NFS: Fix an rcu deadlock in nfs_delegation_find_inode()

I was able to reproduce this pretty regularily using xfstests
generic/013 on NFS v4.0.

Reported-by: Ross Zwisler <Ross.Zwisler@linux.intel.com>
Fixes: 6c342655022d (NFSv4: Return NFS4ERR_DELAY when a delegation recall fails due to igrab())
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

diff --git a/fs/nfs/delegation.c b/fs/nfs/delegation.c
index bbd0465535ebd9e433a812d60ab345161ef736b3..f033f3a69a3bcf7259192a9e062d7af295f90639 100644 (file)
--- a/fs/nfs/delegation.c
+++ b/fs/nfs/delegation.c
@@ -883,8 +883,10 @@ struct inode *nfs_delegation_find_inode(struct nfs_client *clp,
        rcu_read_lock();
        list_for_each_entry_rcu(server, &clp->cl_superblocks, client_link) {
                res = nfs_delegation_find_inode_server(server, fhandle);
-               if (res != ERR_PTR(-ENOENT))
+               if (res != ERR_PTR(-ENOENT)) {
+                       rcu_read_unlock();
                        return res;
+               }
        }
        rcu_read_unlock();
        return ERR_PTR(-ENOENT);