From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752827AbdCTG16 (ORCPT ); Mon, 20 Mar 2017 02:27:58 -0400 Received: from mga06.intel.com ([134.134.136.31]:61034 "EHLO mga06.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750989AbdCTG1z (ORCPT ); Mon, 20 Mar 2017 02:27:55 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.36,191,1486454400"; d="scan'208";a="78284416" From: "Huang, Ying" To: Linus Torvalds Cc: Andrew Morton , Dave Hansen , Shaohua Li , Rik van Riel , Huang Ying , Tim Chen , Michal Hocko , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: [PATCH] mm, swap: Remove WARN_ON_ONCE() in free_swap_slot() Date: Mon, 20 Mar 2017 14:26:42 +0800 Message-Id: <20170320062657.26683-1-ying.huang@intel.com> X-Mailer: git-send-email 2.11.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Huang Ying Before commit 452b94b8c8c7 ("mm/swap: don't BUG_ON() due to uninitialized swap slot cache"), the following bug is reported, ------------[ cut here ]------------ kernel BUG at mm/swap_slots.c:270! invalid opcode: 0000 [#1] SMP CPU: 5 PID: 1745 Comm: (sd-pam) Not tainted 4.11.0-rc1-00243-g24c534bb161b #1 Hardware name: System manufacturer System Product Name/Z170-K, BIOS 1803 05/06/2016 RIP: 0010:free_swap_slot+0xba/0xd0 Call Trace: swap_free+0x36/0x40 do_swap_page+0x360/0x6d0 __handle_mm_fault+0x880/0x1080 handle_mm_fault+0xd0/0x240 __do_page_fault+0x232/0x4d0 do_page_fault+0x20/0x70 page_fault+0x22/0x30 ---[ end trace aefc9ede53e0ab21 ]--- This is raised by the BUG_ON(!swap_slot_cache_initialized) in free_swap_slot(). This is incorrect, because even if the swap slots cache fails to be initialized, the swap should operate properly without the swap slots cache. And the use_swap_slot_cache check later in the function will protect the uninitialized swap slots cache case. In commit 452b94b8c8c7, the BUG_ON() is replaced by WARN_ON_ONCE(). In the patch, the WARN_ON_ONCE() is removed too. Reported-by: Linus Torvalds Cc: Tim Chen Cc: Michal Hocko Signed-off-by: "Huang, Ying" --- mm/swap_slots.c | 2 -- 1 file changed, 2 deletions(-) diff --git a/mm/swap_slots.c b/mm/swap_slots.c index 7ebb23836f68..b1ccb58ad397 100644 --- a/mm/swap_slots.c +++ b/mm/swap_slots.c @@ -267,8 +267,6 @@ int free_swap_slot(swp_entry_t entry) { struct swap_slots_cache *cache; - WARN_ON_ONCE(!swap_slot_cache_initialized); - cache = &get_cpu_var(swp_slots); if (use_swap_slot_cache && cache->slots_ret) { spin_lock_irq(&cache->free_lock); -- 2.11.0