[PATCH RFC 15/29] mm/migration: remove PageMovable()

[David Hildenbrand]

As __ClearPageMovable() is gone that would have only made
PageMovable()==false but still __PageMovable()==true, now
PageMovable() == __PageMovable().

So we can replace PageMovable() checks by __PageMovable(). In fact,
__PageMovable() cannot change until a page is freed, so we can turn
some PageMovable() into sanity checks for __PageMovable().

Signed-off-by: David Hildenbrand <david at redhat.com>
---
 include/linux/migrate.h |  2 --
 mm/compaction.c         | 15 ---------------
 mm/migrate.c            | 18 ++++++++++--------
 3 files changed, 10 insertions(+), 25 deletions(-)

diff --git a/include/linux/migrate.h b/include/linux/migrate.h
index fb6e9612e9f0b..204e89eac998f 100644
--- a/include/linux/migrate.h
+++ b/include/linux/migrate.h
@@ -104,10 +104,8 @@ static inline int migrate_huge_page_move_mapping(struct address_space *mapping,
 #endif /* CONFIG_MIGRATION */
 
 #ifdef CONFIG_COMPACTION
-bool PageMovable(struct page *page);
 void __SetPageMovable(struct page *page, const struct movable_operations *ops);
 #else
-static inline bool PageMovable(struct page *page) { return false; }
 static inline void __SetPageMovable(struct page *page,
 		const struct movable_operations *ops)
 {
diff --git a/mm/compaction.c b/mm/compaction.c
index 889ec696ba96a..5c37373017014 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -114,21 +114,6 @@ static unsigned long release_free_list(struct list_head *freepages)
 }
 
 #ifdef CONFIG_COMPACTION
-bool PageMovable(struct page *page)
-{
-	const struct movable_operations *mops;
-
-	VM_BUG_ON_PAGE(!PageLocked(page), page);
-	if (!__PageMovable(page))
-		return false;
-
-	mops = page_movable_ops(page);
-	if (mops)
-		return true;
-
-	return false;
-}
-
 void __SetPageMovable(struct page *page, const struct movable_operations *mops)
 {
 	VM_BUG_ON_PAGE(!PageLocked(page), page);
diff --git a/mm/migrate.c b/mm/migrate.c
index db807f9bbf975..cf92075108f0c 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -87,9 +87,12 @@ bool isolate_movable_ops_page(struct page *page, isolate_mode_t mode)
 		goto out;
 
 	/*
-	 * Check movable flag before taking the page lock because
+	 * Check for movable_ops pages before taking the page lock because
 	 * we use non-atomic bitops on newly allocated page flags so
 	 * unconditionally grabbing the lock ruins page's owner side.
+	 *
+	 * Note that once a page has movable_ops, it will stay that way
+	 * until the page was freed.
 	 */
 	if (unlikely(!__PageMovable(page)))
 		goto out_putfolio;
@@ -108,7 +111,8 @@ bool isolate_movable_ops_page(struct page *page, isolate_mode_t mode)
 	if (unlikely(!folio_trylock(folio)))
 		goto out_putfolio;
 
-	if (!PageMovable(page) || PageIsolated(page))
+	VM_WARN_ON_ONCE_PAGE(!__PageMovable(page), page);
+	if (PageIsolated(page))
 		goto out_no_isolated;
 
 	mops = page_movable_ops(page);
@@ -149,11 +153,10 @@ 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(!PageIsolated(page), page);
 	folio_lock(folio);
-	/* If the page was released by it's owner, there is nothing to do. */
-	if (PageMovable(page))
-		page_movable_ops(page)->putback_page(page);
+	page_movable_ops(page)->putback_page(page);
 	ClearPageIsolated(page);
 	folio_unlock(folio);
 	folio_put(folio);
@@ -189,10 +192,9 @@ 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(!PageIsolated(src), src);
-	/* If the page was released by it's owner, there is nothing to do. */
-	if (PageMovable(src))
-		rc = page_movable_ops(src)->migrate_page(dst, src, mode);
+	rc = page_movable_ops(src)->migrate_page(dst, src, mode);
 	if (rc == MIGRATEPAGE_SUCCESS)
 		ClearPageIsolated(src);
 	return rc;
-- 
2.49.0