block/xen-blkback: s/nr_pages/nr_segs/

Make the code less confusing to read now that Linux may not have the
same page size as Xen.

Signed-off-by: Julien Grall <[e-mail]>
Acked-by: Roger Pau Monné <[e-mail]>
Cc: Konrad Rzeszutek Wilk <[e-mail]>
Signed-off-by: David Vrabel <[e-mail]>

drivers/block/xen-blkback/blkback.c

···
 	struct grant_page **pages = req->segments;
 	unsigned int invcount;
 
-	invcount = xen_blkbk_unmap_prepare(blkif, pages, req->nr_pages,
+	invcount = xen_blkbk_unmap_prepare(blkif, pages, req->nr_segs,
 					   req->unmap, req->unmap_pages);
 
 	work->data = req;
···
 	int rc;
 
 	rc = xen_blkbk_map(pending_req->blkif, pending_req->segments,
-			   pending_req->nr_pages,
+			   pending_req->nr_segs,
 	                   (pending_req->operation != BLKIF_OP_READ));
 
 	return rc;
···
 	int indirect_grefs, rc, n, nseg, i;
 	struct blkif_request_segment *segments = NULL;
 
-	nseg = pending_req->nr_pages;
+	nseg = pending_req->nr_segs;
 	indirect_grefs = INDIRECT_PAGES(nseg);
 	BUG_ON(indirect_grefs > BLKIF_MAX_INDIRECT_PAGES_PER_REQUEST);
 
···
 	pending_req->id        = req->u.rw.id;
 	pending_req->operation = req_operation;
 	pending_req->status    = BLKIF_RSP_OKAY;
-	pending_req->nr_pages  = nseg;
+	pending_req->nr_segs   = nseg;
 
 	if (req->operation != BLKIF_OP_INDIRECT) {
 		preq.dev               = req->u.rw.handle;
···
 
  fail_flush:
 	xen_blkbk_unmap(blkif, pending_req->segments,
-	                pending_req->nr_pages);
+	                pending_req->nr_segs);
  fail_response:
 	/* Haven't submitted any bio's yet. */
 	make_response(blkif, req->u.rw.id, req_operation, BLKIF_RSP_ERROR);

drivers/block/xen-blkback/common.h

···
 struct pending_req {
 	struct xen_blkif	*blkif;
 	u64			id;
-	int			nr_pages;
+	int			nr_segs;
 	atomic_t		pendcnt;
 	unsigned short		operation;
 	int			status;