From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx150.postini.com [74.125.245.150]) by kanga.kvack.org (Postfix) with SMTP id 6EF2E6B0033 for ; Sun, 7 Jul 2013 07:53:01 -0400 (EDT) Received: by mail-pa0-f50.google.com with SMTP id fb1so3441446pad.23 for ; Sun, 07 Jul 2013 04:53:00 -0700 (PDT) Subject: [PATCH] swap: warn when a swap area overflows the maximum size (resent) From: Raymond Jennings In-Reply-To: <1373197450.26573.5.camel@warfang> References: <1373197450.26573.5.camel@warfang> Content-Type: text/plain; charset="UTF-8" Date: Sun, 07 Jul 2013 04:52:58 -0700 Message-ID: <1373197978.26573.7.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 Silly me, wrong email address On Sun, 2013-07-07 at 04:44 -0700, Raymond Jennings wrote: 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, 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