[PATCH] sparse: read_descriptor_t annotation

We have a fun situation with read_descriptor_t - all its instances end
up passed to some actor; these actors use desc->buf as their private
data; there are 5 of them and they expect resp:

        struct lo_read_data *
        struct svc_rqst *
        struct file *
        struct rpc_xprt *
        char __user *

IOW, there is no type safety whatsoever; the field is essentially untyped,
we rely on the fact that actor is chosen by the same code that sets ->buf
and expect it to put something of the right type there.

Right now desc->buf is declared as char __user *.  Moreover, the last
argument of ->sendfile() (what should be stored in ->buf) is void __user *,
even though it's actually _never_ a userland pointer.

If nothing else, ->sendfile() should take void * instead; that alone removes
a bunch of bogus warnings.  I went further and replaced desc->buf with a
union of void * and char __user *.

1 files changed, 2 insertions, 2 deletions

diff --git a/net/sunrpc/xprt.c b/net/sunrpc/xprt.c
index cf4cf02bc35ea2..5fbbe608b14f5c 100644
--- a/net/sunrpc/xprt.c
+++ b/net/sunrpc/xprt.c
@@ -973,7 +973,7 @@ static int
 tcp_data_recv(read_descriptor_t *rd_desc, struct sk_buff *skb,
 		unsigned int offset, size_t len)
 {
-	struct rpc_xprt *xprt = (struct rpc_xprt *)rd_desc->buf;
+	struct rpc_xprt *xprt = rd_desc->arg.data;
 	skb_reader_t desc = {
 		.skb	= skb,
 		.offset	= offset,
@@ -1021,7 +1021,7 @@ static void tcp_data_ready(struct sock *sk, int bytes)
 		goto out;
 
 	/* We use rd_desc to pass struct xprt to tcp_data_recv */
-	rd_desc.buf = (char *)xprt;
+	rd_desc.arg.data = xprt;
 	rd_desc.count = 65536;
 	tcp_read_sock(sk, &rd_desc, tcp_data_recv);
 out: