block-migration: fix pending() and iterate() return values

block-migration: fix pending() and iterate() return values

The return value of .save_live_pending() is the number of bytes
remaining.  This is just an estimate because we do not know how many
blocks will be dirtied by the running guest.

Currently our return value for .save_live_pending() is wrong because it
includes dirty blocks but not in-flight bdrv_aio_readv() requests or
unsent blocks.  Crucially, it also doesn't include the bulk phase where
the entire device is transferred - therefore we risk completing block
migration before all blocks have been transferred!

The return value of .save_live_iterate() is the number of bytes
transferred this iteration.  Currently we return whether there are bytes
remaining, which is incorrect.

Move the bytes remaining calculation into .save_live_pending() and
really return the number of bytes transferred this iteration in
.save_live_iterate().

Also fix the %ld format specifier which was used for a uint64_t
argument.  PRIu64 must be use to avoid warnings on 32-bit hosts.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Message-id: 1360661835-28663-3-git-send-email-stefanha@redhat.com
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>