From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx148.postini.com [74.125.245.148]) by kanga.kvack.org (Postfix) with SMTP id 806D76B0034 for ; Sun, 7 Jul 2013 16:56:50 -0400 (EDT) Received: by mail-pd0-f179.google.com with SMTP id q10so3439494pdj.10 for ; Sun, 07 Jul 2013 13:56:49 -0700 (PDT) Subject: Re: [PATCH v2] swap: warn when a swap area overflows the maximum size From: Raymond Jennings In-Reply-To: <51D9C217.5030507@redhat.com> References: <1373197450.26573.5.camel@warfang> <1373197978.26573.7.camel@warfang> <1373224421.26573.11.camel@warfang> <51D9C217.5030507@redhat.com> Content-Type: text/plain; charset="UTF-8" Date: Sun, 07 Jul 2013 13:56:45 -0700 Message-ID: <1373230605.26573.17.camel@warfang> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Rik van Riel Cc: Valdis Kletnieks , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Andrew Morton Screwed up and didn't attach my fixed test log to the second version. See below. On Sun, 2013-07-07 at 15:31 -0400, Rik van Riel wrote: > 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 On Sun, 2013-07-07 at 04:52 -0700, Raymond Jennings wrote: > # lvresize /dev/system/swap --size 16G Typo in the second test. The first line should read: # lvresize /dev/system/swap --size 64G First ever serious patch, got excited and burned the copypasta. > # mkswap /dev/system/swap > # swapon /dev/system/swap > > # 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 > > > > > > -- 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