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Subject: Re: 2.6.17-rc5-mm1
From: Martin Schwidefsky <schwidefsky@de.ibm.com>
Reply-To: schwidefsky@de.ibm.com
To: Hugh Dickins <hugh@veritas.com>
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Organization: IBM Corporation
Date: Tue, 06 Jun 2006 20:05:55 +0200
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On Tue, 2006-06-06 at 18:59 +0100, Hugh Dickins wrote:
> Even s390 is okay, isn't it?  MartinS's swp_type returns the highest
> type, 31, corresponding to 32 types, as on every other architecture.
> You and I and Martin Bligh would prefer this patch...
> 
> 
> Remove unnecessary obfuscation from sys_swapon's range check on swap
> type, which blew up causing memory corruption once swapless migration
> made MAX_SWAPFILES no longer 2 ^ MAX_SWAPFILES_SHIFT.
> 
> Signed-off-by: Hugh Dickins <hugh@veritas.com>
> 
> --- 2.6.17-rc5-mm3/mm/swapfile.c	2006-06-04 11:52:47.000000000 +0100
> +++ linux/mm/swapfile.c	2006-06-06 18:53:40.000000000 +0100
> @@ -1404,7 +1404,7 @@ asmlinkage long sys_swapon(const char __
>  	 * from the initial ~0UL that can't be encoded in either the
>  	 * swp_entry_t or the architecture definition of a swap pte.
>  	 */
> -	if (type > swp_type(pte_to_swp_entry(swp_entry_to_pte(swp_entry(~0UL,0))))) {
> +	if (type >= MAX_SWAPFILES) {
>  		spin_unlock(&swap_lock);
>  		goto out;
>  	}

As long as nobody will have the smart idea to increase MAX_SWAPFILES to
more than 32 I'm fine with it.

-- 
blue skies,
  Martin.

Martin Schwidefsky
Linux for zSeries Development & Services
IBM Deutschland Entwicklung GmbH

"Reality continues to ruin my life." - Calvin.