From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Howells Subject: [PATCH 1/2] NFSv4: Fix the locking in nfs_inode_reclaim_delegation() Date: Tue, 20 Apr 2010 11:26:08 +0100 Message-ID: <20100420102608.31956.93404.stgit@warthog.procyon.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Cc: paulmck@linux.vnet.ibm.com, dhowells@redhat.com, linux-nfs@vger.kernel.org, linux-kernel@vger.kernel.org To: Trond.Myklebust@netapp.com Return-path: Received: from mx1.redhat.com ([209.132.183.28]:47250 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754419Ab0DTK02 (ORCPT ); Tue, 20 Apr 2010 06:26:28 -0400 Sender: linux-nfs-owner@vger.kernel.org List-ID: From: Trond Myklebust Ensure that we correctly rcu-dereference the delegation itself, and that we protect against removal while we're changing the contents. Signed-off-by: Trond Myklebust Signed-off-by: David Howells --- fs/nfs/delegation.c | 42 ++++++++++++++++++++++++++++-------------- 1 files changed, 28 insertions(+), 14 deletions(-) diff --git a/fs/nfs/delegation.c b/fs/nfs/delegation.c index 1567124..8d9ec49 100644 --- a/fs/nfs/delegation.c +++ b/fs/nfs/delegation.c @@ -129,21 +129,35 @@ again: */ void nfs_inode_reclaim_delegation(struct inode *inode, struct rpc_cred *cred, struct nfs_openres *res) { - struct nfs_delegation *delegation = NFS_I(inode)->delegation; - struct rpc_cred *oldcred; + struct nfs_delegation *delegation; + struct rpc_cred *oldcred = NULL; - if (delegation == NULL) - return; - memcpy(delegation->stateid.data, res->delegation.data, - sizeof(delegation->stateid.data)); - delegation->type = res->delegation_type; - delegation->maxsize = res->maxsize; - oldcred = delegation->cred; - delegation->cred = get_rpccred(cred); - clear_bit(NFS_DELEGATION_NEED_RECLAIM, &delegation->flags); - NFS_I(inode)->delegation_state = delegation->type; - smp_wmb(); - put_rpccred(oldcred); + rcu_read_lock(); + delegation = rcu_dereference(NFS_I(inode)->delegation); + if (delegation != NULL) { + spin_lock(&delegation->lock); + if (delegation->inode != NULL) { + memcpy(delegation->stateid.data, res->delegation.data, + sizeof(delegation->stateid.data)); + delegation->type = res->delegation_type; + delegation->maxsize = res->maxsize; + oldcred = delegation->cred; + delegation->cred = get_rpccred(cred); + clear_bit(NFS_DELEGATION_NEED_RECLAIM, + &delegation->flags); + NFS_I(inode)->delegation_state = delegation->type; + spin_unlock(&delegation->lock); + put_rpccred(oldcred); + rcu_read_unlock(); + } else { + /* We appear to have raced with a delegation return. */ + spin_unlock(&delegation->lock); + rcu_read_unlock(); + nfs_inode_set_delegation(inode, cred, res); + } + } else { + rcu_read_unlock(); + } } static int nfs_do_return_delegation(struct inode *inode, struct nfs_delegation *delegation, int issync)