linux-kernel - Re: [patch] mm: fix lockless pagecache reordering bug (was Re: BUG: soft lockup

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Date:	Tue, 06 Jan 2009 10:16:32 -0600
From:	Roman Kononov <kononov@...l.net>
To:	Nick Piggin <npiggin@...e.de>
CC:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Peter Klotz <peter.klotz@....at>, stable@...nel.org,
	Linux Memory Management List <linux-mm@...ck.org>,
	Christoph Hellwig <hch@...radead.org>,
	Roman Kononov <kernel@...onov.ftml.net>,
	linux-kernel@...r.kernel.org, xfs@....sgi.com,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [patch] mm: fix lockless pagecache reordering bug (was Re: BUG:
 soft lockup - is this XFS problem?)

On 2009-01-05 20:05 Nick Piggin said the following:
> Subject: mm lockless pagecache barrier fix
>  static inline void *radix_tree_deref_slot(void **pslot)
>  {
> -	void *ret = *pslot;
> +	void *ret = rcu_dereference(*pslot);
>  	if (unlikely(radix_tree_is_indirect_ptr(ret)))
>  		ret = RADIX_TREE_RETRY;
>  	return ret;

3 systems are working fine for a few hours with the patch. They would 
fail within 20 minutes without it.

Thanks.

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