mm: rename __PageMovable() to page_has_movable_ops()

Let's make it clearer that we are talking about movable_ops pages.

While at it, convert a VM_BUG_ON to a VM_WARN_ON_ONCE_PAGE.

Link: https://lkml.kernel.org/r/20250704102524.326966-17-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Reviewed-by: Harry Yoo <harry.yoo@oracle.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Brendan Jackman <jackmanb@google.com>
Cc: Byungchul Park <byungchul@sk.com>
Cc: Chengming Zhou <chengming.zhou@linux.dev>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Eugenio Pé rez <eperezma@redhat.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Gregory Price <gourry@gourry.net>
Cc: "Huang, Ying" <ying.huang@linux.alibaba.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Jason Wang <jasowang@redhat.com>
Cc: Jerrin Shaji George <jerrin.shaji-george@broadcom.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Joshua Hahn <joshua.hahnjy@gmail.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Madhavan Srinivasan <maddy@linux.ibm.com>
Cc: Mathew Brost <matthew.brost@intel.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Naoya Horiguchi <nao.horiguchi@gmail.com>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Peter Xu <peterx@redhat.com>
Cc: Qi Zheng <zhengqi.arch@bytedance.com>
Cc: Rakie Kim <rakie.kim@sk.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Cc: xu xin <xu.xin16@zte.com.cn>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Author: davidhildenbrand

include/linux/migrate.h

@@ -115,7 +115,7 @@ static inline void __SetPageMovable(struct page *page,
 static inline
 const struct movable_operations *page_movable_ops(struct page *page)
 {
-	VM_BUG_ON(!__PageMovable(page));
+	VM_WARN_ON_ONCE_PAGE(!page_has_movable_ops(page), page);
 
 	return (const struct movable_operations *)
 		((unsigned long)page->mapping - PAGE_MAPPING_MOVABLE);

include/linux/page-flags.h

@@ -750,7 +750,7 @@ static __always_inline bool __folio_test_movable(const struct folio *folio)
 			PAGE_MAPPING_MOVABLE;
 }
 
-static __always_inline bool __PageMovable(const struct page *page)
+static __always_inline bool page_has_movable_ops(const struct page *page)
 {
 	return ((unsigned long)page->mapping & PAGE_MAPPING_FLAGS) ==
 				PAGE_MAPPING_MOVABLE;

mm/compaction.c

@@ -1056,11 +1056,8 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
 		 * Skip any other type of page
 		 */
 		if (!PageLRU(page)) {
-			/*
-			 * __PageMovable can return false positive so we need
-			 * to verify it under page_lock.
-			 */
-			if (unlikely(__PageMovable(page)) &&
+			/* Isolation code will deal with any races. */
+			if (unlikely(page_has_movable_ops(page)) &&
 					!PageIsolated(page)) {
 				if (locked) {
 					unlock_page_lruvec_irqrestore(locked, flags);

mm/memory-failure.c

@@ -1388,8 +1388,8 @@ static inline bool HWPoisonHandlable(struct page *page, unsigned long flags)
 	if (PageSlab(page))
 		return false;
 
-	/* Soft offline could migrate non-LRU movable pages */
-	if ((flags & MF_SOFT_OFFLINE) && __PageMovable(page))
+	/* Soft offline could migrate movable_ops pages */
+	if ((flags & MF_SOFT_OFFLINE) && page_has_movable_ops(page))
 		return true;
 
 	return PageLRU(page) || is_free_buddy_page(page);

mm/memory_hotplug.c

@@ -1739,8 +1739,8 @@ bool mhp_range_allowed(u64 start, u64 size, bool need_mapping)
 
 #ifdef CONFIG_MEMORY_HOTREMOVE
 /*
- * Scan pfn range [start,end) to find movable/migratable pages (LRU pages,
- * non-lru movable pages and hugepages). Will skip over most unmovable
+ * Scan pfn range [start,end) to find movable/migratable pages (LRU and
+ * hugetlb folio, movable_ops pages). Will skip over most unmovable
  * pages (esp., pages that can be skipped when offlining), but bail out on
  * definitely unmovable pages.
  *
@@ -1759,13 +1759,11 @@ static int scan_movable_pages(unsigned long start, unsigned long end,
 		struct folio *folio;
 
 		page = pfn_to_page(pfn);
-		if (PageLRU(page))
-			goto found;
-		if (__PageMovable(page))
+		if (PageLRU(page) || page_has_movable_ops(page))
 			goto found;
 
 		/*
-		 * PageOffline() pages that are not marked __PageMovable() and
+		 * PageOffline() pages that do not have movable_ops and
 		 * have a reference count > 0 (after MEM_GOING_OFFLINE) are
 		 * definitely unmovable. If their reference count would be 0,
 		 * they could at least be skipped when offlining memory.

mm/migrate.c

@@ -94,7 +94,7 @@ bool isolate_movable_ops_page(struct page *page, isolate_mode_t mode)
 	 * Note that once a page has movable_ops, it will stay that way
 	 * until the page was freed.
 	 */
-	if (unlikely(!__PageMovable(page)))
+	if (unlikely(!page_has_movable_ops(page)))
 		goto out_putfolio;
 
 	/*
@@ -111,7 +111,7 @@ bool isolate_movable_ops_page(struct page *page, isolate_mode_t mode)
 	if (unlikely(!folio_trylock(folio)))
 		goto out_putfolio;
 
-	VM_WARN_ON_ONCE_PAGE(!__PageMovable(page), page);
+	VM_WARN_ON_ONCE_PAGE(!page_has_movable_ops(page), page);
 	if (PageIsolated(page))
 		goto out_no_isolated;
 
@@ -153,7 +153,7 @@ static void putback_movable_ops_page(struct page *page)
 	 */
 	struct folio *folio = page_folio(page);
 
-	VM_WARN_ON_ONCE_PAGE(!__PageMovable(page), page);
+	VM_WARN_ON_ONCE_PAGE(!page_has_movable_ops(page), page);
 	VM_WARN_ON_ONCE_PAGE(!PageIsolated(page), page);
 	folio_lock(folio);
 	page_movable_ops(page)->putback_page(page);
@@ -194,7 +194,7 @@ static int migrate_movable_ops_page(struct page *dst, struct page *src,
 {
 	int rc = MIGRATEPAGE_SUCCESS;
 
-	VM_WARN_ON_ONCE_PAGE(!__PageMovable(src), src);
+	VM_WARN_ON_ONCE_PAGE(!page_has_movable_ops(src), src);
 	VM_WARN_ON_ONCE_PAGE(!PageIsolated(src), src);
 	rc = page_movable_ops(src)->migrate_page(dst, src, mode);
 	if (rc == MIGRATEPAGE_SUCCESS)

mm/page_alloc.c

@@ -2006,7 +2006,7 @@ static bool prep_move_freepages_block(struct zone *zone, struct page *page,
 			 * migration are movable. But we don't actually try
 			 * isolating, as that would be expensive.
 			 */
-			if (PageLRU(page) || __PageMovable(page))
+			if (PageLRU(page) || page_has_movable_ops(page))
 				(*num_movable)++;
 			pfn++;
 		}

mm/page_isolation.c

@@ -21,9 +21,9 @@
  * consequently belong to a single zone.
  *
  * PageLRU check without isolation or lru_lock could race so that
- * MIGRATE_MOVABLE block might include unmovable pages. And __PageMovable
- * check without lock_page also may miss some movable non-lru pages at
- * race condition. So you can't expect this function should be exact.
+ * MIGRATE_MOVABLE block might include unmovable pages. Similarly, pages
+ * with movable_ops can only be identified some time after they were
+ * allocated. So you can't expect this function should be exact.
  *
  * Returns a page without holding a reference. If the caller wants to
  * dereference that page (e.g., dumping), it has to make sure that it
@@ -133,7 +133,7 @@ static struct page *has_unmovable_pages(unsigned long start_pfn, unsigned long e
 		if ((mode == PB_ISOLATE_MODE_MEM_OFFLINE) && PageOffline(page))
 			continue;
 
-		if (__PageMovable(page) || PageLRU(page))
+		if (PageLRU(page) || page_has_movable_ops(page))
 			continue;
 
 		/*
@@ -421,7 +421,7 @@ static int isolate_single_pageblock(unsigned long boundary_pfn,
 			 * proper free and split handling for them.
 			 */
 			VM_WARN_ON_ONCE_PAGE(PageLRU(page), page);
-			VM_WARN_ON_ONCE_PAGE(__PageMovable(page), page);
+			VM_WARN_ON_ONCE_PAGE(page_has_movable_ops(page), page);
 
 			goto failed;
 		}