Re: [PATCH v4 1/1] dcache: Translating dentry into pathname withouttaking rename_lock

[Waiman Long]

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
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