fscache: Pass object size in rather than calling back for it

Pass the object size in to fscache_acquire_cookie() and
fscache_write_page() rather than the netfs providing a callback by which it
can be received.  This makes it easier to update the size of the object
when a new page is written that extends the object.

The current object size is also passed by fscache to the check_aux
function, obviating the need to store it in the aux data.

Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Anna Schumaker <anna.schumaker@netapp.com>
Tested-by: Steve Dickson <steved@redhat.com>

fs/afs/cell.c

@@ -524,7 +524,7 @@ static int afs_activate_cell(struct afs_net *net, struct afs_cell *cell)
 					     &afs_cell_cache_index_def,
 					     cell->name, strlen(cell->name),
 					     NULL, 0,
-					     cell, true);
+					     cell, 0, true);
 #endif
 	ret = afs_proc_cell_setup(net, cell);
 	if (ret < 0)