NFSv4: Ensure we honour NFS_DELEGATION_RETURNING in nfs_inode_set_delegation()

Ensure that nfs_inode_set_delegation() doesn't inadvertently detach a
delegation that is already in the process of being returned.

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>

1 files changed, 4 insertions, 1 deletions

diff --git a/fs/nfs/delegation.c b/fs/nfs/delegation.c
index d9caf73eef48..5ca502b5f877 100644
--- a/fs/nfs/delegation.c
+++ b/fs/nfs/delegation.c
@@ -370,7 +370,10 @@ int nfs_inode_set_delegation(struct inode *inode, struct rpc_cred *cred, struct
                         delegation = NULL;
                         goto out;
                 }
-                freeme = nfs_detach_delegation_locked(nfsi, 
+                if (test_and_set_bit(NFS_DELEGATION_RETURNING,
+                                        &old_delegation->flags))
+                        goto out;
+                freeme = nfs_detach_delegation_locked(nfsi,
                                 old_delegation, clp);
                 if (freeme == NULL)
                         goto out;