From: Rik van Riel <riel@redhat.com>
To: Raymond Jennings <shentino@gmail.com>
Cc: Valdis Kletnieks <valdis.kletnieks@vt.edu>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH v2] swap: warn when a swap area overflows the maximum size
Date: Sun, 07 Jul 2013 15:31:35 -0400 [thread overview]
Message-ID: <51D9C217.5030507@redhat.com> (raw)
In-Reply-To: <1373224421.26573.11.camel@warfang>
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 <shentino@gmail.com>
> Acked-by: Valdis Kletnieks <valdis.kletnieks@vt.edu>
Reviewed-by: Rik van Riel <riel@redhat.com>
> 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
>
>
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next prev parent reply other threads:[~2013-07-07 19:31 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <1373197450.26573.5.camel@warfang>
2013-07-07 11:52 ` [PATCH] swap: warn when a swap area overflows the maximum size (resent) Raymond Jennings
2013-07-07 11:58 ` Raymond Jennings
2013-07-07 12:01 ` Raymond Jennings
2013-07-07 19:13 ` [PATCH v2] swap: warn when a swap area overflows the maximum size Raymond Jennings
2013-07-07 19:31 ` Rik van Riel [this message]
2013-07-07 20:56 ` Raymond Jennings
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