linux-ext4 - Re: [PATCH 1/4] vfs: introduce try_to_writeback_inodes_sb(

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Date:	Fri, 27 Apr 2012 16:06:00 +0800
From:	Miao Xie <miaoxie1984@...il.com>
To:	Josef Bacik <josef@...hat.com>
CC:	Xie Miao <miaoxie1984@...il.com>,
	Dave Chinner <david@...morbit.com>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Christoph Hellwig <hch@...radead.org>,
	Linux FSDevel <linux-fsdevel@...r.kernel.org>,
	Linux Btrfs <linux-btrfs@...r.kernel.org>,
	miaox@...fujitsu.com, Kamal Mostafa <kamal@...onical.com>,
	Linux Ext4 <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH 1/4] vfs: introduce try_to_writeback_inodes_sb(_nr)

于 2012年04月26日 23:12, Josef Bacik 写道:

> On Thu, Apr 26, 2012 at 03:55:52PM +0800, Xie Miao wrote:
>> On Thu, Apr 26, 2012 at 11:11 AM, Dave Chinner <david@...morbit.com> wrote:
>>>> writeback_inodes_sb(_nr) grabs s_umount lock when it want to start
>>>> writeback,
>>>> it may bring us deadlock problem when doing umount. So we introduce new
>>>> functions -- try_to_writeback_inodes_sb(_nr) -- which use
>>>> down_read_trylock()
>>>> instead of down_read() to avoid that deadlock problem.
>>>>
>>>> This idea came from Christoph Hellwig.
>>>> Some code is from the patch of Kamal Mostafa.
>>>
>>> This just re-implements writeback_inodes_[nr]_sb_if_idle() with a
>>> trylock instead of a blocking lock.
>>>
>>> Just replace the blocking lock in writeback_inodes_[nr]_sb_if_idle()
>>> with a trylock and use that.
>>
>> The change of these two functions is relative to three modules,  so I think
>> the patch set now is easy to be reviewed by the developers of each module.
>>
> 
> I agree with David, there's no sense in making something completely seperate,
> this function was introduced soley to kick off background writeout if we could
> with no garuntees, if the other users suddenly don't like the behavior they can
> creating something different for themselves.  Thanks,


OK, I'll make them together.

Thanks
Miao
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