NFSv4: Fix up another delegation related race

When we can update_open_stateid(), we need to be certain that we don't
race with a delegation return. While we could do this by grabbing the
nfs_client->cl_lock, a dedicated spin lock in the delegation structure
will scale better.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

1 files changed, 6 insertions, 1 deletions

diff --git a/fs/nfs/delegation.c b/fs/nfs/delegation.c
index cc563cfa6940..e0cb4ee3b23e 100644
--- a/fs/nfs/delegation.c
+++ b/fs/nfs/delegation.c
@@ -140,13 +140,17 @@ static struct nfs_delegation *nfs_detach_delegation_locked(struct nfs_inode *nfs
 
         if (delegation == NULL)
                 goto nomatch;
+        spin_lock(&delegation->lock);
         if (stateid != NULL && memcmp(delegation->stateid.data, stateid->data,
                                 sizeof(delegation->stateid.data)) != 0)
-                goto nomatch;
+                goto nomatch_unlock;
         list_del_rcu(&delegation->super_list);
         nfsi->delegation_state = 0;
         rcu_assign_pointer(nfsi->delegation, NULL);
+        spin_unlock(&delegation->lock);
         return delegation;
+nomatch_unlock:
+        spin_unlock(&delegation->lock);
 nomatch:
         return NULL;
 }
@@ -172,6 +176,7 @@ int nfs_inode_set_delegation(struct inode *inode, struct rpc_cred *cred, struct
         delegation->change_attr = nfsi->change_attr;
         delegation->cred = get_rpccred(cred);
         delegation->inode = inode;
+        spin_lock_init(&delegation->lock);
 
         spin_lock(&clp->cl_lock);
         if (rcu_dereference(nfsi->delegation) != NULL) {