From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: linux-nfs-owner@vger.kernel.org Received: from relay.parallels.com ([195.214.232.42]:44181 "EHLO relay.parallels.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753007Ab2EVP3j (ORCPT ); Tue, 22 May 2012 11:29:39 -0400 Message-ID: <4FBBB0DB.6050708@parallels.com> Date: Tue, 22 May 2012 19:29:31 +0400 From: Stanislav Kinsbursky MIME-Version: 1.0 To: "Myklebust, Trond" CC: "linux-nfs@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "devel@openvz.org" Subject: Re: [PATCH] NFS: init client before declaration References: <20120522124018.338.20817.stgit@localhost.localdomain> <1337696984.4269.4.camel@lade.trondhjem.org> <1337698816.4269.15.camel@lade.trondhjem.org> In-Reply-To: <1337698816.4269.15.camel@lade.trondhjem.org> Content-Type: text/plain; charset="UTF-8"; format=flowed Sender: linux-nfs-owner@vger.kernel.org List-ID: On 22.05.2012 19:00, Myklebust, Trond wrote: > On Tue, 2012-05-22 at 10:29 -0400, Trond Myklebust wrote: >> On Tue, 2012-05-22 at 16:40 +0400, Stanislav Kinsbursky wrote: >>> Client have to be initialized prior to adding it to per-net clients list, >>> because otherwise there are races, shown below: >>> >>> CPU#0 CPU#1 >>> _____ _____ >>> >>> nfs_get_client >>> nfs_alloc_client >>> list_add(..., nfs_client_list) >>> rpc_fill_super >>> rpc_pipefs_event >>> nfs_get_client_for_event >>> __rpc_pipefs_event >>> (clp->cl_rpcclient is uninitialized) >>> BUG() >>> init_client >>> clp->cl_rpcclient = ... >>> >> >> Why not simply change nfs_get_client_for_event() so that it doesn't >> touch nfs_clients that have clp->cl_cons_state!=NFS_CS_READY? >> >> That should ensure that it doesn't touch nfs_clients that failed to >> initialise and/or are still in the process of being initialised. > > ...actually, come to think of it. Why not just add a helper function > "bool nfs_client_active(const struct nfs_client *clp)" to > fs/nfs/client.c that does a call to > wait_event_killable(nfs_client_active_wq, clp->cl_cons_state< NFS_CS_INITING); > and checks the resulting value of clp->cl_cons_state? > Sorry, but I don't understand the idea... Where are you proposing to call this function? In __rpc_pipefs_event() prior to dentries creatios? -- Best regards, Stanislav Kinsbursky