mm: change to return bool for isolate_movable_page()

Now the isolate_movable_page() can only return 0 or -EBUSY, and no users
will care about the negative return value, thus we can convert the
isolate_movable_page() to return a boolean value to make the code more
clear when checking the movable page isolation state.

No functional changes intended.

[akpm@linux-foundation.org: remove unneeded comment, per Matthew]
Link: https://lkml.kernel.org/r/cb877f73f4fff8d309611082ec740a7065b1ade0.1676424378.git.baolin.wang@linux.alibaba.com
Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Acked-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Reviewed-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Author: Baolin Wang

include/linux/migrate.h

@@ -71,7 +71,7 @@ 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,
 		unsigned int *ret_succeeded);
 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 bool isolate_movable_page(struct page *page, isolate_mode_t mode);
 
 int migrate_huge_page_move_mapping(struct address_space *mapping,
 		struct folio *dst, struct folio *src);
@@ -92,8 +92,8 @@ static inline int migrate_pages(struct list_head *l, new_page_t new,
 static inline struct page *alloc_migration_target(struct page *page,
 		unsigned long private)
 	{ return NULL; }
-static inline int isolate_movable_page(struct page *page, isolate_mode_t mode)
-	{ return -EBUSY; }
+static inline bool isolate_movable_page(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)

mm/compaction.c

@@ -976,7 +976,7 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
 					locked = NULL;
 				}
 
-				if (!isolate_movable_page(page, mode))
+				if (isolate_movable_page(page, mode))
 					goto isolate_success;
 			}
 

mm/memory-failure.c

@@ -2515,8 +2515,8 @@ static bool isolate_page(struct page *page, struct list_head *pagelist)
 		if (lru)
 			isolated = isolate_lru_page(page);
 		else
-			isolated = !isolate_movable_page(page,
-							 ISOLATE_UNEVICTABLE);
+			isolated = isolate_movable_page(page,
+							ISOLATE_UNEVICTABLE);
 
 		if (isolated) {
 			list_add(&page->lru, pagelist);

mm/memory_hotplug.c

@@ -1668,18 +1668,18 @@ do_migrate_range(unsigned long start_pfn, unsigned long end_pfn)
 		 * We can skip free pages. And we can deal with pages on
 		 * LRU and non-lru movable pages.
 		 */
-		if (PageLRU(page)) {
+		if (PageLRU(page))
 			isolated = isolate_lru_page(page);
-			ret = isolated ? 0 : -EBUSY;
-		} else
-			ret = isolate_movable_page(page, ISOLATE_UNEVICTABLE);
-		if (!ret) { /* Success */
+		else
+			isolated = isolate_movable_page(page, ISOLATE_UNEVICTABLE);
+		if (isolated) {
 			list_add_tail(&page->lru, &source);
 			if (!__PageMovable(page))
 				inc_node_page_state(page, NR_ISOLATED_ANON +
 						    page_is_file_lru(page));
 
 		} else {
+			ret = -EBUSY;
 			if (__ratelimit(&migrate_rs)) {
 				pr_warn("failed to isolate pfn %lx\n", pfn);
 				dump_page(page, "isolation failed");

mm/migrate.c

@@ -58,7 +58,7 @@
 
 #include "internal.h"
 
-int isolate_movable_page(struct page *page, isolate_mode_t mode)
+bool isolate_movable_page(struct page *page, isolate_mode_t mode)
 {
 	struct folio *folio = folio_get_nontail_page(page);
 	const struct movable_operations *mops;
@@ -119,14 +119,14 @@ int isolate_movable_page(struct page *page, isolate_mode_t mode)
 	folio_set_isolated(folio);
 	folio_unlock(folio);
 
-	return 0;
+	return true;
 
 out_no_isolated:
 	folio_unlock(folio);
 out_putfolio:
 	folio_put(folio);
 out:
-	return -EBUSY;
+	return false;
 }
 
 static void putback_movable_folio(struct folio *folio)