NFSv4: Don't call put_rpccred() under the rcu_read_lock()

commit 7c0af9ff upstream.

put_rpccred() can sleep.

Fixes: 8f649c37 ("NFSv4: Fix the locking in nfs_inode_reclaim_delegation()")
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
[lizf: Backported to 3.4: adjust context]
Signed-off-by: Zefan Li <lizefan@huawei.com>

fs/nfs/delegation.c

@@ -148,8 +148,8 @@ void nfs_inode_reclaim_delegation(struct inode *inode, struct rpc_cred *cred,
 				  &delegation->flags);
 			NFS_I(inode)->delegation_state = delegation->type;
 			spin_unlock(&delegation->lock);
-			put_rpccred(oldcred);
 			rcu_read_unlock();
+			put_rpccred(oldcred);
 		} else {
 			/* We appear to have raced with a delegation return. */
 			spin_unlock(&delegation->lock);