[PATCH] mm: zsmalloc: update the comment about pool lock

[Barry Song (Xiaomi)]

Update the comment to reflect that `zs_free()` can be lockless when
`ZS_OBJ_CLASS_BITS` applies.

Suggested-by: Sergey Senozhatsky <senozhatsky@xxxxxxxxxxxx>
Signed-off-by: Barry Song (Xiaomi) <baohua@xxxxxxxxxx>
---
 mm/zsmalloc.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
index 3d566a3ee96f..b5eadee0e8f0 100644
--- a/mm/zsmalloc.c
+++ b/mm/zsmalloc.c
@@ -1865,8 +1865,8 @@ static int zs_page_migrate(struct page *newpage, struct page *page,
 	pool = zspage->pool;
 
 	/*
-	 * The pool migrate_lock protects the race between zpage migration
-	 * and zs_free.
+	 * The pool migrate_lock protects against races between zpage migration
+	 * and zs_free(), but only when ZS_OBJ_CLASS_BITS does not apply.
 	 */
 	write_lock(&pool->lock);
 	class = zspage_class(pool, zspage);
@@ -2045,8 +2045,9 @@ static unsigned long __zs_compact(struct zs_pool *pool,
 	unsigned long pages_freed = 0;
 
 	/*
-	 * protect the race between zpage migration and zs_free
-	 * as well as zpage allocation/free
+	 * Protect against races between zpage migration and zs_free()
+	 * (only when ZS_OBJ_CLASS_BITS does not apply), as well as
+	 * zpage allocation and free.
 	 */
 	write_lock(&pool->lock);
 	spin_lock(&class->lock);
-- 
2.39.3 (Apple Git-146)