linux-kernel - [PATCH 4/9] mm/z3fold: throw warning on failure of trylock_page in z3fold

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Date:   Fri, 29 Apr 2022 14:40:46 +0800
From:   Miaohe Lin <linmiaohe@...wei.com>
To:     <akpm@...ux-foundation.org>, <vitaly.wool@...sulko.com>
CC:     <linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>,
        <linmiaohe@...wei.com>
Subject: [PATCH 4/9] mm/z3fold: throw warning on failure of trylock_page in z3fold_alloc

If trylock_page fails, the page won't be non-lru movable page. When this
page is freed via free_z3fold_page, it will trigger bug on PageMovable
check in __ClearPageMovable. Throw warning on failure of trylock_page to
guard against such rare case just as what zsmalloc does.

Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>
---
 mm/z3fold.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/mm/z3fold.c b/mm/z3fold.c
index 4e6814c5694f..b3b4e65c107f 100644
--- a/mm/z3fold.c
+++ b/mm/z3fold.c
@@ -1122,10 +1122,9 @@ static int z3fold_alloc(struct z3fold_pool *pool, size_t size, gfp_t gfp,
 		__SetPageMovable(page, pool->inode->i_mapping);
 		unlock_page(page);
 	} else {
-		if (trylock_page(page)) {
-			__SetPageMovable(page, pool->inode->i_mapping);
-			unlock_page(page);
-		}
+		WARN_ON(!trylock_page(page));
+		__SetPageMovable(page, pool->inode->i_mapping);
+		unlock_page(page);
 	}
 	z3fold_page_lock(zhdr);
 
-- 
2.23.0