ceph: use ceph_sb_to_client instead of ceph_client

ceph_sb_to_client and ceph_client are really identical, we need to dump
one; while function ceph_client is confusing with "struct ceph_client",
ceph_sb_to_client's definition is more clear; so we'd better switch all
call to ceph_sb_to_client.

  -static inline struct ceph_client *ceph_client(struct super_block *sb)
  -{
  -	return sb->s_fs_info;
  -}

Signed-off-by: Cheng Renquan <crquan@gmail.com>
Signed-off-by: Sage Weil <sage@newdream.net>
diff --git a/fs/ceph/addr.c b/fs/ceph/addr.c
index caf76c7..d9c60b8 100644
--- a/fs/ceph/addr.c
+++ b/fs/ceph/addr.c
@@ -563,7 +563,7 @@
 	ceph_release_pages(req->r_pages, req->r_num_pages);
 	if (req->r_pages_from_pool)
 		mempool_free(req->r_pages,
-			     ceph_client(inode->i_sb)->wb_pagevec_pool);
+			     ceph_sb_to_client(inode->i_sb)->wb_pagevec_pool);
 	else
 		kfree(req->r_pages);
 	ceph_osdc_put_request(req);