Re: [PATCH v4 1/1] dcache: Translating dentry into pathname without taking rename_lock

[Waiman Long <waiman.long@hp.com>]

On 09/09/2013 02:36 PM, Al Viro wrote:
> On Mon, Sep 09, 2013 at 07:21:11PM +0100, Al Viro wrote:
>> Actually, it's better for prepend_path() as well, because it's actually
>>
>> 	rcu_read_lock();
>> 	seq = read_seqbegin(&rename_lock);
>> again:
>> 	....
>> 	if (error)
>> 		goto done;
>> 	....
>> 	if (!seqretry_and_lock(&rename_lock, seq))
>> 		goto again;	/* now as writer */
>> done:
>> 	seqretry_done(&rename_lock, seq);
>> 	rcu_read_unlock();
>>
>> Posted variant will sometimes hit the following path:
>> 	* seq_readlock()
>> 	* start generating the output
>> 	* hit an error
>> [another process has taken and released rename_lock for some reason]
>> 	* hit read_seqretry_and_unlock(), which returns 1.
>> 	* retry everything with seq_writelock(), despite the error.
>>
>> It's not too horrible (we won't be looping indefinitely, ignoring error
>> all along), but it's certainly subtle enough...
> FWIW, what I propose is this (just the d_path-related parts):
>
>

I am fine with your proposed change as long as it gets the job done. It 
doesn't really matter if you do it or I do it.

Thank for taking the effort to make it better for us all.

-Longman