From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757182Ab2DYRaI (ORCPT ); Wed, 25 Apr 2012 13:30:08 -0400 Received: from fieldses.org ([174.143.236.118]:33259 "EHLO fieldses.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756525Ab2DYRaG (ORCPT ); Wed, 25 Apr 2012 13:30:06 -0400 Date: Wed, 25 Apr 2012 13:30:05 -0400 From: "J. Bruce Fields" To: Stanislav Kinsbursky Cc: linux-nfs@vger.kernel.org, linux-kernel@vger.kernel.org, devel@openvz.org Subject: Re: [PATCH v2] SUNRPC: skip dead but not buried clients on PipeFS events Message-ID: <20120425173005.GD751@fieldses.org> References: <20120420141042.7205.62608.stgit@localhost6.localdomain6> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20120420141042.7205.62608.stgit@localhost6.localdomain6> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Apr 20, 2012 at 06:11:02PM +0400, Stanislav Kinsbursky wrote: > v2: atomic_inc_return() was replaced by atomic_inc_not_zero(). > > These clients can't be safely dereferenced if their counter in 0. I'm pretty confused by how these notifiers work.... rpc_release_client decrements cl_count to zero temporarily, to have it immediately re-incremented by rpc_free_auth. So if we're called concurrently with rpc_release_client then it's sort of random whether someone gets this callback. Is that a problem? Also, is this an existing bug? (In which case Trond should take it now.) --b. > > Signed-off-by: Stanislav Kinsbursky > > --- > net/sunrpc/clnt.c | 3 ++- > 1 files changed, 2 insertions(+), 1 deletions(-) > > diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c > index 6797246..d10ebc4 100644 > --- a/net/sunrpc/clnt.c > +++ b/net/sunrpc/clnt.c > @@ -218,7 +218,8 @@ static struct rpc_clnt *rpc_get_client_for_event(struct net *net, int event) > if (((event == RPC_PIPEFS_MOUNT) && clnt->cl_dentry) || > ((event == RPC_PIPEFS_UMOUNT) && !clnt->cl_dentry)) > continue; > - atomic_inc(&clnt->cl_count); > + if (atomic_inc_not_zero(&clnt->cl_count) == 0) > + continue; > spin_unlock(&sn->rpc_client_lock); > return clnt; > } >