From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg0-f69.google.com (mail-pg0-f69.google.com [74.125.83.69]) by kanga.kvack.org (Postfix) with ESMTP id 30DCA6B025F for ; Tue, 31 Oct 2017 03:46:12 -0400 (EDT) Received: by mail-pg0-f69.google.com with SMTP id j3so16123027pga.5 for ; Tue, 31 Oct 2017 00:46:12 -0700 (PDT) Received: from mx2.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id b5si914985ple.404.2017.10.31.00.46.11 for (version=TLS1 cipher=AES128-SHA bits=128/128); Tue, 31 Oct 2017 00:46:11 -0700 (PDT) Date: Tue, 31 Oct 2017 08:46:07 +0100 From: Michal Hocko Subject: Re: [PATCH -mm -V2] mm, swap: Fix false error message in __swp_swapcount() Message-ID: <20171031074607.exg2nh6qvnvkqu3s@dhcp22.suse.cz> References: <20171027055327.5428-1-ying.huang@intel.com> <20171029235713.GA4332@bbox> <20171030080230.apijacsx7fd3qeox@dhcp22.suse.cz> <20171031021702.GA942@bbox> <20171031073107.x5rpkf4emf74ymyk@dhcp22.suse.cz> <20171031073710.GA857@bbox> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20171031073710.GA857@bbox> Sender: owner-linux-mm@kvack.org List-ID: To: Minchan Kim Cc: "Huang, Ying" , Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Huang Ying , Tim Chen , stable@vger.kernel.org, Christian Kujau On Tue 31-10-17 16:37:10, Minchan Kim wrote: > On Tue, Oct 31, 2017 at 08:31:07AM +0100, Michal Hocko wrote: > > On Tue 31-10-17 11:17:02, Minchan Kim wrote: > > > On Mon, Oct 30, 2017 at 09:02:30AM +0100, Michal Hocko wrote: > > > > On Mon 30-10-17 08:57:13, Minchan Kim wrote: > > > > [...] > > > > > Although it's better than old, we can make it simple, still. > > > > > > > > > > diff --git a/include/linux/swapops.h b/include/linux/swapops.h > > > > > index 291c4b534658..f50d5a48f03a 100644 > > > > > --- a/include/linux/swapops.h > > > > > +++ b/include/linux/swapops.h > > > > > @@ -41,6 +41,13 @@ static inline unsigned swp_type(swp_entry_t entry) > > > > > return (entry.val >> SWP_TYPE_SHIFT(entry)); > > > > > } > > > > > > > > > > +extern struct swap_info_struct *swap_info[]; > > > > > + > > > > > +static inline struct swap_info_struct *swp_si(swp_entry_t entry) > > > > > +{ > > > > > + return swap_info[swp_type(entry)]; > > > > > +} > > > > > + > > > > > /* > > > > > * Extract the `offset' field from a swp_entry_t. The swp_entry_t is in > > > > > * arch-independent format > > > > > diff --git a/mm/swap_state.c b/mm/swap_state.c > > > > > index 378262d3a197..a0fe2d54ad09 100644 > > > > > --- a/mm/swap_state.c > > > > > +++ b/mm/swap_state.c > > > > > @@ -554,6 +554,7 @@ struct page *swapin_readahead(swp_entry_t entry, gfp_t gfp_mask, > > > > > struct vm_area_struct *vma, unsigned long addr) > > > > > { > > > > > struct page *page; > > > > > + struct swap_info_struct *si = swp_si(entry); > > > > > > > > Aren't you accessing beyond the array here? > > > > > > I couldn't understand what you intend. Could you explain what case does it accesses > > > beyond the arrary? > > > > what if swp_type > nr_swapfiles > > Logicall, it shouldn't be happen but it's a bug once it happens. > Such a bug can happen everywhere. > Why do you want to take care in this logic? You are right. It was my misunderstanding of the patch. I though the readahead swap entries could overflow swp_type as well as the offset. My bad. -- Michal Hocko SUSE Labs -- 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