[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, 1 insertions, 1 deletions

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index f1250943c167..946742912a9f 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -293,7 +293,7 @@ lo_read_actor(read_descriptor_t *desc, struct page *page,
 	      unsigned long offset, unsigned long size)
 {
 	unsigned long count = desc->count;
-	struct lo_read_data *p = (struct lo_read_data*)desc->buf;
+	struct lo_read_data *p = desc->arg.data;
 	struct loop_device *lo = p->lo;
 	sector_t IV;