Return-Path: linux-kernel-owner@vger.kernel.org From: Jeff Layton Date: Fri, 12 Dec 2014 06:54:08 -0500 To: Al Viro Cc: Linus Torvalds , Bruce Fields , Linux Kernel Mailing List , Linux NFS Mailing List , Tejun Heo , NeilBrown Subject: Re: [PATCH v2 00/16] nfsd/sunrpc: add support for a workqueue-based nfsd Message-ID: <20141212065408.2f76c41e@tlielax.poochiereds.net> In-Reply-To: <20141212030206.GA22149@ZenIV.linux.org.uk> References: <1418238480-18857-1-git-send-email-jlayton@primarydata.com> <20141212021241.GA5944@ZenIV.linux.org.uk> <20141212030206.GA22149@ZenIV.linux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: On Fri, 12 Dec 2014 03:02:06 +0000 Al Viro 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 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