Return-Path: Received: from mx1.redhat.com ([209.132.183.28]:58564 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752816AbdKTVlS (ORCPT ); Mon, 20 Nov 2017 16:41:18 -0500 From: Scott Mayhew To: trond.myklebust@primarydata.com, anna.schumaker@netapp.com Cc: linux-nfs@vger.kernel.org Subject: [PATCH] nfs: fix a deadlock in nfs client initialization Date: Mon, 20 Nov 2017 16:41:18 -0500 Message-Id: <20171120214118.4240-1-smayhew@redhat.com> In-Reply-To: <20171120212819.3yxutvgmigxc7at5@tonberry.usersys.redhat.com> References: <20171120212819.3yxutvgmigxc7at5@tonberry.usersys.redhat.com> Sender: linux-nfs-owner@vger.kernel.org List-ID: The following deadlock can occur between a process waiting for a client to initialize in while walking the client list and another process waiting for the nfs_clid_init_mutex so it can initialize that client: Process 1 Process 2 --------- --------- spin_lock(&nn->nfs_client_lock); list_add_tail(&CLIENTA->cl_share_link, &nn->nfs_client_list); spin_unlock(&nn->nfs_client_lock); spin_lock(&nn->nfs_client_lock); list_add_tail(&CLIENTB->cl_share_link, &nn->nfs_client_list); spin_unlock(&nn->nfs_client_lock); mutex_lock(&nfs_clid_init_mutex); nfs41_walk_client_list(clp, result, cred); nfs_wait_client_init_complete(CLIENTA); (waiting for nfs_clid_init_mutex) Add and initilize the client with the nfs_clid_init_mutex held in order to prevent that deadlock. Signed-off-by: Scott Mayhew --- fs/nfs/client.c | 21 +++++++++++++++++++-- fs/nfs/nfs4state.c | 4 ---- 2 files changed, 19 insertions(+), 6 deletions(-) diff --git a/fs/nfs/client.c b/fs/nfs/client.c index 0ac2fb1..db38c47 100644 --- a/fs/nfs/client.c +++ b/fs/nfs/client.c @@ -60,6 +60,7 @@ static DECLARE_WAIT_QUEUE_HEAD(nfs_client_active_wq); static DEFINE_SPINLOCK(nfs_version_lock); static DEFINE_MUTEX(nfs_version_mutex); static LIST_HEAD(nfs_versions); +static DEFINE_MUTEX(nfs_clid_init_mutex); /* * RPC cruft for NFS @@ -386,7 +387,7 @@ nfs_found_client(const struct nfs_client_initdata *cl_init, */ struct nfs_client *nfs_get_client(const struct nfs_client_initdata *cl_init) { - struct nfs_client *clp, *new = NULL; + struct nfs_client *clp, *new = NULL, *result = NULL; struct nfs_net *nn = net_generic(cl_init->net, nfs_net_id); const struct nfs_rpc_ops *rpc_ops = cl_init->nfs_mod->rpc_ops; @@ -407,11 +408,27 @@ struct nfs_client *nfs_get_client(const struct nfs_client_initdata *cl_init) return nfs_found_client(cl_init, clp); } if (new) { + /* add and initialize the client with the + * nfs_clid_init_mutex held to prevent a deadlock + * with the server trunking detection + */ + spin_unlock(&nn->nfs_client_lock); + mutex_lock(&nfs_clid_init_mutex); + spin_lock(&nn->nfs_client_lock); + clp = nfs_match_client(cl_init); + if (clp) { + spin_unlock(&nn->nfs_client_lock); + mutex_unlock(&nfs_clid_init_mutex); + new->rpc_ops->free_client(new); + return nfs_found_client(cl_init, clp); + } list_add_tail(&new->cl_share_link, &nn->nfs_client_list); spin_unlock(&nn->nfs_client_lock); new->cl_flags = cl_init->init_flags; - return rpc_ops->init_client(new, cl_init); + result = rpc_ops->init_client(new, cl_init); + mutex_unlock(&nfs_clid_init_mutex); + return result; } spin_unlock(&nn->nfs_client_lock); diff --git a/fs/nfs/nfs4state.c b/fs/nfs/nfs4state.c index 54fd56d..668164e 100644 --- a/fs/nfs/nfs4state.c +++ b/fs/nfs/nfs4state.c @@ -77,8 +77,6 @@ const nfs4_stateid invalid_stateid = { .type = NFS4_INVALID_STATEID_TYPE, }; -static DEFINE_MUTEX(nfs_clid_init_mutex); - int nfs4_init_clientid(struct nfs_client *clp, struct rpc_cred *cred) { struct nfs4_setclientid_res clid = { @@ -2164,7 +2162,6 @@ int nfs4_discover_server_trunking(struct nfs_client *clp, clnt = clp->cl_rpcclient; i = 0; - mutex_lock(&nfs_clid_init_mutex); again: status = -ENOENT; cred = nfs4_get_clid_cred(clp); @@ -2232,7 +2229,6 @@ int nfs4_discover_server_trunking(struct nfs_client *clp, } out_unlock: - mutex_unlock(&nfs_clid_init_mutex); dprintk("NFS: %s: status = %d\n", __func__, status); return status; } -- 2.9.5