[PATCH 1/6] mm: migrate: add isolate_movable_folio()

[Kefeng Wang <wangkefeng.wang@huawei.com>]

Like isolate_lru_page(), make isolate_movable_page() as a wrapper
around isolate_lru_folio(), since isolate_movable_page() always
fails on a tail page, add a warn for tail page and return immediately.

Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
---
 include/linux/migrate.h |  3 +++
 mm/migrate.c            | 41 +++++++++++++++++++++++------------------
 2 files changed, 26 insertions(+), 18 deletions(-)

diff --git a/include/linux/migrate.h b/include/linux/migrate.h
index f9d92482d117..a6c38ee7246a 100644
--- a/include/linux/migrate.h
+++ b/include/linux/migrate.h
@@ -70,6 +70,7 @@ int migrate_pages(struct list_head *l, new_folio_t new, free_folio_t free,
 		  unsigned int *ret_succeeded);
 struct folio *alloc_migration_target(struct folio *src, unsigned long private);
 bool isolate_movable_page(struct page *page, isolate_mode_t mode);
+bool isolate_movable_folio(struct folio *folio, isolate_mode_t mode);
 
 int migrate_huge_page_move_mapping(struct address_space *mapping,
 		struct folio *dst, struct folio *src);
@@ -91,6 +92,8 @@ static inline struct folio *alloc_migration_target(struct folio *src,
 	{ return NULL; }
 static inline bool isolate_movable_page(struct page *page, isolate_mode_t mode)
 	{ return false; }
+static inline bool isolate_movable_folio(struct page *page, isolate_mode_t mode)
+	{ return false; }
 
 static inline int migrate_huge_page_move_mapping(struct address_space *mapping,
 				  struct folio *dst, struct folio *src)
diff --git a/mm/migrate.c b/mm/migrate.c
index 2228ca681afb..b2195b6ff32c 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -57,31 +57,29 @@
 
 #include "internal.h"
 
-bool isolate_movable_page(struct page *page, isolate_mode_t mode)
+bool isolate_movable_folio(struct folio *folio, isolate_mode_t mode)
 {
-	struct folio *folio = folio_get_nontail_page(page);
 	const struct movable_operations *mops;
 
 	/*
-	 * Avoid burning cycles with pages that are yet under __free_pages(),
+	 * Avoid burning cycles with folios that are yet under __free_pages(),
 	 * or just got freed under us.
 	 *
-	 * In case we 'win' a race for a movable page being freed under us and
+	 * In case we 'win' a race for a movable folio being freed under us and
 	 * raise its refcount preventing __free_pages() from doing its job
-	 * the put_page() at the end of this block will take care of
-	 * release this page, thus avoiding a nasty leakage.
+	 * the folio_put() at the end of this block will take care of
+	 * release this folio, thus avoiding a nasty leakage.
 	 */
-	if (!folio)
-		goto out;
+	folio_get(folio);
 
 	if (unlikely(folio_test_slab(folio)))
 		goto out_putfolio;
 	/* Pairs with smp_wmb() in slab freeing, e.g. SLUB's __free_slab() */
 	smp_rmb();
 	/*
-	 * Check movable flag 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.
+	 * Check movable flag before taking the folio lock because
+	 * we use non-atomic bitops on newly allocated folio flags so
+	 * unconditionally grabbing the lock ruins folio's owner side.
 	 */
 	if (unlikely(!__folio_test_movable(folio)))
 		goto out_putfolio;
@@ -91,13 +89,13 @@ bool isolate_movable_page(struct page *page, isolate_mode_t mode)
 		goto out_putfolio;
 
 	/*
-	 * As movable pages are not isolated from LRU lists, concurrent
-	 * compaction threads can race against page migration functions
-	 * as well as race against the releasing a page.
+	 * As movable folios are not isolated from LRU lists, concurrent
+	 * compaction threads can race against folio migration functions
+	 * as well as race against the releasing a folio.
 	 *
-	 * In order to avoid having an already isolated movable page
+	 * In order to avoid having an already isolated movable folio
 	 * being (wrongly) re-isolated while it is under migration,
-	 * or to avoid attempting to isolate pages being released,
+	 * or to avoid attempting to isolate folios being released,
 	 * lets be sure we have the page lock
 	 * before proceeding with the movable page isolation steps.
 	 */
@@ -113,7 +111,7 @@ bool isolate_movable_page(struct page *page, isolate_mode_t mode)
 	if (!mops->isolate_page(&folio->page, mode))
 		goto out_no_isolated;
 
-	/* Driver shouldn't use PG_isolated bit of page->flags */
+	/* Driver shouldn't use PG_isolated bit of folio->flags */
 	WARN_ON_ONCE(folio_test_isolated(folio));
 	folio_set_isolated(folio);
 	folio_unlock(folio);
@@ -124,10 +122,17 @@ bool isolate_movable_page(struct page *page, isolate_mode_t mode)
 	folio_unlock(folio);
 out_putfolio:
 	folio_put(folio);
-out:
 	return false;
 }
 
+bool isolate_movable_page(struct page *page, isolate_mode_t mode)
+{
+	if (WARN_RATELIMIT(PageTail(page), "trying to isolate tail page"))
+		return false;
+
+	return isolate_movable_folio((struct folio *)page, mode);
+}
+
 static void putback_movable_folio(struct folio *folio)
 {
 	const struct movable_operations *mops = folio_movable_ops(folio);
-- 
2.27.0