Re: [PATCH v3] SUNRPC: set desired file system root beforeconnecting local transports

From: J. Bruce Fields
Date: Fri Oct 26 2012 - 13:52:59 EST


On Wed, Oct 10, 2012 at 02:32:28PM +0400, Stanislav Kinsbursky wrote:
> 10.10.2012 05:23, J. Bruce Fields ÐÐÑÐÑ:
> >On Tue, Oct 09, 2012 at 03:47:42PM -0700, Eric W. Biederman wrote:
> >>"J. Bruce Fields" <bfields@xxxxxxxxxxxx> writes:
> >>
> >>>On Tue, Oct 09, 2012 at 01:20:48PM -0700, Eric W. Biederman wrote:
> >>>>"Myklebust, Trond" <Trond.Myklebust@xxxxxxxxxx> writes:
> >>>>
> >>>>>On Tue, 2012-10-09 at 15:35 -0400, J. Bruce Fields wrote:
> >>>>>>Cc'ing Eric since I seem to recall he suggested doing it this way?
> >>>>
> >>>>Yes. On second look setting fs->root won't work. We need to change fs.
> >>>>The problem is that by default all kernel threads share fs so changing
> >>>>fs->root will have non-local consequences.
> >>>
> >>>Oh, huh. And we can't "unshare" it somehow?
> >>
> >>I don't fully understand how nfs uses kernel threads and work queues.
> >>My general understanding is work queues reuse their kernel threads
> >>between different users. So it is mostly a don't pollute your
> >>environment thing. If there was a dedicated kernel thread for each
> >>environment this would be trivial.
> >>
> >>What I was suggesting here is changing task->fs instead of
> >>task->fs.root. That should just require task_lock().
> >
> >Oh, OK, got it--if that works, great.
> >
>
> The main problem with swapping fs struct is actually the same as in
> root swapping. I.e. routines for copy fs_struct are not exported.
> It could be done on place, but I don't think, that Al Viro would
> support such implementation.
> Trond?

It seems like we got stalled here.... Could you go ahead and try a
patch, and see what people think?

--b.
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