From mboxrd@z Thu Jan 1 00:00:00 1970 From: "J. Bruce Fields" Subject: Re: [PATCH] svc: Clean up deferred requests on transport destruction Date: Wed, 7 Jan 2009 17:00:28 -0500 Message-ID: <20090107220028.GD965@fieldses.org> References: <496279CF.5050807@opengridcomputing.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Trond Myklebust , Linux NFS Mailing List To: Tom Tucker Return-path: Received: from mail.fieldses.org ([141.211.133.115]:44324 "EHLO fieldses.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1761614AbZAGWAb (ORCPT ); Wed, 7 Jan 2009 17:00:31 -0500 In-Reply-To: <496279CF.5050807@opengridcomputing.com> Sender: linux-nfs-owner@vger.kernel.org List-ID: On Mon, Jan 05, 2009 at 03:21:19PM -0600, Tom Tucker wrote: > Bruce, > > This patch replaces 2/3 of Trond's deferral cleanup patch. This shouldn't By that you mean patches 2 and 3, right? --b. > come across with the white-spaced munged. Please let me know if it does. > > Thanks, > Tom > > A race between svc_revisit and svc_delete_xprt can result in > deferred requests holding references on a transport that can never be > recovered because dead transports are not enqueued for subsequent > processing. > > Check for XPT_DEAD in revisit to clean up completing deferrals on a dead > transport and sweep a transport's deferred queue to do the same for queued > but unprocessed deferrals. > > Signed-off-by: Tom Tucker > > --- > net/sunrpc/svc_xprt.c | 25 ++++++++++++++++++------- > 1 files changed, 18 insertions(+), 7 deletions(-) > > diff --git a/net/sunrpc/svc_xprt.c b/net/sunrpc/svc_xprt.c > index bf5b5cd..e6e7e25 100644 > --- a/net/sunrpc/svc_xprt.c > +++ b/net/sunrpc/svc_xprt.c > @@ -837,6 +837,11 @@ static void svc_age_temp_xprts(unsigned long closure) > void svc_delete_xprt(struct svc_xprt *xprt) > { > struct svc_serv *serv = xprt->xpt_server; > + struct svc_deferred_req *dr; > + > + /* Only do this once */ > + if (test_and_set_bit(XPT_DEAD, &xprt->xpt_flags)) > + return; > > dprintk("svc: svc_delete_xprt(%p)\n", xprt); > xprt->xpt_ops->xpo_detach(xprt); > @@ -851,12 +856,16 @@ void svc_delete_xprt(struct svc_xprt *xprt) > * while still attached to a queue, the queue itself > * is about to be destroyed (in svc_destroy). > */ > - if (!test_and_set_bit(XPT_DEAD, &xprt->xpt_flags)) { > - BUG_ON(atomic_read(&xprt->xpt_ref.refcount) < 2); > - if (test_bit(XPT_TEMP, &xprt->xpt_flags)) > - serv->sv_tmpcnt--; > + if (test_bit(XPT_TEMP, &xprt->xpt_flags)) > + serv->sv_tmpcnt--; > + > + for (dr = svc_deferred_dequeue(xprt); dr; > + dr = svc_deferred_dequeue(xprt)) { > svc_xprt_put(xprt); > + kfree(dr); > } > + > + svc_xprt_put(xprt); > spin_unlock_bh(&serv->sv_lock); > } > > @@ -902,17 +911,19 @@ static void svc_revisit(struct cache_deferred_req *dreq, int too_many) > container_of(dreq, struct svc_deferred_req, handle); > struct svc_xprt *xprt = dr->xprt; > > - if (too_many) { > + spin_lock(&xprt->xpt_lock); > + set_bit(XPT_DEFERRED, &xprt->xpt_flags); > + if (too_many || test_bit(XPT_DEAD, &xprt->xpt_flags)) { > + spin_unlock(&xprt->xpt_lock); > + dprintk("revisit canceled\n"); > svc_xprt_put(xprt); > kfree(dr); > return; > } > dprintk("revisit queued\n"); > dr->xprt = NULL; > - spin_lock(&xprt->xpt_lock); > list_add(&dr->handle.recent, &xprt->xpt_deferred); > spin_unlock(&xprt->xpt_lock); > - set_bit(XPT_DEFERRED, &xprt->xpt_flags); > svc_xprt_enqueue(xprt); > svc_xprt_put(xprt); > }