linux-ext4 - Re: [PATCH]JBD2/JBD: race condition while writing updates to journal

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Date:	Sun, 21 Jun 2009 20:09:15 -0400
From:	Theodore Tso <tytso@....edu>
To:	dingdinghua <dingdinghua85@...il.com>
Cc:	linux-ext4@...r.kernel.org
Subject: Re: [PATCH]JBD2/JBD: race condition while writing updates to
	journal

On Mon, Jun 22, 2009 at 12:22:03AM +0800, dingdinghua wrote:
> 
> At committing phase, we call jbd2_journal_write_metadata_buffer to
> prepare log block's buffer_head, in this function, new_bh->b_data is set
> to b_frozen_data or bh_in->b_data. We call "jbd_unlock_bh_state(bh_in)"
> too early, since at this point , we haven't file bh_in to BJ_shadow list,
> and we may set new_bh->b_data to bh_in->b_data, at this time, another
> thread may call get write access of bh_in, modify bh_in->b_data and
> dirty it. So , if new_bh->b_data is set to bh_in->b_data, the committing
> transaction may flush the newly modified buffer content to disk,
> preserve work done in jbd2_journal_get_write_access is useless. jbd also
> has this problem.
> 
> here is the patch based on kernel version 2.6.30:

This patch is completely whitespace damaged.  Could you resend it
using a mail user agent that doesn't damage patches, please?    Thanks!!

      	     	  	     	     	    - Ted
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