linux-ext4 - Re: [PATCH 1/2] ext4: fix journal ref count in move_extent_par

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Message-ID: <4A76A00F.30506@rs.jp.nec.com>
Date:	Mon, 03 Aug 2009 17:30:07 +0900
From:	Akira Fujita <a-fujita@...jp.nec.com>
To:	Peng Tao <bergwolf@...il.com>
CC:	linux-ext4@...r.kernel.org, "Theodore Ts'o" <tytso@....edu>
Subject: Re: [PATCH 1/2] ext4: fix journal ref count in move_extent_par_page

Hi Peng,

Peng Tao wrote:
> move_extent_par_page calls a_ops->write_begin() to increase journal handler's
> reference count. However, if either mext_replace_branches() or ext4_get_block
> fails, the increased reference count isn't decreased. This will cause later
> umounting of the fs forever hangs. The patch addresses the issue by calling
> ext4_journal_stop() if page is not NULL (which means a_ops->write_end() isn't
> invoked).

In case mext_replaced_branches() or ext4_get_block failed,
ext4_journal_stop() is called at out2 label(*)
and then journal reference counter is decreased.
Therefore I think this fix is not necessary.

static int
move_extent_par_page(struct file *o_filp, struct inode *donor_inode,
                  pgoff_t orig_page_offset, int data_offset_in_page,
                  int block_len_in_page, int uninit)
<snip>

out:
        if (unlikely(page)) {
                if (PageLocked(page))
                        unlock_page(page);
                page_cache_release(page);
        }
out2:
*       ext4_journal_stop(handle);

        return ret < 0 ? ret : 0;
}

Regards,
Akira Fujita
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