Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754290AbaBDEVI (ORCPT ); Mon, 3 Feb 2014 23:21:08 -0500 Received: from mail-pd0-f174.google.com ([209.85.192.174]:37032 "EHLO mail-pd0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752464AbaBDEVD (ORCPT ); Mon, 3 Feb 2014 23:21:03 -0500 Date: Mon, 3 Feb 2014 20:20:21 -0800 (PST) From: Hugh Dickins X-X-Sender: hugh@eggly.anvils To: Andrew Morton cc: Weijie Yang , hughd@google.com, Minchan Kim , shli@kernel.org, Bob Liu , weijie.yang.kh@gmail.com, Seth Jennings , Heesub Shin , mquzik@redhat.com, Linux-MM , linux-kernel , stable@vger.kernel.org Subject: Re: [PATCH 3/8] mm/swap: prevent concurrent swapon on the same S_ISBLK blockdev In-Reply-To: <20140203153628.5e186b0e4e81400773faa7ac@linux-foundation.org> Message-ID: References: <000c01cf1b47$ce280170$6a780450$%yang@samsung.com> <20140203153628.5e186b0e4e81400773faa7ac@linux-foundation.org> User-Agent: Alpine 2.11 (LSU 23 2013-08-11) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 3 Feb 2014, Andrew Morton wrote: > On Mon, 27 Jan 2014 18:03:04 +0800 Weijie Yang wrote: > > > When swapon the same S_ISBLK blockdev concurrent, the allocated two > > swap_info could hold the same block_device, because claim_swapfile() > > allow the same holder(here, it is sys_swapon function). > > > > To prevent this situation, This patch adds swap_lock protect to ensure > > we can find this situation and return -EBUSY for one swapon call. > > > > As for S_ISREG swapfile, claim_swapfile() already prevent this scenario > > by holding inode->i_mutex. > > > > This patch is just for a rare scenario, aim to correct of code. > > > > hm, OK. Would it be saner to pass a unique `holder' to > claim_swapfile()? Say, `p'? > > Truly, I am fed up with silly swapon/swapoff races. How often does > anyone call these things? Let's slap a huge lock around the whole > thing and be done with it? That answer makes me sad: we can't be bothered to get it right, even when Weijie goes to the trouble of presenting a series to do so. But I sure don't deserve a vote until I've actually looked through it. Hugh -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/