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[2003:d8:2f2c:5500:988:23f9:faa0:7232]) by smtp.gmail.com with UTF8SMTPSA id ffacd0b85a97d-3b4708d0aebsm2166371f8f.37.2025.07.04.03.26.23 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 04 Jul 2025 03:26:25 -0700 (PDT) From: David Hildenbrand To: linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org, linux-doc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, virtualization@lists.linux.dev, linux-fsdevel@vger.kernel.org, David Hildenbrand , Andrew Morton , Jonathan Corbet , Madhavan Srinivasan , Michael Ellerman , Nicholas Piggin , Christophe Leroy , Jerrin Shaji George , Arnd Bergmann , Greg Kroah-Hartman , "Michael S. Tsirkin" , Jason Wang , Xuan Zhuo , =?UTF-8?q?Eugenio=20P=C3=A9rez?= , Alexander Viro , Christian Brauner , Jan Kara , Zi Yan , Matthew Brost , Joshua Hahn , Rakie Kim , Byungchul Park , Gregory Price , Ying Huang , Alistair Popple , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , "Matthew Wilcox (Oracle)" , Minchan Kim , Sergey Senozhatsky , Brendan Jackman , Johannes Weiner , Jason Gunthorpe , John Hubbard , Peter Xu , Xu Xin , Chengming Zhou , Miaohe Lin , Naoya Horiguchi , Oscar Salvador , Rik van Riel , Harry Yoo , Qi Zheng , Shakeel Butt Subject: [PATCH v2 20/29] mm: convert "movable" flag in page->mapping to a page flag Date: Fri, 4 Jul 2025 12:25:14 +0200 Message-ID: <20250704102524.326966-21-david@redhat.com> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20250704102524.326966-1-david@redhat.com> References: <20250704102524.326966-1-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: 8bit Instead, let's use a page flag. As the page flag can result in false-positives, glue it to the page types for which we support/implement movable_ops page migration. We are reusing PG_uptodate, that is for example used to track file system state and does not apply to movable_ops pages. So warning in case it is set in page_has_movable_ops() on other page types could result in false-positive warnings. Likely we could set the bit using a non-atomic update: in contrast to page->mapping, we could have others trying to update the flags concurrently when trying to lock the folio. In isolate_movable_ops_page(), we already take care of that by checking if the page has movable_ops before locking it. Let's start with the atomic variant, we could later switch to the non-atomic variant once we are sure other cases are similarly fine. Once we perform the switch, we'll have to introduce __SETPAGEFLAG_NOOP(). Reviewed-by: Zi Yan Reviewed-by: Lorenzo Stoakes Signed-off-by: David Hildenbrand --- include/linux/balloon_compaction.h | 2 +- include/linux/migrate.h | 8 ----- include/linux/page-flags.h | 54 ++++++++++++++++++++++++------ mm/compaction.c | 6 ---- mm/zpdesc.h | 2 +- 5 files changed, 46 insertions(+), 26 deletions(-) diff --git a/include/linux/balloon_compaction.h b/include/linux/balloon_compaction.h index a8a1706cc56f3..b222b0737c466 100644 --- a/include/linux/balloon_compaction.h +++ b/include/linux/balloon_compaction.h @@ -92,7 +92,7 @@ static inline void balloon_page_insert(struct balloon_dev_info *balloon, struct page *page) { __SetPageOffline(page); - __SetPageMovable(page); + SetPageMovableOps(page); set_page_private(page, (unsigned long)balloon); list_add(&page->lru, &balloon->pages); } diff --git a/include/linux/migrate.h b/include/linux/migrate.h index 6aece3f3c8be8..acadd41e0b5cf 100644 --- a/include/linux/migrate.h +++ b/include/linux/migrate.h @@ -103,14 +103,6 @@ static inline int migrate_huge_page_move_mapping(struct address_space *mapping, #endif /* CONFIG_MIGRATION */ -#ifdef CONFIG_COMPACTION -void __SetPageMovable(struct page *page); -#else -static inline void __SetPageMovable(struct page *page) -{ -} -#endif - #ifdef CONFIG_NUMA_BALANCING int migrate_misplaced_folio_prepare(struct folio *folio, struct vm_area_struct *vma, int node); diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h index 4c27ebb689e3c..5f2b570735852 100644 --- a/include/linux/page-flags.h +++ b/include/linux/page-flags.h @@ -170,6 +170,11 @@ enum pageflags { /* non-lru isolated movable page */ PG_isolated = PG_reclaim, +#ifdef CONFIG_MIGRATION + /* this is a movable_ops page (for selected typed pages only) */ + PG_movable_ops = PG_uptodate, +#endif + /* Only valid for buddy pages. Used to track pages that are reported */ PG_reported = PG_uptodate, @@ -698,9 +703,6 @@ PAGEFLAG_FALSE(VmemmapSelfHosted, vmemmap_self_hosted) * bit; and then folio->mapping points, not to an anon_vma, but to a private * structure which KSM associates with that merged page. See ksm.h. * - * PAGE_MAPPING_KSM without PAGE_MAPPING_ANON is used for non-lru movable - * page and then folio->mapping points to a struct movable_operations. - * * Please note that, confusingly, "folio_mapping" refers to the inode * address_space which maps the folio from disk; whereas "folio_mapped" * refers to user virtual address space into which the folio is mapped. @@ -743,13 +745,6 @@ static __always_inline bool PageAnon(const struct page *page) { return folio_test_anon(page_folio(page)); } - -static __always_inline bool page_has_movable_ops(const struct page *page) -{ - return ((unsigned long)page->mapping & PAGE_MAPPING_FLAGS) == - PAGE_MAPPING_MOVABLE; -} - #ifdef CONFIG_KSM /* * A KSM page is one of those write-protected "shared pages" or "merged pages" @@ -1133,6 +1128,45 @@ bool is_free_buddy_page(const struct page *page); PAGEFLAG(Isolated, isolated, PF_ANY); +#ifdef CONFIG_MIGRATION +/* + * This page is migratable through movable_ops (for selected typed pages + * only). + * + * Page migration of such pages might fail, for example, if the page is + * already isolated by somebody else, or if the page is about to get freed. + * + * While a subsystem might set selected typed pages that support page migration + * as being movable through movable_ops, it must never clear this flag. + * + * This flag is only cleared when the page is freed back to the buddy. + * + * Only selected page types support this flag (see page_movable_ops()) and + * the flag might be used in other context for other pages. Always use + * page_has_movable_ops() instead. + */ +TESTPAGEFLAG(MovableOps, movable_ops, PF_NO_TAIL); +SETPAGEFLAG(MovableOps, movable_ops, PF_NO_TAIL); +#else /* !CONFIG_MIGRATION */ +TESTPAGEFLAG_FALSE(MovableOps, movable_ops); +SETPAGEFLAG_NOOP(MovableOps, movable_ops); +#endif /* CONFIG_MIGRATION */ + +/** + * page_has_movable_ops - test for a movable_ops page + * @page The page to test. + * + * Test whether this is a movable_ops page. Such pages will stay that + * way until freed. + * + * Returns true if this is a movable_ops page, otherwise false. + */ +static inline bool page_has_movable_ops(const struct page *page) +{ + return PageMovableOps(page) && + (PageOffline(page) || PageZsmalloc(page)); +} + static __always_inline int PageAnonExclusive(const struct page *page) { VM_BUG_ON_PGFLAGS(!PageAnon(page), page); diff --git a/mm/compaction.c b/mm/compaction.c index 348eb754cb227..349f4ea0ec3e5 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -114,12 +114,6 @@ static unsigned long release_free_list(struct list_head *freepages) } #ifdef CONFIG_COMPACTION -void __SetPageMovable(struct page *page) -{ - VM_BUG_ON_PAGE(!PageLocked(page), page); - page->mapping = (void *)(PAGE_MAPPING_MOVABLE); -} -EXPORT_SYMBOL(__SetPageMovable); /* Do not skip compaction more than 64 times */ #define COMPACT_MAX_DEFER_SHIFT 6 diff --git a/mm/zpdesc.h b/mm/zpdesc.h index 6855d9e2732d8..25bf5ea0beb83 100644 --- a/mm/zpdesc.h +++ b/mm/zpdesc.h @@ -154,7 +154,7 @@ static inline struct zpdesc *pfn_zpdesc(unsigned long pfn) static inline void __zpdesc_set_movable(struct zpdesc *zpdesc) { - __SetPageMovable(zpdesc_page(zpdesc)); + SetPageMovableOps(zpdesc_page(zpdesc)); } static inline void __zpdesc_set_zsmalloc(struct zpdesc *zpdesc) -- 2.49.0