[Drbd-dev] DRBD-8: recent regression causing corruption andcrashes

[Graham, Simon]

After a lot of looking at the disassembly of the send-ack routines, I
think I've found it -- the new routines Philipp added do this:

static int _drbd_send_ack(drbd_dev *mdev, Drbd_Packet_Cmd cmd, 
			  sector_t sector,
			  unsigned int blksize,
			  u64 block_id)
{...}

int drbd_send_ack(drbd_dev *mdev, Drbd_Packet_Cmd cmd, struct
Tl_epoch_entry *e)
{
	return _drbd_send_ack(mdev,cmd,
			      cpu_to_be64(drbd_ee_get_sector(e)),
			      cpu_to_be32(drbd_ee_get_size(e)),
			      e->block_id);
}

Now, if you build on a system that does NOT have CONFIG_LBD defined,
then the definition of sector_t is 'unsigned long' - i.e. 32-bits, to
the code above byte swaps the sector number as a u64, then truncates it
to 32-bits leaving JUST the byte-swapped upper portion, i.e. zero
_ALWAYS_.

I just checked my config and CONFIG_LBD is off -- I'm guessing it's
probably on for the tests you run?

I also think the fix is simply a matter of changing the definition of
_drbd_send_ack to be 'u64 sector' - I'm going to try this right now!

Simon