NFSv4: Fix a race in nfs_inode_reclaim_delegation()

If we race with a delegreturn before taking the spin lock, we
currently end up dropping the delegation stateid.

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
Tested-by: Oleg Drokin <green@linuxhacker.ru>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

diff --git a/fs/nfs/delegation.c b/fs/nfs/delegation.c
index 5de4cfb..094e0ef 100644 (file)
--- a/fs/nfs/delegation.c
+++ b/fs/nfs/delegation.c
@@ -195,15 +195,13 @@ void nfs_inode_reclaim_delegation(struct inode *inode, struct rpc_cred *cred,
                        rcu_read_unlock();
                        put_rpccred(oldcred);
                        trace_nfs4_reclaim_delegation(inode, res->delegation_type);
-               } else {
-                       /* We appear to have raced with a delegation return. */
-                       spin_unlock(&delegation->lock);
-                       rcu_read_unlock();
-                       nfs_inode_set_delegation(inode, cred, res);
+                       return;
                }
-       } else {
-               rcu_read_unlock();
+               /* We appear to have raced with a delegation return. */
+               spin_unlock(&delegation->lock);
        }
+       rcu_read_unlock();
+       nfs_inode_set_delegation(inode, cred, res);
 }
 
 static int nfs_do_return_delegation(struct inode *inode, struct nfs_delegation *delegation, int issync)