From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f198.google.com (mail-pf0-f198.google.com [209.85.192.198]) by kanga.kvack.org (Postfix) with ESMTP id B9AA56B0038 for ; Tue, 21 Mar 2017 16:42:21 -0400 (EDT) Received: by mail-pf0-f198.google.com with SMTP id c23so328305478pfj.0 for ; Tue, 21 Mar 2017 13:42:21 -0700 (PDT) Received: from mga02.intel.com (mga02.intel.com. [134.134.136.20]) by mx.google.com with ESMTPS id u5si22488005pgg.140.2017.03.21.13.42.20 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 21 Mar 2017 13:42:20 -0700 (PDT) Message-ID: <1490128938.3567.2.camel@linux.intel.com> Subject: Re: [PATCH] mm, swap: Remove WARN_ON_ONCE() in free_swap_slot() From: Tim Chen Date: Tue, 21 Mar 2017 16:42:18 -0400 In-Reply-To: <20170320062657.26683-1-ying.huang@intel.com> References: <20170320062657.26683-1-ying.huang@intel.com> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: owner-linux-mm@kvack.org List-ID: To: "Huang, Ying" , Linus Torvalds Cc: Andrew Morton , Dave Hansen , Shaohua Li , Rik van Riel , Michal Hocko , linux-mm@kvack.org, linux-kernel@vger.kernel.org On Mon, 2017-03-20 at 14:26 +0800, Huang, Ying wrote: > From: Huang Ying > > Before commit 452b94b8c8c7 ("mm/swap: don't BUG_ON() due to > uninitialized swap slot cache"), the following bug is reported, > > A ------------[ cut here ]------------ > A kernel BUG at mm/swap_slots.c:270! > A invalid opcode: 0000 [#1] SMP > A CPU: 5 PID: 1745 Comm: (sd-pam) Not tainted 4.11.0-rc1-00243-g24c534bb161b #1 > A Hardware name: System manufacturer System Product Name/Z170-K, BIOS > 1803 05/06/2016 > A RIP: 0010:free_swap_slot+0xba/0xd0 > A Call Trace: > A A A swap_free+0x36/0x40 > A A A do_swap_page+0x360/0x6d0 > A A A __handle_mm_fault+0x880/0x1080 > A A A handle_mm_fault+0xd0/0x240 > A A A __do_page_fault+0x232/0x4d0 > A A A do_page_fault+0x20/0x70 > A A A page_fault+0x22/0x30 > A ---[ end trace aefc9ede53e0ab21 ]--- > > This is raised by the BUG_ON(!swap_slot_cache_initialized) in > free_swap_slot().A A This is incorrect, because even if the swap slots > cache fails to be initialized, the swap should operate properly > without the swap slots cache.A A 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. > This replaces my previous patch to replace the BUG_ON. Acked-by: Tim Chen > Reported-by: Linus Torvalds > Cc: Tim Chen > Cc: Michal Hocko > Signed-off-by: "Huang, Ying" > --- > A mm/swap_slots.c | 2 -- > A 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) > A { > A struct swap_slots_cache *cache; > A > - WARN_ON_ONCE(!swap_slot_cache_initialized); > - > A cache = &get_cpu_var(swp_slots); > A if (use_swap_slot_cache && cache->slots_ret) { > A spin_lock_irq(&cache->free_lock); -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org