From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754007Ab2B0QVh (ORCPT ); Mon, 27 Feb 2012 11:21:37 -0500 Received: from mx2.netapp.com ([216.240.18.37]:10028 "EHLO mx2.netapp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753960Ab2B0QVe (ORCPT ); Mon, 27 Feb 2012 11:21:34 -0500 X-IronPort-AV: E=Sophos;i="4.73,491,1325491200"; d="scan'208";a="628887010" From: "Myklebust, Trond" To: Stanislav Kinsbursky CC: "linux-nfs@vger.kernel.org" , "xemul@parallels.com" , "neilb@suse.de" , "netdev@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "jbottomley@parallels.com" , "bfields@fieldses.org" , "davem@davemloft.net" , "devel@openvz.org" Subject: Re: [PATCH v2 1/4] SUNRPC: release per-net clients lock before calling PipeFS dentries creation Thread-Topic: [PATCH v2 1/4] SUNRPC: release per-net clients lock before calling PipeFS dentries creation Thread-Index: AQHM9Weod0HJbXoOhkm4LDxKtXHHipZRcwyA Date: Mon, 27 Feb 2012 16:21:32 +0000 Message-ID: <1330359695.5541.45.camel@lade.trondhjem.org> References: <20120227154713.7941.17963.stgit@localhost6.localdomain6> <20120227155055.7941.18741.stgit@localhost6.localdomain6> In-Reply-To: <20120227155055.7941.18741.stgit@localhost6.localdomain6> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [10.104.60.115] Content-Type: text/plain; charset="utf-8" Content-ID: <6090798A0FDE1447ABDA8D6F1B94D7D3@tahoe.netapp.com> MIME-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from base64 to 8bit by nfs id q1RGM0KY019328 On Mon, 2012-02-27 at 19:50 +0400, Stanislav Kinsbursky wrote: > Lockdep is sad otherwise, because inode mutex is taken on PipeFS dentry > creation, which can be called on mount notification, where this per-net client > lock is taken on clients list walk. > > Signed-off-by: Stanislav Kinsbursky > > --- > net/sunrpc/clnt.c | 10 +++++++--- > 1 files changed, 7 insertions(+), 3 deletions(-) > > diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c > index bb7ed2f3..ddb5741 100644 > --- a/net/sunrpc/clnt.c > +++ b/net/sunrpc/clnt.c > @@ -84,7 +84,7 @@ static void rpc_register_client(struct rpc_clnt *clnt) > struct sunrpc_net *sn = net_generic(clnt->cl_xprt->xprt_net, sunrpc_net_id); > > spin_lock(&sn->rpc_client_lock); > - list_add(&clnt->cl_clients, &sn->all_clients); > + list_add_tail(&clnt->cl_clients, &sn->all_clients); > spin_unlock(&sn->rpc_client_lock); > } > > @@ -208,15 +208,19 @@ static int rpc_pipefs_event(struct notifier_block *nb, unsigned long event, > void *ptr) > { > struct super_block *sb = ptr; > - struct rpc_clnt *clnt; > + struct rpc_clnt *clnt, *tmp; > int error = 0; > struct sunrpc_net *sn = net_generic(sb->s_fs_info, sunrpc_net_id); > > spin_lock(&sn->rpc_client_lock); > - list_for_each_entry(clnt, &sn->all_clients, cl_clients) { > + list_for_each_entry_safe(clnt, tmp, &sn->all_clients, cl_clients) { > + atomic_inc(&clnt->cl_count); > + spin_unlock(&sn->rpc_client_lock); > error = __rpc_pipefs_event(clnt, event, sb); > + rpc_release_client(clnt); > if (error) > break; > + spin_lock(&sn->rpc_client_lock); > } > spin_unlock(&sn->rpc_client_lock); > return error; > This won't be safe. Nothing guarantees that 'tmp' remains valid after you drop the spin_lock. I think you rather need to add a check for whether clnt->cl_dentry is in the right state (NULL if RPC_PIPEFS_UMOUNT or non-NULL if RPC_PIPEFS_MOUNT) before deciding whether or not to atomic_inc() and drop the lock, so that you can restart the loop after calling __rpc_pipefs_event(). -- Trond Myklebust Linux NFS client maintainer NetApp Trond.Myklebust@netapp.com www.netapp.com {.n++%ݶw{.n+{G{ayʇڙ,jfhz_(階ݢj"mG?&~iOzv^m ?I