netfs: Fix i_dio_count leak on DIO read past i_size

If netfs_begin_read gets a NETFS_DIO_READ request that begins
past i_size, it won't perform any i/o and just return 0.  This
will leak an increment to i_dio_count that is done at the top
of the function.

This can cause subsequent buffered read requests to block
indefinitely, waiting for a non existing dio operation to complete.

Add a inode_dio_end() for the NETFS_DIO_READ case, before returning.
Signed-off-by: Marc Dionne <marc.dionne@auristor.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Link: https://lore.kernel.org/r/20240129094924.1221977-2-dhowells@redhat.comReviewed-by: Jeff Layton <jlayton@kernel.org>
cc: Jeff Layton <jlayton@kernel.org>
cc:  <linux-afs@lists.infradead.org>
cc:  <netfs@lists.linux.dev>
cc:  <linux-fsdevel@vger.kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>

fs/netfs/io.c

@@ -748,6 +748,8 @@ int netfs_begin_read(struct netfs_io_request *rreq, bool sync)
 
 	if (!rreq->submitted) {
 		netfs_put_request(rreq, false, netfs_rreq_trace_put_no_submit);
+		if (rreq->origin == NETFS_DIO_READ)
+			inode_dio_end(rreq->inode);
 		ret = 0;
 		goto out;
 	}