tcm_vhost: Introduce iov_num_pages

Add a helper to calculate the number of pages needed for a iov entry.

(nab: Drop unnecessary inline)
Signed-off-by: NAsias He <asias@redhat.com>
Signed-off-by: NNicholas Bellinger <nab@linux-iscsi.org>

drivers/vhost/tcm_vhost.c

@@ -77,6 +77,12 @@ static struct workqueue_struct *tcm_vhost_workqueue;
 static DEFINE_MUTEX(tcm_vhost_mutex);
 static LIST_HEAD(tcm_vhost_list);
 
+static int iov_num_pages(struct iovec *iov)
+{
+	return (PAGE_ALIGN((unsigned long)iov->iov_base + iov->iov_len) -
+	       ((unsigned long)iov->iov_base & PAGE_MASK)) >> PAGE_SHIFT;
+}
+
 static int tcm_vhost_check_true(struct se_portal_group *se_tpg)
 {
 	return 1;