linux-kernel - Re: [RFC][PATCH] radix_tree: radix_tree_gang_lookup_tag

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Message-Id: <20110125135345.ca4bfd79.toshi.okajima@jp.fujitsu.com>
Date:	Tue, 25 Jan 2011 13:53:45 +0900
From:	Toshiyuki Okajima <toshi.okajima@...fujitsu.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	linux-ext4@...r.kernel.org, Jan Kara <jack@....cz>
Subject: Re: [RFC][PATCH] radix_tree: radix_tree_gang_lookup_tag_slot may
 not return forever.

Hi Andrew,

On Fri, 21 Jan 2011 15:31:54 -0800
Andrew Morton <akpm@...ux-foundation.org> wrote:

> On Fri, 21 Jan 2011 15:34:31 +0900
> Toshiyuki Okajima <toshi.okajima@...fujitsu.com> wrote:
> 
> > Hi.
> > 
> > I executed fsstress and then found that the system hung up.
> > At that time, I took the crash dump. Here is the backtrace of the process
> > which causes this hangup.
> > 
> > [long description]
> >
> > --- a/lib/radix-tree.c
> > +++ b/lib/radix-tree.c
> > @@ -736,10 +736,11 @@ next:
> >  		}
> >  	}
> >  	/*
> > -	 * The iftag must have been set somewhere because otherwise
> > -	 * we would return immediated at the beginning of the function
> > +	 * We need not to tag the root tag if there is no tag which is set with
> > +	 * settag within the range from *first_indexp to last_index.
> >  	 */
> > -	root_tag_set(root, settag);
> > +	if (tagged > 0)
> > +		root_tag_set(root, settag);
> >  	*first_indexp = index;
> >  
> >  	return tagged;
> 
> Thanks.
> 

> It should be fairly simple to reproduce this hang with the userspace
> test harness (http://userweb.kernel.org/~akpm/stuff/rtth.tar.gz) and to
> then demonstrate that the fix fixes it.
> 
> If you have time, could you please do that and then send the rtth
> updates to me?
> 
I add regression2_test for this bug into your testset (rtth.tar.gz).
This is originated from regression1_test.

Regards,
Toshiyuki Okajima

Download attachment "rtth.patch" of type "application/octet-stream" (5413 bytes)