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>

include/linux/ceph/messenger.h

@@ -86,7 +86,7 @@ struct ceph_msg {
 #ifdef CONFIG_BLOCK
 	struct bio  *bio;		/* instead of pages/pagelist */
 	struct bio  *bio_iter;		/* bio iterator */
-	int bio_seg;			/* current bio segment */
+	unsigned int bio_seg;		/* current bio segment */
 #endif /* CONFIG_BLOCK */
 	struct ceph_pagelist *trail;	/* the trailing part of the data */
 	bool front_is_vmalloc;

net/ceph/messenger.c

@@ -697,18 +697,19 @@ static void con_out_kvec_add(struct ceph_connection *con,
 }
 
 #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 @@ static int read_partial_message_pages(struct ceph_connection *con,
 
 #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);