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Date: Fri, 12 Dec 2014 06:54:08 -0500
From: Jeff Layton <jeff.layton@...marydata.com>
To: Al Viro <viro@...IV.linux.org.uk>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>,
Bruce Fields <bfields@...ldses.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Linux NFS Mailing List <linux-nfs@...r.kernel.org>,
Tejun Heo <tj@...nel.org>, NeilBrown <neilb@...e.de>
Subject: Re: [PATCH v2 00/16] nfsd/sunrpc: add support for a workqueue-based
nfsd
On Fri, 12 Dec 2014 03:02:06 +0000
Al Viro <viro@...IV.linux.org.uk> wrote:
> On Thu, Dec 11, 2014 at 06:29:37PM -0800, Linus Torvalds wrote:
> > On Thu, Dec 11, 2014 at 6:12 PM, Al Viro <viro@...iv.linux.org.uk> wrote:
> > >
> > > Linus, do you see any problems with the following patch (against the mainline)?
> >
> > Not concpetually, but create_kthread() uses CLONE_FS, and I don't
> > think it's just umask that things like nfsd want to avoid sharing.
> > What about all the *other* fields?
> >
> > Just as an example: even if all the threads actually end up all having
> > the same global root, what about contention on 'fs->lock'?
> >
> > I have *not* looked at the details, and maybe there's some reason I'm
> > completely off, but it worries me.
>
> Umm... I would be very surprised if it turned out to be a problem.
> nfsd really doesn't give a fuck about its cwd and root - not in the
> thread side of things. And (un)exporting is (a) not on a hot path
> and (b) not done from a kernel thread anyway. fh_to_dentry and friends
> doesn't care about root/cwd, etc.
>
> I don't see anything that could cause that kind of issues.
I like the change overall -- it would certainly make my patch series
simpler, but what about pathwalking? We do take the fs->lock in
unlazy_walk. Is it possible we'd end up with more contention there?
--
Jeff Layton <jlayton@...marydata.com>
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