WorkStruct: Pass the work_struct pointer instead of context data

Pass the work_struct pointer to the work function rather than context data.
The work function can use container_of() to work out the data.

For the cases where the container of the work_struct may go away the moment the
pending bit is cleared, it is made possible to defer the release of the
structure by deferring the clearing of the pending bit.

To make this work, an extra flag is introduced into the management side of the
work_struct.  This governs auto-release of the structure upon execution.

Ordinarily, the work queue executor would release the work_struct for further
scheduling or deallocation by clearing the pending bit prior to jumping to the
work function.  This means that, unless the driver makes some guarantee itself
that the work_struct won't go away, the work function may not access anything
else in the work_struct or its container lest they be deallocated..  This is a
problem if the auxiliary data is taken away (as done by the last patch).

However, if the pending bit is *not* cleared before jumping to the work
function, then the work function *may* access the work_struct and its container
with no problems.  But then the work function must itself release the
work_struct by calling work_release().

In most cases, automatic release is fine, so this is the default.  Special
initiators exist for the non-auto-release case (ending in _NAR).


Signed-Off-By: David Howells <dhowells@redhat.com>

5 files changed, 25 insertions, 21 deletions

diff --git a/net/sunrpc/cache.c b/net/sunrpc/cache.c
index d5725cb1491..d96fd466a9a 100644
--- a/net/sunrpc/cache.c
+++ b/net/sunrpc/cache.c
@@ -284,8 +284,8 @@ static struct file_operations cache_file_operations;
 static struct file_operations content_file_operations;
 static struct file_operations cache_flush_operations;
 
-static void do_cache_clean(void *data);
-static DECLARE_DELAYED_WORK(cache_cleaner, do_cache_clean, NULL);
+static void do_cache_clean(struct work_struct *work);
+static DECLARE_DELAYED_WORK(cache_cleaner, do_cache_clean);
 
 void cache_register(struct cache_detail *cd)
 {
@@ -461,7 +461,7 @@ static int cache_clean(void)
 /*
  * We want to regularly clean the cache, so we need to schedule some work ...
  */
-static void do_cache_clean(void *data)
+static void do_cache_clean(struct work_struct *work)
 {
 	int delay = 5;
 	if (cache_clean() == -1)
diff --git a/net/sunrpc/rpc_pipe.c b/net/sunrpc/rpc_pipe.c
index 97be3f7fed4..49dba5febbb 100644
--- a/net/sunrpc/rpc_pipe.c
+++ b/net/sunrpc/rpc_pipe.c
@@ -54,10 +54,11 @@ static void rpc_purge_list(struct rpc_inode *rpci, struct list_head *head,
 }
 
 static void
-rpc_timeout_upcall_queue(void *data)
+rpc_timeout_upcall_queue(struct work_struct *work)
 {
 	LIST_HEAD(free_list);
-	struct rpc_inode *rpci = (struct rpc_inode *)data;
+	struct rpc_inode *rpci =
+		container_of(work, struct rpc_inode, queue_timeout.work);
 	struct inode *inode = &rpci->vfs_inode;
 	void (*destroy_msg)(struct rpc_pipe_msg *);
 
@@ -838,7 +839,7 @@ init_once(void * foo, kmem_cache_t * cachep, unsigned long flags)
 		rpci->pipelen = 0;
 		init_waitqueue_head(&rpci->waitq);
 		INIT_DELAYED_WORK(&rpci->queue_timeout,
-				    rpc_timeout_upcall_queue, rpci);
+				    rpc_timeout_upcall_queue);
 		rpci->ops = NULL;
 	}
 }
diff --git a/net/sunrpc/sched.c b/net/sunrpc/sched.c
index a1ab4eed41f..eff44bcdc95 100644
--- a/net/sunrpc/sched.c
+++ b/net/sunrpc/sched.c
@@ -41,7 +41,7 @@ static mempool_t	*rpc_buffer_mempool __read_mostly;
 
 static void			__rpc_default_timer(struct rpc_task *task);
 static void			rpciod_killall(void);
-static void			rpc_async_schedule(void *);
+static void			rpc_async_schedule(struct work_struct *);
 
 /*
  * RPC tasks sit here while waiting for conditions to improve.
@@ -305,7 +305,7 @@ static void rpc_make_runnable(struct rpc_task *task)
 	if (RPC_IS_ASYNC(task)) {
 		int status;
 
-		INIT_WORK(&task->u.tk_work, rpc_async_schedule, (void *)task);
+		INIT_WORK(&task->u.tk_work, rpc_async_schedule);
 		status = queue_work(task->tk_workqueue, &task->u.tk_work);
 		if (status < 0) {
 			printk(KERN_WARNING "RPC: failed to add task to queue: error: %d!\n", status);
@@ -695,9 +695,9 @@ rpc_execute(struct rpc_task *task)
 	return __rpc_execute(task);
 }
 
-static void rpc_async_schedule(void *arg)
+static void rpc_async_schedule(struct work_struct *work)
 {
-	__rpc_execute((struct rpc_task *)arg);
+	__rpc_execute(container_of(work, struct rpc_task, u.tk_work));
 }
 
 /**
diff --git a/net/sunrpc/xprt.c b/net/sunrpc/xprt.c
index 80857470dc1..4f9a5d9791f 100644
--- a/net/sunrpc/xprt.c
+++ b/net/sunrpc/xprt.c
@@ -479,9 +479,10 @@ int xprt_adjust_timeout(struct rpc_rqst *req)
 	return status;
 }
 
-static void xprt_autoclose(void *args)
+static void xprt_autoclose(struct work_struct *work)
 {
-	struct rpc_xprt *xprt = (struct rpc_xprt *)args;
+	struct rpc_xprt *xprt =
+		container_of(work, struct rpc_xprt, task_cleanup);
 
 	xprt_disconnect(xprt);
 	xprt->ops->close(xprt);
@@ -932,7 +933,7 @@ struct rpc_xprt *xprt_create_transport(int proto, struct sockaddr *ap, size_t si
 
 	INIT_LIST_HEAD(&xprt->free);
 	INIT_LIST_HEAD(&xprt->recv);
-	INIT_WORK(&xprt->task_cleanup, xprt_autoclose, xprt);
+	INIT_WORK(&xprt->task_cleanup, xprt_autoclose);
 	init_timer(&xprt->timer);
 	xprt->timer.function = xprt_init_autodisconnect;
 	xprt->timer.data = (unsigned long) xprt;
diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c
index 3c7532cd009..cfe3c15be94 100644
--- a/net/sunrpc/xprtsock.c
+++ b/net/sunrpc/xprtsock.c
@@ -1060,13 +1060,14 @@ static int xs_bindresvport(struct rpc_xprt *xprt, struct socket *sock)
 
 /**
  * xs_udp_connect_worker - set up a UDP socket
- * @args: RPC transport to connect
+ * @work: RPC transport to connect
  *
  * Invoked by a work queue tasklet.
  */
-static void xs_udp_connect_worker(void *args)
+static void xs_udp_connect_worker(struct work_struct *work)
 {
-	struct rpc_xprt *xprt = (struct rpc_xprt *) args;
+	struct rpc_xprt *xprt =
+		container_of(work, struct rpc_xprt, connect_worker.work);
 	struct socket *sock = xprt->sock;
 	int err, status = -EIO;
 
@@ -1144,13 +1145,14 @@ static void xs_tcp_reuse_connection(struct rpc_xprt *xprt)
 
 /**
  * xs_tcp_connect_worker - connect a TCP socket to a remote endpoint
- * @args: RPC transport to connect
+ * @work: RPC transport to connect
  *
  * Invoked by a work queue tasklet.
  */
-static void xs_tcp_connect_worker(void *args)
+static void xs_tcp_connect_worker(struct work_struct *work)
 {
-	struct rpc_xprt *xprt = (struct rpc_xprt *)args;
+	struct rpc_xprt *xprt =
+		container_of(work, struct rpc_xprt, connect_worker.work);
 	struct socket *sock = xprt->sock;
 	int err, status = -EIO;
 
@@ -1375,7 +1377,7 @@ int xs_setup_udp(struct rpc_xprt *xprt, struct rpc_timeout *to)
 	/* XXX: header size can vary due to auth type, IPv6, etc. */
 	xprt->max_payload = (1U << 16) - (MAX_HEADER << 3);
 
-	INIT_DELAYED_WORK(&xprt->connect_worker, xs_udp_connect_worker, xprt);
+	INIT_DELAYED_WORK(&xprt->connect_worker, xs_udp_connect_worker);
 	xprt->bind_timeout = XS_BIND_TO;
 	xprt->connect_timeout = XS_UDP_CONN_TO;
 	xprt->reestablish_timeout = XS_UDP_REEST_TO;
@@ -1420,7 +1422,7 @@ int xs_setup_tcp(struct rpc_xprt *xprt, struct rpc_timeout *to)
 	xprt->tsh_size = sizeof(rpc_fraghdr) / sizeof(u32);
 	xprt->max_payload = RPC_MAX_FRAGMENT_SIZE;
 
-	INIT_DELAYED_WORK(&xprt->connect_worker, xs_tcp_connect_worker, xprt);
+	INIT_DELAYED_WORK(&xprt->connect_worker, xs_tcp_connect_worker);
 	xprt->bind_timeout = XS_BIND_TO;
 	xprt->connect_timeout = XS_TCP_CONN_TO;
 	xprt->reestablish_timeout = XS_TCP_INIT_REEST_TO;