libceph: make ceph_msg->bio_seg be unsigned

The bio_seg field is used by the ceph messenger in iterating through
a bio.  It should never have a negative value, so make it an
unsigned.  (I contemplated making it unsigned short to match the
struct bio definition, but it offered no benefit.)

Change variables used to hold bio_seg values to all be unsigned as
well.  Change two variable names in init_bio_iter() to match the
convention used everywhere else.

Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Josh Durgin <josh.durgin@inktank.com>
diff --git a/net/ceph/messenger.c b/net/ceph/messenger.c
index 2c0669f..c06f940 100644
--- a/net/ceph/messenger.c
+++ b/net/ceph/messenger.c
@@ -697,18 +697,19 @@
 }
 
 #ifdef CONFIG_BLOCK
-static void init_bio_iter(struct bio *bio, struct bio **iter, int *seg)
+static void init_bio_iter(struct bio *bio, struct bio **bio_iter,
+			unsigned int *bio_seg)
 {
 	if (!bio) {
-		*iter = NULL;
-		*seg = 0;
+		*bio_iter = NULL;
+		*bio_seg = 0;
 		return;
 	}
-	*iter = bio;
-	*seg = bio->bi_idx;
+	*bio_iter = bio;
+	*bio_seg = (unsigned int) bio->bi_idx;
 }
 
-static void iter_bio_next(struct bio **bio_iter, int *seg)
+static void iter_bio_next(struct bio **bio_iter, unsigned int *seg)
 {
 	if (*bio_iter == NULL)
 		return;
@@ -1818,7 +1819,8 @@
 
 #ifdef CONFIG_BLOCK
 static int read_partial_message_bio(struct ceph_connection *con,
-				    struct bio **bio_iter, int *bio_seg,
+				    struct bio **bio_iter,
+				    unsigned int *bio_seg,
 				    unsigned int data_len, bool do_datacrc)
 {
 	struct bio_vec *bv = bio_iovec_idx(*bio_iter, *bio_seg);