Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752154Ab3GGLoR (ORCPT ); Sun, 7 Jul 2013 07:44:17 -0400 Received: from mail-pb0-f48.google.com ([209.85.160.48]:51604 "EHLO mail-pb0-f48.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751651Ab3GGLoO (ORCPT ); Sun, 7 Jul 2013 07:44:14 -0400 Subject: [PATCH] swap: warn when a swap area overflows the maximum size From: Raymond Jennings To: Rik van Riel Cc: linux-kernel@vger.kernel.org, linux-mm@vger.kernel.org, Valdis Kletnieks Content-Type: text/plain; charset="UTF-8" Date: Sun, 07 Jul 2013 04:44:10 -0700 Message-ID: <1373197450.26573.5.camel@warfang> Mime-Version: 1.0 X-Mailer: Evolution 2.32.3 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1891 Lines: 60 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 ---- 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 (maxpages < swap_header->info.last_page) { + 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 -- 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/