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Date: Tue, 26 Apr 2011 14:42:09 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: Wu Fengguang <fengguang.wu@intel.com>
Cc: Christoph Hellwig <hch@infradead.org>, Jan Kara <jack@suse.cz>,
        Mel Gorman <mel@linux.vnet.ibm.com>,
        Dave Chinner <david@fromorbit.com>,
        Trond Myklebust <Trond.Myklebust@netapp.com>,
        Itaru Kitayama <kitayama@cl.bb4u.ne.jp>,
        Minchan Kim <minchan.kim@gmail.com>,
        LKML <linux-kernel@vger.kernel.org>,
        "linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
        Linux Memory Management List <linux-mm@kvack.org>
Subject: Re: [PATCH 1/2] split inode_wb_list_lock into
 bdi_writeback.list_lock
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On Tue, 26 Apr 2011 22:42:19 +0800
Wu Fengguang <fengguang.wu@intel.com> wrote:

> @@ -55,13 +55,16 @@ EXPORT_SYMBOL(I_BDEV);
>  static void bdev_inode_switch_bdi(struct inode *inode,
>  			struct backing_dev_info *dst)
>  {
> -	spin_lock(&inode_wb_list_lock);
> +	struct backing_dev_info *old = inode->i_data.backing_dev_info;
> +
> +	bdi_lock_two(&old->wb, &dst->wb);
>  	spin_lock(&inode->i_lock);
>  	inode->i_data.backing_dev_info = dst;
>  	if (inode->i_state & I_DIRTY)
>  		list_move(&inode->i_wb_list, &dst->wb.b_dirty);
>  	spin_unlock(&inode->i_lock);
> -	spin_unlock(&inode_wb_list_lock);
> +	spin_unlock(&old->wb.list_lock);
> +	spin_unlock(&dst->wb.list_lock);
>  }

Has this patch been well tested under lockdep?