How to reread disk size?

[Asdo <asdo@shiftmail.org>]

Hi all,
I have a system with hot swappable bays but one of the involved 
controllers apparently does not support hot swap:
(I have unfortunately an old kernel: 2.6.24)

00:1f.2 IDE interface: Intel Corporation 631xESB/632xESB/3100 Chipset 
SATA IDE Controller (rev 09) (prog-if 8f [Master SecP SecO PriP PriO])
        Flags: bus master, 66MHz, medium devsel, latency 0, IRQ 19
        I/O ports at 18c8 [size=8]
        I/O ports at 18ac [size=4]
        I/O ports at 18c0 [size=8]
        I/O ports at 18a8 [size=4]
        I/O ports at 18b0 [size=16]
        Memory at da804400 (32-bit, non-prefetchable) [size=1K]
        Capabilities: [70] Power Management version 2


I have swapped the disk with a larger one (750GB -> 1TB) but it blockdev 
--getsize64 still sees the old size. It has not realized I have swapped 
disk.

In the past I was doing:

  blockdev --rereadpt /dev/sdX

and it usually worked on other controllers to reread the size visible 
from "blockdev --getsize" or "blockdev --getsize64". One time I think it 
even worked on exactly *that* controller... but it's not working now, 
it's strange.

Is there a technique, or I am out of luck?
The machine should not be rebooted
I would even enter the size manually if possible: I know how many LBA 
blocks are in that disk.

Thank you