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Re: [patch] mm: fix lockless pagecache reordering bug (was Re: BUG: soft

To: Peter Klotz <peter.klotz@xxxxxx>
Subject: Re: [patch] mm: fix lockless pagecache reordering bug (was Re: BUG: soft lockup - is this XFS problem?)
From: Nick Piggin <npiggin@xxxxxxx>
Date: Tue, 6 Jan 2009 09:43:12 +0100
Cc: "Paul E. McKenney" <paulmck@xxxxxxxxxxxxxxxxxx>, Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>, stable@xxxxxxxxxx, Linux Memory Management List <linux-mm@xxxxxxxxx>, Christoph Hellwig <hch@xxxxxxxxxxxxx>, Roman Kononov <kernel@xxxxxxxxxxxxxxxx>, linux-kernel@xxxxxxxxxxxxxxx, xfs@xxxxxxxxxxx, Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
In-reply-to: <49631877.3090803@xxxxxx>
References: <49623384.2070801@xxxxxx> <20090105164135.GC32675@xxxxxxxxxxxxx> <alpine.LFD.2.00.0901050859430.3057@xxxxxxxxxxxxxxxxxxxxx> <20090105180008.GE32675@xxxxxxxxxxxxx> <alpine.LFD.2.00.0901051027011.3057@xxxxxxxxxxxxxxxxxxxxx> <20090105201258.GN6959@xxxxxxxxxxxxxxxxxx> <alpine.LFD.2.00.0901051224110.3057@xxxxxxxxxxxxxxxxxxxxx> <20090105215727.GQ6959@xxxxxxxxxxxxxxxxxx> <20090106020550.GA819@xxxxxxxxxxxxx> <49631877.3090803@xxxxxx>
User-agent: Mutt/1.5.9i
On Tue, Jan 06, 2009 at 09:38:15AM +0100, Peter Klotz wrote:
> >Index: linux-2.6/include/linux/radix-tree.h
> >===================================================================
> >--- linux-2.6.orig/include/linux/radix-tree.h
> >+++ linux-2.6/include/linux/radix-tree.h
> >@@ -136,7 +136,7 @@ do {                                              \
> >  */
> > 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;
> >
> >
> 
> The patch above fixes my problem. I did two complete test runs that 
> normally fail rather quickly.

OK, thanks for reporting and testing. 

I think this patch is a candidate for -stable too.

Thanks,
Nick

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