From mboxrd@z Thu Jan  1 00:00:00 1970
From: Jan Kara <jack@suse.cz>
Subject: Re: [PATCH 7/17] fsfreeze: fix nested freezing of sb-less bdevs
Date: Wed, 9 Jan 2013 17:24:38 +0100
Message-ID: <20130109162438.GC17353@quack.suse.cz>
References: <1357557492.8183.1.camel@nexus.lab.ntt.co.jp>
 <1357558238.8183.12.camel@nexus.lab.ntt.co.jp>
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Cc: Al Viro <viro@zeniv.linux.org.uk>,
	Josef Bacik <jbacik@fusionio.com>,
	Eric Sandeen <sandeen@redhat.com>,
	Dave Chinner <dchinner@redhat.com>,
	Christoph Hellwig <hch@infradead.org>, Jan Kara <jack@suse.cz>,
	Luiz Capitulino <lcapitulino@redhat.com>,
	linux-fsdevel@vger.kernel.org
To: Fernando Luis =?iso-8859-1?Q?V=E1zquez?= Cao
	<fernando_b1@lab.ntt.co.jp>
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On Mon 07-01-13 20:30:38, Fernando Luis V=E1zquez Cao wrote:
> If a frozen bdev does not have a filesystem sitting on top of it any =
subsequent
> nested freeze will cause a null pointer dereference because freeze_bd=
ev()
> calls drop_super() unconditionally. drop_super() should be called onl=
y when
> there is a superblock to drop.
  Looks good. You can add:
Reviewed-by: Jan Kara <jack@suse.cz>

									Honza
>=20
> Cc: linux-fsdevel@vger.kernel.org
> Cc: Josef Bacik <jbacik@fusionio.com>
> Cc: Eric Sandeen <sandeen@redhat.com>
> Cc: Christoph Hellwig <hch@infradead.org>
> Cc: Jan Kara <jack@suse.cz>
> Cc: Dave Chinner <dchinner@redhat.com>
> Cc: Luiz Capitulino <lcapitulino@redhat.com>
> Signed-off-by: Fernando Luis Vazquez Cao <fernando@oss.ntt.co.jp>
> ---
>=20
> diff -urNp linux-3.8-rc1-orig/fs/block_dev.c linux-3.8-rc1/fs/block_d=
ev.c
> --- linux-3.8-rc1-orig/fs/block_dev.c	2012-12-25 11:38:05.072018000 +=
0900
> +++ linux-3.8-rc1/fs/block_dev.c	2012-12-25 11:50:43.060018000 +0900
> @@ -227,8 +227,8 @@ struct super_block *freeze_bdev(struct b
>  		 * to freeze_bdev grab an active reference and only the last
>  		 * thaw_bdev drops it.
>  		 */
> -		sb =3D get_super(bdev);
> -		drop_super(sb);
> +		if ((sb =3D get_super(bdev)) !=3D NULL)
> +			drop_super(sb);
>  		mutex_unlock(&bdev->bd_fsfreeze_mutex);
>  		return sb;
>  	}
>=20
>=20
--=20
Jan Kara <jack@suse.cz>
SUSE Labs, CR
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