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Subject[PATCH v2.6.34-rc5 04/12] NFSv4: Fix the locking in nfs_inode_reclaim_delegation()
Date
From: Trond Myklebust <Trond.Myklebust@netapp.com>

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 <Trond.Myklebust@netapp.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
---
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)
--
1.7.0


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