Merge tag 'nfs-for-3.8-2' of git://git.linux-nfs.org/projects/trondmy/linux-nfs

Pull NFS client bugfixes from Trond Myklebust:

 - Fix a permissions problem when opening NFSv4 files that only have the
   exec bit set.

 - Fix a couple of typos in pNFS (inverted logic), and the mount parsing
   (missing pointer dereference).

 - Work around a series of deadlock issues due to workqueues using
   struct work_struct pointer address comparisons in the re-entrancy
   tests.  Ensure that we don't free struct work_struct prematurely if
   our work function involves waiting for completion of other work items
   (e.g. by calling rpc_shutdown_client).

 - Revert the part of commit 168e4b3 that is causing unnecessary
   warnings to be issued in the nfsd callback code.

* tag 'nfs-for-3.8-2' of git://git.linux-nfs.org/projects/trondmy/linux-nfs:
  nfs: avoid dereferencing null pointer in initiate_bulk_draining
  SUNRPC: Partial revert of commit 168e4b39d1afb79a7e3ea6c3bb246b4c82c6bdb9
  NFS: Ensure that we free the rpc_task after read and write cleanups are done
  SUNRPC: Ensure that we free the rpc_task after cleanups are done
  nfs: fix null checking in nfs_get_option_str()
  pnfs: Increase the refcount when LAYOUTGET fails the first time
  NFS: Fix access to suid/sgid executables

2 files changed, 23 insertions, 9 deletions

diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c
index 822f020fa7f..1915ffe598e 100644
--- a/net/sunrpc/clnt.c
+++ b/net/sunrpc/clnt.c
@@ -610,11 +610,6 @@ EXPORT_SYMBOL_GPL(rpc_killall_tasks);
  */
 void rpc_shutdown_client(struct rpc_clnt *clnt)
 {
-	/*
-	 * To avoid deadlock, never call rpc_shutdown_client from a
-	 * workqueue context!
-	 */
-	WARN_ON_ONCE(current->flags & PF_WQ_WORKER);
 	might_sleep();
 
 	dprintk_rcu("RPC:       shutting down %s client for %s\n",
diff --git a/net/sunrpc/sched.c b/net/sunrpc/sched.c
index d17a704aaf5..b4133bd1391 100644
--- a/net/sunrpc/sched.c
+++ b/net/sunrpc/sched.c
@@ -934,16 +934,35 @@ struct rpc_task *rpc_new_task(const struct rpc_task_setup *setup_data)
 	return task;
 }
 
+/*
+ * rpc_free_task - release rpc task and perform cleanups
+ *
+ * Note that we free up the rpc_task _after_ rpc_release_calldata()
+ * in order to work around a workqueue dependency issue.
+ *
+ * Tejun Heo states:
+ * "Workqueue currently considers two work items to be the same if they're
+ * on the same address and won't execute them concurrently - ie. it
+ * makes a work item which is queued again while being executed wait
+ * for the previous execution to complete.
+ *
+ * If a work function frees the work item, and then waits for an event
+ * which should be performed by another work item and *that* work item
+ * recycles the freed work item, it can create a false dependency loop.
+ * There really is no reliable way to detect this short of verifying
+ * every memory free."
+ *
+ */
 static void rpc_free_task(struct rpc_task *task)
 {
-	const struct rpc_call_ops *tk_ops = task->tk_ops;
-	void *calldata = task->tk_calldata;
+	unsigned short tk_flags = task->tk_flags;
+
+	rpc_release_calldata(task->tk_ops, task->tk_calldata);
 
-	if (task->tk_flags & RPC_TASK_DYNAMIC) {
+	if (tk_flags & RPC_TASK_DYNAMIC) {
 		dprintk("RPC: %5u freeing task\n", task->tk_pid);
 		mempool_free(task, rpc_task_mempool);
 	}
-	rpc_release_calldata(tk_ops, calldata);
 }
 
 static void rpc_async_release(struct work_struct *work)