From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx125.postini.com [74.125.245.125]) by kanga.kvack.org (Postfix) with SMTP id 0E4496B0034 for ; Sun, 7 Jul 2013 15:31:39 -0400 (EDT) Message-ID: <51D9C217.5030507@redhat.com> Date: Sun, 07 Jul 2013 15:31:35 -0400 From: Rik van Riel MIME-Version: 1.0 Subject: Re: [PATCH v2] swap: warn when a swap area overflows the maximum size References: <1373197450.26573.5.camel@warfang> <1373197978.26573.7.camel@warfang> <1373224421.26573.11.camel@warfang> In-Reply-To: <1373224421.26573.11.camel@warfang> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Raymond Jennings Cc: Valdis Kletnieks , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Andrew Morton On 07/07/2013 03:13 PM, Raymond Jennings wrote: > Turned the comparison around for clarity of "bigger than" > > No semantic changes, if it still compiles it should do the same thing so > I've omitted the testing this time. Will be happy to retest if required > but I'm on an atom 330 and kernel rebuilds are a nightmare. Added CC: Andrew Morton, since this should probably go into -mm :) > ---- > > swap: warn when a swap area overflows the maximum size > > It is possible to swapon a swap area that is too big for the pte width > to handle. > > Presently this failure happens silently. > > Instead, emit a diagnostic to warn the user. > > Signed-off-by: Raymond Jennings > Acked-by: Valdis Kletnieks Reviewed-by: Rik van Riel > diff --git a/mm/swapfile.c b/mm/swapfile.c > index 36af6ee..5a4ce53 100644 > --- a/mm/swapfile.c > +++ b/mm/swapfile.c > @@ -1953,6 +1953,12 @@ static unsigned long read_swap_header(struct > swap_info_struct *p, > */ > maxpages = swp_offset(pte_to_swp_entry( > swp_entry_to_pte(swp_entry(0, ~0UL)))) + 1; > + if (swap_header->info.last_page > maxpages) { > + printk(KERN_WARNING > + "Truncating oversized swap area, only using %luk > out of %luk > \n", > + maxpages << (PAGE_SHIFT - 10), > + swap_header->info.last_page << (PAGE_SHIFT - > 10)); > + } > if (maxpages > swap_header->info.last_page) { > maxpages = swap_header->info.last_page + 1; > /* p->max is an unsigned int: don't overflow it */ > > ---- > > Testing results, root prompt commands and kernel log messages: > > # lvresize /dev/system/swap --size 16G > # mkswap /dev/system/swap > # swapon /dev/system/swap > > Jul 7 04:27:22 warfang kernel: Adding 16777212k swap > on /dev/mapper/system-swap. Priority:-1 extents:1 across:16777212k > > # lvresize /dev/system/swap --size 16G > # mkswap /dev/system/swap > # swapon /dev/system/swap > > Jul 7 04:27:22 warfang kernel: Truncating oversized swap area, only > using 33554432k out of 67108860k > Jul 7 04:27:22 warfang kernel: Adding 33554428k swap > on /dev/mapper/system-swap. Priority:-1 extents:1 across:33554428k > > -- All rights reversed -- 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