From: Minchan Kim <minchan.kim@gmail.com>
To: Ted Ts'o <tytso@mit.edu>,
linux-ext4@vger.kernel.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org,
Andreas Dilger <adilger.kernel@dilger.ca>,
Paul McKenney <paulmck@linux.vnet.ib
Subject: Re: [BUG?] [Ext4] INFO: suspicious rcu_dereference_check() usage
Date: Mon, 22 Nov 2010 00:39:49 +0900 [thread overview]
Message-ID: <20101121153949.GD20947@barrios-desktop> (raw)
In-Reply-To: <20101121133024.GF23423@thunk.org>
On Sun, Nov 21, 2010 at 08:30:24AM -0500, Ted Ts'o wrote:
> On Sun, Nov 21, 2010 at 07:26:11PM +0800, Arun Bhanu wrote:
> > I saw this in kernel log messages while testing 2.6.37-rc2. I think it
> > appeared while mounting an external hard-disk. I can't seem to
> > reproduce it.
>
> I could be wrong but this looks like it's a bug in mm/migrate.c in
> migrate_page_move_mapping(): it is calling radix_tree_lookup_slot()
> without first taking an rcu_read_lock().
>
> It was triggered by a memory allocation out of ext4_fill_super(),
> which then triggered a memory compaction/migration, but I don't
> believe it's otherwise related to the ext4 code.
>
> Over to the linux-mm folks for confirmation...
I think it's no problem.
That's because migration always holds lock_page on the file page.
So the page couldn't remove from radix.
--
Kind regards,
Minchan Kim
WARNING: multiple messages have this Message-ID (diff)
From: Minchan Kim <minchan.kim@gmail.com>
To: "Ted Ts'o" <tytso@mit.edu>,
linux-ext4@vger.kernel.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org,
Andreas Dilger <adilger.kernel@dilger.ca>,
Paul McKenney <paulmck@linux.vnet.ibm.com>,
Eric Sandeen <sandeen@redhat.com>
Subject: Re: [BUG?] [Ext4] INFO: suspicious rcu_dereference_check() usage
Date: Mon, 22 Nov 2010 00:39:49 +0900 [thread overview]
Message-ID: <20101121153949.GD20947@barrios-desktop> (raw)
In-Reply-To: <20101121133024.GF23423@thunk.org>
On Sun, Nov 21, 2010 at 08:30:24AM -0500, Ted Ts'o wrote:
> On Sun, Nov 21, 2010 at 07:26:11PM +0800, Arun Bhanu wrote:
> > I saw this in kernel log messages while testing 2.6.37-rc2. I think it
> > appeared while mounting an external hard-disk. I can't seem to
> > reproduce it.
>
> I could be wrong but this looks like it's a bug in mm/migrate.c in
> migrate_page_move_mapping(): it is calling radix_tree_lookup_slot()
> without first taking an rcu_read_lock().
>
> It was triggered by a memory allocation out of ext4_fill_super(),
> which then triggered a memory compaction/migration, but I don't
> believe it's otherwise related to the ext4 code.
>
> Over to the linux-mm folks for confirmation...
I think it's no problem.
That's because migration always holds lock_page on the file page.
So the page couldn't remove from radix.
--
Kind regards,
Minchan Kim
WARNING: multiple messages have this Message-ID (diff)
From: Minchan Kim <minchan.kim@gmail.com>
To: Ted Ts'o <tytso@mit.edu>,
linux-ext4@vger.kernel.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org,
Andreas Dilger <adilger.kernel@dilger.ca>,
Paul McKenney <paulmck@linux.vnet.ibm.com>,
Eric Sandeen <sandeen@redhat.com>
Subject: Re: [BUG?] [Ext4] INFO: suspicious rcu_dereference_check() usage
Date: Mon, 22 Nov 2010 00:39:49 +0900 [thread overview]
Message-ID: <20101121153949.GD20947@barrios-desktop> (raw)
In-Reply-To: <20101121133024.GF23423@thunk.org>
On Sun, Nov 21, 2010 at 08:30:24AM -0500, Ted Ts'o wrote:
> On Sun, Nov 21, 2010 at 07:26:11PM +0800, Arun Bhanu wrote:
> > I saw this in kernel log messages while testing 2.6.37-rc2. I think it
> > appeared while mounting an external hard-disk. I can't seem to
> > reproduce it.
>
> I could be wrong but this looks like it's a bug in mm/migrate.c in
> migrate_page_move_mapping(): it is calling radix_tree_lookup_slot()
> without first taking an rcu_read_lock().
>
> It was triggered by a memory allocation out of ext4_fill_super(),
> which then triggered a memory compaction/migration, but I don't
> believe it's otherwise related to the ext4 code.
>
> Over to the linux-mm folks for confirmation...
I think it's no problem.
That's because migration always holds lock_page on the file page.
So the page couldn't remove from radix.
--
Kind regards,
Minchan Kim
--
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next prev parent reply other threads:[~2010-11-21 15:39 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-11-21 11:26 [BUG?] [Ext4] INFO: suspicious rcu_dereference_check() usage Arun Bhanu
2010-11-21 13:30 ` Ted Ts'o
2010-11-21 13:30 ` Ted Ts'o
2010-11-21 13:30 ` Ted Ts'o
2010-11-21 15:39 ` Minchan Kim [this message]
2010-11-21 15:39 ` Minchan Kim
2010-11-21 15:39 ` Minchan Kim
2010-11-21 17:37 ` Ted Ts'o
2010-11-21 17:37 ` Ted Ts'o
2010-11-22 0:38 ` Minchan Kim
2010-11-22 0:38 ` Minchan Kim
2010-11-22 0:38 ` Minchan Kim
2010-11-22 3:31 ` Milton Miller
2010-11-22 6:16 ` Paul E. McKenney
2010-12-07 19:01 ` [BUG?] memory hotplug: include/linux/radix-tree.h:145 invoked rcu_dereference_check() without protection! Gerald Schaefer
2010-12-08 1:19 ` KAMEZAWA Hiroyuki
2010-12-16 13:50 ` Gerald Schaefer
2010-12-17 0:04 ` Minchan Kim
2010-12-17 0:04 ` Minchan Kim
2010-12-17 5:47 ` Paul E. McKenney
2010-12-17 5:47 ` Paul E. McKenney
2010-12-17 5:59 ` Eric Dumazet
2010-12-17 5:59 ` Eric Dumazet
2010-12-17 15:08 ` Minchan Kim
2010-12-17 16:03 ` Paul E. McKenney
2010-12-17 16:03 ` Paul E. McKenney
2010-12-17 8:39 ` Mel Gorman
2010-12-17 8:39 ` Mel Gorman
2010-12-17 9:28 ` Mel Gorman
2010-12-17 15:22 ` Minchan Kim
2010-12-17 15:13 ` Minchan Kim
2010-12-17 15:13 ` Minchan Kim
2010-12-17 16:01 ` Paul E. McKenney
2010-12-17 16:01 ` Paul E. McKenney
2010-11-23 7:16 ` [BUG?] [Ext4] INFO: suspicious rcu_dereference_check() usage KOSAKI Motohiro
2010-11-23 7:16 ` KOSAKI Motohiro
2010-11-23 7:16 ` KOSAKI Motohiro
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