ClearPageA */ static inline int folio_has_private(const struct folio *folio) { - return !!(folio->flags.f & PAGE_FLAGS_PRIVATE); + return folio_has_attached_private(folio) || folio_test_private_2(folio); } #undef PF_ANY --- a/include/trace/events/pagemap.h~mm-page-flags-check-page-folio-private-instead-of-pg_private +++ a/include/trace/events/pagemap.h @@ -22,7 +22,7 @@ (folio_test_swapcache(folio) ? PAGEMAP_SWAPCACHE : 0) | \ (folio_test_swapbacked(folio) ? PAGEMAP_SWAPBACKED : 0) | \ (folio_test_mappedtodisk(folio) ? PAGEMAP_MAPPEDDISK : 0) | \ - (folio_test_private(folio) ? PAGEMAP_BUFFERS : 0) \ + (folio_has_attached_private(folio) ? PAGEMAP_BUFFERS : 0) \ ) TRACE_EVENT(mm_lru_insertion, --- a/mm/huge_memory.c~mm-page-flags-check-page-folio-private-instead-of-pg_private +++ a/mm/huge_memory.c @@ -4845,7 +4845,7 @@ static int split_huge_pages_pid(int pid, * will try to drop it before split and then check if the folio * can be split or not. So skip the check here. */ - if (!folio_test_private(folio) && + if (!folio_has_attached_private(folio) && folio_expected_ref_count(folio) != folio_ref_count(folio)) goto next; --- a/mm/migrate.c~mm-page-flags-check-page-folio-private-instead-of-pg_private +++ a/mm/migrate.c @@ -1327,7 +1327,7 @@ static int migrate_folio_unmap(new_folio * free the metadata, so the page can be freed. */ if (!src->mapping) { - if (folio_test_private(src)) { + if (folio_has_attached_private(src)) { try_to_free_buffers(src); goto out; } --- a/mm/page-writeback.c~mm-page-flags-check-page-folio-private-instead-of-pg_private +++ a/mm/page-writeback.c @@ -2705,7 +2705,7 @@ bool filemap_dirty_folio(struct address_ if (folio_test_set_dirty(folio)) return false; - __folio_mark_dirty(folio, mapping, !folio_test_private(folio)); + __folio_mark_dirty(folio, mapping, !folio_has_attached_private(folio)); if (mapping->host) { /* !PageAnon && !swapper_space */ --- a/mm/vmscan.c~mm-page-flags-check-page-folio-private-instead-of-pg_private +++ a/mm/vmscan.c @@ -1029,7 +1029,7 @@ static void folio_check_dirty_writeback( *writeback = folio_test_writeback(folio); /* Verify dirty/writeback state if the filesystem supports it */ - if (!folio_test_private(folio)) + if (!folio_has_attached_private(folio)) return; mapping = folio_mapping(folio); --- a/tools/mm/page-types.c~mm-page-flags-check-page-folio-private-instead-of-pg_private +++ a/tools/mm/page-types.c @@ -73,7 +73,6 @@ #define KPF_RESERVED 32 #define KPF_MLOCKED 33 #define KPF_OWNER_2 34 -#define KPF_PRIVATE 35 #define KPF_PRIVATE_2 36 #define KPF_OWNER_PRIVATE 37 #define KPF_ARCH 38 @@ -131,7 +130,6 @@ static const char * const page_flag_name [KPF_RESERVED] = "r:reserved", [KPF_MLOCKED] = "m:mlocked", [KPF_OWNER_2] = "d:owner_2", - [KPF_PRIVATE] = "P:private", [KPF_PRIVATE_2] = "p:private_2", [KPF_OWNER_PRIVATE] = "O:owner_private", [KPF_ARCH] = "h:arch", _ Patches currently in -mm which might be from ziy@nvidia.com are