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>

1 files changed, 10 insertions, 8 deletions

diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c
index 3c7532cd009e..cfe3c15be948 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;