mm/migrate.c: make putback_movable_page() static

Patch series "Cleanup and fixup for mm/migrate.c", v3.

This series contains cleanups to remove unnecessary VM_BUG_ON_PAGE and rc
!= MIGRATEPAGE_SUCCESS check.  Also use helper function to remove some
duplicated codes.  What's more, this fixes potential deadlock in NUMA
balancing shared exec THP case and so on.  More details can be found in
the respective changelogs.

This patch (of 5):

The putback_movable_page() is just called by putback_movable_pages() and
we know the page is locked and both PageMovable() and PageIsolated() is
checked right before calling putback_movable_page().  So we make it static
and remove all the 3 VM_BUG_ON_PAGE().

Link: https://lkml.kernel.org/r/20210325131524.48181-1-linmiaohe@huawei.com
Link: https://lkml.kernel.org/r/20210325131524.48181-2-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Yang Shi <shy828301@gmail.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: Rafael Aquini <aquini@redhat.com>
Cc: Alistair Popple <apopple@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/migrate.h

@@ -43,7 +43,6 @@ extern int migrate_pages(struct list_head *l, new_page_t new, free_page_t free,
 		unsigned long private, enum migrate_mode mode, int reason);
 extern struct page *alloc_migration_target(struct page *page, unsigned long private);
 extern int isolate_movable_page(struct page *page, isolate_mode_t mode);
-extern void putback_movable_page(struct page *page);
 
 extern void migrate_page_states(struct page *newpage, struct page *page);
 extern void migrate_page_copy(struct page *newpage, struct page *page);

mm/migrate.c

@@ -118,15 +118,10 @@ out:
 	return -EBUSY;
 }
 
-/* It should be called on page which is PG_movable */
-void putback_movable_page(struct page *page)
+static void putback_movable_page(struct page *page)
 {
 	struct address_space *mapping;
 
-	VM_BUG_ON_PAGE(!PageLocked(page), page);
-	VM_BUG_ON_PAGE(!PageMovable(page), page);
-	VM_BUG_ON_PAGE(!PageIsolated(page), page);
-
 	mapping = page_mapping(page);
 	mapping->a_ops->putback_page(page);
 	__ClearPageIsolated(page);