From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pd0-f181.google.com (mail-pd0-f181.google.com [209.85.192.181]) by kanga.kvack.org (Postfix) with ESMTP id 61C396B0035 for ; Mon, 3 Feb 2014 23:21:03 -0500 (EST) Received: by mail-pd0-f181.google.com with SMTP id y10so7697848pdj.12 for ; Mon, 03 Feb 2014 20:21:03 -0800 (PST) Received: from mail-pa0-x231.google.com (mail-pa0-x231.google.com [2607:f8b0:400e:c03::231]) by mx.google.com with ESMTPS id bq5si22964532pbb.78.2014.02.03.20.21.02 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Mon, 03 Feb 2014 20:21:02 -0800 (PST) Received: by mail-pa0-f49.google.com with SMTP id hz1so7930485pad.22 for ; Mon, 03 Feb 2014 20:21:02 -0800 (PST) Date: Mon, 3 Feb 2014 20:20:21 -0800 (PST) From: Hugh Dickins 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> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: 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 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, 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